Cryogenic Dependent Energy Manipulation in Nonthermally Coupled Levels for Multicolor Upconversion Luminescence

Rational design of multicolor upconversion (UC) luminescent to achieve cryogenic optical thermometers holds exotic potential applications in many high-tech fields. Here, a strategy is proposed to design multicolor UC luminescence by thermally manipulating the electronic transition process, which could be used to achieve optical temperature sensing. The nonthermally coupled energy levels could control the emission intensity of the corresponding energy levels through the nonradiative relaxation process, thus allowing for achieving high sensitivity cryogenic sensing. The Er3+-doped material exhibited thermochromic luminescence properties due to the unique thermal response mechanism, which enables the creation of novel multimode temperature measurements of visual reading and digital recognition. These results not only shed new insights on the luminescence mechanism under specific excitation conditions but also offer a novel strategy for the realization of cryogenic optical thermometers.