Degradation of Perovskite Photovoltaics Manifested in the Cross-Sectional Potential Profile Studied by Quantitative Kelvin Probe Force Microscopy

Kelvin probe force microscopy has been employed to monitor the cross-sectional potential profile in lead-halide perovskite photovoltaic cells. From systematic investigations on many devices under varying bias voltage and light illumination conditions, we are able to deduce quantitative profile features with low noise that allows us to compare the local electronic properties in the working devices against numerical calculations. We applied the technique to devices before and after degradation. Through the profile change before and after, we located the degraded components and inferred the source of the loss of the performance.