Optical and reliability properties studies of Sr_4Al_(14)O_(25)∶Eu~(2+) film for high-CRI white LEDs

摘要

This study is aimed at obtaining a relatively higher-color-rendering index (CRI) white LED using a blue-emitting Sr_4Al_(14)O_(25)∶Eu~(2+) phosphor that could smooth out LED flicker. In order to study the luminescence of the phosphors in the LED package, a thin Sr_4Al_(14)O_(25)∶Eu~(2+) film and three-phosphors-containing (green YAG∶Ce~(3+), red CASN∶Eu~(2+), and indigo Sr_4Al_(14)O_(25)∶Eu~(2+)) film were prepared using a spin coating method. Meanwhile, three-phosphors-LED package was fabricated using a dispensing process, whereby the chip surface was automatically leveled to form a film with the same composition and components as that of the three-phosphors-containing film. In order to study the reliability of Sr_4Al_(14)O_(25)∶Eu~(2+) phosphors in the resin, high-temperature and high-humidity test, Xenon lamp aging test, and thermal cycling test were carried out. The Sr_4Al_(14)O_(25)∶Eu~(2+) phosphors in the resin were also characterized through photoluminescence (PL) and PL decay curve analyses. The electroluminescence, correlated color temperature, and temperature-dependent PL of the three-phosphors-containing film were measured using an integrating sphere. The three-phosphors-containing film displayed high reliability and thermal stability. The blue LED was coated with a three-phosphors-containing film, which led to a correlated color temperature of ～4500 K and a high CRI (Ra＞90.2).This LED package had an afterglow light that could eliminate the observed LED flicker.