NOVELTY - A fluorine copolymer comprises thienothiophene and thiophene pyrrole diketone compound (I).    USE - Fluorine copolymer.    ADVANTAGE - The copolymer has improved stability and photon-to-electron conversion efficiency, and can be prepared with high yield and controllability.    DETAILED DESCRIPTION - A fluorine copolymer comprises thienothiophene and thiophene pyrrole diketone compound of formula (I).    R1-R3=1-20C alkyl;    R4-R9=H or 1-20C alkyl;    x,y=not equal to 0;    x+y=1;and    n=1-200.    B1=fluorene monomer.    INDEPENDENT CLAIMS are also included for the following:    (1) a process for preparing fluorine copolymer, which involves reacting fluorene monomer compound of formula (II), thiophene monomer compound of formula (III) and thiophene pyrrole diketone monomer compound of formula (IV) in the presence of catalyst solution of acid and base, and organic solvent at 65-120 degrees C for 24-72 hours    (2) a process for preparing fluorene monomer compound (II), which involves reacting bromo-substituted fluorene compound of formula (A1) with dioxolane compound of formula (A2) in the presence of n-butyl lithium    (3) a process for preparing thiophene monomer compound (III), which involves reacting thiophene compound of formula (A3) in the presence of N-bromosuccinimide and organic solvent at 0-30 degrees C for 12-48 hours, where the organic solvent is chosen from N,N-dimethyl formamide, tetrahydrofuran, ether, dichloromethane, trichloromethane, ethyl acetate or acetic acid    (4) a process for preparing thiophene pyrrole diketone monomer compound (IV), which involves reacting 1,3-dibromo-thieno(3,4-c)pyrrole-4,6-dione of formula (V) with thiophene compound of formulae (A4) and (A5) to obtain thiophene pyrrole diketone compound (VI), and reacting the compound (VI) in the presence of N-bromosuccinimide    (5) an organic solar battery device comprising a substrate base material depositing on a surface of the substrate, and a conductive layer of an anode containing poly(3,4-ethylenedioxy thiophene):poly (styrene sulfonic acid) layer, an insulating layer containing poly (3,4-ethylenedioxy thiophene):poly(styrene sulfonic acid) arranged between the active material and the surface of the metallic aluminium layer as a cathode, where the active layer is a mixture comprising electron donor material and electron acceptor material, the electron acceptor material is (6,6)-C61-butyrate, and the electron donor material is thiophene bithiophene and thiophene pyrrole fluorene copolymer    (6) an organic field effect transistor comprising doped silicon chip, silicon dioxide insulating layer, alkyl chlorosilane layer, acid alkyl chlorosilane organic semiconductor layer, a source electrode and a drain electrode set on the organic semiconductor layer.