TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The electron donor includes a p-type semiconductor material, and the electron acceptor includes an n-type semiconductor material.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The electron acceptor is a C60 fullerene, a C70 fullerene, a C74 fullerene, a C76 fullerene, a C78 fullerene, a C82 fullerene, a C84 fullerene, a C720 fullerene, a C860 fullerene, 1-(3-methoxy-carbonyl)propyl-1-phenyl(6,6)C61 (PCBM), C71-PCBM, C84-PCBM, bis-PCBM, perylene, an inorganic semiconductor, and/or their derivatives.    TECHNOLOGY FOCUS - POLYMERS - Preparation: No preparation method is given. Preferred Components: The polymer is an electron donating polymer. (A) is a thieno(3,4-b)thiophene repeating unit of formulae (Aa) or (Ab), and (B) is a thiophene repeating unit of formulae (Ba)-(Bd). (A) and (B) are included in a mole ratio of 1:0.5-1:2.5 (preferably 1:1-1:2). (A) and (B) collectively form a repeating unit C, and the repeating unit C is a (E)-3-(4-methylsulfanyl-(2,2')bithiophenyl-3-yl)-acrylic acid repeating unit of formula (Ca) or (Cb), preferably (Caa), and/or a (E)-3-(4'-methylsulfanyl-(2,2';5',2'')terthiophen-3'-yl)-acrylic acid repeating unit of formula (Cc) or (Cd), preferably (Cbb). The polymer has a number average molecular weight of 500-800000 (preferably 5000-50000) g/mole. The polymer has a band gap of 1.2-2.5 (preferably 1.35-1.6) eV. (A) is an electron accepting unit, and (B) is an electron donating unit.X2 = optionally substituted 1-20C alkyl group, H or halo;X3, X4 = 1-15C alkyl group, 1-15C alkoxy group (both optionally substituted), H, halo or -SR102;R102 = optionally substituted 1-15C alkyl group;X5-X7 = optionally substituted divalent 1-10C aliphatic organic group; andR1, R2 = optionally substituted 1-10C aliphatic organic group or H. EXAMPLE - Bis(tributyltin)thiophene (331 mg) and 5-ethoxy-5-oxopentyl-4,6-dibromothieno(3,4-b)thiophene-2-carboxylate (235 mg) were dissolved in dimethylformamide (10 ml)/toluene mixed in a volume ratio of 1/4, and tetrakis(triphenylphosphine)palladium(0) (25 mg) as a catalyst was added to it. The mixture was agitated. The agitated mixture was heated at 120 degrees C to give an electron-donating polymer (Caa).