TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): A bromine-containing compound of formula (II) and a borane of formula (III) in molar ratio of 1:1.5-1.5:1 are dissolved in organic solvent under inert gas atmosphere, then catalyst and alkali solution are added to form mixed solution, the mixed solution is subjected to Suzuki coupled reaction at 50-120 degrees C for 6-100 hours, reaction is stopped, separated and purified, to obtain fluorene-bis(benzothiadiazole)copolymer. Preferred Process: 4-Nitrobenzene-1,2-diamine and thionyl chloride are mixed in liquid ratio of 0.2295 g:1 mL in presence of pyridine catalyst, reaction mixture was refluxed at 90 degrees C for 24 hours, excess amount of thionyl chloride is distilled-off and mixture is cooled to room temperature, to obtain 5-nitro-2,1,3-benzothiadiazole. The 5-nitro-2,1,3-benzothiadiazole and 40% hydrobromic acid in liquid ratio of 0.69 g:1 mL are mixed, refluxed at 127 degrees C, slowly adding liquid bromine, and refluxing at for 30 minutes for 4 hours, to obtain 4,7-dibromo-5-nitro-2,1,3-benzothiadiazole. The 4,7-dibromo-5-nitro-2,1,3-benzothiadiazole and copper in weight ratio of 1.07:1 are added to N,N-dimethyl formamide, reaction mixture is heated at 120 degrees C for 3 hours, reaction is stopped and cooled to room temperature, to obtain 4,4'-dibromo-6,6'-dinitro-2,1,3-benzothiadiazole. The 4,4'-dibromo-6,6'-dinitro-2,1,3-benzothiadiazole and tin dichloride in molar ratio of 1:10 are added to dry tetrahydrofuran, heated at 100 degrees C, refluxed for 10 hours, reaction is stopped, cooled, adding sodium nitrite solution, reacting at less than 5 degrees C for 30 minutes, reaction solution is added in drops into potassium iodide solution, vigorously stirred, reacted for 12 hours, and reaction is stopped, to obtain 4,4'-dibromo-6,6'-diiodo-2,1,3-benzothiadiazole. The 4,4'-dibromo-6,6'-diiodo-2,1,3-benzothiadiazole is added with solvent mixture of n-butyllithium and dichlorosilane of formula (II-1), stirred at room temperature for 10 hours, reacted, such that 4,4'-dibromo-6,6'-diiodo-2,1,3-benzothiadiazole and dichlorosilane are subjected to ring closure reaction, to obtain bromine-containing compound (II). The borane (III) is prepared by providing dibromo fluorine derivative of formula (IV), mixing dibromo fluorine derivative (IV) and 2-isopropoxy-4,4,5,5-tetramethyl-(1,3,2)dioxaborolane under inert atmosphere, cooled to -78 degrees C, adding n-butyllithium and 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, reacting for 1-2 hours, cooling obtained reaction mixture to room temperature and reacting for 6 hours.R3,R4=1-20C alkyl.Preferred Composition: The catalyst is chosen from tris(dibenzylideneacetone) dipalladium, tetrakis(triphenylphosphine) palladium and bis triphenylphosphine palladium dichloride. The molar amount of catalyst is 0.05-20% of bromine-containing compound. The organic solvent is chosen from tetrahydrofuran, ethylene glycol dimethyl ether, ethyl ether, benzene and toluene. The molar amount of dichlorosilane is 2 times of molar amount of 4,4'-dibromo-6,6'-diiodo-2,1,3-benzothiadiazole. The molar ratio of n-butyllithium and 4,4'-dibromo-6,6'-diiodo-2,1,3-benzothiadiazole is 2 to less than 4. The liquid ratio of 5-nitro-2,1,3-benzothiadiazole and liquid bromine is 1 g:1.09 mL. The solid-liquid ratio of 4,7-dibromo-5-nitro-2,1,3-benzothiadiazole and N,N-dimethylformamide is 1 g:8.82 mL. The molar ratio of sodium nitrite and 4,4'-dibromo-6,6'-dinitro-2,1,3-benzothiadiazole is 1.885:1. The molar ratio of potassium iodide and 4,4'-dibromo-6,6'-dinitro-2,1,3-benzothiadiazole is 18.6:1. The molar ratio of dibromo fluorine derivative and n-butyllithium is 1:2. The molar ratio of dibromo fluorine derivative and 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane is 1:2.