Enhancing performance and stability of methylammonium lead iodide-based perovskite solar cells using single-crystal precursors

Methylammonium lead iodide (MAPbI3)–based perovskites are often regarded as unstable under light and heat; however, previous studies have not fully clarified the influence of residual lead iodide (PbI2) in thin films, which may have led to misinterpretations of their intrinsic stability. In this work, we propose a precursor-engineering strategy in which pre-synthesized MAPbI3 single crystals are re-dissolved to prepare coating solutions, thereby producing MAPbI3 films free of residual PbI2. Devices fabricated using this method achieved a power conversion efficiency (PCE) of 21.55%, significantly higher than the 18.61% obtained from control devices prepared using conventional precursor solutions. Moreover, the single crystal-derived devices exhibited remarkable long-term stability, retaining 98% of their initial efficiency after 1000 h of storage, whereas the control devices degraded to below 50% of their initial performance. Extensive characterizations of the single crystal-derived films revealed the degradation pathways induced by residual PbI2 in MAPbI3, confirming the superiority of this precursor design strategy. Importantly, these single crystal-derived films were further applied in mini-modules, achieving a PCE of 19.82% under 1-sun illumination and 39.66% under 6000 lux indoor light, underscoring their great potential for both outdoor and indoor photovoltaic applications. Methylammonium lead iodide perovskites are often deemed unstable, partly due to residual lead iodide in films. Here, the authors employ a precursor-engineering strategy using pre-synthesized methylammonium lead iodide single crystals to eliminate lead iodide, achieving enhanced power conversion efficiency and long-term stability, with significant implications for both outdoor and indoor photovoltaic applications.