TECHNOLOGY FOCUS - POLYMERS - Preparation (Disclosed): Preparation of (I) comprises reacting (II) with stannane derivative of formula ((R3)3Sn-Ar1-Sn(R3)3) in the presence of palladium(0) complex (e.g. palladium tetrakis(triphenylphosphine)) in an organic solvent or its mixture e.g. toluene and dimethylformamide.R3 = alkyl (e.g. methyl ethyl, propyl and butyl).Preferred Components: (I) is an electron donor and the film or membrane further comprises an electron accepting compound. The electron accepting compound comprises a fullerene. The fullerene comprises (6,6)-phenyl-C71-butyric acid methyl ester. (I) is poly(3-(5-(7,7-bis-(2-ethyl-hexyl)-7H-3,4-dithia-7-sila-cyclopenta(a)pentalen-2-yl)-4-(2-ethyl-hexyl)-thiophen-2-yl)-6-(4-(2-ethyl-hexyl)-thiophen-2-yl)-(1,2,4,5)tetrazine), poly(3-(5-(7,7-dihexyl-7H-3,4-dithia-7-sila-cyclopenta(a)pentalen-2-yl)-4-(2-ethyl-hexyl)-thiophen-2-yl)-6-(4-(2-ethyl-hexyl)-thiophen-2-yl)-(1,2,4,5)tetrazine), poly(3-(5-(4,4-bis-(2-ethyl-hexyl)-4H-cyclopenta(2,1-b;3,4-b')dithiophen-2-yl)-4-(2-ethyl-hexyl)-thiophen-2-yl)-6-(4-(2-ethyl-hexyl)-thiophen-2-yl)-(1,2,4,5)tetrazine), poly(3-(5-(4,4-dihexyl-4H-cyclopenta(2,1-b;3,4-b')dithiophen-2-yl)-4-(2-ethyl-hexyl)-thiophen-2-yl)-6-(4-(2-ethyl-hexyl)-thiophen-2-yl)-(1,2,4,5)tetrazine), poly(3-(5-(4,4-bis-(2-ethyl-hexyl)-4H-cyclopenta(2,1-b;3,4-b')dithiophen-2-yl)-4-hexyl-thiophen-2-yl)-6-(4-hexyl-thiophen-2-yl)-(1,2,4,5)tetrazine), poly(3-(5-(4,4-dihexyl-4H-cyclopenta(2,1-b;3,4-b')dithiophen-2-yl)-4-hexyl-thiophen-2-yl)-6-(4-hexyl-thiophen-2-yl)-(1,2,4,5)tetrazine), poly(3-(5-(4,4-bis-(2-ethyl-hexyl)-4H-cyclopenta(2,1-b;3,4-b')dithiophen-2-yl)-3-hexyl-thiophen-2-yl)-6-(3-hexyl-thiophen-2-yl)-(1,2,4,5)tetrazine) or poly(3-(5-(4,4-dihexyl-4H-cyclopenta(2,1-b;3,4-b')dithiophen-2-yl)-3-hexyl-thiophen-2-yl)-6-(3-hexyl-thiophen-2-yl)-(1,2,4,5)tetrazine). Preferred Process: In the preparation of (II), the oxidation to form (IV) is accomplished with isoamyl nitrite. The reaction of (VI) with hydrazine is assisted with elemental sulfur. Preferred Definitions:    Ar1 = cyclic structure comprising at least one aryl and/or heteroaryl rings comprising 2-50C (containing 1-3 heteroatoms comprising N, O, S or Se, preferably N and/or S, and optionally substituted with at least one of F, CN, OH, oxo, amino, amido, carboxy, NO2, thio, 1-20C alkyl, 2-20C alkenyl, 2-20C alkynyl, 6-20C aryl, 7-24C alkaryl, 1-20C alkoxy, 2-20C alkenyloxy, 2-20C alkynyloxy, 6-20C aryloxy, 1-20C alkylamino, 2-40C dialkylamino, 1-20C alkamido, 2-20C carboxy, 1-20C carbonyl, R2 or OR2), substituted benzo(1,2-b;4,5-b')dithiophenyl moiety of formula (a) or (b), substituted 3H-1lambdaasterisk4asterisk-benzo(2,1-b;3,4-b')dithiophenyl moiety of formula (c) or (d), substituted 3,4-dihydro-1lambdaasterisk4asterisk-cyclopenta(2,1-b;3,4-b')dithiophenyl moiety of formula (e), substituted 1,7-dihydro-3lambdaasterisk4asterisk,4-dithia-7-sila-cyclopenta(a)pentalenyl moiety of formula (f), substituted (2,2')bithiophenyl moiety of formula (g), thieno(3,2-b)thiophenyl moiety of formula (h), benzo(1,2,5)thiadiazolyl moiety of formula (i), substituted 5,6-difluoro-benzo(1,2,5)thiadiazolyl moiety of formula (j), substituted 6,12-dihydro-indeno(1,2-b)fluorenyl moiety of formula (k), substituted 9H-fluorenyl moiety of formula (l) or substituted 6,12-dihydro-6,12-diaza-indeno(1,2-b)fluorenyl moiety of formula (m);    R1, R2 = hexyl or 2-ethylhexyl;    A = S;    x = 1;    X = Br; and    n = 5-10000, preferably 10-2000.    EXAMPLE - 4,4'-Bis(ethylhexyl)-dithieno(3,2-b:2',3'-d)silole (1.17 g) was added into a flask (50 ml) and purged with argon under vacuum. Dry tetrahydrofuran (20 ml) was added into a flask. The solution was cooled down to -78 degrees C using a dry ice-acetone bath. Then 1.6M n-butyl lithium/hexane solution (3.84 ml) was added dropwise. The temperature was then raised and the solution was stirred for 60 minutes. The solution was cooled to -78 degrees C again and 1M trimethyltin chloride/tetrahydrofuran (6.98 ml) was added. Then the cooling bath was removed. After being stirred at ambient temperature overnight, hexane (20 ml) and water (20 ml) was added with stirring, the water layer was separated, the organic layer was washed with water (15 ml) again and the combined water layers were extracted with hexane (20 ml). The combined organic layers were washed with water again and then dried with magnesium sulfate, after removal of volatiles, 4,4'-bis(ethylhexyl)-5,5'-bis(trimethyl-tin)-dithieno(3,2-b:2',3'-d)silole (A) was obtained. To a flask (25 ml), (A) (0.3126 g), 3,6-bis(5-bromo-4-(2-ethylhexyl)thien-2-yl)-s-tetrazine (0.2514 g), N,N-dimethylformamide (0.5 ml) and toluene (8 ml) were added. The system was p urged with argon under vacuum. Palladium tetrakis(triphenylphosphine) (0.06 g) was added in a glove box. The solution was stirred and reflux for 24 hours under the protection of argon. After the solution was cooled down, the solution was dropped into acetone to precipitate the copolymer. The copolymer was Soxhlet extracted with n-hexane and then acetone, and then collected with hot toluene to obtain the copolymer (poly(3-(5-(7,7-bis-(2-ethyl-hexyl)-7H-3,4-dithia-7-sila-cyclopenta(a)pentalen-2-yl)-4-(2-ethyl-hexyl)-thiophen-2-yl)-6-(4-(2-ethyl-hexyl)-thiophen-2-yl)-(1,2,4,5)tetrazine)) (0.32 g, 91%).