Optical Properties And Applications Of Perovskite Quantum Dots And Rare Earth Ions Doped Glass

Perovskite quantum dots（PQDs）with advantages of large absorption cross-section,highphotoluminescence quantum yield（PLQY）,short lifetime,narrow full width at half maxima（FWHM）,precisely tunable bandgap,show tremendous potential applications in the fields of lighting,display,solar cells,laser and anti-counterfeiting.However,due to their high surface activity,the factors such as moisture and oxygen easily lead to degradation of PQDs,and the optical performance will be sereiously deteriorated,which significantly limits their practical applications.In order to solve this problem,we intend to embed PQDs into stable inorganic oxide glass matrix,which enables PQDs to isolate from the external environment and maintain excellent optical properties.In addition,rare earth（RE）ions have many advantages,such as multiple transition energy levels,wide luminescence wavelength range,long fluorescence lifetime and extremely narrow luminescence band,etc.If we can realize the co-doping of PQDs and RE ions in glass matrix,it is expected to improve the optical properties of PQDs composites and expand their application fields.Therefore,the RE(Eu³⁺,Tm³⁺,Yb³⁺,etc.)and CsPbBr₃ PQDs doped glasses were prepared by in-situ glass crystallization.By combining theoretical calculation with experimental method,the microstructure and luminescence properties of PQDs and RE doped glass nanocomposites were systematically studied,and their potential applications in fluorescence temperature sensing and luminescent anti-counterfeiting were explored.The specific research contents and results are as follows:1.The composition and technological parameters of in situ crystallization synthesis of CsPbBr₃ perovskite quantum dot-embedded glasses were explored and CsPbBr₃ PQDs embedded tellurite glasses and germanate glasses were successfully achieved by controlling precursor glass compositions,melting temperatures and heat treatment conditions.Then,the glass microstructure and optical properties were of the CsPbBr₃ PQDs were studied by XRD spectroscopy,absorption,excitation and emission spectra.By using the quasi-harmonic approximation theory of the temperature-dependence of the bandgap,the microscopic mechanism of PQDs emission dependent on temperature was analyzed in detail.The results show that the nonlinear relationship between emission peak energy and temperature is caused by the competitive behavior between thermal expansion and electron-phonon interaction.2.Eu³⁺-doped tellurite glasses embedding CsPbBr₃ PQDs were successfully prepared,photoluminescence（PL）properties of CsPbBr₃PQDs were analyzed,while the optical temperature sensing properties of the material were studied by fluorescence intensity ratio（FIR）technology.The results show that the obtained nanocomposite exhibited excellent temperature sensing performance in the temperature range of 93-383 K,and the maximal absolute and relative temperature sensitivities are determined to be 0.0224 K^-1 and 2.25%K^-1,respectively.It is expected that this preliminary study will offer a significant advance in exploring novel quantum dots/rare earth ions-based self-calibrated optical thermometric media.3.A novel dual-phase glass containing Tm:NaYbF₄ upconverting nanocrystals（UCNCs）and CsPbBr₃ PQDs has been fabricated.Then,the precipitation rule of dual-phase glass was investigated by adjusting the glass component and rare earth doped fluoride concentration,and the upconversion luminescence kinetic process and performance of the glass were studied.The results indicate that the glass component has a significant effect on the growth of NaYbF₄ UCNCs and CsPbBr₃ PQDs,and the increase of Yb F₃ content promotes the growth of CsPbBr₃ PQDs and improves their photoluminescence quantum yield.Under the irradiation of 980nm near-infrared laser,the dual-phase glass realized the upconversion of Tm:NaYbF₄ nanocrystals,and simultaneously produced the perovskite quantum dot exciton emission at 523nm,which mechanism was evidenced to be radiative energy transfer（ET）from Tm³⁺:¹G₄ state to PQDs.4.The temperature sensing characteristics of the dual-phase glass containing Tm:NaYbF₄ UCNCs and CsPbBr₃ PQDs were studied using FIR technology.And the effect of temperature on the upconversion luminescence was analyzed by temperature-sensitive UC emission spectra of the Tm:NaYbF₄/CsPbBr₃dual-phase glass under 980 nm laser excitation.The results show that the UC emission intensity of CsPbBr₃ PQDs decreases significantly with the increase of temperature,while the emission intensity of Tm³⁺477 nm remains almost unchanged.Moreover,the emission intensity of Tm³⁺650nm and 707nm show an opposite trend with the increase of temperature.By fitting the curves of FIR1(I_PQDs/I477 nm)and FIR2(I707 nm/I_{650 nm})versus temperature,we calculated their maximum absolute sensitivity and relative sensitivity respectively,it shows that FIR1 has high sensitivity in low temperature region（100～300 K）and FIR2 has high sensitivity in high temperature region（300～700 K）.In addition,a real-time temperature measurement system was designed to realize temperature calibration,which provides a beneficial theoretical and experimental basis for the application of rare earth doped dual-phase glass containd PQDs and fluoride UCNCs in temperature sensors.5.Luminescent anti-counterfeiting characteristics of the dual-phase glass containing Tm:NaYbF₄ UCNCs and CsPbBr₃ PQDs were studied.By measuring the UC spectra of Tm:NaYbF₄/CsPbBr₃ dual-phase glass under single excitation of 980 nm and double excitation of 980 nm and 365 nm,the effects of excitation wavelenth and excitation power on luminescence performance were analyzed.The results show that when the excitation wavelength and its power are regulated,the combined color of upconverting and downshifting（UC/DS）emissionsin of the dual-phase glass can be be tuned and its dual mode emission can be raalized.Therefore,we adopt the screen printing technology to prepare anti-counterfeiting patterns and realize unique anti-counterfeiting applications.