Pseudohalide-Assisted Growth of Oriented Large Grains for High-Performance and Stable 2D Perovskite Solar Cells
Weichuan Zhang, Xianxin Wu, Jin Zhou, Bing Han, Xinfeng Liu, Yuan Zhang, Huiqiong Zhou
Abstract
Defects from grains and boundaries and the random phase distribution of 2D perovskite films generally cause nonradiative recombination and a reduction in carrier transport and stability. Herein, we find that pseudohalides can promote the growth of oriented large-grained 2D perovskite films. It is shown that pseudohalide additives can induce the aggregation and the assembly of 2D perovskites, effectively facilitate the assembly of random low-n phases into pure high-n phases, and enlarge the corresponding grain sizes of films. Concurrently, the phase distribution, crystalline quality, and carrier transport of perovskite films are also improved. As a result, the pseudohalide-optimized perovskite solar cells achieve remarkably improved PCEs of 18.72% and a negligible hysteresis. Importantly, the unencapsulated devices retain 100% of the initial efficiencies at persistent heating at 55 °C for 1180 h. After they were kept operating under the maximum power point (MPP) with continuous light illumination for about 1200 h, the devices showed only 13.3% efficiency degradation.