Photoluminescence and stimulated emission from microcrystallineCsPbCl3films prepared by amorphous-to-crystalline transformation

Abstract

Highly excited photoluminescence of $\mathrm{Cs}\mathrm{Pb}{\mathrm{Cl}}_{3}$, which is known to be one of the most photoluminescent semiconductors, has been measured for thin films prepared by crystallization from the amorphous phase into microcrystalline/polycrystalline states. With the increase of excitation intensity, the microcrystalline state shows successive jumps of the dominant emission band, from a free-exciton band to its phonon replica and finally to a lowest-energy band originating from exciton-exciton inelastic collision. For the exciton-exciton porcess stimulated emission occurs at very low threshold excitation intensities of the order of $10\phantom{\rule{0.3em}{0ex}}\mathrm{kW}∕{\mathrm{cm}}^{2}$ at $77\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. At higher excitation intensities above $50\phantom{\rule{0.3em}{0ex}}\mathrm{kW}∕{\mathrm{cm}}^{2}$, single-path-light-amplification stimulated emission across the film thickness is observed suggesting a very large optical gain. The large-gain mechanism is attributable to giant oscillator strength effect characteristic of excitonic superradiance recently reported for films prepared in the same way.