TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Component: The cathode is aluminum electrode or double metal layer electrode.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Gas: The protective atmosphere comprises argon gas, nitrogen gas, or argon/nitrogen mixed gas.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compounds: The catalyst is organic palladium, or a mixture of organic palladium and organic phosphine ligand in a molar ratio of 1:4-8. The organic palladium is bis(triphenylphosphine)palladium(II) dichloride or tetrakis(triphenylphosphine)palladium(0). The mixture of organic palladium and organic phosphine ligand is mixture of palladium acetate and tris(o-methoxyphenyl)phosphine, or mixture of tri(dibenzylideneacetone)dipalladium and 2-dicyclohexylphosphino-2',6'-dimethoxy-biphenyl. The organic solvent is toluene, N,N-dimethylformamide and/or tetrahydrofuran.    TECHNOLOGY FOCUS - POLYMERS - Preparation (claimed): In protective-gas atmosphere, a bis-trimethylstannanyl-4H-cyclopenta(2,1-b;3,4-b')dithiophene derivative of formula (II) and 4,7-bis-(5-bromo-thiophen-2-yl)-5,6-difluoro-benzo(1,2,5)thiadiazole in a molar ratio of 1:1-1.2, a catalyst, and an organic solvent are mixed. The mixture is reacted at 70-130 degrees C for 6-60 hours, separated, and purified to obtain copolymer (I). Preferred Conditions: The molar ratio of catalyst and compound (II) is 1:20-1:100. The reaction temperature is 90-120 degrees C and time is 12-48 hours. After reaction completion, the reaction mixture is cooled to room temperature and precipitated with methanol. The precipitate is filtered and extracted by Soxhlet extraction using methanol and n-hexane. The obtained precipitate is extracted with chloroform until colorless, and the chloroform solution is collected and dried to obtain a red powder, which is vacuum-dried to obtain copolymer (I). Preferred Composition: The buffer layer contains a mixture of poly 3,4-ethylenedioxythiophene and polystyrene sulfonic acid.