Inner Shell Influence on the Optical Properties of InP/ZnSeS/ZnS Quantum Dots

The design of core/shell InP-based quantum dots (QDs) can not only retain the low toxicity of the InP core but also significantly enhance its stability, making it suitable for various applications. However, the influence of the shell layer on the optical properties of InP QDs is still not clear, which is not conducive to the optimization of optical properties and application exploration. Here, the optical properties of two kinds of InP-based QDs, i.e., InP/ZnS and InP/ZnSeS/ZnS, have been comparatively investigated. Compared with the former, the latter possesses improved photoluminescence quantum yield and weaker defect state emission. Due to the introduction of the inner ZnSeS shell, the surface states of the InP core can be reduced and a quasi-II electronic structure is formed, which is beneficial for suppressing the blinking effect. In addition, compared with InP/ZnS QDs, InP/ZnSeS/ZnS QDs exhibit higher two- and three-photon brightness in the wavelength range from 700 to 1500 nm. Our work reveals the importance of the inner ZnSeS shell for the optimization of the optical properties of InP-based QDs.