TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Cell: In the cell, one of the anode or the cathode comprises one of indium tin oxide (ITO), indium-doped zinc oxide (IZO), tin oxide (SnO2), aluminum-doped zinc oxide (AZO), and/or gallium-doped zinc oxide (GZO); and the other of the anode and the cathode comprises at least one of aluminum (Al), silver (Ag), gold (Au), and/or lithium (Li). Preferred Components: The photoactive layer includes an electron acceptor material. The electron acceptor material comprises one of cadmium sulfide (CdS), CdTe, CdSe, and/or zinc oxide (ZnO).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred components: The electron acceptor material comprises one of C60, C70, C74, C76, C78, C82, C84, C720, C860, 1-(3-methoxy-carbonyl)propyl-1-phenyl(6,6)C61 (C61-PCBM), C71-PCBM, C84-PCBM, bis-PCBM and/or perylene.    TECHNOLOGY FOCUS - POLYMERS - Preparation: No general method for preparation of the polymer compound (P1) is given. Preferred Compound: In the electron-donating polymer (P1), the repeating unit A includes 6 repeating units, as given in the specification, e.g. polymer compound of formula (IV); and the repeating unit B includes 6 repeating units, as given in the specification, e.g. polymer compound of formula (V). The electron-donating polymer (P1) includes the repeating units A and B in a mole ratio of 1:1 to 1:1.4 or 1:1.001 to 1:1.2. The electron-donating polymer has a number average molecular weight of 1000-800000; and has a band gap of 1.2-2.5 eV. The electron-donating polymer (P1) comprises 18 repeating units, as given in the specification, e.g. polymer compounds of formulae (VI) and (VII). Preferred Components: The substrate comprises glass, polycarbonate, polymethylmethacrylate, polyethylene terephthalate, polyethylene naphthalate, polyamide or polyethersulfone. EXAMPLE - Bis(trimethyl tin)-1,8-bis(ethyloxy)anthro(1,2-b:4,5-b')dithiophene (0.02 mol) and ethyloxy-6-dibromo-thieno(3,3-b)thiophene (0.02 mol) were added to 5 ml of dimethylformamide (DMF)/toluene (dimethylformamide/toluene) (having volume ratio of 1:4), and then tetra(triphenylphosphine)palladium (Pd(PPh3)4) as a catalyst was added. The mixture was agitated at 120 degrees C for 6 hours to obtain electron-donating polymer having number average molecular weight of 18000.