Upconversion Charging‐Induced Near‐Infrared Persistent Luminescence for Simultaneous Imaging and Temperature Sensing

Current imaging and temperature sensing techniques utilizing persistent phosphors face a trade‐off between charging efficiency and charging wavelength, particularly hinders biomedical applications, due to the limitations of conventional charging modes. Here, we introduce the upconversion charging (UCC) technique to balance high‐efficiency and long‐wavelength charging, using β ‐Ga 2 O 3 :Cr 3+ as a representative persistent phosphor to realize effective UCC at wavelengths within the bio‐window. Spectroscopic studies reveal that the phosphor can be charged not only via ultraviolet photoionization but also through two‐photon UCC with the Cr 3+ 4 T 2 / 2 E level acting as an intermediate state, thereby extending the charging wavelength into the bio‐window. Quantum tunneling is found to dominate the long‐lasting persistent luminescence (PersL) output, broadening the time window for readout imaging and temperature signals. Three linearized thermal response parameters based on temperature‐dependent Cr 3+ PersL spectra are synergistically optimized via multiple linear regression analysis, achieving orders‐of‐magnitude improvements in relative sensitivity and temperature uncertainty. The potential of UCC‐induced PersL for simultaneous imaging and temperature sensing is demonstrated. Our work opens new perspectives for the long‐wavelength high‐efficiency charging and multifunctional applications of persistent phosphors.