Polarization-Induced Trap States in Perovskite Solar Cells Revealed by Circuit-Switched Transient Photoelectric Technique

Ion migration in perovskite solar cells (PSCs) is a crucial factor governing both photoelectric performance and physicochemical stability of the devices. However, the related fundamental research, especially the quantitative studies of the ion migration dynamics at a device level, has long been limited by the lack of analytical methods. Herein, we report a novel circuit-switched transient photoelectric technique by which the migration dynamics specific to the ions in PSCs is closely inspected. By decoding the comprehensive information on the interaction between ions and charge carriers, we put forward a model of polarization-induced trap states, which can not only precisely account for the photoelectric behavior of PSCs but also be applicable to other photovoltaic systems with different device architectures, such as conventional silicon photovoltaic cells and dye-sensitized solar cells. Furthermore, we demonstrate the bifunctional role of the fullerene derivative in suppressing ion migration and accumulation, which provides an effective protocol of ion dynamics manipulation, besides the empirical strategy of defect passivation, toward high-efficiency and high-stability PSC devices.