Single-step ZnS shell passivation enables stable carrier dynamics and enhanced emission in InP quantum dots

Indium phosphide (InP) quantum dots (QDs) are promising, less-toxic alternatives to Cd-based nanocrystals, but achieving stable emission through simple, experimentally accessible passivation strategies remains challenging due to trap-assisted non-radiative recombination. Here, we demonstrate that direct single-step ZnS shell growth on InP QDs provides an effective route to control carrier recombination dynamics without halide etching or intermediate ZnSe/ZnSeS layers. Structural characterization by XRD and HRTEM confirms the formation of crystalline core–shell nanostructures, while UV–Vis absorption and photoluminescence (PL) measurements reveal enhanced band-edge emission and improved spectral definition after passivation. Temperature-dependent time-resolved photoluminescence (TRPL) measurements in the 10–290 K range show longer average lifetimes and reduced thermal quenching in ZnS-coated QDs. Analysis using an empirical thermal activation model together with biexponential lifetime fitting indicates a reduced contribution of thermally activated trap states and a more favorable balance between radiative and non-radiative recombination pathways. These results establish single-step ZnS passivation as a practical strategy to stabilize emission and engineer carrier dynamics in InP-based quantum dots, providing an experimentally accessible approach for optoelectronic and bioimaging applications. • Single-step ZnS shell growth enables control of carrier recombination pathways in InP QDs. • ZnS passivation suppresses trap-assisted recombination and stabilizes emission across temperature. • Temperature-dependent TRPL reveals reduced thermal quenching and stabilized recombination balance. • Passivated QDs show narrower emission (13–23 nm) and up to 3× longer carrier lifetimes. • This work provides an experimentally accessible route to thermally stable InP quantum dots.