Probing Halide Perovskites' Degradation from the Macro- to the Nanoscale*

At the macroscale, we interrogate the individual and combined effects of extrinsic (humidity and oxygen) and intrinsic (light, bias, and temperature) stressors on halide perovskite materials by implementing photoluminescence (PL) under environmentally controlled conditions. We unravel the effects of distinct humidity levels on the charge carrier recombination in CsxFA1−xPb(IyBr1−y)3 perovskites through in situ PL, where we temporally and spectrally measure light emission within loops of critical relative humidity (rH) levels. Our results show that the Cs/Br ratio strongly affects the spectral stability of light emission hysteresis, as well as its extent. The photo-emission dynamics in metal halide perovskites with both I and Br is also interrogated by environmental PL, where we find that the presence of Br suppresses hysteresis. The isolated effects of both temperature and photon excitation energy are also investigated. At the nanoscale, we use advanced scanning probe microscopy methods to image the electrical behavior (photovoltage and photocurrent) of a series of perovskites. Here, we resolve ion motion in real-time.