Novel benzodithiophene unit with an alkylthiobiphenyl side chain for constructing high-efficiency polymer solar cells

Abstract

A novel BDT monomer with an alkylthiobiphenyl side chain named 4,8-bis(4′-((2-hexyldecyl)thio)-[1,1′-biphenyl]-4-yl)benzo[1,2-b:4,5-b′]dithiophene (BDTBPS) was designed and synthesized. The polymer named PBDTBPS–BDD was synthesized with BDTBPS and benzo[1,2-b:4,5-b′]dithiophene-4,8-dione (BDD). Solar cells were studied by blending the polymer PBDTBPS–BDD with both fullerene and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC). The optimized polymer solar cells showed a PCE of 8.40% and 9.76% for the PC₇₁BM-based and ITIC-based solar cells, respectively. This research indicates that the novel monomer is a promising unit for constructing high-efficiency polymer solar cells.