Abstract
Advances in improving the operational lifetime of highly efficient organic photovoltaic (OPV) and understanding photo-degradation mechanisms in molecular level are currently limited, especially on the promising inverted OPV, posing critical challenges to commercialization. Here, we demonstrate a radical scavenger (3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionic acid) capped ZnO (BHT@ZnO) nanoparticles as the electron transport layer providing effective surface oxygen vacancy passivation and reactive radical capture capability. Encouragingly, this BHT@ZnO-based empowered device achieves a record inverted OPV efficiency of 19.47% (Certificated efficiency: 18.97%). The devices demonstrate light soaking-free behavior, long-term stability under ISOS-D-1 (94.2% PCE retention after 8904 h in ambient) and ISOS-L-1 testing protocol (81.5% PCE retention after 7724 h in MPP). More importantly, we elucidate detailed degradation mechanism in OPV involving selectively catalytic degradation of donor and acceptor by superoxide and hydroxyl radicals, respectively, as well as the degradation pathway of polymer donor upon radiation exposure. Performance enhancement and mechanism comprehension provide strong support for the development of OPV technology.