TECHNOLOGY FOCUS - POLYMERS - Preparation (claimed): In an inert atmosphere, 7,7'-dibromo-5,5'-diiodo-(4,4')bi(benzo(1,2,5)thiadiazolyl) (compound II) and an alkyne compound (B) of formula: R2-CC-R3 are cyclized in a molar ratio of 1:2 in the presence of catalyst (I) and alkali solution (I) in solvent (I) at 100-150 degrees C for 2-6 hours, to obtain a dibromo-benzo-di(benzothiadiazole) compound of formula (III). In an inert atmosphere, a dibromo silole-containing dithiophene compound of formula (IV) is dissolved in tetrahydrofuran at -78 degrees C. n-Butyl lithium is added, stirred, and reacted for 1-2 hours. Tributyl tin chloride is added and reacted for 1 hour and then reacted at room temperature for 6 hours, to obtain a tributyltin silole-containing dithiophene compound of formula (V). The molar ratio of compound (IV) and n-butyl lithium is 1:2. The molar amounts of tributyl tin chloride and n-butyl lithium are the same. In an inert atmosphere, compound (III) and compound (V) are subjected to Stille coupling reaction in a molar ratio of 1:1.5-1.5:1 in the presence of solvent (II) and catalyst (II) at 50-120 degrees C for 6-100 hours, to obtain compound (I). Preferred Method: Compound (II) is obtained by stirring 2-amino-4-nitrophenylamine with thionyl chloride, dripping in pyridine, reflux-reacting at 85 degrees C or less, adding obtained 5-nitro-2,1,3-benzothiadiazole to hydrobromic acid, reflux-reacting at 127 degrees C or less for 30 minutes, heat-reacting obtained 4,7-dibromo-5-nitro-2,1,3-benzothiadiazole in the presence of copper catalyst in N,N-dimethylforamamide at 120 degrees C for 3 hours, adding obtained 7,7'-dibromo-5,5'-dinitro-4,4'-bi-2,1,3-benzothiadiazole and tin chloride to tetrahydrofuran, and heat-refluxing at 100 degrees C for 10 hours. The Stille coupling reaction temperature is 70-100 degrees C and time is 24-72 hours. Preferred Compounds: Catalyst (I) is palladium acetate. The usage amount of catalyst (I) is 10% of compound (II). The alkali solution is tributylamine solution. The molar ratio of alkali solution and alkyne compound is 1:1. Solvent (I) is N,N-dimethylformamide. Catalyst (II) is tetrakis(triphenylphosphine)palladium, tris(dibenzylideneacetone)dipalladium, or bis(triphenylphospine)palladium dichloride. The usage amount of catalyst is 0.05-20 mol% with respect to compound (V). Solvent (II) is tetrahydrofuran, ethylene glycol dimethyl ether, diethyl ether, benzene, or toluene.