TECHNOLOGY FOCUS - POLYMERS - Preparation: No preparation method is given. Preferred Components: The first co-monomer repeat unit comprises an alkylthieno(3,4-c)pyrrole-4,6-dione moiety of formula (I), or 1,3-dithiophene-5-alkylthieno(3,4-c)pyrrole-4,6-dione moiety of formula (II). The second comonomer repeat unit comprises a 4,4'-dialkyl-dithieno(3,2-b:2'3'-d)silole moiety of formula (III), an ethylene moiety, a thiophene moiety, an N-alkylcarbazole moiety of formula (IV), an N-(1-alkyl)dithieno(3,2-b:2',3'-d)pyrrole moiety of formula (V), or a 4,8-dialkyloxybenzo(1,2-b:3,4-b)dithiophene moiety of formula (VI). The photoactive polymer is a substituted poly(3-(7H-3,4-dithia-7-sila-cyclopenta(a)pentalen-2-yl)-thieno(3,4-c)pyrrole-4,6-dione) of formula (VII) (preferably poly(3-(7,7-dihexyl-7H-3,4-dithia-7-sila-cyclopenta(a)pentalen-2-yl)-5-octyl-thieno(3,4-c)pyrrole-4,6-dione)), substituted poly(1-vinyl-thieno(3,4-c)pyrrole-4,6-dione) of formula (VIII) (preferably poly(5-octyl-1-vinyl-thieno(3,4-c)pyrrole-4,6-dione)), substituted poly(1-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione) of formula (IX) (preferably poly(5-octyl-1-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione)), substituted poly(3-(5-(9H-carbazol-2-yl)-thiophen-2-yl)-1-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione) of formula (X) (preferably poly(5-octyl-3-(5-(9-(1-octyl-nonyl)-9H-carbazol-2-yl)-thiophen-2-yl)-1-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione)), substituted poly(3-(5-(7H-3,4-dithia-7-sila-cyclopenta(a)pentalen-2-yl)-thiophen-2-yl)-1-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione) of formula (XI) (preferably poly(3-(5-(7,7-dioctyl-7H-3,4-dithia-7-sila-cyclopenta(a)pentalen-2-yl)-thiophen-2-yl)-5-octyl-1-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione)), substituted poly(3-(5-(4H-dithieno(3,2-b;2',3'-d)pyrrol-2-yl)-thiophen-2-yl)-1-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione) of formula (XII) (preferably poly(5-octyl-3-(5-(4-(1-octyl-nonyl)-4H-dithieno(3,2-b;2',3'-d)pyrrol-2-yl)-thiophen-2-yl)-1-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione)), substituted poly(3-(9H-carbazol-2-yl)-thieno(3,4-c)pyrrole-4,6-dione) of formula (XIII) (preferably poly(5-octyl-3-(9-(1-octyl-nonyl)-9H-carbazol-2-yl)-thieno(3,4-c)pyrrole-4,6-dione)), substituted poly(3-(4H-dithieno(3,2-b;2',3'-d)pyrrol-2-yl)-thieno(3,4-c)pyrrole-4,6-dione) of formula (XIV) (preferably poly(5-octyl-3-(4-(1-octyl-nonyl)-4H-dithieno(3,2-b;2',3'-d)pyrrol-2-yl)-thieno(3,4-c)pyrrole-4,6-dione)), substituted poly(1-(4,8-dihydroxy-benzo(1,2-b;4,5-b')dithiophen-2-yl)-thieno(3,4-c)pyrrole-4,6-dione) of formula (XV) (preferably poly(1-(4,8-bis-octyloxy-benzo(1,2-b;4,5-b')dithiophen-2-yl)-5-octyl-thieno(3,4-c)pyrrole-4,6-dione), poly(1-(4,8-bis-dodecyloxy-benzo(1,2-b;4,5-b')dithiophen-2-yl)-5-octyl-thieno(3,4-c)pyrrole-4,6-dione), poly(1-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-5-octyl-thieno(3,4-c)pyrrole-4,6-dione), poly(1-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-5-dodecyl-thieno(3,4-c)pyrrole-4,6-dione), or poly(1-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-5-(2-ethyl-hexyl)-thieno(3,4-c)pyrrole-4,6-dione)), substituted poly(1-(5-(4,8-dihydroxy-benzo(1,2-b;4,5-b')dithiophen-2-yl)-thiophen-2-yl)-3-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione) of formula (XVI) (preferably poly(1-(5-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-thiophen-2-yl)-5-octyl-3-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione)), or substituted poly(1-(5-(4,8-dihydroxy-benzo(1,2-b;4,5-b')dithiophen-2-yl)-thiophen-2-yl)-3-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione) of formula (XVII) (preferably poly(1-(5-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-thiophen-2-yl)-5-octyl-3-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione), poly(1-(5-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-thiophen-2-yl)-5-(2-ethyl-hexyl)-3-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione), poly(1-(5-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-thiophen-2-yl)-5-dodecyl-3-thiophen-2-yl-thieno(3,4-c)pyrrole-4,6-dione), poly(1-(5-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-3-octyl-thiophen-2-yl)-5-octyl-3-(3-octyl-thiophen-2-yl)-thieno(3,4-c)pyrrole-4,6-dione), poly(1-(5-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-3-ethyl-thiophen-2-yl)-3-(3-ethyl-thiophen-2-yl)-5-octyl-thieno(3,4-c)pyrrole-4,6-dione), poly(1-(5-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-4-octyl-thiophen-2-yl)-5-octyl-3-(4-octyl-thiophen-2-yl)-thieno(3,4-c)pyrrole-4,6-dione), poly(1-(5-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-3-octyl-thiophen-2-yl)-5-dodecyl-3-(3-octyl-thiophen-2-yl)-thieno(3,4-c)pyrrole-4,6-dione) or poly(1-(5-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-4-octyl-thiophen-2-yl)-5-dodecyl-3-(4-octyl-thiophen-2-yl)-thieno(3,4-c)pyrrole-4,6-dione)).R = alkyl;R2, R3 = H or alkyl; andn = 5-1000000. EXAMPLE - A solution of 1,3-dibromo-5-octylthieno(3,4-c)pyrrole-4,6-dione (210.5 mg) and 2,6-bis(trimethyltin)-4,8-dihexylethylbenzo(1,2-b:3,4-b)dithiophene (386 mg) in toluene (20 ml) in a 50 mL flask was flushed with argon for 10 minutes. Tris(dibenzylideneacetone)dipalladium(0) (9.2 mg) and tri(p-tolyl)phosphine (32.72 mg) were subsequently added to the reaction mixture which was subsequently refluxed for 24 hours while under an argon atmosphere. 2-Bromothiophene (0.1 equivalent) was then added to the reaction mixture, the reaction mixture refluxed for an additional 2 hours and 2-tributylstannyl thiophene (0.1 equivalent) was added. The reaction mixture was then refluxed overnight to complete the end-capping reaction. The reaction mixture was subsequently allowed to cool and the polymer precipitated using methanol/water (10:1) (300 ml) and filtered through a 0.45 mu m nylon filter. The polymer was then subjected to Soxhlet extraction using methanol and hexanes. The polymer was taken-up in chloroform, the chloroform solution concentrated and the polymer precipitated using methanol/water (10:1, 400 ml). The precipitate was filtered through a 0.45 mu m nylon filter and the polymer isolated was drying under vacuum at 50 degrees C for 12 hours to give poly(1-(4,8-bis-(2-ethyl-hexyloxy)-benzo(1,2-b;4,5-b')dithiophen-2-yl)-5-octyl-thieno(3,4-c)pyrrole-4,6-dione) (340 mg, 98%).