Rubidium Induced Phase Regulation for High-Performance Quasi-2D Perovskite Solar Cells
Bo Xu, Rong Yang, Yu Chen, Jinfei Zhou, Wen Liang Tan, Pinghui Yang, Fengwei Wang, Xiliu Wang, Wenbo Liu, Xuan Gao, Jingwei Li, Daliang Zhang, Christopher R. McNeill, Renzhi Li, Wei Huang, Jianpu Wang
Abstract
Quasi-two-dimensional (2D) perovskites are notable for their diverse formulations and environmental stability. However, solution-processed quasi-2D perovskites often exhibit inherent multiple-quantum-well structures with broad phase distributions, limiting their efficiency in photovoltaic applications. Here, we demonstrate that incorporating rubidium ions effectively narrows the phase distribution in quasi-2D perovskite by accelerating the formation of the n = 1 2D perovskite phase during the initial crystallization stage. This leads to a decrease in the remaining free organic spacer cations, which in turn limits the transition to medium- n phases ( n = 3, 4) and promotes the formation of high-quality 3D-like or large- n perovskites, ultimately enhancing charge transport of quasi-2D perovskite. Consequently, we achieve quasi-2D perovskite solar cells with a champion power conversion efficiency of 21.9%. Furthermore, the thermal stability of the unencapsulated devices containing rubidium is significantly improved, with the T80 lifetime under continuous 60 °C stress increasing from 1150 to over 3000 h.