Nanoscale Characterization of Halide Perovskite Phase Stability with Scanning Electron Microscopy

Abstract

In light of the high potential of halide perovskites for solar energy applications, continued focus has been placed on long-term stability of these materials. Significant work has focused on the phase instabilities of both cesium- and formamidinium-based halide perovskites since the photoactive perovskite phases of both materials have intrinsic and extrinsic instabilities. Scanning electron microscopy (SEM) is routinely used to investigate the morphology and structure of halide perovskite materials. In this study, SEM techniques are extended to an investigation of material phase instability. This allows for high-resolution observations of the change from the perovskite to non-perovskite phase with insight into phase nucleation and growth. When combining secondary electron imaging with backscatter electron imaging, we show the facile growth of the non-perovskite phase across grain boundaries and a decrease in crystallinity after the phase transition. This work yields a closer look at this important phase transition and provides a roadmap for imaging materials with similar property differences between crystal phases.