Stable intermediate phase regulation for high-performance and scalable perovskite solar cells

Abstract Large-area perovskite solar cell modules efficiency remains lower than small-area devices, perovskite crystallization between small and large areas difference could be one reason. Previously, diluted solution was often used to reduce viscosity to achieve uniform perovskite thin films, but this approach could narrow the crystallization window and leave insufficient time for controlled crystal growth. Meanwhile, insufficient solute supply often results in interrupted material availability for grain growth, leading to the formation of excessive small crystal nuclei and thus poor thin-film quality. Here, we developed a strategy that use a bi-functional group additive to stabilize the δ-FAPbI 3 intermediate phase, which delays the direct and rapid conversion of lead iodide into α-FAPbI 3 during large-area perovskite film growth. Based on this strategy, the efficiencies of perovskite modules with aperture areas of 14.6, 70.5, and 285.6 cm 2 developed in this work are 24.4% (certified steady-state efficiency: 24.4%), 23.1%, and 22.4%, respectively. The efficiency loss per order-of-magnitude increase in area was reduced from 2.0% to 1.3%, which is approaching the state of the art of traditional thin-film CdTe solar cells (0.8%). In addition, the large-area module (155 cm 2 ) retained 86% of its initial efficiency after 1053 h of maximum power point (MPP) tracking.