Bulk heterojunction solar cells of three polythienothiophenes

Semiconducting conjugated copolymers poly(3-phenyl-2-(thiophen-2-yl)thieno[3,2-b]thiophene) (PTTPh), poly(3-(4-methoxyphenyl)-2-(thiophen-2-yl)thieno[3,2-b]thiophene) (PTTPh-OMe) and poly(3-(4-N,N-dimethylaminophenyl)-2-(thiophen-2-yl)thieno[3,2-b]thiophene) (PTTPh-N(CH 3) 2), which were synthesized previously through Suzuki coupling method, were fabricated for solar cell applications. The devices had a structure of glass/ITO/PEDOT:PSS/polymer:PC61BM/Al. Bulk heterojunction photovoltaic cells were prepared as blends of PTTPh, PTTPh-OMe, PTTPh-N(CH 3) 2 and PC61BM in a 1:1 ratio, which delivered power conversion efficiencies of 0.43%, 0.039% and 0.027%, respectively, without addition of additives or device optimization.