One-pot synthesis of water-soluble Cu-In-Zn-S/ZnS core/shell quantum dots for efficient white light-emitting devices

I-III-VI quantum dots (QDs), as a new class of light-emitting materials, have aroused a great of attention for an impressive variety of applications. A facile one-pot approach was employed to synthesize highly luminescent Cu-In-Zn-S/ZnS (CIZS/ZnS) core/shell QDs. It was found that the CIZS/ZnS QDs prepared using sodium sulfide as sulfur source exhibited the strongest emission due to its highest chemical reactivity as compared to thiourea and thioacetamide. The combination of GSH content and pH value played a crucial role in the growth of ZnS shell, which was responsible for the bright emission of QDs. The surface defects of QDs could be effective passivated by GSH, which exhibited a significant improvement of emission intensity. The optimum pH value of 7 was also established due to the fact that the deprotonized sulfhydryl group of GSH molecule strongly coordinated with Zn2+ at neutral pH value. Moreover, the particle size and composition of the CIZS/ZnS QDs can be well adjusted by tuning the n(Zn)/n(CuInZn) ratios. The maximum quantum yield (QY) of CIZS/ZnS QDs increased from 5.95% to 26.12%, accompanying by the improvement of the radiative decay rate from 1.90 x 10(5) to 5.64 x 10(5) s(-1). Furthermore, a blue LED-pumped white light-emitting diode (WLED) device was realized by combining yellow-orange CIZS/ZnS QDs with green Lu3Al5O12:Ce3+ phosphor, achieving a luminous efficacy (LE) of 66.9 lm/W, and color rendering index (CRI) of 87.2, which demonstrated their great application potential in solidstate lighting field.