Synthesis And Applications Of All Inorganic Caesium Lead Halide Perovskite Composite Materials

In recent years,the all inorganic caesium lead halide perovskite nanocrystals?NCs?,namely CsPbX₃?X=Cl,Br,I?,has been successfully developed,because of their high photoluminescence quantum yield,narrow emission spectrum,adjustable emitting light,and the advantages of wide color gamut.They have been gotten much attention from the global academic and industry researchers.In particularly,comparing with the traditional CdSe,InP quantum dots and organic fluorescent dyes,the CsPbX₃ NCs have a higher fluorescence quantum efficiency and color purity,etc.The CsPbX₃ NCs have a great application prospect in the field of display.However,the CsPbX₃ NCs have not been successfully applied to commercial application due to the limitation of stability.For this purpose,we select and construct the composite materials with different encapsulation structures to improve the stability of the CsPbX₃ NCs,which can provide the basis for their application.The main research contents are as follows:1.By untlizing the halogen exchange,the CsPbBr₃/NH₄Br-AE nanocomposites were prepared by CsPbCl₃ NCs and NH₄Br crystals.The photoluminescence quantum yields?PLQY?of the composite materials can reached to 64.21%and the emitting position was518 nm,with full width at half maximum?FWHM?was 23 nm.Comparing with the pure CsPbBr₃ NCs,the thermal stability and water resistance of CsPbBr₃/NH₄Br-AE were obviously improved.Finally,combining the CsPbBr₃/NH₄Br-AE and the red fluoride phosphor K₂SiF₆:Mn⁴⁺,the white light-emitting diodes?WLED?were successfully obtained with the color coordinate of?0.36,0.35?.2.According with the study of organic phosphate coating to improve the stability of red fluoride phosphor K₂SiF₆:Mn⁴⁺.We developed a simple strategy to synthesize alkyl phosphate encapsulated CsPbBr₃ NCs?CsPbBr₃/TDPA?by using 1-Tetradecylphosphonic acid?TDPA?both as ligand for the CsPbBr₃ NCs and the precursor for alkyl phosphate.The CsPbBr₃/TDPA not only retained high PLQY?68%?and narrow-band emission?FHWM²2 nm?,but also exhibited high stability against water and heat.The relative PL intensity of the CsPbBr₃/TDPA was maintained at 75%or 59%after being dispersed in water for 5 h or heated to 375 K?100??,respectively.Finally,the WLED with a high luminous efficiency of 63 lm/W and wide color gamut?122%of NTSC?was fabricated by using green-emitting CsPbBr₃/TDPA and red-emitting K₂SiF₆:Mn⁴⁺phosphors.The luminous efficiency of the WLEDs maintained at 90%after working under a relative humidity of 60%for 15 h,which showed potential in LCD backlight devices.3.Here,we developed a simple strategy to synthesize CsPbBr₃ embedded in Cs₄PbBr₆?CsPbBr₃/Cs₄PbBr₆?formation of nanocomposites by using 2-Methylimidazole?MeIm?as capping ligands.The MeIm is helpful to dissolve halide salts and stabilize the Cs₄PbBr₆matrix.The component,morphology,and size of the CsPbBr₃/Cs₄PbBr₆ NCs can be controlled by varying the stirring time of precursor.The optimized CsPbBr₃/Cs₄PbBr₆ NCs not only exhibited monodispersity and regular hexagon shape,but also retained high PLQY?83%?in powder form.Moreover,the energy transformation between Cs₄PbBr₆ and CsPbBr₃ NCs has been investigated and a possible mechanism schematic of exciton recombination was presented.Additionally,CsPbBr₃/Cs₄PbBr₆ NCs will rapidly turn into CsPb₂Br₅ NCs after dipping in water.The fluorescence intensity remained at the initial 45%after 5 days in water.And untilizing the harmfulless and water-resistant CsPb₂Br₅ NCs,the living HeLa cells can be successfully labeled.