Ultraviolet-B persistent luminescence and thermoluminescence of bismuth ion doped garnet phosphors

Ultraviolet persistent luminescence technology holds potential for some new applications where ultraviolet emission is needed but constant external excitation is unavailable. Despite the promising applications, not much is known about such luminescence. Here we report ultraviolet-B (290-320 nm) persistent luminescence phenomenon in isostructural Y₃Ga₅O₁₂:Bi³⁺ and Y₃Ga₅O₁₂:Bi³⁺ phosphors. We further investigate the luminescence by measuring thermoluminescence of the two phosphors. Our spectral results indicate that conventional thermoluminescence measurement cannot directly evaluate the electron population in the traps of Y₃Ga₅O₁₂:Bi³⁺, in which the ultraviolet emission is suppressed at high temperature due to a thermal ionization quenching. We believe that the insight of the present trap performance is transferable to other ultraviolet persistent phosphors.