Hot Electrons and Coherent Photons from Strongly Quantum-Confined Lead Halide Perovskite Nanocrystals and Their Assemblies

Imposing strong quantum confinement in lead halide perovskite nanocrystals enhances the electronic interactions between charge carriers and dopants within each nanocrystal and promotes the delocalization of the exciton wavefunction in the closely packed assemblies of these nanocrystals. We investigated: (i) the generation of hot electrons via exciton-to-hot electron upconversion in strongly quantum-confined cesium lead bromide (CsPbBr₃) nanocrystals doped with Mn²⁺ and (ii) the coherent photon emission from the superlattices of CsPbBr₃ quantum dots, where strong quantum confinement plays a significant role. The enhanced exciton-dopant interaction in the more strongly confined CsPbBr₃ nanocrystals proved beneficial for hot electron upconversion and allowed for the utilization of the long-lived dark exciton in such processes at low temperatures. The closely-packed QD superlattice of the strongly confined CsPbBr3 quantum dots, which are 4 nm in size, exhibited superfluorescence from excitons delocalized across many quantum dots, rather than from an ensemble of electronically non-coupled quantum dots, especially as the temperature decreased. Positioning the superlattice within the micro-ring resonance cavity further amplified the coherent emission from the interconnected quantum dots.