Tailoring thermal behavior and luminous performance in LuAG:Ce films via thickness control for high-power laser lighting applications

Abstract

Lutetium aluminum garnet doped with cerium (LuAG:Ce) thin films have been identified as a promising material for high-power laser-driven lighting applications. In this study, spray pyrolysis we employed to fabricate LuAG:Ce films on sapphire substrates and the impact of film thickness on thermal management and light emission efficiency was investigated. Our results show that, regardless of thickness, LuAG:Ce films exhibit impressive internal quantum efficiencies (IQE) exceeding 83.2% and external quantum efficiencies (EQE) surpassing 56.4%, with minimal alteration of luminescent color. Notably, thinner films facilitate more efficient heat dissipation to the underlying sapphire substrate, resulting in superior thermal management and outstanding luminous performance under high-power laser excitation. Specifically, the thinnest LuAG:Ce film (15.79 μm) exhibited rapid thermal stabilization (~ 130 °C within 30 s) and maintained stability during continuous irradiation lasting 30 min, with a corresponding decrease in luminous flux to 87.9% of its initial value within the first 60 s. This film also demonstrated relatively high and stable conversion efficiency and luminous efficiency, achieving higher saturation thresholds (15 W·mm⁻²) and luminous flux (1070 lm). In contrast, thicker films exhibited a shift in the saturation point toward lower power densities. These findings provide valuable insights for the practical implementation of LuAG:Ce films in advanced lighting technologies.

Graphic abstract