TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The terminal group is a monocyclic aromatic compound group having a substituent. The substituent contained in the aromatic group is chosen from silyl group, amino group, alkyl group, alkenyl group, alkynyl group, alkoxy group, alkyl carbonyl group, and alkoxy carbonyl group. The copolymer preferably has a repeating unit of formula (V).    TECHNOLOGY FOCUS - POLYMERS - Preparation (disclosed): The copolymer is prepared by polymerizing carbonyl group-containing compound of formula (III) and tricyclic compound of formula (IV) in the presence of a catalyst.X,Y=halogen atom, alkyl stannyl, alkyl sulfo, aryl sulfo, arylalkyl sulfo, borate residue, sulfonium methyl, phosphonium methyl, phosphonate methyl, mono-halogenated methyl, boric acid residue, formyl, silyl, alkenyl, or alkynyl. EXAMPLE - 175.7 mg Imide thiophene dibromide was added into a two-opening round bottom flask as monomer, under nitrogen atmosphere. 328.8 mg 4,4-Bis(2-ethylhexyl)-2,6-bis(trimethyltin)-dithieno-2',3'-silole was further added into the flask, to obtain a mixture. 15 mg Tetrakis(triphenylphosphine)palladium, 19 mg triphenylphosphine-containing heterogeneous-system palladium complex catalyst, 7.4 mL toluene, and 1.8 mL N,N-dimethylformamide were added to the mixture contained in the flask, and stirred continuously at 90-100 degrees C for 1-10 hours. The reaction mixture was diluted with toluene for 4 times, and stirred at 100 degrees C for 0.5 hour. 0.3 mL Trimethyl(butyl-phenyl)tin and 1.5 mL 1-bromo-4-butylbenzene were added to the reaction liquid as terminal treatment material, and stirred at 100 degrees C for 10 hours. The reacted liquid was poured into methanol, and precipitated and filtrated, to separate solids. The separated solids were dissolved in chloroform. A diamine silica gel was added into the chloroform, and stirred at room temperature for 1 hour, to prepare a mixed solution. The mixed solution was concentrated, and recrystallized using chloroform or ethyl acetate as solvent, to obtain the copolymer, having weight average molecular weight of 1.89x 105 and polydispersity index of 3.5.