An alloyed mid-shell strategy assisted realization of thick-shell violet-blue ZnSe/ZnSexS1-x/ZnS quantum dots with high color purity

Abstract

Environmentally friendly zinc selenide (ZnSe) based core/shell quantum dots (QDs) are promising emitting materials for special light sources and displays. However, ZnSe-based core/shell QDs with violet-blue emission that simultaneously possess thick shells and narrow emission linewidths are still challenging thus far. We herein use a gradient ZnSexS1-x/ZnS shell strategy to target this goal. The ZnSexS1-x mid shell helps the lattice strain relaxation during the growth, whereas the wide bandgap ZnS outer shell benefits the optical properties by passivating the emitting cores and improving the quantum confinement effect. These ZnSe core QDs show a unity zinc blende structure and high crystallinity. The optimized ZnSe/ZnSexS1-x/ZnS QDs exhibit tunable emission wavelengths (415–445 nm), narrow photoluminescence linewidths (10.2–14.2 nm), thick shells (>3.9 nm), and high photoluminescence quantum yields (>50%). We postulate that these excellent features are due to the use of alloyed ZnSexS1-x layer at the core/shell interfaces. This study provides a feasible idea for the development of blue ZnSe-based QDs with perfect emitting properties.