Quaternary Alloyed Quantum Dots with a Wide-Ranging Tunable Emission for High Color-Rendering White Light-Emitting Diodes

Quaternary alloyed quantum dots (QDs) Ag-Zn-In-S(AZIS)/ZnS were prepared by using of heating-up method for the synthesis of AZIS cores followed by a hot-injection method for the shelling of ZnS. By regulating the Ag:Zn:In ratio, the peak emissions of the resulted AZIS/ZnS QDs exhibited an unreported wide ranging tunable emission from 475 nm to 645 nm. With the increasing silver components, redshift in the photoluminescence spectrum was observed. White light-emitting diodes (WLEDs) were fabricated successfully by employing the yellow-green emission AZIS/ZnS QDs and the combination of the green and the red emission ones as color converters respectively. These devices showed satisfied luminescent properties including a highest color-rending index of 88 accompanied by a corelated color temperature of 3260 K. However, AZIS/ZnS QDs integrated on the chips exhibited large redshift compared to their solution states. This redshift was suppressed remarkably by coating the as synthesized AZIS/ZnS QDs with a silica shell using the hydrolysis of tetramethoxysilane (TMOS). The WLEDs based on silica-coated AZIS/ZnS QDs showed an ultrahigh CRI of 96.3 accompanied by a CCT of 3653 K and good resistance to the invasion of room temperature and humidity after placed under room environment for 11 months. Possessing no heavy metal elements and satisfied luminescent properties combined with good resistance to the invasion of room temperature and humidity in devices make AZIS/ZnS QDs be expected to play a critical role in various applications of lighting.