Benzodithiophene based copolymer containing thieno [3,4-B] thiophene units and preparing method and applications thereof

A method for preparing a benzodithiophene based copolymer containing thieno[3,4-b]thiophene units, comprising the steps of:

• adding M1 and M2 to a solvent in an oxygen-free environment;
• performing a refluxing reaction in the presence of catalyst;
• the reaction formula is as follows:
• wherein R1 and R2 are selected from the group consisting of H, and C1 to C16 alkyl, respectively;
• R3 and R4 are selected from the group consisting of H, C1 to C16 alkyl, C1 to C16 alkoxy, and thienyl substituted by C1 to C16 alkyl, respectively;
• R5 is C1 to C16 alkyl;
• n is a natural number from 7 to 80;
• a molar ratio between M1 and M2 is 1:1 to 1.5:1;
• the solvent is at least one selected from the group consisting of toluene, tetrahydrofuran, benzene, and N,N-dimethylformamide;
• the catalyst is organic palladium or a mixture of organic palladium and organic phosphine ligand, a molar amount of the catalyst is 0.01% to 5% of the molar amount of the M2;
• the organic palladium is Pd2(dba)3, Pd(PPh3)4 or Pd(PPh3)2Cl2, a molar ratio between the organic palladium and the organic phosphine ligand in the mixture is 1:2 to 1:20;
• the organic phosphine ligand is P(o-Tol)3 or tricyclohexylphosphine;
• the reaction is performed at a temperature ranging from 60° C. to 120° C. for 12 to 72 hours.