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

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%.