Correlating Intensity Fluctuations and Lifetime Distributions Reveals Surface Chemistry Effects on Photoluminescence...

Perovskite quantum dots (PQDs) exhibit pronounced photoluminescence (PL) intensity and lifetime fluctuations at the single-particle level that arise from competition between radiative and trap-mediated nonradiative exciton recombination pathways. Although surface treatments are widely employed to mitigate these fluctuations, the mechanistic relationship among surface chemistry, trap state energetics, and exciton dynamics remains poorly understood. Here, we present an integrative and comparative study that correlates PL intensity fluctuation with fluorescence lifetime-intensity distribution (FLID) patterns in single CsPbBr₃ QDs. This work analyzes PQDs capped with conventional ligands, a zwitterionic ligand, or treated postsynthetically with excess bromide. Three distinct PL intensity fluctuation behaviors, blinking, flickering, and minimal fluctuations, were observed, with relative populations that strongly depend on surface passivation. FLID analysis reveals that these behaviors originate from nonradiative recombination pathways involving trap states of various energies. By correlating the observed FLID patterns with density functional theory calculations, we demonstrate how ligand binding strength and binding mode influence the accessibility of specific surface defect states. Strong, multidentate binding of the zwitterionic ligand enhances surface stability and suppresses both blinking and flickering by limiting dynamic ligand desorption and trap formation. In contrast, excess bromide treatment selectively alters shallow trap-mediated pathways, modifying PL fluctuation characteristics. These results provide an atomistic framework for understanding how surface chemistry and trap states evolve under different passivation methods and offer insight into strategies for improving the stability and optical performance of PQDs.