The effect of surface/interface defects on multiexciton recombination is studied with CdZnSeS/ZnS alloy core/ shell quantum dots (QDs) with different shell thicknesses. Through pump-power-related time-resolved photoluminescence/ amplified-spontaneous-emission (ASE) spectra and statistical analysis of single-dot fluorescence, it is indicated that with the epitaxial growth of the ZnS shell, the multiexciton property of the QDs can be improved due to surface passivation, but with further shell growth, interface defects caused by stress accumulation will result in deterioration. The QDs with three monolayers ZnS shell show the best performance with a biexciton quantum yield of 11.6%, biexciton lifetime of ∼360 ps, and ASE threshold of only 118 μJ cm −2 , with which a vertical cavity surface-emitting laser is fabricated. Our experimental results highlight the importance of surface/interfacial defects to the application of QDs on laser devices.
Room‐temperature exciton‐polariton Bose‐Einstein condensation (BEC), a phase transition to single quantum state with strong nonlinearity, provides a new strategy for coherent light sources and ultralow threshold optic switches. In this work, colloidal CdSe/CdS 2D nanoplatelets are embedded into a microcavity, and exciton‐polariton BEC is realized with an ultralow threshold of 0.5 µJ cm–2 at room temperature. The superlinear power‐dependent emission, macroscopic occupation of the ground state, strong blueshift and broadening of the emission peak, and long‐range coherence strongly confirm the realization of the polariton laser. This work suggests considerable prospects for colloidal nanoplatelets in low‐cost, high‐performance polariton devices, and coherent light sources.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.