Determining Temperature-Dependent Optical Characteristics of Remote Phosphor Plates by Transmission-Type Measurement System

We propose a transmission-type measurement system for determining temperature-dependent optical characteristics (TDOCs) for phosphors or remote phosphor plates which are applied in high-power white light-emitting diodes, related to their stabilities and reliabilities. The proposed measurement system possesses remote-excitation characteristics and is able to separately control the temperature of tested phosphors or remote phosphor plates and that of excitation light sources (with the emission wavelength of 360-470 nm), to avoid the heat interference between them. This system is finally examined by fabricating two types of remote phosphor plates, i.e., yellow Y
₃
Al
₅
O
₁₂
:Ce
³⁺
and red CaAlSiN
₃
:Eu
²⁺
remote phosphor plates. A comparison between the proposed transmission-type system and the reflection-type system at various temperatures is also carried out. Results show that both the phosphor quantum efficiency and phosphor conversion efficiency of remote phosphor plates under various temperatures are possibly overestimated by the traditional reflection-type system. Employing the proposed method and carrying out experiments, we discover that the fraction of silicone in the silicone-phosphor mixture affects TDOCs of remote phosphor plates remarkably. Finally, via both the proposed system and the microhyperspectral imaging technology, thermal-quenching effects in the microcosmic level have also been investigated.