Enhanced luminescence of a silica-nitride phosphor; La3Si6N11:Ce3+by using Cr3+-activated TiO2 nanoparticles

Abstract

Ce³⁺-activated silica nitride phosphors (lanthanum silicate-nitride [LSN]) are promising thermostable conversion components for white-light-emitting diodes, screen technologies, and other optoelectronic applications. Cr³⁺-activated TiO₂, on the other hand, is a strongly absorbing material depending on its size and optical microenvironment. In this work, we gathered Cr³⁺-doped TiO₂ and La₃Si₆N₁₁:Ce³⁺ in an optically transparent polymethylmethacrylate matrix. Photoluminescence of the binary blends of La₃Si₆N₁₁:Ce³⁺/TiO₂ and La₃Si₆N₁₁:Ce³⁺/TiO₂:Cr³⁺ has been investigated under two different excitation energies by steady-state and lifetime-based measurements, respectively. When the microscale La₃Si₆N₁₁:Ce³⁺ phosphor and nanoscale TiO₂:Cr³⁺ particles were gathered at a critical concentration, the resulting composite exhibited 3.14-fold enhancement in the emission signal intensity with respect to the additive-free phosphor. Upon excitation, the La₃Si₆N₁₁:Ce³⁺–TiO₂:Cr³⁺ blend exhibited different excited-state lifetimes for the nano- and microsecond time-scales compared to the LSN. The microsecond time-scale measurements performed under 378 nm excitation supported the existence of a potential energy transfer from the TiO₂:Cr³⁺ to the La₃Si₆N₁₁:Ce³⁺.