Blue-emitting Sr_(1-x)Ca_xLu_2O_4:Ce~(3+) phosphors for high CRI white LEDs

A broadband blue-emitting Sr_1-xCa_xLu₂O₄: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 Sr_1-xCa_xLu₂O₄:Ce³⁺, by partially substituting Sr²⁺ with Ca²⁺ (x = 0–0.2), were studied by various analytical techniques. When the Ca/Sr ratio of Sr_1-xCa_xLu₂O₄:Ce³⁺ gradually increases, the emission peak of Sr_1-xCa_xLu₂O₄: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 Sr_0.8Ca_0.2Lu₂O₄: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 Sr_1-xCa_xLu₂O₄:Ce³⁺ can be potential blue phosphors for n-UV pumped high CRI w-LEDs application.