Designing High Performance Nonfullerene Electron Acceptors with Rylene Imides for Efficient Organic Photovoltaics

Improving carrier mobility, redox stability, blend morphology, and photovoltaic performance while elucidating structure–property relationships remains an important design goal for nonfullerene electron acceptors (NFAs) for organic solar cells. Although numerous NFAs have been created from rylene diimide electron-deficient building blocks, they have shown far inferior photovoltaic properties compared to benchmark fused-ring electron acceptors (FREAs) such as ITIC. Herein we show that new bis(naphthalene-imide)arylenelidenes (BNIAs), incorporating rylene-imide end-capping groups via methine bridges in donor–acceptor architectures, are endowed with enhanced electrochemical redox stability, high carrier mobilities, and high photovoltaic performance. Pairing of those BNIAs that are also FREAs, NIDT and NIBT, respectively, with donor polymer PBDB-T produced 10.0–10.8% efficient photovoltaic devices, which are comparable to benchmark ITIC devices. Blends of FREAs NIDT and NIBT and those of non-FREA NITV were found to have similar electron mobilities, demonstrating that the much higher photovoltaic efficiency of NIDT and NIBT devices does not originate from enhanced charge transport but from differences in blend morphology and blend photophysics. The results demonstrate that incorporating rylene imides into molecular architectures through the methine-bridged donor–acceptor coupling motif is a promising design strategy toward more efficient and electrochemically rugged materials for organic solar cells.