TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The electron-donor structural units (ii) are units of the thiophene, fluorine, phenothiazine, pyrrole, carbazole type, possibly also condensed and optionally substituted with alkyl groups. The conjugated electron-donor structural unit (B') is selected from compound of formula 2,6-dimethyl-3H-1lambdaasterisk4asterisk-dithieno(3,2-b;2',3'-d)thiophene, 2,5-dimethyl-thieno(3,2-b)thiophene, 1,3-dimethyl-benzo(c)thiophene, 2,5-dimethyl-thiazole, compound of formulae (ia)-(ig), (iia)-(iie) or 1,2-vinylene group.Y'=at least one group selected from alkyl, alkoxy, alkylamino or alkylthio;X=R, Ar-Y';X'=O or S;R'a=alkyl (preferably branched, containing 1-36, especially 4-16C), or aryl groups (preferably phenyl substituted with 1-24 (preferably 4-18C) alkyl radicals (preferably heptyl, octyl, dodecyl, hexadecyl, 2-ethylhexyl, 2-ethyloctyl, 2-ethyldodecyl, 2-ethyl-hexadecyl, 2-butylhexyl, 2-butyldodecyl, 1-hexylhexyl, 1-octyloctyl, 1-dodecyldodecyl, 1-hexadecylhexadecyl, 1-octadecyloctadecyl, 1,1,3,3-tetramethylbutyl, 2,2-di-isopropylphenyl).    TECHNOLOGY FOCUS - POLYMERS - Preparation: No general preparation is given for the compound (I). Preferred Components: The average number of (A) units in the copolymer is 2-1000 (preferably 5-1000). Each non-terminal (A) unit in the polymeric chain is bound to two (B') units, the same or different, in any two of the positions 2, 3, 6 and 7 of (i), preferably in positions 2.6 or 2.7. The structure of the repetitive base unit is represented by one of the formulae (A-B')n', (B'-A-B')n'or (B'-B1-A-B1)n'. The ratio between the sum of all the carbon atoms of the alkyl chains present in the repetitive base units and the number of aromatic rings present in the same unit varies from 3.5-12.B'and B1=B-type conjugated subunits;n'=2-1000 (preferably 5-1000).Preferred Copolymer: The copolymer (I) is preferably selected from compound of formula (Ia)-(Id).n=2-500. Preferred Definitions:    R1 and R2=C7H15 or C8H17 alkyl group;    R3-R7=H;    R7=Br.    EXAMPLE - No suitable example is given.