TECHNOLOGY FOCUS - POLYMERS - Preparation (Claimed): The preparation of (I), comprises dissolving silolo-bis(benzothiadiazole) compounds of formula (II) and 2,7-bis-tributylstannanyl-benzo(2,1-b;3,4-b')dithiophene compounds of formula (III) in a molar ratio of 1:1.5-1.5:1 in an organic solvent under inert gas atmosphere, adding a catalyst, and carrying out Stille coupling reaction at 50-120 degrees C for 6-100 hours, and then separating and purifying obtained reacted mixture to obtain final product. Preferred Method: (II) is prepared by (i) reacting 4-nitrophenylene-1,2-diamine with thionyl chloride and pyridine at 80-90 degrees C for 24 hours to obtain 5-nitro-2,1,3-benzothiadiazole, where weight ratio between 4-nitrophenylene-1,2-diamine and thionyl chloride is 1.5:1 mol/l, and volume ratio of thionyl chloride to pyridine is 50:1, (ii) carrying out bromination reaction of 5-nitro-2,1,3-benzothiadiazole with hydrobromic acid and liquid bromine at 127 degrees C for 4 hours to obtain 4,7-dibromo-5-nitro-2,1,3-benzothiadiazole, where mass fraction of hydrobromic acid is 40%, weight ratio between 5-nitro-2,1,3-benzothiadiazole and hydrobromic acid is 4:1 mol/l, and weight ratio of 5-nitro-2,1,3-benzothiadiazole to liquid bromine is 5.3: 1 mol/l, (iii) carrying out coupling reaction of 4,7-dibromo-5-nitro-2,1,3-benzothiadiazole in presence of copper powder catalyst at 120 degrees C for 3 hours to obtain 4,4'-dibromo-6,6'-dinitro-bi(2,1,3-benzothiadiazole), where weight ratio between 4,7-dibromo-5-nitro-2,1,3-benzothiadiazole and copper powder is 0.2:1, (iv) carrying out reduction of 4,4'-dibromo-6,6'-dinitro-bi(2,1,3-benzothiadiazole) with stannous chloride at 100 degrees C for 10 hours, carrying out diazotization reaction in presence of hydrochloric acid and sodium nitrite at 5 degrees C for 30 minutes, and reacting with potassium iodide for 12 hours to obtain 4,4'-dibromo-6,6'-diiodo-bi(2,1,3-benzothiadiazole), where molar ratio between 4,4'-dibromo-6,6'-dinitro-bi(2,1,3-benzothiadiazole) and stannous chloride is 1:10, molar ratio of 4'-dibromo-6,6'-dinitro-bi(2,1,3-benzothiadiazole) to hydrochloric acid is 0.92:1, molar ratio of 4,4'-dibromo-6,6'-dinitro-bi(2,1,3-benzothiadiazole) to sodium nitrite is 0.53:1, and molar ratio of 4,4'-dibromo-6,6'-dinitro-bi(2,1,3-benzothiadiazole) to potassium iodide is 0.054:1, and (v) reacting 4,4'-dibromo-6,6'-diiodo-bi(2,1,3-benzothiadiazole) with n-butyllithium in dimethylformamide solvent at -90 degrees C for 2 hours under anaerobic condition, then reaction with dichlorosilane compounds of formula (R1-Si(R2)(Cl)-Cl) (IV) at room temperature for 10 hours to obtain (II), where molar ratio between n-butyllithium and 4,4'-dibromo-6,6'-diiodo-bi(2,1,3-benzothiadiazole) is greater than or equal to 2 and less than or equal to 4, molar ratio of (IV) to 4,4'-dibromo-6,6'-diiodo-bi(2,1,3-benzothiadiazole) is 2:1. (III) is prepared by adding 2,7-dibromol-benzo(2,1-b;3,4-b')dithiophene compounds of formula (V) into tetrahydrofuran under an inert gas atmosphere, cooling to -78 degrees C, adding n-butyl lithium, where molar ratio of (V) to n-butyllithium is 1:2, then reacting for 2 hours, adding tributyltin chloride at -78 degrees C, where molar ratio of (V) to tributyltin chloride is 1:2, and reacting at -78 degrees C for 1 hour, then raise temperature to room temperature and reaction for 6 hours, and separating to obtain (III). The separation and purification step in the preparation of (I), comprises adding the reacted mixture into deionized water, extracting with toluene, taking organic phase, vacuum distilling, adding anhydrous alcohol, separating out precipitate, filtering, drying obtained solid powder, dissolving the solid powder in chloroform, separating by silica gel column chromatography using toluene as eluent, vacuum distilling the eluate, carrying out liquid with methanol, filtering, extracting obtained solid with acetone in a Soxhlet extractor for three days, then precipitating with methanol, filtering, and carrying out suction filtration to obtain pure product (I). Preferred Components: The preparation of (I): the catalyst is tris(dibenzylideneacetone)dipalladium, bis(triphenylphosphine)palladium dichloride or tetrakis(triphenylphosphine)palladium; used amount of the catalyst is 0.5-20% of the amount of (II); the organic solvent is tetrahydrofuran, ethylene glycol dimethyl ether, benzene or toluene.