Highly Efficient Green ZnAgInS/ZnInS/ZnS QDs by a Strong Exothermic Reaction for Down-Converted Green and Tripackage White LEDs

Highly efficient bright green-emitting ZnAgInS (ZAIS)/ZnInS (ZIS)/ZnS alloy core/inner-shell/shell quantum dots (QDs) are synthesized using a multistep hot injection method with a highly concentrated zinc acetate dihydrate precursor. ZAIS/ZIS/ZnS QD growth is realized via five sequential steps: a core growth process, a two-step alloying-shelling process, and a two-step shelling process. To enhance the photoluminescence quantum yield (PLQY), a ZIS inner-shell is synthesized and added with a band gap located between the ZAIS alloy-core and ZnS shell using a strong exothermic reaction. The synthesized ZAIS/ZIS/ZnS QDs shows a high PLQY of 87% with peak wavelength of 501 nm. Tripackage white down-converted light-emitting diodes (DC-LEDs) are realized using an InGaN blue (B) LED, a green (G) ZAIS/ZIS/ZS QD-based DC-LED, and a red (R) ZnCuInS/ZnS QD-based DC-LED with correlated color temperature from 2700 to 10 000 K. The red, green, and blue tripackage white DC-LEDs exhibit high luminous efficacy of 72 lm W-1 and excellent color qualities (color rendering index (CRI, Ra) = 95 and the special CRI for red (R9) = 93) at 2700 K.