Improvement of luminescence properties of surface-passivated mixed-halide perovskites with CdSe/ZnS quantum dots

CdSe/ZnS core-shell quantum dots (QDs) have been employed to enhance the optical properties of perovskite (PS). We investigated the luminescence properties of surface-passivated mixed halide perovskite (CH₃NH₃PbI₂Br) using photoluminescence (PL) and time-resolved PL spectroscopy. The integrated PL intensity and PL decay time of the QD/PS hybrid structure increased compared to those of the bare PS films, owing to charge transfer (CT) from the CdSe/ZnS QDs to the PS and reduced charge traps. The CT efficiency increased from ~7 to 63% for the QD/PS hybrid structure when the core diameter of the QDs decreased from 6.5 to 2.7 nm, respectively, which can be explained by the enhancement in the CT rate due to the control of energy level alignment of QDs. A shorter radiative lifetime was obtained in the QD/PS hybrid structures as compared to the bare PS film, which is attributed to the screening effects of the Rashba splitting and internal electric field due to the CT. These results allow us to understand fundamental mechanisms such as CT from QDs to PS as a function of the size of the QDs