A giant enhancement in the up-conversion luminescence and high temperature sensitivity of Bi3+ doped ZnMoO4:Er3+ up-conversion phosphor

Abstract

Luminescence intensity is a critical factor for upconversion (UC) oxides with high phonon energy. Herein, an effective enhancement in UC luminescence is achieved in the ZnMoO₄:Er³⁺ phosphor via Bi³⁺ doping. UV-vis-NIR diffuse reflectance spectroscopy verifies the fact that the absorption at 980 nm is enhanced by the introduction of Bi³⁺. The physical mechanism is that Bi³⁺ doping affects the transition probability between the f-levels of Er³⁺. Therefore, the green and red emission intensities are increased 82.4 and 37 times, respectively. The dependence of luminescence intensity on the power of Bi³⁺-doped ZnMoO₄:Er³⁺ combined with density functional theory (DFT) calculations also confirms the proposed energy transfer mechanism. Based on the excellent green emission, the 980 nm excited optical temperature sensing property of the synthesized sample is realized in a wide temperature range by monitoring the intensity of UC luminescence. The theoretically calculated absolute sensitivity of the optical temperature sensor was S_A = 3.04% K⁻¹ at 1253 K. This work paves a new way for enhancing UC luminescence and will arouse extensive interest in noncontact temperature-sensing applications.