Benzodifuran and benzodithiophene donor–acceptor polymers for bulk heterojunction solar cells

Abstract

Four new donor–acceptor copolymers were synthesized by using benzo[1,2-b:4,5-b′]dithiophene and benzo[1,2-b:4,5-b′]difuran as donors and thieno[3,4-b]thiophene was used as the acceptor building block. A systematic study was performed to determine the influence of the combinations of different heteroatoms in the donor–acceptor copolymer. In bulk heterojunction solar cells, the polymer with all furan building blocks in the electron donating units, poly[(4,8-bis(5-dodecyl-2-furanyl)benzo[1,2-b:4,5-b′]difuran-2-yl)-alt-(2-ethyl-1-(3-fluorothieno[3,4-b]thiophen-2-yl)-1-hexanone)] (P4) (M_n = 66.7 kDa), achieved the highest power conversion efficiency of 5.23%.