Phosphors for LED-based light sources: Thermal properties and reliability issues

Dal Lago M;Meneghini M;Trivellin N;MURA, GIOVANNA;VANZI, MASSIMO;Meneghesso G;Zanoni E.

2012-01-01

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Abstract

The aim of this work is to investigate the thermal stability of remote phosphor plates to be used in solid-state lighting systems, for the conversion of the blue light emitted by GaN-based LEDs into white light. A preliminary thermal characterization revealed that in normal conditions of blue light irradiance the phosphor plates can reach temperature levels higher than 60 °C, which can affect both performance and reliability. The results of accelerated thermal stress tests indicate that high temperature levels can trigger a relevant degradation mechanism (estimated activation energy is 1.2 eV), that drastically reduces the phosphor conversion efficiency and modifies the photometric and colorimetric characteristics of the emitted white light.