WO2016126209A1 - P-doped electrically conductive polymeric materials for hole-injection and hole-extraction layers - Google Patents

Abstract

The invention provides high workfunction p-doped electrically conductive materials comprising one or more triarylaminium moieties counter-balanced by covalently bonded anions, and optionally further comprising one or more non-covalently attached cations. These materials can be used as hole-injection and hole-extraction layers to provide ohmic contacts to semiconductors with deeper ionization potentials than previously possible, up to the workfunction of the material.

Description

p-DOPED ELECTRICALLY CONDUCTIVE POLYMERIC MATERIALS FOR HOLE- INJECTION AND HOLE-EXTRACTION LAYERS

RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No.

62/111,330, filed on February 3, 2015. The entire teachings of the above application are incorporated herein by reference.

BACKGROUND

[0002] p-Doped electrically conductive polymers are π-conjugated organic polymers that have been p-doped to an electrically conductive state. This is achieved using a p-dopant, which is a strong oxidant or a strong acid, to introduce mobile positive charges, called holes, into the conjugated segments of the polymer. These holes need to be counterbalanced by anions in the material, called "counter- anions". Because the holes are charged and are mobile, the material is capable of conducting electricity, often having an electrical conductivity between 10^~6 to 10² Scm^-1.

[0003] Some p-doped polymers can be processed from solution into layers which have an ability to also inject holes into and extract holes from some semiconductors. The layers performing these functions are called hole-injection layers (HILs) and hole-extraction layers (HELs) respectively. The semiconductors may be an organic material, or an inorganic material including, for example, quantum dots, nanowires, fullerenes, carbon nanotubes, graphene, 2D materials and soft inorganic crystals for example perovskites. The resultant semiconductor devices include, for example, diodes, light-emitting diodes, field-effect transistors and solar cells. [0004] Besides electricity conductivity, the workfunction of the HIL and HEL plays a key role in determining its efficiency for hole injection and extraction respectively. The workfunction (WF) is the difference in energy between the Fermi level and the vacuum level of the material. Workfunctions larger than about 5.0 eV are referred to as "high"

workfunctions. Workfunctions larger than about 5.2 eV are referred to as "ultrahigh" workfunctions. The difference between WF of the HIL and valence band edge of the adjacent semiconductor, measured with respect to a common energy reference, gives the thermodynamic barrier for hole injection from the HIL into the semiconductor.

[0005] For efficient hole injection, the contact between the HIL and the semiconductor layer should have a low hole-injection resistance. An ideal hole contact would have negligible hole-injection resistance compared to the resistance in the bulk of the

semiconductor. Such a contact is called an ohmic hole contact. Forming ohmic contacts is crucial to achieving high device efficiency and reliability, and is thus a fundamental objective in device technology.

[0006] To achieve an ohmic hole contact, the HIL needs to be able to inject the required high density of holes into the semiconductor layer, so that the applied voltage is used primarily to transport them across the bulk of the semiconductor. This often requires the HIL to have a sufficiently large WF that approaches or exceeds the ionization potential (I_p) of the semiconductor. In contrast, a non-ohmic hole contact demands a significant electric field to inject holes across the interface. This not only lowers device efficiency, but also degrades device reliability and stability. Similar considerations also apply to the hole-extraction contact.

[0007] Numerous organic and inorganic semiconductors of interest however have an I_p that is larger than 5.2 eV. These HILs are found to not form satisfactory hole contacts to these semiconductors. Such challenges exist across a wide variety of device technologies, including the entire spectrum of organic semiconductor device technologies, including organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic solar cells. For OLEDs, many green-emitting and blue-emitting materials have I_p > 5.2 eV. The present art requires a complex cascade hole injection scheme to deliver holes into these deep- Ip materials. The injection is still not fully ohmic. For OFETs, most of the recent air- stable semiconductors of interest, such as the diketopyrrolopyrrole materials, also have I_p > 5.2 eV. The usual gold contacts do not provide ohmic characteristics for these materials. For organic solar cells, the new photoactive materials developed also often have I_p > 5.2 eV. The lack of suitable HELs with sufficiently deep WFs to contact these semiconductors is one of the factors that limit the open-circuit voltage, fill factor, and power conversion efficiency of these devices.

[0008] Furthermore, the counter-anions should preferably be immobilized within the HIL (or HEL) so that they cannot diffuse into the adjacent semiconductor layer. If the counter- anions can migrate through the semiconductor, the holes would also migrate, and this would degrade the hole-doping profile, which is the variation of hole density with location in the semiconductor. Stability of the doping profiles correlates to the stability of the device characteristics. The doping profile should not degrade during processing, storage and operation of the device. At the time of this invention, there was still a need for a general design and strategy of a new class of p-doped polymers that could achieve HILs and HELs with high workfunctions greater than about 5.0 eV, preferably ultrahigh WFs greater than about 5.2 eV, and up to about 6.2 eV, and which substantially meet the aforesaid criteria. This would enable the appropriate HILs and HELs to be selected to provide ohmic contacts to the desired semiconductor with a deeper ionization potential (I_p) than previously possible, up to the workfunction of the p-doped material.

SUMMARY OF THE INVENTION

[0009] The present invention is concerned with providing a new class of p-doped polymers. More specifically, the present invention is concerned with providing design and strategy for achieving p-doped materials with high workfunctions greater than about 5.0 eV, preferably ultrahigh WFs greater than about 5.2 eV, and up to about 6.2 eV.

[0010] The present invention provides a class of p-doped materials comprising triarylaminium moieties and covalently-attached counter-anions, and optionally further comprising one or more noncovalently attached cations, and their undoped precursors, that can give the desired high workfunction, electrical, processing and stability characteristics. These materials can provide ohmic hole injection and extraction contacts to semiconductor materials with deeper I_p (i.e., I_p greater than about 5.0 eV) than previously possible, up to the workfunction of the p-doped material. Furthermore, they are sufficiently stable under ambient conditions for processing devices. This typically requires the key properties of the material to be substantially unchanged, when exposed to the ambient conditions for a period of time ranging from approximately tens of minutes to approximately an hour. [0011] In a first aspect, the invention provides a material comprising a p-doped electrically-conductive polymer or oligomer comprising one or more triarylaminium moieties, and one or more counter-anions covalently bonded to said polymer or oligomer, or to a second polymer or oligomer, wherein the one or more triarylaminium moieties optionally comprises one or more heteroatoms, and wherein the polymer is p-doped to a density of about 0.1 to about 1 hole per triarylamine moiety, and the polymer is capable of forming a film having a workf unction of from about 5.0 eV to about 6.2 eV.

[0012] In an embodiment of the first aspect, the triarylaminium moieties form a fully conjugated polymer, a partially conjugated polymer, or pendant groups on a polymer.

[0013] In another embodiment of the first aspect, the triarylamine moieties, prior to doping, are selected from optionally substituted N,N-diphenyl(N-phenyl)amine-4,4'-diyl, optionally substituted 9-phenylcarbazole-3,6-diyl, optionally substituted 9- phenylphenoxazine-3,7-diyl, optionally substituted 10-phenylphenothiazine-5-oxide-3,7-diyl, optionally substituted N,N'-diphenylene(N,N'-diphenyl)-l,4-phenylenediamine, or optionally substituted N,N'-diphenylene(N,N'-diphenyl)4,4'-diphenylenediamine, wherein substitutions are one or more selected from hydrogen, alkyl, cycloalkyl, phenyl, substituted phenyl, alkoxy, phenoxy, substituted phenoxy, alkylthio, phenylthio, substituted phenylthio, fluorine, cyano, nitro, alkylketo, trichloromethyl or trifluoromethyl.

[0014] In another embodiment of the first aspect, one or more co-monomers of the polymer or oligomer comprise fluorene, indenofluorene, phenylene, arylene vinylene, thiophene, azole, quinoxaline, benzothiadiazole, oxadiazole, thiophene, arylamine or bisphenol-A; or optionally substituted fluorene, indenofluorene, phenylene, arylene vinylene, thiophene, azole, quinoxaline, benzothiadiazole, oxadiazole, thiophene, arylamine or bisphenol-A.

[0015] In another embodiment of the first aspect, the counter-anions are selected from sulfonate, fluoroalkylsulfonate, trifluoromethylsulfonylimide, fluoroalkylsulfonylimide, carboxylate, fluoroalkylcarboxylate, phosphonate, fluoroalkylphosphonate, phosphate, sulfate, or a combination thereof. These can be covalently attached to the triarylamine polymer or oligomer, on the triarylamine moieties or the co-monomer moieties; or on a second polymer or oligomer optionally comprising one or more triarylaminium moieties.

[0016] In another embodiment of the first aspect, the material further comprises one or more non-covalently attached cations, wherein the cations are selected from Li⁺, Na⁺, K⁺, Cs⁺, NH₄ ⁺, R₄N⁺ where R is Ci-Ci₂ alkyl or phenyl, R₃S⁺ where R is Ci-Ci₂ alkyl or phenyl, R tP^"1" where R is Ci-Ci₂ alkyl or phenyl, or an aromatic heterocycle-containing cation. The aromatic heterocycle cations are preferably selected from pyridinium, imidazolium, pyrrolium or pyrylium.

[0017] In another embodiment of the first aspect, the polymer or oligomer, prior to doping, is selected from

-6-

where n is at least 5, preferably at least 10; where m is at least 5, preferably at least 10; where M⁺ are non-covalently attached cations.

[0018] In an embodiment of the first aspect, the holes are fully self-compensated by the covalently-bonded counter- anions .

[0019] In other certain embodiments of the first aspect, the material may possess any one or more of the following characteristics: (i) the undoped precursor has p-dopable π- conjugated segments that have I_p larger than about 5.0 eV and up to about 6.2 eV; (ii) the material is p-doped to an electrically-conductive state with electrical conductivity greater than about 10^~5 S cm^-1 to provide sufficient conductance across the layer thickness and WF greater than about 5.0 eV; (iii) counter-anions to charge-balance the holes are covalently bonded to the triarylaminium polymer or oligomer, or a second polymer or oligomer; (iv) the material has non-covalently attached cations which can be selected to give the desired solvent processability characteristics; and/or (v) the material has suitable solvent processing characteristics compatible with the presence of underlying layers, and with the deposition of overlayers, so that layers of these materials can be fabricated into devices. In other certain embodiments of the first aspect, the material may be obtained from one or more of the following steps: (i) the undoped precursor is doped using a strong oxidant, and the oxidant by-product subsequently removed from the material so that the holes are counter-balanced by the bonded anions; (ii) the undoped precursor is pre-doped in solution and purified to give processable p-doped solutions wherein the holes are substantially counter-balanced by the bonded anions; (iii) the undoped precursor is post-doped after film-formation and purified to give the final p-doped state in which the holes are substantially counter-balanced by the bonded anions.

[0020] In a second aspect, the invention provides a composition comprising the material of the first aspect and a polymer diluent.

[0021] In a third aspect, the invention provides a method of making the material of the first aspect, the method comprising p-doping a polymer or oligomer with a p-dopant, followed by removing excess ions via a solvent, wherein the p-dopant is a one-electron oxidant with a formal oxidation potential larger than about 0.8 V.

[0022] In a fourth aspect, the invention provides a layer comprising a p-doped electrically-conductive polymer or oligomer comprising one or more triarylaminium moieties, wherein the polymer or oligomer is in the form of a layer, and one or more counter- anions covalently bonded to said polymer or oligomer, or to a second polymer or oligomer, wherein the workfunction of the layer is from about 5.0 eV to about 6.2 eV.

[0023] In a fifth aspect, the invention provides a layer comprising a p-doped electrically- conductive polymer or oligomer comprising one or more triarylaminium moieties, wherein the polymer or oligomer is in the form of a layer, and one or more counter-anions covalently bonded to said polymer or oligomer or to a second polymer or oligomer, wherein the layer is capable of hole-injection into or hole-extraction from a semiconductor having a ionization potential of at least about 5.0 eV, and preferably at least about 5.2 eV.

[0024] In an embodiment of the fifth aspect, the holes are fully self-compensated by the covalently-bonded counter-anions .

[0025] In a sixth aspect, the invention provides a method of fabricating the layers of the fourth and/or fifth aspect, the method comprising depositing a solution of the p-doped polymer or oligomer, or depositing a solution of the undoped polymer or oligomer, to form a layer, followed by p-doping with a p-dopant, and removing excess ions.

[0026] In a seventh aspect, the invention provides a device comprising the layers of the fourth and/or fifth aspect.

BRIEF DESCRIPTION OF THE DRAWINGS AND SCHEMES

[0027] FIG. 1 shows UV-Vis-NIR spectra of undoped mTFF-F3S0₃Na (dotted line) and self-compensated p-doped mTFF-F3S0₃Na (solid line). [0028] FIG. 2 shows I-V characteristics of OLED pixels with device geometry of ITO/ HIL/ 86 nm 9,9-dioctylfluorene/ 120 nm Al, using a self-compensated /?-doped HIL produced according to the present invention illustrated in Example 4a.

[0029] FIG. 3 shows I-V characteristics of OLED pixels with device geometry of ITO/ HIL/ 86 nm F9,9-dioctylfluorene/ 120 nm Al, using a prior art HIL (PEDT:PSSH).

[0030] FIG. 4 shows I-V characteristics of an OLED pixel with device geometry of ITO/ HIL/ 80 nm 9,9-bis(p-octylphenyl) fluorene/ 120 nm Ag, using a self-compensated /?-doped HIL produced according to the present invention illustrated in Example 4d.

[0031] FIG. 5 shows I-V characteristics of an OLED pixel with device geometry of ITO/ HIL/ 80 nm 9,9-bis(p-octylphenyl) fluorene/ 120 nm Ag, using different HILs, including a prior art HIL (PEDT:PSSH) and a self-compensated /?-doped HIL produced according to the present invention illustrated in Example 4e.

[0032] FIG. 6 shows a schematic of an organic field effect transistor with a monolayer of self-compensated /?-doped HIL assembled on the Au electrode, produced according to the present invention illustrated in Example 4h.

[0033] FIG. 7 shows the transfer characteristics of the transistors based on a prior art structure and a structure with a self-compensated /?-doped HIL. Drain voltage is stepped from 0 to -20 V in -2.5 V steps.

[0034] Scheme la depicts synthesis of an alternating copolymer of N,N-diphenyl(N-(m- trifluoromethyl)phenyl)amine-4,4'-diyl and disodium 9,9-bis(3-sulfonatopropyl)fluorene-2,7- diyl (mTFF- F3S0₃Na).

[0035] Scheme lb depicts synthesis of an alternating copolymer of N,N-diphenyl(N-(p- sec-butyl)phenyl)amine-4,4'-diyl and disodium 9,9-bis(3-sulfonatopropyl)fluorene-2,7-diyl (TFB-F3S0₃Na).

[0036] Scheme lc depicts synthesis of an alternating copolymer of N,N-diphenyl(N-(p- sec-butyl)phenyl)amine-4,4'-diyl and bis(tetramethyammonium) 9,9-bis(3- sulfonatopropyl)fluorene-2,7-diyl (TFB -F3 S 0₃TMA) .

[0037] Scheme Id depicts synthesis of an alternating copolymer of N,N-diphenyl(N-(p- methoxy)phenyl)amine-4,4'-diyl and disodium 9,9-bis(3-sulfonatopropyl)fluorene-2,7-diyl (TFOMe-F3S0₃Na). [0038] Scheme le depicts synthesis of an alternating copolymer of N,N-diphenyl(N- phenyl)amine-4,4'-diyl with different substituents on the pendant N-phenyl ring and disodium 9,9-bis(3-sulfonatotetrafluoroethyl)fluorene-2,7-diyl (TAAx-F2fS0₃Na).

[0039] Scheme If depicts synthesis of an alternating copolymer comprising one unit of N,N-diphenyl(N-phenyl)amine-4,4'-diyl with alkoxysulfonate side chain and three units of 9,9-bis[2-[2-(2-methoxyethoxy)ethoxy]ethyl]-9H-fluorene-2,7-diyl (TFOC3S0₃Na-3FEG).

[0040] Scheme lg depicts synthesis of an alternating copolymer of N,N-diphenyl(N-(m- trifluoromethyl)phenyl)amine-4,4'-diyl and dicesium 9,9-bis(3- trifluoromethanesulfonylimidopropyl)fluorene-2,7-diyl (mTFF-F3TFSICs).

[0041] The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0042] The present invention is concerned with providing a new class of p-doped polymers. More specifically, the present invention is concerned with providing design and strategy for achieving p-doped materials with high workfunctions greater than about 5.0 eV, preferably ultrahigh workfunctions greater than about 5.2 eV, and up to about 6.2 eV.

[0043] The term "about" as used herein with respect to workfunction refers to ± 0.1 eV.

[0044] The present invention provides high workfunction p-doped electrically-conductive materials comprising triarylaminium moieties with covalently-attached counter- anions, and their undoped precursors. The IUPAC name for aminium (common name) is ammoniumyl. The common name aminium will be used throughout this document. The materials comprise polymers and/or oligomers. Polymers are macromolecules of relatively high molecular weights of more than 5 kDa, with typically more than ten identical or dissimilar monomer units bonded together. Oligomers are macromolecules of relatively low molecular weights of 5 kDa or less, with typically at least two and up to ten identical or dissimilar monomer units bonded together.

[0045] Without thereby being limited by theory, the materials are p-doped to give holes on the triarylaminium moieties. These materials are surprisingly stable in the p-doped state even for ultrahigh workfunctions between about 5.2 and about 6.2 eV, where oxidation of water becomes thermodynamically favorable.

[0046] These holes are furthermore counterbalanced by anions covalently-bonded to the material. The counter- anion may be bonded to the polymer and/ or oligomer containing the triarylaminium units, or may be bonded to another polymer and/or oligomer provided specifically for the counter- anions.

[0047] Without thereby being limited by theory, the bonded counter-anions have severely restricted diffusion, which limits the possibility for degradation or scrambling of the desired doping profile during processing, storage and device operation. This stabilizes its hole- injection and extraction characteristics.

[0048] Optionally, the bonded counter-anions are present in excess, wherein the excess is counter-balanced by one or a plurality of associated but non-bonded cations, which are referred to as spectator cations. Thus, in some aspects the material comprises the p-doped electrically-conductive material with bonded counter-anions and one or a plurality of non- bonded spectator cations. The incorporation of spectator cations may be advantageous to modify the solvent processing (e.g., solubility and viscosity) characteristics of the material.

[0049] The presence of non-bonded spectator cations does not result in instability of the doping profile unlike the case with non-bonded counter-anions. This is because the non- bonded anions can diffuse or migrate together with the holes as neutral entities, thereby facilitating hole transfer to an adjacent undoped region, whereas the non-bonded cations cannot diffuse or migrate together with the holes as neutral entities.

[0050] Optionally, one or a plurality of polymer diluents may be advantageously incorporated to give a composition that comprises the p-doped electrically-conductive material with bonded counter-anions and optionally with one or a plurality of non-bonded spectator cations, and one or a plurality of polymer diluents. The incorporation of polymer diluents may be advantageous to modify the hole density, injection characteristics and absorption characteristics of the composition.

[0051] To generate the p-doped materials and compositions, optionally in a separate step after synthesis, a strong oxidant (also called p-dopant) is applied to accomplish p-doping of the material, and then an ion removal process is applied to remove excess ion pairs and enforce self-compensation. These two steps of doping and ion removal can be performed sequentially or simultaneously. [0052] Solution-state doping vs film-state doping.

[0053] These two steps may be performed on the undoped precursor material in solution to generate the self-compensated p-doped material in solution. This is called solution-state doping method. The p-doped materials can then be deposited and patterned on the desired substrate by spin-casting, inkjet printing, doctor blading, self-assembly or other suitable methods.

[0054] Alternatively, the two steps may be performed on films of the undoped precursor material that has been deposited and patterned on the substrate by a suitable method described above, including a layer-by-layer polyelectrolyte assembly. In the layer-by-layer polyelectrolyte assembly, a polycation and polyanion are alternately assembled by adsorption on the substrate to build the film. In addition, a photolithography patterning method may be used. In this method, the film may contain photocrosslinkable moieties which are activated by light illuminated through a mask to pattern the film. Alternatively, the film may be patterned by etching or dissolving away areas exposed by a photoresist mask layer that has first been fabricated on the film. The film is then exposed to the p-dopant in solution and then to a suitable pure solvent to accomplish the ion-removal step. This is called film-state doping method.

[0055] Undoped Precursor Material

[0056] The undoped precursor material comprises triarylamine units. These moieties may be a part of the polymer backbone or may be present as a pendant unit attached to a polymer backbone.

[0057] Polymer structure: If the triarylamine moiety is part of the polymer backbone, it may form a fully-conjugated polymer optionally with other repeating units. These include oxygen, sulphur, aromatic, and/or heteroaromatic units, such as fluorene, indenofluorene, phenylene, arylene vinylene, thiophene, azole, quinoxaline, benzothiadiazole, oxadiazole, thiophene, and arylamine. An example of a fully-conjugated copolymer formed with another repeating unit is the polymer represented by the two repeating units N,N-diphenyl(N- phenyl)amine-4,4'-diyl and 9,9-dialkylfluorene-2,7-diyl.

[0058] Alternatively, the triarylamine moiety may form a partly-conjugated polymer that is interrupted along its backbone by non-conjugating units. Such units include bisphenol-A, methacrylate, siloxane, and meta-linked benzene. An example of a partly-conjugated polymer copolymer is the polymer formed by the two repeating units N,N-diphenyl(N- phenyl) amine-4,4'-diyl and bisphenol-A.

[0059] Alternatively, the triarylamine moiety could be a pendant group attached to a polymer backbone. Examples of polymer backbones include poly(methacrylate), and vinyl polymers. The choice is determined by the desired, molecular packing, processing characteristics and the electronic levels of the material, in particular its I_p. The polymer molecular weight can be about 8 kDa to about 200 kDa, and more preferably about 30 kDa to about 200 kDa.

[0060] Triarylamine moiety: The triarylamine moiety refers to a trivalent amine unit that is trisubstituted with three identical or dissimilar aromatic units. These units may not be linked other than through the nitrogen atom, as exemplified by the prototype N,N- diphenyl(N-phenyl)amine-4,4'-diyl. Optionally, these units may be linked, as exemplified by the prototype 9-phenylcarbazole-3,6-diyl. Linking the units will planarize a portion of the moiety, and beneficially improve stability during device operation, and alter the I_p of the resultant material.

[0061] Aromatic units: The aromatic units may contain only carbon atoms in the molecular framework. Optionally, they may also contain heteroatoms including oxygen, nitrogen or sulfur or other atoms, as exemplified by the prototypes 9-phenylphenoxazine-3,7- diyl and 10-phenylphenothiazine-5-oxide-3,7-diyl. Heteroatoms may beneficially reduce the chemical reactivity of the rings, the stability during device operation, and I_p of the resultant material.

[0062] Optionally, the triarylamine moiety may also be in the form of "dimers" and higher multimers, as exemplified by the prototypes N,N-diphenylene(N,N'-diphenyl)-l,4- phenylenediamine and N,N'-diphenylene(N,N'-diphenyl)4,4'-diphenylenediamine moieties. These dimers and higher multimers may beneficially reduce the chemical reactivity of the rings, improve stability during device operation, and alter the I_p of the resultant material.

[0063] Furthermore the aromatic units could bear one or more substitutions in place of hydrogen, for example alkyl, cycloalkyl, phenyl and substituted phenyl groups to improve processability for intended application; alkoxy, phenoxy or substituted phenoxy groups to improve processability and downshift I_p; alkylthio, phenylthio or substituted phenylthio groups to improve processability and downshift I_p; fluorine, cyano, nitro, alkylketo, trichloromethyl or trifluoromethyl groups to improve processability and upshift I_p. [0064] Upshifting I_p will tend to make workfunction of the resultant p-doped material larger, while downshifting I_p will tend to make it smaller. In this way, the I_p of the undoped precursor material could be varied between about 4.8 eV and about 6.5 eV, preferably between about 5.0 and about 6.2 eV, more preferably between about 5.2 and about 6.2 eV.

[0065] The term "about" as used herein with respect to I_p refers to + 0.1 eV.

[0066] The alkyl part can comprise 1 to 10 carbons atoms. Examples of straight-chain and branched-chain alkyl groups having 1-4 carbon atoms are methyl, ethyl, n-propyl, iso- propyl, n-butyl, and t-butyl.

[0067] Substitutions in particular at the p-position may be beneficial to block undesired reactivity when the polymer is p-doped.

[0068] Selection of π-conjugated structure of the polymer. Through the combination of any or all of the above, the I_p of the material can be tuned between about 4.8 eV and about 6.5 eV, preferably between about 5.0 and about 6.2 eV, more preferably between about 5.2 eV to about 6.2 eV, as illustrated here with two families of materials. For an alternating copolymer of 9,9-dialkylfluorene-2,7-diyl and N,N-diphenyl(N-substitutedphenyl)amine-4,4'- diyl, the I_p values of polymers for the following substitutions on the N-phenyl ring are: p- methoxy 5.3 eV, p-sec-butyl 5.5 eV, m-trifluoromethyl 5.8 eV, p-trifluoromethyl 6.3 eV. The workfunctions obtained for the corresponding heavily-p-doped polymer with 0.8 holes per repeat unit is 5.2 eV, 5.5 eV, 5.7 eV and 5.8 eV respectively, using hexafluoroantimonate as a model counter- anion. With a larger model counter-anion, tetrakis( 1,3,5- trifluromethylbenzene)borate, the corresponding workfunction increases by 0.3 eV to reach 6.1 eV for the last mentioned polymer. A larger anion or an anion spaced further away from the hole tends to increase workfunction.

[0069] For an alternating copolymer of 9,9-dialkylfluorene-2,7-diyl and N,N- diphenylene(N,N'-substituted-diphenyl)-l,4-phenylenediamine, the I_p values of polymers for the following substitutions on the N-phenyl ring are: p-sec-butyl 5.5 eV, m-trifluoromethyl 6.1 eV, p-trifluoromethyl 6.4 eV. The workfunctions obtained for the corresponding heavily- p-doped polymer with 0.8 holes per repeat unit is 5.5 eV, 5.8 eV and 6.0 eV respectively, using tetrakis(l,3,5-trifluoromethylbenzene)borate as model counter-anion.

[0070] Thus, numerous combinations of structures are available to generate the triarylamine material with the desired I_p, through the choice of the structure of the

triarylamine moiety, its substituents, and the copolymer unit, if any. [0071] While the workfunction of the doped material depends on I_p of the undoped precursor material, it depends in addition on the doping level, the counter-anion and any spectator cation present. In the regime of weak doping, for example less than about 0.2 holes per amine repeat unit, the workfunction of the p-doped material increases greatly with doping level. However in the regime of strong doping, for example from about 0.2 holes to about 1 hole per amine repeat unit, it increases only slightly with doping level.

[0072] The term "about" as used herein with respect to doping level refers to ± 50 %.

[0073] Therefore, without being thereby limited by theory, the trend in the workfunction of a heavily-p-doped polymer can be controlled through the energy of the singly occupied molecular orbital that is influenced by the I_p of the polymer, although it is additionally influenced by counter-anion, and spectator cation if any.

[0074] Numerous combinations of the ττ-conjugation structures and their modifications can be obtained by following the rules outlined here to achieve the required I_p that can result in high workfunction p-doped materials.

[0075] Measurement ofI_p and workfunction: The I_p can be measured by ultraviolet photoemission spectroscopy following standard procedures of measuring the kinetic energies at the Fermi level and the low-energy cutoff of the sample to determine the vacuum level, and then extrapolating the photoemission onset to define the I_p, as described for example in: Hwang J.H., Wan A., Kahn A. Mater. Sci. Eng. R 64 (2009) pp.1. All ionization potentials and workfunctions in this document were measured this way. Other ways to measure I_p includes cyclic voltammetry, which may be complicated by counter-ion effects, and an ambient photoemission technique often called AC2.

[0076] Measurement of electrical conductivity: The electrical conductivity can be measured by standard four-probe force-sense measurements. The suitability of the doping level used in the HIL/ HEL can be directly assessed in the device configuration by capacitance-voltage measurements as a function of dc bias and frequency. The capacitance is preferably constant up to 10 MHz and substantially independent of bias between -3 and +3 V.

[0077] Determination of ohmicity of contact: The extent to which an ohmic hole contact is achieved can be evaluated from the current-voltage characteristics of a set of hole-only diodes fabricated with the HIL/ HEL, and then modelling the characteristics to determine whether the current is space-charge-limited and/or to determine the hole density at the contact. An ohmic contact is one that is substantially ohmic, yielding a current density preferably at least one-third of the expected space-charge-limited current density. Usually such an ohmic contact has a hole density of at least 2x10 11 holes per cm 2. A non-ohmic contact may yield current density less than one-tenth of the expected space-charge-limited current density.

[0078] Cox alentl -Bonded Anion

[0079] The covalently-bonded anion is one or a plurality selected from the group of anions well known in organic chemistry. Examples include sulfonate, fluoroalkylsulfonate, trifluoromethylsulfonylimide, fluoroalkylsulfonylimide, carboxylate, fluoroalkylcarboxylate, and phosphonate, fluoroalkylphosphonates, sulfate, phosphate. The anion is more preferably selected from the group of weakly nucleophilic anions. Examples include sulfonate, fluoroalkylsulfonate, trifluoromethylsulfonylimide, fluoroalkylsulfonylimide,

fluoroalkylcarboxylate, phosphonate, fluoroalkylphosphonates, sulfate, phosphate and a combination thereof.

[0080] Oxidative stability: The anion needs to have good oxidative stability. Oxidative stability is the ability of the said chemical moiety to resist electrochemical oxidation. This can be assessed by the electrode potential for oxidation of the chemical moiety. The anion should not undergo electrochemical oxidation up to an electrode potential of 2 V vs standard hydrogen electrode (SHE). For good oxidative stability, the anion should preferably be hydrophobic to avoid physisorption of water.

[0081] Low nucleophilicity: The anion preferably has low nucleophilicity.

Nucleophilicity is the tendency of the said chemical moiety to take part in nucleophilic (i.e., formal electron pair donation) reactions. This can be inferred from the rate of nucleophilic reactions on model targets, such as Malachite, tropylium, benzhydrylium or other aromatic carbocations. See for example: March's Advanced Organic Chemistry: Reactions,

Mechanisms and Structures, Wiley. The anions preferably are of similar or lower

nucleophilicity as compared to sulfonate or phosphonate.

[0082] Nucleophilicity can also be inferred from the negative logarithm of the

dissociation constant, the so-called pKa, of the corresponding acid of the anion in a suitable non-protic solvent. See for example: March's Advanced Organic Chemistry: Reactions, Mechanisms and Structures, Wiley. The anions preferably are derived from acids with similar or more negative pKa values less than -1 in 1,2-dichloroethane. [0083] In view of the above, a suitable anion is a sulfonate covalently bonded to a polymer or through a (Ci-C₈)-alkyl or (Ci-C₈)-perfluoroalkyl chain, a phosphonate bonded to a polymer or through a (Ci-C₈)-alkyl or (Ci-C₈)-perfluoroalkyl chain, or a carboxylate bonded to a polymer through a (Ci-C₈)-perfluoroalkyl chain.

[0084] Anion attachment: The anion is covalently attached to a material directly or through a short spacer chain, such as an alkyl chain, i.e., -(CH₂)_X- where x is 1-8, preferably 2-4; a perfluoroalkyl chain, e.g., -(CF₂)_X- where x is 1-8, preferably 2-4; an alkoxy chain - (OCH₂CH₂)_x-, where x is 1-3, preferably 1-2; or a perfluoro alkoxy chain -(OCF₂CF₂)_x-, where x is 1-3, preferably 1-2. The material may be the one that contains the triarylamine moiety, or a separate polymer provided by the purpose of attaching the anion. Examples of such a polymer include vinyl polymers, such as polystyrenesulfonate.

[0085] The optimum spacer length is best determined empirically because this varies with the exact structure of the material. Without thereby being limited by theory, the

processability of the material whether in the undoped precursor form or p-doped form is affected by competition between hydrophobicity of the π—conjugated core and side chains and the ionic character of counter-anion together with the hole and spectator ion, if any. These side chains can be, for example, alkyl, perfluoroalkyl or alkoxyl; or optionally substituted alkyl, perfluoroalkyl or alkoxyl, wherein the substituent is a polar group such as alkoxy, phenoxy, cyano, alkylketo, alkoxycarbonyl, or alkoxycarbonyloxy.

[0086] Anion density: The ratio of anion equivalent to triarylaminium moiety f should preferably be 1-5, and more preferably 1-3. A singly charged anion is counted as one equivalent. This f ratio determines the fractional excess of anions in the material which requires spectator cations to counter-balance. The fractional spectator cation required is given by f - 1. If f = 1, the number of anions is just sufficient to self-compensate for the number of holes on the material. The fully self-compensated p-doped material exists in the zwitterionic form where the positive and bound negative charges are exactly in balance. In this case, the holes are fully charge-balanced by the covalently-bonded anions. If f < 1, the p- doped material is not fully self -compensated. This means that free anions need to be present. The holes in the self-compensated p-doped material cannot significantly diffuse or migrate through the material. This is because all the counter-anions are immobilized. There are no other excess anions that can diffuse or migrate together with the holes. Without hereby being limited by theory, this is key to achieving a stable doping level that does not degrade during processing, storage or device operation.

[0087] It may be desirable if a graded doping profile is accomplished in the HIL through the sequential deposition of materials with a progressively changing doping level.

[0088] If f > 1, the number of anion equivalent is larger than the number of aminium units. Hence the fraction of anions given by f - 1 will need to be compensated by spectator cations. In this case, the spectator ions can advantageously be employed to impart solvent processability to the undoped precursor material. This may be beneficial for solution- state doping. The spectator ions may further impart solvent processability to the fully- or heavily- p-doped polymer, depending on its choice.

[0089] Pre- versus post-functionaliz tion: The desired anionic groups can be provided on the polymer by pre- or post-functionalization, depending on ease of synthesis and purification, and the characteristics of the resultant materials. The anion group can be incorporated into the monomer which is then polymerized. Alternatively it can be functionalized into the polymer post-polymerization using a suitable chemistry.

[0090] Spectator Cations

[0091] The one or a plurality of spectator cations may preferably be selected from the group of cations. Examples of cations include Li⁺, Na⁺, K⁺, Cs⁺; ammonium and substituted ammonium R₄N⁺ where R is preferably C1-C12 alkyl or phenyl, including N,N- dimethylmorpholinium; sulfonium R₃S⁺ where R is C1-C12 alkyl or phenyl; phosphonium R tP^"1" where R is preferably C1-C12 alkyl or phenyl; aromatic heterocycle cations including pyridinium, imidazolium, pyrrolium, pyrylium, including their substituted analogues. Useful examples of imidazolium include N-butyl-N-methylimidazolium (often denoted bmim), N- hexyl-N-methylimidazolium (hmim) and N-octyl-N-methylimidazolium (omim).

[0092] Choice of cation: Without thereby being limited by theory, the spectator cation can be chosen to help solubilize the p-doped polymer in the desired processing solvent. The nature and number density of these cations modify the morphology and coulombic interactions within the ionic clusters comprising counter-anions, holes and spectator cations in the p-doped material. Through interactions with the solvent, the spectator cation can provide enthalpic and entropic contributions to solvation energetics, and hence a degree-of- freedom to improve solubility of the material. [0093] It has been determined for example for a model alternating copolymer of 9,9- dialkylfluorene-2,7-diyl and N,N-diphenyl(N-(m-trifluoromethyl)phenyl)amine-4,4'-diyl that small spherical cations with ionic radii smaller than about 1.7 A, as exemplified by Li⁺, Na⁺ and Cs⁺, tend to confer solubility in protic solvents such as methanol. Large spherical cations with ionic radii larger than about 3.2 A, as exemplified by tetramethylammonium, tetraphenylphosphonium, tend to confer solubility also in aprotic polar solvents such as propylene carbonate and Ν,Ν-dimethylacetamide. Non-spherical cations such as

imidazolium tend to introduce a richer solubilization behavior owing to the presence of a solubilizing alkyl side chain on the cation.

[0094] Further than above, the appropriate cation or cations for the given material structure and solvent needs to be determined empirically.

[0095] Insertion of spectator cations: The material as synthesized typically have the covalently-bonded anions counterbalanced by H⁺, Na⁺ or K⁺ in the undoped precursor material, depending on the chemical process used. Several ways are available to exchange the desired spectator cation or cations into the material before p-doping. These include: (i) dialysis, (ii) ion-exchange resin, or (iii) metathesis.

[0096] In the dialysis method, the material is dissolved in a suitable solvent and kept on one side of a suitable dialysis membrane. A suitable salt of the target cation or cations is dissolved into a suitable solvent and placed either on the same side or opposite side of the membrane. The membrane may be made, for example, of cellulose or polyethersulfone. As dialysis proceeds, the dialysate is refreshed and gradually replaced with pure solvent. In this way, ion exchange takes place and excess ions are removed from the material. The material may be purified by dialysis until the desired ionic purity is obtained, for example sub-1% ionic impurities.

[0097] In the ion-exchange resin method, the desired cation is first inserted in the usual way into a suitable ion-exchange resin, which is then placed in contact with the material in solution for the ion exchange to take place.

[0098] In the metathesis method, the material is mixed with a suitable salt of the target cation to precipitate an insoluble salt. One way to accomplish this is to prepare the Ag⁺ salt of the material, react this with a suitable halide salt of the target cation, such as a bromide or an iodide, and then remove the silver halide formed by filtration or centrifugation.

[0099] Polymer Diluents [00100] The one or a plurality of polymer diluents may preferably be selected from the group of polymers that can have favorable interaction with the p-doped material, subject to the requirements of oxidative stability and low nucleophilicity. Examples of such polymers include polyelectrolytes, such as poly(styrenesulfonate salts).

[00101] p-Doping and Excess Ion Removal

[00102] As a consequence of the high I_p of the triarylamine material, p-doping has to be accomplished using a p-dopant that has a much higher reduction potential than a proton or acid. The formal reduction potential E° of an oxidant measures the thermodynamic ability of the oxidant to transfer holes to oxidize another material. A dopant that has a higher E° value is a stronger dopant. The E value of a proton in aqueous solution is 0.0 V vs SHE.

[00103] p-Dopant: A suitable p-dopant is selected from the group of electron-transfer oxidants, more preferably from the group of one-electron oxidants. Examples of one-electron dopants include (indicative E° values in bracket): tris(p-nitrophenyl) aminium salts (1.84 V), tris(2,4-dibromophenyl)aminium salts (1.78 V), tris(p-cyanophenyl)aminium (1.72 V), nitronium salts (1.6 eV), thianthrenium salts (1.49 V), nitrosonium salts (1.42 V), tris(p- bromophenyl) aminium salts (1.34 V), tri(p-methylphenyl) aminium salts (1.04 V) and tris(p- methoxyphenyl) aminium salts (0.80 V).

[00104] Salts: Suitable salts include those of the non-nucleophilic anions, such as hexafluoroantimonate, hexachloroantimonate, perfluoroalkylsulfonate and

bis(trifluoromethylsulfonyl)imide. The anion is selected based on the following

considerations: (i) stability and processability it imparts to the p-dopant, (ii) ease of subsequent purification to give the self-compensated p-doped material, (iii) benignity of residual anion concentration to device performance.

[00105] Advantageously, the p-dopant selected should be one that is just sufficiently strong to p-dope the polymer under the selected conditions of solution- state doping or film- state doping. Nitrosonium and tris(p-bromophenyl)aminium salts are suitable for polymers with Ip in the range of about 5.2 to about 6.5 eV for both solution- state doping and film-state doping.

[00106] Another suitable p-dopant is tetraalkylammonium persulfate.

[00107] Quantification of the doping level: The desired doping level is between about 0.1 hole per repeat unit to about 1.0 hole per repeat unit, more preferably between about 0.4 hole per repeat unit to about 0.8 hole per repeat unit. This can be checked using X-ray photoemission spectroscopy of the Nls core level by quantifying the fraction of photoemission intensity attributed to the p-doped triarylamine moiety (binding energy vs vacuum level, approximately 406.0 eV) compared to the total photoemission intensity including that of the undoped triarylamine moiety (approximately 404.5 eV). Alternatively, this can be checked using UV-Vis spectroscopy by quantifying the fractional loss in the absorption band intensity of the π^~π* band at about 3.0-3.5 eV, and rise in the p-doped band intensities between 0.5-3.0 eV. Alternatively, this can be checked using Hall measurements.

[00108] The doping can be monitored in situ by UV-Vis spectroscopy for both solution- state and film-state doping to adjust the concentration of the p-dopant until the desired doping level is achieved.

[00109] Excess ion removal: After p-doping, purification of the material is required to remove the ionic by-products and obtain the desired self-compensated state. In the case of solution- state doping, purification can be achieved by precipitating the p-doped material using a non-solvent for the material (but which dissolves the ionic by-products) and then re- dissolving the precipitated material in suitable solvent. These steps can be repeated until the material reaches the desired purity. Non-polar or weakly polar solvents such as diethyl ether are suitable for this purpose.

[00110] The purity of the resultant self-compensated p-doped material can be quantified by infrared vibration spectroscopy through the absorption band intensities of the undesired ions.

[00111] In the case of film-state doping, purification can be achieved by immersing the film in a suitable wash solvent.

[00112] Moderately polar solvents such as acetonitrile, and solvent mixtures of a highly polar solvent such as nitromethane, propylene carbonate, and a non-polar solvent such as dioxane are suitable for this purpose.

[00113] Solvents

[00114] Numerous solvents may be considered for the undoped precursor materials.

Without thereby limited by theory, solvents with dielectric constants above 20 may be considered for materials with high anion density. This includes methanol, mixtures of water and methanol, mixtures of water and other lower alcohols, glycol ethers, acetonitrile, N,N- dimethylacetamide, N-methylpyrrolidone, acetonitrile, methoxyacetonitrile, propylene carbonate, ethylene carbonate, nitromethane, dimethylsulfoxide. After doping, fewer solvents are available due to the restrictions on oxidative stability and purity of the solvents. Without thereby limited by theory, solvents with dielectric constants above 20 and oxidative potential above 2.5 V vs SHE may be considered: acetonitrile, methoxyacetonitrile, propylene carbonate, ethylene carbonate, nitromethane. Without thereby limited by theory, solvents with dielectric constants above 20 may be considered for materials with low anion density. The solvent or solvent mixture selected should have the appropriate volatility (boiling point) for the film deposition method chosen.

[00115] Optionally, an acidity modifier may be added to the solvent to regulate the proton activity and/or the conjugate anion activity of the solvent or other electroactive species in the solvent to stabilize the p-doped material in the solvent.

[00116] Films and Devices

[00117] The p-doped materials can be applied as HILs in diodes, including light-emitting diodes and photoconductive diodes, and field-effect transistors.

[00118] In the case of light-emitting diodes, the HIL is fabricated to a thickness of about 5 to about 100 nm, preferably about 30 to about 50 nm, over an anode which may be made, for example, of a metal or a transparent conducting oxide. The HIL may be deposited directly in the doped form or in the undoped precursor form and then doped. Optionally the HIL may be patterned by photolithography or other methods. The light-emitting semiconductor layer or a plurality of light-emitting semiconductor layers may be deposited over the HIL.

[00119] Optionally, one or a plurality of buffer interlayers may be deposited over the HIL before depositing the light-emitting semiconductor layer. The cathode is then deposited, which may be made, for example, of a metal or composite layered structure including LiF. Optionally one or a plurality of buffer interlayers may be deposited over the semiconductor layer before depositing the cathode. The buffer interlayers may perform roles including confinement of opposite carriers, confinement of excitons and assistance to carrier injection. Alternatively, the light-emitting organic semiconductor layer is fabricated in the reverse sequence.

[00120] In the case of field-effect transistors, the HIL is fabricated to a thickness of about 5 to about 100 nm, preferably about 5 to about 20 nm, over an electrode array which may be made, for example, of a metal or a transparent conducting oxide. The HIL is preferably aligned to the electrode array by photolithography or self-organization. The HIL may be deposited directly in the doped form or in the undoped precursor form and then doped. [00121] In the photolithography method, the film may contain photocrosslinkable moieties which are activated by light illuminated through a mask to pattern the film. Alternatively, the film may be patterned by etching or dissolving away areas exposed by a photoresist mask layer that has first been fabricated on the film. In the self-organization method, the HIL is self-aligned to the electrode array by chemical interactions. This process, also called self- assembly, typically limits the HIL thickness to 1-5 nm.

[00122] The semiconductor is then deposited over the HIL, followed by one or a plurality of gate dielectric layers, and a patterned gate electrode. The semiconductor layer may be patterned by photolithography. Alternatively, the field effect transistors may be fabricated in the reverse sequence. In this case, an oxygen-plasma or a reductant may be used to pattern the HIL.

[00123] The p-doped materials can be applied as HELs in photodiodes.

[00124] In the case of photodiodes, the HEL is fabricated to a thickness of about 5 to about 100 nm, preferably about 30 to about 50 nm, over a hole-collecting electrode which may be made, for example, of a metal or a transparent conducting oxide. The HEL may be deposited directly in the doped form or in the undoped precursor form and then doped. Optionally the HIL may be patterned by photolithography or other methods.

[00125] The light-absorbing photoactive semiconductor layer or a plurality of photoactive semiconductor layers may be deposited over the HIL. The electron-collecting electrode is then deposited, which may be made, for example, of a metal or a transparent conducting oxide. Optionally, one or a plurality of buffer interlayers may be deposited over the HEL layer before the photoactive layer. Optionally, one or a plurality of buffer interlayers may be deposited over the photoactive layer before the electron-collecting electrode. The buffer interlayers may perform roles including confinement of opposite carriers and assistance to carrier extraction. Alternatively, the photovoltaic is fabricated in the reverse sequence.

[00126] In the case of tandem photodiodes, a first cell incorporating a HEL is fabricated followed by a second cell incorporating an identical or dissimilar HEL.

[00127] Other devices can be construed, including sensors, super-capacitors, transducers, actuators and electrochromic devices employing the high-workfunction HIL/ HEL, following the general principles above.

[00128] Since the doped material is not in an aqueous solution, the HIL or HEL layer can be advantageously fabricated over other layers without dewetting problems. [00129] EXAMPLES

[00130] A description of example embodiments of the invention follows.

[00131] Examples la through lg

[00132] Examples la through le as outlined below are for synthesis of model polymers from the corresponding monomers to give various copolymers containing N,N-diphenyl(N- phenyl)amine-4,4'-diyl but with different substituents on the pendant N-phenyl ring, different covalently-bonded counter-anion and different spectator cation to illustrate the generality of the concept.

[00133] Example la: Synthesis of an alternating copolymer of N,N-diphenyl(N-(m- trifluoromethyl)phenyl)amine-4,4'-diyl and disodium 9,9-bis(3-sulfonatopropyl)fluorene-2,7- diyl (mTFF- F3S0₃Na) (See Scheme la).

[00134] To a 5-mL microwave-safe vial, equimolar quantities of diBr-F3S03Na (61.2 mg, 0.100 mmol) and diEs-mTFF (56.5 mg, 0.100 mmol) were added. Then Pd(dppf)Cl₂ catalyst (2.25 mg, 3 mol%) was added and the vial was crimp-sealed. The vial was purged pumped down to vacuum and backfilled with argon thrice. A thoroughly degassed 2:1 THF: DMF solvent mixture (2.25 mL) was added into the vial. A thoroughly degassed sodium carbonate solution (1.5 mL, 0.33 M, 0.50 mmol) was added. This resulted in solubilisation of the monomers to give a clear solution. The reactant solution was further degassed (15 min). The reaction vial was loaded into a Biotage microwave synthesizer and rapidly heated to the selected polymerization condition (130°C, 15 min). The polymer was extracted into methanol, concentrated on rotavap, precipitated in acetone and collected on a 2-μιη nylon filter. The polymer was then washed with water until the washing was neutral (pH « 7), redissolved in hot methanol (10 mg /mL), filtered through 2-μπΐ nylon syringe filter, and concentrated on rotavap. The polymer was finally precipitated in toluene and collected on a 2-μπι nylon filter. The product was vigorously agitated in a saturated sodium

diethyldithiocarbamate solution (20 h) to extract Pd catalyst residues. The polymer was recovered by filtration, washed with water and dried overnight under vacuum. The structure of the title polymer was confirmed by 1H NMR and X-ray photoemission spectroscopy.

[00135] Example lb: Synthesis of an alternating copolymer of N,N-diphenyl(N-(p-sec- butyl)phenyl)amine-4,4'-diyl and disodium 9,9-bis(3-sulfonatopropyl)fluorene-2,7-diyl (TFB-F3S0₃Na) (See Scheme lb). [00136] As in Example la, but with diEs-TFB (55.3 mg, 0.100 mmol) in place of diEs- mTFF. The structure of the title polymer was confirmed by 1H NMR and X-ray

photoemission spectroscopy.

[00137] Example lc: Synthesis of an alternating copolymer of N,N-diphenyl(N-(p-sec- butyl)phenyl)amine-4,4'-diyl and bis(tetramethyammonium) 9,9-bis(3- sulfonatopropyl)fluorene-2,7-diyl (TFB -F3 S O₃TMA) (See Scheme lc).

[00138] As in Example lb, but with diBr-F3S0₃TMA (71.5 mg, 0.100 mmol) in place of diBr-F3S0₃Na, and tetramethylammonium hydroxide solution (1.5 mL, 0.33 M, 0.50 mmol) in place of sodium carbonate solution. The sodium diethyldithiocarbamate step was omitted. The structure of the title polymer was confirmed by 1H NMR and Xray photoemission spectroscopy.

[00139] Example Id: Synthesis of an alternating copolymer of N,N-diphenyl(N-(p- methoxy)phenyl)amine-4,4'-diyl and disodium 9,9-bis(3-sulfonatopropyl)fluorene-2,7-diyl (TFOMe-F3S0₃Na) (See Scheme Id).

[00140] As in Example la, but with diEs-TFOMe (52.7 mg, 0.100 mmol) in place of diEs- mTFF. The structure of the title polymer was confirmed by 1H NMR and X-ray

photoemission spectroscopy.

[00141] Example le: Synthesis of an alternating copolymer of N,N-diphenyl(N- phenyl)amine-4,4'-diyl with different substituents on the pendant N-phenyl ring and disodium 9,9-bis(3-sulfonatotetrafluoroethyl)fluorene-2,7-diyl (TAAx-F2fS0₃Na) (See Scheme le).

[00142] This example outlines an approach to synthesize this alternative covalently- bonded counter-anion for the monomer (diBr-F2fS0₃Na). The rest of the polymerization steps are broadly as given above.

[00143] Sodium 2-Sulfonatotetrafluoroethyl ionic side-chains attached to the fluorene monomer can be synthesized by a 2-step process involving: (1) S 2 Nucleophilic substitution of perfluoro -bromide side chains; (2) sulfinatodehalogenation method which converts the perfluorobromide to a sulfinate salt. This was followed by an oxidation using hydrogen peroxide to give perfluoro- sulfonated fluorene monomer.

[00144] In step (1), KOH is employed as a base to remove the 9-proton on fluorene. 1- bromo-2-iodotetrafluoroethane (2.5 equiv) and DMSO is added dropwise into the reaction mixture, warmed to 50°C for 6 h, cooled to room temperature and then quenched with water, and DCM added to extract the aqueous layer. The extract is then dried and concentrated on a rotary evaporator.

[00145] In step (2), Na₂S₂0₄ (2.2 equiv) is added under Ar to a mixture of bis(l-bromo- tetrafluoroethyl)fluorene (1.0 equiv) in a degassed aqueous ACN (2 H₂0: 1 ACN), and NaHC0₃, and the reaction mixture heated (70°C, 3 h). The two-phase mixture is then extracted with ethyl acetate. The extracts are dried and concentrated on rotavap. The sulfinite salt obtained is then washed with hexane and isopropanol, redissolved in aqueous ACN solution (3 H₂0: 5 ACN) and then reacted with H₂0₂ (22°C, 24 h), whereupon the sulfinite salt is completely oxidised to the sulfonate to give the title diBr-F2S0₃Na monomer. The reaction mixture is then concentrated, washed with hexane and evaporated to yield the monomer, which is then purified by recrystallization.

[00146] Example If: Synthesis of an alternating copolymer comprising one unit of N,N- diphenyl(N-phenyl)amine-4,4'-diyl with alkoxysulfonate side chain and three units of 9,9- bis[2-[2-(2-methoxyethoxy)ethoxy]ethyl]-9H-fluorene-2,7-diyl (TFOC3S0₃Na-3FEG) (See Scheme If).

[00147] To a 20-mL microwave-safe vial, diBr-FEG (61.64 mg, 0.1 mmol,0.5 equiv), diEs-FEG (142.10 mg ,0.2 mmol,1.0 equiv) and diBr-TFOC3S0₃Na (56.32 mg, 0.1 mmol,0.5 equiv) were added. Then Pd(dppf)Cl₂ catalyst (3 mol%) was added and the vial was crimp- sealed. The vial was purged pumped down to vacuum and backfilled with argon thrice. A thoroughly degassed DMF (6 ml) solvent was added into the vial. A thoroughly degassed sodium carbonate solution (3 mL, 0.33 M, 1.0 mmol) was added. This resulted in

solubilisation of the monomers to give a clear solution. The reactant solution was further degassed (15 min). The reaction vial was loaded into a Biotage microwave synthesizer and rapidly heated to the selected polymerization condition (130°C, 15 min). The polymer was precipitated in acetone and collected on a 2-μιη nylon filter. The polymer was then washed with water until the washing was neutral (pH « 7), redissolved in hot DMF (20 mg /mL), filtered through 0.45-μπι nylon syringe filter. The polymer was finally reprecipitated in acetone and collected on a 2-μπι nylon filter. The product was vigorously agitated in a saturated sodium diethyldithiocarbamate solution (20 h) to extract Pd catalyst residues. The polymer was recovered by filtration, washed with water and dried overnight under vacuum. The structure of the title polymer was confirmed by 1H NMR and X-ray photoemission spectroscopy. [00148] Example lg: Synthesis of an alternating copolymer of N,N-diphenyl(N-(m- trifluoromethyl)phenyl)amine-4,4'-diyl and dicesium 9,9-bis(3- trifluoromethanesulfonylimidopropyl)fluorene-2,7-diyl (mTFF-F3TFSICs)(See Scheme lg)

[00149] The conversion to a trifluoromethanesulfonylimide was a three-step process which firstly involved the chlorination of sulfonated polymers e.g. mTFF-F3S0₃Na using oxalyl chloride (10 eq) in THF. The sulfonated polymers were first suspended in THF before addition of chlorinating agent. Addition of oxalyl chloride solubilized the polymer suspension in THF. The reaction mixture is left to stir at room temperature for 12 h in N₂. After removing the excess chlorinating agents by vacuum under N₂ protection,

trifluoromethansulfonamide (10 eq) was dissolved and added to the THF solution. The reaction mixture was again left to stir at room temperature for 12 hours. Upon end of reaction, the polymer was precipitated in MeOH. Finally, the polymer is dissolved in DMSO and converted to the ionic dicesium form by neutralization with cesium acetate. The final mTFF-F3TFSICs polymer is precipitated in THF and recovered by filtration on a 2-μιη nylon filter. The rate of conversion to trifluoromethanesulfonylimide was confirmed by X-ray photoelectron spectroscopy.

[00150] Example 2: Synthesis of post-phosphonated alternating copolymers of N,N- diphenyl(N-(mtrifluoromethyl) phenyl)amine-4,4'-diyl and 9,9-dioctylfluorene-2,7-diyl (P03Na₂-mTFF-F8).

[00151] The alternating copolymer of N,N-diphenyl(N-(m-trifluoromethyl)phenyl)amine- 4,4'-diyl and 9,9-dioctylfluorene-2,7-diyl (40 mg) was dissolved in anhydrous chloroform (20 mL) to give a clear solution (2.0 mg/mL). 1,3,5-trioxane (173^L, 0.385 mmol) was dissolved in anhydrous chloroform to give a clear solution (200 mg/mL) of Chlorotrimethylsilane (146 ^L, 1.15 mmol) and SnCl₄ (45 ^L, 0.385 mmol) were added to the polymer solution at room temperature in N₂ glovebag. The reaction was terminated at 12 h and 24 h to give a degree of substitution per repeat unit of 1.0 and 1.8 respectively. The product was precipitated in a MeOH: H₂0 mixture (10: 1 vol/vol), and collected on centrifuge at 10,000 rev per min (8700 g, 15 min). The centrifugate was redissolved in chloroform (2.0 mL) and precipitated with MeOH. This step was repeated thrice. The chloromethylated polymer was then dried in a dessicator to remove all solvents. 1H NMR confirmed the presence and concentration of the desired -CH₂C1 group. [00152] The chloromethylated polymer (30 mg) was dissolved in mesitylene (6.0 mL) to give a clear solution (5 mg/mL). Triethyl phosphite (1.0 mL, 6.19 mmol) was added, and the mixture heated in an oven (165°C, N2, 16 h), then precipitated in MeOH. The product was recovered by centrifuge at 10,000 rev per min (8700 g, 15 min), then redissolved in chloroform (2.0 mL) and precipitated with MeOH (4.0 mL). This step was repeated thrice, and the product dried. 3 IP NMR confirmed the identity of the product. This product (17 mg) was then dissolved in anhydrous chloroform (2.0 mL) and reacted with bromotrimethylsilane (20 ^L) overnight at room temperature. The product was then hydrolysed with H₂0, dissolved in THF : H₂0 mixture (1: 1 vol/vol) then treated with NaOH stoichiometrically to obtained the title polymers.

[00153] Example 3: Cation exchange of undoped polymer.

[00154] 25 g (59.6mM) of P(Ph)₄Br (Sigma, 218782) was dissolved in 40 mL of MeOH to target a 1.5M solution. The solution was added to 500 mg (0.66 mM) of polymer TFB- F3S0₃Na that was weighted into a vial.

[00155] Cellulose dialysis tubings (Sigma, D0405), cut into strips of 14-16 cm in length, were soaked in a beaker of Millipore water for 30mins. After 30mins, the dialysis tubings were rinsed with Millipore water.

[00156] Each dialysis tubing was filled with approximately 10 mL of solution. The dialysis tubings, 2 in each beaker containing 500 mL of Millipore water and a stirrer bar, was dialyzed for 2 h at a rotation of 80 rev per min. Subsequently, at every 4 h interval, the Millipore water was replaced. This was repeated thrice. At the end of dialysis, the cation exchange process was complete with mTFF-F3S0₃P(Ph)₄ collected as the final product.

[00157] The mTFF-F3S0₃P(Ph)₄ polymer dissolved in MeOH was rotavap to remove the MeOH, leaving behind the solid mTFF-F3S0₃P(Ph)₄. mTFF-F3S0₃P(Ph)₄ was dried completely in a vacuum oven heated to 120°C, and subsequently stored in an inert nitrogen environment.

[00158] X-ray photoemission spectroscopy indicated the P(Ph)₄ cations were satisfactorily exchanged with Na cations to give mTFF-F3S0₃P(Ph)₄.

[00159] Example 4: Solution- state doping and film-state post-doping of different triarylamine polymers to give self-compensated p-doped films. [00160] Examples 4a through 4h as outlined below exemplify the solution- state doping and film-state post-doping of different triarylamine polymers to give self-compensated p- doped films with high workfunctions and illustrate the generality of the concept.

[00161] Example 4a: Film-state post-doping of a layer-by-layer assembled film of the alternating phosphonated and trimethylammonionated copolymers of N,N-diphenyl(N-(p-sec- butyl)phenyl)amine-4,4'-diyl and 9,9- dioctylfluorene-2,7-diyl (P0₃Na₂-mTFF-F8/ NMe₃Br- mTFF-F8) with a nitronium salt.

[00162] The P0₃Na₂-mTFF-F8 product of Example 2a was assembled alternately with the trimethylammonionated derivative made analogously to Example 2a onto ITO-glass treated with a monolayer of poly(styrenesulfonic acid). Each assembled monolayer of the polymer increases the film thickness by 2.0 nm. The polyelectrolyte monolayer (PEM) assembly was then p-doped simply by contact with a p-dopant solution of nitronium hexafluoroantimonate. Solvent was contacted with the p-doped polymer film to remove excess ions.

[00163] Example 4b: Solution- state doping of an alternating copolymer of N,N- diphenyl(N-(mtrifluoromethyl) phenyl)amine-4,4'-diyl and disodium 9,9-bis(3- sulfonatopropyl)fluorene-2,7-diyl (mTFF-F3S0₃Na) with a tris(p-bromophenyl)aminium salt.

[00164] mTFF-F3S0₃Na (75 mg, 98.1 μιηοΐβ) was weighed into a vial and baked on a hotplate (140°C, 30 min) in a nitrogen (N₂)-filled glovebox to completely dry the polymer. Anhydrous nitromethane (10 mL) was added to give a suspension.

[00165] Tris(p-bromophenyl)aminium hexachloroantimonate (420 mg, 514.4 μιηοΐ8, weighed in N₂) was mixed with anhydrous propylene carbonate (10.3 mL) to give a dark-blue solution (50 mM). This p-dopant solution should be freshly prepared before use.

[00166] To the polymer suspension, the p-dopant solution was added gradually (10 mL) whereupon most of the solids have dissolved. The polymer solution turned from clear to brown-blue. The mixture was centrifuged at 3000 rev per min (780 g, 3 min) to collect the supernatant. Anhydrous diethyl ether (60 mL) was added to the supernatant to precipitate the crude self-compensated p-doped polymer. The mixture was centrifuged (3000 rev per min, 780 g, 3 min) and the supernatant discarded. Anhydrous nitromethane (3.6 mL) was added to redissolve the precipitate to give a dark red solution. The solution was filtered through a 5- μιη nylon syringe filter to remove any undissolved solids. The solution could be spun-cast at 2000 rev per min to give deep red films of thicknesses 85-105 nm. This solution could be diluted with anhydrous nitromethane (2.4 mL). The solution could be spun-cast at 2000 rev per min to give deep red films of thicknesses 30-35 nm.

[00167] To complete the purification of the material, anhydrous acetonitrile (80 μΐ. per square cm of film) was contacted with the polymer film (10 s) and spun off at 6000 rev per min. This step was repeated once more.

[00168] UV-Vis spectroscopy indicated a doping density of 0.8 hole per amine unit.

Infrared spectroscopy indicated the hexachloroantimonate impurity was satisfactorily removed. X-ray photoemission spectroscopy indicated the hexachloroantimonate impurity was satisfactorily removed. These results confirmed the self-compensated p-doped state was achieved. Ultraviolet photoemission spectroscopy indicated a workfunction of 5.5 eV.

[00169] Alternately, the procedures could be performed in the ambient.

[00170] Example 4c: Solution-state doping of an alternating copolymer of N,N- diphenyl(N-(p-sec-butyl)phenyl)amine-4,4'-diyl and bis(tetraphenylphosphonium)-9,9-bis(3- sulfonatopropyl)fluorene-2,7-diyl (TFB-F3S0₃P(Ph)₄) with a nitrosonium salt.

[00171] TFB-F3S0₃P(Ph)₄ was dissolved in anhydrous propylene carbonate to give a clear solution (30 mM, by repeat unit). Nitrosonium hexafluoroantimonate was dissolved in anhydrous propylene carbonate to give a dark blue solution (30 mM). The nitrosonium hexafluoroantimonate solution was added gradually to the polymer solution (2.0 equiv) to give a dark red solution. The crude p-doped polymer product was precipitated with anhydrous diethyl ether (3 vol), and recovered on centrifuge at 6,000 rev per min (3100 g, 5 min). The precipitate was then dissolved in y-butyrolactone to give a dark red solution (60 mM, by repeat unit).

[00172] Example 4d: Solution- state doping of an alternating copolymer of N,N- diphenyl(N-(m-trifluoromethyl) phenyl)amine-4,4'-diyl and disodium 9,9-bis(3- sulfonatopropyl)fluorene-2,7-diyl (mTFF-F3S0₃Na)

[00173] mTFF-F3S0₃Na (4.14 mg, 5.4 μπιοΐβ) was weighed into a vial. Anhydrous nitromethane (200 L) was added to give a suspension.

[00174] Nitrosonium hexafluoroantimonate (9.42 mg, 35.4 μπιοΐβ, weighed in N₂) was dissolved with anhydrous nitromethane (1.18 mL) to give a colourless solution (30 mM). This p-dopant solution should be freshly prepared before use.

[00175] To the polymer suspension, the p-dopant solution was added gradually (0.95 mL) whereupon most of the solids have dissolved. The polymer solution turned from clear to red. Anhydrous diethyl ether (3.45 mL) was added to the solution to precipitate the crude self- compensated p-doped polymer. The mixture was centrifuged (6000 rev per min, 3100 g, 3 min) and the supernatant discarded. Anhydrous nitrom ethane (552 μΐ.) was added to redissolve the precipitate to give a dark red solution. The solution could be spun-cast at 2000 rev per min to give deep red films of thicknesses 20-22 nm.

[00176] To complete the purification of the material, anhydrous 1:3 vol/vol

nitromethane: diethyl ether (80 μΐ_^ per square cm of film) was contacted with the polymer film (10 s) and spun off at 6000 rev per min. This step was repeated once more.

[00177] UV-Vis spectroscopy indicated a doping density of 0.8 hole per amine unit.

Infrared spectroscopy indicated the hexachloroantimonate impurity was satisfactorily removed. X-ray photoemission spectroscopy indicated the hexachloroantimonate impurity was satisfactorily removed. These results confirmed the self-compensated p-doped state was achieved. Ultraviolet photoemission spectroscopy indicated a workfunction of 5.7 eV.

[00178] Alternately, the procedures could be performed in the ambient.

[00179] Example 4e: Film-state post-doping of an alternating copolymer of N,N- diphenyl(N-(mtrifluoromethyl) phenyl)amine-4,4'-diyl and disodium 9,9-bis(3- sulfonatopropyl)fluorene-2,7-diyl (mTFF-F3S0₃Na) with a tris(p-bromophenyl)aminium salt.

[00180] mTFF-F3 S 0₃Na polymer ( 13 mg, 17.0 μιηοΐ s) and MeOH (2.0 mL) were mixed to obtain a clear 6.5 mg/ mL solution. This solution was spin-cast at 6,000 rev per min to give a film of thickness 20-25 nm, which was baked on a hotplate (140°C, 15 min) in a nitrogen (N₂)-filled glovebox to remove residual solvent including water.

[00181] Tris(p-bromophenyl)aminium hexachloroantimonate (0.94 mg, weighed in N₂) was mixed with anhydrous nitromethane (190 μL) and anhydrous diethyl ether (580 μL) to give a solution of 1.5 mM of the p-dopant in a 1:3 vol/vol nitromethane : diethyl ether in N₂ glove box. This p-dopant solution should be freshly prepared before use.

[00182] Step 1: Film-state p-doping.

[00183] The p-dopant solution (50 μL per square cm of film) was contacted with the polymer film (30 s) and spun off at 6,000 rev per min, in the N₂ glovebox. The polymer film turned from pale yellow to red.

[00184] Step 2: Excess ion removal.

[00185] Anhydrous acetonitrile (80 μΐ_^ per square cm of film) was contacted with the polymer film (10 s) and spun off at 6000 rev per min, in the N₂ glovebox. This step was repeated once more. UV-Vis spectroscopy indicated a doping density of 0.8 hole per amine unit. Infrared spectroscopy indicated the hexachloroantimonate impurity was satisfactorily removed. X-ray photoemission spectroscopy indicated the hexachloroantimonate impurity was satisfactorily removed. These results confirmed the self-compensated p-doped state was achieved. Ultraviolet photoemission spectroscopy indicated a workfunction of 5.5 eV.

[00186] Alternately, the procedures could be performed in the ambient.

[00187] Example 4f: Film-state post-doping of an alternating copolymer of N,N- diphenyl(N-(m-trifluoromethyl) phenyl)amine-4,4'-diyl and disodium 9,9-bis(3- sulfonatopropyl)fluorene-2,7-diyl (mTFF-F3S0₃Na) mixed with a polymer diluent poly-4- vinylphenol (PVP) and doped with a nitrosonium salt.

[00188] mTFF-F3S0₃Na polymer (2.25 mg) and MeOH ( 1.0 mL) were mixed to obtain a clear 2.25 mg/ mL solution. PVP polymer (6.75 mg) and MeOH (2.0 mL) were mixed to obtain a clear 3.38 mg/ mL solution. Both solutions were mixed together to give a 3mg/ml 1 :3 w/w mTFF-F3S0₃Na:PVP solution in MeOH. This solution was spin-cast at 2,000 rev per min to give a film of thickness 20-25 nm, which was baked on a hotplate (220°C, 15 min) in a nitrogen (N2)-filled glovebox to remove residual solvent including water.

[00189] Nitrosonium hexafluoroantimonate, NOSbF₆, (1.82 mg, weighed in N₂) was mixed with anhydrous acetonitrile (684.8 uL) to give a solution of 10 mM of the p-dopant. IOOUL of 10 mM NOSbF₆ was further diluted with 900uL of acetonitrile to obtain a solution of 1 mM of the p-dopant. This p-dopant solution should be freshly prepared before use.

[00190] Step 1 : Film-state p-doping.

[00191] The 1 mM p-dopant solution (50 μL per square cm of film) was contacted with the polymer film (10 s) and spun off at 2,000 rev per min, in the N₂ glovebox. The polymer film turned from pale yellow to red.

[00192] Step 2: Excess ion removal.

[00193] Anhydrous acetonitrile (80 μΐ_^ per square cm of film) was contacted with the polymer film (10 s) and spun off at 2000 rev per min, in the N₂ glovebox. This step was repeated once more. UV-Vis spectroscopy indicated a doping density of 0.7 hole per amine unit (see FIG 1).

[00194] Example 4g: Film-state post-doping of an alternating copolymer of N,N- diphenyl(N-(mtrifluoromethyl) phenyl)amine-4,4'-diyl and disodium 9,9-bis(3- sulfonatopropyl)fluorene-2,7-diyl (mTFF-F3S0₃Na) with a nitrosonium salt. [00195] mTFF-F3S0₃Na polymer (10 mg, 13.0 μιηοΐβ) and MeOH (2.0 mL) were mixed to obtain a clear 5 mg/ mL solution. This solution was spin-cast at 2,000 rev per min to give a film of thickness 25-30 nm, which was baked on a hotplate (220°C, 15 min) in a nitrogen (N2)-filled glovebox to remove residual solvent including water, followed by film-state p- doping and excess ion removal procedure described above in Example 4f.

[00196] Example 4h: Film-state post-doping of a monolayer of an alternating copolymer of N,N-diphenyl(N-(mtrifluoromethyl) phenyl)amine-4,4'-diyl and disodium 9,9-bis(3- sulfonatopropyl)fluorene-2,7-diyl (mTFF-F3S0₃Na) with a tris(p-bromophenyl)aminium salt.

[00197] mTFF-F3S0₃Na polymer (10 mg, 13.0 μιηοΐβ) and dimethyl sulfoxide (2.0 mL) were mixed to obtain a clear 5 mg/ mL solution. A monolayer of the polymer is self- assembled onto an Au-patterned substrate by contacting the polymer solution (50 μΐ_^ per square cm of substrate) for 1 min before flood-wash with clean DMSO and spun-off at 6000 rev per min. The film was annealed at 220°C (hotplate) for 5 min in glovebox.

[00198] Tris(p-bromophenyl)aminium hexachloroantimonate (0.8 mg, weighed in N₂) was mixed with acetonitrile (980 μί) to give a solution of 1 mM of the p-dopant. This p-dopant solution should be freshly prepared before use.

[00199] Step 1: Film-state p-doping.

[00200] The p-dopant solution (50 μΐ_^ per square cm of film) was contacted with the polymer film (10 s).

[00201] Step 2: Excess ion removal.

[00202] The dopant solution was flood-wash with clean acetonitrile and spun-off at 6000 rev per min.

[00203] Example 5: Improved device performances.

[00204] Examples 5a through 5d as outlined below illustrate the improvements in hole- injection and hole-extraction performance achieved over conventional HILs and HELs.

[00205] Example 5a: Hole injection from ΓΓΌ through the p-doped HIL

[00206] Self-compensated p-doped triarylaminium PEM assembly polymer films made from methods described above in Example 4a were spin-cast on SCI cleaned ITO substrates in N₂ glovebox. Films were heated to 80°C for 5 min in N₂. PEDT:PSSH (1:16) polymer films were spun in air and annealed (140°C, 15 min) in N2 glovebox. Host material (9,9- dioctylfluorene) from toluene was then spin-casted over the /?-doped polymer films. Devices were completed with the evaporation of 120-nm-thick Al as cathode. [00207] The self-compensated p-doped triarylaminium PEM assembly (See FIG. 2) provided more than three orders of magnitude improvement in hole current density injected into 9,9-dioctylfluorene compared to the reference 1: 16 PEDT:PSSH (See FIG. 3).

[00208] Example 5b: Hole injection from ITO through the self-compensated solution- state pre-doped alternating copolymer of N,N-diphenyl(N-(m-trifluoromethyl)phenyl)amine- 4,4'-diyl and disodium 9,9-bis(3- sulfonatopropyl)fluorene-2,7-diyl (mTFF-F3S0₃Na).

[00209] Self-compensated p-doped mTFF-F3S0₃Na polymer films described above in Example 4d were spin-cast on SCI cleaned ITO substrates in N₂ glovebox. PEDT:PSSH (1:6) polymer films were spun in air and annealed (140°C, 15 min) in N₂ glovebox. Host material (9,9-bis(p-octylphenyl)fluorene) from toluene was then spin-casted over the films.

[00210] Devices were completed with the evaporation of 120nm-thick Ag as cathode.

[00211] The reference device with PEDT:PSSH as the HIL gave a turn on voltage at 3.7V and an injection current density of 10-4 Acm-2.The self-compensated p-doped mTFF- F3S0₃Na give more than three orders of magnitude of hole current density higher than the reference PEDT:PSSH (See FIG. 4).

[00212] Example 5c: Hole injection from ITO through the self-compensated film-state post-doped alternating copolymer of N,N-diphenyl(N-(m-trifluoromethyl)phenyl)amine-4,4'- diyl and disodium 9,9-bis(3-sulfonatopropyl)fluorene-2,7-diyl (mTFF-F3S0₃Na).

[00213] Self-compensated p-doped mTFF-F3S0₃Na polymer films described above in Example 4e were spin-cast on 0₂-plasma cleaned ITO substrates in N₂ glovebox.

PEDT:PSSH (1:6) polymer films were spun in air and annealed (140°C, 15 min) in N₂ glovebox. Host material (9,9-bis(p-octylphenyl)fluorene) from toluene was then spin-casted over the films . Devices were completed with the evaporation of 120nm-thick Ag as cathode.

[00214] The self-compensated p-doped mTFF-F3S0₃Na give more than three orders of magnitude of hole current density higher than standard 1:6 PEDT:PSSH (See FIG. 5).

[00215] Example 5d: p-Type top-gate bottom-contact organic field effect transistors.

[00216] 50-nm-thick Au source-drain (s-d) electrodes were deposited through a shadow mask on a glass substrate to provide a channel length of 100 μιη and a channel width of 3 mm. For the prior art device, the substrate was cleaned by UV-ozone. For the device with a monolayer of a self-compensated p-doped HIL, a monolayer of mTFF-F3S0₃Na polymer is self-assembled onto Au s-d described above in Example 4h. 50-nm-thick DPPT2-T films from chlorobenzene solution were spin-cast over the s-d electrodes in the glovebox. The films were annealed at 100°C (hotplate) for 3 min in glovebox. Poly(methyl methacrylate)

(PMMA, Sigma Aldrich; Mw 2M) in butyl acetate was spin-cast over the OSC to give 450- nm-thick gate dielectric. The films were annealed at 90°C (hotplate) for 3 min in glovebox. 50-nm of Ag was evaporated through a shadow mask as the gate electrode (see FIG. 6 for device configuration). The FET with ozone-cleaned Au electrodes exhibits nearly symmetrical gate-voltage (Vgs) thresholds in both directions (p-channel, -20 V; n-channel, +40 V, for channel midpoint voltage of +10 V at Vds = -20 V). When the HIL is inserted, the n-channel characteristics are suppressed by a 10-V upshift of the Vgs threshold and a reduction of the electron current. As a consequence, ambipolar FETs can be differentiated into p- channel FETs (see FIG 7).

[00217] The teachings of all patents, published applications and references cited herein are incorporated by reference in their entirety.

[00218] While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Claims

CLAIMS What is claimed is:

1. A material comprising: a p-doped electrically-conductive polymer or oligomer comprising one or more triarylaminium moieties, and one or more counter-anions covalently bonded to said polymer or oligomer, or to a second polymer or oligomer; wherein the one or more triarylaminium moieties optionally comprises one or more hetero atoms; and wherein the polymer is p-doped to a density of about 0.1 to about 1 hole per triarylamine moiety, and the polymer is capable of forming a layer having a workf unction of from about 5.0 eV to about 6.2 eV.

2. A composition comprising the material of claim 1 and a polymer diluent.

3. The material of claim 1, wherein the triarylaminium moieties form a fully conjugated polymer, a partially conjugated polymer, or pendant groups on a polymer.

4. The material of claim 1, wherein the triarylamine moieties, prior to doping, are

selected from optionally substituted N,N-diphenyl(N-phenyl)amine-4,4'-diyl, optionally substituted 9-phenylcarbazole-3,6-diyl, optionally substituted 9- phenylphenoxazine-3,7-diyl, optionally substituted 10-phenylphenothiazine-5-oxide- 3,7-diyl, optionally substituted N,N'-diphenylene(N,N'-diphenyl)-l,4- phenylenediamine, or optionally substituted N,N'-diphenylene(N,N'-diphenyl)4,4'- diphenylenediamine, wherein substitutions are one or more selected from hydrogen, alkyl, cycloalkyl, phenyl, substituted phenyl, alkoxy, phenoxy, substituted phenoxy, alkylthio, phenylthio, substituted phenylthio, fluorine, cyano, nitro, alkylketo, trichloromethyl or trifluoromethyl.

5. The material of claim 1 or claim 4, wherein one or more co-monomers of the polymer or oligomer comprise fluorene, indenofluorene, phenylene, arylene vinylene, thiophene, azole, quinoxaline, benzothiadiazole, oxadiazole, thiophene, arylamine or bisphenol-A; or optionally substituted fluorene, indenofluorene, phenylene, arylene vinylene, thiophene, azole, quinoxaline, benzothiadiazole, oxadiazole, thiophene, arylamine or bisphenol-A

6. The material of any one of claims 1, 4 and 5, wherein the counter-anions are selected from sulfonate, fluoroalkylsulfonate, trifluoromethylsulfonylimide,

fluoroalkylsulfonylimide, carboxylate, fluoroalkylcarboxylate, phosphonate, fluoroalkylphosphonate, phosphate, sulfate, or a combination thereof.

7. The material of claim 1, further comprising one or more non-covalently attached cations, wherein the cations are selected from Li⁺, Na⁺, K⁺, Cs⁺, NH₄ ⁺, R jN* where R is Ci^~Ci₂ alkyl or phenyl, R₃S⁺ where R is C₁-C₁₂ alkyl or phenyl, R jP* where R is Ci-Ci₂ alkyl or phenyl, or an aromatic heterocycle-containing cation.

8. The material of claim 7, wherein the aromatic heterocycle cations are selected from pyridinium, imidazolium, pyrrolium or pyrylium.

9. The material of claim 1, wherein the polymer or oligomer, prior to doping, is selected from

-39-

-40-

-41 -

where n is at least 5, preferably at least 10; where m is at least 5, preferably at least 10; where M⁺ are non-covalently attached cations.

10. A method of making the material of claim 1, comprising: p-doping a polymer or oligomer with a p-dopant, followed by removing excess ions via a solvent, wherein the p-dopant is a one-electron oxidant with a formal oxidation potential larger than about 0.8 V versus a Standard Hydrogen Electrode.

11. A layer comprising: a p-doped electrically-conductive polymer or oligomer comprising one or more triarylaminium moieties, wherein the polymer or oligomer is in the form of a layer, and one or more counter-anions covalently bonded to said polymer or oligomer, or to a second polymer or oligomer, wherein the workfunction of the layer is from about 5.0 eV to about 6.2 eV.

12. A layer comprising: a p-doped electrically-conductive polymer or oligomer comprising one or more triarylaminium moieties, wherein the polymer or oligomer is in the form of a layer, and one or more counter-anions covalently bonded to said polymer or oligomer, or to a second polymer or oligomer, wherein the layer is capable of hole-injection into or hole-extraction from a semiconductor having an ionization potential of at least about 5.0 eV, and preferably at least about 5.2 eV.

13. The material of claim 1, or the layer of one of claims 11 and 12, wherein the holes are fully self-compensated by the covalently-bonded counter-anions.

14. A method of fabricating the layer of one of claims 11, 12 and 13, comprising: depositing a solution of the p-doped polymer or oligomer, or depositing a solution of the undoped polymer or oligomer followed by p-doping with a p-dopant, and removing excess ions.

15. A device comprising the layer of any one of claims 11, 12 and 13.