Upconverting temperature sensors with high activation energy and low pump threshold

The structural and optical properties of Er3+/Yb3+/Mo6+-codoped aurivillius-structured Bi2WO6 phosphors are reported. Simultaneous substitution of Bi3+ and W6+ by Er3+/Yb3+ and Mo6+ ions in a codoped phosphor was explored for photoluminescence study. The green emission was enhanced with the codoping of Yb3+ as well as Mo6+ ions in Er3+:Bi2WO6 phosphors. In the Er3+/Yb3+/Mo6+-codoped Bi2WO6 phosphors, the Yb3+-MoO42- dimer state transfers its energy to Er3+ ions and is found responsible for the enhancement. The luminescence saturation processes with increased photon density have been discussed using rate equations. The H-2(11/2) and S-4(3/2) energy levels of Er3+ ions are adapted for optical thermometry. The absolute and relative sensitivities were found with a resolution of 0.38 K at room temperature and repeatability cycles of FIR. The thermal stability has been verified with the Arrhenius equation.