Photo-oxidation Induced Ultrafast Exciton Trapping and Photoluminescence Quenching in InP/ZnSe/ZnS Quantum Dots

InP/ZnSe/ZnS quantum dots (QDs) are promising candidates for advancing optoelectronic devices. However, their applications are limited by their low emission efficiency caused by photo-oxidation. In this study, we investigate the impact of photo-oxidation on the emission of InP/ZnSe/ZnS QDs at the ensemble and single-particle levels. Transient absorption spectroscopy reveals that photo-oxidation-induced ultrafast exciton trapping exhibits complex, multitime scale decay dynamics ranging from sub-nanoseconds to picoseconds, indicating that photo-oxidation-induced surface defects form high-density trap states with a broad, continuous energetic distribution. Single-QD spectroscopy shows that these trap states act as multiple nonradiative recombination centers that trigger band-edge carrier blinking. The extensive formation of photo-oxidation-induced defects results in photoluminescence (PL) quenching of single QDs. Monte Carlo simulations reproduce ultrafast exciton trapping-induced PL blinking and quenching and quantify the nonradiative recombination rates involved in these processes. These findings provide new insights into the photodegradation of InP QD materials and devices due to photo-oxidation and contribute to the design of novel antioxidant materials.