White LED Packaging with Layered Encapsulation of Quantum Dots and Optical Properties

The preparation method of encapsulating paste containing YAG phosphor and red quantum dot (QD) in silicone resin and the structure of phosphor layers were studied from the view point of improving both the efficiency and color rendering index (CRI) of the phosphor converted white LED (pcWLED). The addition of red phosphor or red QD in addition to the YAG phosphor could increase CRI of the pcWLED, but the efficiency was decreased. The pcWLED packaged with the encapsulant where the red QD was mixed in advance with the part of the silicone resin and mixed again with the YAG phosphor dispersed the remaining in silicone resin exhibited higher CRI and efficiency than the one packaged with one pot mixture of YAG and red QDs. The pcWLEDs made by silicone encapsulant with YAG phosphor and red QD at the ratio of YAG: QD = 5.0:0.5wt% exhibited that both efficiency and color rendering index could be increased at same time by adopting YAG phosphor and QD encapsulation in a layer-by-layer structure on top of InGaN LED chip.