GB2542346A

GB2542346A - Anthrathiophene derivatives with transverse solubilising units and their applications as organic semiconductors

Info

Publication number: GB2542346A
Application number: GB1516229.0A
Authority: GB
Inventors: Islam Nazrul; James Newsome Christopher; Zuberi Tania; Zuberi Sheena
Original assignee: Cambridge Display Technology Ltd
Current assignee: Cambridge Display Technology Ltd
Priority date: 2015-09-14
Filing date: 2015-09-14
Publication date: 2017-03-22
Also published as: WO2017046554A1; GB201516229D0

Abstract

Anthrathiophene derivatives as represented in formula (I) wherein R1-R10 are as defined in claim 1, comprise transverse solubilising groups at transversal positions relative to the longitudinal axis of the anthracene core. These compounds enable preferential molecular stacking and a high field effect mobility and at the same time show improved solubility as compared to known benzothiophene based materials. In addition, organic thin films comprising these derivatives, their use in electronic devices and components, such as organic thin film transistors, and methods of manufacturing the same are disclosed.

Description

ANTHRATHIOPHENE DERIVATIVES WITH TRANSVERSE SOLUBILISING UNITS AND THEIR APPLICATIONS AS ORGANIC SEMICONDUCTORS

FIELD OF INVENTION

[0001] This invention relates to novel anthrathiophene derivatives, organic thin films comprising these derivatives, their use in electronic devices and components, and to methods of manufacturing the same.

BACKGROUND OF THE INVENTION

[0002] In the recent years, there has been increased interest in the development of small-molecule organic electronic materials as alternatives to inorganic semiconductors, such as silicon-based semiconductors, as they are lightweight, provide a high flexibility and allow manufacturing and processing of electronic devices at relatively low costs. Typically applied within thin films, such organic semiconductors find use in a large number of electronic devices, such as displays (including organic light-emitting diodes (OLED)), photovoltaics, and electronic circuits and components (e.g. organic field effect transistor (OFET) devices).

[0003] Ideally, organic semiconductors exhibit high charge carrier mobility or high field effect mobility, respectively, and favourable ττ-π stacking. Organic semiconductors fulfilling these criteria tend to be those which comprise compounds having a rigid planar structure and extensively conjugated π-systems allowing for the movement of electrons. In addition, it is of utmost importance that organic semiconductors are both highly soluble and thermally stable during solution processing.

[0004] Pentacene derivatives, such as e.g. 6,13-bis[(triisopropylsilyl)ethynyl] pentacene (commonly referred to as “TIPS-pentacene”), have been shown to represent promising candidates in terms of solubility and stability in organic solvents as well as the performance in organic field effect transistors (see e.g. US 6,690,029 B1).

[0005] Benzothiophene derivatives have also been studied as organic semiconductor material.

[0006] For instance, WO 2012/076092 A1 discloses non-linear acene compounds containing solubilising ethynyl substituents at the central ring.

[0007] JP 2013-170127 A discloses Diels Alder adducts of benzothiophene derivatives as organic semiconductor materials.

[0008] However, since the hitherto disclosed compounds still leave room for improvements, it is desirable to provide compounds that exhibit high field effect mobility, favourable π-π stacking, and at the same time show improved solubility and thermal stability during solution processing when compared to existing benzothiophene based materials.

SUMMARY OF THE INVENTION

[0009] The present invention solves this object with the subject matter of the claims as defined herein. The advantages of the present invention will be further explained in detail in the section below and further advantages will become apparent to the skilled artisan upon consideration of the invention disclosure.

[0010] In the search for soluble, small molecule organic semiconductor materials for thin film transistor device applications, materials that exhibit a crystalline structure enabling a high field effect mobility and an improved solubility as compared to known benzothiophene based materials have been studied. The present inventors surprisingly found that implementation of specific transverse solubilising groups at the central position of a thienoacene core enables preferential molecular stacking in the solid crystal and provides a solution to the abovementioned problems.

[0011] Generally speaking, in one aspect the present invention relates to an anthrathiophene derivative represented by the following General Formula (I):

(I) wherein, of the residues R1 to R10, either two or four groups transversal to the longitudinal axis of the anthracene core (axis along which the aromatic rings of the anthracene moiety are fused) are each independently selected from a solubilising group consisting of: alkyl groups having 4 to 18 carbon atoms, halogens, halogenoalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted alkoxy groups having 6 to 18 carbon atoms, substituted or unsubstituted thioalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted aminoalkyl groups having 6 to 18 carbon atoms or substituted or unsubstituted trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups, the optional substituent being a halogen; wherein two of the pairs R3 and R4, R4 and R5, R5 and R6, R7 and R8, R8 and R9, or R9 and R10 are cross-bridged with each other to form a substituted or unsubstituted thieno group, the optional substituent being selected from any of a halogen or an alkyl group comprising 1 to 4 carbon atoms; and wherein the residues R1 to R10 neither being a solubilising group nor forming a thieno group are independently selected from hydrogen or an alkyl group having 1 to 3 carbon atoms.

[0012] In a preferred aspect, the present invention relates to an anthrathiophene derivative represented by General Formula (II): 5

(II) wherein R1 and R2 represent a solubilising group selected from the group consisting of: alkyl groups having 4 to 18 carbon atoms, halogens, halogenoalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted alkoxy groups having 6 to 18 carbon atoms, substituted or unsubstituted thioalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted aminoalkyl groups having 6 to 18 carbon atoms or substituted or unsubstituted trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups, the optional substituent being a halogen; wherein R5, R6, R7 and R8 are independently selected from hydrogen or an alkyl group having 1 to 4 carbon atoms; and wherein A1 and A2 independently represent a thieno group selected from one of the following formulae (VI) and (VII):

(VI) (VII)

Ra and Rb being independently selected from any of hydrogen, a halogen or an alkyl group comprising 1 to 4 carbon atoms.

[0013] In another preferred aspect, the present invention relates to an anthrathiophene derivative represented by General Formula (III):

(HI) wherein either only one of the pairs R1 and R2, R3 and R7, R4 and R8, or all of R3, R4, R7 and R8 represent solubilising groups selected from the group consisting of: alkyl groups having 4 to 18 carbon atoms, halogens, halogenoalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted alkoxy groups having 6 to 18 carbon atoms, substituted or unsubstituted thioalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted aminoalkyl groups having 6 to 18 carbon atoms or substituted or unsubstituted trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups, the optional substituent being a halogen; wherein the residues R1 to R8 which do not represent a solubilising group are independently selected from hydrogen or an alkyl group having 1 to 3 carbon atoms; and wherein A1 and A2 independently represent a thieno group selected from one of the above formulae (VI) and (VII).

[0014] In another preferred aspect, the present invention relates to an anthrathiophene derivative represented by General Formula (IV):

(IV) wherein either only one of the pairs R1 and R2, R3 and R7, or all of R1, R3, R2 and R7 represent solubilising groups selected from the group consisting of: alkyl groups having 4 to 18 carbon atoms, halogens, halogenoalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted alkoxy groups having 6 to 18 carbon atoms, substituted or unsubstituted thioalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted aminoalkyl groups having 6 to 18 carbon atoms or substituted or unsubstituted trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups, the optional substituent being a halogen; wherein the residues R1 to R8 which do not represent a solubilising group are independently selected from hydrogen or an alkyl group having 1 to 3 carbon atoms; and wherein A1 and A2 independently represent a thieno group selected from one of the above formulae (VI) and (VII).

[0015] In another preferred aspect, the present invention relates to an anthrathiophene derivative represented by General Formula (V):

(V) wherein either only one of the pairs R1 and R2, R3 and R7, or all of R1, R3, R2 and R7 represent solubilising groups selected from the group consisting of: alkyl groups having 4 to 18 carbon atoms, halogens, halogenoalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted alkoxy groups having 6 to 18 carbon atoms, substituted or unsubstituted thioalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted aminoalkyl groups having 6 to 18 carbon atoms or substituted or unsubstituted trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups, the optional substituent being a halogen; wherein the residues R1 to R10 which do not represent a solubilising group are independently selected from hydrogen or an alkyl group having 1 to 3 carbon atoms; and wherein A1 and A2 independently represent a thieno group selected from one of the above formulae (VI) and (VII).

[0016] In a further aspect, the present invention provides an organic thin film comprising the above-described anthrathiophene derivatives.

[0017] Another aspect of the present invention is an electronic device or component comprising said an organic thin film.

[0018] Moreover, the present invention relates to a solution for applying to the surface of a substrate to form a semiconducting portion on the substrate, the solution comprising the above-defined anthrathiophene derivative.

[0019] Also, the invention relates to methods for the preparation of organic thin films comprising the aforementioned compounds and the use of said compounds and organic thin films as semiconducting material in electronic devices.

[0020] Other aspects of the present invention are described in the following description and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 schematically illustrates the general architecture of a conventional bottom-gate organic thin film transistor.

[0022] FIG. 2 schematically illustrates a pixel comprising an organic thin film transistor and an adjacent organic light-emitting device fabricated on a common substrate.

[0023] FIG. 3 schematically illustrates a stacked configuration comprising an organic thin film transistor and an organic light-emitting device.

[0024] FIG. 4 shows a comparison of the reorganization energies (B3LYP/6-31G*) of C8BTBT and benzothiophene derivatives of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0025] For a more complete understanding of the present invention, reference is now made to the following description of the illustrative embodiments thereof:

Anthrathiophene Derivatives [0026] In a first embodiment, the present invention relates to anthrathiophene derivatives, the most general structure of which may be represented by the following General Formula (I):

(I) [0027] In the above General Formula (I), of the residues R1 to R10, either two or four groups transversal to the longitudinal axis of the anthracene core are each independently selected from a solubilising group consisting of: alkyl groups having 4 to 18, preferably 6 to 16, more preferably 8 to 12 carbon atoms; halogens, preferably fluorine; halogenoalkyl groups having 6 to 18, preferably 6 to 16, more preferably 8 to 12 carbon atoms; substituted or unsubstituted alkoxy, thioalkyl, aminoalkyl having 6 to 18, preferably 6 to 16, more preferably 8 to 12 carbon atoms or substituted or unsubstituted trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups. If the alkoxy, thioalkyl, aminoalkyl or trialkylsilyl groups are substituted, the substituent is a halogen, preferably fluorine. From the viewpoint of increased solubility, it is preferable that the solubilising groups are independently selected from the group consisting of: alkyl groups having 4 to 18 carbon atoms, alkoxy groups having 6 to 18 carbon atoms, thioalkyl groups having 6 to 18 carbon atoms, halogenoalkyl groups having 6 to 18 carbon atoms, aminoalkyl groups having 6 to 18 carbon atoms or trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups. The halogenoalkyl group is preferably a fluoroalkyl group. The alkyl substituents in the trialkylsilyl groups may be identical or different. Further preferred in terms of solubility is a solubilising group selected from an alkyl group having 4 to 18 carbon atoms, an alkoxy group having 6 to 18 carbon atoms or a trialkylsilyl group comprising 4 to 16 carbon atoms in the alkyl groups. The longitudinal axis of the anthracene core denotes the axis A along which the aromatic rings of the anthracene moiety are fused. Preferably, the two or four groups transversal to the longitudinal axis of the anthracene core are R1 and R2, R3and R7, Rs and R10 (in case of two groups), and R1/R3 and R2/R7, R1/R10 and R2/R6, R3/R4 and R7/R8, or R5/R6 and R9/R10 (in case of four groups). More preferably, the two groups transversal to the longitudinal axis of the anthracene core bearing the solubilising group are R1 and R2.

[0028] In a preferred embodiment, the solubilising groups are identical. Preferably, the substituents used as the solubilising groups exclusively comprise linear alkyl chains.

[0029] Furthermore, in the above General Formula (I), of the residues R1 to R10 not being solubilising groups, two of the pairs R3 and R4, R4 and R5, R5 and R6, R7 and R8, R8 and R9, and R9 and R10 are cross-bridged with each other to form a thieno group which may be substituted or unsubstituted. In a preferred embodiment, two of the pairs R3 and R4, R4 and R5, R5 and R6, R7 and R8, R8 and R9, and R9 and R10 are cross-bridged with each other to form a thieno group. If the thieno group is substituted, the substituent is selected from any of a halogen or an alkyl group comprising 1 to 4 carbon atoms.

[0030] In the above General Formula (I), the residues R1 to R10 neither being a solubilising groups nor forming a thieno group according to the above definitions are independently selected from hydrogen or an alkyl group having 1 to 3 carbon atoms from the viewpoint of achieving advantageously shallow HOMOs.

[0031] Modification of organic semiconductors with different alkyl substituents in order to tune their solubility is well-known from prior art. However, substitution with relatively long alkyl chains may often lead to a decrease in solubility due to strong Van der Waals interactions between the molecules. While using branched alkyl chains may improve solubility, it is often accompanied with a poor carrier or field effect mobility. Therefore, designing compounds that exhibit high field effect mobility, favourable ττ-π stacking, and at the same time show improved solubility and thermal stability during solution processing is highly challenging. The above-described compounds according to General Formula (I) fulfill these criteria and in particular exhibit a surprisingly high solubility despite of having a relatively large number of carbon atoms in the solubilising groups.

[0032] In preferred embodiments, the present invention relates to compounds selected from any of the General Formulae (II) to (V):

(II)

(IN)

(IV)

(V) [0033] In the above General Formulae (II), (III), (IV) and (V), of the residues R1 to R10, either two or four groups transversal to the longitudinal axis of the anthracene core may be each independently selected from a solubilising group consisting of: alkyl groups having 4 to 18, preferably 6 to 16, more preferably 8 to 12 carbon atoms; halogens, preferably fluorine; halogenoalkyl groups having 6 to 18, preferably 6 to 16, more preferably 8 to 12 carbon atoms; substituted or unsubstituted alkoxy, thioalkyl, aminoalkyl groups having 6 to 18, preferably 6 to 16, more preferably 8 to 12 carbon atoms or substituted or unsubstituted trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups. If the alkoxy, thioalkyl, aminoalkyl or trialkylsilyl groups are substituted, the substituent is a halogen, preferably fluorine. The alkyl substituents in the trialkylsilyl groups may be identical or different. In a preferred embodiment, the solubilising groups in General Formulae (II), (III), (IV) and (V) are identical. Preferably, the groups used as the solubilising groups exclusively comprise linear alkyl chains.

[0034] From the viewpoint of increased solubility, it is preferable that of the residues R1 to R10, either two or four groups transversal to the longitudinal axis of the anthracene core in the above General Formulae (II), (III), (IV) and (V) are each independently selected from the group consisting of: alkyl groups having 8 to 12 carbon atoms, alkoxy groups having 8 to 12 carbon atoms, and trialkylsilyl groups comprising 6 to 10 carbon atoms in the alkyl groups.

[0035] For the compounds according to General Formula (II), it is preferable that R1 and R2 represent solubilising groups according to the above definition.

[0036] For the compounds according to General Formula (III), it is preferable that either R1 and R2, R3 and R7, or R4 and R8 represent solubilising groups according to the above definition. In another preferred embodiment, R3, R4, R7 and R8 in General Formula (III) are solubilising groups according to the above definition.

[0037] For the compounds according to General Formula (IV), it is preferable that either R1 and R2 or R3 and R7 represent solubilising groups according to the above definition. In another preferred embodiment, R1, R3, R2 and R7 in General Formula (IV) are solubilising groups according to the above definition.

[0038] For the compounds according to General Formula (V), it is preferable that either R1 and R2 or R3 and R7 represent solubilising groups according to the above definition. In another preferred embodiment, R1, R3, R2 and R7 in General Formula (V) are solubilising groups according to the above definition.

[0039] Furthermore, in the above General Formulae (II), (III), (IV) and (V), A1 and A2 independently represent a thieno group selected from one of the following formulae (VI) and (VII):

(VI) (VII) wherein Ra and Rb are independently represented by hydrogen, a halogen or an alkyl group comprising 1 to 4 carbon atoms. Preferably, Ra and Rb are independently represented by hydrogen, a halogen or an alkyl group comprising 1 to 4 carbon atoms at least one of Ra or Rb is hydrogen. More preferably, both Ra and Rb are hydrogen.

[0040] In the above General Formulae (II), (III), (IV) and (V), the residues R1 to R10 not being a solubilising group are independently selected from hydrogen or an alkyl group having 1 to 3 carbon atoms. Preferably, these residues are hydrogen.

[0041] Of the above General Formulae (II), (III), (IV) and (V), compounds according to General Formulae (II), (III) and (IV) are preferable, and compounds according to General Formulae (II) and (III) are more preferable.

[0042] The above compounds according to General Formulae (II), (III), (IV) and (V) have been shown to exhibit a particularly favourable balance in terms of high field effect mobility, favourable ττ-π stacking, and thermal stability during solution processing. Last but not least, these compounds are easily soluble and may thus be applied by a large variety of solution deposition techniques.

[0043] A number of exemplary compounds illustrating the present invention are listed hereinbelow:

(1) (2) (3)

(4) (5) (6)

(7) (8) (9)

(10) (11) (12)

(13) (14) (15)

(16) (17) (18)

(19) (20) (21)

(22) (23) (24)

(25) (26) (27)

(28) (29) (30)

(31) (32) (34)

(35) (36) (37)

(38) (39) (40)

(41) (42) (43)

(44) (45) (46)

(47) (48) (49)

(50) (51) (52)

(53) (54) (55)

(56) (57)

(58) (59)

(60) (61) [0044] The compounds of the present invention may be synthesized according to or in analogy to methods known to the skilled artisan.

[0045] An exemplary method for the synthesis of compound (1) is shown in the following scheme:

[0046] Intermediate 1b can be prepared by treatment of 1,8-dihydroxyanthraquinone 1a with Ν,Ν-dimethylthiocarbamoyl chloride following by recrystallization of the crude product from hot DMSO. Subsequent rearrangement upon heating at 200°C can give intermediate 1c. Mercaptan 1d may be obtained by hydrolysis of 1c in refluxing MeOH and the compound can be used in the next step without further purification.

[0047] The diketone 1f may be prepared by treatment of thiophenol 1d with bromoacetaldehyde diethylacetal in the presence of sodium hydride followed by cyclisation with phosphorous pentoxide. Crude 1f can be purified by recrystalization from hot chloroform.

[0048] Dihydroxy intermediate 1g may be prepared under standard Grignard conditions and the crude product purified by column chromatography (neutral alumina, EtOAc:Heptane) followed by recrystallization. Treatment of 1g with tin chloride and purification by column chromatography (DCM:Heptane) may give Compound 1 of the invention.

Organic semiconductor thin films and their applications [0049] In a further embodiment, the present invention relates to organic thin films comprising the above-described anthrathiophene compounds.

[0050] For the preparation of such organic thin films, the compounds according to the present invention may be used on their own or in combination with a polymer to form an organic material blend.

[0051] The organic thin films may be fabricated by depositing the anthrathiophene derivatives according to the first embodiment of the present invention on a substrate according to conventional methods known in the art, or alternatively dissolving said compounds in an organic solvent (optionally together with the polymer) and then coating the same at room temperature according to a solution process. After the deposition or coating process, a heating treatment may be performed to further enhance the densification and uniformity of the thin film. The method of film deposition may include thermal deposition, vacuum deposition, laser deposition, screen printing, printing, imprinting, spin casting, dipping, inkjetting, roll coating, flow coating, drop casting, spray coating, and/or roll printing, for example. Preferred solution deposition techniques include spin coating and ink jet printing.

[0052] The organic solvent is not particularly limited and may include an aliphatic hydrocarbon (e.g. hexane or heptane), a haloalkane (e.g. chloroform), an aromatic hydrocarbon (e.g. toluene, pyridine, tetralin, quinoline, anisole, mesitylene, or xylene), a ketone (e.g. methyl isobutyl ketone, 1-methyl-2-pyrrolidinone, cyclohexanone, or acetone), an ether (e.g. tetrahydrofuran or isopropyl ether), an acetate (e.g. ethyl acetate, butyl acetate, or propylene glycol methyl ether acetate), an alcohol (e.g. isopropyl alcohol or butanol), an amide (e.g. dimethyl acetamide or dimethyl formamide), a silicone, and a mixture thereof. The type and amount of the solvent relative to the anthrathiophene derivative may be appropriately selected and determined by a person of ordinary skill in the art.

[0053] The thickness of the organic thin films is not particularly limited and may be adjusted appropriately by the skilled artisan depending on their application. Usually, thicknesses of 1 pm or less are used, and for use in OFETs or OLEDs, the layer thickness is preferably 500 nm or less.

[0054] If the compounds according to the present invention are used in combination with a polymer to form an organic material blend, the polymer may be a polymeric binder in accordance with those disclosed in WO 2012/076092 A1, for example.

[0055] The organic thin films according to the present invention may be used as charge transport, semiconducting, electrically conducting, photoconducting or light emitting material in electronic devices and components.

[0056] Examples of electronic devices including the organic thin film as a carrier transport layer may include a transistor, an organic light emitting diode (OLED), a photovoltaic device, a solar cell, a laser device, a memory, and/or a sensor, and the organic thin film may be applied to each device according to a conventional process commonly known in the art.

[0057] In a preferred embodiment, the organic thin films according to the present invention may are used as semiconducting layers in electronic components, such as organic thin film transistors (OTFT).

[0058] An exemplary configuration of an OTFT is shown in Fig. 1, illustrating the general architecture of a bottom-gate OTFT. Herein, a gate electrode 12 is deposited on a substrate 10. An insulating layer 11 of dielectric material is deposited over the gate electrode 12 and source and drain electrodes 13, 14 are deposited over the insulating layer 11 of dielectric material. The source and drain electrodes 13, 14 are spaced apart to define a channel region therebetween located over the gate electrode 12. The organic semiconductor material 15 is deposited in the channel region for connecting the source and drain electrodes 13, 14. The organic semiconductor material 15 may extend at least partially over the source and drain electrodes 13, 14.

[0059] As an alternative to the bottom-gate OTFT, the gate electrode may be provided at the top of an organic thin film transistor to form a so-called top-gate OTFT. In such an architecture, source and drain electrodes are deposited on a substrate and spaced apart to define a channel region there between. A layer of an organic semiconductor material is deposited in the channel region to connect the source and drain electrodes and may extend at least partially over the source and drain electrodes. An insulating layer of dielectric material is deposited over the organic semiconductor material and may also extend at least partially over the source and drain electrodes. A gate electrode is deposited over the insulating layer and located over the channel region.

[0060] In general, organic thin film transistors may be fabricated on rigid or flexible substrates. Rigid substrates may be selected from glass or silicon and flexible substrates may comprise thin glass or plastics such as poly(ethylene-terephthalate) (PET), poly(ethylene-naphthalate) (PEN), polycarbonate and polyimide, for example.

[0061] The gate electrode can be selected from a wide range of conducting materials for example a metal (e.g. gold) or metal compound (e.g. indium tin oxide). Alternatively, conductive polymers may be deposited as the gate electrode. Such conductive polymers may be deposited from solution using, for example, spin coating or ink jet printing techniques and other solution deposition techniques discussed above.

[0062] The insulating layer comprises a dielectric material selected from insulating materials having a high resistivity. The dielectric constant, k, of the dielectric material is typically around 2-3 although materials with a high value of k are desirable because the capacitance that is achievable for an OTFT is directly proportional to k, and the drain current ID is directly proportional to the capacitance. Thus, in order to achieve high drain currents with low operational voltages, OTFTs with thin dielectric layers in the channel region are preferred. The dielectric material may be organic or inorganic. Preferred inorganic materials include S1O2, SiNx and spin-on-glass (SOG). Preferred organic materials are generally polymers and include insulating polymers such as poly vinylalcohol (PVA), polyvinylpyrrolidine (PVP), acrylates such as polymethylmethacrylate (PMMA) and benzocyclobutanes (BCBs), for example. The insulating layer may be formed from a blend of materials or comprise a multi-layered structure.

[0063] FIG. 2 shows a pixel comprising an organic thin film transistor 100 and an adjacent organic light-emitting device (OLED) 102 fabricated on a common substrate 104. The OTFT 100 comprises gate electrode 106, dielectric layer 108, source and drain electrodes 110 and 112 respectively, and OSC layer 114. The OLED 102 comprises anode 116, cathode 118 and an electroluminescent layer 120 provided between the anode 116 and cathode 118. Further layers may be located between the anode 116 and cathode 118, such as charge transporting, charge injecting or charge blocking layers. In the embodiment of FIG. 2, the layer of cathode material 118 extends across both the OTFT 100 and the OLED 102, and an insulating layer 122 is provided to electrically isolate the cathode layer 118 from the OSC layer 114. The active areas of the OTFT 100 and the OLED 102 are defined by a common bank material formed by depositing a layer of photoresist 124 on substrate 104 and patterning it to define OTFT 100 and OLED 102 areas on the substrate.

[0064] In FIG. 2, the drain electrode 112 is directly connected to the anode 116 of the organic light-emitting device 102 for switching the organic light-emitting device 102 between emitting and non-emitting states.

[0065] In an alternative arrangement illustrated in FIG. 3, an organic thin film transistor 200 may be fabricated in a stacked relationship to an organic light-emitting device 202. In such an embodiment, the organic thin film transistor 202 is built up as described above in either a top or bottom gate configuration. As with the embodiment of FIG. 2, the active areas of the OTFT 200 and OLED 202 are defined by a patterned layer of photoresist 124, however in this stacked arrangement, there are two separate bank layers 124—one for the OLED 202 and one for the OTFT 200. A planarisation layer 204 (also known as a passivation layer) is deposited over the OTFT 200. Exemplary passivation layers 204 include BCBs and parylenes. The organic light-emitting device 202 is fabricated over the passivation layer 204 and the anode 116 of the organic light-emitting device 202 is electrically connected to the drain electrode 112 of the OTFT 200 by a conductive via 206 passing through passivation layer 204 and bank layer 124.

[0066] It will be appreciated that pixel circuits comprising an OTFT and an optically active area (e.g. light emitting or light sensing area) may comprise further elements. In particular, the OLED pixel circuits of FIGS. 2 and 3 will typically comprise least one further transistor in addition to the driving transistor shown, and at least one capacitor. It will be appreciated that the organic light-emitting devices described herein may be top or bottom-emitting devices. That is, the devices may emit light through either the anode or cathode side of the device. In a transparent device, both the anode and cathode are transparent. It will be appreciated that a transparent cathode device need not have a transparent anode (unless, of course, a fully transparent device is desired), and so the transparent anode used for bottom-emitting devices may be replaced or supplemented with a layer of reflective material such as a layer of aluminium.

[0067] Transparent cathodes are particularly advantageous for active matrix devices because emission through a transparent anode in such devices may be at least partially blocked by OTFT drive circuitry located underneath the emissive pixels as can be seen from the embodiment illustrated in FIG. 3.

[0068] Other layers may be included in the device architecture. For example, in addition to providing a self assembled monolayer (SAM) on the gate, source or drain electrodes one may be provided on the, substrate, insulating layer and organic semiconductor material to promote crystallinity, reduce contact resistance, repair surface characteristics and promote adhesion where required. In particular, the dielectric surface in the channel region may be provided with a monolayer comprising a binding region and an organic region to improve device performance, e.g. by improving the organic semiconductor's morphology (in particular polymer alignment and crystallinity) and covering charge traps, in particular for a high k dielectric surface. Exemplary materials for such a monolayer include chloro- or alkoxy-silanes with long alkyl chains, e.g. octadecyltrichlorosilane.

Examples

Reorganisation Energies of Thienoacenes [0069] Quantum chemical calculations were performed with the hybrid density functional theory (DFT) method using B3LYP and the 6-31G* (5d) basis set according to methods known in the art in order to determine the reorganization energies of anthrathiophene derivatives according to the present invention. Reorganization energy (λ) is an important molecular factor that may affect charge transport properties of OSC materials. Carrier transport in organic solids is often described by the hopping model, where the high mobility, i.e. rapid exchange of carriers between molecules can be realized by a small energy, λ (energy consumption during carrier exchange at the molecular level). For p-type OSC materials largely π-extended compounds tend to have smaller Ah (λ for hole) values in general, because of the effective delocalization of hole in the radical cation state, which reduces structural deformation during carrier transport. The smaller the lvalue, materials show better transport properties.

[0070] In particular, the reorganization energies of compounds (1), (4), (7), (44) and (53) have been calculated in accordance with procedures described in the literature (see e.g. J. Phys. Chem. A, 2003, 107, 5241-5251) and compared to 2,7-Dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8BTBT), a commercially available p-type organic semiconductor, and to 6,13-bis[(triisopropylsilyl)ethynyl] pentacene (TIPS-pentacene), the formulae of which are shown in the following:

C8BTBT

TIPS-pentacene [0071] The results of the calculations are shown in FIG. 4. All values are guoted in electronvolts (eV).

[0072] As is demonstrated by FIG.4, the anthrathiophene according to the present invention derivatives exhibit shallower HOMO levels when compared with C8BTBT and TIPS-pentacene and smaller reorganization energies compared to C8BTBT. Hence, it is expected that the anthrathiocene derivatives of the present invention are suitable candidates for organic semiconductor applications.

Solubility, Thermal Stability and Mobility Properties

(A)

(B)

(C) [0073] From the foregoing description, the anthrathiophene derivatives of the present invention are expected to advantageously exhibit improved solubility, thermal stability and high field-effect mobility as compared with compounds (A), (B) and (C) which are known to have poor solubility and thermal stability and low field effect mobility. Further, a comparison between the performances of compounds (A) and (B) shows that an extension of alkyl chain length only provides small improvements in solubility due to increased Van der Waals interactions. However, even this improvement is at the expense of the field-effect mobility, which dramatically decreases upon using longer alkyl chains as solubilising groups. Moreover, it is expected that the examples of the present invention will perform better than example (C) bearing the solubilising groups at the thieno group.

[0074] Once given the above disclosure, many other features, modifications, and improvements will become apparent to the skilled artisan.

Claims

1. Anthrathiophene derivative represented by the following General Formula (I):

(I) wherein, of the residues R1 to R10, either two or four groups transversal to the longitudinal axis of the anthracene core are each independently selected from a solubilising group consisting of: alkyl groups having 4 to 18 carbon atoms, halogens, halogenoalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted alkoxy groups having 6 to 18 carbon atoms, substituted or unsubstituted thioalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted aminoalkyl groups having 6 to 18 carbon atoms or substituted or unsubstituted trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups, the optional substituent being a halogen; wherein two of the pairs R3 and R4, R4 and R5, R5 and R6, R7 and R8, R8 and R9, or R9 and R10 are cross-bridged with each other to form a substituted or unsubstituted thieno group, the optional substituent being selected from any of a halogen or an alkyl group comprising 1 to 4 carbon atoms; and wherein the residues R1 to R10 neither being a solubilising group nor forming a thieno group are independently selected from hydrogen or an alkyl group having 1 to 4 carbon atoms.

2. Anthrathiophene derivative according to claim 1, represented by General Formula (II):

(VI) (VII) Ra and Rb being independently selected from any of hydrogen, a halogen or an alkyl group comprising 1 to 4 carbon atoms.

3. Anthrathiophene derivative according to claim 1, represented by General Formula (III):

(III) wherein either only one of the pairs R1 and R2, R3 and R7, R4 and R8, or all of R3, R4, R7 and R8 represent solubilising groups selected from the group consisting of: alkyl groups having 4 to 18 carbon atoms, halogens, halogenoalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted alkoxy groups having 6 to 18 carbon atoms, substituted or unsubstituted thioalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted aminoalkyl groups having 6 to 18 carbon atoms or substituted or unsubstituted trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups, the optional substituent being a halogen; wherein the residues R1 to R8 which do not represent a solubilising group are independently selected from hydrogen or an alkyl group having 1 to 4 carbon atoms; and wherein A1 and A2 independently represent a thieno group selected from one of the following formulae (VI) and (VII):

4. Anthrathiophene derivative according to claim 1, represented by General Formula (IV):

(IV) wherein either only one of the pairs R1 and R2, R3 and R7, or all of R1, R3, R2 and R7 represent solubilising groups selected from the group consisting of: alkyl groups having 4 to 18 carbon atoms, halogens, halogenoalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted alkoxy groups having 6 to 18 carbon atoms, substituted or unsubstituted thioalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted aminoalkyl groups having 6 to 18 carbon atoms or substituted or unsubstituted trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups, the optional substituent being a halogen; wherein the residues R1 to R8 which do not represent a solubilising group are independently selected from hydrogen or an alkyl group having 1 to 4 carbon atoms; and wherein A1 and A2 independently represent a thieno group selected from one of the following formulae (VI) and (VII):

5. Anthrathiophene derivative according to claim 1, represented by General Formula (V):

(V) wherein either only one of the pairs R1 and R2, R3 and R7, or all of R1, R3, R2 and R7 represent solubilising groups selected from the group consisting of: alkyl groups having 4 to 18 carbon atoms, halogens, halogenoalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted alkoxy groups having 6 to 18 carbon atoms, substituted or unsubstituted thioalkyl groups having 6 to 18 carbon atoms, substituted or unsubstituted aminoalkyl groups having 6 to 18 carbon atoms or substituted or unsubstituted trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups, the optional substituent being a halogen; wherein the residues R1 to R10 which do not represent a solubilising group are independently selected from hydrogen or an alkyl group having 1 to 4 carbon atoms; and wherein A1 and A2 independently represent a thieno group selected from one of the following formulae (VI) and (VII):

6. Anthrathiophene derivative according to any of claims 1 to 5, wherein only R1 and R2 represent solubilising groups selected from the group consisting of: alkyl groups having 4 to 18 carbon atoms; alkoxy groups having 6 to 18 carbon atoms; and trialkylsilyl groups comprising 4 to 16 carbon atoms in the alkyl groups.

7. Anthrathiophene derivative according to any of claims 1 to 6, wherein the solubilising groups are selected from the group consisting of: alkyl groups having 8 to 12 carbon atoms; alkoxy groups having 8 to 12 carbon atoms; and trialkylsilyl groups comprising 6 to 10 carbon atoms in the alkyl groups.

8. Anthrathiophene derivative according to any of claims 1 to 7, wherein the solubilising groups contained in the derivative are identical.

9. Anthrathiophene derivative according to claim 1, wherein the residues R1 to R10 neither being a solubilising group nor forming a thieno group are hydrogen.

10. Anthrathiophene derivative according to any of claims 2 to 5, wherein the residues R1 to R10 which do not represent a solubilising group are hydrogen and/or wherein both Ra and Rb are hydrogen.

11. Organic thin film comprising an anthrathiophene derivative according to any of claims 1 to 10.

12. Organic thin film according to claim 11, further comprising a polymer.

13. An electronic device or component comprising an organic thin film according to any of claims 11 or 12.

14. A solution for applying to the surface of a substrate to form a semiconducting portion on the substrate, the solution comprising an anthrathiophene derivative according to any of 1 to 10.

15. A method of manufacturing an electronic device or component, the method comprising applying a solution comprising an anthrathiophene derivative according to any of claims 1 to 10 to a substrate.