Promotion of solid-state lighting for ZnCdSe quantum dot modified-YAG-based white light-emitting diodes

In this study, the effect of quantum dot (QD) addition and photoluminescence quantum yield (PL QY) of QDs on the luminous efficacy and color rendering index (CRI) of white light-emitting diodes (LEDs) has been investigated. Two kinds of red-emitting materials, ZnCdSe QDs and commercial CaSiAlN₃:Eu²⁺ (nitride) phosphor, are mixed with commercial Y₃Al₅O₁₂:Ce³⁺ (YAG) phosphor as white LED materials. The as-prepared ZnCdSe QDs have a PL QY of about 44%, which drops to 29% after purification due to the removal of the surfactants. When the as-prepared QDs are used, both the CRI and luminous efficacy of the YAG/QDs-based white LED can be improved to meet the requirements of solid-state lighting (SSL), suggesting that the addition of QDs with high QY can overcome the trade-off property between CRI and luminous efficacy. Besides, the correlated color temperature (CCT) of this white LED can be tuned toward cold light by incorporating YAG with QDs, while it tunes toward warm light for a YAG/CaSiAlN₃-based white LED. This special phenomenon can be solely observed in QD-modified white LEDs. Moreover, the long term operation stability of QD-modified white LEDs is excellent.