High-Performance Mid-Bandgap Fused-Pyrene Electron Acceptor

A new mid-bandgap nonfullerene acceptor, FPIC, is designed and synthesized on the basis of a novel fused-pyrene electron-donating core. FPIC exhibits intense light absorption between 500 and 750 nm, with a maximum molar extinction coefficient of 2.3 × 105 M–1 cm–1 at 645 nm, a medium optical bandgap of 1.63 eV, and a high electron mobility of 1.7 × 10–3 cm2 V–1 s–1. The ternary blend organic solar cells (OSCs) consisting of low-bandgap donor PTB7-Th, ultra-narrow-bandgap nonfullerene acceptor F8IC, and FPIC yield a high power conversion efficiency (PCE) of 13.0%, significantly surpassing the PCE value of the PTB7-Th/F8IC binary blend OSCs (9.55%). The ternary blend exhibits complementary absorption, effective exciton dissociation, balanced charge transport, and reduced charge recombination, leading to the improvement in open-circuit voltage, short-circuit current density, and fill factor relative to those of its PTB7-Th/F8IC counterpart. This work indicates that the mid-bandgap fused-pyrene electron acceptor FPIC is a promising third component for enhancing the photovoltaic performance of low-bandgap donor/acceptor binary blends.