The effects of SiO2@Y2O2S:Eu3+ phosphor on the optic characteristics of white light-emitting diodes

Abstract

The study investigated the effectiveness of coating silica nanoparticles (SiO₂) and resin-silica nanocomposites poly methyl methacrylate (PMMA)-silicaover the surface of Y₂O₂S:Eu³⁺ red phosphors. The purpose of this surface coating is to enhance the optical properties, including the photoluminescence (PL) and long-term stability, of Y₂O₂S:Eu³⁺. Two methods used to coat the phosphor with 5-mm silica nanoparticles are dip-coating and sol-gel (Stöber) methods. SiO₂ nanoparticles were formed via hydrolysis and condensation reactions, while radical polymerization was performed to fabricate the poly (1-vinyl-2-pyrrolidone). The Y₂O₂S:Eu³⁺ surface coating of PMMA-silica composite was performed via two reactions. One is the reaction of SiO₂ nanoparticles with methyl methacrylate (MMA) monomer, and the other is MMA-tetraethyl orthosilicate (TEOS) reaction. The results showed that by using the latter method, Y₂O₂S:Eu³⁺ yielded better PL and long-term stability. Additionally, surface coating with the PMMA-SiO₂ nanocomposite using the second technique resulted in 5% enhancement in PL and stabilized the cathode luminescence (CL) intensity of Y₂O₂S:Eu³⁺, compared to those properties of uncoated Y₂O₃S:Eu³⁺ phosphor particles.