Sequential Growth of InP Quantum Dots and Coordination between Interfacial Heterovalency and Shell Confinement: Implication for Light-Emitting Devices

As a kind of luminescent nanomaterial, InP quantum dots (QDs) have been regarded as one of the most potential nontoxic alternatives for cadmium-based QDs in the light-emitting devices, and much progress has been obtained recently. However, their growth kinetics remains not fully revealed yet, and the effects of the shelling process on as-synthesized InP cores have been rarely investigated. Herein, the growth kinetics of InP QDs is investigated via the convenient method of varying halide ions, and their sequential growth is proposed according to the discontinuous evolution of their first exciton absorption peaks, especially the observed typical positions, which is different from the reported continuous evolution previously and means that the specific sized InP cores appeared during the growth stage. Moreover, the impacts of ZnS are analyzed from the quantum confinement effect of ZnS on InP cores with different sizes and interfacial heterovalent bonds. The coordination between these two aspects decides the final positions of the first exciton absorption peaks of InP/ZnS QDs. Compared with the positions of the first exciton absorption peaks of bare InP QDs, insufficient confinement of the ZnS shell to small InP cores causes the red-shift, but the heterovalent bonds at the interface cause the blue-shift. Furthermore, the emissions of final InP/ZnS QDs are influenced, and the emission from 484 to 578 nm is obtained via this facile synthetic protocol. It is thought that this study can reveal the growth of InP QDs and provide guidance to design rational InP-based QDs with desired emission and high performance, contributing to the fabrication of efficient light-emitting devices.