High intensity photoluminescence of microcrystalline CsPbBr3 films: Evidence for enhanced stimulated emission at room temperature

Photoluminescence of microcrystalline CsPbBr3 films grown from the amorphous phase shows stimulated emission not only at cryogenic temperature but also at room temperature, in great contrast to the case for bulk CsPbBr3 single crystals, where no stimulated emission occurs even at 4.2 K. This is the first demonstration of room temperature stimulated emission from metal halide compounds.The stimulated emission is so strong that single-path-light-amplification stimulated emission across the film thickness is observed at relatively low threshold excitation intensities of ∼50 kW cm−2 at 77 K and ∼100 kW cm−2 at 295 K suggesting a large optical gain. The physical origin of the stimulated emission is assigned as due to free exciton-free exciton inelastic collision. The large-gain mechanism is attributable to giant oscillator strength effect characteristic of excitonic superradiance recently reported in this issue.