Journal of the American Chemical Society 2011-07-06

Dithienogermole as a fused electron donor in bulk heterojunction solar cells.

Chad M Amb, Song Chen, Kenneth R Graham, Jegadesan Subbiah, Cephas E Small, Franky So, John R Reynolds

Index: J. Am. Chem. Soc. 133 , 10062-10065, (2011)

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Abstract

We report the synthesis and bulk heterojunction photovoltaic performance of the first dithienogermole (DTG)-containing conjugated polymer. Stille polycondensation of a distannyl-DTG derivative with 1,3-dibromo-N-octyl-thienopyrrolodione (TPD) results in an alternating copolymer which displays light absorption extending to 735 nm, and a higher HOMO level than the analogous copolymer containing the commonly utilized dithienosilole (DTS) heterocycle. When polyDTG-TPD:PC(70)BM blends are utilized in inverted bulk heterojunction solar cells, the cells display average power conversion efficiencies of 7.3%, compared to 6.6% for the DTS-containing cells prepared in parallel under identical conditions. The performance enhancement is a result of a higher short-circuit current and fill factor in the DTG-containing cells, which comes at the cost of a slightly lower open circuit voltage than for the DTS-based cells.