Increased open-circuit voltage in bulk-heterojunction solar cells using a C60 derivative

The fullerene derivative C-60-fused N-methyl-2-(3-hexylthiophen-2-yl) pyrrolidine (C-60-TH-Hx) is used as the acceptor material in bulk-heterojunction (BHJ) solar cells fabricated with the low band-gap polymer poly[4,4'-bis(2-ethylhexyl)dithiene[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(4,7-bis(2-thienyl)-2,1,3-benzothiadiazole)-5,5'-diyl]. Direct comparison with BHJ solar cells based on [6,6]-phenyl-C-61-butyric methyl ester and Si-PCPDTBT indicates that the C-60-TH-Hx acceptor yields a larger open-circuit voltage because of higher lowest unoccupied molecular orbital energy level of C-60-TH-Hx. (C) 2010 American Institute of Physics. [doi:10.1063/1.3518066]