Jong Myeon Lee

Luminescent Properties of Ca-α-SiAlON : Eu2 + Phosphors Synthesized by Gas-Pressured Sintering

Rare-earth-doped oxynitride or nitride compounds have been reported to be photoluminescent and may then serve as new phosphors with good thermal and chemical stabilities. In this work, Ca-α-SiAlON:Eu 2+ based yellow and orange oxynitride phosphors with compositions of Ca 0.485 Eu 0.015 Si 9.2 Al 2.8 O 1.8 N 14.2 and Ca 0.94 Eu 0.06 Si 9 Al 3 ON 15 were prepared using the gas-pressured sintering method. The crystallinity and particle morphology of the prepared phosphors were characterized. The temperature dependence of photoluminescence properties was investigated from 25 to 150°C. The Stokes shift and zero-phonon line was calculated mathematically and estimated from the spectral data. The prepared Ca-α-SiAlON:Eu 2+ phosphors showed superior thermal quenching properties compared to commercially used YAG:Ce 3+ phosphors. In addition, the activation energies (ΔE) for thermal quenching of the prepared Ca-α-SiAlON:Eu 2+ phosphors were determined by Arrhenius fitting.

Enhancement of Light Extraction Efficiency in Light-Emitting Diodes with Prism-Type Textured Top Surface

The light extraction efficiency of side-view light-emitting diodes (LEDs) with a textured encapsulant top surface is analyzed theoretically and experimentally. A prism-type textured surface is proposed in order to increase the extraction efficiency, which is calculated by ray-tracing simulations. According to the simulation results, extraction efficiency can be enhanced by up to 35% compared with that of conventional LEDs. By using an imprinting technique to texture the encapsulant top surface, a prism-structure array has been fabricated. The experimental enhancement of light extraction efficiency is 14% for blue LEDs and 10% for white LEDs.