A stress relaxation strategy for preparing high-quality organic–inorganic perovskite thin films via a vapor–solid reaction

Abstract

A post-vapor treatment was developed to alleviate compressive strains in perovskite thin films grown by vapor–solid reaction. Perovskite solar cells based on these films achieved an improved power conversion efficiency of over 22%.

Abstract

Perovskite solar cells (PSCs) prepared through vapor–solid reactions exhibit promising potential for commercial application due to their scalability and lack of organic solvents. Unlike solution-based drying processes, the vapor–solid reaction causes the perovskite thin film to undergo volume expansion rather than shrinkage. Consequently, the residual stress within the vapor-processed perovskite thin film differs significantly from that within the solution-processed film. In this study, we investigate the characteristics of residual stress in films obtained via vapor–solid reactions. Building upon this, we develop a vapor-annealing strategy to alleviate the residual stress. Through post-treatment of the film with organic ammonium salt vapor, we successfully obtained high-quality perovskite thin films devoid of residual stress. As a result, the optimized PSCs achieve an impressive champion power conversion efficiency (PCE) of 22.06%. Furthermore, the unencapsulated device maintains 97% of its initial PCE after 3600 h storage under ambient conditions, and the encapsulated device 84% of its initial PCE after a 720 h thermal test at 85 °C. These results underscore the significance of eliminating residual stress in ensuring the long-term stability of high-efficiency PSCs.