Compensation effect of electron traps for enhanced fluorescence intensity ratio thermometry performance

Abstract

How electron traps in a host matrix impact the fluorescence intensity ratio (FIR) thermometry performance in inorganic phosphors is still unclear. In this work, relationships between temperature-dependent photoluminescence, fluorescence intensity ratio-based optical thermometry performance, and concentration of the electron traps have been thoroughly investigated in a Mn-doped ZnGa₂O₄ spinel system. The results reveal that the sample with a higher concentration of electron traps shows a thermometry sensitivity (S_r) of 3.47% K⁻¹ read from the FIR of the green channel (Mn²⁺) and the red channel (Mn⁴⁺), which is over twice higher than that of the sample with a lower concentration of electron traps. Detailed photoluminescence, thermoluminescence, and first-principles calculations demonstrate that the performance enhancement is dominantly caused by a selective thermally induced emission compensation through the antisite defects in the ZnGa₂O₄ host. The defects act as electron traps and compensate for the intensity decline of the green channel by releasing electrons at high temperatures while leaving the red channel unaffected, thus increasing the FIR value and the sensitivity. This work shows a significant enhancement effect of the electron traps on the FIR thermometry performance in ZnGa₂O₄:Mn and provides a novel strategy for thermometry performance enhancement through the manipulation of traps.