Gradient refractive index structure of phosphor‐in‐glass coating for packaging of white LEDs

Abstract

AbstractA gradient refractive index (GRIN) structure, with a gradual increase in the refractive index from the glass substrate, was successfully obtained by multilayer screen printing for white light‐emitting diodes (w‐LEDs) packaging. Each phosphor‐in‐glass (PiG) coating consisted of B2O3–SiO2–ZnO glass matrix and yellow phosphor. The gradually increased refractive index (1.62, 1.72, and 1.82) of glass matrices were obtained from higher molecular weight of La2O3 and WO3. After sintering at 600°C, no obvious interface was observed and the phosphor particles were mixed thoroughly in the glass matrix. When the phosphor content was 50 wt%, the white‐light emission was obtained. Compared with those based on the nongradient and low‐refractive PiG coating, the luminous efficacy of w‐LEDs constructed by the PiG coating with GRIN was enhanced. It shows that the GRIN structure is beneficial to improve the luminous efficacy of w‐LEDs.