Emission tunable CdZnS/ZnSe core/shell quantum dots for white light emitting diodes

CdZnS based quantum dots are emerging as promising light sources for light-emitting diodes (LEDs). Although current CdZnS/ZnS quantum dots exhibit good performances in ultraviolet (UV) or blue light, it is hard to achieve efficient red or green emission owing to the intrinsic limitation of the core-shell system, in which ZnS shell only serves as passivation layer to enhance the luminescence. Instead, we introduce a versatile ZnSe shell with a moderate band gap onto the CdZnS core. Evidences show that ZnSe, on one hand, can passivate the core surface which leads to bright emissions. On the other hand, ZnSe shell is essential in tuning the emission to the visible region. The as-prepared CdZnS/ZnSe quantum dots show good color tunability, which is ranging from deep-blue to red. Bright white LEDs are fabricated by appropriately integrating a mixture of red, yellow and green emissive CdZnS/ZnSe quantum dots on the blue-emitting GaN LED chip. The fabricated white quantum dot-based LED demonstrates good luminescent and visual performance with a color rendering index of 85.2 and a correlated color temperature of 4072 K. These results suggest that CdZnS/ZnSe quantum dots hold great promise for the next-generation white light source.