In view of the donor-acceptor (D-A) copolymers used in the active layer of organic solar cells at present

the selection of D-A donor materials is the key problem in the design of highly efficient organic solar cells. In this paper

we selected 10 D units and A units respectively

using the first principles density functional method

studied the energy gap changes of D

A unit and its corresponding copolymer structure. The results show that the number of thiophene ring when thiophene fused thiophene ring and the number of benzene ring when thiophene fused benzene ring can effectively modulate the size and the position of the band gap; In the same time

the position of the S atom on the thiophene ring also has a certain influence on the band gap; Based on this

three kinds of polymers with smaller band gap value are selected

which are thieno thiophene(TT)

4

4-bis(2-ethylhexyl)-4H-germolo dithiophene(DTG)and diketopyrrolopyrrole(DPP)as monomer. The electronic structure characteristics of three kinds of high short-circuit current donor material PDTG-PT

PNTz4T and DPPTT-T have been studied. By analyzing the molecular chain conformation

Bader charge transfer and binding energy of the donor

it is indicated that they are the ideal choice for the D-A type donor materials of organic solar cells with high short-circuit current. This study provides valuable guidance for the design of D-A type of organic solar cells with high short-circuit current.