title: Dithienogermole as a fused electron donor in bulk heterojunction solar cells.
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.
authors.affiliation: The George and Josephine Butler Polymer Research Laboratory, Department of Chemistry, Center for Macromolecular Science and Engineering, University of Florida, Box 117200, Gainesville, Florida 32611, USA.
authors.forename: Chad M
authors.initials: CM
authors.lastname: Amb
authors.forename: Song
authors.initials: S
authors.lastname: Chen
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Graham
authors.forename: Jegadesan
authors.initials: J
authors.lastname: Subbiah
authors.forename: Cephas E
authors.initials: CE
authors.lastname: Small
authors.forename: Franky
authors.initials: F
authors.lastname: So
authors.forename: John R
authors.initials: JR
authors.lastname: Reynolds