Whispering-Gallery Mode Lasing in Perovskite Nanocrystals Chemically Bound to Silicon Dioxide Microspheres

Cesium lead halide perovskite nanocrystals exhibit high photoluminescence quantum efficiencies and tunability across the visible spectrum. This makes these crystals ideal candidates for solar panels, light-emitting diodes, lasers, and especially nanolasers. Due to the versatility of cation substitution in perovskite nanocrystals, they can be grown on amine-functionalized silicon dioxide nanoparticles, where the amine linker replaces the standard cation structure. Selectively growing luminescent nanocrystals on spherical silicon dioxide microspheres results in the opportunity to populate whispering-gallery modes in these spherical silica microspheres. In this case, the nanocrystal halide composition can be used to selectively tune the emission wavelength mode, and microsphere radius to tune the mode spacing. This silicon dioxide attachment also adds to the overall stability of the system. Through photoluminescence microscopy measurements, we show whispering gallery modes in individual perovskite-coated microspheres for CsPbBr₃ and CsPbI₃ nanocrystals on 9.2 μm diameter silica spheres and compare these to theoretically predicted optical modes. In CsPbBr₃, we provide evidence that these modes will lase under optical excitation, with a threshold of 750 μJ/cm². This study presents a novel system that, through optimization, could be a promising pathway to achieve facile and stable perovskite nanolasers.