Healing aged metal halide perovskite toward robust optoelectronic devices: Mechanisms, strategies, and perspectives

Owing to their low cost, high efficiency, property tunability, and flexibility, metal halide perovskites (MHPs) show great promise in next-generation optoelectronics, including perovskite-based solar cells, photodetectors, and light-emitting diodes. However, the long-term stability of these perovskite-based optoelectronic devices (PODs) is far from satisfactory, and their poor stability greatly hinders their future commercialization in real-world applications. Essentially speaking, the performance loss of PODs is due to the structural change of the core MHP layer either physically or chemically. Fortunately, these physicochemical changes are found to be reversible under controlled conditions, which offers a critical opportunity to address the long-term stability problem of PODs. In this review, we comprehensively summarize the current understanding of performance loss and the corresponding advanced healing strategies for PODs. First, four typical pathways of MHP aging that cause the performance loss of PODs are discussed, including phase transitions, phase segregation, photoactivated trap states, and structural decomposition of MHPs. Then, state-of-the-art strategies for promoting the healing of MHPs and the performance recovery of PODs are introduced. Finally, the current challenges and future prospects in this exciting research direction are discussed. This review highlights the significance of developing healable PODs, which is expected to enhance the robustness of PODs and promote their large-scale industrialization in the near future.