Stable FAPbI₃ hydrate structure by kinetics negotiation for solar cells

The instability of formamidinium lead iodide (FAPbI₃) perovskite has limited its application in renewable energy development, despite the highest power conversion efficiency (PCE) it exhibited. A step forward has been achieved here by negotiating the hydration kinetics via adjusting the moisture partial pressure. The stable hydrate was restricted to precipitating only in the area surrounding the grain boundary under the influence of the moisture partial pressure, avoiding the large strain created by the complete hydration reaction, which preserved the condensed morphology of the perovskite film. The PCE of such a device was thus enhanced to more than 10%, as opposed to the value of 0.32% in previous results, with comparable stability to the pure moisture-stable hydrate-based film, which not only provided a promising solution to the lifetime problem, but also provided fresh inspiration for thin film growth kinetics.