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.