A Novel Oxygen Vacancy in ScPO₄:Er for Luminescence Anti-Thermal Quenching

Different from previously reported shallow defects in ScPO₄, herein we have uncovered a deep defect, oxygen vacancy (V_O). The perfect energy level match with ⁴S_3/2/⁴F_9/2 in doped Er³⁺ allows V_O to accept and store the excitation energy transferred from Er³⁺, which is then released and back-transferred to Er³⁺ upon heating, and finally leads to significant luminescence anti-thermal quenching (LATQ). Moreover, the concentration of V_O can be adjusted by simple atmospheric annealing, which allows modulation of V_O → Er³⁺ energy transfer for adjustable LATQ in ScPO₄:Er, i.e., downshifting LATQ up to 843 K and upconversion LATQ till a record-high temperature of 1323 K, and thus unparalleled performance of the classic compound ScPO₄:Er in thermophotovoltaics (TPV) and dual-mode luminescence thermometers.