Optically recoverable, deep ultraviolet (UV) stable and transparent sol-gel fluoro siloxane hybrid material for a UV LED encapsulant

An ultraviolet (UV) transparent recoverable fluoro-siloxane hybrid material was prepared via a facile sol-gel process. The transparency and stability of a deep UV-LED encapsulant is a key factor in the light extraction efficiency and long-term reliability of a UV LED. In this study, we report a novel UV-LED encapsulation process through the thermal hydrosilylation curing of vinyl-fluoro and hydrogen-methyl oligosiloxane resins. The fluoro-siloxane hybrimer showed high UV transparency in the deep UV (<300 nm) region, with increased transmittance after UVB (300 nm) and UVC (250 nm) aging for 2000 hours from radical stabilization and a high cross-linking density. Specifically, vinyl radical formation and recombination during UV irradiation and their effects on deep UV transmittance were investigated. With its easy low-temperature solution processability and robust performance stability, the fluoro-siloxane hybrimer was used as a deep UV-LED packaging material to demonstrate its potential as a stable encapsulant that is also UV transparent.