Self-passivation of low-dimensional hybrid halide perovskites guided by structural characteristics and degradation kinetics†
Low-dimensional perovskite (LDP) holds great potential to deliver highly stable and efficient solar cells. However, a fundamental understanding of the structure, composition and degradation mechanism of the LDP material is required for further advancements. Here, we present an effective self-passivation strategy to concurrently enhance the efficiency and stability of the butylammonium (BA) based LDP solar cells. It is inspired and guided by the structural characteristics and degradation kinetics of the LDP film. We show that the BA-based LDP film possesses a unique crystal stacking pattern, containing highly oriented perovskite crystals of different layer thicknesses. We also uncover the divergent degradation behaviour of the LDP film under thermal stress and the unique disproportion degradation process under high-humidity conditions. Without introducing foreign compounds, the LDP film is passivated with a thin layer of the BA-based perovskite, which results in an exceptional power conversion efficiency of 17.0% and significantly enhanced device stability. These studies provide mechanistic insight into the structure and stability of the LDP material and offer guidelines for further device optimization.