TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The catalyst is tris(dibenzylideneacetone)palladium, tetrakis(triphenylphosphine)palladium or bis(triphenylphosphine)palladium dichloride. The molar amount of the catalyst is 0.05-20% the molar amount of (II).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): The preparation of (I) comprises dissolving broom-substituted benzothiadiazole compounds of formula (II) and 5,5'-bis(tributylstannyl)-2,2'-bithiophene compounds of formula (III) at molar ratio of 1:1.5-1.5:1 in an organic solvent under an inert gas atmosphere, then adding a catalyst, performing Stille coupling reaction for 6-100 hours at 50-120 degrees C, and separating and purifying to obtain (I). Preferred Method: (II) is prepared by dissolving 7,7'-dibromo-5,5'-diiodo-4,4'-bibenzo(c)(1,2,5)thiadiazole (IV) in a first solvent under an inert gas atmosphere to obtain a first mixed solution, dropping n-butyl lithium into the solution, stirring and reacting for 2 hours at -90 degrees C, adding substituted silyl dichloride compounds of formula (R1R2-Si(Cl)2) (V), reacting for 10 hours at room temperature, separating and purifying, where the molar ratio of n-butyl lithium to (IV) is 2:1-4:1, and the molar ratio of (IV) to (V) is 1:2. (IV) is prepared by: (a) dissolving 2-amino-5-nitroaniline and pyridine in a thionyl chloride, refluxing and reacting for 24 hours at 80-90 degrees C, separating and purifying to obtain 5-nitro-2,1,3-benzothiadiazole (IVa); (b) mixing (IVa) with hydrobromic acid to obtain a mixture, warming the mixture to 127 degrees C and refluxing, and then dropping liquid bromine and refluxing for 4 hours, separating and purifying to obtain 4,7-dibromo-5-nitro-2,1,3-benzothiadiazole (IVb); (c) adding N,N-dimethyl formamide to (IVb) and copper powder, heating to 120 degrees C and reacting for 3 hours, separating and purifying to obtain 4,4'-dibromo-6,6'-dinitro-linked-2,1,3-benzothiadiazole (IVc); and (d) adding N,N-dimethyl formamide to (IVc), then adding tin dichloride, heating to 100 degrees C and refluxing for 10 hours, and separating and purifying. (III) is prepared by dissolving 5,5'-dibromo-2,2'-bithiophene compounds of formula (VI) in a second solvent under inert atmosphere to obtain second mixed solution, dropping n-butyllithium into the solution under -78 degrees C and reacting for 1-2 hours, then adding tributyltin chloride and reacting for 1 hour at -78 degrees C, and then reacting for 6 hours at room temperature, and separating and purifying, where the molar ratio of (VI) to n-butyllithium is 1:2, and the molar ratio of (VI) to tributyltin chloride is 1:2. The separation purification comprises adding de-ionized water and toluene into the reaction solution and performing extraction, distilling the collected organic phase under reduced pressure and concentrating, dropping concentrated organic phase to a anhydrous ethanol, stirring constantly, separating out precipitated solid, filtering, drying obtained solid powder, dissolving the solid powder in chloroform, and then passing through neutral alumina column chromatography, removing chloroform under reduced pressure, sedimentation of methanol, filtering, extracting obtained solid using acetone in a Soxhlet extractor, and then sedimentation of methanol and filtering to obtain purified (I). Preferred Components: The organic solvent is tetrahydrofuran, ethylene glycol dimethyl ether, dimethyl ether, benzene or toluene.