TECHNOLOGY FOCUS - POLYMERS - Preferred Process: The fluorenyl copolymer is prepared by reacting, 5-methyl-thieno (3,4-c)pyrrole-4,6-dione (III), 2,3,4-trimethyl-thiophene-tin-t-butoxide (IV), with organic solvent to obtain the coupling product. The coupling product is added with bromating agent to obtain the dibromo product. The 4,4,5,5-tetramethyl-2-phenyl-(1,3,2)dioxaborolane compound is reacted with 2,3,4-trimethyl-thiophene (V), organic solvent and dibromo product to obtain the fluorenyl copolymer(I). The fluorenyl copolymer is prepared by reacting 5-methyl-thieno(3,4-c)pyrrole-4,6-dione compound, 2,3,4-trimethyl-thiophene-tin-t-butoxide with 2,3,4-trimethyl-thiophene at 60-120 degrees C for 12-24 hours at mol ratio of 2.0:a:b to obtain a coupling product, where the a is greater than 0, b is greater than 0, a+b is 2-4. The catalyst comprises organic palladium catalyst or the mixtures of organic palladium catalyst and organic phosphorus ligand. The fluorenyl copolymer is prepared by adding the coupling product and brominating agent into the organic solvent at 0-30 degrees C for 12-48 hours at a mol ratio of 1.0:2.0-1.0:2.5 to obtain a dibromo product. The fluorenyl copolymer is prepared by reacting 4,4,5,5-tetramethyl-2-phenyl-(1,3,2)dioxaborolane and 2,3,4-trimethyl-thiophene and dibromo product at 65-120 degrees C for 24-72 hours at mol ratio of 1.0:c:d to obtain a fluorenyl copolymer, where the c is greater than 0, d is greater than 0, c+d is 0.9-1.1. The alkali solution comprises alkali metal hydroxide or alkali metal carbonate water solution or tetra alkyl ammonium hydroxide water solution. The fluorenyl copolymer is prepared by mixing 2,7-dibromo-9,9-dialkyl silicon fluorenyl and alkyl lithium at 100-25 degrees C, adding 2- isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxane pentaborane and reacting for 24-48 hours to obtain a 4,4,5,5-tetramethyl-2-phenyl-(1,3,2)dioxaborolane. The fluorenyl copolymer is prepared by adding thiophene-3,4- dicarboxylic acid and acetic anhydride, stirring for 12-24 hours, adding organic solvent alkyl amine at 100-120 degrees C for 24-32 hours and cooling to obtain mixed product. The mixed product is subjected to adding thionyl chloride at 80-100 degrees C, refluxing for 1-12 hours to obtain a 5-alkyl thiophene (3, 4-c) pyrroledione-4, 6-diketone. The 5-alkyl thiophene (3,4-c) pyrroledione-4, 6-diketone is added with brominating agent and organic solvent at 10-30 degrees C for 12-48 hours to obtain a 1,3-dibromo-5-alkyl thiophene (3,4-c)pyrroledione-4,6-diketone.