Persistent luminescence mechanism of Gd3+ inScPO4

Persistent luminescence (PersL) is an important and interesting optical phenomenon. However, the popular valence-alternation theory struggles to elucidate the PersL mechanism of Gd 3+ due to its highly stable +3 oxidation state. Here, by using the X-ray Absorption Near Edge Structure (XANES), we confirm the stable valence state of Gd 3+ in ScPO 4 , thus providing evidence to exclude the valence-alternation model for explaining the PersL of Gd 3+ in ScPO 4 . Comparative experiments on the photoluminescence and PersL spectra between ScPO 4 and Gd 3+ -doped ScPO 4 confirm the energy transfer from the self-trapped excitons of ScPO 4 to Gd 3+ . Further density functional theory (DFT) calculations reveal that Gd 3+ doping enhances the orbital hybridization between Gd 3+ and O 2− , thereby modifying the electronic structure, which likely facilitates the confinement of self-trapped excitons.