NOVELTY - Copolymer (A) comprising (hetero)arylene repeating units is claimed, where the copolymer is optionally doped with one or more polymeric acids.    USE - (A) is useful in an electrically conductive layer or film, which is useful in an article comprising light-emitting diodes, light emitting diode displays, liquid crystal displays, electronic paper, touchscreens, diode lasers, photodetectors, photoconductive cells, photoresistors, photo switches, phototransistors, phototubes, infrared detectors, photovoltaic devices, solar cells, transistors, diodes, memory storage devices, antistatic films biosensors, electrochromic devices, solid electrolyte capacitors, energy storage devices, electromagnetic wave shielding films, window de-icers, heat reflectors and architectural materials (all claimed). (A) is useful: as an electrode or an electrode buffer layer in an electronic device; as an electrode material for a gate and a source-drain electrode in an organic transistor; and to form buffer layers in an electronic device.    ADVANTAGE - (A) have improved photocrosslinkable and soluble properties.    DETAILED DESCRIPTION - Copolymer (A) comprising (hetero)arylene repeating units of formula (-A-) (I) and (-B1(R1)-) (II) is claimed, where the copolymer is optionally doped with one or more polymeric acids.    A, B1 = phenylene, phenylene vinylene, pyrrolylene, pyrrolylene vinylene, thienylene, thienylene vinylene, fluorenylene, fluorenylene vinylene, furanylene, furanylene vinylene, phenothiazinylene, phenothiazinylene vinylene, phenazinylene, phenazinylene vinylene, phenoxazinylene or phenoxazinylene vinylene (all optionally substituted with one or more groups comprising hydroxyl, alkyl, alkenyl, alkynyl, alkanoyl, alkanoylamino, alkenoyl, alkynoyl, alkoxy, alkoxycarbonyl, alkoxycarbonylamino, alkylamino, alkylaminocarbonyl, dialkylaminocarbonyl, alkylsulfonyl, alkylsulfinyl, sulfonylaminoalkyl, alkylsulfonylaminocarbonyl, aminoalkyl, cyanoalkyl, halo, haloalkyl, haloalkenyl, haloalkynyl, haloalkanoyl, haloalkenoyl, haloalkynoyl, haloalkoxy, haloalkoxycarbonyl, hydroxyalkyl, oxoalkyl, cycloalkyl, cycloalkenyl, cycloalkanoyl, cycloalkenoyl, cycloalkoxy, cycloalkoxycarbonyl, aryl, arylene, heterocycle, heterocyclyl, heteroaryl, heteroarylene, arylalkyl, heteroarylalkyl, arylalkanoyl, heteroarylalkanoyl, arylalkenoyl, heteroarylalkenoyl, arylalkynoyl, heteroarylalkynoyl, arylalkoxy, heteroarylalkoxy, aryloxy, heteroaryloxy, aryloxycarbonyl, heteroarylxoycarbonyl, arylalkoxycarbonyl, heteroarylalkoxycarbonyl, alkylthio, alkylthioalkyl, arylthio, arylsulfonyl or arylsulfinyl, or the substituents together form an alkylene or alkenylene chain completing a 3-7-membered aryl or alicyclic ring optionally including one or more divalent N, S or O atoms), where the substituents are optionally substituted;    R = Y1 or L-Y1;    Y1 = photoreactive group; and    L = linker.    INDEPENDENT CLAIMS are included for:    (1) a composition comprising the copolymer (A);    (2) an electrically conductive layer or film formed from the composition;    (3) preparing an electrically conductive layer or film comprising applying the composition on a substrate, and exposing the substrate to UV light, thus inducing a photocrosslinking reaction of the composition; and    (4) an article comprising at least one electrically conductive layer formed from the composition.