Light Soaking Effects in Perovskite Solar Cells: Mechanism, Impacts, and Elimination

Perovskites solar cells (PSCs) have been recognized as one of the most prospective photovoltaic technologies for their combined properties of simple fabrication process, low material cost, and remarkable power conversion efficiencies of over 25%. However, the instability and poor reliability of PSCs remain the major obstacles to their practical applications. Specifically, light-soaking effect (LSE), which refers to the fluctuations of photovoltaic parameters under light exposure, represents a critical factor limiting the accuracy and stability of device power output. However, great challenges still remain in understanding and modulating the LSE in PSCs. In this review, we discuss different transient behaviors associated with LSE, and summarize various physical mechanisms (such as light-induced ions migration, trap defect passivation, lattice expansion, and charge carrier accumulation) behind the LSE together with their impacts to the device performance. Moreover, we systematically review the recent advances in developing effective approaches and strategies to mitigate or eliminate the LSE in PSCs, including interfacial modification, material doping, and surface passivation. Finally, a perspective and outlook toward LSE-free PSCs are further provided. This review offers a deeper opinion of the LSE physics with further guidance on ways to optimize the photostability of PSCs.