Suppressing the Cation Exchange at the Core/Shell Interface of InP Quantum Dots by a Selenium Shielding Layer Enables Efficient Green Light-Emitting Diodes

Indium phosphide (InP) quantum dots (QDs) have demonstrated great potential for light-emitting diode (LED) application because of their excellent optical properties and nontoxicity. However, the over performance of InP QDs still lags behind that of CdSe QDs, and one of main reasons is that the Zn traps in InP lattices can be formed through the cation exchange in the ZnSe shell growth process. Herein, we realized highly luminescent InP/ZnSe/ZnS QDs by constructing Se-rich shielding layers on the surfaces of InP cores, which simultaneously protect the InP cores from the invasion of Zn2+ into InP lattices and facilitate the ZnSe shell growth via the reaction between Zn2+ precursors and Se2- shielding layers. The as-synthesized green InP/ZnSe/ZnS QDs had a high photoluminescence quantum yield (PLQY) of up to 87%. The fabricated QLEDs present a peak external quantum efficiency of 6.2% with an improved efficiency roll-off at high luminance, which is 2 times higher than that of control devices.