Generating yellow and red emissions by co-doping Mn²⁺ to substitute for Ca²⁺ and Sc³⁺ sites in Ca₃Sc₂Si₃O₁₂: Ce³⁺ green emitting phosphor for white LED applications

We report luminescence properties of Ce³⁺ and Mn²⁺ co-activated Ca₃Sc₂Si₃O₁₂ (CSS) silicate garnets. It is observed that Mn²⁺ may not only occupy Ca²⁺ sites to generate a yellow emission (Mn²⁺(I)) at 574 nm but also Sc³⁺ sites to generate a red emission (Mn²⁺(II)) at 680 nm. Considerable Mn²⁺ substitution for Sc³⁺ can be performed through balancing their charge difference by introducing a trivalent rare earth ion, such as La³⁺ and Ce³⁺, to replace Ca²⁺. Meanwhile, remarkable energy transfer from the green emitting Ce³⁺ to both Mn²⁺(I) and Mn²⁺(II) can occur, making tunable color and white light emission available in CSS: Ce³⁺, Mn²⁺ upon blue excitation into Ce³⁺. White LEDs combined by CSS: Ce³⁺, Mn²⁺ phosphors and blue LED chips are fabricated. A CSS: 0.03Ce³⁺,0.2Mn²⁺ phosphor with deficient red emission is enriched in red by increasing Ce³⁺ concentration to 0.1, which leads to increase of Mn²⁺(II) number in case of charge compensation by more Ce³⁺ ions. Consequently, the color rendering index of the white LEDs is improved from 64 to 76. The results of this work indicate that CSS: Ce³⁺, Mn²⁺ garnet could be a promising single phase phosphor for white LEDs.