Dual-excited anti-thermal quenching in SrGa ₁₂ O ₁₉ : Er ³⁺ , Yb ³⁺ , Cr ³⁺ phosphors: from thermochromism to NIR luminescence

Conventional phosphors suffer from thermal quenching, i.e., the loss of emission intensity with rising temperature. A promising, yet emerging solution is a new class of materials called anti-thermal quenching (ATQ) phosphors, capable of avoiding this issue and thus succeeding in applications where higher temperatures are expected. In this study, SrGa₁₂O₁₉: Er³⁺, Yb³⁺, Cr³⁺ phosphors were designed to display dual-excited ATQ. Under 980 nm excitation, the Yb/Er upconversion process causes the Yb³⁺→Er³⁺→Cr³⁺ energy transfer, resulting in a 2.7-fold Cr³⁺ intensity enhancement and an <i>S_r-</i>_max of 2.88% K^-1 at 480 K. Moreover, co-modulating excitation wavelength and thermal stimulation leads to a gradual change in the emission color from green to orange-red, which is an interesting feature for anti-counterfeiting optical markers. Finally, the downshifting process under 468 nm excitation triggers a reverse Cr³⁺→Er³⁺/Yb³⁺ energy transfer process. This efficient conversion from UV-visible light to NIR radiation shows high application potential in solar cells and LED devices.