Pure-blue emissive ZnSe/Cd_xZn_1−xS/ZnS quantum dots with type-II core-shell structure for display application

Blue emissive quantum dots are key materials in fabricating quantum-dot light-emitting diodes for display applications. Up to date, most of the previous blue emissive quantum dots are based on quantum dots with type-I core-shell structure. In this work, we report pure-blue emissive ZnSe/Cd_xZn_1−xS/ZnS quantum dots with type-II core-shell structure, which show high photoluminescence quantum yield over 90%. The type-II structure was investigated by applying time-resolved photoluminescence and transient absorption measurements, illustrating the extended photoluminescence decay lifetime of ZnSe/Cd_xZn_1−xS quantum dots as well as the transition of bleaching peak from the valence band of ZnSe to the conduction band of CdZnS. We further fabricated ZnSe/Cd_xZn_1−xS/ZnS quantum dots based electroluminescence devices, achieving a maximum external quantum efficiency of 6.7% and a maximum luminance of 39,766 cd·m⁻².