Correlating Delayed Emission, Blinking Mechanism, and the Quantum-Confined Stark Effect in Single Quantum Dots

Delayed emission, a long-lived nonexponential photoluminescence tail, is widely observed in quantum dots (QDs), but its microscopic origin and relationship with blinking and the quantum-confined Stark effect (QCSE) remain unclear. Here, we combine single-QD spectroscopy, time-gated photon analysis, and Monte Carlo simulations across CsPbX3 perovskite, CdSe-based, and InP-based QDs to identify a potential mechanism. Delayed emission correlates with band-edge carrier-trapping blinking, but is weak in QDs dominated by trion-mediated Auger blinking, suggesting delayed emission is not universally tied to charge-separated states. Delayed photons originate from nanosecond-scale carrier trapping and detrapping at nonradiative recombination centers: transiently trapped carriers return to the band edge and recombine radiatively. Time-gated analysis distinguishes this process from QCSE-driven intensity-lifetime fluctuations on slower blinking time scales. Furthermore, we demonstrate that delayed photons compromise the single-photon purity at a fixed excitation repetition rate. These findings establish a general framework of delayed emission in QDs.