GB2334959A - Conducting polymers - Google Patents

Abstract

Polymers of Formula I are provided which may be incorporated in organic compositions for use as electrically conducting and electronically active materials. The compositions may be used in semiconductor devices such as organic light emitting diodes and photorefractive devices: wherein A, B and C are independently selected from phenyl and substituted phenyl wherein the substituents are independently selected from C 1 - C 8 alkyl, C 1 - C 8 alkoxy, C 1 - C 8 dialkylamino wherein the alkyl groups may be the same or different, diarylamino wherein the aryl groups may be the same or different, diarylaminophenyl and C 1 - C 8 alkylaryl amino wherein aryl shall be taken to denote a phenyl or naphthyl group optionally substituted with one C 1 - C 8 alkyl or alkoxy group; and n = 3 to 10,000.

Description

CONDUCTING POLYMERS This invention concerns new compounds and the use of such compounds in organic compositions as electrically conducting and electronically active materials. In particular it relates to the use of sidechain polymer systems comprising covalently linked polymer chains bearing electrically active organic substitution.

It is recognised that a variety of organic compounds can be made to conduct electricity.

The mechanism of electrical conduction may be either ionic conduction or electronic conduction. Ionic conduction is most important in blends of polymer materials with ionic compounds which may be regarded as solutes in the polymer. Movement of the ions under an applied electric field results in a flow of electric current. Typical materials in which ionic conductivity is important include blends of lithium salts in polymers such as poly(ethylene oxide).

Electronic conduction occurs in organic compounds even in the absence of addition of ionic salts. Various classes of organic compounds show this class of conduction, including conjugated polymers such as poly(acetylene), poly(phenylene vinylene) and poly(thiophene). This class of conduction is also found in molecular solids of low molecular mass such as N,N'-diphenyl-N,N'-ditolylbenzidine and aluminium tris 8hydroxyquinolinate. Polymers which do not posses a conjugated main chain structure can also show electronic conductivity. Such polymers include poly(vinyl carbazole) as a known example.

Electronic conduction in these organic compounds relies on the insertion of electrical charge into the materials. Such electrical charge may be introduced in a variety of known ways, including doping with an oxidising or reducing agent, by chemical doping with a charge transfer reagent, or by direct insertion of positive or negative electric charge from a conducting electrode. Known examples of such introduction of charge include the chemical doping of poly(acetylene) with the oxidising agent iodine, doping of poly(vinyl carbazole) with the charge transfer reagent trinitrofluorenone, and the injection of charge into evaporated thin films of 3-biphenyl-5-(4-t-butylphenyl)oxadiazole from a low.woi function electrode such as a magnesium metal electrode by applicationgf å,it#tative potential to the electrode. This injection of charge may also be regarded ata) f electrochemical reduction of the conducting material, or as electrochemical doping of the material. Other electronically conducting organic compounds may be subjected to charge injection by a positive potential, which is commonly applied via an electrode composed of a high work function metal such as gold. Such charge injection is commonly described as injection of positive charges denoted holes, and this description is understood to be equivalent to the extraction of electrons from the conducting material. A further route to generation of charge in organic solids is the ionisation of molecules of the solid under the influence of an electric field or of incident light, or both. In this case, an electron is removed from a molecule of the material, and captured by another molecule, or by a different part of the molecule. In this way, a pair of separated positive and negative charges is produced, movement of either or both of which may contribute to conduction in the material.

Conduction within electronically conducting organic solids involves, in practical materials, the transfer of electrical charge from one molecule to another. Such transfer of charge is described by a charge hopping or charge tunnelling mechanism which may allow an electron to overcome the energetic barrier between different molecules or molecular subunits. In systems such as conjugated polymers including poly(acetylene) and poly(phenylenevinylene) charge can also flow along the conjugated chain by movement of charged discontinuities in the regular bonding sequence of the polymer. In such cases, charge will normally be transferred through the bulk sample by a large number of individual molecules, and hopping or tunnelling remains an important mechanism.

The use of organic electrically conducting materials as semiconductors in the fabrication of electronic devices has been explored by many investigators. Field effect transistors have been fabricated from organic compounds such as poly(acetylene), pentacene, and poly(phenylenevinylene). Light emitting diodes have been demonstrated using a wide range of organic and molecular solids, including N,N'-diphenyl-N,N'-ditolylbenzidine, aluminium tris 8-hydroxyquinolinate, 3-biphenyl-5-(4-t-butylphenyl)oxadiazole and poly(phenylene vinylene). Preferably, such light emitting diodes are fabricated using at least two organic semiconductors which transport charge respectively by transport of holes and electrons. Such multilayer diodes attain higher efficiency than single layer devices, by trapping the charge carriers in the device until carrier recoerniition and wight emission can take place. Photovoltaic devices have been fabricated using.compvounds such as copper phthalocyanine and perylene bisbenzimidazole. Photoconductive materials have been prepared and are recommended for use as sensitive layers in electrophotography, photocopying and printing applications. Such photoconductive compositions include compositions based on poly(vinylcarbazole) doped with trinitrofluorenone.

Conducting polymers may be used as components of optical storage and switching equipment by using the photorefractive effect. Photorefractive layers combine the capacity for photogeneration of charge, transport of charge carriers by diffusion or under an applied field and a linear electro-optic coefficient. Such properties may be obtained by addition of selected dopants to a conducting polymer. Suitable dopants for inducing the capability for photogeneration of charge include C60 fullerene. Suitable dopants to provide a linear electro-optic coefficient include dimethylamino nitrostilbene.

Many shortcomings have been identified in organic conducting materials described in the prior art. Among these shortcomings, chemical stability is an important parameter.

Poly(acetylene), which shows a high electrical conductivity in the doped state, is converted to a non-conducting product on exposure to air, and must be handled and used in an inert atmosphere. Poly(phenylenevinylene) is believed to undergo oxidation of the conjugated double bonds in the main chain, yielding non-luminescent oxidation products.

Further degradation mechanisms have been identified or proposed for poly(phenylenevinylene) when it is incorporated in devices, including sensitivity to ambient ultraviolet radiation. Molecular solids such as N,N'-diphenyl-N,N'-ditolylbenzidine may undergo crystallisation, changes in morphology, or melting in operating devices. These effects may cause premature failure or loss in efficiency of the device.

A further important shortcoming which is common in many organic conducting materials rests in the difficulty and high cost of processing the materials. Both poly(acetylene) and poly(phenylenevinylene) are insoluble and infusible materials which are prepared for use in devices by use of a precursor polymer route. Typically a soluble precursor polymer is first synthesised and deposited onto a prepared substrate. A combination of heat and vacuum is then used to chemically convert the precursor polymer into the target product, usually with elimination of smaller volatile molecules of one or more by-products.

Processing of the target polymer to a dense film in bulk quantities requires critical control of this step which moreover entails the use of costly and time consuming vacuum processing stages. The final polymer is difficult to further process, and steps such as patteming and lithography are difficult to accomplish. Many attempts have been made to provide solution processable organic conductors. Substitution of alkyl, alkoxy and other flexible organic radical onto the polymers is understood to improve their solubility and processibiiity. Such substitution, however, may also commonly reduce the mobility of charges in the system, making the product less desirable for device preparation. Said substitution may also change the orbital energies of the system, altering the potential required for charge injection into the material.

Low molecular mass conducting organic materials must be deposited in thin uniform films for use in devices. Such films are commonly deposited by vacuum deposition onto the substrate from an electrically heated boat. This process is relatively time consuming and requires the use of costly high vacuum handling equipment. The time required for use of such equipment is relatively long due to the need for evacuation and outgassing of the materials and equipment at different stages in the process. Therefore this route does not provide means for low cost fabrication of organic semiconductor devices.

It has now been unexpectedly found that processable conducting organic polymers may be prepared by polymerisation of vinyl substituted triphenylamine derivatives.

Triphenylamine is a known organic conductor which is little used because of its poor solubility, poor glass forming capacity and low mobility of charge transport. Attempts have been made previously to incorporate triphenylamine derivatives in polymer structures, but this has involved the introduction of functional groups such as ester groups which may act as sites of chemical instability in the product. We have found that vinyl substituted triphenylamines may be polymerised to yield glass forming polymers which contain no additional functional groups which might compromise stability. We further surprisingly find that the charge mobility in such polymers is high and organic semiconductor devices fabricated from them provide excellent performance. Test devices show no sign of crystallisation of the triphenylamine polymer. Furthermore the polymers unexpectedly show excellent solubility in common solvents and may be processed into uniform films suitable for device fabrication simply by spin coating from solution. Said polymers therefore satisfy the requirements for fabrication of organic semiconductor devices in large areas by inexpensive and rapid processing methods.

According to this invention there is provided a polymer of general formula I:

Formula I wherein A, B and C are independently selected from phenyl and substituted phenyl wherein the substituents are independently selected from C1 - C8 alkyl, C1 - C8 alkoxy, C1 - C8 dialkylamino wherein the alkyl groups may be the same or different, diarylamino wherein the aryl groups may be the same or different, diarylaminophenyl and C1 - C8 alkylaryl amino wherein aryl shall be taken to denote a phenyl or naphthyl group optionally substituted with one C1 - C8 alkyl or alkoxy group; n = 3 to 10,000.

The structural and other preferences are expressed below on the basis of desirable charge transport characteristics, in particular an advantageous combination of electronic work function which is one factor determining the electric potential required to inject charge in to the polymer from a metallic or semiconducting electrode, charge carrier mobility, ease of synthesis from readily available and inexpensive starting materials, solubility, film forming ability and high physical and chemical stability of deposited films of the polymer in storage and in operating devices.

Preferably the substituents on the phenyl groups A, B, C are independently selected from methyl, dimethylamino, and diarylaminophenyl.

Preferably n is in the range 30 - 5000.

Overall preferred structures for formula I are those listed below: Poly(4-vinyl triphenylamine) Poly(N, N-di-4-dimethylaminophenyl 4-vinylaniline) Poly(N-phenyl N4-methoxyphenyl 4-vinylaniline) Poly(N-phenyl N4-dimethylaminophenyl 4-vinylaniline) Poly(NA-methylphenyl N4-dimethylaminophenyl 4-vinylaniline) Poly(N-phenyl N-4-diphenylaminophenyl 4-vinylaniline) Poly(N,N-di4-diphenylaminophenyl 4-vinylaniline) Poly(N,N, N'-triphenyl N'-4-styryl benzidine) Poly(N-phenyl N, N'-di-3-methylphenyl N'A-styryl benzidine) Poly(N-phenyl N, N'-1-naphthyl N'-4-styryl benzidine).

Compounds of formula I can be prepared by various routes. Typically the polymers are formed by polymerisation of a vinyl(triphenylamine), which may in turn be prepared by reaction of an iodobenzene with a diphenylamine. Either or both of these starting materials may bear appropriate substitution which is incorporated in the product triphenylamine. The reaction may with advantage be performed in the presence of finely divided copper at elevated temperatures in a solvent such as dibutyl ether, dichlorobenzene etc, according to procedures known in the art and described, for example, by Grimley et al (Org Magn Reson, 15, 296, (1981)), or by Gauthier et al (Synthesis, 4, 383, (1987)). Vinyl substitution on the triphenylamine may be achieved either by use of a vinyl substituted iodobenzene or vinyl substituted biphenyl in the above reaction, or by substitution of a vacant site on the triphenylamine, or by transformation of another functional group.

An advantageous approach to the synthesis of vinyltriphenylamine monomers uses the coupling of 4-iodo bromobenzene with an optionally substituted diphenylamine in the presence of finely divided copper. The resulting bromo triphenylamine is converted to a Grignard derivative by treatment with magnesium metal in tetrahydofuran, and reacted with vinyl bromide to yield the desired product.

Other approaches to the synthesis of vinyltriphenylamines will be evident to those skilled in the art, and may be used with advantage according to the particular nature and pattem of substitution which is desired.

Polymerisation of the vinyltriphenylamine monomer to form the polymer of structure 1 may be accomplished by known means of ionic or free radical polymerisation.

The invention will now be described with reference to the following diagrams by way of example only: Figure 1 illustrates an Organic Light Emitting Diode (OLED) device incorporating the materials of the present invention.

Figure 2 is a plan view of a matrix multiplex addressed device of Figure 1.

Figure 3 illustrates current/voltage characteristics for a material of the present invention used in an OLED device.

Figure 4 shows the luminance versus current density measured for several organic light emitting diodes fabricated according to Example 2.

Unless otherwise stated all reagents used are commercially available from the Aldrich Chemical Company.

The following compounds are illustrative examples which have been synthesised according to the present invention: Example 1 Synthesis of 4-Acyl.Triphenylamine 4-Acyl-triphenylamine was prepared by the acylation of triphenylamine using acetyl chloride and anhydrous zinc chloride as catalyst according to a previously published procedure- see CJ Fox and AL Johnson, J. Org. Chem., 1964, 29, 3536.

Synthesis of 4-Vinyl-Triphenylamine 4-Acyl-triphenylamine (31.69, 0.110 mol) and Al(O'Pr)3 (44.5, 0.220 mol) were suspended in xylene (100 ml) and refluxed for 3 hours. During this period nitrogen was passed through the reaction vessel and up the condenser to remove acetone produced during the reaction. The solution was cooled and poured into water producing a white precipitate of aluminium salts which were removed by filtration. The layers were separated, the aqueous layer washed with diethyl ether (2 x 150 ml), the organic extracts combined, dried over MgSO4, and solvent removed in vacuo to give a yellow solid. This solid was recrystallised from hexane (100ml) cooled to -78 C to yield a white solid which was collected by filtration and dried in vacuo (15.3 g, 0.056 mol, 51%).

'H NMR (200 MHz, CDC13) d 7.4 - 6.8 (m, 20H, aromatic CH), 6.67 (d of d, 3JHH 10.8 and 17.58 Hz, ArCHCH2), 5.65 (d, 3JHH 17.58 Hz, ArCHCH2 (trans)), 5.17 (d, 3JHH 10.9 Hz, ArCHCH2 (cis)) Elemental Analysis: C 88.43%, H 6.39%, N 5.16% (C20H17N requires C 88.52%, H 6.32%, N 5.10%).

Melting Point: 87.5-89 "C.

Purification of monomer 4-Vinyl-triphenylamine was purified by column chromatography on silica with hexane as an eluant. The solvent was removed and redissolved in sufficient degassed pentane just to dissolve the solid. The solution was stirred over activated charcoal and filtered under nitrogen. It was then stirred over calcium hydride and filtered under nitrogen, and finally stirred over silica and filtered under nitrogen. It was then cooled to -25 C and the white solid thus formed collected by filtration under nitrogen and dried under high vacuum for 7 days. From this point on the solid was handled in a nitrogen filled dry box.

Free Radical Polymerisation 4-Vinyl-triphenyl amine (0.469, 17mmol) and AIBN (7.6mg, 46 mol) was placed in an ampoule and dry, degassed benzene (5ml) condensed on to it under vacuum. The solution was then heated to 80 C for 10 hours, cooled and poured into methanol (50ml) precipitating polymer. The polymer was collected by filtration and dried under vacuum to yield 0.35g of polymer.

GPC Data: M" 5460; Mw 9940; PDI 1.82.

PDI is the Poly Dispersity Index and = Mwl M" Polymerisation of 4-Vinyl-Triphenylamine Benzene was dried by stirring over calcium hydride and was degassed by a freeze-thaw process. 4-Vinyl-triphenylamine was purified by column chromatography on silica with hexane as the solvent. The hexane was removed in vacuo and the solid dried under high vacuum for 2 days. All polymerisations were carried out under vacuum (10-6 mbar).

Typical Procedure: Benzene (60 ml) was condensed onto 4-vinyl-triphenylamine (1.50g, 5.5 mmol) under vacuum and sBuLi (32.5 mol, 1.3M solution in cyclohexane) added. A deep red colour formed immediately and the solution was stirred for 24 hrs. The colour disappeared immediately upon the addition of methanol (50 ul). The solution was poured into methanol causing the precipitation of white polymer which was recovered by filtration and dried under vacuum to yield 1.2 g of polymer.

GPC(THF): M". . 14,300; ZiVw 14,800; PDl: 1.03 GPC data for other polymers: #n #w PDI 3,200 8,800 2.1 2,600 9,400 3.6 Bimodal 2,200 2,600 1.2 The following compounds can be obtained analogously: Poly(N, N-di4-dimethylaminophenyl 4-vinylaniline) Poly(N-phenyl N4-methoxyphenyl 4-vinylaniline) Poly(N-phenyl N4-dimethylaminophenyl 4-vinylaniline) Poly(NA-methylphenyl N-4-dimethylaminophenyl 4-vinylaniline) Poly(N-phenyl NA-diphenylaminophenyl 4-vinylaniline) Poly(N,N-di-4-diphenylaminophenyl 4-vinylaniline) Poly(N,N, N'-triphenyl N'4-styryl benzidine) Poly(N-phenyl N, N'-di-3-methylphenyl N'4-styryl benzidine) Poly(N-phenyl N, N'-1-naphthyl N'4-styryl benzidine) Poly(N, N-di- 1 -naphthyl 4-vinylaniline) Poly(N-4-dimethylaminophenyl N-4-diphenylaminophenyl 4-vinyl aniline).

The materials described by the current invention may used in a variety of devices. By way of example an Organic Light Emitting Diode (OLED), which is a type of semiconductor device, suitable for incorporating materials of the present invention is illustrated in Figure 1. The device comprises two electrodes 1 a, 1 b, at least one of the electrodes is transparent to light of the emission wavelength of a layer of organic material 3. The other electrode may be a metal, for example Mg, Li, Ca, Al or an alloy of metals, for example MgAg, LiAI or a double metal layer, for example Li and Al or Indium Tin Oxide (ITO). One or both electrodes 1 a, 1 b may consist of organic conducting layers. A processing surface or substrate 2 may be made of any material which is flat enough to allow subsequent processing, for example glass, silicon, plastic. The substrate 2 may be transparent to the emitted radiation of the organic material 3. Alternatively one of the electrodes 1 a, 1 b may be transparent instead. Sandwiched between the electrodes 1 a and 1 b is a layer of organic material 3 which may itself consist of one or more layers represented here as 3a, 3b, 3c. The layer of organic material 3 possesses the following three properties: electron transporting (ET); hole transporting (HT); light emitting (LE). The materials described by the current invention are suitable for use as hole transporters. If the layer of organic material 3 is a single layer then the single layer of organic material 3 must exhibit all three properties. For the case when the layer of organic material 3 is a single layer then the organic material may consist of a single material, for example polyphenylenevinylene, or by mixing two or more materials with appropriate properties together, for example N,N'diphenyl-N,N'-ditolylbenzidine (HT), Coumarin 6 Laser dye (LE) and t-Butylphenyl 4biphenylyl-oxadiazole (ET) which may be abbreviated to PBT. For the case when the layer of organic material 3 comprises more than one layer then suitable examples include: il 3a = HT layer, 3b = LE layer, 3c = ET layer ii/ 3a = HT layer, 3b = material which acts as an ET medium but also emits light, for example Aluminium tris 8hydroxyquinolinate (Alq3) iii/ 3a = HT and LE, 3b = ET iv/ The LE material may be doped in small quantities - typically 0.5% into ET or HT or both. Typical doping agents are coumarin 6 or pentaphenyl cyclopentadiene.

Preferably in the case where the layer of organic material 3 is a multiplicity of layers, then the layer adjacent to the cathode preferentially transports electrons and/or the layer adjacent the anode preferentially transports holes. Preferably the luminescent material has a high quantum efficiency of luminescence. The luminescent component may be combined with a charge transporting material or may be present in a separate layer.

The layer of organic material 3 may be deposited on the electrode I a by any of the following techniques: thermal evaporation under vacuum, sputtering, chemical vapour deposition, spin depositing from solution or other conventional thin film technology.

The thickness of the layer of organic material 3 is typically 30-2000nm, preferably 50500nm.

The device may contain layers 4a and 4b which are situated next to the electrodes la and 1 b, these layers 4a and 4b may be conducting or insulating and act as a barrier to diffusion of the electrode material or as a barrier to chemical reaction at the electrode 1 a, 1 b and layer of organic material 3 interface. Examples of suitable materials for 4a and 4b include emeraldine which prevents indium diffusion into the layer of organic material 3 from an ITO electrode, or, for the same reason, copper phthalocyanine may be used; alternatively the addition of a thin layer (~0.5cm) of lithium or magnesium fluoride at the interface between a lithium electrode and the layer of organic material 3 may be used.

The device of Figure 1 may be a singe pixel device or it may be matrix addressed. An example of a matrix addressed OLED is shown in plan view in Figure 2. The display of Figure 2 has the internal structure described in Figure 1 but the substrate electrode 5 is split into strip-like rows 51 to 5m and similar column electrodes 61 to 6n, this forms an mxn matrix of addressable elements or pixels. Each pixel is formed by the intersection of a row and column electrode.

A row driver 7 supplies voltage to each row electrode 5. Similarly, a column driver 8 supplies voltage to each column electrode. Control of applied voltages is from a control logic 9 which receives power from a voltage source 10 and timing from a clock 11.

The following illustrates a method of device fabrication incorporating the material prepared in Example 1.

Example 2 - Device Fabrication 5% by weight of the polymer described in Example 1 was dissolved in dichorobenzene.

The solution was deposited on to an indium tin oxide coated glass slide which was then spun at 1000rum for 30s. The substrate was removed from the spinner and placed on a hotplate at 70"C for 1 Omins to drive off the residual solvent. A uniform polymer film was deposited by this means. The film thickness obtained was 100no, and constitutes the hole transport layer 3a shown in Fig 1. The polymer coated substrate was transferred to a vacuum evaporation apparatus, then coated with a layer of 50nm of naphthalene-1,8methoxybenzimidazole (a mixture of 3-methoxy and 4-methoxy isomers) by thermal evaporation under a pressure of 1-2x10-6 Torr at a rate of ca. 0.4 nm/second. This layer serves as a luminescent layer which is also capable of transporting electrons in the device. A layer of 100nm aluminium was then deposited by thermal evaporation under high vacuum through an evaporation mask. The mask was patterned with a series of 5mm diameter circular holes, resulting in an array of circular electrode pads deposited on the organic layers. The sample was removed from the vacuum chamber and electrical connections were made using indium solder to contact to the ITO and gallium-indium mixture to contact the aluminium pads. Each device defined by the area of metallisation of one aluminium pad was found to function both as a rectifier and as a light emitting diode.

The current/voltage (IN) characteristics shown in Figure 3 for a representative device are highly asymmetric with rectification ratios of 500. Above an applied potential difference of 21V, with the aluminium layer the negative electrode, bright emission of light is visible.

The photoluminescent (PL) and electroluminescent (EL) spectra obtained from such a sample show peaks at ca. 580nm.

Polyvinyl(triphenylamine) (PVTPA) was synthesised using living polymerisation as described earlier in the description, to give a polymer with a polydispersity of 1.03. The material was readily soluble in dichlorobenzene and a 4.0% solution was used to coat four ITO coated slides with different thicknesses of the HT Layer (HTL). Further details of the PVTPA films are included in the Table below. The films were then coated with 51.1 nm of naphthalene-1 ,8-methoxybenzimidazole (a mixture of 3-methoxy and 4-methoxy isomers) and 100.8nm Al in processes as similar as possible to those already described.

Sample Name Spin Speed (rpm) Thickness of HTL (nm) SAS48 1000 87.5 SAS49 2000 49.0 SASSO 3000 36.5 SASS1 4000 21.0 Spin speed and layer thickness for poly(vinyl triphenylamine).

The compounds of the present invention may also be used in photosensitive devices for example photodiodes, photovoltaic cells, sensitive layers for electrophotography and photorefractive layers.

In the case where the conducting polymers of the current invention may be used as components of optical storage and switching equipment by use of the photorefractive effect then with reference to figure 1, the layer 3 comprises a layer of organic material having conductive, photogenerative and electro-optic properties. Such properties may be obtained by addition of suitable dopants to a conducting polymer as described by the present invention. Suitable dopants for inducing the capability for photogeneration of charge include C60 fullerene. Suitable dopants to provide a linear electro-optic coefficient include dimethylamino nitrostilbene.

Claims (9)

1. Claims 1. A polymer of Formula I:

   Formula I wherein A, B and C are independently selected from phenyl and substituted phenyl wherein the substituents are independently selected from Ci - C8 alkyl, Cj - C8 alkoxy, C - C8 dialkylamino wherein the alkyl groups may be the same or different, diarylamino wherein the aryl groups may be the same or different, diarylaminophenyl and C1 - C8 alkylaryl amino wherein aryl shall be taken to denote a phenyl or naphthyl group optionally substituted with one Ci - C8 alkyl or alkoxy group; n = 3 to 10,000.
2. 2. A polymer according to claim 1 wherein A and B and C are selected from substituted phenyl and the substituents are independently selected from methyl, dimethylamino and diarylaminophenyl.
3. 3. A polymer given by any of: Poly(4-vinyl triphenylamine) Poly(N , N-di4-dimethylaminophenyl 4-vinylaniline) Poly(N-phenyl N-4-methoxyphenyl 4-vinylaniline) Poly(N-phenyl N4-dimethylaminophenyl 4-vinylaniline) Poly(N-4-methylphenyl N-4-dimethylaminophenyl 4-vinylaniline) Poly(N-phenyl N-4-diphenylaminophenyl 4-vinylaniline) Poly(N , N-di-4-diphenylaminophenyl 4-vinylaniline) Poly(N,N, N'-triphenyl N'-4-styryl benzidine) Poly(N-phenyl N, N'-di-3-methylphenyl N'4-styryl benzidine) Poly(N-phenyl N, N'-l-naphthyl N'-4-styryl benzidine).
4. 4. A polymer according to any of claims 1 or 2 or 3 wherein n = 30-50000.
5. 5. An organic semiconductor device comprising a substrate bearing an organic layer sandwiched between electrode structures wherein the organic layer comprises a polymer according to any of claims 1,2,3 or 4.
6. 6. An organic semiconductor device according to claim 5 wherein the organic layer further comprises an organic conducting material capable of selectively transporting electrons.
7. 7. An organic semiconductor device according to either of claims 5 or 6 wherein the organic layer further comprises a luminescent organic material.
8. 8. A device according to any of claims 5,6 or 7 wherein the device is an organic light emitting diode device.
9. 9. A photorefractive device comprising a substrate bearing an organic layer sandwiched between electrode structures wherein the organic layer comprises a polymer according to any of claims 1,2,3 or 4.