Atomistic origins of CH_3NH_3Pbl_3 degradation to Pbl_2 in vacuum

摘要

We study the mechanisms of CH_3NH_3Pbl_3 degradation and its transformation to Pbl_2 by means of X-ray diffraction and the density functional theory. The experimental analysis shows that the material can degrade in both air and vacuum conditions, with humidity and temperature-annealing strongly accelerating such process. Based on ab initio calculations, we argue that even in the absence of humidity, a decomposition of the perovskite structure can take place through the statistical formation of molecular defects with a non-ionic character, whose volatility at surfaces should break the thermodynamic defect equilibria. We finally discuss the strategies that can limit such phenomenon and subsequently prolong the lifetime of the material.