Luminous efficacy enhancement of ultraviolet-excited white light-emitting diodes through multilayered phosphor-in-glass

To enhance the luminous efficacy of ultraviolet-excited white light-emitting diodes (WLEDs), a novel packaging structure that is based on a multilayered red, green, and blue (RGB) phosphor-in-glass (PiG) was proposed. The RGB PiG was prepared by screenprinting and low temperature sintering, and the effects of different configuration orders of RGB phosphor layers on the optical performance of WLEDs were studied. Compared with the conventional mixed-RGB PiG, the luminous efficacy of WLEDs packaged by the multilayered PiG with the order of R-G-B is increased by 8.2% at the driving current of 500 mA, and the corresponding correlated color temperature (CCT) and color rendering index (CRI) are 2984 K and 86.8, respectively. Moreover, the WLEDs packaged by multilayered G-R-B PiG yield the highest luminous efficacy of 27.19 lm/W at the expense of color quality, which is still an acceptable warm light, with a CCT of 3326 K and a CRI of 84.2.