1. Department of Nanofusion Technology, Department of Cogno‐Mechatronics Engineering (WCU), Pusan National University, , Miryang, 627–706 Republic of Korea;2. Interdisciplinary School of Green Energy, KIER‐UNIST Advanced Center for Energy, Ulsan National Institute of Science and Technology (UNIST), , Ulsan, 689–798 Republic of Korea
Abstract:
A semicrystalline low‐bandgap polymer (PDTPBT) based on alternating dithienopyrrole and benzothiadiazole moieties as a pair of the indene‐C60 bisadduct (ICBA) for polymeric solar cells is reported. The lowest unoccupied molecular orbital (LUMO) level of PDTPBT is measured to be ?3.47 eV, ensuring sufficient energy offset for photoinduced charge transfer to ICBA. Photovoltaic cells are fabricated with ICBA and 6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) as an acceptor. By replacing PC71BM with ICBA, the open‐circuit voltage is increased by 0.23 V and the resulting power conversion efficiency is improved from 1.17% to 1.71%. To optimize the ICBA‐based devices, crystalline low‐bandgap structures should be designed carefully as a pair of ICBA by considering the energy‐level offset for charge separation and crystalline interchain ordering, for minimizing the intercalated ICBAs inside the polymer domain.
