B-site Heterovalent Substitution And Mercaptosilane Surface Passivation Of Perovskite Fluorescent Nanocrystals

In recent years,the all inorganic CsPbX₃（X=Cl,Br,I）perovskite nanocrystals prepared by solution method have the advantages of narrow half peak width,high photoluminescence quantum yield and simple synthesis method.However,the lattice structure stability of all inorganic perovskite nanocrystals is poor,and the environmental tolerance to water,light,heat and polar solvents is poor,the phenomenon of fluorescence quenching is easy to appear,which seriously hinders the further application and development of nanocrystals.In this paper,we use the hot injection method to synthesize ABX₃cubic perovskite nanocrystals.Through the regulation of ion doping concentration and ligand passivation,the photoluminescence quantum yield（Photoluminescence Quantum Yield,PLQY）,photothermal stability and air stability of the nanocrystals are further improved.The main contents of this paper are as follows:（1）CsPb（Cl/Br）₃NCs and Pr³⁺doped nanocrystals were synthesized by hot injection method.Pr³⁺doped nanocrystals were recorded as Pr-CsPb（Cl/Br）₃NCs.PLQY of pure CsPb（Cl/Br）₃NCs with emission wavelength of 480nm is 21%,and that of Pr-CsPb（Cl/Br）₃NCs is 59%at 489 nm,and the fluorescence efficiency is improved,but the effect is not ideal.The Cs₃PrCl₆NCs and CsPbBr₃NCs were synthesized by hot injection method.The mixture of Cs₃PrCl₆NCs and CsPbBr₃NCs by one-step mixing method.Pr-CsPb（Cl/Br）₃NCs with emission wavelength of 410nm-490 nm was obtained,covering the whole blue light band.The PLQY of Pr-CsPb（Cl/Br）₃NCs is 85%at 490 nm,which was higher than that of pure CsPb（Cl/Br）₃NCs and Pr-CsPb（Cl/Br）₃NCs prepared by hot injection.（2）All inorganic perovskite CsPbBr₃NCs were synthesized by hot injection method.3-Mercaptopropylt rimethoxysilane（MPTMS）was used as a ligand for ligand exchange in nanocrystals.The nanocrystals prepared after the ligand exchange were recorded as ExMP-CsPbBr₃NCs.The PLQY of ExMP-CsPbBr₃NCs is 99%,and the morphology is more uniform,the absorption intensity is 2.5 times of pure CsPbBr₃NCs.The two nanocrystalline solutions were stored in air for 40 days,the PLQY of pure CsPbBr₃NCs decreased to 31%of the original,while that of ExMP-CsPbBr₃NCs remained 89%of the original,and the air stability was significantly improved.（3）The ExMP-CsPbBr₃NCs prepared under the optimum conditions were further mixed with Cs₃PrCl₆NCs to prepare Pr-ExMP-CsPb（Cl/Br）₃NCs by one-step mixing method.Compared with Pr-CsPb（Cl/Br）₃NCs,the peak PLQY of Pr-ExMP-CsPb（Cl/Br）₃NCs appears at a shorter wavelength（464 nm）,and the corresponding PLQY is 88%.