Stimulated emission from microcrystalline CsPbBr3 films: Edge emission versus surface emission

Stimulated emission from microcrystalline CsPbBr3 films is measured under several excitation/detection geometries including the measurements of optical gain. Threshold for stimulated emission is strongly dependent on the geometries. In particular, in the stripe-shape excitation geometry, the edge luminescence is, unlike the case for the simultaneously measured surface luminescence, solely composed of stimulated emission even for a very low excitation fluence of a few kW/cm2, suggesting a very low threshold for the stimulated emission. The net optical gain at 77 K amounted to 130 cm-1 at 32 kW/cm2 excitation fluence and increased up to 300 cm-1 at 210 kW/cm2