Phosphor Temperature Overestimation in High-Power Light-Emitting Diode by Thermocouple

Phosphor temperature in high-power white light-emitting diodes can greatly affect the optical properties, reliability, and lifetime. Accurate estimation of phosphor temperature is the first step for enhancing thermal management inside the package. In this paper, the phosphor temperature was measured by a plug-in method with thermocouple. The thermocouple's bead was inserted into the phosphor layer, and then the silicone matrix got cured. The phosphor temperature was measured under various input currents. Under 350 mA, the temperature difference between the measured value and the junction temperature was about 17 °C higher than those in the references. The reason for this overestimation was attributed to light energy absorption and conversion of the bead, which was confirmed by thermal simulations.