Enriching red emission of Y₃Al₅O₁₂: Ce³⁺ by codoping Pr³⁺ and Cr³⁺ for improving color rendering of white LEDs

Triply doped Y₃Al₅O₁₂: Ce³⁺, Pr³⁺, Cr³⁺ phosphors are prepared by solid state reaction. The emission spectra are enriched in the red region with the luminescence of both Pr³⁺ and Cr³⁺ through Ce³⁺→Cr ³⁺ and Ce³⁺→Pr³⁺→Cr³⁺ energy transfers. The properties of photoluminescence and fluorescence decay indicates larger macroscopic Ce³⁺→Cr³⁺ transfer rates in the triply doped phosphors in comparison to Ce³⁺ and Cr ³⁺ doubly doped one, reflecting the effect of competition between Ce³⁺→Cr³⁺ and Ce³⁺→Pr³⁺ transfers. White LEDs fabricated using the triply doped phosphor coated on blue LED chips show a color rendering index of 81.4 higher than that either using Ce³⁺ and Cr³⁺ doubly doped or Ce³⁺ singly doped phosphor.