Sandwich structured phosphor-in-glass films enabling laser lighting with superior optical properties

YAG:Ce3+ PiG film cannot produce high color-rendering laser lighting due to the deficiency in red spectral component, but adding nitride-based red phosphors usually leads to dramatic decrease of brightness and efficiency as a result of their obvious luminance saturation. In this work, a sandwich structured PiG (SS-PiG) film was created using green-emitting YAGG:Ce3+ and orange-emitting GdYAG:Ce3+ phosphors, where two types of PiG films were separately co-fired on each surface of a sapphire substrate. The color-rendering index of SS-PiG film can reach 81.4 upon blue laser excitation, improved by 24.3% when compared with that of YAG:Ce3+ PiG film (65.5). Driven by blue laser diodes with a flux density of 7.69 W mm-2, the SS-PiG film shows a luminous emittance of 1362 lm mm-2, which is 179% higher than traditional multilayer structured PiG film (489 lm mm-2). The SS-PiG film enables to enhance both of color rendition and luminance of laser-phosphor-converted lighting.