| Inorganic perovskite with lead and halide generally refers to a compound that composed of Cs,Pb and halogen(Cl,Br,I)in a certain proportion,it has the advantages of simple preparation process,low cost,high fluorescence quantum efficiency,wide color gamut and narrow luminescence peak,which make it have a wide range of applications in the field of light-emitting diodes,photodetectors and solar cells,but its toxicity and low stability limit its practical application.In this thesis,ion exchange between Mn2+ and Pb2+ in different perovskite systems was carried out by controlling the reaction conditions,and the mechanism of ion exchange was studied.It can not only reduce the content of Pb2+ ions and reduce the toxicity,but also can control the fluorescence color.The main work is as follows:(1)We first synthesized the samples of CsPbCl3:xmol%Mn2+ by hot injection method at 150℃.Then we analyzed the morphology,the crystalline phase and fluorescence spectra of the samples.The results show that the samples doped with different concentrations of Mn2+ ions show a tetragonal crystal structure with uniform grain distribution.Under the excitation of 365nm UV light,the intensity of the exciton emission peak at 400nm increases with the increase of the doping concentration when the initial doping concentration of Mn2+ is less than 40mol%.Meanwhile,when the initial doping concentration is higher than 40mol%,it can be clearly observed the luminescence peak of Mn2+ at around 600nm.At the same time,the maximum replacement rate of Mn2+ reached 10.0%.(2)In order for Mn2+ to replace Pb2+ ions more to reduce the toxicity of perovskite,we synthesized Cs(Pb/Mn)Cl3 nanocrystals by cation exchange method for the first time.And the cation exchange mechanism between Pb2+ and Mn2+ was studied.We designed the following two experimental programs:First,CsPbCl3 perovskites were synthesized,and then the solution of MnCl2 was added into the CsPbCl3 perovskite maintaining the reaction temperature,and we characterized the morphology,crystal phase and fluorescence spectra of the samples of Cs(Pb/Mn)Cl3.The results show that the crystal structure keeps the tetragonal phase structure spectrum with the increase of the reaction time.After Mn2+ was added,the fluorescence of the sample changed from a single luminescence peak to double luminescence peaks under the excitation of 365 nm UV light,and the fluorescence intensity of the Mn2+ luminescence peak increased with the reaction time.From the CIE color chart,it can be intuitively found that the emission color of the samples shows a linear change from blue to orange with the increase of the reaction time.Second,CsMnCl3 nanocrystals were synthesized,and then the solution of PbCl2 was added into the CsMnCl3 nanocrystals,and we characterized the morphology,crystal phase and fluorescence spectra of the samples.The results show that the CsMnCl3b nanocrystal has a hexagonal crystal phase,once the Pb2+ is added,the sample is transformed into a tetragonal crystal phase,and then the crystal phase does not change with the increase of the reaction time.Meanwhile,the maximum replacement rate of Mn2+ reached 24.4%.After Pb2+ ions are added,the spectrum is changed from non-luminescence in the visible range to bimodal emission.With the reaction time increasing,the intensity of the exciton luminescence first increases and then decreases.Finally,the mechanism of cation exchange was analyzed in detail.(3)Cs(Pbi-x/Mnx)(Cl/Br)3 nanocrystals were synthesized by ion exchange method.First,CsPb(Cl/Br)3 perovskite was synthesized,and the morphology,crystal phase and fluorescence spectrum of the sample Cs(Pbi-x/Mnx)(Cl/Br)3,which was prepared after the cation exchange between Mn2+ and CsPb(Cl/Br)3 perovskite,were studied with the reaction time increasing.The results show that with the increase of reaction time,the morphology and crystal phase of the sample did not change.However,the fluorescence spectrum changes from the single luminescence to bioluminescence,and the luminescence intensity of Mn2+ increased gradually. |
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