CaAlSiN3:Eu/glass composite film in reflective configuration: A thermally robust and efficient red-emitting color converter with high saturation threshold for high-power high color rendering laser lighting

To achieve high color rendering and proper color temperature, a red color converter is essential for phosphorconverted white lighting devices. CaAlSiN3:Eu2+ (CASN) is a highly suitable red phosphor for white lightemitting diodes. However, it can be hardly used in high-power laser lighting due to poor thermal/chemical performance of the phosphor/silicone resin mixture. A series of all-inorganic CASN-based phosphors (e.g., composite ceramic and phosphor-in-glass) were developed to avoid the use of resin. However, new challenges emerged: none of them showed sufficient luminous efficacy (i.e., >50 lm/W) and adequate saturation-threshold (i.e., >30 W or 10 W/mm2). Here, we report a facile fabrication of CASN/glass composite films using a simple and efficient blade-coating method. Upon 450 nm excitation, the resultant composite film presents a high internal quantum efficiency of -83%, comparable to that of pristine CASN powder (-90%). When irradiated with a blue laser, the composite film shows a record high luminous efficacy of 82 lm/W. Furthermore, its saturation threshold was investigated in high power and high power density mode, respectively. When measured in high power mode, it shows a high saturation threshold over 29.7 W (1.75 W/mm2), thus achieving a high luminous flux of 1576 lm; when measured in high power density mode, it shows a saturation threshold of -10.2 W/mm2 (1.13 W). With abovementioned excellent properties, the CASN/glass composite film has great potential for use in high-power and high color rendering laser lighting.

Automated summary

In order to address the poor thermal/chemical performance of red phosphors in high-power laser lighting, all-inorganic CASNN-based phosphors have been developed to avoid the use of resin. A facile fabrication method was reported for CASN/glass composite films with high quantum efficiency and record high luminous efficacy. The composite film showed excellent properties in terms of color rendering, luminous efficacy, and saturation threshold in both high power and high power density modes.