TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The electron acceptor contains fullerene, fullerene derivative, carbon nanotubes, carbon nanotube derivative, bathocuproine, semiconducting element and/or semiconducting compound, preferably C60 fullerene derivative or C70 fullerene derivative.    TECHNOLOGY FOCUS - POLYMERS - Preparation: No general preparation given. Preferred Composition: The content of unit (I) is more than 0 mol% and 45 mol% or less with respect to total content of copolymer. The copolymer is of formula (V). The copolymer has aryl group or heterocyclic group in terminal. The copolymer further has carbazole and thiophene-containing unit of formula (VI) and fluorene and thiophene-containing unit of formula (VII). The organic layer further includes an electron donor containing copolymer, and an electron acceptor. The weight ratio of copolymer and electron acceptor is 1:0.5-1:4.A=group of formula (i);l,m=more than 0 and 1 or less;l+m=1;andn=1-10000.Preferred Properties: The copolymer has number average molecular weight of 500-1000000 g/mol, and molecular weight distribution of 1-100. EXAMPLE - 4.1 mg 3,6-bis(4',4',5',5'-tetramethyl-1',3',2'-dioxaborolane-2'-yl)-N-9'-heptadecanylcarbazole, 197 mg 2,7-bis(4',4',5',5'-tetramethyl-1',3',2'-dioxaborolane-2-yl)-9,9-dioctylfluorene, 143 mg 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole, 3 ml 20% tetraethylammonium hydroxide aqueous solution, 5 mg tetrakis(triphenylphosphine)palladium(0) and Aliquat 336 (RTM: N-methyl-N,N,N-trioctyloctan-1-ammonium chloride) were added to 3 ml toluene, and stirred for 72 hours under reflux. 0.05 g Phenylboronic acid was added, and reacted for 3 hours. 0.12 g Bromobenzene was added to the reaction mixture, and further reacted for 4 hours. The obtained reaction mixture was cooled to room temperature and poured into methanol. The resultant solid was filtered and extracted by Soxhlet extraction using acetone, hexane and chloroform. The methanol was settled and solid was filtered, to obtain copolymer of formula (Ia) having yield of 61%, number average molecular weight of 11400 g/mol and weight average molecular weight of 42900 g/mol.