High color rendering and high-luminance laser lighting using all inorganic nitride phosphor films

Despite the huge advances that have been made in the development of ultra-high luminance laser lighting, achieving high color rendering properties in such systems at the same time remains a challenge. Recent studies show that in most cases, the luminous efficacy (LE) of laser lighting is compromised to improve the color rendering index (CRI). In this study, a possible solution to this problem has been proposed by preparing phosphor-in-glass (PiG) films comprised of the yellow-emitting phosphor (LSN:Ce³⁺) and the red-emitting phosphor (CASN:Eu²⁺). The composite material synthesized in this study exhibited outstanding optical and thermal properties. A uniform white light with a high CRI of 80.0 and a high LE of 185.9 lm W^-1 was achieved by optimizing the yellow/red ratio and the emission peak position of the blue laser. Furthermore, it was found that this design enabled the phosphor to restrict the light emission area effectively, thus attaining a high luminous exitance of 1302 lm mm^-2. With their superior optical performance, the PiG films can be regarded as promising color converter candidates for future high-quality laser-based white light sources.