Phosphor Glass-Coated Sapphire With Moth-Eye Microstructures for Ultraviolet-Excited White Light-Emitting Diodes

In this paper, we used a moth-eye structured phosphor-in-glass (PiG) to enhance the luminous efficiency (LE) of ultraviolet (UV)-excited white light-emitting diodes (WLEDs). The proposed PiG was prepared by printing and sintering a red/green phosphor film on a moth-eye array-structured (MAS) sapphire plate. Then, this PiG was directly bonded on a UV-LED flip-chip to achieve an ultracompact and reliable WLED device. The luminescent performances of the WLEDs were adjusted by managing the thickness of PiG film from 20 to 107 μm. When the film thickness is 20 μm, the LE of the WLED with the MAS PiG is increased by 20.96% compared to the WLED with the flat PiG, and the correlated color temperature (CCT) is 4712 K and the color rendering index (CRI) is 78.7. It is chiefly attributed to a significant reduction of total internal reflection at the PiG and air interface benefit from using MAS. In addition, the light intensity of the MAS PiG from -80° to 80° is higher than that of the reference PiG. For the reference PiG, the electric field amplitude is strong in the air at θ
_s
= 0°, and then becomes weak at the critical angle of θ
_s
= 36°. Consequently, the MAS PiG plays a promising role in the luminescent converter for high-quality WLEDs and can significantly improve the luminescent performances.