The reduction of the thermal quenching effect in laser-excited phosphor converters using highly thermally conductive hBN particles

Abstract

AbstractPhosphor converters for solid state lighting applications experience a strong thermal stress under high-excitation power densities. The recent interest in laser diode based lighting has made this issue even more severe. This research presents an effective approach to reduce the thermal quenching effect and damage of laser-excited phosphor-silicone converters using thermally conductive hexagonal boron nitride (hBN) particles. Herein, the samples are analyzed by employing phosphor thermometry based on the photoluminescence decay time, and thermo-imaging techniques. The study shows that hBN particle incorporation increases the thermal conductivity of a phosphor-silicone mixture up to 5 times. It turns out, that the addition of hBN to the Eu$$^{2+}$$ 2 + doped chalcogenide-silicone converters can increase the top-limit excitation power density from 60 to 180 W cm$$^{-2}$$ - 2 , thus reaching a 2.5 times higher output. Moreover, it is shown that the presence of hBN in Ce$$^{3+}$$ 3 + activated garnet phosphor converters, may increase the output power by up to 1.8 times and that such converters can withstand 218 W cm$$^{-2}$$ - 2 excitation. Besides, hBN particles are also found to enhance the stability of the converters chromaticity and luminous efficacy of radiation. This means that the addition of hBN particles into silicone-based phosphor converter media is applicable in a wide range of different areas, in particular, the ones requiring a high optical power output density.