NOVELTY - A dibromothiophene pentafluorophenyl pyrrole dione monomer (I) is new.    USE - Dibromothiophene pentafluorophenyl pyrrole dione monomer used in polymer solar cell device (claimed).    ADVANTAGE - The monomer can improve utilization rate and carrier of sunlight migration efficiency to effectively improve thermal stability of polymer and increase service life of solar cell device.    DETAILED DESCRIPTION - A dibromothiophene pentafluorophenyl pyrrole dione monomer of formula (I) is new. INDEPENDENT CLAIMS are included for:    (1) a pentafluorophenyl pyrrole dione-benzothiophene copolymer of formula (II); and    (2) preparation of the copolymer (II), comprising mixing 3,4-thiadiazole phenothiazine dicarboxylic acid and thionyl chloride in an anaerobic environment filled with inert and reacting at 10-100 degrees C for 1-14 hours, cooling to room temperature, decompression distilling to obtain crude product 3,4-dimethylthiophene; adding crude product with acyl chloride in organic solvent, then slowly dripping pentafluoroaniline in toluene solution and reacting at 10-120 degrees C for 1-14 hours, cooling to room temperature, distilling, extracting, washing, and refining by column chromatography to obtain pentafluoro-phenyl-4H-thiophene-(3,4-c)-pyrrole-4,6-(5H)-dione white crystal; adding white crystal with N-bromosuccinimide and sulfuric acid mixed solution, reacting at 70 degrees C for 1-24 hours, after reaction is finished, extracting, washing, and refining by column chromatography to obtain pentafluorophenyl-4H-thiofuran-(3,4-c) pyrrole-4,6-(5H)-dione bromide monomer; adding monomer with benzo-thiophene derivative , then adding organic palladium catalyst and organic solvent and reacting at 40-110 degrees C for 12-72 hours, cooling to room temperature, dropping anhydrous methanol, filtering to obtain copolymer crude product, drying the crude product, crystallizing using methanol, n-hexane and chloroform to obtain purple black copolymer solid.    R1, R2=H, 1-20C alkyl or phenyl; and    n=10-100.