Enhancing Sm³⁺ red emission via energy transfer from Bi³⁺→Sm³⁺ based on terbium bridge mechanism in Ca₂Al₂SiO₇ phosphors

Currently, the key change for white-LED is to improve the luminescence efficiency of red phosphor. Sm³⁺ activated phosphor was considered due to suitable emission position of red light. However, the luminescence intensity in the red region is weak. For enhancing red-emitting of Sm³⁺, Bi³⁺ and Tb³⁺ ions were introduced into Ca₂Al₂SiO₇:Sm³⁺ phosphors based on the concept of energy transfer. For Ca₂Al₂SiO₇:Bi³⁺, Sm³⁺ samples, it can be observed that the energy transfer process was blocked. Hence, Tb³⁺ was introduced into Ca₂Al₂SiO₇:Bi³⁺, Sm³⁺ samples to increase Sm³⁺ luminescence intensity based on Bi³⁺→Tb³⁺→Sm³⁺ energy transfer process. Compared with Sm³⁺ single-doped Ca₂Al₂SiO₇ phosphor, the luminescence intensity of Sm³⁺ was enhanced by 2.6 times. It can be found that Tb³⁺ ions play a role of storing the energy or transfer bridge from Bi³⁺→ Sm³⁺ by investigating the Ca₂Al₂SiO₇:Bi³⁺, Tb³⁺ and Ca₂Al₂SiO₇:Tb³⁺, Sm³⁺ energy transfer mechanism. All these results suggest that terbium branch mechanism plays an important role on enhancing activators luminescence intensity.