Phosphor-converted laser-based solid-state lighting device in transmission mode using transparent conducting oxide substrate

Abstract Laser excitation of phosphorescent material (inorganic phosphor) to produce super-bright white light leads to thermal quenching. This article presents an innovative thermal heat reduction scheme that addresses the issue of phosphor heating. This study demonstrates a transparent conducting oxide film on a glass substrate under three conditions: low laser power with a heat sink, high laser power, and increased glass thickness. The characteristics of produced white light are examined in detail, and a electro-thermal equivalent circuit is devised. Indium-tin oxide (ITO) film mitigates thermal and color instability issues, along with the flickering of a light source in transmission mode. Owing to the elevated conductivity of ITO film, it functions as a heat sink, absorbing thermal energy from the phosphor (luminescent material). It disperses heat to the underlying glass substrate via diffusion and into the ambient air more effectively than a conventional glass substrate. It is more economical than utilizing diamond or sapphire substrate. This work is expected to boost the applications of transmissive laser lighting. Experimental results of laser-based solid-state lighting (LB-SSL) devices in transmission mode are presented utilizing ITO-coated glass (ITOG). We observed substantial heat conduction through ITOG and reduced thermal quenching of the photoluminescent spectrum compared to standard glass.