| Nowadays,in the field of next-generation semiconductor materials,perovskite nanocrystals have received unprecedented attention due to their excellent optoelectronic properties,such as tunable emission spectrum over the entire visible region,narrow full-width at half maximum(FWHM),high photoluminescence yields(PLQYs),high absorption coefficient.The control of shape and precise preparation is an effective way to adjust the luminescence performance of perovskite nanocrystals.By inhibiting the growth of perovskite nuclei,two-dimensional perovskite structures that the thickness is close to the atomic level in a certain dimension can be formed,such as nanoplates,nanosheets,etc.Two-dimensional perovskite nanocrystals,while maintaining the excellent optoelectronic properties of the perovskite nanocrystals,also show a series of novel properties,such as large optical absorption cross section,high carrier mobility,and significantly polarized emission.These excellent characteristics make two-dimensional perovskite nanocrystals have a wide range of applications in the fields of photodetectors and lasers.So far,there are still some problems in the synthesis and photoelectric properties of two-dimensional CsPbBr3 nanocrystals.First of all,the precise control of the thickness of CsPbBr3 nanoplates is difficult,and the products often compose of nanoplates of different thicknesses,which in turn leads to broadening of the emission spectrum.Secondly,there is little synthesis and research on thinner(?2 ML)CsPbBr3 nanoplates.Moreover,there are few studies on the synthesis mechanism of CsPbBr3 nanoplates,and the mechanism of orientation growth of crystal nuclei on different crystal planes is not clear.Based on the above problems,this paper devises a method that can precisely adjust the thickness of the nanoplates.By introducing FeBr3,ultra-thin(2 ML)and uniform CsPbBr3 nanoplates are synthesized.This paper is divided into the following two parts:(1)The luminescent properties and structural characterization of CsPbBr3 nanoplates.Compared with the green emission of cubic CsPbBr3 nanocrystals,these ultra-thin CsPbBr3 nanoplates(only 4.4 nm)exhibit a strong quantum confinement effect.The emission peak position is significantly blue-shifted,and the half-width is narrower.This paper characterizes its special luminescence performance by means of fluorescence spectroscopy,fluorescence quantum efficiency and fluorescence lifetime.The CsPbBr3 nanoplates also exhibite strong self-assembly behavior under certain conditions.The nanoplates tend to spontaneously form a face-to-face state,and stack to each other with their edges perpendicularly to the substrate.In this paper,TEM,XRD,SAXS and other methods are used to characterize its morphology and analyze the characteristics of its self-assembled structure.XPS,EDS and infrared absorption spectroscopy are used to characterize the element distribution and structural characteristics of the nanoplates.(2)Study on the mechanism of introducing FeBr3 to synthesize CsPbBr3 nanoplates.This paper systematically studies the synthesis mechanism of the ultra-thin CsPbBr3 nanoplates through the analysis of experimental synthesis,purification process and by-products,combined with EDS mapping,XPS and other characterization methods to exclude the possibility of Fe3+ion doping into the perovskite lattice.This article also set up a series of comparative experiments of adding OLA-HBr,Fe(OA)3 and other metal bromide MBrx,and characterized their experimental products.Finally this paper summarizes the mechanism of introducing FeBr3 to form CsPbBr3 nanoplates:the protonated oleylamine generated from the decomposition of FeBr3 replaces the Cs+ion on the surface of the perovskite structure,blocking the three-dimensional growth of the perovskite crystal nuclei,thereby forming a two-dimensional nanoplate structure. |
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