Trace Water in Lead Iodide Affecting Perovskite Crystal Nucleation Limits The Performance of Perovskite Solar Cells.

The experimental replicability of highly efficient perovskite solar cells (PSCs) has been a persistent challenge faced by laboratories worldwide. Although trace impurities in raw materials can impact the experimental reproducibility of high-performance PSCs, the in situ study of how trace impurities affect perovskite film growth has never been investigated. In our study, we shed light on the impact of inevitable water contamination in lead iodide (PbI 2 ) on the replicability of device performance, mainly depending on the synthesis methods of PbI 2 . Through synchrotron-based structure characterization, we uncover that even slight additions of water to PbI 2 accelerate the crystallization process in the perovskite layer during annealing. However, this accelerated crystallization also results in an imbalance of charge-carrier mobilities, leading to a degradation in device performance and reduced longevity of the solar cells. We also find that anhydrous PbI 2 promotes a homogenous nucleation process and improves perovskite film growth. Finally, our PSCs achieve a remarkable certified power conversion efficiency of 24.3%. This breakthrough demonstrates the significance of understanding and precisely managing the water content in PbI 2 to ensure the experimental replicability of high-efficiency PSCs. This article is protected by copyright. All rights reserved.