Optical EngineeringThermally stable conformal encapsulation material for high-power ultraviolet light-emitting diodes
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A conformal encapsulation material for use in high-power, thermally stable ultraviolet (UV) light-emitting diodes was successfully developed. For silicone, thermal degradation started at ∼ 200°C , and the transmittance was 85.5% at 365 nm. The transmittance decreased by 55% after thermal aging at 250°C for 72 h and it decreased further by 2.5%, even at room temperature, under continuous exposure to UV light at 365 nm for 72 h. By contrast, for the sol–gel material, thermal degradation started at ∼ 300°C , and the transmittance was 90% at 365 nm. The transmittance decreased negligibly after thermal aging at 250°C for 72 h and it did not decrease further even at 75°C under continuous exposure to UV light at 365 nm for 72 h.