Influence of Phosphor Saturation on 2-D Temperature Measurement in Phosphor- Converted LEDs by Microscopic Hyperspectral Imaging

Abstract

We perform an experimental study on the impact of phosphor saturation on 2-D temperature measurement for InGaN/GaN-based phosphor-converted light-emitting diodes (pc-LEDs). These pc-LEDs generally consist of 455-nm InGaN/GaN-based blue LEDs and 623-nm CaAlSiN <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{3}}$</tex-math> </inline-formula> :Eu <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text{2}+}$</tex-math> </inline-formula> -based red phosphors. The advanced microscopic hyperspectral imaging system is used to monitor 2-D phosphor saturation in these used pc-LEDs. At the same time, this technique can also be used to detect 2-D surface temperature distribution in red pc-LEDs after determining the relationship between surface temperature and temperature-sensitive parameter such as the normalized emission intensity of phosphors and relevant coefficients in their linear relationships. For the ease of analysis, we propose a factor for describing phosphor saturation in pc-LEDs, which is, namely, by phosphor saturation factor (PSF). Then, the influence of phosphor saturation on temperature measurement errors based on PSF is also analyzed. Finally, we believe that this work can provide a useful guidance for experimental understanding of 2-D photo-thermal characteristics in such type of pc-LEDs, which would be extensively applied in future lighting and display fields.