Bicolor phosphor-in-glass film with highly reflective interface design for high-quality laser-driven white lighting

Abstract

Phosphors-in-glass films (PiGFs) with thermally conductive substrates are considered to be an efficient color inorganic color conversion material for laser lighting. However, due to the contradiction between the light extraction and heat dissipation, achieving high brightness and excellent color quality simultaneously is still a big challenge. Herein, a unique architecture of bicolor PiGF with highly reflective interface design was proposed for high-quality laser lighting. The TiO2-glass films with different thicknesses were prepared on highly heat-conducting AlN substrates to obtain the TiO2–AlN (TA) substrates with various reflectance. In addition, mixed green/red, stacked green-red, and stacked red-green phosphor glass films were printed and sintered on the TA substrates to prepared three bicolor PiGF converters of M-PiTA, G-R-PiTA, and R-G-PiTA. At the TiO2-glass film thickness of 100 μm, the M-PiTA enables a luminous flux of 2053 lm@24.8 W/mm2, which is 1.9 times that of traditional M-PiGF-AlN converter (1077 lm@17.6 W/mm2). The M-PiTA converter realizes a high-quality white light with a CRI of 82.7 and a chromaticity coordinate of (0.3378, 0.3297). Furthermore, the M-PiTA converter enables higher luminance and light quality compared with the stacked G-R-PiTA and R-G-PiTA converters. With the laser power of 4.2 W, the working temperature of M-PiTA converter is only 59.2 °C, while that of R-G-PiTA and G-R-PiTA converters rises to 499 °C and 301 °C. The results demonstrate that the bicolor PiTA converters have broad prospects in the application of laser lighting.