TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The catalyst is tetrakis (triphenylphosphine)palladium or bis(triphenylphosphine)palladium dichloride. The molar ratio of catalyst and (A) is 0.0001-0.05:1 and it is mixture of an organic palladium and an organic phosphine ligand with a molar ratio of 1:2-20, where the organic palladium is tris(dibenzylideneacetone) dipalladium and organic phosphine ligand is tri-ortho-tolyl phosphine, the inert gas atmosphere is nitrogen and/or argon, and the solvent is tetrahydrofuran, N,N-dimethylformamide or toluene.    TECHNOLOGY FOCUS - POLYMERS - Preparation (Claimed): Preparation of (I) comprises dissolving stannous compound of formula (A) and 4,7-dibromobenzo(c)(1,2,5)selenadiazole (B1) in a molar ratio of 1.1-1.5:1 into organic solvent under an inert gas atmosphere, then adding catalyst and perfuming Stille coupling reaction at 60-120 degrees C for 24-72 hours, separating and purifying of reaction solution to obtain (I). Preferred Method: The step of performing Stille coupling reaction comprises evaporating the excess solvent present in the reaction solution under reduced pressure, then adding methanol dropwise and allowing for sedimentation, washing with methanol after filtration, passing through an alumina column chromatography after drying, steaming to remove the organic solvent by using chloroform as eluent, after methanol sedimentation and filtration, the resulting solid is subjecting to Soxhlet extraction with acetone, allowing for sedimentation and filtering to obtain (I). Preparation of (A) comprises adding N-alkyl-5,8-dibromo-dithiophene(3?,2?:3,4;2?,3?:5,6)benzo(1,2-d)(1,2,3)triazole, thieno(3,2-b)thiophene boronic acid derivative, carbonate, palladium catalyst and reaction solvent in a reaction flask under an inert gas atmosphere at 60-120 degrees C under stirring and reflux for 24-72 hours, cooling to room temperature and then reaction mixture is poured into distilled water, extracting with dichloromethane after combining the organic phase with saturated salt, washing with water, drying the filter, separating and purifying by silica gel column to give the compound the reaction solution, where the molar ratio of N-alkyl-5,8-dibromo-dithiophene(3',2':3,4;2'',3'':5,6)benzo(1,2-d)(1,2,3)triazole, thieno(3,2-b)thiophene boronic acid derivative is 1:1.1-1.2, alkali is carbonate, amount of N-alkyl-5,8-dibromo-dithiophene(3',2':3,4;2'',3'': 5,6)benzo(1,2-d)(1,2,3)triazole is 3-5 times. The palladium catalyst is bis(triphenylphosphine)palladium(II) dichloride or tetrakis(triphenylphosphine)palladium, the molar amount of N-alkyl-5,8-dibromo-dithiophene(3',2':3,4;2'',3'':5,6)benzo(1,2-d)(1,2,3)triazole is 0.01%-5%, the solvent is tetrahydrofuran, N,N-dimethylformamide or dimethylsulfoxide, and adding the reaction solution into dry tetrahydrofuran under anhydrous oxygen-free conditions and cooled to -78 degrees C, using injector slowly adding N-hexane solution of 5 mol/l n-butyllithium at -78 degrees C under stirring for 2-3 hours and then adding tetrahydrofuran solution of trimethyltin chloride and incubating at room temperature for 5 hours after that continuing the reaction for 20-24hours and stopping the reaction, evaporating the excess solvent to give (A), where the dosage of n-butyllithium and trimethyltin chloride is 2.2-2.5 times the amount of the reaction solution.