Detection of A Shifting Bromine Concentration in Hybrid Perovskites by X-ray Fluorescence Microscopy

Hybrid perovskite materials are promising for application as the active layers in solar cells due to their excellent optoelectronic properties. Improved understanding of the origins of hysteresis in perovskite materials must be established to overcome barriers to commercialization. In this study, we use a lateral device geometry to bias a methylammonium lead bromide thin film single crystal. Upon biasing, the halide concentration varies laterally within the crystal, as observed by means of nondestructive synchrotron-based nanoprobe X-ray fluorescence (Nano-XRF). The direct observation of a partially reversible bromine re-distribution under bias is revealed experimentally. The origins of device hysteresis and switchable effects can be partially explained by the local elemental information available from Nano-XRF.