Reversible Modulated Upconversion Luminescence of MoO3:Yb3+,Er3+ Thermochromic Phosphor for Switching Devices.

Reversible modulation of upconversion luminescence induced by the external field stimuli exhibits potential applications in various fields, such as photoswitches, optical sensing, and optical memory devices. Herein, a new MoO3:Yb3+,Er3+ thermochromic phosphor was synthesized via a high-temperature solid-state method, and the reversible color modification of the MoO3:Yb3+,Er3+ phosphor was obtained by alternating the sintering conditions either in a reducing atmosphere or in air. The color of the MoO3:Yb3+,Er3+ phosphor changed from light-yellow to blue under sintering in the reducing atmosphere and returned back after sintering again in air. The influence of reversible thermochromism on the upconversion luminescence of MoO3:Yb3+,Er3+ phosphor was investigated. The MoO3:Yb3+,Er3+ phosphor prepared in air exhibited visible upconversion luminescence, while the MoO3:Yb3+,Er3+ phosphor has no upconversion luminescence after sintering in the reducing atmosphere. This up-conversion luminescence modulation shows excellent reproducibility after several cycles. The thermochromic MoO3:Yb3+,Er3+ phosphor with reversible modulated upconversion luminescence shows great potential for practical applications in optical switches and optoelectronic multifunctional devices.