Exciton dynamics and random lasing in surface-passivated CdSe/CdSeS core/crown nanoplatelets

CdSe nanoplatelets (NPLs) are promising candidates for on-chip light sources, yet their performance is hindered by surface defects and inefficient optical gain. Herein, we demonstrate that CdSeS crown passivation significantly enhances the photophysical property of CdSe NPLs. Laser spectroscopy techniques reveal suppressed electronic and hole trapping at lateral surfaces, leading to a 4.2-fold increase in photoluminescence quantum yield and a shortened emission lifetime from 13.5 to 4.8 ns. In addition, amplified spontaneous emission is achieved under nanosecond pulse pumping, with thresholds of 0.75 to 0.16 mJ/cm² for CdSe and CdSe/CdSeS NPLs, respectively. By integrating CdSe/CdSeS NPLs with high-refractive-index SiO₂ scatters, coherent random lasing is realized at a threshold of 0.21 mJ/cm². These findings highlight the critical role of lateral surface passivation in optimizing optical gain and pave the way for low-cost, multifunctional nanophotonic devices.