Lattice expansion of hybrid perovskite inhibits halogen interstitial generation and enhances solar cell performance

One of the primary challenges for halide perovskite technology lies in its instability. Water is a ubiquitous environmental factor known to induce lattice expansion to perovskite. Lattice expansion has been proven beneficial to perovskite solar cell, but little is known about its role in lattice stability. In this work, we expose perovskites with pre-adsorbed water to vacuum and investigate the evolution of their structure. Our results show that vacuum induces water desorption and results in the removal of lattice expansion. This lattice recovery leads to an increasing lattice distortion, ultimately favoring the formation of halogen trimers in the case of hybrid perovskites. We thus find that the lack of lattice expansion facilitates the generation of defects detrimental to hybrid perovskite devices. Here, we report the crucial role of lattice expansion in preventing degradation of hybrid halide perovskites, which is of critical importance in the context of solar cell fabrication.