Implications of Phosphor Coating on the Thermal Characteristics of Phosphor-Converted White LEDs

Abstract

Abstract-The phosphor layer in phosphor-converted white Light Emitting Diodes (pcLEDs) affects their optical and thermal performances. This paper reports the effects of phosphor thickness and particle concentration on the optical efficiency and temperature rise on conformal phosphor-coated LED package. It is observed that a thicker phosphor layer and a higher phosphor particle concentration will increase the amount of backscattering and back reflection of light from the phosphor layer. These light extraction losses not only reduce the optical efficiency of the light output but also cause heat accumulation in the phosphor layer, leading to higher LED junction temperature. At 2700 K correlated colour temperature (CCT), the temperature rise is observed to increase by as much as 2.6 times as compared to its blue emitting LED package. However, the self-heating effect can be reduced through its die-bonding configuration. Structure function-based thermal evaluation shows heat accumulation in the phosphor layer and that flip-chip bonding can dissipate the heat generated in the GaN LED and phosphor layer effectively. Evidence in this study demonstrates that optical efficiency and thermal resistance of pcLEDs are dependent on the CCT ratings.

Effects of humidity on the electro-optical-thermal characteristics of high-power LEDs

“…1) causing higher light scattering and absorption losses in the phosphor layer, leading to higher extraction losses for the FC LEDs. Research on this impact of the phosphor layer on the optical output has been reported elsewhere by this research team [11]. In a phosphor converted LED package, the light emitted from the package is determined by both the LED device and the phosphor layer.…”

Improving color uniformity and color rending index of remote-phosphor packaging white LEDs by co-doping SiO2 and Sr2Si5N8:Eu2+ particles

“…Nowadays, light-emitting diodes (LEDs) are popularly used, with a rapid progress, for lighting applications such as traffic signals, signage, vehicle lighting, and liquid crystal display backlight. They became a critical illumination source because of their high efficiency, long lifetime, low energy consumption, low cost, and environmental friendliness compared to conventional lighting sources [1,2]. Up to date, there are three methods to obtain white light emission in white light-emitting diodes (WLEDs).…”