Photoluminescence enhancement of orange-emitting Ca5(PO4)2SiO4:Sm3+ phosphor through charge compensation of A+ (Li+, Na+ and K+) ions for white light-emitting diodes

Abstract

The orange-emitting Ca_5−x(PO₄)₂SiO₄:xSm³⁺ (C₅PSO:Sm³⁺) phosphor was prepared via a simple solid-state method, and the charge compensators A⁺ (A = Li, Na and K) were codoped into C₅PSO:Sm³⁺ for improving the luminescence performance. The influences of Sm³⁺ doping and Sm³⁺/A⁺ codoping on the crystal structure and the luminescence performance of the C₅PSO:Sm³⁺ phosphor were investigated in detail. The X-ray diffraction results exhibited that all the as-prepared samples were assigned to the standard structure Ca₅(PO₄)₂SiO₄ possessing the P63/m space group. Upon near-ultraviolet excitation at 401 nm, the characteristic emission peaks of the C₅PSO:Sm³⁺ phosphors are located at 558 nm, 605 nm and 656 nm, respectively, which are derived from the ⁴G_5/2 → ⁶H_J (J = 5/2, 7/2, and 9/2) electron transitions of Sm³⁺ ions. Furthermore, a significant luminescence improvement of the C₅PSO:Sm³⁺ phosphor was attained through charge compensation of codoped A⁺ ions, and the emission intensity is enhanced by 1.79-, 1.45-, and 1.14-fold for K⁺, Na⁺, and Li⁺, respectively. In addition, the actual orange-red LED and w-LED fabricated with the as-prepared C₅PSO:Sm³⁺,K⁺ phosphor showed excellent optical performance. All the results demonstrated that the C₅PSO:Sm³⁺,K⁺ orange-emitting phosphor could act as a potential orange-red component in the w-LEDs illumination field.