Synthesis of highly efficient ZnAgInS-ZnInS/ZnS quantum dots and application for down-converted LEDs

摘要

This study introduces innovative exothermic reaction assisted synthetic method for highly efficient green emitting ZnAgInS-ZnInS/ZnS quantum dots (QDs) by simply adding excess amounts of Zn precursors (Zinc acetate dehydrate, ZAD) and application for down-converted light emitting diodes (LEDs). The ZnAgInS-ZnInS/ZnS QDs were synthesized using multi-step hot-injection method: Ag-In-S core growth, Zn-Ag-In-S core-alloy, Zn-In-S inner-shell, Zn-S outer-shelling. We compared low and high concentration of ZAD in order to make different reaction conditions during formation of ZnAgInS-ZnInS/ZnS QDs. We found when we use high concentration of ZAD, ZnInS inner-shell was successfully synthesized between ZnAgInS core-alloy and ZnS shell and photoluminescence quantum yield (PLQY) of QDs was increased by the exothermic reaction. The PLQY of QDs using high concentration of ZAD (86%) shows 1.43 times higher than that of QDs using low concentration of ZAD (60%) [1]. Dominant wavelength of QDs using high concentration of ZAD (511 nm) show blue shift about 15 nm compared to QDs using low concentration of ZAD (536 nm). Finally, we realized tri-packaged white LEDs using ZAIS green emitting QDs, ZCIS red emitting QDs and 445 nm blue emitting LED. The tri-package white LEDs show the luminous efficacy (LE) of 72 ～ 98 lm/W, color rendering index of 88 ～ 94 and high TM-30-2015 values from 2700 K to 10000 K of correlated color temperature (CCT). The highly efficient, broad band emitting ZnAgInS-ZnInS/ZnS QDs can be a good candidate for color converting materials in the field of LED lightings.