Residual Nanoscale Strain in Cesium Lead Bromide Perovskite Reduces Stability and Shifts Local Luminescence

Using scanning X-ray diffraction microscopy, we investigate the relationship between residual strains from crystal growth in CsPbBr 3 thin-film crystals, their stability, and local photoluminescence (PL). We find that out-of-plane compressive strain that arises from cooldown from crystallization is detrimental to material stability under X-ray irradiation. We also find that the optical PL red-shifts as a result of the out-of-plane compressive strain. The sensitivity of the PL peak position to strain suggests possible applications such as stress-sensitive sensors. Mosaicity, the formation of small misorientations in neighboring crystalline domains we observe in some CsPbBr 3 single crystals, indicates the significant variations in the crystal quality that can occur even in single-crystal halide perovskites. The nanodiffraction results suggest that reducing local strains is a necessary path to enhance the stability of perovskite optoelectronic materials and devices from light-emitting diodes to high-energy detectors.