WO2019008382A1 - Formulation and layer - Google Patents

Formulation and layer Download PDF

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Publication number
WO2019008382A1
WO2019008382A1 PCT/GB2018/051919 GB2018051919W WO2019008382A1 WO 2019008382 A1 WO2019008382 A1 WO 2019008382A1 GB 2018051919 W GB2018051919 W GB 2018051919W WO 2019008382 A1 WO2019008382 A1 WO 2019008382A1
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Prior art keywords
layer
organic
solvent
formulation
passivation
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PCT/GB2018/051919
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French (fr)
Inventor
Simon Dominic Ogier
Michael James SIMMS
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Wuhan Xinqu Chuangrou Optoelectronics Technology Co., Ltd.
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Publication of WO2019008382A1 publication Critical patent/WO2019008382A1/en

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K10/00—Organic devices specially adapted for rectifying, amplifying, oscillating or switching; Organic capacitors or resistors having potential barriers
    • H10K10/40—Organic transistors
    • H10K10/46—Field-effect transistors, e.g. organic thin-film transistors [OTFT]
    • H10K10/462—Insulated gate field-effect transistors [IGFETs]
    • H10K10/468—Insulated gate field-effect transistors [IGFETs] characterised by the gate dielectrics
    • H10K10/471—Insulated gate field-effect transistors [IGFETs] characterised by the gate dielectrics the gate dielectric comprising only organic materials
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004—Photosensitive materials
    • G03F7/0048—Photosensitive materials characterised by the solvents or agents facilitating spreading, e.g. tensio-active agents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
    • H01L21/0271—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34 comprising organic layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K10/00—Organic devices specially adapted for rectifying, amplifying, oscillating or switching; Organic capacitors or resistors having potential barriers
    • H10K10/40—Organic transistors
    • H10K10/46—Field-effect transistors, e.g. organic thin-film transistors [OTFT]
    • H10K10/462—Insulated gate field-effect transistors [IGFETs]
    • H10K10/464—Lateral top-gate IGFETs comprising only a single gate
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K10/00—Organic devices specially adapted for rectifying, amplifying, oscillating or switching; Organic capacitors or resistors having potential barriers
    • H10K10/80—Constructional details
    • H10K10/88—Passivation; Containers; Encapsulations

Definitions

  • the present invention relates to formulations for providing layers, such as passivation layers and/or photopatterning layers, for use in fabrication of organic electronic devices, to methods of fabrication of organic electronic devices using such formulations and to organic electronic devices including layers provided by such formulations.
  • Organic electronic (OE) devices include, for example, organic field effect transistors (OFET) for use in backplanes of display devices or logic capable circuits, and organic photovoltaic (OPV) devices.
  • a conventional top gate OFET comprises source and drain electrodes, a semiconducting layer made of an organic semiconductor (OSC) material, a gate insulator layer made of a dielectric material (also known as a dielectric or a gate dielectric) such as an organic gate insulator (OGI), a gate electrode, and typically a passivation layer on top of the OGI layer to protect the OSC and OGI layer against environmental influence and/or damage from subsequent device fabricating steps.
  • OSC organic semiconductor
  • OGI organic gate insulator
  • a conventional bottom gate OFET comprises a gate electrode, a gate insulator layer made of a dielectric material such as an organic gate insulator (OGI), source and drain electrodes, a semiconducting layer made of an organic semiconductor (OSC) material, and typically a passivation layer on top of the OSC layer to protect the OSC and OGI layers against environmental influence and/or damage from subsequent device fabricating steps.
  • the passivation layer may also serve as an interlayer dielectric so that metal tracks may be routed in the circuit on different layers of these OE devices without short circuiting, for example.
  • Solution processable passivation layers are preferred, particularly for OFETs.
  • Solution processable passivation materials SPPMs
  • solution-based deposition methods for example spin-coating or larger area printing methods including flexo, gravure and slot-die coating, during fabrication.
  • Adhesion of the passivation materials to underlying layers may be a primary conventional requirement for such solution-based passivation materials.
  • orthogonality of solvents used in the solution-based passivation materials particularly to organic layers such as the OSC layers and/or the OGI layers, is also required.
  • the orthogonality of the solvents may be understood as chemical orthogonality.
  • an orthogonal solvent is a solvent which, when used in the provision of a layer of a material dissolved and/or dispersed therein on a previously provided layer, does not adversely affect the previously provided layer.
  • orthogonal solvents may be considered as suitable (also known as compatible) solvents, in that they do not adversely affect organic layers such as the OSC layers and/or the OGI layers.
  • non-orthogonal (also known as unsuitable or incompatible) solvents may dissolve, damage, destroy or impact a long-term stability of the previously provided layer.
  • Figure 1 shows schematically a method of fabrication of an OE device, specifically a top gate OFET, using conventional solution processable passivation materials. Typically, such a method of fabrication may be achieved practically by photolithographic processing, as known to the person skilled in the art.
  • a substrate 1 10 is provided.
  • the substrate 1 10 may comprise glass, metal, a polymer or an intergrated circuit (IC), for example.
  • the substrate 1 10 may include an optional buffer layer provided on the surface of the substrate 1 10.
  • the buffer layer may also be known as a planarization layer, provided by a crosslinkable polymer that may improve surface uniformity and/or homogeneity by smoothing imperfections in the surface of the substrate and may provide a chemically inert surface upon which the OE device is fabricated.
  • source and drain electrodes 120 are provided on the surface of the substrate 1 10, for example by sputtering and photolithography (using mask 1 ).
  • the source and the drain electrodes 120 are typically a metal, for example silver or gold or alloys thereof, or a non-metal.
  • the source and the drain electrodes 120 may be treated with a thiol solution, to adjust work functions of the source and the drain electrodes 120, as known in the art. In this way, injection of charges into an overlaying OSC layer may be improved. Excess thiol solution may be washed away, with thiol binding only to the source and the drain electrodes 120.
  • an OSC layer 130 is first provided over the source and the drain electrodes 120 and the exposed surface of the substrate 1 10, for example by spin coating or printing.
  • the OSC layer 130 typically has a thickness of 30 nm.
  • An OGI layer 140 is subsequently provided over the OSC layer 130, for example by spin coating or printing.
  • the OGI layer 140 typically has a thickness of 300 nm.
  • a metal layer 150 for example silver or gold or alloys thereof, is subsequently deposited on the OGI layer 140, for example by evaporation.
  • a photoresist (not shown) is subsequently patterned (e.g. by photolithography) on the metal layer 150 and portions of the metal layer 150 exposed through the patterned photoresist are removed by wet etching.
  • the patterned metal layer 150 provides a gate, such as a thin film transistor (TFT) gate.
  • the patterned metal layer 150 also provides a hardmask (mask 2) against reactive ion etching (RIE) (also known as dry etching, for example using 0 2 and/or Ar), thereby masking the underlying OGI layer 140, the OSC layer 130 and the source and the drain electrodes 120.
  • RIE reactive ion etching
  • RIE reactive ion etching
  • the stack 100 generally describes a multilayered structure and thus may comprise more or fewer and/or different layers.
  • the stack 100 may comprise those layers at an intermediary stage of fabrication of the OE device.
  • the stack 100 may comprise all layers of the completed OE device. That is, layers included in the stack 100 may change during fabrication, by addition and/or by removal of layers. Sides 141 of the OGI layer 140 and sides 131 of the OSC layer 130 may be thus exposed, for example by the RIE, and may be adversely affected by unsuitable solvents. Further, inter-layer interfaces may also be exposed, for example between the substrate 110 and the OSC layer 130, between the OSC layer 130 and the OGI layer 140 and/or between the OGI layer 140 and the metal layer 150. Other surfaces of the OGI layer 140 and/or the OSC layer 130 may be additionally and/or alternatively exposed.
  • a conventional first passivation layer 180 is provided over the stack 100 and the exposed surface of the substrate 1 10, for example, by coating with a first formulation comprising an aqueous solution of a water-soluble polymer formulation such as polyvinyl alcohol (PVA) plus Ammonium Dichromate (ADC) and subsequently UV crosslinking the water-soluble polymer (i.e. the PVA+ADC).
  • the first passivation layer 180 typically has a thickness of 100 nm. Water is generally considered an orthogonal solvent, being at least sufficiently compatible with the OGI layer 140 and/or the OSC layer 130.
  • the first passivation layer 180 provided using crosslinked PVA may not be suitable for subsequent fabrication steps and/or may not be suitable for providing environmental, chemical and/or physical protection of the fabricated OE device.
  • a second passivation layer 190 is additionally required, as described below.
  • a positive photoresist mask 181 (mask 3) is provided over the first passivation layer 180.
  • a first hole 185 (also known as a via) is formed through the first passivation layer 180 to the patterned metal layer 150, by RIE through the positive photoresist mask 181 , thereby exposing at least a part of the surface of the metal layer 150.
  • residual photoresist mask 181 is removed.
  • the second passivation layer 190 is provided over the first passivation layer 180 and exposed potions of the stack, such as the patterned metal layer 150 exposed through the hole formed through the first passivation layer 180.
  • the second passivation layer 190 is provided, for example, by coating with a second formulation, such as a solution of another crosslinkable polymer, for example SU-8 available from MicroChem Corp., Westborough, MA (USA), and crosslinking the polymer.
  • SU-8 comprises a bisphenol A novolac epoxy dissolved in an organic solvent such as cyclopentanone, gamma-butyrolactone (GBL) or propylene glycol monoethyl ether acetate (PGMEA).
  • the SU-8 may include also up to 10 wt.% of a photoacid generator, for example a mixed triarylsulfonium hexafluoroantimonate salt.
  • the second passivation layer 190 typically has a thickness of 300 nm and may provide the main passivation layer for the OE device.
  • the second passivation layer 190 provides the robustness required for providing environmental, chemical and/or physical protection of the fabricated OE device.
  • the organic solvents used in the second formulation are generally non-orthogonal solvents, being incompatible with the organic layers, such as the OGI layer 140 and/or the OSC layer 130, of the stack 100.
  • robust crosslinkable polymers such as in SU-8, may not be soluble and/or dispersible in orthogonal solvents, such as water used in the first formulation, and thus must be provided in these non-orthogonal solvents, such as cyclopentanone, GBL or PGMEA.
  • the first passivation layer 180 acts as a protection layer, protecting the organic layers, such as the OGI layer 140 and/or the OSC layer 130, of the stack 100 from the non-orthogonal solvents included in the second formulation.
  • Another positive photoresist mask (not shown) (mask 4) is provided over the second passivation layer 190 and the hole or via is formed therethrough by RIE. Residual photoresist mask is subsequently removed.
  • a metal gate interconnect 170 is provided through the second hole to the patterned metal layer 150, for example, by sputtering, masking (mask 5) and etching.
  • the OE device may be provided, having a double passivation layer comprising the first passivation layer 180 and the second passivation layer 190.
  • this double passivation layer comprising the first passivation layer 180 and the second passivation layer 190 increase OE device fabrication complexity and/or cost.
  • water-soluble polymers such as PVA
  • PVA water-soluble polymers
  • water, such as absorbed moisture, in the first passivation layer 180 may be detrimental to long-term stability of OE devices.
  • five masks (mask 1 - mask 5) are required.
  • a first aspect of the invention provides a flowable formulation for depositing a passivation layer on an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer, wherein the formulation comprises a passivation material and a solvent;
  • OSC organic semiconductor
  • OTI organic gate insulator
  • the solvent comprises levoglucosenone or dihydrolevoglucosenone or a derivative thereof.
  • a second aspect of the invention provides a method of fabricating an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer, wherein the method comprises:
  • a passivation layer on at least a part of the organic layer by depositing a formulation according to the first aspect thereon and removing the solvent.
  • a third aspect of the invention provides an organic electronic (OE) device comprising an organic layer and a passivation layer directly thereon, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer and wherein the passivation layer comprises a cross-linked product of a cross-linkable composition provided by the first aspect.
  • OSC organic semiconductor
  • OTI organic gate insulator
  • a fourth aspect of the invention provides a product comprising an organic electronic (OE) device fabricated according to the second aspect and/or an OE device according to the third aspect.
  • OE organic electronic
  • a fifth aspect of the invention provides a flowable formulation comprising a photopatterning material and a solvent
  • the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof.
  • a sixth aspect of the invention provides use of a solvent comprising levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof in a method of fabricating an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer.
  • OSC organic semiconductor
  • OTI organic gate insulator
  • the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components.
  • the term “consisting essentially of or “consists essentially of” means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention.
  • the SPPMs and/or formulations should preferably be compatible with (i.e. orthogonal to) organic layers, such as OSC and/or OGI layers, and OE device architectures.
  • organic layers may be soluble in organic solvents and hence exposure of these organic layers to such solvents should be avoided.
  • inter-layer adhesion such as between overlaying OSC and/or OGI layers, is important for functioning of OE devices. Since different organic layers, such as the OSC and/or the OGI layers, typically have different surface energies, solvents that may not dissolve a particular layer may penetrate via inter-layer interfaces and thereby also degrade or destroy functioning of OE devices.
  • the SPPMs should preferably provide environmental, physical and/or chemical resistance, for example against materials and conditions applied during subsequent fabrication steps during OE device manufacture, for example photolithography.
  • photolithography incudes one or more of the following processing steps, which may involve chemical and/or physical exposure of the underlying layers: deposition of photo resist resin, typically in an organic solvent; UV exposure; development of the photo resist, typically using bases; etching of metal, typically using aggressive acids and redox reactions; and/or removal of the photo resist, typically using aggressive organic solvents.
  • the deposited passivation material should preferably withstand organic solvents and/or aqueous solutions.
  • deposition of the passivation material generally requires the passivation material to preferably be soluble and/or dispersible in an organic solvent or an aqueous solution.
  • the passivation material may be cross-linked after deposition, for example, to meet these conflicting requirements.
  • the deposited passivation layer should preferably exhibit at least one of mechanical flexibility, good scratch resistance, thermal stability, optical transparency, uniformity, pinhole free, good adhesion to other layers, good barrier properties with respect to water and/or oxygen, non-hygroscopic and good dielectric breakdown strength.
  • the first aspect of the invention provides a flowable formulation for depositing a passivation layer on an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer, wherein the formulation comprises a passivation material and a solvent;
  • OSC organic semiconductor
  • OTI organic gate insulator
  • an aspect of the invention provides a flowable formulation comprising a passivation material and a solvent;
  • the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof.
  • the flowable formulation according to the first aspect of the invention may also be suitable for providing layers in other devices, such as microelectromechanical systems (MEMs), microfluidic devices, and/or conventional (for example, non-organic thin-film transistor (OTFT)) electronics.
  • MEMs microelectromechanical systems
  • OTFT non-organic thin-film transistor
  • a flowable formulation comprising a photopatterning material and a solvent
  • the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof.
  • OE organic electronic
  • OSC organic semiconductor
  • OGI organic gate insulator
  • a flowable formulation comprising a cross-linkable composition and a solvent
  • the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof.
  • the flowable formulation may be provided for spin coating and/or printing directly and/or following addition of further solvent.
  • flowable formulations for spin coating for example, may have dynamic or absolute viscosities in a range of from 1 to 10,000 centipoise or more, as known to the person skilled in the art.
  • a dynamic viscosity of the flowable formulation is in a range of from 1 to 10,000 centipoise, preferably 1 to 1000 centipoise, more preferably 1 to 20 centipoise.
  • a dynamic viscosity of the flowable formulation may depend, at least in part, on an amount of the solvent in the flowable formulation, such that an increased amount of the solvent may decrease the dynamic viscosity.
  • the solvent exhibits low wettability of the organic layer, such that a contact angle ⁇ is in a range from 90° to 180°.
  • a contact angle ⁇ is the angle at which a liquid-vapour interface meets a solid-liquid interface.
  • the contact angle ⁇ is determined by a result between adhesive and cohesive forces. As a tendency of a drop to spread out over a flat, solid surface increases, the contact angle ⁇ decreases.
  • the contact angle ⁇ provides an inverse measure of wettability. A contact angle less than 90° (low contact angle) usually indicates that wetting of the surface is very favourable, and the fluid will spread over a large area of the surface.
  • Contact angles greater than 90° generally means that wetting of the surface is unfavourable, so the fluid will minimize contact with the surface and form a compact liquid droplet.
  • a wettable surface may also be termed hydrophilic and a nonwettable surface hydrophobic.
  • Superhydrophobic surfaces have contact angles greater than 150°, showing almost no contact between the liquid drop and the surface.
  • a term lyophilic may be used for low contact angle conditions and lyophobic may be used when higher contact angles result.
  • terms omniphilic and omniphobic may be used for polar and apolar liquids.
  • Wettability may relate to a surface tension of the solvent.
  • a surface tension of dihydrolevoglucosenone (neat) is 33.6 mN/m (DATA SHEET: CYRENETM Circa, Australia) c.f. 47.36 ⁇ 0.56 mN/m (Table 14).
  • a surface tension of dihydrolevoglucosenone (1 wt.% aqueous solution) is 72.5 mN/m (DATA SHEET: CYRENETM Circa, Australia). Water has a surface tension of 72.8 mN/m.
  • cyclopentanone has a surface tension of 33.4mN/m
  • GBL has a surface tension of 40.4 mN/m
  • PGMEA has a surface tension of 26.9mN/m.
  • the solvent, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof has a surface tension of at least 30 mN/m, at least 35 mN/m, at least 40 mN/m, at least 45 mN/m, at least 50 mN/m, at least 55 mN/m, at least 60 mN/m, at least 65 mN/m or at least 70 mN/m.
  • the solvent, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof has a surface tension of at least 45 mN/m. More preferably, the solvent, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof has a surface tension of at least 70 mN/m.
  • the solvent, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof has a surface tension of at most 50 mN/m, at most 55 mN/m, at most 60 mN/m, at most 65 mN/m, at most 70 mN/m, at most 75 mN/m, at most 80 mN/m, at most 85 mN/m, at most 90 mN/m, at most 95 mN/m, at most 100 mN/m or at most 105 mN/m.
  • the solvent, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof has a surface tension of at most 100 mN/m. More preferably, the solvent, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof has a surface tension of at most 85 mIM/m.
  • Levoglucosenone, of Formula (I) is a bicyclic a, ⁇ -unsaturated ketone containing a protected aldehyde.
  • the highly dehydrated sugar is derived from cellulose and hence provides a bio-based solvent, which is attractive as a 'green' solvent.
  • Levoglucosenone ((1 S,5R)-6,8-dioxabicyclo[3.2.1]oct-2-en-4-one) has a molecular formula: C 6 H 6 0 3 and InChl Key HITOXZPZGPXYHY-UJURSFKZSA-N.
  • levoglucosenone and/or derivatives thereof may behave as dipolar aprotic solvents.
  • levoglucosenone and/or derivatives thereof have been investigated as replacements for solvents such as N,N- dimethylformamide, ⁇ , ⁇ -dimethylacetamide and N-methylpyrolidinone, which are widely used in organic synthesis and chemical manufacture but have undesirable toxicity and environmental profiles.
  • levoglucosenone and/or derivatives thereof may also be expected to exhibit similar properties to other types of solvents which find application in microelectronic fabrication processes, such as cyclopentanone, gamma-butyrolactone (GBL) or propylene glycol monoethyl ether acetate (PGMEA).
  • solvents such as cyclopentanone, gamma-butyrolactone (GBL) or propylene glycol monoethyl ether acetate (PGMEA).
  • GBL gamma-butyrolactone
  • PMEA propylene glycol monoethyl ether acetate
  • levoglucoseneone and/or derivatives thereof would be similar to the above solvents in terms of solvency properties, that is to say that they would be non-orthogonal to the OSC and/or OGI and/or the partly assembled and exposed 'stack' of a OTFT device. These properties would severely limit the usability of levoglucosenone and/or derivatives thereof in the fabrication of OTFTs.
  • the inventors have determined that levoglucosenone and/or derivatives thereof may also be orthogonal solvents, unlike the conventional organic solvents, such as cyclopentanone, GBL or PGMEA, as described above.
  • references herein to a derivative mean a derivative of levoglucosenone or a derivative of dihydrolevoglucosenone.
  • the derivative of levoglucosenone for example dihydrolevoglucosenone, may be derived from levoglucosenone. That is, the derivative of levoglucosenone may be synthesized from levoglucosenone, directly and/or indirectly.
  • levoglucosenone may be a starting material and/or an intermediary material in a synthesis of the derivative of levoglucosenone.
  • dihydrolevoglucosenone is a derivative of levoglucosenone.
  • Dihydrolevoglucosenone is derived from levoglucosenone by hydrogenation of levoglucosenone, for example over supported palladium catalysts.
  • dihydrolevoglucosenone is available as Cyrene (RTM) from Circa Group Pty Ltd (Australia).
  • Dihydrolevoglucosenone, of Formula (II), is a chiral dipolar aprotic solvent.
  • Dihydrolevoglucosenone ((1 S,5R)-6,8-Dioxabicyclo[3.2.1]octan-4-one) has a molecular formula: ⁇ 6 ⁇ 8 0 3 and InChl Key WHIRALQRTSITMI-UJURSFKZSA-N.
  • dihydrolevoglucosenone may behave as a dipolar aprotic solvent and thus may substitute for certain conventional organic dipolar aprotic solvents.
  • dihydrolevoglucosenone is considered to be a substitute for N-Methyl-2-pyrrolidone (NMP), being also similar in terms of hydrogen bonding capacity.
  • NMP N-Methyl-2-pyrrolidone
  • the Kamlet-Abboud-Taft parameters indicate that dihydrolevoglucosenone is aprotic with a similar ⁇ * value (corresponding to dipolarity) to those of highly dipolar aprotic solvents, but with a slightly lower ⁇ value which is an indicator of hydrogen bond accepting ability.
  • levoglucosenone, dihydrolevoglucosenone and/or a derivative may substitute for conventional organic solvents, such as cyclopentanone, GBL or PGMEA, in SU-8 for example, as described above in relation to the second passivation layer.
  • levoglucosenone, dihydrolevoglucosenone and/or a derivative thereof may also be orthogonal solvents, unlike the conventional organic solvents, such as cyclopentanone, GBL or PGMEA, as described above. That is, the inventors have determined that levoglucosenone or dihydrolevoglucosenone or a derivative thereof may be used as solvents for solutions comprising robust crosslinkable polymers dissolved and/or dispersed therein and that these solutions may be provided, for example directly, on organic layers, such as an OSC layer and/or an OGI layer and/or a stack comprising one or more of these layers.
  • organic layers such as an OSC layer and/or an OGI layer and/or a stack comprising one or more of these layers.
  • the formulation may be provided directly on the OGI layer, which may be part of the stack, for example.
  • the formulation may be preferably provided directly on a protection layer, for example a fluoropolymer protection layer, on the OSC layer.
  • a protection layer for example a fluoropolymer protection layer
  • such protection layers are provided on OSC layers for patterning, such as by dry etching as described previously.
  • the single passivation layer provided by the first formulation replaces the first passivation layer and the second passivation layer, as conventionally provided.
  • OE device fabrication complexity and/or cost may be reduced, since fewer steps and materials are required.
  • water-soluble polymers such as PVA
  • long-term stability of OE devices may be improved.
  • the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or the derivative thereof in an amount of at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97.5% or at least 99%, wherein the amount of levoglucosenone and/or dihydrolevoglucosenone and/or the derivative thereof is a percentage by weight of the total amount of solvent in the formulation.
  • the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or the derivative thereof in an amount of at most 25%, at most 30%, at most 35%, at most 40%, at most 45%, at most 50%, at most 55%, at most 60%, at most 65%, at most 70%, at most 75%, at most 80%, at most 85%, at most 90%, at most 95%, at most 97.5%, at most 99% or at most 100%, wherein the amount of levoglucosenone and/or dihydrolevoglucosenone and/or the derivative thereof is a percentage by weight of the total amount of solvent in the formulation.
  • the solvent comprises a mixture of levoglucosenone and/or dihydrolevoglucosenone and/or one or more derivatives thereof.
  • the solvent comprises a cosolvent, for example organic and/or aqueous solvents.
  • Example cosolvents may include cyclopentanone, GBL and PG EA, propylene carbonate, diethylene glycol, isopropyl alcohol (IPA), 2-propanol and/or ethanol.
  • the solvent comprises the cosolvent in an amount of at most 50%, at most 45%, at most 40%, at most 35%, at most 30%, at most 25%, at most 20%, at most 15%, at most 10%, at most 5%, at most 2.5% or at most 1 %, wherein the amount of the cosolvent is a percentage by weight of the total amount of solvent in the formulation.
  • the solvent comprises the cosolvent in an amount of at least 50%, at least 45%, at least 40%, at least 35%, at least 30%, at least 25%, at least 20%, at least 15%, at least 10%, at least 5%, at least 2.5% or at least 1 %, wherein the amount of the cosolvent is a percentage by weight of the total amount of solvent in the formulation.
  • the solvent comprises a plurality of cosolvents.
  • the solvent comprises the plurality of cosolvents in an amount of at most 50%, at most 45%, at most 40%, at most 35%, at most 30%, at most 25%, at most 20%, at most 15%, at most 10%, at most 5%, at most 2.5% or at most 1 %, wherein the amount of the plurality of cosolvents is a percentage by weight of the total amount of solvent in the formulation.
  • the solvent comprises the plurality of cosolvents in an amount of at least 50%, at least 45%, at least 40%, at least 35%, at least 30%, at least 25%, at least 20%, at least 15%, at least 10%, at least 5%, at least 2.5% or at least 1 %, wherein the amount of the plurality of cosolvents is a percentage by weight of the total amount of solvent in the formulation.
  • the formulation comprises the solvent in an amount of at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97.5% or at least 99%, wherein the amount of solvent is a percentage by weight of the formulation.
  • the formulation comprises the solvent in an amount of at most 25%, at most 30%, at most 35%, at most 40%, at most 45%, at most 50%, at most 55%, at most 60%, at most 65%, at most 70%, at most 75%, at most 80%, at most 85%, at most 90%, at most 95%, at most 97.5% or at most 99%, wherein the amount of solvent is a percentage by weight of the formulation.
  • the formulation comprises the passivation material in an amount of at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97.5% or at least 99%, wherein the amount of the passivation material is a percentage by weight of the formulation.
  • the formulation comprises the passivation material in an amount of at most 80%, at most 75%, at most 70%, at most 65%, at most 60%, at most 55%, at most 50%, at most 45%, at most 40%, at most 35%, at most 30%, at most 25%, at most 20%, at most 15%, at most 10%, at most 5%, at most 2.5% or at most 1 %, wherein the amount of the passivation material is a percentage by weight of the formulation.
  • Table S1 (presented as Tables S1a - S1 p for convenience) details structures and certain properties of levoglucosenone, dihydrolevoglucosenone and derivatives thereof, as reproduced from Table S1 of A. Alves Costa Pacheco, J.
  • levoglucosenone, dihydrolevoglucosenone and derivatives thereof are identified by a unique number (#) and provided with codes based on their respective documentary source references.
  • the codes are generally in the form ⁇ -1 ', in which the characters before the dash indicate the respective documentary source references (see Table S2) and the characters after the dash are the compound numbering used in the respective documentary source references reference. For this reason, abbreviations, letters, numbers and Roman numerals are possible. A common format has not been used to help the finding of compounds in their respective references should the reader wish to do so. Where the compound code is followed by (m), this is an original modification to the referenced structure.
  • (m2) signifies a second structural modification
  • (m3) a third, and so on.
  • Table S2 details the respective documentary source references (citations) for levoglucosenone, dihydrolevoglucosenone and derivatives thereof as detailed in Table S1 , as reproduced from Table S2 of Pacheco et at. (2016). Synthesis and/or sources of levoglucosenone, dihydrolevoglucosenone and derivatives thereof are provided by the respective documentary source references.
  • Table S1 a Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
  • Table S1 b Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
  • Table S1 c Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
  • Table S1 d Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
  • Table S1 i. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
  • Table S1j Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
  • Hansen solubility parameters may be used to characterise polarity of solvents in terms of their dispersion forces 6 d , the degree of polarity that arises from any dipoles ⁇ ⁇ , and their capacity for hydrogen bonding 5 h .
  • the solvents may be thus located in Hansen space, a three-dimensional (3D) representation of 5 d , ⁇ ⁇ and 5 h . The closer two solvents are in the Hansen space, the more likely they are to exhibit the same solubilising properties.
  • the Hansen dispersion forces 5 d expressed by solvents may be similar, and so for a simpler representation of the Hansen solubility parameters, ⁇ ⁇ may be plotted against 5 h to represent different types of solvents in a two-dimensional (2D) graph.
  • the derivative has Hansen solubility parameters that are within 3 MPa 1 ⁇ 2 of those of levoglucosenone. In one example, the derivative has Hansen solubility parameters that are within 2.4 MPa 1 ⁇ 2 of those of levoglucosenone. In one example, the derivative has Hansen solubility parameters that are within 1.2 MPa 1 ⁇ 2 of those of levoglucosenone.
  • the derivative has Hansen solubility parameters that are within 3 MPa 1 ⁇ 2 of those of NMP. In one example, the derivative has Hansen solubility parameters that are within 2.4 MPa 1 ⁇ 2 of those of NMP. In one example, the derivative has Hansen solubility parameters that are within 1.2 Pa 1 ⁇ 2 of those of NMP.
  • the derivative has Hansen solubility parameters that are within 3 MPa 1 ⁇ 2 of those of cyclopentanone, GBL and/or PGMEA. In one example, the derivative has Hansen solubility parameters that are within 2.4 MPa 1 ⁇ 2 of those of cyclopentanone, GBL and/or PGMEA. In one example, the derivative has Hansen solubility parameters that are within 1.2 MPa 1 ⁇ 2 of those of cyclopentanone, GBL and/or PGMEA.
  • the derivative has Hansen solubility parameters that are within 3 MPa 1 ⁇ 2 of those of levoglucosenone, NMP, cyclopentanone, GBL and/or PGMEA. In one example, the derivative has Hansen solubility parameters that are within 2.4 MPa 1 ⁇ 2 of those of levoglucosenone, NMP, cyclopentanone, GBL and/or PGMEA. In one example, the derivative has Hansen solubility parameters that are within 1.2 MPa 1 ⁇ 2 of those of levoglucosenone, NMP, cyclopentanone, GBL and/or PGMEA.
  • Table S1 details Hansen solubility parameters of levoglucosenone, dihydrolevoglucosenone and derivatives thereof, determined as described in Pacheco et al. (2016).
  • Table 3 details physical properties and Hansen solubility parameters of various solvents, including levoglucosenone, dihydrolevoglucosenone and conventional solvents cyclopentanone, GBL and PGMEA, as described above.
  • Table 3 Physical properties Hansen solubility parameters of various solvents, including levoglucosenone, dihydrolevoglucosenone and conventional solvents cyclopentanone, GBL and PGMEA, as described above, as reproduced in part from James Sherwood, Mario De bruyn, Andri Constantinou, Laurianne Moity, C. Rob McElroy, Thomas J. Farmer, Tony Duncan, Warwick Raverty, Andrew J. Hunt and James H.
  • Hansen solubility parameters may suggest that levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof may substitute for conventional organic solvents, such as cyclopentanone, GBL or PGMEA, in SU-8 for example, as described above, the Hansen solubility parameters provide no indication that these may also be orthogonal solvents.
  • levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof may also be orthogonal solvents, unlike the conventional organic solvents, such as cyclopentanone, GBL or PGMEA, as described above. That is, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof may both substitute for conventional organic solvents, such as cyclopentanone, GBL or PGMEA, in SU-8 for example, and may be orthogonal solvents, unlike the conventional organic solvents, such as cyclopentanone, GBL or PGMEA.
  • the derivate is S5, S6 or S7, as detailed in Table S1 .
  • the hydroxyl precursors of these derivatives may be produced from levoglucosenone and/or dihydrolevoglucosenone using biocatalytic Baeyer Villiger oxidation, as described in A. L. Flourat, A. A. M. Peru, A. R. S. Teixeira, F. Brunissen and F.
  • Figure 2 schematically depicts a 2D Hansen solubility parameter map, representing levoglucosenone, dihydrolevoglucosenone and derivatives thereof, as detailed in Table 1 , reproduced from Pacheco er al. (2016).
  • conventional solvents cyclopentanone, GBL and PGMEA, as described above, are also represented.
  • Figure 2 also schematically depicts levoglucosenone derivatives having Hansen solubility parameters that are within 3 MPa 1 ⁇ 2 of those of levoglucosenone.
  • the passivation material comprises a cross-linkable composition.
  • the passivation material may be soluble and/or dispersible in the solvent for deposition and by subsequent cross-linking after deposition, the passivation material may be resistant to organic solvents and/or aqueous solutions.
  • the passivation material may meet at least some of the conflicting requirements, as described above.
  • the passivation material comprises the cross-linkable composition in an amount of at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97.5% or at least 99%, wherein the amount of cross-linkable composition is a percentage by weight of the passivation material.
  • the passivation material comprises the cross-linkable composition in an amount of at most 50%, at most 55%, at most 60%, at most 65%, at most 70%, at most 75%, at most 80%, at most 85%, at most 90%, at most 95%, at most 97.5%, at most 99% or at most 99.5%, wherein the amount of cross-linkable composition is a percentage by weight of the passivation material.
  • the cross-linkable composition comprises monomeric, oligomeric and/or polymeric precursors.
  • cross-linkable compositions comprising monomeric, oligomeric and/or polymeric precursors include monomeric, oligomeric and/or polymeric precursors comprising, for example, cross-linkable epoxy groups, siloxane - organic hybrid frameworks comprising cross-linkable epoxy groups and/or cross-linkable acrylate or (alkyl)acrylate repeat units.
  • cross-linking initiation examples include, for example, initiation thermally, photochemically, via a free radical reaction, via a thiol - ene or a thiol (alkyl)acrylate reaction, and/or via a thermal azide alkyne cycloaddition reaction.
  • the monomeric, oligomeric and/or polymeric precursors comprise epoxy groups, which may be cross-linked.
  • a passivation layer may be formed by thermal or photochemical crossiinking of monomeric, oligomeric or polymeric precursors comprising epoxy groups.
  • the passivation formulation may be coated onto a surface and then subjected to thermal or photochemical crosslinking conditions.
  • An example of a suitable oligomeric precursor comprising epoxy groups is the commercial product EPONTM SU-8 resin (also known as EPIKOTETM 157) available from Hexion.
  • EPONTM Resin SU-8 is a polymeric solid epoxy novolac resin possessing an average epoxide group functionality around eight.
  • Suitable monomeric, oligomeric or polymeric precursors may also comprise siloxane - organic hybrid frameworks comprising epoxy groups.
  • Table 4 details examples of commercially available epoxy siloxane monomeric and oligomeric precursors including products PC-1000, PC-1035, PC-2000, PC-2004, PC-201 1 , PC-2021 and PC-2026 available from Polyset Inc (Mechanicville, NY, USA). Other epoxy siloxane monomeric and oligomeric precursors are known.
  • the formulation comprises at least one of a cross-linking agent, a photoacid generator, a hardening agent, an antioxidant agent, a surfactant, and a filler.
  • the cross-linkable composition for example comprising epoxy type monomers, oligomers or polymers, may also comprise crosslinking reagents and / or catalysts.
  • a chemical reaction used provide a crosslinked, insoluble layer may be thermally or photochemically driven.
  • ACS Applied Materials Interfaces 2009, 1 , 7, 1585 describes an example of a thermally driven crosslinking reaction for a thin film precursor comprising a polymer substituted with epoxy groups.
  • methyl tetrahydrophthalic anhydride (MeTHPA) was used as a thermal curing agent and N,N- dimethylbenzylamine (BDMA) as a catalyst to promote thermal curing.
  • MeTHPA methyl tetrahydrophthalic anhydride
  • BDMA N,N- dimethylbenzylamine
  • the passivation formulation may comprise a photoacid generator (PAG).
  • PAGs are reagents which generate active acid catalysts on exposure to visible or ultraviolet radiation, typically ultraviolet radiation.
  • Suitable PAGs include materials in the Irgacure® series, commercially available from BASF (Germany).
  • PAG reagents may be ionic or non ionic in nature, and within different PAGs the chemical structures may be designed to operate at different UV wavelengths.
  • PAGs are commercially available for operation at I line (365 nm) and g / h line (405 nm, 436 nm) UV wavelengths, which are widely used within microelectronic fabrication processes.
  • the cross-linkable composition for example comprising epoxy type monomers, oligomers or polymers as described above, may also comprise a hardener (also known as a hardening reagent or agent) which may be used to adjust the curing time and / or the mechanical properties of the resulting crosslinked passivation layer.
  • suitable hardeners include the ARON series of oxetane hardeners available from Toagosei (Japan).
  • the cross-linkable composition for example comprising epoxy type monomers, oligomers or polymers as described above, may also comprise an antioxidant.
  • the antioxidant may be used to suppress discolouration (yellowing) in the crosslinkable or crosslinked film, for example due to side reactions with the PAG or its chemical byproducts. Examples of suitable antioxidants are described in US 2013 / 225711 A1.
  • the monomeric, oligomeric and/or polymeric precursors comprise (alkyl)acrylate repeat units, for example acrylate or methacrylate repeat units.
  • Crosslinkable monomers, oligomers or polymers comprising acrylate or methacrylate repeat units, herein described collectively as (alkyl)acrylate may be highly useful for the formation of crosslinked passivation layers.
  • (alkyl)acrylate thin film coating precursors are commercially available, for example under the SARTOMER brand produced by Arkema (France). It is known in the art that (alkyl)acrylate precursors may be selected and formulated in different proportions to provide different properties in crosslinked thin film coatings.
  • the (alkyl)acrylate precursors used to produce crosslinked thin film coatings may be monofunctional, difunctional or multifunctional and may be optionally be substituted with additional non (alkyl)acrylate reactive functional groups, allowing further crosslinking by alternative chemical methods other than those used to polymerise the (alkyl)acrylate groups.
  • additional non (alkyl)acrylate reactive functional groups are epoxy groups, or cinnamylidene groups are described in WO 2013 / 1 19717 A1.
  • crosslinkable (alkyl)acrylate precursors suitable for use in the cross-linkable composition may themselves be oligomeric or polymeric in nature.
  • An example of such a material is SIRIUS-501 , a dendrimeric acrylate produced by Osaka Organic Chemical Industry Ltd (Japan).
  • (Alkyl)acrylate precursors suitable for use in thermally or photochemically crosslinkable films, such as passivation layers, may optionally be substituted with partially or fully fluorinated side chains.
  • Thin films comprising polymers prepared from these precursors, and therefore bearing such side chain substitutents, may have usefully altered properties, such as chemical resistance, hydrophobicity or surface energy.
  • Table 5 details a range of fluorinated (alkyl)acrylate precursors commercially available from Sigma Aldrich, a subsidiary of Merck KGaA (Germany). Other fluorinated (alkyl)acrylate precursors are known.
  • Suitable monomeric, oligomeric or polymeric precursors may also comprise siloxane - organic hybrid frameworks comprising (alkyl)acrylate groups.
  • siloxane - organic hybrid frameworks comprising (alkyl)acrylate groups.
  • An example of such a hybrid precursor is described in J Sol Gel Sci Technol 2012, 61 , 2, 321.
  • the cross-linkable composition comprising monomeric, oligomeric or polymeric (alkyl)acrylate precursors may be crosslinked using free radical reactions.
  • the cross-linkable composition used to form crosslinkable films may additionally comprise a free radical initiator.
  • the free radical initiator is initiated under thermal or photochemical conditions.
  • free radical initiators suitable for either thermal or photochemical initiation, are known in the art.
  • Table 6 details free radical thermal initiators commercially available from Sigma Aldrich, a subsidiary of Merck KGaA (Germany). Table 6: Free radical thermal initiators available from Sigma Aldrich.
  • Table 7 details free radical photoinitiators commercially available from Sigma Aldrich, a subsidiary of Merck KGaA (Germany).
  • photochemical free radical initiators are available, allowing the operation of the photochemical crosslinking process at different wavelengths, including i line (365 nm) and g / h line (405 nm, 436 nm).
  • Type II initiators Certain types of commercially available photochemical free radical initiators are known as Type II initiators. These photoinitiators typically require the presence of a further reagent, known as a co - initiator. Commonly used examples of co - initiators for Type II systems are alcohols or amines.
  • co - initiators for Type II systems are alcohols or amines.
  • the monomeric, oligomeric and/or polymeric precursors are cross-linkable via a thiol - ene or a thiol (alkyl)acrylate reaction for example, as described below.
  • the thiol ene reaction involves the reaction of an unsaturated double bond with a separate precursor bearing a thiol (-SH) group.
  • the unsaturated double bond may be a (alkyl)acrylate, in which case the process may be described as a thiol - (alkyl)acrylate reaction.
  • the thiol - ene or thiol - (alkyl)acrylate reaction is typically a radical reaction, which may be initiated thermally or photochemically as described above for polymerisation processes using only (alkyl)acrylate precursors.
  • a useful property of the thiol - ene, or thiol - (alkyl)acrylate reaction, as used in the preparation of crosslinked thin film coatings, such as a passivation layer, is that the reaction process is less sensitive to inhibition from atmospheric oxygen, allowing the crosslinking process to be carried out in air rather than under an inert gas blanket.
  • Suitable precursors for thermal or photochemical crosslinking processes using thiol - ene or thiol - (alkyl)acrylate reactions may be monomeric, oligomeric or polymeric in nature.
  • the monomeric, oligomeric and/or polymeric precursors are cross-linkable via a thermal azide alkyne cycloaddition reaction, for example, as described below.
  • the cross-linkable composition comprises a polyimide.
  • polyimides are examples of oligomeric precursors.
  • Polyimides are useful materials for the formation of protective films. The chemistry and properties of polyimides are usefully reviewed in the Handbook of Polymer Coatings for Electronics : Chemistry, Technology and Applications (2 nd Edition) p 55 - 65. Efforts have been made to improve the solubility and solution processability of polyimides, and solvent soluble polyimides are known in the art.
  • a suitable class of polyimides for use in the current invention are soluble polyimide oligomers. Soluble polyimide oligomers may be further functionalised with suitable groups for thermal or photochemical crosslinking reactions, other than the backbone polyimide functional groups.
  • the polyimide oligomers have good solvent solubility properties due to their low average molecular weight, and may be conveniently coated by solution processing methods.
  • the resulting film may then be subjected to thermal or photochemical crosslinking processes, dependent on the nature of the further functionalised crosslinkable groups. This results in a highly insoluble crosslinked film. Examples of thermally crosslinked films produced from polyimide oligomers are described in EP 2524947 A1.
  • the cross-linkable composition comprises a cycloolefinic polymer.
  • cycloolefinic polymers are examples of oligomeric or polymeric precursors.
  • a further class of material useful for passivation layers in organic electronic devices are cycloolefinic polymers. Cycloolefinic polymers bearing chemical substituents allowing further thermal or photochemical crosslinking, after deposition of the non crosslinked film, are known in the art. Examples of suitable cycloolefinic polymers with crosslinkable side groups are described in US 9082981 and WO 2013 / 120581.
  • the cross-linkable composition comprises a substituted poly(vinylphenol) derivative, for example, as described below.
  • the poly(vinylphenol) may be substituted at the phenolic group (e.g. alkyl, aryl, aralkyl with optional further substitutions).
  • Chem Mater 2015, 25, 4806 shows one possible type of substitution (O-allyl).
  • Suitably substituted poly(vinylphenol) derivatives are a further class of crosslinked thin film coating precursors suitable for use in the cross-linkable composition.
  • Chem Mater 2015, 25, 4806 describes a soluble thin film forming composition comprising the O-allyl derivative of poly(vinylphenol) and pentaerythritol tetra(3-mercaptopropionate) which is then thermally crosslinked by thiol - ene reaction using AIBN as the radical initiator.
  • WO 2013 / 1 19717 describes derivatives of poly(vinylphenol) that may be crosslinked under photochemical conditions to provide insoluble films, such as a passivation layer.
  • the formulation comprises a surfactant, to improve coating properties, such as surface wetting, levelling and flow.
  • Formulations of the current invention may optionally comprise surfactants, for example fluorinated surfactants and/or siloxane solvents, to improve coating properties, such as surface wetting, levelling and flow.
  • An amount of a surfactant, such as a fluorosurfactant, in the formulation may be in a range of from 0 to 5% by weight of the formulation, preferably in a range of from 0 to 2 % by weight of the formulation.
  • the amount of the surfactant may be at least 0.001 %, at least 0.01 % or at least 0.1 % by weight of the formulation.
  • fluorosurfactant is commercially available from AGC Seimi Chemical Co., Ltd. (Japan) as SURFLON.
  • Table 8 details fluorosurfactants commercially available from Cytonix LLC, Maryland (USA) as FluorN.
  • Table 8 Fluorosurfactants available from Cytonix.
  • fluorosurfactants commercially available from DIC Corporation, Tokyo (Japan) as EGAFACE.
  • Preferred fluorosurfactants include MEGAFACE R-41 , R-40, R-40-LM, R-43, F-556, F- 557, F-554, F-559, RS-72-K, F-567, F-563, F-560, F-444, F-553, F-477, F-554, F-556, F-557, F-568, F- 563 and F-560.
  • F-570 Oligomer with fluoro, hydrophilic, lipophilic and carboxyl group
  • Formulations of the current invention may optionally comprise a siloxane solvent, particularly a cyclic siloxane solvent.
  • the siloxane solvent may be used to alter the wetting, levelling and flow properties of the formulation.
  • suitable siloxane solvent additives include octamethylcyclotetrasiloxane (BP 175 °C), decamethylcyclopentasiloxane (BP 210 °C) and dodecamethylcyclohexasiloxane (BP 245 °C).
  • the loading of siloxane solvent in the composition would be 0 - 10 % by weight of the passivation material, preferably 0 - 5 % by weight of the passivation material, more preferably 0 - 2 % by weight of the passivation material.
  • An amount of siloxane solvent in the formulation may be in a range of from 0 to 10 % by weight of the formulation, preferably in a range of from 0 to 5 % by weight of the passivation material, more preferably in a range of from 0 to 2 % by weight of the passivation material.
  • the amount of the surfactant may be at least 0.001 %, at least 0.01 % or at least 0.1 % by weight of the passivation material.
  • the formulation comprises a filler, to alter physical and/or electrical properties of the crosslinked layer.
  • Suitable compositions for use in the current invention may optionally also comprise a filler.
  • Fillers may usefully alter the physical and/or electrical properties of the crosslinked thin film coating, for example, dielectric constant, mechanical strength or dielectric breakdown strength.
  • Suitable fillers include inorganic nanoparticles, in which case the resulting crosslinked film may be described as a polymer nanocomposite. Examples of suitable fillers are described in Materials 2009, 2, 1697-1733; doi: 10.3390/ma2041697.
  • These described fillers include inorganic fillers, for example BaTi0 3 , PMN-PT (65/35), PbNb 2 0 6 , PLZT (7/60/40), Si0 2 , Al 2 0 3l Ta 2 0 5 , Ti0 2 , SrTi0 3 , Zr0 2 , Hf0 2 , HfSi0 4 , La 2 0 3 , Y 2 0 3 , o-I_aAI0 3 , CaCu 3 Ti 4 0i 2 and Lai.8Sr 0 . 2 NiO 4 .
  • These inorganic fillers may be provided as particles, for example microparticles and/or nanoparticles.
  • the organic semiconductor material (OSC) layer comprises a single component or muiticomponent blend of materials which may be evaporated or solution processed.
  • the OSC layer is preferably solution processable and can be polymeric but preferably comprises a semiconducting non-polymeric polycyclic compound, such as a semiconducting non-polymeric organic polycyclic compound, which is an OSC (also known as a small molecule organic semiconductor).
  • the semiconducting non-polymeric polycyclic compounds have charge carrier mobilities of 1CT 1 cm 2 /Vs or more, more preferably of 0.5 cm 2 /Vs or more, even more preferably of 2 cm 2 /Vs or more.
  • the semiconducting non-polymeric polycyclic compounds have charge carrier mobilities of less than 100 cm 2 /Vs.
  • the semiconducting non-polymeric polycyclic compound charge mobility can be determined through field effect transistor measurements on drop cast films or thermally evaporated single crystal films.
  • Any suitable semiconducting non-polymeric polycyclic compound may be used. These may be p-type or n-type OSC materials.
  • Suitable semiconducting non-polymeric polycyclic compounds include polyacenes.
  • Suitable polyacenes are disclosed in WO 2012/164282.
  • suitable polyacenes may have the Formula (III):
  • R 55 and R 33 are each -C ⁇ C-SiR 35 R 36 R 37 , wherein R 35 , R 36 and R 37 are each independently selected from C1-C4 alkyl, C 2 -C 4 alkenyl and C 3 -C 6 cycloalkyl;
  • R 50 , R 51 , R 52 , R 53 , R 57 , R 29 , R 30 and R 31 are each independently selected from hydrogen, C r C 4 alkyl, C C 6 alkoxy and C 6 -C 12 aryloxy; or wherein independently each pair of R 51 and R 52 and/or R 29 and R 30 may be cross- bridged to form a C 4 -C 10 saturated or unsaturated ring, which saturated or unsaturated ring may be intervened by an oxygen atom, a sulfur atom or a group shown by formula -N(R 49 )- (wherein R 49 is a hydrogen atom, a C C 6 alkyl group or a C C 10 perfluoroalkyl group; and wherein k and I are independently 0 or 1 , preferably both k and I are 1 or both k and I are 0.
  • k and I are both 1 ;
  • R and R are -C ⁇ C-SiR R R , wherein R 35 , R 36 and R 37 are each independently selected from ethyl, n-propyl, isopropyl, 1 -propenyl, 2-propenyl and C 3 -C 6 cycloalkyl; and
  • R 50 , R 51 , R 52 , R 53 , R 57 , R 29 , R 30 and R 31 are each independently selected from hydrogen, methyl, ethyl and methoxy.
  • Especially preferred polyacene compounds are those of Formulae (IV) and (V):
  • R , R , R and R are each independently selected from hydrogen, C C 6 alkyl and C C 6 alkoxy (preferably R 50 , R 53 , R 57 and R 31 are each independently selected from hydrogen, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, methoxy, ethoxy, propyloxy and butyloxy, more preferably hydrogen, methyl, propyl and methoxy);
  • R 51 , R 52 , R 29 and R 30 are each independently selected from hydrogen, Ci-C 6 alkyl and Ci-C 6 alkoxy, or each pair of R 51 and R 52 and/or R 29 and R 30 , are cross-bridged to form a C 4 -C 10 saturated or unsaturated ring, which saturated or unsaturated ring may be intervened by an oxygen atom, a sulfur atom or a group shown by formula -N(R 38 )- (wherein R 38 is hydrogen or C C C 6
  • R , R and R are each independently selected from C C 6 alkyl and C 2 -C 6 alkenyl (preferably R 39 , R 40 and R 41 are each independently selected from methyl, ethyl, propyl, isopropyl, n- butyl, isobutyl, t-butyl, 1 -propenyl and 2-propenyl, more preferably ethyl, n-propyl and isopropyl);
  • R and R are each independently selected from hydrogen, halogen, cyano, optionally fluorinated or perfluorinated C C 2 o alkyl, fluorinated or perfluorinated, C C 2 o alkoxy, fluorinated or perfluorinated C 6 - C 30 aryl and C0 2 R 44 , wherein R 44 is hydrogen, fluorinated or perfluorinated C 1 -C 2 o alkyl, or fluorinated or perfluorinated C 6 -C 30 aryl (preferably R 42 and R 43 are each independently selected from fluorinated or perfluorinated C C 8 alkyl, fluorinated or perfluorinated Ci-C 8 alkoxy and C 6 F 5 ); and
  • polyacene compounds of the present invention are those of Formulae (VI) and (VII):
  • R , R and R are each independently selected from methyl, ethyl and isopropyl; wherein R , R , R , R , R , R J0 and R J are each independently selected from C C 6 alkyl, C C 6 alkoxy and C 6 -C 20 aryloxy.
  • R 50 , R 51 , R 52 , R 53 , R 57 , R 29 , R 30 and R 31 are each independently selected from methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, methoxy, ethoxy, propyloxy and butyloxy.
  • Polyacene compounds may be synthesised by any known method within the common general knowledge of a person skilled in the art. In a preferred embodiment, methods disclosed in US 2003/01 16755 A, US 3,557,233, US 6,690,029 WO 2007/078993, WO 2008/128618 and Organic Letters, 2004, Volume 6, number 10, pages 1609-1612 can be employed for the synthesis of polyacene compounds.
  • the polyacene compounds have charge carrier mobilities of 10 "1 cm 2 /Vs or more, more preferably of 0.5 cm 2 /Vs or more, even more preferably of 2 cm 2 /Vs or more.
  • the polyacene compounds have charge carrier mobilities of less than 100 cm 2 /Vs.
  • the polyacene charge mobility can be determined through field effect transistor measurements on drop cast films or thermally evaporated single crystal films.
  • a suitable polyacene is 1 ,4,8,1 1 -tetramethyl-6,13-bis(triethylsilylethynyl)pentacene (TMTES).
  • Alternative semiconducting non-polymeric polycyclic compounds used in the invention could include the following materials, either applied via solution processing or evaporation: pentacene, 2,7- Dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT), 2,9-didecyldinaphtho[2,3-b:2',3'-f]thieno[3,2- b]thiophene (C10-DNTT), 3,11-didecyl-dinaphtho[2,3-d:2',3'-d]benzo[1 ,2-b:4,5-bldithiophene (C10- DNBDT), 8,17-bis((triisopropylsilyl)ethynyl)tetraceno[2,1 ,12-qra]tetracene (Formula (VIII)), 8,17- bis((diisopropyl(octy
  • Suitable n-type small molecules could include naphthalene diimides (NTCDI) or perylene tetracarboxylic diimides (PTC DA), [6,6]-phenyl-C61 -butyric acid ester ([60]PCBM) and [6,6]-phenyl-C71 -butyric acid methyl ester ([70]PCBM).
  • NTCDI naphthalene diimides
  • PTC DA perylene tetracarboxylic diimides
  • [6,6]-phenyl-C61 -butyric acid ester [60]PCBM
  • PCBM [6,6]-phenyl-C71 -butyric acid methyl ester
  • the OSC layer may optionally comprise a polymeric binder material to aid film forming and uniformity.
  • Suitable binder materials can be found in WO2012160383 which discloses high-k (permittivity > 3.4) binders in combination with small molecule semiconductors, or WO2005055248 which discloses low-k binders (1.1 ⁇ k ⁇ 3.3) in combination with small molecule semiconductors.
  • Suitable OGI materials are polymers that can be crosslinked such that they are solvent resistant or based upon polymers that are not soluble in levoglucosenone or dihydrolevoglucosenone or a derivative thereof.
  • preferred polymers include polymers with greater than 30% of fluorine by weight and are soluble in fluorinated or perfluorinated solvents.
  • preferred soluble amorphous fluoropolymers include Cytop (Asahi), Teflon AF (DuPont), Hyflon AD (Solvay), Fluoropel (Cytonix).
  • Suitable solvents for the fluorinated OGI layer include Fluorinert (trade name) FC43, or Hydrofluoroethers Novec (3M) HFE7500 or HFE7700.
  • OGI materials may be vapor deposited through chemical vapor deposition, such as parylene, or thermal evaporation, but it is especially preferred that the OGI is deposited by solution processing.
  • the passivation layer provides an interlayer dielectric, arranged to isolate, for example electrically isolate, metal layers, for example a metal gate electrode from a source and/or drain electrode, on the OE device.
  • Dihydrolevoglucosenone For the avoidance of doubt, statements of invention below explicitly recite dihydrolevoglucosenone, as described above in detail.
  • the formulation, the solvent and/or the passivation material, together with the OE device and the organic layer, may be as described above in relation to this first aspect.
  • the solvent comprises dihydrolevoglucosenone.
  • the solvent comprises dihydrolevoglucosenone and the passivation material comprises the cross-linkable composition.
  • the solvent comprises dihydrolevoglucosenone and the cross-linkable composition comprises monomeric, oligomeric and/or polymeric precursors. In one example, the solvent comprises dihydrolevoglucosenone and the monomeric, oligomeric and/or polymeric precursors comprise an epoxy group.
  • the solvent comprises dihydrolevoglucosenone and the monomeric, oligomeric and/or polymeric precursors comprise acrylate or methacrylate repeat units.
  • the solvent comprises dihydrolevoglucosenone and the monomeric, oligomeric and/or polymeric precursors are cross-linkable via a thiol - ene or a thiol (alkyl)acrylate reaction.
  • the solvent comprises dihydrolevoglucosenone and the monomeric, oligomeric and/or polymeric precursors are cross-linkable via a thermal azide alkyne cycloaddition reaction.
  • the solvent comprises dihydrolevoglucosenone and the cross-linkable composition comprises a polyimide.
  • the solvent comprises dihydrolevoglucosenone and the cross-linkable composition comprises a cycloolefinic polymer.
  • the solvent comprises dihydrolevoglucosenone and the cross-linkable composition comprises a substituted poly(vinylphenol) derivative.
  • the solvent comprises dihydrolevoglucosenone and the formulation comprises at least one of a cross-linking agent, a photoacid generator, a hardening agent, an antioxidant agent, a surfactant, and a filler.
  • the solvent comprises dihydrolevoglucosenone and a cosolvent.
  • the second aspect of the invention provides a method of fabricating an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer, wherein the method comprises:
  • the method comprises providing a substrate.
  • the substrate may comprise glass, metal, a polymer or an IC, for example.
  • the substrate may include an optional buffer layer (also known as a sublayer) provided on the surface of the substrate.
  • the buffer layer may also be known as a polarization layer, provided by a crosslinkable polymer that may improve surface uniformity and/or homogeneity by smoothing imperfections in the surface of the substrate and may provide a chemically insert surface upon which an OE device is fabricated.
  • the buffer layer may comprise SU-8, crosslinked acrylate polymers or polycycloolefinic polymers, for example.
  • the substrate may comprise polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), for example, which may be processed without a buffer layer.
  • PET polyethylene terephthalate
  • PEN polyethylene naphthalate
  • the method comprises providing a source and/or a drain electrode on the surface of the substrate, for example by sputtering and photolithography.
  • the source and the drain electrodes are typically a metal, for example silver or gold or alloys thereof, or a non-metal.
  • the source and the drain electrodes may be treated with a thiol solution, to adjust work functions of the source and the drain electrodes. In this way, injection of charges into an overlaying OSC layer may be improved. Excess thiol solution may be washed away, with thiol binding only to the source and the drain electrodes.
  • the method comprises providing an OSC layer over the source and the drain electrodes and the exposed surface of the substrate, for example by spin coating or printing.
  • the OSC layer typically has a thickness of 30 nm.
  • the method comprises providing an OGI layer over the OSC layer, for example by spin coating or printing.
  • the OGI layer typically has a thickness of 300 nm.
  • a metal layer for example silver or gold or alloys thereof, may be subsequently deposited on the OGI layer, for example by evaporation.
  • a photoresist may be subsequently patterned (e.g. by photolithography) on the metal layer and portions of the metal layer exposed through the patterned photoresist may be removed by wet etching.
  • the patterned metal layer may provide a gate, such as a thin film transistor (TFT) gate.
  • the patterned metal layer may provide a hardmask against reactive ion etching (RIE) (also known as dry etching, for example using 0 2 and/or Ar), thereby masking the underlying OGI layer, the OSC layer and the source and the drain electrodes. Subsequently, RIE may remove portions of the OGI layer and the OSC layer, that are not masked by the patterned metal layer. In this way, a stack comprising the patterned metal layer, OGI layer, the OSC layer and the source and the drain electrodes may be provided on the substrate. It should be understood that the stack generally describes a multilayered structure and thus may comprise more or fewer and/or different layers.
  • the stack may comprise those layers at an intermediary stage of fabrication of the OE device.
  • the stack may comprise all layers of the completed OE device. That is, layers included in the stack may change during fabrication, by addition and/or by removal of layers. Sides of the OGI layer and sides of the OSC layer may be thus exposed, for example by the RIE, and may be adversely affected by unsuitable solvents.
  • inter-layer interfaces may also be exposed, for example between the substrate and the OSC layer, between the OSC layer and the OGI layer and/or between the OGI layer and the metal layer. These inter-layer interfaces may be subject to solvent penetration, as described previously, thereby providing another vector of attack by unsuitable solvents. Other surfaces of the OGI layer and/or the OSC layer may be additionally and/or alternatively exposed.
  • the method comprises providing the passivation layer over the stack and the exposed surface of the substrate, for example, by coating with a formulation according to an exemplary embodiment of the invention.
  • the method comprises providing a positive photoresist mask over the passivation layer.
  • the method comprises forming a first hole or via through the passivation layer to the patterned metal layer, by RIE through the positive photoresist mask, thereby exposing at least a part of the surface of the metal layer.
  • the method comprises removing residual photoresist mask.
  • the method comprises providing a metal gate interconnect through the first hole to the patterned metal layer, for example, by sputtering, masking and etching.
  • the third aspect of the invention provides an organic electronic (OE) device comprising an organic layer and a passivation layer directly thereon, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer and wherein the passivation layer comprises a cross-linked product of a cross-linkable composition according to the first aspect.
  • OSC organic semiconductor
  • OTI organic gate insulator
  • the OE device is selected from a group consisting of an Organic Field Effect Transistor (OFET) such as a bottom gate OFET or preferably a top gate OFET , including Organic Thin Film Transistors (OTFT), an Organic Light Emitting Diode (OLED), an Organic Photovoltaic (OPV) device and an Organic Photodetector (OPD).
  • OFET Organic Field Effect Transistor
  • OTFT Organic Thin Film Transistors
  • OLED Organic Light Emitting Diode
  • OPD Organic Photovoltaic
  • OPD Organic Photodetector
  • the fourth aspect of the invention provides a product comprising an organic electronic (OE) device fabricated according to the second aspect and/or an OE device according to the third aspect.
  • the product is selected from a group consisting of an Integrated Circuit (IC), a Radio Frequency Identification (RFID) tag, a security marking or security device containing an RFID tag, a Flat Panel Display (FPD), a backplane of an FPD, a backlight of an FPD, an electrophotographic device, an electrophotographic recording device, an organic memory device, a sensor, a biosensor and a biochip.
  • IC Integrated Circuit
  • RFID Radio Frequency Identification
  • FPD Flat Panel Display
  • FPD Flat Panel Display
  • backplane of an FPD a backlight of an FPD
  • electrophotographic device an electrophotographic recording device
  • organic memory device a sensor, a biosensor and a biochip.
  • the fifth aspect of the invention provides a flowable formulation comprising a photopatterning material and a solvent
  • the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof.
  • the solvent may be as described with respect to the first aspect.
  • the photopatterning material may be similar to the passivation material described with respect to the first aspect.
  • the sixth aspect of the invention provides use of a solvent comprising levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof in a method of fabricating an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer.
  • OE organic electronic
  • OSC organic semiconductor
  • OTI organic gate insulator
  • Figure 1 shows schematically a method of fabrication of an OE device using conventional solution processable passivation materials
  • Figure 2 schematically depicts a 2D Hansen solubility parameter map
  • Figure 3 shows schematically a method of fabrication of an OE device according to an embodiment of aspects of the invention
  • Figure 4 shows schematically another method of fabrication of an OE device according to an embodiment of aspects of the invention
  • Figures 5A and 5B show transfer and mobility curve data, respectively, after gold gate electrode patterning of OE devices fabricated according to an embodiment of aspects of the invention
  • Figure 6A and 6B show transfer and mobility curve data, respectively, after dry etch patterning of the OE devices of Figure 5;
  • Figures 7A and 7B shows transfer and mobility curve data, respectively, after passivation layer deposition of the OE devices of Figure 6;
  • Figures 8A and 8B show optical micrographs of the OE devices of Figure 6 after washing with Cyrene and PGMEA, respectively;
  • Figures 9A and 9B show optical micrographs of the OE devices of Figure 6 after washing with Cyrene and GBL, respectively;
  • Figure 10 shows an optical micrograph of via structures, formed by photopatterning according to an exemplary embodiment of the invention
  • Figure 1 1 shows resistance data for the via structures of Figure Figure 12 shows an OE device at a step of fabrication according to an embodiment of aspects of the invention
  • Figures 13A - 13C show optical micrographs of OE devices of the type of Figure 12 after washing with mixtures of Cyrene and IPA, Cyrene and GBL and Cyrene and PGMEA, respectively;
  • Figure 14 shows an optical micrograph of a product according to an exemplary embodiment of the invention
  • Figure 15 shows an optical micrograph of a product according to an exemplary embodiment of the invention.
  • Figure 3 shows schematically a method of fabrication of an OE device, specifically a top gate OFET, according to an embodiment of aspects of the invention.
  • a method of fabrication may be achieved practically by photolithographic processing, as known to the person skilled in the art.
  • a formulation according to an exemplary embodiment of the invention is used, thereby eliminating at least one step of the prior art method.
  • OE device fabrication complexity and/or cost may be reduced.
  • water-soluble polymers, such as PVA which may be hygroscopic, are avoided, thereby improving long-term stability of OE devices fabricated according to exemplary embodiments of the invention.
  • the formulation used comprises a 'green' solvent, thereby improving an environmental profile of the formulation.
  • the substrate 310 may comprise glass, metal, a polymer or an IC, for example.
  • the substrate 310 may include an optional buffer layer (also known as a sublayer) provided on the surface of the substrate 310.
  • the buffer layer may also be known as a planarization layer, provided by a crosslinkable polymer that may improve surface uniformity and/or homogeneity by smoothing imperfections in the surface of the substrate and may provide a chemically insert surface upon which the OE device is fabricated.
  • the buffer layer may comprise crosslinked acrylate polymers or polycycloolefinic polymers, for example.
  • the substrate 310 may comprise polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), for example, which may be processed without a buffer layer.
  • source and drain electrodes 320 are provided on the surface of the substrate 310, for example by sputtering and photolithography (using mask 1 ).
  • the source and the drain electrodes 320 are typically a metal, for example silver or gold or alloys thereof, or a non-metal.
  • the source and the drain electrodes 320 may be treated with a thiol solution, to adjust work functions of the source and the drain electrodes 320. In this way, injection of charges into an overlaying OSC layer may be improved. Excess thiol solution may be washed away, with thiol binding only to the source and the drain electrodes 320.
  • an OSC layer 330 is first provided over the source and the drain electrodes 320 and the exposed surface of the substrate 310, for example by spin coating or printing.
  • the OSC layer 330 typically has a thickness of 30 nm.
  • An OGI layer 340 is subsequently provided over the OSC layer 330, for example by spin coating or printing.
  • the OGI layer 340 typically has a thickness of 300 nm.
  • a metal layer 350 for example silver or gold or alloys thereof, is subsequently deposited on the OGI layer 340, for example by evaporation.
  • a photoresist (not shown) is subsequently patterned (e.g.
  • the patterned metal layer 350 provides a gate, such as a thin film transistor (TFT) gate.
  • the patterned metal layer 350 also provides a hardmask (mask 2) against reactive ion etching (RIE) (also known as dry etching, for example using 0 2 and/or Ar), thereby masking the underlying OGI layer 340, the OSC layer 330 and the source and the drain electrodes 320. Subsequently, RIE removes portions of the OGI layer 340 and the OSC layer 330, that are not masked by the patterned metal layer 350.
  • RIE reactive ion etching
  • a stack 300 comprising the patterned metal layer 350, OGI layer 340, the OSC layer 330 and the source and the drain electrodes 320 is provided on the substrate 310.
  • the stack 300 generally describes a multilayered structure and thus may comprise more or fewer and/or different layers.
  • the stack 300 may comprise those layers at an intermediary stage of fabrication of the OE device.
  • the stack 300 may comprise all layers of the completed OE device. That is, layers included in the stack 300 may change during fabrication, by addition and/or by removal of layers.
  • Sides 341 of the OGI layer 340 and sides 331 of the OSC layer 330 may be thus exposed, for example by the RIE, and may be adversely affected by unsuitable solvents.
  • inter-layer interfaces may also be exposed, for example between the substrate 310 and the OSC layer 330, between the OSC layer 330 and the OGI layer 340 and/or between the OGI layer 340 and the metal layer 350. These inter-layer interfaces may be subject to solvent penetration, as described previously, thereby providing another vector of attack by unsuitable solvents. Other surfaces of the OGI layer 340 and/or the OSC layer 330 may be additionally and/or alternatively exposed.
  • a passivation layer 360 is provided over the stack 300 and the exposed surface of the substrate 310, for example, by coating with a formulation according to an exemplary embodiment of the invention.
  • the formulation comprises a passivation material and a solvent, wherein the solvent comprises levoglucosenone, dihydrolevoglucosenone or a derivative thereof.
  • the passivation material comprises a cross-linkable composition, for example bisphenol A novolac epoxy, and the solvent comprises dihydrolevoglucosenone.
  • the passivation material is dissolved in the solvent.
  • the single passivation 360 provides the robustness required for providing environmental, chemical and/or physical protection of the fabricated OE device, similar to the second passivation layer 190 described above, that required also the first passivation layer 180. In this way, OE device fabrication complexity and/or cost may be reduced. Furthermore, water-soluble polymers, such as PVA, which may be hygroscopic, are avoided, thereby improving long-term stability of OE devices fabricated according to exemplary embodiments of the invention.
  • the formulation used comprises a 'green' solvent, thereby improving an environmental profile of the formulation.
  • the passivation material is crosslinked by UV.
  • the passivation layer 360 typically has a thickness of between 300 nm and 2000 nm.
  • a positive photoresist mask 361 (mask 3) is provided over the passivation layer 360, similarly to as described previously at S105 with reference to Figure 1.
  • a first hole or via is formed through the passivation layer 360 to the patterned metal layer 350, by RIE through the positive photoresist mask 361 , thereby exposing at least a part of the surface of the metal layer 350, similarly to as described previously at S106 with reference to Figure 1.
  • OE device fabrication complexity and/or cost may be reduced.
  • water-soluble polymers such as PVA, which may be hygroscopic, are avoided, thereby improving long-term stability of OE devices fabricated according to exemplary embodiments of the invention.
  • the formulation used comprises a 'green' solvent, thereby improving an environmental profile of the formulation.
  • a metal gate interconnect 370 is provided through the first hole to the patterned metal layer 350, for example, by sputtering, masking (mask 4) and etching , similarly to as described previously at S107 with reference to Figure 1.
  • the OE device may be provided, having a single passivation layer 360.
  • the single passivation layer 360 may be required. Furthermore, water-soluble polymers, are avoided.
  • the formulation used comprises a 'green' solvent.
  • mask 1 - mask 4 only four masks are required, unlike the conventional process which requires five masks.
  • Figure 4 shows schematically a method of fabrication of another OE device, according to an embodiment of aspects of the invention.
  • a method of fabrication may be achieved practically by photolithographic processing, as known to the person skilled in the art.
  • a formulation according to an exemplary embodiment of the invention is used, thereby eliminating at least one step of the prior art method.
  • OE device fabrication complexity and/or cost may be reduced.
  • water-soluble polymers, such as PVA which may be hygroscopic, are avoided, thereby improving long-term stability of OE devices fabricated according to exemplary embodiments of the invention.
  • the formulation used comprises a 'green' solvent, thereby improving an environmental profile of the formulation.
  • a substrate 410 is provided.
  • the substrate 410 may comprise glass, metal, a polymer or an IC, for example.
  • the substrate 410 may include an optional buffer layer provided on the surface of the substrate 410.
  • the buffer layer may also be known as a planarization layer, provided by a crosslinkable polymer that may improve surface uniformity and/or homogeneity by smoothing imperfections in the surface of the substrate and may provide a chemically insert surface upon which the OE device is fabricated.
  • an OSC layer 430 is first provided over the exposed surface of the substrate 410, for example by spin coating or printing.
  • the OSC layer 430 typically has a thickness of 30 nm.
  • an OGI layer 440 is subsequently provided over the OSC layer 430, for example by spin coating or printing.
  • the OGI layer 440 typically has a thickness of 300 nm.
  • a stack 400 comprising the OGI layer 440 and the OSC layer 430 is provided on the substrate 410.
  • the stack 400 generally describes a multilayered structure and thus may comprise more or fewer and/or different layers.
  • the stack 400 may comprise those layers at an intermediary stage of fabrication of the OE device.
  • the stack 400 may comprise all layers of the completed OE device. That is, layers included in the stack 400 may change during fabrication, by addition and/or by removal of layers.
  • Sides 441 of the OGI layer 440 and sides 431 of the OSC layer 430 may be thus exposed, for example by the RIE, and may be adversely affected by unsuitable solvents.
  • inter-layer interfaces may also be exposed, for example between the substrate 410 and the OSC layer 430 and/or between the OSC layer 430 and the OGI layer 440. These inter-layer interfaces may be subject to solvent penetration, as described previously, thereby providing another vector of attack by unsuitable solvents.
  • Other surfaces of the OGI layer 440 and/or the OSC layer 430 may be additionally and/or alternatively exposed.
  • a passivation layer 460 is provided over the stack 400 and the exposed surface of the substrate 410, for example, by coating with a formulation according to an exemplary embodiment of the invention.
  • the passivation layer 460 may be provided as described previously with reference to S304.
  • the formulation comprises a passivation material and a solvent, wherein the solvent comprises levoglucosenone, dihydrolevoglucosenone or a derivative thereof.
  • the solvent comprises levoglucosenone, dihydrolevoglucosenone or a derivative thereof.
  • the single passivation layer 460 provides the robustness required for providing environmental, chemical and/or physical protection of the fabricated OE device, similar to the second passivation layer 190 described above, that required also the first passivation layer 180. In this way, OE device fabrication complexity and/or cost may be reduced.
  • water-soluble polymers such as PVA, which may be hygroscopic, are avoided, thereby improving long-term stability of OE devices fabricated according to exemplary embodiments of the invention.
  • the formulation used comprises a 'green' solvent, thereby improving an environmental profile of the formulation.
  • OE device fabrication complexity and/or cost may be reduced.
  • water-soluble polymers such as PVA, which may be hygroscopic, are avoided, thereby improving long-term stability of OE devices fabricated according to exemplary embodiments of the invention.
  • the formulation used comprises a 'green' solvent, thereby improving an environmental profile of the formulation.
  • the OE device may be provided, having a single passivation layer 460.
  • Example 1 relates to fabrication of an OTFT device, including a passivation formulation of SU-8 polymer in Cyrene solvent.
  • 20cm x 20cm glass substrates were cleaned using sonication for 20 minutes in Deconex (3% w/w in water) followed by rinsing in ultrapure water and dried using compressed air.
  • the substrates were baked at 70°C for 30 minutes in a convection oven.
  • the substrates were then spin coated with a thermally crosslinkable polymer (P1 1 ) (available to the public from NeuDrive Ltd) as a buffer layer (also known as sublayer). After spin coating, the substrates were first placed on a hotplate at 95°C for 2 minutes to softbake, then baked at 150°C for 60 minutes. The final thickness of the P11 layer was measured to be 1 micron.
  • P1 1 thermally crosslinkable polymer
  • the substrates were sputter coated with 50 nm of Au, then source and drain electrodes were prepared with a combination of photolithographic and wet etching techniques (potassium iodide and iodine in water etchant composition). The substrates were then scribed into 4 equal sized pieces (10cm x 10cm) and processed at this size for the remainder of the fabrication. After removal of the residual photolithographic resist from the source and drain contact by UV flash exposure and spin developing, the substrates were inspected under an optical microscope and channel length features measured in several areas of the substrate.
  • the substrates were treated in a Plasma Etch Inc. PE100 surface treatment system, using an Ar/0 2 plasma. Each gas was supplied at a concentration of 50 seem and a RF power of 250 W for 65 s.
  • the substrates were then coated with 50 nm of Au by thermal evaporation and the gate electrodes were patterned as before with a combination of photolithography and wet etching. Following this the photoresist on the Au removed by UV flash exposure and development. The OTFTs were electrically tested to check for functionality prior to further processing.
  • OTFT characterisation OTFTs were tested using a Wentworth Pegasus 300S semi-automated probe station in conjunction with a Keithley S4200 semiconductor parameter analyser. This allowed a statistically significant number of OTFT device measurements to be made on each substrate.
  • the Keithley system calculated the linear mobility according to the equation shown below:
  • V DS drain source voltage
  • V G s gate voltage
  • the mobility values reported are an average of the 5 highest points in accumulation for each transistor. The data is reported for the channel lengths shown below and is displayed as an average of the devices measured. To exclude devices with gate leakage, a ratio of the gate current to the source-drain current was made at the highest V G s value for a V DS of -2V. If this ratio was below 10 (i.e.
  • V t0 Turn on voltage of the transistors
  • V t0 the gate voltage point at which the derivative of the logarithm of the drain current with respect to gate voltage is a maximum. It represents the transition point where the device starts to switch from the off state towards the on state.
  • On/off ratio is defined as the maximum current in accumulation (at V g --30V) divided by the off current in depletion.
  • the OSC and dielectric layers were patterned by reactive ion etching (RIE) using an Oxford Plasmalab 800 Plus system with a gas supply of 100 seem 0 2 , at a power of 500W for 120s (pressure was 200 mTorr).
  • RIE reactive ion etching
  • the removal of the dielectric and OSC layer was confirmed by inspection under cross polarisers. Areas that were removed showed no sign of crystalline OSC film remaining.
  • the substrate was again electrically tested in order to determine the change in performance due to the dry etching process.
  • Application of the passivation layer (SU-8 in cyrene solvent)
  • An example passivation formulation was provided containing 1.5 g EPON-SU-8 base polymer (i.e. a passivation material comprising a cross-linkable composition, wherein the cross-linkable composition comprises polymeric precursors comprising epoxy groups) and 16.4 g Cyrene (i.e. dihydrolevoglucosenone).
  • the passivation formulation further contained 0.6 g Triarylsulfonium hexafluoroantimonate (50% solution by weight in propylene carbonate) as a cross-linking agent. That is, the solvent of this passivation formulation comprises 16.4 g Cyrene together with 0.3 g propylene carbonate as a cosolvent.
  • the passivation formulation was spin coated (at 500 rpm for 5 s followed by 3000 rpm for 25 s) onto the dry etched OTFT devices on the substrate.
  • the passivation layer was then softbaked at 95°C for 2 minutes followed by UV exposure 400 mJ/cm 2 followed by hardbaking for 10 minutes at 1 15°C to crosslink the film.
  • the sample was inspected under the microscope to confirm that none of the OTFT structures had been affected by the process.
  • the sample was then electrically tested to confirm that the application of the passivation layer to the device had not affected the performance of the OTFT devices. Data were compared for devices tested after the initial fabrication, after the dry etch process and after the passivation layer application to see the effect of each of the processes.
  • results of the testing of the OTFTs at different steps of fabrication include measurement of the average mobility, mobility standard deviation (as a percentage), average on/off ratio and average turn on voltage, as detailed in Tables 10 - 12.
  • the results of the testing after the initial fabrication, after the dry etch process and after the passivation layer application also include transfer and mobility data for individual OTFT devices, as shown in Figures 5 to 7, which relate to Tables 10 - 12 respectively.
  • Table 10 details electrical test data after Au gate electrode patterning (i.e. after initial fabrication) of the OTFTs.
  • Table 11 details electrical test data after Au gate electrode patterning.
  • Table 12 details electrical test data after application of the passivation layer.
  • Tables 10 - 12 and Figures 5 - 7 indicate that the electrical parameters have changed by less than 5% when comparing the same OTFT devices and overall have changed on average just over 0.1cm 2 /Vs. That is, as can be seen from the electrical results, the application of the passivation layer according to an embodiment of the invention has a minimal effect on the electrical characteristics of the OTFT devices.
  • Figures 8A, 8B, 9A and 9B schematically depict effects of washing the dry etched OTFT devices with different solvents, thereby distinguishing between orthogonal and non-orthogonal solvents.
  • This test demonstrates the extent to which test solvents interact with the dry etched OTFT materials stack and therefore whether a passivation layer material could be coated from the test solvents.
  • a test solvent was dispensed over the entire substrate, left for 20 s and then spun off at 1500 rpm for 20 s followed by baking at 100°C for 60 s.
  • Figures 8A and 8B show optical micrographs of the OTFT devices of Figure 6 after washing in Cyrene and PGMEA, respectively. Particularly, Figures 8A and 8B show optical micrographs of the OTFT devices of Figure 5 following dry etch patterning and after washing in Cyrene and PGMEA, respectively. As shown in Figure 8A, following Cyrene coating, the gate layer 850A of the OTFT device 800A has not moved at all and the OSC/OGI materials are over the channel area of the OTFT (to be marked in Figures).
  • Figure 8B following PGMEA coating, the gate layer 850B of the OTFT device 800B has moved due to delamination of the OSC/OGI/gate metal layer (to be marked in Figures). That is, Cyrene is an orthogonal solvent while PGMEA is not an orthogonal solvent.
  • Figures 9A and 9B show optical micrographs of the OE devices of Figure 6 after washing in Cyrene and GBL, respectively. Particularly, Figures 9A and 9B show optical micrographs of the OTFT devices of Figure 5 following dry etch patterning and after washing in Cyrene and GBL, respectively.
  • Example 2 relates to photopatterning, including a photopattemable formulation of SU-8 polymer in Cyrene solvent.
  • 10cm x 10cm glass substrates (Corning Eagle XG) were cleaned using sonication for 20 minutes in Deconex (3% w/w in water) followed by rinsing in ultrapure water and dried using compressed air.
  • the substrates were baked at 70°C for 30 minutes in a convection oven.
  • the substrates were then spin coated with a thermally crosslinkable polymer (P11 ) (available to the public from NeuDrive Ltd). After spin coating, the substrates were first placed on a hotplate at 95 °C for 2 minutes to softbake, then baked at 150 °C for 60 minutes. The final thickness of the P11 layer was measured to be 1 micron.
  • P11 thermally crosslinkable polymer
  • the substrates were sputter coated with 50 nm of Au, then metal via pad patterns were prepared with a combination of photolithographic and wet etching techniques (potassium iodide and iodine in water etchant composition). After removal of the residual photolithographic resist from the source and drain contact by UV flash exposure and spin developing, the substrates were inspected under an optical microscope.
  • a formulation was prepared using EPON SU-8 solution 1.5 g EPON-SU-8, 0.3 g Triarylsulfonium hexafluoroantimonate (50% solution by weight in propylene carbonate), 16.4 g Cyrene solvent. This equates to 10% photoinitiator by weight of the SU-8 polymer.
  • the formulation of SU-8 and photoinitiator in Cyrene was spin coated at 200 rpm for 10 s followed by 1000 rpm for 30 s and then baked for 2 minutes at 95°C on a hotplate to form a dry film.
  • the film was then exposed to UV (365nm wavelength) through a photomask (VIA MASK) using an EVG 6200 mask aligner in proximity mode (5 micron gap) to selectively expose parts of the film to light.
  • the VIA MASK was aligned with the first metal layer to ensure via holes were patterned over the metal bottom pads.
  • the film was post exposure baked at 95 °C for 2 minutes.
  • the film was flooded with MicropositTM EC solvent (Rohm and Haas) for 30 s, then spun at 1000 rpm with developer rinse for 5 s followed by 2500 rpm spin for 30 s to dry the film.
  • Figure 10 shows an optical micrograph of via structures, particularly finished via chains, formed by the photopatterning.
  • the via structures formed in the material was imaged to check that they were formed correctly.
  • the substrate was then sputter coated with 50 nm of Au metal and this layer was patterned by photolithography and wet etching to form the top metal pad of the via structure.
  • the dimensions of the vias were measured using a microscope and camera with image analysis software (in this image the vias were between 15 and 16 microns). The smallest via chains formed were 6 microns.
  • Figure 11 shows resistance data for the via structures.
  • the vias were electrically tested using an LCR meter (Agilent) to measure the resistance between the contact pads of the via chain. Results are shown in the graph for via chains containing different numbers of via connections. As can be seen from the results there is a low resistance connection for via chains up to 50 connections with small vias contributing 3.3 Ohms per via and larger diameter vias contributing 2.8 Ohms per via. This demonstrates that the photopatternable SU-8 formulation in Cyrene can be imaged effectively to form high resolution via structures suitable for interconnecting TFTs in electronic devices.
  • Example 3 relates to washing dry etched OTFT devices with different solvent mixtures (i.e. further including a cosolvent), thereby distinguishing between orthogonal and non-orthogonal solvent mixtures.
  • Figure 12 shows an OE device 1200A at a step of fabrication according to an embodiment of aspects of the invention and Figures 13A - 13B show optical micrographs of OE devices of the type of Figure 12 after washing with solvent mixtures of Cyrene and IPA, Cyrene and GBL, and Cyrene and PGMEA, respectively.
  • Figure 12 shows the OE device 1200 at the step of fabrication corresponding to the step S303, as described above with reference to Figure 3.
  • the substrate 1210 with stack 1200 was produced using the stack etch, as described above, in an Oxford Plasmalab 800Plus RIE system. The etch takes off the OSC/OGI layers and over-etches about 300-400 nm into the P11 sublayer. Solvent mixtures, as detailed in Tables 13A - 13B respectively, were deposited on one quarter of different parts of the substrate 1210 containing the stack 1200, left for 20 s, spun at 500 rpm for 10 s and then spun at 1500 rpm for 20 s to remove the solvent. The substrate 1210 plus stack 1200 structures were baked on a hotplate for 1 minute at 100 °C, to dry off the solvent mixture.
  • Figure 13A shows the optical micrograph of the OE device 1300A, following washing with IPA 100 wt.%.
  • OSC crystallinity is observed up an edge of the metal layer 1350A, indicating that IPA does not adversely affect the OSC layer 1330A.
  • IPA improves wetting, as described previously.
  • Table 13A summarises results of washing with different solvent mixtures of Cyrene and IPA, in which the tested mixtures were found to not adversely affect the OSC layer 1330A.
  • Table 13A Solvent mixtures and results for Cyrene and IPA Cyrene !PA
  • Figure 13B shows the optical micrograph of the OE device 1300B, following washing with a solvent mixture consisting of Cyrene 80 wt.% and GBL 20 wt.%. Undercutting between the metal layers 1320B and 1350B is observed, possibly due to dissolution of the OSC layer 1330B, indicating that GBL does adversely affect the OSC layer 1330B.
  • Table 13B summarises results of washing with different mixtures of Cyrene and GBL, in which the tested mixtures were found to adversely affect the OSC layer 1330B at solvent mixtures including GBL at 20 wt.% GBL and above.
  • Figure 13C shows the optical micrograph of the OE device 1300C, following washing with a solvent mixture consisting of Cyrene 80 wt.% and PG EA 10 wt.%. Damage of the OSC layer 1330C is observed.
  • Table 13C summarises results of washing with different mixtures of Cyrene and PGMEA, in which the tested solvent mixtures were found to adversely affect the OSC layer 1330C at solvent mixtures including PGMEA at 10 wt.% PGMEA and above.
  • Example 4 relates to a product 14000, particularly a decoder circuit, according to an exemplary embodiment of the invention.
  • Figure 14 shows an optical micrograph of the product 14000, including a plurality of OE devices 1400. Like reference signs denote like features, description of which is not repeated for brevity. Particularly, Figure 14 shows a gate interconnect metal track 1470A crossing a source and drain metal electrode track 1420A with the SU8 passivation layer 1460 (spun from Cyrene and photopatterned, described previously) isolating the tracks from each other. Metal 1470A (50 nm Au) was sputtered on top of the SU8 and patterned using photolithography and wet etching as for the source and drain metal electrode track metal 1420A.
  • Metal 1470A 50 nm Au
  • the passivation layer 1460 also serves as an interlayer dielectric so that metal tracks 1420A and 1470A may be routed in the circuit on different layers without short circuiting, for example.
  • Example 5 relates to measurements of surface tension of mixtures of solvents, particularly a first mixure of IPA and Cyrene and to a second mixture of hexanol and Cyrene.
  • Example 5 also relates to OTFT using the second mixture of hexanol and Cyrene. Measurement of surface tension - drop shape analysis
  • Drop shape analysis was performed on single solvents and solvent mixtures comprising Cyrene to determine their surface free tension.
  • Pendant drop analysis was carried out using a Kruss DSA30S. Measurements were conducted using a syringe of solvent to form a drop at the end of a blunt needle suspended near to a cuvette filled with the test solvent. This was done to reduce the effect of evaporation on the resulting surface tension values.
  • a drop was formed at the end of the needle, 10-30 pL in volume depending on the solvent under test, close to the point where it would drop off the end of the needle. The drop was then increased in size in 0.1 pL increments until it dropped from the end of the needle.
  • Table 15 Surface free tension values of Cyrene/IPA solvent mixtures.
  • Table 16 Surface free tension values of Cyrene/hexanol solvent mixtures.
  • OTFT devices were made using the process as described in Example 1 but with the following changes.
  • the equipment used to dry etch pattern the OSC and dielectric layers was changed to an Aurion Gen2 RIE system with process pressure of 0.07 hPa, 0 2 gas at 150 seem, power 2250 W, temperature 21 °C, etch time 25s.
  • a passivation layer formulation was prepared using EPON SU-8 dissolved at 12.5% by weight solids SU8 in mixed solvent of Cyrene/hexanol (9:1 by weight).
  • a Triarylsulfonium hexafluoroantimonate photoinitiator (50% solution by weight in propylene carbonate) was added at 10% by weight of the SU-8 polymer.
  • the passivation layer formulation was spun at 500rpm 10s followed by 1250rpm for 30s, baked 2 min at 95 °C to give a layer thickness of 850nm.
  • the passivation layer was exposed through a photomask with 100 mJ/cm 2 (i-line) UV light using an EVG 6200 mask aligner in hard contact mode.
  • Post-baking and development was as in example 1 and the features produced by the patterning were well defined as can be seen in Figure 15.
  • An interconnect metal (50nm Au) was then deposited and patterned as described in Example 4.
  • the devices were tested electrically and the results shown in Table 17.
  • Figure 15 shows an optical micrograph of a product 15000 according to an exemplary embodiment of the invention. Particularly, Figure 15 shows a photograph of 4, 6, 8, and 10 micron CD bars (1510, 1520, 1530 and 1540 respectively) for the passivation layer made using a mixed solvent system of Cyrene and hexanol (9: 1 ).
  • Table 17 OTFT results for devices processed with an SU8 passivation layer spun from Cyrene/hexanol mixed solvent system
  • the mixed solvent system of Cyrene and hexanol can be used as a coating solvent in a passivation layer.
  • Other solvent systems such as pentanol and butanol were also miscible with Cyrene so could be suitable for a mixed solvent system.
  • Example 6 (example of polyvinylphenol used as passivation layer)
  • Example 6 relates to use of poly (4-vinvlphenol) (PVP) as a passivation layer.
  • PVP poly (4-vinvlphenol)
  • an OTFT device was processed as in Example 1 except that the dry etch patterning equipment and process used was the same as in Example 5 and the passivation layer used was poly (4-vinylphenol) (PVP).
  • the PVP passivation layer formulation was formulated at 10% by weight in Cyrene with hydroxymethyl benzoguanamine (HMBG) as crosslinker (2% by weight in cyrene).
  • HMBG hydroxymethyl benzoguanamine
  • the formulation was spun at 2500 rpm for 30 s on top of a dry etch patterned OTFT to form a passivation layer.
  • the PVP layer was measured at 1 .5 microns thickness using a stylus profilometer.
  • the substrate was baked at 95°C for 2 min on a hot-plate and then further baked for crosslinking for 3 hours at 130 C in a vacuum oven.
  • the devices were electrically tested after the dry etching and after the PVP passivation layer process.
  • Table 18 electrical test data after OTFT dry etch patterning process.
  • Table 19 electrical test data after application of passivation layer (PVP in cyrene solvent).
  • the invention provides a formulation for providing passivation and/or photopatterning layers for use in fabrication of organic electronic devices that may be provided, for example directly, on organic layers, such as OSC layers and/or OGI layers and/or a stack comprising one or more of these layers, without adversely affecting the organic layers.
  • the formulation comprises a solvent comprising levoglucosenone or dihydrolevoglucosenone or a derivative thereof.
  • the invention provides a method of fabrication of organic electronic devices, using such a formulation, having reduced complexity and/or cost.
  • the invention provides an organic electronic device, including a layer provided by such a formulation, that has improved long-term stability.
  • the square pad and frame corresponding with the square aperture may be modified to be a circular pad and frame to correspond with a circular aperture.
  • the gap may be provided within the aperture rather than outside and adjacent to the aperture.

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Abstract

A flowable formulation, for depositing a passivation layer (360) on an organic electronic (OE) device comprising an organic layer, is described. The organic layer is selected from an organic semiconductor (OSC) layer (330) and an organic gate insulator (OGI) layer (340). The formulation comprises a passivation material and a solvent. The solvent comprises levoglucosenone or dihydrolevoglucosenone or a derivative thereof. A method of fabricating an OE device (300) is also described. An OE device (300) is further described.

Description

Formulation and layer
Field The present invention relates to formulations for providing layers, such as passivation layers and/or photopatterning layers, for use in fabrication of organic electronic devices, to methods of fabrication of organic electronic devices using such formulations and to organic electronic devices including layers provided by such formulations. Background to the Invention
Organic electronic (OE) devices include, for example, organic field effect transistors (OFET) for use in backplanes of display devices or logic capable circuits, and organic photovoltaic (OPV) devices. A conventional top gate OFET comprises source and drain electrodes, a semiconducting layer made of an organic semiconductor (OSC) material, a gate insulator layer made of a dielectric material (also known as a dielectric or a gate dielectric) such as an organic gate insulator (OGI), a gate electrode, and typically a passivation layer on top of the OGI layer to protect the OSC and OGI layer against environmental influence and/or damage from subsequent device fabricating steps. Similarly, a conventional bottom gate OFET comprises a gate electrode, a gate insulator layer made of a dielectric material such as an organic gate insulator (OGI), source and drain electrodes, a semiconducting layer made of an organic semiconductor (OSC) material, and typically a passivation layer on top of the OSC layer to protect the OSC and OGI layers against environmental influence and/or damage from subsequent device fabricating steps. In both top and bottom gate OFETs, the passivation layer may also serve as an interlayer dielectric so that metal tracks may be routed in the circuit on different layers of these OE devices without short circuiting, for example.
Conventional fabrication techniques of these OE devices are based on processes including thermal evaporation, chemical or physical vapour deposition, solution coating or printing and photolithography, for example. Solution processable passivation layers are preferred, particularly for OFETs. Solution processable passivation materials (SPPMs) allow use of solution-based deposition methods, for example spin-coating or larger area printing methods including flexo, gravure and slot-die coating, during fabrication. Adhesion of the passivation materials to underlying layers may be a primary conventional requirement for such solution-based passivation materials. In addition, orthogonality of solvents used in the solution-based passivation materials, particularly to organic layers such as the OSC layers and/or the OGI layers, is also required. Generally, the orthogonality of the solvents may be understood as chemical orthogonality. For example, an orthogonal solvent is a solvent which, when used in the provision of a layer of a material dissolved and/or dispersed therein on a previously provided layer, does not adversely affect the previously provided layer. Thus, orthogonal solvents may be considered as suitable (also known as compatible) solvents, in that they do not adversely affect organic layers such as the OSC layers and/or the OGI layers. In contrast, non-orthogonal (also known as unsuitable or incompatible) solvents may dissolve, damage, destroy or impact a long-term stability of the previously provided layer. However, while the orthogonal solvents may be compatible with the organic layers such as the OSC layers and/or the OGI layers, dissolution and/or dispersion of the passivation materials therein may be problematic. Figure 1 shows schematically a method of fabrication of an OE device, specifically a top gate OFET, using conventional solution processable passivation materials. Typically, such a method of fabrication may be achieved practically by photolithographic processing, as known to the person skilled in the art.
At S101 , a substrate 1 10 is provided. The substrate 1 10 may comprise glass, metal, a polymer or an intergrated circuit (IC), for example. The substrate 1 10 may include an optional buffer layer provided on the surface of the substrate 1 10. The buffer layer may also be known as a planarization layer, provided by a crosslinkable polymer that may improve surface uniformity and/or homogeneity by smoothing imperfections in the surface of the substrate and may provide a chemically inert surface upon which the OE device is fabricated.
At S102, source and drain electrodes 120 are provided on the surface of the substrate 1 10, for example by sputtering and photolithography (using mask 1 ). The source and the drain electrodes 120 are typically a metal, for example silver or gold or alloys thereof, or a non-metal. The source and the drain electrodes 120 may be treated with a thiol solution, to adjust work functions of the source and the drain electrodes 120, as known in the art. In this way, injection of charges into an overlaying OSC layer may be improved. Excess thiol solution may be washed away, with thiol binding only to the source and the drain electrodes 120.
At S103, an OSC layer 130 is first provided over the source and the drain electrodes 120 and the exposed surface of the substrate 1 10, for example by spin coating or printing. The OSC layer 130 typically has a thickness of 30 nm. An OGI layer 140 is subsequently provided over the OSC layer 130, for example by spin coating or printing. The OGI layer 140 typically has a thickness of 300 nm. A metal layer 150, for example silver or gold or alloys thereof, is subsequently deposited on the OGI layer 140, for example by evaporation. A photoresist (not shown) is subsequently patterned (e.g. by photolithography) on the metal layer 150 and portions of the metal layer 150 exposed through the patterned photoresist are removed by wet etching. The patterned metal layer 150 provides a gate, such as a thin film transistor (TFT) gate. The patterned metal layer 150 also provides a hardmask (mask 2) against reactive ion etching (RIE) (also known as dry etching, for example using 02 and/or Ar), thereby masking the underlying OGI layer 140, the OSC layer 130 and the source and the drain electrodes 120. Subsequently, RIE removes portions of the OGI layer 140 and the OSC layer 130, that are not masked by the patterned metal layer 150. In this way, a stack 100 comprising the patterned metal layer 150, OGI layer 140, the OSC layer 130 and the source and the drain electrodes 120 is provided on the substrate 1 10. It should be understood that the stack 100 generally describes a multilayered structure and thus may comprise more or fewer and/or different layers. For example, the stack 100 may comprise those layers at an intermediary stage of fabrication of the OE device. For example, the stack 100 may comprise all layers of the completed OE device. That is, layers included in the stack 100 may change during fabrication, by addition and/or by removal of layers. Sides 141 of the OGI layer 140 and sides 131 of the OSC layer 130 may be thus exposed, for example by the RIE, and may be adversely affected by unsuitable solvents. Further, inter-layer interfaces may also be exposed, for example between the substrate 110 and the OSC layer 130, between the OSC layer 130 and the OGI layer 140 and/or between the OGI layer 140 and the metal layer 150. Other surfaces of the OGI layer 140 and/or the OSC layer 130 may be additionally and/or alternatively exposed.
At S104, a conventional first passivation layer 180 is provided over the stack 100 and the exposed surface of the substrate 1 10, for example, by coating with a first formulation comprising an aqueous solution of a water-soluble polymer formulation such as polyvinyl alcohol (PVA) plus Ammonium Dichromate (ADC) and subsequently UV crosslinking the water-soluble polymer (i.e. the PVA+ADC). The first passivation layer 180 typically has a thickness of 100 nm. Water is generally considered an orthogonal solvent, being at least sufficiently compatible with the OGI layer 140 and/or the OSC layer 130. However, the first passivation layer 180 provided using crosslinked PVA may not be suitable for subsequent fabrication steps and/or may not be suitable for providing environmental, chemical and/or physical protection of the fabricated OE device. Hence, a second passivation layer 190 is additionally required, as described below.
At S105, a positive photoresist mask 181 (mask 3) is provided over the first passivation layer 180.
At S106, a first hole 185 (also known as a via) is formed through the first passivation layer 180 to the patterned metal layer 150, by RIE through the positive photoresist mask 181 , thereby exposing at least a part of the surface of the metal layer 150. At S107, residual photoresist mask 181 is removed.
At S108, the second passivation layer 190 is provided over the first passivation layer 180 and exposed potions of the stack, such as the patterned metal layer 150 exposed through the hole formed through the first passivation layer 180. The second passivation layer 190 is provided, for example, by coating with a second formulation, such as a solution of another crosslinkable polymer, for example SU-8 available from MicroChem Corp., Westborough, MA (USA), and crosslinking the polymer. SU-8 comprises a bisphenol A novolac epoxy dissolved in an organic solvent such as cyclopentanone, gamma-butyrolactone (GBL) or propylene glycol monoethyl ether acetate (PGMEA). SU-8 may include also up to 10 wt.% of a photoacid generator, for example a mixed triarylsulfonium hexafluoroantimonate salt. The second passivation layer 190 typically has a thickness of 300 nm and may provide the main passivation layer for the OE device. The second passivation layer 190, comprising the crosslinked polymer, thus overlays the first passivation layer 180, comprising the crosslinked PVA. The second passivation layer 190 provides the robustness required for providing environmental, chemical and/or physical protection of the fabricated OE device. The organic solvents used in the second formulation are generally non-orthogonal solvents, being incompatible with the organic layers, such as the OGI layer 140 and/or the OSC layer 130, of the stack 100. However, robust crosslinkable polymers, such as in SU-8, may not be soluble and/or dispersible in orthogonal solvents, such as water used in the first formulation, and thus must be provided in these non-orthogonal solvents, such as cyclopentanone, GBL or PGMEA. Hence, the first passivation layer 180 acts as a protection layer, protecting the organic layers, such as the OGI layer 140 and/or the OSC layer 130, of the stack 100 from the non-orthogonal solvents included in the second formulation.
A second hole 195 or via, aligned with the first hole formed through the first passivation layer 180, is subsequently formed through the second passivation layer 190 to the patterned metal layer 150, thereby exposing at least a part of the surface of the metal layer 150, as similarly described with at steps S105 to S107 with respect to the first passivation layer 190. Another positive photoresist mask (not shown) (mask 4) is provided over the second passivation layer 190 and the hole or via is formed therethrough by RIE. Residual photoresist mask is subsequently removed.
At S109, a metal gate interconnect 170 is provided through the second hole to the patterned metal layer 150, for example, by sputtering, masking (mask 5) and etching.
In this way, the OE device may be provided, having a double passivation layer comprising the first passivation layer 180 and the second passivation layer 190.
However, provision of this double passivation layer comprising the first passivation layer 180 and the second passivation layer 190 increase OE device fabrication complexity and/or cost. Furthermore, water-soluble polymers, such as PVA, are hygroscopic and water, such as absorbed moisture, in the first passivation layer 180 may be detrimental to long-term stability of OE devices. In addition, according to this conventional method of fabrication of the OE device, five masks (mask 1 - mask 5) are required.
Thus, there is a need to provide improve fabrication of OE devices, for example, with respect to provision of passivation layers and/or photopatterning layers.
Summary of the Invention
It is one aim of the present invention, amongst others, to provide formulations for providing passivation and/or photopatterning layers for use in fabrication of organic electronic devices that may be provided, for example directly, on organic layers, such as OSC layers and/or OGI layers and/or a stack comprising one or more of these layers. It is a further aim of the invention to provide methods of fabrication of organic electronic devices, using such formulations, having reduced complexity and/or cost. It is a further aim of the invention to provide organic electronic devices, including layers provided by such formulations, that have improved long-term stability. A first aspect of the invention provides a flowable formulation for depositing a passivation layer on an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer, wherein the formulation comprises a passivation material and a solvent;
wherein the solvent comprises levoglucosenone or dihydrolevoglucosenone or a derivative thereof.
A second aspect of the invention provides a method of fabricating an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer, wherein the method comprises:
providing a passivation layer on at least a part of the organic layer by depositing a formulation according to the first aspect thereon and removing the solvent.
A third aspect of the invention provides an organic electronic (OE) device comprising an organic layer and a passivation layer directly thereon, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer and wherein the passivation layer comprises a cross-linked product of a cross-linkable composition provided by the first aspect.
A fourth aspect of the invention provides a product comprising an organic electronic (OE) device fabricated according to the second aspect and/or an OE device according to the third aspect.
A fifth aspect of the invention provides a flowable formulation comprising a photopatterning material and a solvent;
wherein the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof.
A sixth aspect of the invention provides use of a solvent comprising levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof in a method of fabricating an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer.
Detailed Description of the Invention
According to the present invention there are provided formulations, methods and organic electronic (OE) device as set out in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description that follows.
Throughout this specification, the term "comprising" or "comprises" means including the component(s) specified but not to the exclusion of the presence of other components. The term "consisting essentially of or "consists essentially of means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention.
The term "consisting of" or "consists of" means including the components specified but excluding other components.
Whenever appropriate, depending upon the context, the use of the term "comprises" or "comprising" may also be taken to include the meaning "consists essentially of or "consisting essentially of, and also may also be taken to include the meaning "consists of or "consisting of. The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each aspect or exemplary embodiment of the invention, as set out herein are also applicable to all other aspects or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each aspect or exemplary embodiment of the invention as interchangeable and combinable between different aspects and exemplary embodiments.
Development of SPPMs is challenged by conflicting requirements, as outlined above. The SPPMs and/or formulations should preferably be compatible with (i.e. orthogonal to) organic layers, such as OSC and/or OGI layers, and OE device architectures. However, the organic layers may be soluble in organic solvents and hence exposure of these organic layers to such solvents should be avoided. In addition, inter-layer adhesion, such as between overlaying OSC and/or OGI layers, is important for functioning of OE devices. Since different organic layers, such as the OSC and/or the OGI layers, typically have different surface energies, solvents that may not dissolve a particular layer may penetrate via inter-layer interfaces and thereby also degrade or destroy functioning of OE devices.
Furthermore, the SPPMs should preferably provide environmental, physical and/or chemical resistance, for example against materials and conditions applied during subsequent fabrication steps during OE device manufacture, for example photolithography. Typically, photolithography incudes one or more of the following processing steps, which may involve chemical and/or physical exposure of the underlying layers: deposition of photo resist resin, typically in an organic solvent; UV exposure; development of the photo resist, typically using bases; etching of metal, typically using aggressive acids and redox reactions; and/or removal of the photo resist, typically using aggressive organic solvents.
Hence, the deposited passivation material should preferably withstand organic solvents and/or aqueous solutions. However, as a conflicting requirement, deposition of the passivation material generally requires the passivation material to preferably be soluble and/or dispersible in an organic solvent or an aqueous solution. Hence, the passivation material may be cross-linked after deposition, for example, to meet these conflicting requirements. The deposited passivation layer should preferably exhibit at least one of mechanical flexibility, good scratch resistance, thermal stability, optical transparency, uniformity, pinhole free, good adhesion to other layers, good barrier properties with respect to water and/or oxygen, non-hygroscopic and good dielectric breakdown strength.
Formulation
The first aspect of the invention provides a flowable formulation for depositing a passivation layer on an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer, wherein the formulation comprises a passivation material and a solvent;
wherein the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof. More generally, an aspect of the invention provides a flowable formulation comprising a passivation material and a solvent;
wherein the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof. For example, the flowable formulation according to the first aspect of the invention may also be suitable for providing layers in other devices, such as microelectromechanical systems (MEMs), microfluidic devices, and/or conventional (for example, non-organic thin-film transistor (OTFT)) electronics.
According to an aspect of the invention, there is also provided a flowable formulation comprising a photopatterning material and a solvent;
wherein the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof.
In this way, direct photopatterning on an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer, may be provided. In this way, RIE etching may be avoided, thereby reducing cost and/or complexity of fabrication of OE devices, for example.
According to an aspect of the invention, there is also provided a flowable formulation comprising a cross-linkable composition and a solvent;
wherein the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof.
Generally, the flowable formulation may be provided for spin coating and/or printing directly and/or following addition of further solvent. Generally, flowable formulations, for spin coating for example, may have dynamic or absolute viscosities in a range of from 1 to 10,000 centipoise or more, as known to the person skilled in the art. In one example a dynamic viscosity of the flowable formulation is in a range of from 1 to 10,000 centipoise, preferably 1 to 1000 centipoise, more preferably 1 to 20 centipoise. A dynamic viscosity of the flowable formulation may depend, at least in part, on an amount of the solvent in the flowable formulation, such that an increased amount of the solvent may decrease the dynamic viscosity.
In one example, the solvent exhibits low wettability of the organic layer, such that a contact angle Θ is in a range from 90° to 180°. In this way, damage, such as delamination, of the organic layer may be prevented and/or avoided. Generally, the contact angle Θ is the angle at which a liquid-vapour interface meets a solid-liquid interface. The contact angle Θ is determined by a result between adhesive and cohesive forces. As a tendency of a drop to spread out over a flat, solid surface increases, the contact angle Θ decreases. Thus, the contact angle Θ provides an inverse measure of wettability. A contact angle less than 90° (low contact angle) usually indicates that wetting of the surface is very favourable, and the fluid will spread over a large area of the surface. Contact angles greater than 90° (high contact angle) generally means that wetting of the surface is unfavourable, so the fluid will minimize contact with the surface and form a compact liquid droplet. For water, a wettable surface may also be termed hydrophilic and a nonwettable surface hydrophobic. Superhydrophobic surfaces have contact angles greater than 150°, showing almost no contact between the liquid drop and the surface. For nonwater liquids, a term lyophilic may be used for low contact angle conditions and lyophobic may be used when higher contact angles result. Similarly, terms omniphilic and omniphobic may be used for polar and apolar liquids.
Wettability may relate to a surface tension of the solvent. For example, a surface tension of dihydrolevoglucosenone (neat) is 33.6 mN/m (DATA SHEET: CYRENE™ Circa, Australia) c.f. 47.36 ± 0.56 mN/m (Table 14). For example, a surface tension of dihydrolevoglucosenone (1 wt.% aqueous solution) is 72.5 mN/m (DATA SHEET: CYRENE™ Circa, Australia). Water has a surface tension of 72.8 mN/m. In contrast, cyclopentanone has a surface tension of 33.4mN/m, GBL has a surface tension of 40.4 mN/m, and PGMEA has a surface tension of 26.9mN/m. In one example, the solvent, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof has a surface tension of at least 30 mN/m, at least 35 mN/m, at least 40 mN/m, at least 45 mN/m, at least 50 mN/m, at least 55 mN/m, at least 60 mN/m, at least 65 mN/m or at least 70 mN/m. Preferably, the solvent, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof has a surface tension of at least 45 mN/m. More preferably, the solvent, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof has a surface tension of at least 70 mN/m.
In one example, the solvent, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof has a surface tension of at most 50 mN/m, at most 55 mN/m, at most 60 mN/m, at most 65 mN/m, at most 70 mN/m, at most 75 mN/m, at most 80 mN/m, at most 85 mN/m, at most 90 mN/m, at most 95 mN/m, at most 100 mN/m or at most 105 mN/m. Preferably, the solvent, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof has a surface tension of at most 100 mN/m. More preferably, the solvent, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof has a surface tension of at most 85 mIM/m.
Levoglucosenone or dihydrolevoglucosenone or a derivative thereof
Levoglucosenone, of Formula (I), is a bicyclic a, β-unsaturated ketone containing a protected aldehyde. The highly dehydrated sugar is derived from cellulose and hence provides a bio-based solvent, which is attractive as a 'green' solvent. Levoglucosenone ((1 S,5R)-6,8-dioxabicyclo[3.2.1]oct-2-en-4-one) has a molecular formula: C6H603 and InChl Key HITOXZPZGPXYHY-UJURSFKZSA-N.
Figure imgf000010_0001
Formula (I)
A dipolar structure of levoglucosenone and/or derivatives thereof suggests that levoglucosenone and/or derivatives thereof may behave as dipolar aprotic solvents. Specifically, levoglucosenone and/or derivatives thereof have been investigated as replacements for solvents such as N,N- dimethylformamide, Ν,Ν-dimethylacetamide and N-methylpyrolidinone, which are widely used in organic synthesis and chemical manufacture but have undesirable toxicity and environmental profiles. Based on their Hansen solubility parameters, as described below in more detail, levoglucosenone and/or derivatives thereof may also be expected to exhibit similar properties to other types of solvents which find application in microelectronic fabrication processes, such as cyclopentanone, gamma-butyrolactone (GBL) or propylene glycol monoethyl ether acetate (PGMEA). For example, they would be expected to be useful solvents for epoxy based photoresist materials, for example SU-8 as described above in relation to the second passivation layer. Based on these Hansen solubility parameters, it would also be expected that levoglucoseneone and/or derivatives thereof would be similar to the above solvents in terms of solvency properties, that is to say that they would be non-orthogonal to the OSC and/or OGI and/or the partly assembled and exposed 'stack' of a OTFT device. These properties would severely limit the usability of levoglucosenone and/or derivatives thereof in the fabrication of OTFTs. Surprisingly, the inventors have determined that levoglucosenone and/or derivatives thereof may also be orthogonal solvents, unlike the conventional organic solvents, such as cyclopentanone, GBL or PGMEA, as described above. References herein to a derivative mean a derivative of levoglucosenone or a derivative of dihydrolevoglucosenone. Generally, the derivative of levoglucosenone, for example dihydrolevoglucosenone, may be derived from levoglucosenone. That is, the derivative of levoglucosenone may be synthesized from levoglucosenone, directly and/or indirectly. In other words, levoglucosenone may be a starting material and/or an intermediary material in a synthesis of the derivative of levoglucosenone. For example, dihydrolevoglucosenone is a derivative of levoglucosenone.
Dihydrolevoglucosenone is derived from levoglucosenone by hydrogenation of levoglucosenone, for example over supported palladium catalysts. Commercially, dihydrolevoglucosenone is available as Cyrene (RTM) from Circa Group Pty Ltd (Australia).
Dihydrolevoglucosenone, of Formula (II), is a chiral dipolar aprotic solvent. Dihydrolevoglucosenone ((1 S,5R)-6,8-Dioxabicyclo[3.2.1]octan-4-one) has a molecular formula: ϋ6Η803 and InChl Key WHIRALQRTSITMI-UJURSFKZSA-N.
Figure imgf000011_0001
Formula (II)
A dipolar structure of dihydrolevoglucosenone suggests that dihydrolevoglucosenone may behave as a dipolar aprotic solvent and thus may substitute for certain conventional organic dipolar aprotic solvents. Typically, dihydrolevoglucosenone is considered to be a substitute for N-Methyl-2-pyrrolidone (NMP), being also similar in terms of hydrogen bonding capacity. Particularly, the Kamlet-Abboud-Taft parameters indicate that dihydrolevoglucosenone is aprotic with a similar π* value (corresponding to dipolarity) to those of highly dipolar aprotic solvents, but with a slightly lower β value which is an indicator of hydrogen bond accepting ability.
The inventors have determined that levoglucosenone, dihydrolevoglucosenone and/or a derivative may substitute for conventional organic solvents, such as cyclopentanone, GBL or PGMEA, in SU-8 for example, as described above in relation to the second passivation layer.
Surprisingly, the inventors have determined that levoglucosenone, dihydrolevoglucosenone and/or a derivative thereof may also be orthogonal solvents, unlike the conventional organic solvents, such as cyclopentanone, GBL or PGMEA, as described above. That is, the inventors have determined that levoglucosenone or dihydrolevoglucosenone or a derivative thereof may be used as solvents for solutions comprising robust crosslinkable polymers dissolved and/or dispersed therein and that these solutions may be provided, for example directly, on organic layers, such as an OSC layer and/or an OGI layer and/or a stack comprising one or more of these layers.
Preferably, the formulation may be provided directly on the OGI layer, which may be part of the stack, for example. Alternatively, the formulation may be preferably provided directly on a protection layer, for example a fluoropolymer protection layer, on the OSC layer. Typically, such protection layers are provided on OSC layers for patterning, such as by dry etching as described previously.
In this way, only a single passivation layer may be required, in contrast with the conventional double passivation layer, as described above. That is, the single passivation layer provided by the first formulation replaces the first passivation layer and the second passivation layer, as conventionally provided.
In this way, OE device fabrication complexity and/or cost may be reduced, since fewer steps and materials are required. Furthermore, since use of water-soluble polymers, such as PVA, is avoided, long-term stability of OE devices may be improved.
In one example, the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or the derivative thereof in an amount of at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97.5% or at least 99%, wherein the amount of levoglucosenone and/or dihydrolevoglucosenone and/or the derivative thereof is a percentage by weight of the total amount of solvent in the formulation.
In one example, the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or the derivative thereof in an amount of at most 25%, at most 30%, at most 35%, at most 40%, at most 45%, at most 50%, at most 55%, at most 60%, at most 65%, at most 70%, at most 75%, at most 80%, at most 85%, at most 90%, at most 95%, at most 97.5%, at most 99% or at most 100%, wherein the amount of levoglucosenone and/or dihydrolevoglucosenone and/or the derivative thereof is a percentage by weight of the total amount of solvent in the formulation.
In one example, the solvent comprises a mixture of levoglucosenone and/or dihydrolevoglucosenone and/or one or more derivatives thereof.
In one example, the solvent comprises a cosolvent, for example organic and/or aqueous solvents. Example cosolvents may include cyclopentanone, GBL and PG EA, propylene carbonate, diethylene glycol, isopropyl alcohol (IPA), 2-propanol and/or ethanol. In one example, the solvent comprises the cosolvent in an amount of at most 50%, at most 45%, at most 40%, at most 35%, at most 30%, at most 25%, at most 20%, at most 15%, at most 10%, at most 5%, at most 2.5% or at most 1 %, wherein the amount of the cosolvent is a percentage by weight of the total amount of solvent in the formulation. In one example, the solvent comprises the cosolvent in an amount of at least 50%, at least 45%, at least 40%, at least 35%, at least 30%, at least 25%, at least 20%, at least 15%, at least 10%, at least 5%, at least 2.5% or at least 1 %, wherein the amount of the cosolvent is a percentage by weight of the total amount of solvent in the formulation.
In one example, the solvent comprises a plurality of cosolvents. In one example, the solvent comprises the plurality of cosolvents in an amount of at most 50%, at most 45%, at most 40%, at most 35%, at most 30%, at most 25%, at most 20%, at most 15%, at most 10%, at most 5%, at most 2.5% or at most 1 %, wherein the amount of the plurality of cosolvents is a percentage by weight of the total amount of solvent in the formulation. In one example, the solvent comprises the plurality of cosolvents in an amount of at least 50%, at least 45%, at least 40%, at least 35%, at least 30%, at least 25%, at least 20%, at least 15%, at least 10%, at least 5%, at least 2.5% or at least 1 %, wherein the amount of the plurality of cosolvents is a percentage by weight of the total amount of solvent in the formulation.
In one example, the formulation comprises the solvent in an amount of at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97.5% or at least 99%, wherein the amount of solvent is a percentage by weight of the formulation.
In one example, the formulation comprises the solvent in an amount of at most 25%, at most 30%, at most 35%, at most 40%, at most 45%, at most 50%, at most 55%, at most 60%, at most 65%, at most 70%, at most 75%, at most 80%, at most 85%, at most 90%, at most 95%, at most 97.5% or at most 99%, wherein the amount of solvent is a percentage by weight of the formulation.
In one example, the formulation comprises the passivation material in an amount of at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97.5% or at least 99%, wherein the amount of the passivation material is a percentage by weight of the formulation.
In one example, the formulation comprises the passivation material in an amount of at most 80%, at most 75%, at most 70%, at most 65%, at most 60%, at most 55%, at most 50%, at most 45%, at most 40%, at most 35%, at most 30%, at most 25%, at most 20%, at most 15%, at most 10%, at most 5%, at most 2.5% or at most 1 %, wherein the amount of the passivation material is a percentage by weight of the formulation. Table S1 (presented as Tables S1a - S1 p for convenience) details structures and certain properties of levoglucosenone, dihydrolevoglucosenone and derivatives thereof, as reproduced from Table S1 of A. Alves Costa Pacheco, J. Sherwood, A. Zhenova, C. R. McElroy, A. J. Hunt, H. L. Parker, T. J. Farmer, A. Constantinou, M. De bruyn, A. C. Whitwood, W. Raverty, J. H. Clark, Intelligent Approach to Solvent Substitution: The Identification of a New Class of Levoglucosenone Derivatives, ChemSusChem 2016, 9, 3503 and the supporting information relating to this publication, the subject matter of which is incorporated by reference herein in its entirety. For brevity, references to this publication and/or the supporting information relating to this publication are indicated herein as Pacheco et al. (2016).
In Table S1 , levoglucosenone, dihydrolevoglucosenone and derivatives thereof are identified by a unique number (#) and provided with codes based on their respective documentary source references. The codes are generally in the form Ά-1 ', in which the characters before the dash indicate the respective documentary source references (see Table S2) and the characters after the dash are the compound numbering used in the respective documentary source references reference. For this reason, abbreviations, letters, numbers and Roman numerals are possible. A common format has not been used to help the finding of compounds in their respective references should the reader wish to do so. Where the compound code is followed by (m), this is an original modification to the referenced structure. Also, (m2) signifies a second structural modification, (m3) a third, and so on. Some compounds have more than one code because they appear in multiple references, hence each compound is also individually numbered in Table S1. Numbering of compounds is in order of appearance, with the numbering from the main article also given in brackets (where applicable).
Table S2 details the respective documentary source references (citations) for levoglucosenone, dihydrolevoglucosenone and derivatives thereof as detailed in Table S1 , as reproduced from Table S2 of Pacheco et at. (2016). Synthesis and/or sources of levoglucosenone, dihydrolevoglucosenone and derivatives thereof are provided by the respective documentary source references.
Table S1 a. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000015_0001
Table S1 b. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000016_0001
Table S1 c. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000017_0001
Table S1 d. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000018_0001
Table S1e. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000019_0001
Table S1f. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000020_0001
Table S1 g. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000021_0001
Table S1 h. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000022_0001
Table S1 i. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000023_0001
Table S1j. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000024_0001
Table S1 k. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000025_0001
Table S1 I. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000026_0001
Table S1 m. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000027_0001
Table S1 n. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000028_0001
Table S1 o. Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000029_0001
Table S1 . Levoglucosenone, dihydrolevoglucosenone and derivatives thereof.
Figure imgf000030_0001
Table S2a. Documentary source references
Documentary Citation
source
reference
AA A. L. Flourat, A. A. M. Peru, A. R. S. Teixeira, F. Brunissen and F. Allais, Green Chem.,
2015, 17, 404.
AB B. T. Sharipov, O. Yu. Krasnoslobodtseva, L. V. Spirikhin, and F. A. Valeev, Russian
Journal of Organic Chemistry, 2010, 46, 129.
AC B. T. Sharipov, O. Yu. Krasnoslobodtseva, L. V. Spirikhin, and F. A. Valeev, Russian
Journal of Organic Chemistry, 2010, 46, 226.
AD R. A. Novikov, R. R. Rafikov, E. V. Shulishov, L. D. Konyushkin, V. V. Semenov and Yu.
V. Tomilov, Russian Chemical Bulletin International Edition, 2009, 58, 327.
AE I. P. Tsypysheva, F. A. Valeev, E. V. Vasileva, L. V. Spirikhin and G. A. Tolstikov, Russian
Chemical Bulletin International Edition, 2000, 49, 1237.
AF F. A. Valeev, L. Kh. Kalimullina, Sh. M. Salikhov, O. V. Shitikova, I. P. Tsypysheva and
M. G. Safarov, Chemistry of Natural Compounds, 2004, 40, 521.
AG R. R. Rafikov, R. A. Novikov, E. V. Shulishov and Yu. V. Tomilov, Russian Chemical
Bulletin International Edition, 2009, 58, 2449.
AH R. A. Novikov, R. R. Rafikov, E. V. Shulishov and Yu. V. Tomilov, Russian Chemical
Bulletin International Edition, 2010, 59, 1930.
Al A. V. Samet, A. M. Shestopalov, D. N. Lutov, L. A. Rodinovskaya, A. A. Shestopalov and
V. V. Semenov, Tetrahedron: Asymmetry, 2007, 18, 1986.
AJ E. A. Yatsynich, D. V. Petrov, F. A. Valeev and V. A. Dokichev, Chemistry of Natural
Compounds, 2003, 39, 337.
AK T. Nishikawa, M. Asai, N. Ohyabu, Y. Fukuda and M. Isobe, Tetrahedron, 2001 , 57,
3875.
AL L. L Vasiljeva and K. K. Pivnitsky, Russian Chemical Bulletin, 1999, 48, 157.
AM F. A. Valeev, E. V. Gorobets, I. P. Tsypysheva, G. Sh. Singizova, L. Kh. Kalimullina, M.
Safarov, O. V. Shitikova and M. S. Miftakhov, Chemistry of Natural Compounds, 2003, 39, 563.
AN Valery K. Brel, Aleksandr V. Samet, Leonid D. Konyushkin, Adam I. Stash, Vitaly K.
Belsky and Victor V. Semenov, Mendeleev Commun., 2015, 25, 44.
AO A. M. Sarotti, Rol. A. Spanevello, A. G. Suarez, G. A. Echeverria and O. E. Piro, Organic
Letters, 2012, 14, 2556.
AP A. N. Davydova, A. A. Pershin, B. T, Sharipov and F. A. Valeev, Mendeleev Commun.,
2015, 25, 271.
AQ A. R. Tagirov, I. M. Biktagirov, Yu. S. Galimova, L. Kh. Faizullina, Sh. M. Salikhov and F.
A. Valeev, Russian Journal of Organic Chemistry, 2015, 51 , 569.
AR I. M. Biktagirov, L. Kh. Faizullina, Sh. M. Salikhov, M. M. Iskakova, . G. Safarov, F. Z.
Galin and F. A. Valeev, Russian Journal of Organic Chemistry, 2015, 51 , 576.
AS I. M. Biktagirov, L. Kh. Faizullina, Sh. M. Salikhov, M. G. Safarov, and F. A. Valeev,
Russian Journal of Organic Chemistry, 2014, 50, 1317.
AT A. M. Sarotti, Carbohydrate Research, 2014, 390, 76.
AU Z. J. Witczak, P. Kaplon and M. Kolodziej, Journal of Carbohydrate Chemistry, 2002, 21 ,
143. Table S2b. Documentary source references
Documentary Citation
source
reference
AV M. . Iskakova, I. M. Biktagirov, L. Kh. Faizullina, Sh. M. Salikhov, M. G. Safarov and F.
A. Valeev, Russian Journal of Organic Chemistry, 2014, 50, 105.
AW B. T. Sharipov, A. N. Pilipenko and F. A. Valeev, Russian Journal of Organic Chemistry,
2014, 50, 1628.
AX Yu. A. Khalilova, L. V. Spirikhin, Sh. M. Salikhov and F. A. Valeev, Russian Journal of
Organic Chemistry, 2014, 50, 117.
AY A. N. Pilipenko, B. T. Sharipov and F. A. Valeev, Russian Journal of Organic Chemistry,
2014, 50, 1504.
AZ Yu. S. Galimova, Yu. A. Khalilova, B. T. Sharipov, L. V. Spirikhin, Sh. R. Rameev, R. L.
Safiullin and F. A. Valeev, Russian Journal of Organic Chemistry, 2014, 50, 1848.
BA A. V. Samet, D. N. Lutov, S. I. Firgang, Yu. V. Nelyubina and V. V. Semenov, Russian
Chemical Bulletin International Edition, 2013, 62, 2196.
BB O. Yu. Doronina, Yu. A. Khalilova, B. T. Sharipov, L. V. Spirikhin, and F. A. Valeev,
Russian Journal of Organic Chemistry, 2012, 48, 1419.
BC L. Kh. Faizullina, M. G. Safarov, L. V. Spirikhin and F. A. Valeev, Russian Journal of
Organic Chemistry, 2010, 46, 768.
BD R. R. Rafikov, R. A. Novikov, E. V. Shulishov, L. D. Konyushkin, V. V. Semenov and Yu.
V. Tomilov, Russian Chemical Bulletin International Edition, 2009, 58, 1927.
BE K. P. Stockton, C. J. Merritt, C. J. Sumby and B. W. Greatrex, Eur. J. Org. Chem., 2015,
6999.
BF M. M. Zanardi and A. G. Suarez, Tetrahedron Letters, 2015, 56, 3762.
Hansen solubility parameters
Generally, Hansen solubility parameters may be used to characterise polarity of solvents in terms of their dispersion forces 6d, the degree of polarity that arises from any dipoles δρ, and their capacity for hydrogen bonding 5h. The solvents may be thus located in Hansen space, a three-dimensional (3D) representation of 5d, δρ and 5h. The closer two solvents are in the Hansen space, the more likely they are to exhibit the same solubilising properties. The Hansen dispersion forces 5d expressed by solvents may be similar, and so for a simpler representation of the Hansen solubility parameters, δρ may be plotted against 5h to represent different types of solvents in a two-dimensional (2D) graph.
In one example, the derivative has Hansen solubility parameters that are within 3 MPa½ of those of levoglucosenone. In one example, the derivative has Hansen solubility parameters that are within 2.4 MPa½ of those of levoglucosenone. In one example, the derivative has Hansen solubility parameters that are within 1.2 MPa½ of those of levoglucosenone.
In one example, the derivative has Hansen solubility parameters that are within 3 MPa½ of those of NMP. In one example, the derivative has Hansen solubility parameters that are within 2.4 MPa½ of those of NMP. In one example, the derivative has Hansen solubility parameters that are within 1.2 Pa½ of those of NMP.
In one example, the derivative has Hansen solubility parameters that are within 3 MPa½ of those of cyclopentanone, GBL and/or PGMEA. In one example, the derivative has Hansen solubility parameters that are within 2.4 MPa½ of those of cyclopentanone, GBL and/or PGMEA. In one example, the derivative has Hansen solubility parameters that are within 1.2 MPa½ of those of cyclopentanone, GBL and/or PGMEA.
In one example, the derivative has Hansen solubility parameters that are within 3 MPa½ of those of levoglucosenone, NMP, cyclopentanone, GBL and/or PGMEA. In one example, the derivative has Hansen solubility parameters that are within 2.4 MPa½ of those of levoglucosenone, NMP, cyclopentanone, GBL and/or PGMEA. In one example, the derivative has Hansen solubility parameters that are within 1.2 MPa½ of those of levoglucosenone, NMP, cyclopentanone, GBL and/or PGMEA.
Table S1 details Hansen solubility parameters of levoglucosenone, dihydrolevoglucosenone and derivatives thereof, determined as described in Pacheco et al. (2016).
Table 3 details physical properties and Hansen solubility parameters of various solvents, including levoglucosenone, dihydrolevoglucosenone and conventional solvents cyclopentanone, GBL and PGMEA, as described above. Table 3: Physical properties Hansen solubility parameters of various solvents, including levoglucosenone, dihydrolevoglucosenone and conventional solvents cyclopentanone, GBL and PGMEA, as described above, as reproduced in part from James Sherwood, Mario De bruyn, Andri Constantinou, Laurianne Moity, C. Rob McElroy, Thomas J. Farmer, Tony Duncan, Warwick Raverty, Andrew J. Hunt and James H. Clark (2014) Dihydrolevoglucosenone (Cyrene) as a bio-based alternative for dipolar aprotic solvents, Chem. Commun., 50, 9650-9652, DOI: 10.1039/C4CC04133J.
Figure imgf000034_0001
While the Hansen solubility parameters may suggest that levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof may substitute for conventional organic solvents, such as cyclopentanone, GBL or PGMEA, in SU-8 for example, as described above, the Hansen solubility parameters provide no indication that these may also be orthogonal solvents.
Surprisingly, as described above, the inventors have determined that levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof may also be orthogonal solvents, unlike the conventional organic solvents, such as cyclopentanone, GBL or PGMEA, as described above. That is, levoglucosenone, dihydrolevoglucosenone and/or the derivative thereof may both substitute for conventional organic solvents, such as cyclopentanone, GBL or PGMEA, in SU-8 for example, and may be orthogonal solvents, unlike the conventional organic solvents, such as cyclopentanone, GBL or PGMEA. Preferably, the derivate is S5, S6 or S7, as detailed in Table S1 . The hydroxyl precursors of these derivatives may be produced from levoglucosenone and/or dihydrolevoglucosenone using biocatalytic Baeyer Villiger oxidation, as described in A. L. Flourat, A. A. M. Peru, A. R. S. Teixeira, F. Brunissen and F. Allais, Chemo-enzymatic synthesis of key intermediates (S)-y-hydroxymethyl-a,p-butenolide and (S)-Y-hydroxymethyl-Y-butyrolactone via lipase-mediated Baeyer-Villiger oxidation of levoglucosenone, Green Chem., 2015, 17, 404, DOI: 10.1039/c4gc01231 c. Conversion of these hydroxyl precursors to S5, S6 and/or S7 is via acylation or alkylation reactions, which are well known in the art.
Figure 2 schematically depicts a 2D Hansen solubility parameter map, representing levoglucosenone, dihydrolevoglucosenone and derivatives thereof, as detailed in Table 1 , reproduced from Pacheco er al. (2016). In addition, conventional solvents cyclopentanone, GBL and PGMEA, as described above, are also represented. Key: 1 ': cyclohexane; 2': triethylamine; 3': toluene; 4': diethyl ether; 5': chloroform; 6': tetrahydrofuran; 7': 1 -butanol; 8': 1 :3-dioxolane; 9': 1 :2-dichloroethane; 10': acetic acid; 1 1': cyclohexanone; 12': ethanol; 13': acetone; 14': nitrobenzene; 15': benzonitrile ; 16': N,N- dimethylformamide (DMF); 17': dimethyl sulfoxide; 18': propylene carbonate; 19': acetonitrile; 20': nitromethane.
Figure 2 also schematically depicts levoglucosenone derivatives having Hansen solubility parameters that are within 3 MPa½ of those of levoglucosenone.
Cross-linkable composition
In one example, the passivation material comprises a cross-linkable composition. In this way, the passivation material may be soluble and/or dispersible in the solvent for deposition and by subsequent cross-linking after deposition, the passivation material may be resistant to organic solvents and/or aqueous solutions. Hence, the passivation material may meet at least some of the conflicting requirements, as described above.
In one example, the passivation material comprises the cross-linkable composition in an amount of at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97.5% or at least 99%, wherein the amount of cross-linkable composition is a percentage by weight of the passivation material.
In one example, the passivation material comprises the cross-linkable composition in an amount of at most 50%, at most 55%, at most 60%, at most 65%, at most 70%, at most 75%, at most 80%, at most 85%, at most 90%, at most 95%, at most 97.5%, at most 99% or at most 99.5%, wherein the amount of cross-linkable composition is a percentage by weight of the passivation material.
In one example, the cross-linkable composition comprises monomeric, oligomeric and/or polymeric precursors. Examples of cross-linkable compositions comprising monomeric, oligomeric and/or polymeric precursors include monomeric, oligomeric and/or polymeric precursors comprising, for example, cross-linkable epoxy groups, siloxane - organic hybrid frameworks comprising cross-linkable epoxy groups and/or cross-linkable acrylate or (alkyl)acrylate repeat units. Examples of cross-linking initiation include, for example, initiation thermally, photochemically, via a free radical reaction, via a thiol - ene or a thiol (alkyl)acrylate reaction, and/or via a thermal azide alkyne cycloaddition reaction.
In one example, the monomeric, oligomeric and/or polymeric precursors comprise epoxy groups, which may be cross-linked. A passivation layer may be formed by thermal or photochemical crossiinking of monomeric, oligomeric or polymeric precursors comprising epoxy groups. Typically, the passivation formulation may be coated onto a surface and then subjected to thermal or photochemical crosslinking conditions. An example of a suitable oligomeric precursor comprising epoxy groups is the commercial product EPON™ SU-8 resin (also known as EPIKOTE™ 157) available from Hexion. EPON™ Resin SU-8 is a polymeric solid epoxy novolac resin possessing an average epoxide group functionality around eight.
Suitable monomeric, oligomeric or polymeric precursors may also comprise siloxane - organic hybrid frameworks comprising epoxy groups.
Table 4 details examples of commercially available epoxy siloxane monomeric and oligomeric precursors including products PC-1000, PC-1035, PC-2000, PC-2004, PC-201 1 , PC-2021 and PC-2026 available from Polyset Inc (Mechanicville, NY, USA). Other epoxy siloxane monomeric and oligomeric precursors are known.
Table 4: Epoxy siloxane monomeric and oligomeric precursors commercially available from Polyset Inc.
Figure imgf000036_0001
An example of a crosslinked material prepared from epoxy siloxane precursors is described in J AppI Polymer Sci 2013, 39968, 1 - 7. In one example, the formulation comprises at least one of a cross-linking agent, a photoacid generator, a hardening agent, an antioxidant agent, a surfactant, and a filler.
The cross-linkable composition, for example comprising epoxy type monomers, oligomers or polymers, may also comprise crosslinking reagents and / or catalysts. A chemical reaction used provide a crosslinked, insoluble layer may be thermally or photochemically driven. ACS Applied Materials Interfaces 2009, 1 , 7, 1585 describes an example of a thermally driven crosslinking reaction for a thin film precursor comprising a polymer substituted with epoxy groups. In that example, methyl tetrahydrophthalic anhydride (MeTHPA) was used as a thermal curing agent and N,N- dimethylbenzylamine (BDMA) as a catalyst to promote thermal curing.
For photochemically driven crosslinking of thin films comprising precursors, for example functionalised with epoxy groups, the passivation formulation may comprise a photoacid generator (PAG). Generally, PAGs are reagents which generate active acid catalysts on exposure to visible or ultraviolet radiation, typically ultraviolet radiation. Many different types of PAG are known in the art. Suitable PAGs include materials in the Irgacure® series, commercially available from BASF (Germany). PAG reagents may be ionic or non ionic in nature, and within different PAGs the chemical structures may be designed to operate at different UV wavelengths. PAGs are commercially available for operation at I line (365 nm) and g / h line (405 nm, 436 nm) UV wavelengths, which are widely used within microelectronic fabrication processes. The cross-linkable composition, for example comprising epoxy type monomers, oligomers or polymers as described above, may also comprise a hardener (also known as a hardening reagent or agent) which may be used to adjust the curing time and / or the mechanical properties of the resulting crosslinked passivation layer. Examples of suitable hardeners include the ARON series of oxetane hardeners available from Toagosei (Japan).
The cross-linkable composition, for example comprising epoxy type monomers, oligomers or polymers as described above, may also comprise an antioxidant. The antioxidant may be used to suppress discolouration (yellowing) in the crosslinkable or crosslinked film, for example due to side reactions with the PAG or its chemical byproducts. Examples of suitable antioxidants are described in US 2013 / 225711 A1.
In one example, the monomeric, oligomeric and/or polymeric precursors comprise (alkyl)acrylate repeat units, for example acrylate or methacrylate repeat units. Crosslinkable monomers, oligomers or polymers comprising acrylate or methacrylate repeat units, herein described collectively as (alkyl)acrylate, may be highly useful for the formation of crosslinked passivation layers. A wide variety of (alkyl)acrylate thin film coating precursors are commercially available, for example under the SARTOMER brand produced by Arkema (France). It is known in the art that (alkyl)acrylate precursors may be selected and formulated in different proportions to provide different properties in crosslinked thin film coatings.
The (alkyl)acrylate precursors used to produce crosslinked thin film coatings, such as a passivation layer, may be monofunctional, difunctional or multifunctional and may be optionally be substituted with additional non (alkyl)acrylate reactive functional groups, allowing further crosslinking by alternative chemical methods other than those used to polymerise the (alkyl)acrylate groups. Examples of additional non (alkyl)acrylate reactive functional groups are epoxy groups, or cinnamylidene groups are described in WO 2013 / 1 19717 A1.
The crosslinkable (alkyl)acrylate precursors suitable for use in the cross-linkable composition may themselves be oligomeric or polymeric in nature. An example of such a material is SIRIUS-501 , a dendrimeric acrylate produced by Osaka Organic Chemical Industry Ltd (Japan).
(Alkyl)acrylate precursors suitable for use in thermally or photochemically crosslinkable films, such as passivation layers, may optionally be substituted with partially or fully fluorinated side chains. Thin films comprising polymers prepared from these precursors, and therefore bearing such side chain substitutents, may have usefully altered properties, such as chemical resistance, hydrophobicity or surface energy.
Table 5 details a range of fluorinated (alkyl)acrylate precursors commercially available from Sigma Aldrich, a subsidiary of Merck KGaA (Germany). Other fluorinated (alkyl)acrylate precursors are known.
Table 5: Fluorinated (alkyl)acrylate precursors are commercially available from Sigma Aldrich
Figure imgf000038_0001
Figure imgf000039_0001
Suitable monomeric, oligomeric or polymeric precursors may also comprise siloxane - organic hybrid frameworks comprising (alkyl)acrylate groups. An example of such a hybrid precursor is described in J Sol Gel Sci Technol 2012, 61 , 2, 321.
The cross-linkable composition comprising monomeric, oligomeric or polymeric (alkyl)acrylate precursors may be crosslinked using free radical reactions. The cross-linkable composition used to form crosslinkable films may additionally comprise a free radical initiator. Typically, the free radical initiator is initiated under thermal or photochemical conditions. Many examples of free radical initiators, suitable for either thermal or photochemical initiation, are known in the art.
Table 6 details free radical thermal initiators commercially available from Sigma Aldrich, a subsidiary of Merck KGaA (Germany). Table 6: Free radical thermal initiators available from Sigma Aldrich.
Sigma Aldrich
Catalogue Number Free radical thermal initiator
441465 tert-Amyl peroxybenzoate
118168 4,4-Azobis(4-cyanovaleric acid)
380210 1 , 1 '-Azobis(cyclohexanecarbonitrile)
441090 2,2'-Azobisisobutyronitrile (AIBN)
179981 Benzoyl peroxide
441694 2,2-Bis(tert-butylperoxy)butane
388149 1 ,1-Bis(tert-butylperoxy)cyclohexane
388092 2,5-Bis(tert-butylperoxy)-2,5-dimethylhexane
329533 2,5-Bis(tert-Butylperoxy)-2,5-dimethyl-3-hexyne
441716 Bis(1 -(tert-butylperoxy)-1-methylethyl)benzene 388084 1 , 1 -Bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane
416665 tert-Butyl hydroperoxide
388076 tert-Butyl peracetate
168521 tert-Butyl peroxide
159042 tert-Butyl peroxybenzoate
441473 tert-Butylperoxy isopropyl carbonate
247502 Cumene hydroperoxide
289086 Cyclohexanone peroxide
329541 Dicumyl peroxide
290785 Lauroyl peroxide
441821 2,4- Pentanedione peroxide
269336 Peracetic acid
216224 Potassium persulfate
Table 7 details free radical photoinitiators commercially available from Sigma Aldrich, a subsidiary of Merck KGaA (Germany).
Table 7: Free radical photoinitiators available from Sigma Aldrich.
Sigma Aldrich
Catalogue Number Free radical photoinitiator
A1 ,070-1 Acetophenone, 99%
A8.840-9 Anisoin, 95%
A9.000-4 Anthraquinone, 97%
12,324-2 Anthraquinone-2-sulfonic acid, sodium salt monohydrate, 97%
11 ,931 -8 (Benzene) tricarbonylchromium, 98%
B515-1 Benzil, 98%
39,939-6 Benzoin, sublimed, 99.5+%
17,200-6 Benzoin ethyl ether, 99%
19,578-2 Benzoin isobutyl ether, tech., 90%
B870-3 Benzoin methyl ether, 96%
B930-0 Benzophenone, 99%
40,562-0 Benzophenone/1-Hydroxycyclohexyl phenyl ketone, 50/50 blend
26,246-3 3,3',4,4'-Benzophenonetetracarboxylic dianhydride, sublimed, 98%
B1 , 260-1 4-Benzoylbiphenyl, 99%
40,564-7 2-Benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone, 97%
16,032-6 4,4'-Bis(diethylamino)benzophenone, 99+%
14,783-4 4,4'-Bis(dimethylamino)benzophenone, 98%
12,489-3 Camphorquinone, 98%
C7.240-4 2-Chlorothioxanthen-9-one, 98%
40,807-7 (Cumene)cyclopentadienyliron(ll) hexafluorophosphate, 98%
D3, 173-7 Dibenzosuberenone, 97%
22,710-2 2,2-Diethoxyacetophenone, 95%
D11 ,050-7 4,4'-Dihydroxybenzophenone, 99%
19,611 -8 2,2-Dimethoxy-2-phenylacetophenone, 99% 14,934-9 4-(Dimethylamino)benzophenone, 98%
14,670-6 4,4'-Dimethylbenzil, 97%
D14.966-7 2,5-Dimethylbenzophenone, tech., 95%
D14.967-5 3,4-Dimethylbenzophenone, 99%
Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide/ 2-Hydroxy-2-
40,566-3 methylpropiophenone, 50/50 blend
27,571 -9 4'-Ethoxyacetophenone, 98%
E1 , 220-6 2-Ethylanthraquinone, 97+%
F40-8 Ferrocene, 98%
32,810-3 3'-Hydroxyacetophenone, 99+%
27,856-4 4'-Hydroxyacetophenone, 99%
22,043-4 3-Hydroxybenzophenone, 99%
H2.020-2 4-Hydroxybenzophenone, 98%
40,561 -2 1 -Hydroxycyclohexyl phenyl ketone, 99%
40,565-5 2-Hydroxy-2-methylpropiophenone, 97%
15,753-8 2-Methylbenzophenone, 98%
19,805-6 3-Methylbenzophenone, 99%
M3.050-7 Methybenzoylformate, 98%
40563-9 2-Methyl-4'-(methylthio)-2-morpholinopropiophenone, 98%
15,650-7 Phenanthrenequinone, 99+%
29,074-2 4'-Phenoxyacetophenone, 98%
T3.400-2 Thioxanthen-9-one, 98%
In analogy to PAGs used for epoxy group polymerisation, a variety of photochemical free radical initiators are available, allowing the operation of the photochemical crosslinking process at different wavelengths, including i line (365 nm) and g / h line (405 nm, 436 nm).
Certain types of commercially available photochemical free radical initiators are known as Type II initiators. These photoinitiators typically require the presence of a further reagent, known as a co - initiator. Commonly used examples of co - initiators for Type II systems are alcohols or amines. In one example, the monomeric, oligomeric and/or polymeric precursors are cross-linkable via a thiol - ene or a thiol (alkyl)acrylate reaction for example, as described below.
A further type of useful chemical reaction which is suitable for the preparation of crosslinked thin films, such as a passivation layer, is the thiol - ene reaction. The thiol ene reaction involves the reaction of an unsaturated double bond with a separate precursor bearing a thiol (-SH) group. The unsaturated double bond may be a (alkyl)acrylate, in which case the process may be described as a thiol - (alkyl)acrylate reaction. The thiol - ene or thiol - (alkyl)acrylate reaction is typically a radical reaction, which may be initiated thermally or photochemically as described above for polymerisation processes using only (alkyl)acrylate precursors.
A useful property of the thiol - ene, or thiol - (alkyl)acrylate reaction, as used in the preparation of crosslinked thin film coatings, such as a passivation layer, is that the reaction process is less sensitive to inhibition from atmospheric oxygen, allowing the crosslinking process to be carried out in air rather than under an inert gas blanket.
Suitable precursors for thermal or photochemical crosslinking processes using thiol - ene or thiol - (alkyl)acrylate reactions may be monomeric, oligomeric or polymeric in nature. An example of the use of thiol - ene reaction to provide crosslinked films, suitable for use as insulating layers in organic electronic devices, is described in Chem Mater 2013, 25, 4806.
In one example, the monomeric, oligomeric and/or polymeric precursors are cross-linkable via a thermal azide alkyne cycloaddition reaction, for example, as described below.
An example of cross-linking via a thermal azide alkyne cycloaddition reaction is described in Shengxia Li, Wei Tang, Weimin Zhang, Xiaojun Guo, and Qing Zhang, Cross-linked Polymer-Blend Gate Dielectrics through Thermal Click Chemistry, Chem. Eur. J. 2015, 21 , 17762 - 17768 DOI: 10.1002/chem.201502825.
Another example of cross-linking via a thermal azide alkyne cycloaddition reaction is described in Sheng-Xia Li, Lin-Run Feng, Xiao-Jun Guo, Qing Zhang, Application of thermal azide-alkyne cycloaddition (TAAC) reaction as a low temperature cross-linking method in polymer gate dielectrics for organic field effect transistors, J. Mater. Chem. C, 2014, DOI: 10.1039/C4TC00116H.
In one example, the cross-linkable composition comprises a polyimide. Typically, polyimides are examples of oligomeric precursors. Polyimides are useful materials for the formation of protective films. The chemistry and properties of polyimides are usefully reviewed in the Handbook of Polymer Coatings for Electronics : Chemistry, Technology and Applications (2nd Edition) p 55 - 65. Efforts have been made to improve the solubility and solution processability of polyimides, and solvent soluble polyimides are known in the art. A suitable class of polyimides for use in the current invention are soluble polyimide oligomers. Soluble polyimide oligomers may be further functionalised with suitable groups for thermal or photochemical crosslinking reactions, other than the backbone polyimide functional groups. The polyimide oligomers have good solvent solubility properties due to their low average molecular weight, and may be conveniently coated by solution processing methods. The resulting film may then be subjected to thermal or photochemical crosslinking processes, dependent on the nature of the further functionalised crosslinkable groups. This results in a highly insoluble crosslinked film. Examples of thermally crosslinked films produced from polyimide oligomers are described in EP 2524947 A1.
In one example, the cross-linkable composition comprises a cycloolefinic polymer. Typically, cycloolefinic polymers are examples of oligomeric or polymeric precursors. A further class of material useful for passivation layers in organic electronic devices are cycloolefinic polymers. Cycloolefinic polymers bearing chemical substituents allowing further thermal or photochemical crosslinking, after deposition of the non crosslinked film, are known in the art. Examples of suitable cycloolefinic polymers with crosslinkable side groups are described in US 9082981 and WO 2013 / 120581.
In one example, the cross-linkable composition comprises a substituted poly(vinylphenol) derivative, for example, as described below. For example, the poly(vinylphenol) may be substituted at the phenolic group (e.g. alkyl, aryl, aralkyl with optional further substitutions). Chem Mater 2015, 25, 4806 shows one possible type of substitution (O-allyl).
Suitably substituted poly(vinylphenol) derivatives are a further class of crosslinked thin film coating precursors suitable for use in the cross-linkable composition. Chem Mater 2015, 25, 4806 describes a soluble thin film forming composition comprising the O-allyl derivative of poly(vinylphenol) and pentaerythritol tetra(3-mercaptopropionate) which is then thermally crosslinked by thiol - ene reaction using AIBN as the radical initiator.
WO 2013 / 1 19717 describes derivatives of poly(vinylphenol) that may be crosslinked under photochemical conditions to provide insoluble films, such as a passivation layer.
In one example, the formulation comprises a surfactant, to improve coating properties, such as surface wetting, levelling and flow. Formulations of the current invention may optionally comprise surfactants, for example fluorinated surfactants and/or siloxane solvents, to improve coating properties, such as surface wetting, levelling and flow. An amount of a surfactant, such as a fluorosurfactant, in the formulation may be in a range of from 0 to 5% by weight of the formulation, preferably in a range of from 0 to 2 % by weight of the formulation. The amount of the surfactant may be at least 0.001 %, at least 0.01 % or at least 0.1 % by weight of the formulation.
An example fluorosurfactant is commercially available from AGC Seimi Chemical Co., Ltd. (Japan) as SURFLON. Table 8 details fluorosurfactants commercially available from Cytonix LLC, Maryland (USA) as FluorN.
Table 8: Fluorosurfactants available from Cytonix.
FluorN Chemical Description
561 Fluorinated Ethylene Glycol
562 Fluorinated Ethylene Glycol 659 Perfluoroalkyl Stearate
1740G Fluoro-acrylate Copolymer
S83 Fluoro-acrylate Copolymer
20158 Fluoro-acrylate Copolymer
2900N PFPE polyethylene glycol
1788 PFPE-diisocyanate
Table 9 details fluorosurfactants commercially available from DIC Corporation, Tokyo (Japan) as EGAFACE. Preferred fluorosurfactants include MEGAFACE R-41 , R-40, R-40-LM, R-43, F-556, F- 557, F-554, F-559, RS-72-K, F-567, F-563, F-560, F-444, F-553, F-477, F-554, F-556, F-557, F-568, F- 563 and F-560.
Table 9: Fluorosurfactants available from DIC Corporation.
MEGAFACE
Description
Product Number
F-1 14 Perfluorobutanesulfonate
F-251 Oligomer with fluoro and lipophilic group
F-253 Oligomer with fluoro and lipophilic group
F-281 Oligomer with fluoro and lipophilic group
F-410 Carboxylate with perfluoroalkyl group
F-430 Oligomer with fluoro and hydrophilic group
F-444 Perfluoroalkyl ethylene oxide adduct
F-477 Oligomer with fluoro, hydrophilic and lipophilic group
F-510 phosphoric ester with fluoro group
F-511 Ammonium phosphate with fluoro group
F-551 Oligomer with fluoro and lipophilic group
F-552 Oligomer with fluoro and lipophilic group
F-553 Oligomer with fluoro, hydrophilic and lipophilic group
F-554 Oligomer with fluoro and lipophilic group
F-555 Oligomer with fluoro, hydrophilic and lipophilic group
F-556 Oligomer with fluoro, hydrophilic and lipophilic group
F-557 Oligomer with fluoro, hydrophilic and lipophilic group
F-558 Oligomer with fluoro and lipophilic group
F-559 Oligomer with fluoro, hydrophilic and lipophilic group
F-560 Oligomer with fluoro and lipophilic group
F-561 Oligomer with fluoro and lipophilic group
F-562 Oligomer with fluoro, hydrophilic and lipophilic group
F-563 Oligomer with fluoro and lipophilic group
F-565 Oligomer with fluoro, hydrophilic and lipophilic group
F-568 Oligomer with fluoro, hydrophilic and lipophilic group
F-569 Oligomer with fluoro and hydrophilic group
F-570 Oligomer with fluoro, hydrophilic, lipophilic and carboxyl group
F-571 Oligomer with fluoro, hydrophilic and lipophilic group
F-572 Oligomer with fluoro and lipophilic group R-40 Oligomer with fluoro, hydrophilic and lipophilic group
R-40-LM Oligomer with fluoro, hydrophilic and lipophilic group
R-41 Oligomer with fluoro and lipophilic group
R-43 Oligomer with fluoro and lipophilic group
R-94 Oligomer with fluoro, hydrophilic and lipophilic group
RS-55 Oligomer with fluoro, hydrophilicjipophilic and UV reactive group
RS-56 Oligomer with fluoro, hydrophilicjipophilic and UV reactive group
RS-72-K Oligomer with fluoro, hydrophilicjipophilic and UV reactive group
RS-75 Oligomer with fluoro, hydrophilicjipophilic and UV reactive group
RS-76-E Oligomer with fluoro, hydrophilicjipophilic and UV reactive group
RS-76-NS Oligomer with fluoro, hydrophilicjipophilic and UV reactive group
RS-78 Oligomer with fluoro, hydrophilicjipophilic and UV reactive group
RS-90 Oligomer with fluoro, hydrophilicjipophilic and UV reactive group
Formulations of the current invention may optionally comprise a siloxane solvent, particularly a cyclic siloxane solvent. The siloxane solvent may be used to alter the wetting, levelling and flow properties of the formulation. Examples of suitable siloxane solvent additives include octamethylcyclotetrasiloxane (BP 175 °C), decamethylcyclopentasiloxane (BP 210 °C) and dodecamethylcyclohexasiloxane (BP 245 °C). The loading of siloxane solvent in the composition would be 0 - 10 % by weight of the passivation material, preferably 0 - 5 % by weight of the passivation material, more preferably 0 - 2 % by weight of the passivation material. An amount of siloxane solvent in the formulation may be in a range of from 0 to 10 % by weight of the formulation, preferably in a range of from 0 to 5 % by weight of the passivation material, more preferably in a range of from 0 to 2 % by weight of the passivation material. The amount of the surfactant may be at least 0.001 %, at least 0.01 % or at least 0.1 % by weight of the passivation material. In one example, the formulation comprises a filler, to alter physical and/or electrical properties of the crosslinked layer.
Suitable compositions for use in the current invention may optionally also comprise a filler. Fillers may usefully alter the physical and/or electrical properties of the crosslinked thin film coating, for example, dielectric constant, mechanical strength or dielectric breakdown strength. Suitable fillers include inorganic nanoparticles, in which case the resulting crosslinked film may be described as a polymer nanocomposite. Examples of suitable fillers are described in Materials 2009, 2, 1697-1733; doi: 10.3390/ma2041697. These described fillers include inorganic fillers, for example BaTi03, PMN-PT (65/35), PbNb206, PLZT (7/60/40), Si02, Al203l Ta205, Ti02, SrTi03, Zr02, Hf02, HfSi04, La203, Y203, o-I_aAI03, CaCu3Ti40i2 and Lai.8Sr0.2NiO4. These inorganic fillers may be provided as particles, for example microparticles and/or nanoparticles.
Organic Semiconductor (OSC) materials The organic semiconductor material (OSC) layer comprises a single component or muiticomponent blend of materials which may be evaporated or solution processed. The OSC layer is preferably solution processable and can be polymeric but preferably comprises a semiconducting non-polymeric polycyclic compound, such as a semiconducting non-polymeric organic polycyclic compound, which is an OSC (also known as a small molecule organic semiconductor).
Preferably, the semiconducting non-polymeric polycyclic compounds have charge carrier mobilities of 1CT1 cm2/Vs or more, more preferably of 0.5 cm2/Vs or more, even more preferably of 2 cm2/Vs or more. Preferably, the semiconducting non-polymeric polycyclic compounds have charge carrier mobilities of less than 100 cm2/Vs. The semiconducting non-polymeric polycyclic compound charge mobility can be determined through field effect transistor measurements on drop cast films or thermally evaporated single crystal films.
Any suitable semiconducting non-polymeric polycyclic compound may be used. These may be p-type or n-type OSC materials.
Examples of suitable semiconducting non-polymeric polycyclic compounds include polyacenes. Suitable polyacenes are disclosed in WO 2012/164282. For example, suitable polyacenes may have the Formula (III):
Figure imgf000046_0001
Formula (III) wherein each of R , R , R and R are hydrogen;
R55 and R33 are each -C≡C-SiR35R36R37, wherein R35, R36 and R37 are each independently selected from C1-C4 alkyl, C2-C4 alkenyl and C3-C6 cycloalkyl;
R50, R51, R52, R53, R57, R29, R30 and R31 are each independently selected from hydrogen, CrC4 alkyl, C C6 alkoxy and C6-C12 aryloxy; or wherein independently each pair of R51 and R52 and/or R29 and R30 may be cross- bridged to form a C4-C10 saturated or unsaturated ring, which saturated or unsaturated ring may be intervened by an oxygen atom, a sulfur atom or a group shown by formula -N(R49)- (wherein R49 is a hydrogen atom, a C C6 alkyl group or a C C10 perfluoroalkyl group; and wherein k and I are independently 0 or 1 , preferably both k and I are 1 or both k and I are 0. Suitably, in compounds of Formula (III), k and I are both 1 ; R and R are -C≡C-SiR R R , wherein R35, R36 and R37 are each independently selected from ethyl, n-propyl, isopropyl, 1 -propenyl, 2-propenyl and C3-C6 cycloalkyl; and R50, R51 , R52, R53, R57, R29, R30 and R31 are each independently selected from hydrogen, methyl, ethyl and methoxy.
Suitably, in compounds of Formula (III), k and I are both 0; Ff and R are -CSC-SiR^R^R , wherein R35, R36 and R37 are each independently selected from ethyl, n-propyl, isopropyl, 1-propenyl, 2-propenyl and C3-C6 cycloalkyl; R50, R53, R57 and R31 are hydrogen; and R51 and R52 together, and R29 and R30 together, form 5-membered heterocyclic rings containing 1 or 2 nitrogen atoms, 1 or 2 sulfur atoms or 1 or 2 oxygen atoms, wherein the heterocyclic rings may be optionally substituted, for example by Ci-C6 alkyl and halo.
Especially preferred polyacene compounds are those of Formulae (IV) and (V):
Figure imgf000047_0001
Formula (IV) wherein R , R , R and R are each independently selected from hydrogen, C C6 alkyl and C C6 alkoxy (preferably R50, R53, R57 and R31 are each independently selected from hydrogen, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, methoxy, ethoxy, propyloxy and butyloxy, more preferably hydrogen, methyl, propyl and methoxy); R51, R52, R29 and R30 are each independently selected from hydrogen, Ci-C6 alkyl and Ci-C6 alkoxy, or each pair of R51 and R52 and/or R29 and R30, are cross-bridged to form a C4-C10 saturated or unsaturated ring, which saturated or unsaturated ring may be intervened by an oxygen atom, a sulfur atom or a group shown by formula -N(R38)- (wherein R38 is hydrogen or C C 0 alkyl); and wherein one or more of the carbon atoms of the polyacene skeleton may optionally be substituted by a heteroatom selected from N, P, As, O, S, Se and Te (preferably, R51, R52, R29 and R30 are each independently selected from hydrogen, methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, methoxy, ethoxy, propyloxy and butyloxy, more preferably hydrogen, methyl, ethyl, propyl and methoxy); and R39, R40 and R41 are each independently selected from C C6 alkyl and C2-C6 alkenyl (preferably R39, R40 and R41 are each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, 1 -propenyl and 2-propenyl, more preferably ethyl, n-propyl and isopropyl).
Figure imgf000048_0001
Formula (V) wherein R , R and R are each independently selected from C C6 alkyl and C2-C6 alkenyl (preferably R39, R40 and R41 are each independently selected from methyl, ethyl, propyl, isopropyl, n- butyl, isobutyl, t-butyl, 1 -propenyl and 2-propenyl, more preferably ethyl, n-propyl and isopropyl);
R and R are each independently selected from hydrogen, halogen, cyano, optionally fluorinated or perfluorinated C C2o alkyl, fluorinated or perfluorinated, C C2o alkoxy, fluorinated or perfluorinated C6- C30 aryl and C02R44, wherein R44 is hydrogen, fluorinated or perfluorinated C1-C2o alkyl, or fluorinated or perfluorinated C6-C30 aryl (preferably R42 and R43 are each independently selected from fluorinated or perfluorinated C C8 alkyl, fluorinated or perfluorinated Ci-C8 alkoxy and C6F5); and
Y1, Y2, Y3 and Y4 are each independently selected from -CH=, =CH-, O, S, Se or NR45 (wherein R45 is hydrogen or C C 0 alkyl).
In yet another preferred embodiment, the polyacene compounds of the present invention are those of Formulae (VI) and (VII):
Figure imgf000049_0001
Formula (VI)
Figure imgf000049_0002
Formula (VII) wherein R , R and R are each independently selected from methyl, ethyl and isopropyl; wherein R , R , R , R , R , R , RJ0 and RJ are each independently selected from C C6 alkyl, C C6 alkoxy and C6-C20 aryloxy. Preferably R50, R51, R52, R53, R57, R29, R30 and R31 are each independently selected from methyl, ethyl, propyl, n-butyl, isobutyl, t-butyl, methoxy, ethoxy, propyloxy and butyloxy. Polyacene compounds may be synthesised by any known method within the common general knowledge of a person skilled in the art. In a preferred embodiment, methods disclosed in US 2003/01 16755 A, US 3,557,233, US 6,690,029 WO 2007/078993, WO 2008/128618 and Organic Letters, 2004, Volume 6, number 10, pages 1609-1612 can be employed for the synthesis of polyacene compounds.
Preferably, the polyacene compounds have charge carrier mobilities of 10"1 cm2/Vs or more, more preferably of 0.5 cm2/Vs or more, even more preferably of 2 cm2/Vs or more. Preferably, the polyacene compounds have charge carrier mobilities of less than 100 cm2/Vs. The polyacene charge mobility can be determined through field effect transistor measurements on drop cast films or thermally evaporated single crystal films.
For example, a suitable polyacene is 1 ,4,8,1 1 -tetramethyl-6,13-bis(triethylsilylethynyl)pentacene (TMTES).
Alternative semiconducting non-polymeric polycyclic compounds used in the invention could include the following materials, either applied via solution processing or evaporation: pentacene, 2,7- Dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT), 2,9-didecyldinaphtho[2,3-b:2',3'-f]thieno[3,2- b]thiophene (C10-DNTT), 3,11-didecyl-dinaphtho[2,3-d:2',3'-d]benzo[1 ,2-b:4,5-bldithiophene (C10- DNBDT), 8,17-bis((triisopropylsilyl)ethynyl)tetraceno[2,1 ,12-qra]tetracene (Formula (VIII)), 8,17- bis((diisopropyl(octyl)silyl)ethynyl)tetraceno[2,1 ,12-qra]tetracene (Formula (IX)).
Figure imgf000050_0001
Formula (VIII)
Figure imgf000050_0002
(Formula IX) Suitable n-type small molecules could include naphthalene diimides (NTCDI) or perylene tetracarboxylic diimides (PTC DA), [6,6]-phenyl-C61 -butyric acid ester ([60]PCBM) and [6,6]-phenyl-C71 -butyric acid methyl ester ([70]PCBM).
The OSC layer may optionally comprise a polymeric binder material to aid film forming and uniformity. Suitable binder materials can be found in WO2012160383 which discloses high-k (permittivity > 3.4) binders in combination with small molecule semiconductors, or WO2005055248 which discloses low-k binders (1.1 <k<3.3) in combination with small molecule semiconductors.
Organic Gate Insulator (OGI) materials
Suitable OGI materials are polymers that can be crosslinked such that they are solvent resistant or based upon polymers that are not soluble in levoglucosenone or dihydrolevoglucosenone or a derivative thereof. Examples of preferred polymers include polymers with greater than 30% of fluorine by weight and are soluble in fluorinated or perfluorinated solvents. Examples of preferred soluble amorphous fluoropolymers include Cytop (Asahi), Teflon AF (DuPont), Hyflon AD (Solvay), Fluoropel (Cytonix). Suitable solvents for the fluorinated OGI layer include Fluorinert (trade name) FC43, or Hydrofluoroethers Novec (3M) HFE7500 or HFE7700.
OGI materials may be vapor deposited through chemical vapor deposition, such as parylene, or thermal evaporation, but it is especially preferred that the OGI is deposited by solution processing.
In one example, the passivation layer provides an interlayer dielectric, arranged to isolate, for example electrically isolate, metal layers, for example a metal gate electrode from a source and/or drain electrode, on the OE device.
Dihydrolevoglucosenone For the avoidance of doubt, statements of invention below explicitly recite dihydrolevoglucosenone, as described above in detail. The formulation, the solvent and/or the passivation material, together with the OE device and the organic layer, may be as described above in relation to this first aspect.
In one example, the solvent comprises dihydrolevoglucosenone.
In one example, the solvent comprises dihydrolevoglucosenone and the passivation material comprises the cross-linkable composition.
In one example, the solvent comprises dihydrolevoglucosenone and the cross-linkable composition comprises monomeric, oligomeric and/or polymeric precursors. In one example, the solvent comprises dihydrolevoglucosenone and the monomeric, oligomeric and/or polymeric precursors comprise an epoxy group.
In one example, the solvent comprises dihydrolevoglucosenone and the monomeric, oligomeric and/or polymeric precursors comprise acrylate or methacrylate repeat units.
In one example, the solvent comprises dihydrolevoglucosenone and the monomeric, oligomeric and/or polymeric precursors are cross-linkable via a thiol - ene or a thiol (alkyl)acrylate reaction. In one example, the solvent comprises dihydrolevoglucosenone and the monomeric, oligomeric and/or polymeric precursors are cross-linkable via a thermal azide alkyne cycloaddition reaction.
In one example, the solvent comprises dihydrolevoglucosenone and the cross-linkable composition comprises a polyimide.
In one example, the solvent comprises dihydrolevoglucosenone and the cross-linkable composition comprises a cycloolefinic polymer.
In one example, the solvent comprises dihydrolevoglucosenone and the cross-linkable composition comprises a substituted poly(vinylphenol) derivative.
In one example, the solvent comprises dihydrolevoglucosenone and the formulation comprises at least one of a cross-linking agent, a photoacid generator, a hardening agent, an antioxidant agent, a surfactant, and a filler.
In one example, the solvent comprises dihydrolevoglucosenone and a cosolvent.
The second aspect of the invention provides a method of fabricating an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer, wherein the method comprises:
providing a passivation layer on at least a part of the organic layer by depositing a formulation according to the first aspect and removing the solvent, for example, at least a part of the solvent, substantially all of the solvent and/or all of the solvent. In one example, the method comprises providing a substrate. The substrate may comprise glass, metal, a polymer or an IC, for example. The substrate may include an optional buffer layer (also known as a sublayer) provided on the surface of the substrate. The buffer layer may also be known as a polarization layer, provided by a crosslinkable polymer that may improve surface uniformity and/or homogeneity by smoothing imperfections in the surface of the substrate and may provide a chemically insert surface upon which an OE device is fabricated. The buffer layer may comprise SU-8, crosslinked acrylate polymers or polycycloolefinic polymers, for example. Alternatively, the substrate may comprise polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), for example, which may be processed without a buffer layer.
In one example, the method comprises providing a source and/or a drain electrode on the surface of the substrate, for example by sputtering and photolithography. The source and the drain electrodes are typically a metal, for example silver or gold or alloys thereof, or a non-metal. The source and the drain electrodes may be treated with a thiol solution, to adjust work functions of the source and the drain electrodes. In this way, injection of charges into an overlaying OSC layer may be improved. Excess thiol solution may be washed away, with thiol binding only to the source and the drain electrodes.
In one example, the method comprises providing an OSC layer over the source and the drain electrodes and the exposed surface of the substrate, for example by spin coating or printing. The OSC layer typically has a thickness of 30 nm. In one example, the method comprises providing an OGI layer over the OSC layer, for example by spin coating or printing. The OGI layer typically has a thickness of 300 nm. A metal layer, for example silver or gold or alloys thereof, may be subsequently deposited on the OGI layer, for example by evaporation. A photoresist may be subsequently patterned (e.g. by photolithography) on the metal layer and portions of the metal layer exposed through the patterned photoresist may be removed by wet etching. The patterned metal layer may provide a gate, such as a thin film transistor (TFT) gate. The patterned metal layer may provide a hardmask against reactive ion etching (RIE) (also known as dry etching, for example using 02 and/or Ar), thereby masking the underlying OGI layer, the OSC layer and the source and the drain electrodes. Subsequently, RIE may remove portions of the OGI layer and the OSC layer, that are not masked by the patterned metal layer. In this way, a stack comprising the patterned metal layer, OGI layer, the OSC layer and the source and the drain electrodes may be provided on the substrate. It should be understood that the stack generally describes a multilayered structure and thus may comprise more or fewer and/or different layers. For example, the stack may comprise those layers at an intermediary stage of fabrication of the OE device. For example, the stack may comprise all layers of the completed OE device. That is, layers included in the stack may change during fabrication, by addition and/or by removal of layers. Sides of the OGI layer and sides of the OSC layer may be thus exposed, for example by the RIE, and may be adversely affected by unsuitable solvents. Further, inter-layer interfaces may also be exposed, for example between the substrate and the OSC layer, between the OSC layer and the OGI layer and/or between the OGI layer and the metal layer. These inter-layer interfaces may be subject to solvent penetration, as described previously, thereby providing another vector of attack by unsuitable solvents. Other surfaces of the OGI layer and/or the OSC layer may be additionally and/or alternatively exposed.
In one example, the method comprises providing the passivation layer over the stack and the exposed surface of the substrate, for example, by coating with a formulation according to an exemplary embodiment of the invention. In one example, the method comprises providing a positive photoresist mask over the passivation layer. In one example, the method comprises forming a first hole or via through the passivation layer to the patterned metal layer, by RIE through the positive photoresist mask, thereby exposing at least a part of the surface of the metal layer. In one example, the method comprises removing residual photoresist mask.
In one example, the method comprises providing a metal gate interconnect through the first hole to the patterned metal layer, for example, by sputtering, masking and etching. The third aspect of the invention provides an organic electronic (OE) device comprising an organic layer and a passivation layer directly thereon, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer and wherein the passivation layer comprises a cross-linked product of a cross-linkable composition according to the first aspect. In one example, the OE device is selected from a group consisting of an Organic Field Effect Transistor (OFET) such as a bottom gate OFET or preferably a top gate OFET , including Organic Thin Film Transistors (OTFT), an Organic Light Emitting Diode (OLED), an Organic Photovoltaic (OPV) device and an Organic Photodetector (OPD). The fourth aspect of the invention provides a product comprising an organic electronic (OE) device fabricated according to the second aspect and/or an OE device according to the third aspect.
In one example, the product is selected from a group consisting of an Integrated Circuit (IC), a Radio Frequency Identification (RFID) tag, a security marking or security device containing an RFID tag, a Flat Panel Display (FPD), a backplane of an FPD, a backlight of an FPD, an electrophotographic device, an electrophotographic recording device, an organic memory device, a sensor, a biosensor and a biochip.
The fifth aspect of the invention provides a flowable formulation comprising a photopatterning material and a solvent;
wherein the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof.
The solvent may be as described with respect to the first aspect. The photopatterning material may be similar to the passivation material described with respect to the first aspect.
The sixth aspect of the invention provides use of a solvent comprising levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof in a method of fabricating an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer. The solvent may be as described with respect to the first aspect. The method of fabricating may be as described with respect to the second aspect.
Brief Description of the Drawings
For a better understanding of the invention, and to show how exemplary embodiments of the same may be brought into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which; Figure 1 shows schematically a method of fabrication of an OE device using conventional solution processable passivation materials;
Figure 2 schematically depicts a 2D Hansen solubility parameter map; Figure 3 shows schematically a method of fabrication of an OE device according to an embodiment of aspects of the invention;
Figure 4 shows schematically another method of fabrication of an OE device according to an embodiment of aspects of the invention;
Figures 5A and 5B show transfer and mobility curve data, respectively, after gold gate electrode patterning of OE devices fabricated according to an embodiment of aspects of the invention;
Figure 6A and 6B show transfer and mobility curve data, respectively, after dry etch patterning of the OE devices of Figure 5;
Figures 7A and 7B shows transfer and mobility curve data, respectively, after passivation layer deposition of the OE devices of Figure 6; Figures 8A and 8B show optical micrographs of the OE devices of Figure 6 after washing with Cyrene and PGMEA, respectively;
Figures 9A and 9B show optical micrographs of the OE devices of Figure 6 after washing with Cyrene and GBL, respectively;
Figure 10 shows an optical micrograph of via structures, formed by photopatterning according to an exemplary embodiment of the invention;
Figure 1 1 shows resistance data for the via structures of Figure Figure 12 shows an OE device at a step of fabrication according to an embodiment of aspects of the invention;
Figures 13A - 13C show optical micrographs of OE devices of the type of Figure 12 after washing with mixtures of Cyrene and IPA, Cyrene and GBL and Cyrene and PGMEA, respectively;
Figure 14 shows an optical micrograph of a product according to an exemplary embodiment of the invention; and Figure 15 shows an optical micrograph of a product according to an exemplary embodiment of the invention.
Detailed Description of the Drawings Figure 3 shows schematically a method of fabrication of an OE device, specifically a top gate OFET, according to an embodiment of aspects of the invention. Typically, such a method of fabrication may be achieved practically by photolithographic processing, as known to the person skilled in the art.
In contrast to the method of fabrication described above with respect to Figure 1 , a formulation according to an exemplary embodiment of the invention is used, thereby eliminating at least one step of the prior art method. In this way, OE device fabrication complexity and/or cost may be reduced. Furthermore, water-soluble polymers, such as PVA, which may be hygroscopic, are avoided, thereby improving long-term stability of OE devices fabricated according to exemplary embodiments of the invention. In addition, the formulation used comprises a 'green' solvent, thereby improving an environmental profile of the formulation.
At S301 , as described previously with reference to S 01 , a substrate 310 is provided. The substrate 310 may comprise glass, metal, a polymer or an IC, for example. The substrate 310 may include an optional buffer layer (also known as a sublayer) provided on the surface of the substrate 310. The buffer layer may also be known as a planarization layer, provided by a crosslinkable polymer that may improve surface uniformity and/or homogeneity by smoothing imperfections in the surface of the substrate and may provide a chemically insert surface upon which the OE device is fabricated. The buffer layer may comprise crosslinked acrylate polymers or polycycloolefinic polymers, for example. Alternatively, the substrate 310 may comprise polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), for example, which may be processed without a buffer layer.
At S302, as described previously with reference to S102, source and drain electrodes 320 are provided on the surface of the substrate 310, for example by sputtering and photolithography (using mask 1 ). The source and the drain electrodes 320 are typically a metal, for example silver or gold or alloys thereof, or a non-metal. The source and the drain electrodes 320 may be treated with a thiol solution, to adjust work functions of the source and the drain electrodes 320. In this way, injection of charges into an overlaying OSC layer may be improved. Excess thiol solution may be washed away, with thiol binding only to the source and the drain electrodes 320.
At S303, as described previously with reference to S103, an OSC layer 330 is first provided over the source and the drain electrodes 320 and the exposed surface of the substrate 310, for example by spin coating or printing. The OSC layer 330 typically has a thickness of 30 nm. An OGI layer 340 is subsequently provided over the OSC layer 330, for example by spin coating or printing. The OGI layer 340 typically has a thickness of 300 nm. A metal layer 350, for example silver or gold or alloys thereof, is subsequently deposited on the OGI layer 340, for example by evaporation. A photoresist (not shown) is subsequently patterned (e.g. by photolithography) on the metal layer 350 and portions of the metal layer 350 exposed through the patterned photoresist are removed by wet etching. The patterned metal layer 350 provides a gate, such as a thin film transistor (TFT) gate. The patterned metal layer 350 also provides a hardmask (mask 2) against reactive ion etching (RIE) (also known as dry etching, for example using 02 and/or Ar), thereby masking the underlying OGI layer 340, the OSC layer 330 and the source and the drain electrodes 320. Subsequently, RIE removes portions of the OGI layer 340 and the OSC layer 330, that are not masked by the patterned metal layer 350. In this way, a stack 300 comprising the patterned metal layer 350, OGI layer 340, the OSC layer 330 and the source and the drain electrodes 320 is provided on the substrate 310. It should be understood that the stack 300 generally describes a multilayered structure and thus may comprise more or fewer and/or different layers. For example, the stack 300 may comprise those layers at an intermediary stage of fabrication of the OE device. For example, the stack 300 may comprise all layers of the completed OE device. That is, layers included in the stack 300 may change during fabrication, by addition and/or by removal of layers. Sides 341 of the OGI layer 340 and sides 331 of the OSC layer 330 may be thus exposed, for example by the RIE, and may be adversely affected by unsuitable solvents. Further, inter-layer interfaces may also be exposed, for example between the substrate 310 and the OSC layer 330, between the OSC layer 330 and the OGI layer 340 and/or between the OGI layer 340 and the metal layer 350. These inter-layer interfaces may be subject to solvent penetration, as described previously, thereby providing another vector of attack by unsuitable solvents. Other surfaces of the OGI layer 340 and/or the OSC layer 330 may be additionally and/or alternatively exposed.
At S304, in contrast to as described previously with reference to S104, a passivation layer 360 is provided over the stack 300 and the exposed surface of the substrate 310, for example, by coating with a formulation according to an exemplary embodiment of the invention. In detail, the formulation comprises a passivation material and a solvent, wherein the solvent comprises levoglucosenone, dihydrolevoglucosenone or a derivative thereof. In this example, the passivation material comprises a cross-linkable composition, for example bisphenol A novolac epoxy, and the solvent comprises dihydrolevoglucosenone. In this example, the passivation material is dissolved in the solvent. In contrast to the conventional method of fabrication described above with respect to Figure 1 , in which the first passivation layer 180 and the second passivation layer 190 are required for reasons as described above, only the single passivation 360 may be required, according to an exemplary embodiment of the invention. The single passivation layer 360 provides the robustness required for providing environmental, chemical and/or physical protection of the fabricated OE device, similar to the second passivation layer 190 described above, that required also the first passivation layer 180. In this way, OE device fabrication complexity and/or cost may be reduced. Furthermore, water-soluble polymers, such as PVA, which may be hygroscopic, are avoided, thereby improving long-term stability of OE devices fabricated according to exemplary embodiments of the invention. In addition, the formulation used comprises a 'green' solvent, thereby improving an environmental profile of the formulation.
In this example, the passivation material is crosslinked by UV. The passivation layer 360 typically has a thickness of between 300 nm and 2000 nm.
At S305, a positive photoresist mask 361 (mask 3) is provided over the passivation layer 360, similarly to as described previously at S105 with reference to Figure 1.
At S306, a first hole or via is formed through the passivation layer 360 to the patterned metal layer 350, by RIE through the positive photoresist mask 361 , thereby exposing at least a part of the surface of the metal layer 350, similarly to as described previously at S106 with reference to Figure 1.
At S307, residual photoresist mask 381 is removed, similarly to as described previously at S107 with reference to Figure 1.
Since only the single passivation layer 360 may be required, provision of a second passivation layer, such as described previously at S108 with reference to Figure 1 , is not required. In this way, OE device fabrication complexity and/or cost may be reduced. Furthermore, water-soluble polymers, such as PVA, which may be hygroscopic, are avoided, thereby improving long-term stability of OE devices fabricated according to exemplary embodiments of the invention. In addition, the formulation used comprises a 'green' solvent, thereby improving an environmental profile of the formulation.
At S309, a metal gate interconnect 370 is provided through the first hole to the patterned metal layer 350, for example, by sputtering, masking (mask 4) and etching , similarly to as described previously at S107 with reference to Figure 1.
In this way, the OE device may be provided, having a single passivation layer 360.
Hence, in contrast with the conventional process described with reference to Figure 1 , only the single passivation layer 360 may be required. Furthermore, water-soluble polymers, are avoided. In addition, the formulation used comprises a 'green' solvent. In addition, according to this method of fabrication of the OE device, only four masks (mask 1 - mask 4) are required, unlike the conventional process which requires five masks.
Figure 4 shows schematically a method of fabrication of another OE device, according to an embodiment of aspects of the invention. Typically, such a method of fabrication may be achieved practically by photolithographic processing, as known to the person skilled in the art.
In contrast to the method of fabrication described above with respect to Figure 1 , a formulation according to an exemplary embodiment of the invention is used, thereby eliminating at least one step of the prior art method. In this way, OE device fabrication complexity and/or cost may be reduced. Furthermore, water-soluble polymers, such as PVA, which may be hygroscopic, are avoided, thereby improving long-term stability of OE devices fabricated according to exemplary embodiments of the invention. In addition, the formulation used comprises a 'green' solvent, thereby improving an environmental profile of the formulation.
At S401 , as described previously with reference to S101 , a substrate 410 is provided. The substrate 410 may comprise glass, metal, a polymer or an IC, for example. The substrate 410 may include an optional buffer layer provided on the surface of the substrate 410. The buffer layer may also be known as a planarization layer, provided by a crosslinkable polymer that may improve surface uniformity and/or homogeneity by smoothing imperfections in the surface of the substrate and may provide a chemically insert surface upon which the OE device is fabricated.
At S402, as described previously with reference to S103, an OSC layer 430 is first provided over the exposed surface of the substrate 410, for example by spin coating or printing. The OSC layer 430 typically has a thickness of 30 nm.
At S403, an OGI layer 440 is subsequently provided over the OSC layer 430, for example by spin coating or printing. The OGI layer 440 typically has a thickness of 300 nm. In this way, a stack 400 comprising the OGI layer 440 and the OSC layer 430 is provided on the substrate 410. It should be understood that the stack 400 generally describes a multilayered structure and thus may comprise more or fewer and/or different layers. For example, the stack 400 may comprise those layers at an intermediary stage of fabrication of the OE device. For example, the stack 400 may comprise all layers of the completed OE device. That is, layers included in the stack 400 may change during fabrication, by addition and/or by removal of layers. Sides 441 of the OGI layer 440 and sides 431 of the OSC layer 430 may be thus exposed, for example by the RIE, and may be adversely affected by unsuitable solvents. Further, inter-layer interfaces may also be exposed, for example between the substrate 410 and the OSC layer 430 and/or between the OSC layer 430 and the OGI layer 440. These inter-layer interfaces may be subject to solvent penetration, as described previously, thereby providing another vector of attack by unsuitable solvents. Other surfaces of the OGI layer 440 and/or the OSC layer 430 may be additionally and/or alternatively exposed. At S404, a passivation layer 460 is provided over the stack 400 and the exposed surface of the substrate 410, for example, by coating with a formulation according to an exemplary embodiment of the invention. The passivation layer 460 may be provided as described previously with reference to S304.
In detail, the formulation comprises a passivation material and a solvent, wherein the solvent comprises levoglucosenone, dihydrolevoglucosenone or a derivative thereof. In contrast to the conventional method of fabrication described above with respect to Figure 1 , in which the first passivation layer 180 and the second passivation layer 190 are required for reasons as described above, only the single passivation 460 may be required, according to an exemplary embodiment of the invention. The single passivation layer 460 provides the robustness required for providing environmental, chemical and/or physical protection of the fabricated OE device, similar to the second passivation layer 190 described above, that required also the first passivation layer 180. In this way, OE device fabrication complexity and/or cost may be reduced. Furthermore, water-soluble polymers, such as PVA, which may be hygroscopic, are avoided, thereby improving long-term stability of OE devices fabricated according to exemplary embodiments of the invention. In addition, the formulation used comprises a 'green' solvent, thereby improving an environmental profile of the formulation.
Since only the single passivation layer 460 may be required, provision of a second passivation layer, such as described previously at S108 with reference to Figure 1 , is not required. In this way, OE device fabrication complexity and/or cost may be reduced. Furthermore, water-soluble polymers, such as PVA, which may be hygroscopic, are avoided, thereby improving long-term stability of OE devices fabricated according to exemplary embodiments of the invention. In addition, the formulation used comprises a 'green' solvent, thereby improving an environmental profile of the formulation.
In this way, the OE device may be provided, having a single passivation layer 460.
Example 1
Example 1 relates to fabrication of an OTFT device, including a passivation formulation of SU-8 polymer in Cyrene solvent.
20cm x 20cm glass substrates (Corning Eagle XG) were cleaned using sonication for 20 minutes in Deconex (3% w/w in water) followed by rinsing in ultrapure water and dried using compressed air. The substrates were baked at 70°C for 30 minutes in a convection oven. The substrates were then spin coated with a thermally crosslinkable polymer (P1 1 ) (available to the public from NeuDrive Ltd) as a buffer layer (also known as sublayer). After spin coating, the substrates were first placed on a hotplate at 95°C for 2 minutes to softbake, then baked at 150°C for 60 minutes. The final thickness of the P11 layer was measured to be 1 micron.
After the preparation of the P11 sublayer, the substrates were sputter coated with 50 nm of Au, then source and drain electrodes were prepared with a combination of photolithographic and wet etching techniques (potassium iodide and iodine in water etchant composition). The substrates were then scribed into 4 equal sized pieces (10cm x 10cm) and processed at this size for the remainder of the fabrication. After removal of the residual photolithographic resist from the source and drain contact by UV flash exposure and spin developing, the substrates were inspected under an optical microscope and channel length features measured in several areas of the substrate.
Before proceeding with the organic thin-film transistor (OTFT) fabrication, the substrates were treated in a Plasma Etch Inc. PE100 surface treatment system, using an Ar/02 plasma. Each gas was supplied at a concentration of 50 seem and a RF power of 250 W for 65 s.
Prior to spin coating of the organic semiconductor (OSC), a 10 mM solution of 3-fluoro-4- methoxythiophenol in 2-propanol was applied to the surface of the electrodes for 1 minute followed and rinsing in 2-propanol (2 times), followed by drying on a hotplate at 100°C for 1 minute. An OSC formulation of 1 ,4,8,1 1 -tetramethyl bis-triethylsilylethynyl pentacene (T -TES) and 30:70 4- isopropylcyano-polytriarylamine (PTAA): 2,4-dimethyl polytriarylamine copolymer (binder) was formulated at a ratio of 1 part TM-TES to 2 parts binder by weight in 1 ,2,3,4 tetrahydronaphthalene, as for example, described in Example 5 in WO 2012/160383. This was then coated by spin coating at 1250rpm for 60s onto the SD electrodes using a Suss RC12 spinner set at 1250 rpm for 1 minute followed by baking on a hotplate for 60 seconds at 100°C. A solution of 1 part Cytop 809M (Asahi Glass) to 2 parts FC43 solvent (Acros Organics) was spin coated at 1500 rpm for 20 seconds and the sample was baked on a hotplate for 60 seconds at 100°C.
The substrates were then coated with 50 nm of Au by thermal evaporation and the gate electrodes were patterned as before with a combination of photolithography and wet etching. Following this the photoresist on the Au removed by UV flash exposure and development. The OTFTs were electrically tested to check for functionality prior to further processing.
OTFT characterisation OTFTs were tested using a Wentworth Pegasus 300S semi-automated probe station in conjunction with a Keithley S4200 semiconductor parameter analyser. This allowed a statistically significant number of OTFT device measurements to be made on each substrate. The Keithley system calculated the linear mobility according to the equation shown below:
_ dIDS L
Li — —
^ dVGS WCiVDS where L is the transistor length, W is the transistor width, lDS is the drain to source current and Q is the dielectric capacitance per unit area. VDS (drain source voltage) was set at -2V, VGs (gate voltage) was varied from depletion to accumulation (+20V to -30V in 1V steps). The mobility values reported are an average of the 5 highest points in accumulation for each transistor. The data is reported for the channel lengths shown below and is displayed as an average of the devices measured. To exclude devices with gate leakage, a ratio of the gate current to the source-drain current was made at the highest VGs value for a VDS of -2V. If this ratio was below 10 (i.e. the gate current was more than 10% of the source drain current, then the device was excluded from the results). The standard deviation of the mobility values is reported as a percentage of the mean. Turn on voltage of the transistors (Vt0) is defined as the gate voltage point at which the derivative of the logarithm of the drain current with respect to gate voltage is a maximum. It represents the transition point where the device starts to switch from the off state towards the on state. On/off ratio is defined as the maximum current in accumulation (at Vg--30V) divided by the off current in depletion.
Dry etching to pattern the OSC layer
The OSC and dielectric layers were patterned by reactive ion etching (RIE) using an Oxford Plasmalab 800 Plus system with a gas supply of 100 seem 02, at a power of 500W for 120s (pressure was 200 mTorr). The removal of the dielectric and OSC layer was confirmed by inspection under cross polarisers. Areas that were removed showed no sign of crystalline OSC film remaining. The substrate was again electrically tested in order to determine the change in performance due to the dry etching process. Application of the passivation layer (SU-8 in cyrene solvent)
An example passivation formulation was provided containing 1.5 g EPON-SU-8 base polymer (i.e. a passivation material comprising a cross-linkable composition, wherein the cross-linkable composition comprises polymeric precursors comprising epoxy groups) and 16.4 g Cyrene (i.e. dihydrolevoglucosenone). The passivation formulation further contained 0.6 g Triarylsulfonium hexafluoroantimonate (50% solution by weight in propylene carbonate) as a cross-linking agent. That is, the solvent of this passivation formulation comprises 16.4 g Cyrene together with 0.3 g propylene carbonate as a cosolvent. The passivation formulation was spin coated (at 500 rpm for 5 s followed by 3000 rpm for 25 s) onto the dry etched OTFT devices on the substrate. The passivation layer was then softbaked at 95°C for 2 minutes followed by UV exposure 400 mJ/cm2 followed by hardbaking for 10 minutes at 1 15°C to crosslink the film. The sample was inspected under the microscope to confirm that none of the OTFT structures had been affected by the process. The sample was then electrically tested to confirm that the application of the passivation layer to the device had not affected the performance of the OTFT devices. Data were compared for devices tested after the initial fabrication, after the dry etch process and after the passivation layer application to see the effect of each of the processes.
Results
The results of the testing of the OTFTs at different steps of fabrication, particularly, after the initial fabrication, after the dry etch process and after the passivation layer application, include measurement of the average mobility, mobility standard deviation (as a percentage), average on/off ratio and average turn on voltage, as detailed in Tables 10 - 12. The results of the testing after the initial fabrication, after the dry etch process and after the passivation layer application also include transfer and mobility data for individual OTFT devices, as shown in Figures 5 to 7, which relate to Tables 10 - 12 respectively.
Table 10 details electrical test data after Au gate electrode patterning (i.e. after initial fabrication) of the OTFTs. Table 11 details electrical test data after Au gate electrode patterning. Table 12: details electrical test data after application of the passivation layer.
Table 10: Electrical test data after Au gate electrode patterning
Channel
Channel Width Mobility Mobility standard Turn on
Length (microns) (microns) [cm2/Vs] Deviation [%] On/Off ratio voltage [V]
42.9 1005 3.44 6.67% 5.19E+07 1.87
22.9 1068 3.35 4.27% 8.49E+07 1.87
12.9 1 100 3.09 4.05% 1.26E+08 1.87
7.9 1 1 15 2.96 5.92% 1.83E+08 1.87
Table 11 : Electrical test data after dry etch patterning process
Channel
Channel Width Mobility Mobility standard Turn on
Length (microns) (microns) [cm2/Vs] Deviation [%] On/Off ratio voltage [V]
42.9 1005 2.94 8.67% 2.17E+07 2.85
22.9 1068 2.76 7.12% 4.07E+07 2.85
12.9 1 100 2.60 2.59% 6.81 E+07 2.85
7.9 1 1 15 2.57 6.45% 9.33E+07 3.83
Table 12: Electrical test data after application of passivation layer (SU-8 in cyrene solvent)
Channel Channel Mobility Mobility On/Off ratio Turn on Length (microns) Width [cm2/Vs] standard voltage [V] (microns) Deviation [%]
42.9 1005 2.80 5.39% 3.20E+07 1.87
22.9 1068 2.76 6.69% 4.90E+07 2.85
12.9 1 100 2.55 9.07% 8.10E+07 2.36
7.9 1 115 2.48 7.53% 1.12E+08 2.85
Figures 5A and 5B show transfer and mobility curve data, respectively, after gold gate electrode patterning of individual OTFT devices. Each curve represents a different individual OTFT device (L=7.9 pm W=1115 pm device).
Figure 6A and 6B show transfer and mobility curve data, respectively, after dry etch patterning of the individual OTFT devices. Each curve represents a different individual OTFT device (L=7.9 Mm W=1 1 15 pm device). Figures 7A and 7B shows transfer and mobility curve data, respectively, after passivation layer deposition of the individual OTFT devices, using the passivation formulation described above. Each curve represents a different individual OTFT device (L=7.9 pm W=1115 pm device).
Generally, a change arising from a fabrication step of at most 10% in an electrical parameter of Tables 10 - 12 and Figures 5 - 7 is acceptable for making an industrially useful fabrication process. Tables 10 - 12 and Figures 5 - 7 indicate that the electrical parameters have changed by less than 5% when comparing the same OTFT devices and overall have changed on average just over 0.1cm2/Vs. That is, as can be seen from the electrical results, the application of the passivation layer according to an embodiment of the invention has a minimal effect on the electrical characteristics of the OTFT devices.
Figures 8A, 8B, 9A and 9B schematically depict effects of washing the dry etched OTFT devices with different solvents, thereby distinguishing between orthogonal and non-orthogonal solvents. This test demonstrates the extent to which test solvents interact with the dry etched OTFT materials stack and therefore whether a passivation layer material could be coated from the test solvents. A test solvent was dispensed over the entire substrate, left for 20 s and then spun off at 1500 rpm for 20 s followed by baking at 100°C for 60 s.
Figures 8A and 8B show optical micrographs of the OTFT devices of Figure 6 after washing in Cyrene and PGMEA, respectively. Particularly, Figures 8A and 8B show optical micrographs of the OTFT devices of Figure 5 following dry etch patterning and after washing in Cyrene and PGMEA, respectively. As shown in Figure 8A, following Cyrene coating, the gate layer 850A of the OTFT device 800A has not moved at all and the OSC/OGI materials are over the channel area of the OTFT (to be marked in Figures). In contrast, as shown in Figure 8B, following PGMEA coating, the gate layer 850B of the OTFT device 800B has moved due to delamination of the OSC/OGI/gate metal layer (to be marked in Figures). That is, Cyrene is an orthogonal solvent while PGMEA is not an orthogonal solvent. Figures 9A and 9B show optical micrographs of the OE devices of Figure 6 after washing in Cyrene and GBL, respectively. Particularly, Figures 9A and 9B show optical micrographs of the OTFT devices of Figure 5 following dry etch patterning and after washing in Cyrene and GBL, respectively. As shown in Figure 9A, following Cyrene coating, large arrays of devices 900, for example 900A, show all areas are unaffected by the Cyrene. In contrast, as shown in Figure 9B, following GBL coating, structure losses in arrays of the OTFT devices 900, for example the OTFT device 900B in region 99B is observed. That is, Cyrene is an orthogonal solvent while GBL is not an orthogonal solvent. Example 2
Example 2 relates to photopatterning, including a photopattemable formulation of SU-8 polymer in Cyrene solvent. 10cm x 10cm glass substrates (Corning Eagle XG) were cleaned using sonication for 20 minutes in Deconex (3% w/w in water) followed by rinsing in ultrapure water and dried using compressed air.The substrates were baked at 70°C for 30 minutes in a convection oven. The substrates were then spin coated with a thermally crosslinkable polymer (P11 ) (available to the public from NeuDrive Ltd). After spin coating, the substrates were first placed on a hotplate at 95 °C for 2 minutes to softbake, then baked at 150 °C for 60 minutes. The final thickness of the P11 layer was measured to be 1 micron.
After the preparation of the P11 sublayer the substrates were sputter coated with 50 nm of Au, then metal via pad patterns were prepared with a combination of photolithographic and wet etching techniques (potassium iodide and iodine in water etchant composition). After removal of the residual photolithographic resist from the source and drain contact by UV flash exposure and spin developing, the substrates were inspected under an optical microscope.
A formulation was prepared using EPON SU-8 solution 1.5 g EPON-SU-8, 0.3 g Triarylsulfonium hexafluoroantimonate (50% solution by weight in propylene carbonate), 16.4 g Cyrene solvent. This equates to 10% photoinitiator by weight of the SU-8 polymer. The formulation of SU-8 and photoinitiator in Cyrene was spin coated at 200 rpm for 10 s followed by 1000 rpm for 30 s and then baked for 2 minutes at 95°C on a hotplate to form a dry film. The film was then exposed to UV (365nm wavelength) through a photomask (VIA MASK) using an EVG 6200 mask aligner in proximity mode (5 micron gap) to selectively expose parts of the film to light. The VIA MASK was aligned with the first metal layer to ensure via holes were patterned over the metal bottom pads. After exposure the film was post exposure baked at 95 °C for 2 minutes. The film was flooded with Microposit™ EC solvent (Rohm and Haas) for 30 s, then spun at 1000 rpm with developer rinse for 5 s followed by 2500 rpm spin for 30 s to dry the film. Figure 10 shows an optical micrograph of via structures, particularly finished via chains, formed by the photopatterning. The via structures formed in the material was imaged to check that they were formed correctly. The substrate was then sputter coated with 50 nm of Au metal and this layer was patterned by photolithography and wet etching to form the top metal pad of the via structure. The dimensions of the vias were measured using a microscope and camera with image analysis software (in this image the vias were between 15 and 16 microns). The smallest via chains formed were 6 microns.
Figure 11 shows resistance data for the via structures. The vias were electrically tested using an LCR meter (Agilent) to measure the resistance between the contact pads of the via chain. Results are shown in the graph for via chains containing different numbers of via connections. As can be seen from the results there is a low resistance connection for via chains up to 50 connections with small vias contributing 3.3 Ohms per via and larger diameter vias contributing 2.8 Ohms per via. This demonstrates that the photopatternable SU-8 formulation in Cyrene can be imaged effectively to form high resolution via structures suitable for interconnecting TFTs in electronic devices.
Example 3
Example 3 relates to washing dry etched OTFT devices with different solvent mixtures (i.e. further including a cosolvent), thereby distinguishing between orthogonal and non-orthogonal solvent mixtures.
Figure 12 shows an OE device 1200A at a step of fabrication according to an embodiment of aspects of the invention and Figures 13A - 13B show optical micrographs of OE devices of the type of Figure 12 after washing with solvent mixtures of Cyrene and IPA, Cyrene and GBL, and Cyrene and PGMEA, respectively.
In more detail, Figure 12 shows the OE device 1200 at the step of fabrication corresponding to the step S303, as described above with reference to Figure 3. Like reference signs denote like features, description of which is not repeated for brevity. Briefly, the substrate 1210 with stack 1200 was produced using the stack etch, as described above, in an Oxford Plasmalab 800Plus RIE system. The etch takes off the OSC/OGI layers and over-etches about 300-400 nm into the P11 sublayer. Solvent mixtures, as detailed in Tables 13A - 13B respectively, were deposited on one quarter of different parts of the substrate 1210 containing the stack 1200, left for 20 s, spun at 500 rpm for 10 s and then spun at 1500 rpm for 20 s to remove the solvent. The substrate 1210 plus stack 1200 structures were baked on a hotplate for 1 minute at 100 °C, to dry off the solvent mixture.
In more detail, Figure 13A shows the optical micrograph of the OE device 1300A, following washing with IPA 100 wt.%. OSC crystallinity is observed up an edge of the metal layer 1350A, indicating that IPA does not adversely affect the OSC layer 1330A. Furthermore, IPA improves wetting, as described previously. Table 13A summarises results of washing with different solvent mixtures of Cyrene and IPA, in which the tested mixtures were found to not adversely affect the OSC layer 1330A. Table 13A: Solvent mixtures and results for Cyrene and IPA Cyrene !PA
(wt.%) (wt.%) Result
95 5 Pass
90 10 Pass
80 20 Pass
60 40 Pass
0 100 Pass
In more detail, Figure 13B shows the optical micrograph of the OE device 1300B, following washing with a solvent mixture consisting of Cyrene 80 wt.% and GBL 20 wt.%. Undercutting between the metal layers 1320B and 1350B is observed, possibly due to dissolution of the OSC layer 1330B, indicating that GBL does adversely affect the OSC layer 1330B. Table 13B summarises results of washing with different mixtures of Cyrene and GBL, in which the tested mixtures were found to adversely affect the OSC layer 1330B at solvent mixtures including GBL at 20 wt.% GBL and above.
Table 13B: Solvent mixtures and results for Cyrene and GBL
Figure imgf000067_0001
In more detail, Figure 13C shows the optical micrograph of the OE device 1300C, following washing with a solvent mixture consisting of Cyrene 80 wt.% and PG EA 10 wt.%. Damage of the OSC layer 1330C is observed. Table 13C summarises results of washing with different mixtures of Cyrene and PGMEA, in which the tested solvent mixtures were found to adversely affect the OSC layer 1330C at solvent mixtures including PGMEA at 10 wt.% PGMEA and above.
Table 13C; Solvent mixtures and results for Cyrene and PGMEA
Cyrene PGMEA
(wt.%) (wt.%) Result
95 5 Pass
90 10 Fail
80 20 Fail
60 40 Not tested
0 100 Not tested Example 4
Example 4 relates to a product 14000, particularly a decoder circuit, according to an exemplary embodiment of the invention.
Figure 14 shows an optical micrograph of the product 14000, including a plurality of OE devices 1400. Like reference signs denote like features, description of which is not repeated for brevity. Particularly, Figure 14 shows a gate interconnect metal track 1470A crossing a source and drain metal electrode track 1420A with the SU8 passivation layer 1460 (spun from Cyrene and photopatterned, described previously) isolating the tracks from each other. Metal 1470A (50 nm Au) was sputtered on top of the SU8 and patterned using photolithography and wet etching as for the source and drain metal electrode track metal 1420A.
In this way, the passivation layer 1460 also serves as an interlayer dielectric so that metal tracks 1420A and 1470A may be routed in the circuit on different layers without short circuiting, for example.
Example 5
Example 5 relates to measurements of surface tension of mixtures of solvents, particularly a first mixure of IPA and Cyrene and to a second mixture of hexanol and Cyrene. Example 5 also relates to OTFT using the second mixture of hexanol and Cyrene. Measurement of surface tension - drop shape analysis
Drop shape analysis was performed on single solvents and solvent mixtures comprising Cyrene to determine their surface free tension. Pendant drop analysis was carried out using a Kruss DSA30S. Measurements were conducted using a syringe of solvent to form a drop at the end of a blunt needle suspended near to a cuvette filled with the test solvent. This was done to reduce the effect of evaporation on the resulting surface tension values. A drop was formed at the end of the needle, 10-30 pL in volume depending on the solvent under test, close to the point where it would drop off the end of the needle. The drop was then increased in size in 0.1 pL increments until it dropped from the end of the needle. Measurements of surface free tension were obtained using the camera of the DSA30S to record images of the drop shapes, which were then processed via fitting to the Young Laplace equation. A minimum of three measurements were carried out for each solvent to ensure a consistent reading. Results are shown in Table 14 for the single solvents. Deionised (Dl) water and propylene glycol monomethyl ether acetate (PGMEA) were used as test solvents to check the accuracy of the data vs literature values.
Table 14: Surface free tension values of various solvents. Dl water 72.43 ± 1.34 mN/m
PGMEA 28.24 ± 0.96 mN/m
Cyrene 47.36 ± 0.56 mN/m
Table 15: Surface free tension values of Cyrene/IPA solvent mixtures.
Figure imgf000069_0001
Table 16: Surface free tension values of Cyrene/hexanol solvent mixtures.
Figure imgf000069_0002
As can be seen from the surface tension data above (Tables 15 and 16), it is possible to reduce surface tension of Cyrene through mixing with a co-solvent such as IPA or Hexanol. Hexanol may be preferred over IPA in some coating formulations due to its higher boiling point which may reduce its evaporation rate during coating.
OTFT devices were made using the process as described in Example 1 but with the following changes. The equipment used to dry etch pattern the OSC and dielectric layers was changed to an Aurion Gen2 RIE system with process pressure of 0.07 hPa, 02 gas at 150 seem, power 2250 W, temperature 21 °C, etch time 25s. A passivation layer formulation was prepared using EPON SU-8 dissolved at 12.5% by weight solids SU8 in mixed solvent of Cyrene/hexanol (9:1 by weight). As in Example 2, a Triarylsulfonium hexafluoroantimonate photoinitiator (50% solution by weight in propylene carbonate) was added at 10% by weight of the SU-8 polymer. The passivation layer formulation was spun at 500rpm 10s followed by 1250rpm for 30s, baked 2 min at 95 °C to give a layer thickness of 850nm. The passivation layer was exposed through a photomask with 100 mJ/cm2 (i-line) UV light using an EVG 6200 mask aligner in hard contact mode. Post-baking and development was as in example 1 and the features produced by the patterning were well defined as can be seen in Figure 15. An interconnect metal (50nm Au) was then deposited and patterned as described in Example 4. The devices were tested electrically and the results shown in Table 17. Figure 15 shows an optical micrograph of a product 15000 according to an exemplary embodiment of the invention. Particularly, Figure 15 shows a photograph of 4, 6, 8, and 10 micron CD bars (1510, 1520, 1530 and 1540 respectively) for the passivation layer made using a mixed solvent system of Cyrene and hexanol (9: 1 ).
Table 17: OTFT results for devices processed with an SU8 passivation layer spun from Cyrene/hexanol mixed solvent system
Figure imgf000070_0001
As can be seen from the results, the mixed solvent system of Cyrene and hexanol can be used as a coating solvent in a passivation layer. Other solvent systems such as pentanol and butanol were also miscible with Cyrene so could be suitable for a mixed solvent system. Example 6 (example of polyvinylphenol used as passivation layer)
Example 6 relates to use of poly (4-vinvlphenol) (PVP) as a passivation layer.
In this example, an OTFT device was processed as in Example 1 except that the dry etch patterning equipment and process used was the same as in Example 5 and the passivation layer used was poly (4-vinylphenol) (PVP). The PVP passivation layer formulation was formulated at 10% by weight in Cyrene with hydroxymethyl benzoguanamine (HMBG) as crosslinker (2% by weight in cyrene). The formulation was spun at 2500 rpm for 30 s on top of a dry etch patterned OTFT to form a passivation layer. The PVP layer was measured at 1 .5 microns thickness using a stylus profilometer. The substrate was baked at 95°C for 2 min on a hot-plate and then further baked for crosslinking for 3 hours at 130 C in a vacuum oven. The devices were electrically tested after the dry etching and after the PVP passivation layer process.
Table 18: electrical test data after OTFT dry etch patterning process.
Channel
Channel Width Mobility Mobility standard On/Off Turn on
Length (microns) [cm2 Vs] deviation [%] ratio voltage [V] (microns) 42.9 1005 3.12 9.51 % 8.04E+06 5.79
22.9 1068 2.98 9.57% 1.43E+07 5.79
12.9 1100 2.81 10.67% 2.51 E+07 5.79
7.9 1115 2.80 8.42% 3.29E+07 6.77
Table 19: electrical test data after application of passivation layer (PVP in cyrene solvent).
Figure imgf000071_0001
It can be seen from the results (Tables 18 and 19) that the PVP in cyrene can be applied successfully as a passivation layer. Optical images showed no damage to the OTFT devices due to application of the layer. The reduction in mobility between the post dry etch test and after the passivation layer is likely due to the 3 hour bake at 130 °C affecting the thiol material on the source-drain contact of the transistors.
In summary, the invention provides a formulation for providing passivation and/or photopatterning layers for use in fabrication of organic electronic devices that may be provided, for example directly, on organic layers, such as OSC layers and/or OGI layers and/or a stack comprising one or more of these layers, without adversely affecting the organic layers. The formulation comprises a solvent comprising levoglucosenone or dihydrolevoglucosenone or a derivative thereof. Further, the invention provides a method of fabrication of organic electronic devices, using such a formulation, having reduced complexity and/or cost. Further, the invention provides an organic electronic device, including a layer provided by such a formulation, that has improved long-term stability. Although preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims. For example, the square pad and frame corresponding with the square aperture may be modified to be a circular pad and frame to correspond with a circular aperture. For example, the gap may be provided within the aperture rather than outside and adjacent to the aperture.
Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All of the features disclosed in this specification (including any accompanying claims and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

I . A flowable formulation for depositing a passivation layer on an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer, wherein the formulation comprises a passivation material and a solvent;
wherein the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof.
2. The formulation according to claim 1 , wherein the derivative has Hansen solubility parameters that are within 3 MPa½ of those of levoglucosenone.
3. The formulation according to any previous claim, wherein the passivation material comprises a cross- linkable composition.
4. The formulation according to claim 3, wherein the cross-linkable composition comprises monomeric, oligomeric and/or polymeric precursors.
5. The formulation according to claim 4, wherein the monomeric, oligomeric and/or polymeric precursors comprise an epoxy group.
6. The formulation according to any of claims 4 to 5, wherein the monomeric, oligomeric and/or polymeric precursors comprise (alkyl)acrylate repeat units.
7. The formulation according to any of claims 4 to 6, wherein the monomeric, oligomeric and/or polymeric precursors are cross-linkable via a thiol - ene or a thiol (alkyl)acrylate reaction.
8. The formulation according to any of claims 4 to 7, wherein the monomeric, oligomeric and/or polymeric precursors are cross-linkable via a thermal azide alkyne cycloaddition reaction.
9. The formulation according to any of claims 3 to 8, wherein the cross-linkable composition comprises a polyimide.
10. The formulation according to any of claims 3 to 9, wherein the cross-linkable composition comprises a cycloolefinic polymer.
I I . The formulation according to any of claims 3 to 10, wherein the cross-linkable composition comprises a substituted poly(vinylphenol) derivative.
12. The formulation according to any previous claim, comprising at least one of a cross-linking agent, a photoacid generator, a hardening agent, an antioxidant agent, a surfactant, and a filler.
13. The formulation according to any previous claim, comprising a cosolvent.
14. A method of fabricating an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator
(OGI) layer, wherein the method comprises:
providing a passivation layer on at least a part of the organic layer by depositing a formulation according to any of claims 1 to 13 thereon and removing the solvent.
15. An organic electronic (OE) device comprising an organic layer and a passivation layer directly thereon, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer and wherein the passivation layer comprises a cross-linked product of a cross-linkable composition according to any of claims 3 to 13.
16. A product comprising an organic electronic (OE) device fabricated according to claim 14 and/or an OE according to claim 15.
17. A flowable formulation comprising a photopatterning material and a solvent;
wherein the solvent comprises levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof.
18. Use of a solvent comprising levoglucosenone and/or dihydrolevoglucosenone and/or a derivative thereof in a method of fabricating an organic electronic (OE) device comprising an organic layer, wherein the organic layer is selected from an organic semiconductor (OSC) layer and an organic gate insulator (OGI) layer.
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