NOVELTY - Copolymer comprising (a) at least one dithiophene unit (I), (b) at least one thia-aromatic unit (II), and (c) at least one thia-aromatic unit (III), is new.    USE - The copolymer or the substance mixture is useful as an absorber of an organic photovoltaic module, and as a semiconducting component of a field-effect transistor or a diode (claimed).    ADVANTAGE - The copolymer exhibits high charge carrier mobility, improved absorption behavior which is matched to solar spectrum, and very good solubility in organic solvents.    DETAILED DESCRIPTION - Copolymer comprising (a) at least one dithiophene unit of formula (-A-) (I), (b) at least one thia-aromatic unit of formula (-B1-) (II), and (c) at least one thia-aromatic unit of formula (-C1-) (III), is new.    A = cyclopenta-dithiophene moieties of formula (Ia) or (Ib) or benzodithiophene moieties of formula (Ic) or (Id);    B1 = heteroaryl moieties of formula (IIa);    C1 = heteroaryl moieties of formula (IIIa);    R1 = H, 1-36C alkyl, 5-36C cycloalkyl, 1-36C alkoxy, 6-10C aromatic group, 6-36C aryloxy, 6-36C arylthio-oxy or 4-36C heteroaromatic group;    R2 = H, F, 1-36C alkyl, 5-36C cycloalkyl, 1-36C alkoxy, 6-10C aromatic group, 6-36C aryloxy, 6-36C arylthio-oxy or 4-36C heteroaromatic group;    R3 = H, 1-36C alkyl, 5-36C cycloalkyl, 1-36C alkoxy, 1-36C alkylthio-oxy, oligo(alkylene glycol)oxy, poly(alkylene glycol)oxy, 6-10C aromatic group, 6-36C aryloxy, 6-36C arylthio-oxy or 4-36C heteroaromatic group; either    R4 = H, halo, 1-36C alkyl, 5-36C cycloalkyl, 1-36C alkoxy, 6-10C aromatic group, 6-36C aryloxy, 6-36C arylthio-oxy or 4-36C heteroaromatic group; or    2 vicinal R4 = (hetero)aromatic ring; and    X = N or P.    INDEPENDENT CLAIMS are also included for:    (1) preparing the copolymer;    (2) a substance mixture comprising the above copolymer and at least one fullerene with 60 carbon atoms, fullerene with 70 carbon atoms and/or a fullerene derivative, preferably phenyl-C61-butyric acid methyl ester and/or phenyl-C71-butyric acid methyl ester, where the weight ratio of the copolymer and fullerene with 60 carbon atoms, fullerene with 70 carbon atoms and/or a fullerene derivative is 10:90-80:20, preferably 20:80-70:30;    (3) an electrical- or electronic component comprising a semiconductor which comprises the above copolymer or the substance mixture; and    (4) manufacturing the electrical- or electronic component, comprising depositing the copolymer or the substance mixture from a solution by spin coating, dip coating, doctor blade coating or printing method, preferably ink jet coating or slot die coating, and removing the solvent, and (b) vapor-depositing or printing the first- and/or the second electrode or depositing the first- and/or the second electrode from precursor compounds of the electrode material.