One-Step Synthesis of New Electron Acceptor for High Efficiency Solution Processable Organic Solar Cells

Here, we demonstrate a new fulleropyrrolidine electron acceptor coded as DIF-ful-C₆₀, following a one-step synthetic protocol. The absorption spectrum of DIF-ful-C₆₀ suggests broader absorption over PC₆₁BM while the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the molecule are -5.32 and -3.60 eV, respectively. The solution processed bulk-heterojunction polymer solar cells fabricated using a blend of DIF-ful-C₆₀ with PTB7 and PTB7-Th as electron donors show power conversion efficiencies (PCEs) of 6.8 and 8.6%, respectively, which is highest reported so far for fulleropyrrolidine type electron acceptors. In comparison, the control devices made from PTB7:PC₆₁BM and PTB7-Th:PC₆₁BM blends showed PCEs of 6.2 and 7.9%, respectively. The increase in efficiency of the devices based on DIF-ful-C₆₀ is due to increase in the short circuit current as well as open circuit voltage of ca. 0.8 V.