TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The conjugated electron-donor structural units B1 are selected from 27 groups as given in the specification e.g. groups of formulae (i)-(x).R1-R4=H, optionally branched 1-37C alkyl or -O-1-16C alkoxy (preferably methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, 2-ethylhexyl, 2-ethyloctyl, 2-ethyldecyl, 2-ethyldodecyl , 4-butylhexyl , 4-butyloctyl, 4-butyldecyl , 4-butyldodecyl , 2-hexyloctyl, 2-hexyldecyl, 4-hexyldecyl , isopropyl, 1-ethylpropyl, 1-butylpentyl, 1-hexylheptyl , 1-octylnonyl, 1-dodecyltridecyl , 1-hexadecylheptadecyl or 1-octadecylnonadecyl).Provided that the R1-R4 are bonded to a carbon atom.    TECHNOLOGY FOCUS - POLYMERS - Preferred Compound: In the pi-conjugated polymer compound, the structure of the repeating base unit is of formula (A1-B1)n, where the ratio between the sum of all the carbon atoms of the alkyl chains present in the repeating base unit and the number of aromatic rings present in the same unit, is 3.5-12. The alternating pi -conjugated polymer is selected from 3 polymer compounds as given in the specification e.g. polymer compound of formula (IA).n=1-1000 (preferably 2-500);andl=3-50.Preparation (Disclosed): 3 Methods for preparation of the alternating pi -conjugated polymer compound are given e.g. reacting 9,9-bis(2-ethylhexyl)-9H-fluorene-2,7-diyldiboronic acid with 1-(2,2-dibromo-vinyl)-4-fluoro-benzene to obtain polymer compound of formula (IA). EXAMPLE - Alternating pi -conjugated polymer poly (9,9-bis (2-ethylhexyl) fluorene-alt-2-(para-fluorophenyl)-1,1-vinylidene) (polymer (IA)) was prepared as follows. The following products were introduced, into a 250 ml three-necked flask equipped with a magnetic stirrer and reflux condenser, in an inert atmosphere: 9,9-bis(2'-ethylhexyl)-2,7-diboronic acid (1.289 mg); para-fluoro- beta , beta -dibromostyrene (1,1-dibromo-2-(para-fluorophenyl) ethylene) (755 mg), dissolved in deaerated toluene (20 ml); Aliquat 336 (250 mg) dissolved in deaerated toluene (50 ml); potassium carbonate (12 ml), 1.036 M (deaerated water) (12.4 mmoles); and palladium (0) tetrakis (triphenylphosphine) (66 mg). The reaction mixture was heated to reflux temperature (90 degrees C) and under vigorous stirring for 26 hours. At the end of the period indicated, the mixture was concentrated to 30 ml and poured into methanol (400 ml). The precipitate obtained was filtered and washed, in order, with methanol, water and methanol again. The product was dissolved in a minimum quantity of toluene and re-precipitated in methanol. Yellow-greenish polymer (650 mg) of formula (IA) was obtained. The optical band-gap measured on the solid film for the copolymer thus obtained was 2.5 eV, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) values of -5.7 and -2.2 eV, respectively, a weight average molecular weight of 6400 and a weight loss at 250 degrees C of less than 1%, determined by means of thermogravimetric analysis in air.