Shape‐Dependent Kinetics of Halide Vacancy Filling in Organolead Halide Perovskites

Abstract Halide perovskites show high photoluminescence quantum yields and tunable bandgap. While perovskites’ optical properties significantly degrade due to the ionic and electronic defects, a correlation among their structure, size, defects, and degradation rate remains concealed. The authors report the crystal shape‐ and halide vacancy‐dependent stability of methylammonium lead bromide single crystals. The vacancies are filled in the cubic‐, plate‐, and rod‐shaped crystals by the halide‐soaking and light‐soaking processes. The differences in the stability, photoluminescence intensity, lifetime, and vacancy filling rates in these geometrical shapes derive from their specific surface‐to‐volume ratios. The shape‐dependent vacancy filling helps to correlate the electron microscope images, elemental compositions, and the photoluminescence intensity and lifetime.