WO2010093237A1

WO2010093237A1 - Optoelectronic device and method for fabricating such device

Info

Publication number: WO2010093237A1
Application number: PCT/NL2010/050060
Authority: WO
Inventors: Herbert Lifka; Petrus Marinus Martinus Cornelus Bressers; Cristina Tanase; Peter Van De Weijer; Antonius Maria Bernardus Van Mol
Original assignee: Nederlandse Organisatie Voor Toegepast- Natuurwetenschappelijk Onderzoek Tno; Koninklijke Philips Electronics N.V.
Priority date: 2009-02-11
Filing date: 2010-02-10
Publication date: 2010-08-19

Abstract

The invention relates to an optoelectronic device comprising at least a first electrode (2), at least a second electrode (4) and organic electroactive material (3) wherein at least part of the organic electroactive material is located between the first electrode and the second electrode, wherein in at least a part of the optoelectronic device said first electrode and said second electrode protrude relative to at least part of the organic electroactive material, and wherein electrically insulative material (5) is present in a space defined by the protruding parts of the first electrode and the second electrode.

Description

Title: Optoelectronic device and method for fabricating such device

The invention relates to an optoelectronic device and to a method for fabricating such device.

Organic optoelectronic devices, such as organic light emitting diodes (OLED's) or organic photovoltaic cells (OPV), generally contain an organic electroactive material and at least two electrodes, which are usually made of a metallic material or a conductive oxide. The electroactive material is usually situated between the electrodes. For an efficient operation of an optoelectronic device, it is desired that efficient transport of charges takes place across an interface of organic electroactive material and electrode material. Protection of the organic electroactive material against environmental conditions such as oxygen and/or water (moisture) is very important in organic optoelectronic electronic devices, because the organic material is prone to deterioration upon contact with water and/or oxygen, which leads to underperformance of the optoelectronic device. The substrate usually protects the device on one side (the side engaging the substrate), which side is generally referred to as the 'bottom side', regardless of the actual orientation of the device. To this end, the substrate usually comprises a material that is essentially impermeable to oxygen and/or water, e.g. glass or metal. Those parts of the device that are not protected by the substrate, e.g. the opposite side of the bottom side (which side is generally referred to as the 'top side', regardless of the actual orientation of the device), are usually provided with a material that protects those parts. Such a material is essentially impermeable to oxygen and/or water, a so-called barrier coating. It is preferred that such a barrier coating provides an essentially complete sealing of the device. However, there are generally one or more locations on an organic optoelectronic device where an electrode (or a material that is conductively connected thereto) extends through the coating to serve as an external contact (the 'electrode-lead-out'). To avoid shortcuts between the electrodes at such locations, part of the electroactive material is usually kept free from contact with electrode material. Accordingly, those parts of the electroactive material which are not in contact with electrode material, and which are close to the outlet of the electrode through the coating, are particularly vulnerable to the outside environment.

Preferred materials for a barrier coating on optoelectronic devices, in general, are inorganic barrier coatings, such as a metallic material, a silicon carbide, a silicon nitride or a silicon oxide coating. Such materials are suitable because of their low permeability towards water and/or oxygen.

However, conventional methods of applying such materials may involve coating conditions that adversely affect the organic electroactive material. For example, the organic material may be adversely affected by exposure to a high temperature, an oxidative environment, a reductive environment, and/or an environment containing water. Accordingly, deterioration of the organic material may occur during application of such a barrier coating, leading to poorer quality of the device, e.g. a reduced light intensity in case of a LED, a reduced photo-sensitivity in case of a detector or a photovoltaic cell, a reduced efficiency, a loss of image resolution in case the device is a device to display an image, or a reduced lifetime of the device. Further, in conventional devices, metallic materials may cause electrical shortcuts between the electrodes proximal to the organic electroactive material, due to the design of the devices.

It is an object of the present invention to provide a novel organic optoelectronic device wherein the organic electroactive material is adequately protected from water and/or oxygen. It is further an object to provide a novel method for preparing an organic electronic device. In particular, such a method is relatively simple to be carried out on an industrial scale.

One or more other objects which may be met in accordance with the invention will follow from the remainder of the description and/or the claims.

The inventors have now realized that one or more objects are met by an optoelectronic device, wherein a specific material is applied at a specific part of the device in a specific configuration.

Accordingly, the present invention relates to an optoelectronic device comprising at least a first electrode 2, at least a second electrode 4 and electroactive material 3, wherein

— at least part of the electroactive material 3 is located between the first electrode 2 and the second electrode 4;

— in at least a part of the optoelectronic device said first electrode 2 and said second electrode 4 protrude relative to at least part of the electroactive material 3, and wherein

— electrically insulative material 5 is present in a space defined by the protruding parts of the first electrode 2 and the second electrode 4.

An optoelectronic device according to the invention preferably comprises organic electroactive material.

Further, the present invention relates to a method for fabricating an optoelectronic device comprising electroactive material 3, comprising

— providing a first electrode 2;

— depositing electrically insulative material 5 on a first electrode 2 thereby partly covering the first electrode 2 with electrically insulative material 5; thereafter

— depositing electroactive material 3 on a part of the first electrode 2 that has not been covered by the electrically insulative material 3; thereafter

— depositing a second electrode 4 on at least part of the electroactive material 3 and on at least part of the electrically insulative material 5. In a method for fabricating an optoelectronic device according to the invention, the electroactive material preferably comprises organic electroactive material.

The term "or" as used herein means "and/or" unless specified other wise.

The term "a" or "an" as used herein means "at least one" unless specified other wise.

With the term "optoelectronic device" is meant an instrument that is or uses an electrical-to-optical transducer or an optical-to- electrical transducer. Examples of organic optoelectronic devices are organic light emitting diodes (OLED's) or organic photovoltaic cells (OPVs).

The term "electroactive" is used herein for an electrically conductive material which is (1) capable of converting a non-electric form of energy into electric energy or vice versa, (2) capable of absorbing or emitting light, and/or (3) capable of changing color, and/or reflectivity and/or transmittance.

Generally, an electroactive material is capable of acting as a (semi-)conductor for electrical energy. In particular an electroactive material in a device of the invention is capable of converting electromagnetic radiation (such as UV, visible light or IR) into electrical energy or converting electrical energy into electromagnetic radiation.

In an optoelectronic device according to the invention, the electrodes are in general partially separated by the electroactive material 3 and partially by the electrically insulative material 5. In general, the electrically insulative material 5 is partially in contact with the outside environment and/or with a barrier coating 6 that protects the device. Due to the presence of the electrically insulative material 5, shortcuts between the electrodes 2 and 4 are avoided. Moreover, the electrically insulative material 5 serves as a separator between the electroactive material 3 and the outside environment and/or it serves as a separator between the electroactive material 3 and barrier coating 6 that shields the device. Exposure of the electroactive material 3 to the outside environment or application of a barrier coating 6 onto the electroactive material 3 is undesired as it may lead to damage to the electroactive material 3.

If an optoelectronic device according to the invention comprises a barrier coating 6, suitable coatings are, in general, inorganic barrier coatings. Examples of suitable inorganic barrier coatings are coatings comprising one or more compounds selected from the group of metals, metal oxides, silicon carbide, silicon nitride, silicon oxynitrides and silicon oxide.

The electrically insulative material 5 may also be capable of acting as an effective barrier against components of the environment surrounding the device, e.g. one or more compounds selected from the group of oxygen, nitrogen, CO2, water, N2O, O3 and volatile organic compounds (e.g. ethanol, methanol, toluene). With an effective barrier against a specific compound is in particular meant a barrier with a permeability of 1 mg/m².day or less, of 0.1 mg /m².day or less, or of 1 μg/m².day or less. The permeability may be determined as described in US2006/147346.

In particular in case the electrically insulative material 5 as well as the other components that are surrounding the electroactive material 3 are capable of acting as an effective barrier, the device may be free of a barrier such as a barrier coating 6.

It is also an advantage that, at the electrode-lead-out, the two electrodes are separated by a non- conductive material instead of the (semi-)conductive electroactive material 3. This opens the possibility to grow a metallic sealing layer around the device via electrodeposition, if desired, without creating a metallic shortcut between the electrodes, and without depositing the layer directly on the electroactive material 3. An advantage of such a metallic sealing layer is that it can serve as an effective barrier coating 6 against components of the environment and protect the device against mechanical forces. It is in particular an advantage that such a metallic barrier coating 6 can be applied via electrodeposition, because layers obtained via this method can have less pinholes than layers obtainable via other methods, such as sputtering, chemical vapour deposition, and physical vapour deposition. An advantage of metal over some other materials for protecting the device, is that metal is generally relatively ductile, such that the device retains its flexibility, in case it is a flexible device.

Such a metallic layer further has the advantage that it provides strength to the external contact of the electrode. Welding, soldering, clamping and gluing can be performed more easily on the enforced metal of the contact. A further advantage of the possibility to apply a metallic barrier material (such as a coating or other layer) via electrodeposition is that it enables the fabrication of a plurality of devices on one substrate (see also the embodiment represented in Figure 6), wherein the electrical contact(s) between these devices are provided with an electrodeposited metallic material. Such electrodeposited material is in particular advantageous in that it results in a strengthened electrical contact. From a manufacturing point of view it is further advantageous in that no separate procedure is necessary to strengthen the electrical contact(s) between the devices

It is a further advantage that such metallic layer may protect inner layer(s) of the electrode, in case the electrode comprises multiple layers. Accordingly, it is possible to use one or more (inner) layers in the electrode which are not corrosion resistant.

Figure 1 (ref) represents a schematic cross section of a known (organic) optoelectronic device. Such a device usually comprises a first electrode 2 (usually an anode), a second electrode 4 (usually a cathode), and (organic) electroactive material 3. Components 2, 3 and 4 are usually (at least partially) applied on a substrate 1. Further, a barrier coating 6 may be present, covering the assembly of at least substrate 1, electrodes 2 and 4, and electroactive material 3, such that the assembly is essentially sealed. The cross section in Figure 1 shows a plane in the device comprising the outlet of one of the electrodes. This cross section demonstrates how the protruding electroactive material 3 between the electrodes 2 and 4 results in a high exposure of the protruding electroactive material 3 to the environment. Or, in the case that the barrier coating 6 is present, it demonstrates that the protruding electroactive material 3 is in direct contact with the barrier coating 6. As the other electrode 4 already has a surface at the exterior of the device, an external connection to that electrode is straightforward and is not shown in the cross-sectional view of Figure 1.

Figure 2 represents a schematic cross section of an (organic) optoelectronic device according to the invention, the cross section being a plane in the device comprising the outlet of one of the electrodes. Alike figure 1, it comprises the assembly of a first electrode 2, a second electrode 4, and electroactive material 3. Components 2, 3 and 4 are usually (at least partially) applied on a substrate 1. In the embodiment shown in Figure 2, a barrier coating 6 around the assembly is absent. It is shown that both electrodes 2 and 4 protrude relative to the organic electroactive material 3. In the space defined by the protruding parts of the first electrode 2 and the second electrode 4 an electrically insulative material 5 is present, which at least in an embodiment without a surrounding barrier coating 6 in general is a barrier material against water and/or oxygen. It avoids electrical shortcuts between the electrodes and shields the organic electroactive material 3 from the environment at the outside of the device. The line 5a represents the thickness of the electrically insulative material 5, and the line 5b represents its length. Figure 3 represents the cross section of the (organic) optoelectronic device of Figure 2, with the difference that it comprises a barrier coating 6, which may in particular be a metallic barrier coating. This specific embodiment displays the advantage of the invention that, due to the presence of the non-conductive material between electrode 2 and electrode 4, an electrochemically grown metallic barrier coating 6 does not create a metallic shortcut between the electrodes. Figure 4 represents the cross section of an optoelectronic device according to the invention, comprising additional elements 7 and 8.

Element 7 may be a barrier layer between the substrate 1 and the assembly of electrodes and electroactive material. Such a barrier layer is non-conductive and may be selected from the same group of materials as those mentioned elsewhere herein for the barrier coating 6 (with the exclusion of conductive materials, such as metallic materials) or for the electrically insulative material. In case such a barrier layer 7 should be transparent, it is preferably formed from a transparent silicon nitride, transparent silicon oxide, transparent silicon oxynitride, transparent silicon carbide or a transparent metal oxide. It is also possible to provide a stack from a barrier material such as SiN and an organic layer, layers of both materials alternating in the stack. Alternatively, a stack may also comprise layers of barrier materials, e.g. SiN-SiO-SiN. Material 8 may be a buffer layer between electrode 2a and organic electroactive material 3. Material 8 in particular comprises an organic material that is an electrical insulator, e.g. non-conductive polymers. Material 8 may be deposited before or after material 5.

Further, in the embodiment represented by Figure 4, electrode layer 2 is divided into the sublayers 2a and 2b. Sublayer 2a is a part of electrode 2, which part serves as an external contact and may be non-transparant. In particular, 2a comprises a metal. Sublayer 2b represents a transparent conductor material, in particular a material comprising indium-doped tin oxide (ITO). Further, a metal shunt may be present between electroactive material 3 and sublayer 2b. The shunt may comprise tracks of material 2a to reduce the effective resistance of sublayer 2b. The shunt may further comprise buffer layer 8, separating the tracks of material 2a from the electroactive material 3, thereby reducing the risk on shortcuts with the electrode 4. Figure 5 represents a cross section of a further embodiment of the invention.

Figure 6 displays a configuration of a plurality of electroactive devices, wherein on one substrate more than one OLED devices are present. Such configuration, wherein the devices are arranged in essentially the same plane and wherein the devices are connected in serial, in parallel or in combinations thereof, are also known as "in-plane connecting devices" (Figure 6 and the example). An advantage of in-plane connecting devices is a reduction of the current in the OLED devices and a reduction of the risk of shortcuts. Accordingly, the invention also relates to a structure comprising two or more optoelectronic devices as described herein, wherein one or more electrical connections exist between at least two of the optoelectronic devices. In a device according to the invention, the electroactive material is generally completely enclosed by a combination of the following components: an anode 2, a cathode 4, electrically insulative material 5, and a substrate 1. In this way, the electroactive material can be adequately protected against environmental conditions.

In particular, in a device as exemplified in Figure 4, the electroactive material is completely enclosed by a combination of the following components: an anode 2, a cathode 4, electrically insulative material 5, a non- conductive barrier layer 7 and a buffer layer 8.

Usually, the electroactive material 3 is fully sealed in the device, i.e. surrounded by material that is essentially impermeable to water (vapour) and oxygen. It may in particular be sealed by the combination of a barrier layer 6 or stack on the device and the electrically insulative material 5 present in a space defined by the protruding parts of the first electrode and the second electrode.

At least in some embodiments, the components enclosing the electroactive material 3 result in an effective sealing of the electroactive material such that it is adequately protected, without requiring a separate barrier coating 6 surrounding said components in order to seal the device to obtain the desired protection for the electroactive material 3.

Though, if desired the device may be provided with a barrier coating 6. As indicated above, an optoelectronic device according to the invention may comprise a substrate 1, serving as a carrier material for at least the electrodes 2 and 4, the electroactive material 3 and the electrically insulative material 5. The thickness of the substrate can be chosen within wide ranges, e.g. within the ranges described in the prior art identified herein. In particular, the thickness of the substrate may advantageously be chosen in the range of 0.01-20 mm, in particular in the range of 0.01-5 mm, more in particular in the range of 0.01—2 mm.

Suitable substrate materials are for example glass or plastic, e.g. polyethylene or polyethylene terephthalate. The substrate can be a composite, such as a multilayer laminate.

In an embodiment, the substrate material is transparent. It may for example comprise glass or a transparent plastic, e.g. a transparent plastic selected from the group of polycarbonates, cyclic olefinic polymers (e.g. Zeonex, Topas), polymethyl pentenes (e.g. TPXTN), polymethyl methacrylates (PMMA), polystyrenes (PS), polyamides, polyvinyl chlorides, polyethyl terephthalates, polypropenes, styrene butadiene styrene copolymers, cellulose polymers, polyethylenes, polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and polynorbornenes.

In a preferred embodiment, the substrate is flexible, so that it can be bended into a particular shape, whilst a device comprising such substrate remains functional.

An optoelectronic device according to the invention comprises at least a first electrode 2 and at least a second electrode 4. In an embodiment, the first electrode is an anode and the second electrode is a cathode. Usually, the electrodes are present as a layer, which means that the size in one dimension (thickness) is considerably less than the size in the other dimensions (length, width), e.g. at least 10 times less.

The thickness of the electrode layers can be chosen within wide ranges, e.g. within the ranges described in the prior art identified herein. In particular, the thickness the electrode layers may advantageously be chosen in the range of 10—50000 nm, in particular in the range of 100—500 nm.

In general, electroactive material 3 in an optoelectronic device according to the invention is present as a thin layer, which means that the size in one dimension (thickness) is considerably less than the size in the other dimensions (length, width), e.g. at least 10 times less, or even 1000 times less. For instance, such a layer may have a thickness of 10 nm up to 10000 nm.

The electroactive material 3 in a device according to the invention may be a polymeric organic electroactive compound, a non-polymeric organic electroactive compound or an inorganic electroactive compound. In an embodiment, the electroactive material 3 is selected from the group of organic light- emitting compounds and organic photovoltaic compounds.

In principle a device according to the invention may comprise any organic electroactive compound. Various kinds of such compounds are known in the art, for example electroactive polymers and non-polymeric compounds. In an embodiment, the electroactive material is a polymer selected from the group of polyarylene compounds, poly(paraphenylene vinylene) compounds, polyfluorene compounds, polyacetylene compounds, polythiophene compounds, polypyrroles, polyanilines, including derivatives of said polymers (in particular alkyl, aryl and alkoxy derivatives), copolymers of said polymers and said polymers which have been derivatized with a dye.

In a photovoltaic cell, such polymers have been found very suitable as electron- donating compound. The photoactive layer may comprise a fullerene and/or a fullerene derivative, preferably [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), as electron-accepting compound. In an embodiment, the electroactive material comprises a material selected from the group of non-polymeric materials, mixtures and stacks of polymers and non-polymeric compounds, and quantum-dot embedded organic materials. In the case of an OLED, the electroactive layer 3 comprises an electroluminescent compound. An OLED is herein understood to mean a light emitting diode whose photoactive layer consists at least substantially of at least one (semi)conductive electroluminescent organic compound or composition. A polymeric light emitting diode (hereinafter called PLED) is herein understood to mean an OLED whose photoactive layer consists at least substantially of at least one (semi) conductive electroluminescent organic polymer (including polymer mixtures) or an OLED whose photoactive layer consists at least substantially of at least one (semi)conductive organic polymer (including polymer mixtures) and of at least one other organic compound (for instance a single compound), which is electroluminescent.

Preferred electroluminescent compounds are polyarylenes, more preferably poly(paraphenylene vinylene) compounds (PPV compounds), polyacetylenes, polyanilines, polythiophenes, polyfluorenes, polyvinylcarbazoles, polyphenylene compounds polyfluorene compounds polypyrroles, polyanilines, including derivatives of these polymers (in particular alkyl, aryl and alkoxy derivatives), copolymers of these polymers and mixtures thereof.

Besides a polymeric (which term as used herein includes "oligomeric"), a non-polymeric electroluminescent compound may also be used, such as a non-polymeric electroluminescent dye. Examples of such compounds are monomers and other non-polymerized molecules with conjugated bonds. Often, such compounds have a relatively low molecular weight compared with polymers. In general, such compounds have a molecular weight of 20,000 g/mol or less, in particular of 10,000 g/mol or less. Also stacks of organic materials can be used, e.g. stacks comprising one or more organic materials selected from the group of (planarising) hole-injection material, hole-blocking material, electroluminescent material, electron-blocking material and/or electron-injecting material. Any combination of these stacks or even multiple repetions of these stacks is within the scope of this invention.

In an embodiment, the electroactive material 3 may also be used as part of the first electrode to get a homogeneous area coverage of that first electrode. In a further embodiment of the device, also metal shunts e.g. comprising aluminium, can be applied on at least part of the first electrode. These can then be partially covered with an insulating non-barrier layer, e.g. an organic layer as e.g. novolak.

In an embodiment, the OLED emission spectrum has at least two maxima. An OLED with more than one maximum can be provided for in that the OLED contains at least one electroluminescent active layer which comprises at least two different electroluminescent functionalities. Thus, for instance, the photoactive layer can contain a mixture of two different electroluminescent compounds. Examples include mixtures of the polymers mentioned herein, mixtures of the polymers mentioned herein with other electroluminescent compounds, for instance non-polymeric conjugated compounds, and copolymers with different electroluminescent segments. Suitable examples thereof are described in WO 2005/001945, of which the contents with respect to the suitable electroluminescent compounds are incorporated herein by reference, in particular the part from page 10, line 10 to page 14, line 17.

In an embodiment, the optoelectronic device is an organic photodiode, e.g. a polymeric photodiode. An organic photodiode is herein understood to mean a photodiode of which an electroactive layer comprises at least one (semi)conductive organic compound (including a composition thereof), e.g. a polymer. The photodiode preferably comprises an electron- donating organic material (p-type material) and an electron- accepting organic material (n-type material). The photodiode can comprise as an electroactive layer a material (such as a conductive polymer) which exhibits photoconduction when it is under an electric potential.

The photodiode may be a photovoltaic cell, which, without an electric potential present, exhibits photoconduction and is capable of converting photon energy into electric energy. In such a cell, as electron- donating material and preferably also as electron-accepting material, an organic compound, more preferably an organic polymer, is present. Electron- donating and electron-accepting material can be mixed or be present in separate layers. It is also possible that electron- donating functionalities and electron-accepting functionalities are present in one molecule, e.g. a polymer molecule.

An optoelectronic device according to the invention comprises electrically insulative material 5 that is at least partially positioned between the electrodes 2 and 4, and proximal to the electroactive material 3. In an embodiment, the electrically insulative material 5 is essentially non-permeable to one or more members selected from the group of oxygen, nitrogen, CO2, water, N2O, O3 and volatile organic compounds, e.g. ethanol, methanol, toluene etc.

In general, the electrically insulative material 5 in an optoelectronic device according to the invention is present in a shape wherein the size in one dimension (thickness) is considerably less than the size in at least one of the other dimensions (length, width), e.g. at least 10 times less. Accordingly, the electrically insulative material 5 usually has an elongated form or a flat form. For instance, the thickness 5a of the electrically insulative material 5 may be in the range of 10—10.000 nm, preferably in the range of 100—1000 nm.

The electrically insulative material's thickness 5a is generally equal to the distance between the electrodes, such that no channels are present through which a gas or liquid could flow. The dimension of length 5b of the electrically insulative material 5 is the dimension as defined by the direction of the protrusion of the electrodes (5b in Figure 2). In an optoelectronic device according to the invention, the length 5b of the electrically insulative material 5 is equal to or longer than the distance along which both electrodes 2 and 4 protrude relative to the electroactive material 3.

The length 5b of the electrically insulative material 5 is usually 10 nm or more. In particular, the length 5b is 100 nm or more, 300 nm or more, 1 μm or more, or 3 μm or more. In particular, the length 5b of the electrically insulative material 5 is 10 mm or less, 5 mm or less, or 2 mm or less. Preferably, the length 5b is in the range of 0.5 to 1 mm.

In a device according to the invention, the electrically insulative material 5 is an inorganic material that is selected from the group of metal oxides, silicon nitrides, silicon oxides, silicon carbides and combinations thereof. In particular it is selected from the group of Si₃N^ SiNH, SiCH, SiCh, Al₂O₃, SiON and SiONH.

An advantage of the present invention is that the electrically insulative material 5 may possess a higher permeability towards molecules or elements from the environment than barrier coatings used in the art to protect a device. Namely, the distance along which a physical entity from the environment on the outside of the device would need to penetrate through the electrically insulative material 5 in order to reach the electroactive material 3 is at least the length of the electrically insulative material 5. This penetration distance is substantially longer than the thickness of, for example, a barrier coating 6 surrounding the assembly of electrodes 2 and 4 and electroactive material 3 conventionally used to protect optoelectronic devices.

The electrically insulative material 5 usually has a permeability of 1 mg/m².day or less, preferably of 0.1 mg /m².day or less, more preferably of 1 μg/m².day or less. In an embodiment, a 300 nm thick layer of electrically insulative material 5 comprising silicon nitride was incorporated in a device, which layer had a permeability to water of 10"⁶ g water/m²/day.

The electrode 2 or 2b may be divided into at least two sub-layers, a sub-layer comprising a low work function material and a sub-layer comprising a conductor metal, wherein the sub-layer comprising the low work function material is positioned in between the sub-layer comprising the conductor metal and the electroactive layer 3. This is in particular advantageous in case the electrode 2 becomes the cathode and electrode 4 becomes the anode, which is the case for an inverted LED or a photovoltaic cell.

The electrode 4 may be divided into at least two sub-layers, a sub-layer comprising a low work function material and a sub-layer comprising a conductor metal, wherein the sub-layer comprising a low work function material is positioned in between the sub-layer comprising the conductor metal and the electroactive layer 3. This is in particular advantageous in case the device is a LED or a photovoltaic cell.

A low work function sub-layer, if desired, may have a thickness of at least 0.3 nm, preferably of 15 nm or less, in particular of 10 nm or less, more in particular of 5 nm or less. A conductor metal sub-layer (such as aluminium) may have a thickness in the range of 11-50,000 nm, in particular in the range of 50-1,000 nm.

If it is desired that the device is capable of emitting light and/or if it is desired that incident light from the outside environment can reach the electroactive layer 3, a relatively low thickness of the layer(s) that transmit the light may be advantageous. Depending on the material(s) used and the wavelength of the light, the person skilled in the art will be able to select a suitable thickness. The low work function sub-layer usually has a thickness of 15 nm or less, in particular of 8 nm or less. In case the low work function sub-layer comprises aluminium, a thickness in the range of 0.5—15 nm is suitable. The conductor metal sub-layer usually has a thickness in the range of 10—65 nm, in particular of 10—50 nm. In case the conductor metal sub-layer comprises silver, a thickness in the range of 10—50 nm is suitable.

In case of polymeric electroactive material, the low work function metal sub-layer of the electrode layer 4 preferably comprises barium. In case of non-polymeric electroactive material, the low work function sub-layer preferably comprises lithium fluoride.

In particular in case the organic electroactive material comprises an organic p- or n-type material, the low work function sub-layer may be omitted.

One or more other layers may be present, such as a non- conductive (organic) buffer layer 8, between an electrode, in particular cathode 4, and organic electroactive material 3.

Suitable conducting layers are, for instance, poly(ethylene dioxythiophene) /poly(styrenesulfonate) (PEDOT/PSS) or polyaniline (PANI). A (organic) conductor layer may have a thickness in the range of 50-400 nm, in particular in the range of 75—150 nm.

Further functional layers for the electronic device, such as one or more functional layers selected from the group of barrier layers, planarisation layers, etcetera, may be applied. The layers may be carried out in a manner known per se, e.g. as described in US 2002/0113548, WO 2005/001945, WO 2005/015173, WO 03/026011, WO03/022581 or WO 02/082561. In principle, the anode may be applied by electrodeposition. However, suitable substrate foils provided with a transparent conductive oxide and/or shunting lines which may serve as the anode are commercially available.

An optoelectronic device according to the invention may be flexible. With flexible is meant that it is possible to bend the device to a certain extent, e.g. to a cylinder of 200 mm diameter, whereby no damage occurs to the device, at least no damage that significantly reduces the performance of the device.

An optoelectronic device according to the invention may comprise a metallic (sealing) layer around the device, with the exception of the place where the electrically insulative material 5 is situated. An advantage of such metallic layer is the reduction of the anode and/or cathode resistance.

The present invention further relates to a method for fabricating an optoelectronic device comprising an organic electroactive material. A product according to the invention can be fabricated via a method according to the invention, using the materials as described hereinabove.

In a method according to the invention, components such as the anode 2, the cathode 4, the electroactive material 3, and the electrically insulative material 5, are (at least partially) applied on a substrate 1, wherein the organic electroactive material 3 is applied after the insulating barrier has been applied. This allows the electrically insulative material 5 to be made of materials of which the application conditions are not compatible with electroactive material, e.g. the conditions used for sputter deposition of silicon carbide, silicon nitride or silicon oxide. A method of the invention allows the realisation of a configuration wherein the electroactive material 3 is proximal to electrically insulative material 5, which latter material requires for its application on the support conditions that are not compatible with the electroactive material.

The assembly of the anode 2, the cathode 4, the electroactive material 3, the electrically insulative material 5 and other optional components may be provided with a barrier coating 6.

A method according to the invention may make use of electrochemical deposition. In particular, providing the assembly with a barrier coating may be performed electrochemically {i.e. via electrochemical deposition). Typically, with electrochemical deposition, a metallic layer is deposited on the assembly with the exception of the place of the device where the electrically insulative material 5 is situated. In this way, the application of a barrier coating 6 can be performed in a simple procedure without creating a metallic shortcut between the electrodes. This has the advantage that a method of fabrication of an optoelectronic device according to the invention is self-aligned and therefore simpler than conventional methods. With self-aligned is meant that the metal only grows on those electrically (semi-)conductive surfaces that are conductively connected to one of the electrodes of the electrodeposition apparatus. Also, no vacuum deposition is required to apply the barrier coating. Deposition may be carried out under atmospheric conditions.

Besides a barrier coating, other components of the device may also be applied using electrochemical deposition, e.g. an anode, a cathode, or parts thereof, such as a low work function layer. Electrochemical deposition (also called electrodeposition or electroplating) of metals and metalloids, including alloys thereof, involves the reduction of ions from an electrolyte solution. The technique is well-known for deposition of various metals and metalloids. In electrodeposition, the substrate is placed in a suitable electrolyte containing the ions of the metal or metalloid to be deposited. The substrate must have an electrically conductive layer which forms the cathode which is connected to the negative terminal of a power supply. The positive terminal is connected to a suitable anode. The thickness of the deposited layer is a function of the number of electrons (charge) used in the electro-deposition process. Electrodeposition from aqueous solutions is only possible for providing a layer of a metal or metalloid having a sufficiently high standard potential (also known as Nernst potential). The standard potential of the metal or metalloid should be higher than the standard potential of water to hydrogen, or the kinetic for the reduction of water to hydrogen at the surface of the metal or metalloid should be so slow that the metal can be plated even if its standard potential is below 0 Volt. For instance the noble metals and copper are examples of the first category, while zinc, chromium and cadmium are within the second category of metals that can be plated from an aqueous solution. However, an aqueous solution is in general not suitable or at least not practical for deposition of a metal or metalloid with a low standard potential, e.g., an alkaline earth metal (such as barium or calcium), lithium or aluminium. In particular, an aqueous solution is not suitable or at least not practical when water-sensitive materials such as organic electroactive materials are exposed to the aqueous solution.

The electrically insulative material 5 may be deposited by several techniques, e.g. by chemical vapour deposition, plasma enhanced chemical vapor deposition, physical vapour deposition and printing. In a method of the invention, it is possible to make use of a non-aqueous system for electrodeposition by applying a plating liquid that comprises an ionic liquid. An ionic liquid is a liquid formed of a salt that is liquid under the process conditions, such as a melt of a salt. In general an ionic liquid used in a method of the invention, has a melting point below 200 ⁰C, preferably of 100 ⁰C or less, in particular of 50 ⁰C or less. It is in particular preferred that the ionic liquid is liquid at about 20 ⁰C or at about 25 ⁰C. Such liquid may be referred to as a room temperature liquid salt.

Preferably one or more ions selected from the group of aluminium, silicon, tantalum, titanium, chromium, bismuth, zirconium, hafnium, tungsten, niobum and zinc, may be reduced and deposited in a method according to the invention, to form a barrier layer, optionally after at least partial oxidation.

The counter ions of the metal ions or metalloid ions used for deposition may be the same as or different from the cations of the ionic liquid. In particular the counter ions may be chosen from the group of chloride, bromide, iodide, nitrate, nitrite, fluoride, phosphate, imide, amide, borate, tosylate, tetrafluoroborate, hexafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, methylsulfate, bis(pentafluoroethyl)phosphinate, thiocynate, octylsulfate, hexylsulfate, butylsulfate, ethylsulfate, dicyanamide, hexafluoroantimonate, bis-(pentafluoroethyl)phospinate, bis-(trifluoromethyl)imide, trifluoroacetate, bis-trifluorsulfonimide, triflate and dicyanamide, including combinations thereof. Suitable examples of ionic liquids and deposition conditions are described in European Patent Application 07106347.3, of which the contents are incorporated herein by reference. In particular incorporated herein are the parts directed to suitable salts, as described from page 21, line 11 to page 23, line 3; pretreatment of the substrate and the control of voltage, current and temperature during the electrodeposition, as described from page 15, line 20 to page 20, line 27; other electroplating conditions such as additional solvents, metals, ions, and concentrations thereof as described in page 23, line 4 to page 26, line 9.

In a method for fabricating an optoelectronic device according to the invention, the deposition of electrically insulative material 5 may comprise

— electrodepositing a metallic or metalloid material on the first electrode 2 in an ionic liquid; — oxidizing the metallic or metalloid material.

Further, in a method for fabricating an optoelectronic device according to the invention, it is possible that a first and a second electrically insulative material are applied, the first electrically insulative material having a lower permeability than the second electrically insulative material. The above described electrochemical deposition for the fabrication of devices according to the invention is especially advantageous in case of in-plane connecting devices (Figure 6 and the example). Besides providing a simple and effective method to avoid unwanted metallic shortcuts between the plurality of electrodes that are present, the different contacts between the devices can be strengthened via the electrochemical deposition.

Accordingly, the invention further relates to a method for fabricating a structure comprising in-plane connecting devices, comprising

- fabricating a first optoelectronic device using a method according to the invention for fabricating an optoelectronic device comprising electroactive material 3, - fabricating at least a second optoelectronic device using a method according to the invention for fabricating an optoelectronic device comprising electroactive material 3, wherein at least one electrical connection exists between at least the first and at least the second optoelectronic device.

The two or more optoelectronic devices that are fabricated according to the above method for fabricating a structure comprising in-plane connecting devices, preferably comprise organic electroactive material.

Preferably, in a method for fabricating a structure comprising in-plane connecting devices according to the invention, at least one component of a first device is provided or deposited in the same step of the method according to the invention for fabricating an optoelectronic device comprising electroactive material, as the corresponding component of an at least second device. In an embodiment, a barrier coating 6 is present at the outside of the device which coating has a low permeability to a gaseous, vaporous or liquid component, such as water. For instance, the permeability to water may be less than Iμg/m².dag. The permeability may be determined as described in US2006/147346. The invention will now be illustrated by the following example.

EXAMPLE

On a glass-substrate a 100 nm thick layer of indium tin oxide (ITO) is applied. Thereafter a 500 nm thick stack of molybdenum-aluminium- molybdenum shunting metal layers is applied. Then, in the region of the anode-lead-out is prepared a 300 nm thick electrically insulative layer of SiN. On the shunt a 2 μm thick organic isolation layer is prepared. Then, a 100 nm thick pedot/PSS layer is printed on the transparent electrode, followed by a 80 nm thick LEP layer. Thereafter, a 5 nm thick barium/100 nm thick aluminum cathode is applied via vapour deposition. Finally, a 10 μm aluminium layer is deposited using electrodeposition in a plating liquid comprising an ionic liquid. Analogously, a plurality of in-plane connecting devices are prepared and subjected to electrodeposition.

Claims

1. An optoelectronic device comprising at least a first electrode (2), at least a second electrode (4) and organic electroactive material (3), wherein • at least part of the organic electroactive material (3) is located between the first electrode (2) and the second electrode (4);

• in at least a part of the optoelectronic device said first electrode (2) and said second electrode (4) protrude relative to at least part of the organic electroactive material (4), and wherein • electrically insulative material (5) is present in a space defined by the protruding parts of the first electrode (2) and the second electrode (4).

2. An optoelectronic device wherein the first electrode (2) is an anode and the second electrode (4) is a cathode.

3. An optoelectronic device according to claim 1, wherein the electroactive material (3) comprises an organic light- emitting compound or an organic photovoltaic compound.

4. An optoelectronic device according to any of the preceding claims, wherein electroactive material (3) is fully sealed by the combination of a sealing layer or stack on the device and the electrically insulative material (5) present in a space defined by the protruding parts of the first electrode (2) and the second electrode (4).

5. An optoelectronic device according to any of the preceding claims, wherein the electrically insulative material (5) is non-permeable to one or more members selected from the group of air, water and volatile organic compounds.

6. An optoelectronic device according to any of the preceding claims, wherein the thickness of the electrically insulative material (5) is in the range of 10-10.000 nm, preferably in the range of 100-1000 nm

7. An optoelectronic device according to any of the preceding claims, wherein, in the part of the optoelectronic device wherein the first electrode and the second electrode protrude relative to the electroactive material, both electrodes (2) and (4) protrude at least 100 nm relative to the electroactive material (3), and preferably protrude between 0.5 and 1 mm.

8. An optoelectronic device according to any of the preceding claims, wherein the electrically insulative material (5) is an inorganic material that is selected from the group of metal oxides, silicon nitrides, silicon oxides, silicon carbides and combinations thereof.

9. An optoelectronic device according to any of the preceding claims, which is flexible.

10. A structure comprising two or more optoelectronic devices according to any of the preceding claims, wherein one or more electrical connections exist between at least two of the optoelectronic devices.

11. Method for fabricating an optoelectronic device comprising organic electroactive material (3), comprising • providing a first electrode (2);

• depositing electrically insulative material (5) on a first electrode (2) thereby partly covering the first electrode (2) with electrically insulative material (5); thereafter • depositing organic electroactive material (3) on a part of the first electrode (2) that has not been covered by the electrically insulative material (5); thereafter

• depositing a second electrode (4) on at least part of the electroactive material (3) and on at least part of the electrically insulative material

(5).

12. Method according to claim 11, wherein the deposition of electrically insulative material (5) comprises • electrodepositing a metallic or metalloid material on the first electrode

(2) in an ionic liquid;

• oxidizing the metallic or metalloid material.

13. Method according to claim 11 or 12, wherein a first and a second electrically insulative material (5) are applied, the first electrically insulative material having a lower permeability than the second electrically insulative material.

14. Method for fabricating a structure according to claim 10, comprising • fabricating a first optoelectronic device using a method according to any one of the claims 11-13,

• fabricating at least a second optoelectronic device using a method according to any one of the claims 11-13, wherein at least one electrical connection exists between at least the first and at least the second optoelectronic device.

15. Method according to claim 14, wherein at least one component of a first device is provided or deposited in the same step of claim 11 as the corresponding component of an at least second device.