Blue-emitting Sr1-xCaxLu2O4:Ce3+ phosphors for high CRI white LEDs

Abstract

A broadband blue-emitting Sr1-xCaxLu2O4:Ce3+ (x = 0–0.2) phosphors were synthesized, which can be used for near-UV pumped white light-emitting diodes (w-LEDs). The crystal structures, photoluminescence properties, external quantum efficiency, thermal stability and application performance of Sr1-xCaxLu2O4:Ce3+, by partially substituting Sr2+ with Ca2+ (x = 0–0.2), were studied by various analytical techniques. When the Ca/Sr ratio of Sr1-xCaxLu2O4:Ce3+ gradually increases, the emission peak of Sr1-xCaxLu2O4:Ce3+ red-shiftes from 459 to 465 nm, corrected external quantum efficiency increases from 31.8% to 42.9%, and the thermal stability is also improved. The mechanism of the changes of the photoluminescence emission and excitation spectra, external quantum efficiency and thermal stability properties was also investigated in detail. In addition, a w-LED was fabricated by using SrLu2O4:Ce3+ (blue), β-sialon:Eu2+ (green) and (Sr,Ca)AlSiN3:Eu2+ (red) phosphors combined with a 405 nm near-UV LED chip, and its color rendering index (CRI) reaches 96.0. When Sr0.8Ca0.2Lu2O4:Ce3+ is applied as blue phosphor to substitute SrLu2O4:Ce3+, the obtained w-LED devices have high luminous efficiency, and CRI greater than 95.0. These results show that the Sr1-xCaxLu2O4:Ce3+ can be potential blue phosphors for n-UV pumped high CRI w-LEDs application.