Photoluminescent properties of SrSi₂O₂N₂ : Eu²⁺phosphor: concentration related quenching and red shift behaviour

Abstract

Highly efficient green phosphors SrSi2O2N2 : Eu2+, suitable for white light emitting diodes (LEDs), was synthesized by solid-state reaction and their photoluminescence properties were investigated. SrSi2O2N2 : Eu2+ phosphors can be effectively excited by ultraviolet (UV)–Vis light (300–460 nm) and yield green emission with a single, intense, broad band centred at around 540 nm. Concentration quenching occurs in the phosphors when the Eu2+ concentration exceeds 2 at%. The mechanism of concentration quenching is confirmed to be dipole–dipole interaction of Eu2+. With an increase in the Eu2+ concentration, the emission band of Eu2+ shifts to a longer wavelength due to the 5d-orbit hybridization of Eu2+ with the host crystal and the energy transfer between adjacent Eu2+ ions. All the results indicate that SrSi2O2N2 : Eu2+ is a promising green phosphor for UV or blue chip based white LEDs.