Cold-Sintered phosphor film@Cu converter for ultra-high-brightness laser illumination

Phosphor ceramic has been regarded as a promising color converter for high-quality laser illumination, but it often suffers from optothermal performance degradation during high-temperature sintering process. Herein, an optothermal-enhanced cold-sintered phosphor film@Cu (PF@Cu) converter is developed. A low-temperature (150℃) cold sintering process (CSP) was introduced and tunable composite pastes were prepared with geopolymer, alkali activator, and phosphor materials. High-performance yellow-emitting PF@Cu (Y-PF@Cu) and yellow/red-emitting PF@Cu (Y/R-PF@Cu) converters were prepared with densified PFs that tightly integrated with the Cu substrate while effectively preserving the intrinsic luminescent properties of phosphors. The optimized Y-PF@Cu converter achieves a record luminous flux (LF) of 9624.7 lm@35 W/mm2, a correlated color temperature (CCT) of 5931 K and a color rendering index (CRI) of 60.7. The further optimized Y/R-PF@Cu converter delivers excellent comprehensive performance, including a high thermal conductivity of 50.6 W/(m·K), a LF of 2652.2 lm@17.5 W/mm2, a CCT of 2604 K, and a significantly improved CRI of 91.2. This work demonstrates the feasibility of CSP for fabricating color converters and provides an efficient strategy for synergistic optothermal optimization in ultra-high-brightness laser-illumination applications.