Highly Thermally Stable Single-Component White-Emitting Silicate Glass for Organic-Resin-Free White-Light-Emitting Diodes

Abstract

Thermal management is still a great challenge for high-power phosphor-converted white-light-emitting diodes (pc-WLEDs) intended for future general lighting. In this paper, a series of single-component white-emitting silicate SiO₂–Li₂O–SrO–Al₂O₃–K₂O–P₂O₅: Ce³⁺, Tb³⁺, Mn²⁺ (SLSAKP: Ce³⁺, Tb³⁺, Mn²⁺) glasses that simultaneously play key roles as a luminescent convertor and an encapsulating material for WLEDs were prepared via the conventional melt-quenching method, and systematically studied using their absorption spectra, transmittance spectra, photoluminescence excitation and emission spectra in the temperature range 296–498 K, decay curves, and quantum efficiency. The glasses show strong and broad absorption in 250–380 nm region and exhibit intense white emission, produced by in situ mixing of blue-violet, green, and orange-red light from Ce³⁺, Tb³⁺, and Mn²⁺ ions, respectively, in a single glass component. The quantum efficiency of SLSAKP: 0.3%Ce³⁺, 2.0%Tb³⁺, 2.0%Mn²⁺ glass is determined to be 19%. More importantly, this glass shows good thermal stability, exhibiting at 373 and 423 K about 84.56 and 71.02%, respectively, of the observed room temperature (298 K) emission intensity. The chromaticity shift of SLSAKP: 0.3%Ce³⁺, 2.0%Tb³⁺, 2.0%Mn²⁺ is 2.94 × 10^–2 at 498 K, only 57% of the commercial triple-color white-emitting phosphor mixture. Additionally, this glass shows no transmittance loss at the 370 nm emission of a UV-Chip-On-Board (UV-COB) after thermal aging for 240 h, compared with the 82% transmittance loss of epoxy resin. The thermal conductivity of the glass is about 1.07 W/mK, much larger than the 0.17 W/mK of epoxy resin. An organic-resin-free WLEDs device based on SLSAKP: 0.3%Ce³⁺, 2.0%Tb³⁺, 2.0%Mn²⁺ glass and UV-COB is successfully demonstrated. All of our results demonstrate that the presented Ce³⁺/Tb³⁺/Mn²⁺ tridoped lithium–strontium–silicate glass may serve as a promising candidate for high-power WLEDs