Modulated crystal growth enables efficient and stable perovskite solar cells in humid air

Abstract

The preparation of high-quality perovskite thin film in ambient air is crucial for achieving low-cost commercialization of perovskite solar cells (PSCs). However, it is difficult to obtain high-performance PSCs in high-humidity atmosphere because the perovskite films based on universal PbI2 lead source face the challenges of sluggish crystallization rate and high defect density. Herein, we report an effective additive method by incorporating volatile methylamine salts into the perovskite precursor solution to facilitate the fabrication of efficient and stable MAPbI3 PSCs in ambient air irrespective of the humidity. The addition of various compositional volatile methylamine salts (MACl, MASCN and MAAc) can modulate perovskite crystal growth in different degrees and improve the film quality with enhanced crystallinity and enlarged crystal grains. By comparison, the device with MACl additive achieves the highest power conversion efficiency (PCE) of 20.06% with almost no hysteresis owing to the significantly reduced defect state density in the film. Meanwhile, the device with MASCN addition delivers the second-best PCE (19.19%). Notably, the according perovskite film exhibits the strongest crystallinity that renders excellent photovoltaic performance even in ultrashort annealing duration or without annealing, indicating a prospect for the rapid upscaling of PSCs in ambient air. Furthermore, the PSCs without encapsulation show greatly enhanced air stability after the film growth modulation. Our work demonstrates the possibility of fabricating efficient and stable PSCs in humid atmosphere with PbI2 lead source and should be informative for industrial production in the future.