Long afterglow green luminescence of Tb3+ ion in Ga4GeO8 through persistent energy transfer from host to Tb3+

Highlights: • Novel long afterglow green luminescent material of Ga₄GeO₈: Tb³⁺ was developed. • The persistent energy transfer from host to Tb³⁺ resulted in afterglow emission. • The appropriate trap depths answered for good afterglow luminescent performance. In this paper, a novel long afterglow green luminescent material of Ga₄GeO₈: Tb³⁺ has been successfully synthesized by high-temperature solid-state method. Ga₄GeO₈ showed long afterglow blue emission peaked at 490 nm. When Tb³⁺ ions were introduced into the host, the strong long afterglow green emission from the f-f transition of Tb³⁺ appeared and the blue afterglow emission of the host disappeared completely. Furthermore, the obtained results have shown that the afterglow emission of the host overlapped with typical excitation wavelengths of Tb³⁺ in the range 300–500 nm, indicating of persistent energy transfer from the host to Tb³⁺ ions. The thermoluminescence curves monitored at 490 and 550 nm belonged to the afterglow emissions of host and Tb³⁺ respectively were similar, which consisted of two peaks at T_A (303 K) and T_B (350 K) corresponded to the shallow trap and the deep trap and the trap depths were estimated to be 0.606 and 0.732 eV. This further confirmed that the persistent energy transfer form host to Tb³⁺ ions was responsible for the excellent long afterglow green luminescence of Ga₄GeO₈: Tb³⁺. Thus, the efficient persistent energy transfer of host to emitting center can be regarded as an effective strategy to realize more colors novel long afterglow luminescent materials.