Photoluminescence And Temperature Sensing Properties Of Rare Earth Doped Cs₂Ag（Na）In（Bi）Cl₆ Microcrystal

As an important basic physical parameter,the accurate measurement of temperature has a pivotal role in aerospace,electronics,industrial manufacturing,and scientific experiments.Optical temperature sensing of rare-earth ions doped perovskite based on fluorescence intensity ratio and fluorescence lifetime thermometric measurement has rapidly become a hot research topic in the field of thermometry because of its superior strong anti-interference capability,high sensitivity,and fast response.However,most of the rare-earth doped fluorescence materials used for temperature sensing contain Pb²⁺,which makes the material itself toxic and unstable,and the studies have focused on the up-conversion photoluminescence of rare-earth ions,while ignoring the down-conversion photoluminescence properties of rare-earth ions themselves,and the photoluminescence mechanism of which is still unclear,so it is urgent and necessary to study the multimodal thermometry and photoluminescence mechanism based on rare-earth doped lead-free perovskites.The study of multi-mode temperature sensing and photoluminescence mechanisms based on rare-earth ions doped lead-free perovskites was urgent and necessary.The research in this dissertition specifically includes the following as,Firstly,the problems of toxicity and instability as well as single mode photoluminescence of rare-arth doped perovskites photoluminescence materials were contested.We used an improved hydrothermal method to synthesize low toxicity,stable performance and dual-mode photoluminescence of rare-earth ions(Er³⁺,Ho³⁺,Yb³⁺)doped lead-free halogenated perovskite of Cs₂Ag_0.6Na_0.4In_0.9Bi_0.1Cl₆（abbreviated as CANIBC）microcrystals,and made the perovskite free of toxic Pb²⁺by elemental substitution,and test characterization by X-ray diffractometer,energy spectrometer and photoelectron spectrometer proved the successful doping of rare-earth ions into CANIBC microcrystals,and the good physicochemical stability of CANIBC microcrystals by water and thermal stability.Under 405 and 980 nm laser excitation,the CANIBC microcrystals showed yellow and green emission,and the down/up dual-mode photoluminescence of rare-earth ions was achieved.Second,the optical temperature sensing of rare-earth doped perovskite photoluminescence materials is mostly based on a single temperature measurement mode,down/up conversion photoluminescence based on Er³⁺/Yb³⁺and Ho³⁺/Yb³⁺co-doped CANIBC microcrystals was explored for temperature sensing characteristics and thermometric sensitivity.For the Er³⁺/Yb³⁺co-doped CANIBC microcrystals,the maximum relative and absolute sensitivity values of 1.37%K^-1 and 3.5×10^-2 K^-1 are obtained in the down-conversion photoluminescence using fluorescence intensity ratio thermometric method;In the up-conversion photoluminescence,the maximum relative and absolute sensitivity values of 8.7×10^-1%K^-1and 2.8×10^-2ms·K^-1 are obtained based on fluorescence lifetime thermometric method,respectively.Based on the fluorescence intensity ratio thermometric method,the maximum relative and absolute sensitivity values of 1.05%K^-1 and 7.4×10^-3 K^-1 can be obtained,respectively;For Ho³⁺/Yb³⁺co-doped CANIBC microcrystals,the maximum relative and absolute sensitivity values of7.4×10^-1%K^-1 and 1.3×10^-3 K^-1 can be obtained in the down-conversion photoluminescence using the fluorescence intensity ratio temperature thermometric method.In the upconversion photoluminescence,the maximum relative and absolute sensitivity values of 1.4×10^-1%K^-1and 5.11×10^-2K^-1 can be obtained using the fluorescence intensity ratio temperature thermometric method.The values of relative and absolute sensitivity were improved compared to the reported fluorescent temperature sensing materials.Finally,the problem of unclear mechanism in the dual-mode photoluminescence process of rare-earth doped perovskite is contested.The role of CANIBC microcrystals in the dual-mode photoluminescence process was analyzed using time-resolved spectroscopy,and it was demonstrated that there is energy transfer from CANIBC microcrystals to rare-earth ions in the down-conversion photoluminescence process,while there is only energy transfer between rare-earth ions in the up-conversion photoluminescence process.