Anion Exchange Synthesis And Photoluminescence Mechanism Of Manganese Doped Inorganic Perovskite Quantum Dots

In recent years,lead halide perovskite quantum dots have attracted extensive attention,especially cesium lead halide perovskite quantum dots,which have excellent charge transport,high luminescence stability,high luminescence efficiency and narrow emission width.The band gap can be adjusted by changing the composition which can tune the luminescence peak of the quantum dots in the whole visible region.Therefore,they have a wide range of practical applications in solar cells,light-emitting diodes and lasers,etc.The lead halide perovskite quantum dots have weak quantum confinement effect,which reduce the influence of size heterogeneity and defects of surface states on their luminescence properties.However,the perovskite materials are kind of ionic crystals and their crystal structure is not very stable.And it is easy to be decomposed under oxygen,water,temperature,and light,which greatly limits the practical application of perovskite materials.Therefore,improving the stability of perovskite quantum dots is crucial for development of perovskite quantum dots.Doping impurity ions has been considered as a promising method to control the electronic,magnetic,and optical performances of perovskite quantum dots.Recently,several successful substitutions of Pb²⁺with transition metal ions have been reported for cesium lead halide perovskite quantum dots,such as Mn²⁺,Zn²⁺,and Sn²⁺,which can effectively improve the stability and luminescence efficiencies of perovskite quantum dots.In this work,we successfully synthesized Mn²⁺:CsPbCl_3-xBr_x perovskite quantum dots by hot injection and anion exchange method.We also systematically revealed the temperature-dependent energy transfer process betweent excitons and doped ions.Furthermore,Mn²⁺:CsPbCl_3-xBr_x/Cs₄PbCl₆ core-shell quantum dots were further synthesized and the edge luminescence around 450 nm and strong luminescence of Mn²⁺were obtained.The following results were obtained:1?Mn²⁺:CsPbCl₃ perovskite quantum dots were synthesized by high temperature thermal injection method,and the optimal synthesis ratio was found by adjusting the doping concentration of Mn ions,the amount of ligands and the synthesis temperature.The optimum synthetic efficiency was about 63%.On the basis of the previous study in our group,a series of Mn²⁺:CsPbCl_3-xBr_x perovskite quantum dots with different Br contents were synthesized by anion exchange method.A series of Mn²⁺:CsPbCl_3-xBr_x perovskite quantum dots with edge luminescence from 405 nm to about 500 nm and absorption from 395 nm to 480 nm were obtained.The luminescence of Mn²⁺did not shift.When the Cl/Br ratio was 2.15:0.85,the luminescence of Mn²⁺reached the maximum value and then decreased,indicating that Mn²⁺ions competed with the luminescence process of band excitons and the relaxation process was dependent on Br component.We obtained perovskite quantum dots with high luminescence efficiency at different peak wavelengths by adjusting the content of doped anion Br-and the concentration of Mn ions.The doped quantum dots can be further applied to the production of white LEDs.2?In this work,we investigated the luminescence properties and temperature dependent exciton dopant energy transfer in Mn²⁺doped CsPbCl_3-xBr_x with various composition x of Br by steady-state and time-resolved PL spectroscopy.The Mn²⁺doped perovskite quantum dots with varied Br^-contents were synthesized via post-synthetic halide anion exchange.The effects of the Br composition on the PL spectra and PL decays of Mn²⁺:CsPbCl_3-xBr_x NCs were studied at temperature ranging from 80 to 300 K.The luminescence mechanism of Mn²⁺:CsPbCl_3-xBr_x nanocrystals was discussed.3?Mn²⁺:CsPbCl_3-xBr_x/Cs₄PbCl₆ core-shell quantum dots were successfully fabricated.The luminescence mechanism of Mn²⁺:CsPbCl_3-xBr_x/Cs₄PbCl₆ core-shell quantum dots with different contents of Br was also studied by the steady state and time-resolved luminescence spectroscopy.The luminescence performance was further improved by applying the core-shell structure of C Mn²⁺:CsPbCl_3-xBr_x/Cs₄PbCl₆ which provided a good basis for the preparation of light emitting diode.