| Synchrotron-based technologies have unique advantages in characterization of the material structure.Synchrotron X-ray diffraction(XRD)present a remarkable ability to detect the structure of crystalline materialswith the advantages of non-distructive characterization and quantitative analysis,especially for low-dimentional andmetastable materails.Besides,in-situ or in-operandosynchrotron X-ray diffraction can efficiently reveal the structure revolution which can benefit to better understand the dynamic process of materials in use;Synchrotron coherent X-ray diffraction imaging(or Ptychography)is a new type imaging technology,which can provide a much higher spatial resolution on morphological and chemical state detection.This method is regarded asthe future of sychrontron-based imaging techniques since it is independent of the X-ray focusing opticsand can obtain a nearly diffraction-limited spatial resolution.This thesis can be divided into two parts.In the first part,series of research works have been carried out by using synchrotron radiation X-ray diffraction technologyand lots of achievements are abtained.For instance,the stablitliy problem of organometallic halide perovskite CH3NH3PbI3 in humidity environment was studied,and the lattice strain effect on photoluminesence of colloidal CsPbBr3 nanocrystals was investigated,and also the phase transformation of CsBr-PbBr2 system reaction products was characterized.In the second part,aimed at the low speed of Ptychography,the fast Ptychography method was developedwhich focus on the realization of fast scan trajectory and the exploration of combined spectroscopy imagingmethod.The main contents of this thesis are listed as follows:Chapter 1,in the introduction part,the classificationof structure and characterization methods are briefly introduced.Therein,the advantages of synchrotron-based characterization methods are emphasized.In the end,the research content of this paper is introduced.Chapter 2,the fundamental theory of synchrotron X-ray diffraction and coherent X-ray diffraction imaging are introduced in detail.Chapter 3,with combination ofsynchrotron X-ray diffraction and other characterizationmethods,the decomposition mechanism of organometallic halide CH3NH3PbI3 in humidity environment was revealed.It was comfirmed that there is a mesophase CH3NH3PbI3·H2O during thehydrolysis and this hydrolysis process is not completely reversible.Chapter 4,with combination of synchrotron X-ray diffraction and other characterization methods,the reaction mechanism of CsBr-PbBr2 system in the different reaction solvent as well as the phase transformation of the reaction productswere systematically studied.The experimental results make it clear that the coordination condition of Pb in the solvent plays a significant role in the formation of reaction products.Following this theory,the phase transformation among Cs4PbBr6?CsPbBr3 and CsPb2Br5 was realized by the chemical selectivity of water.Charpter 5,taking advantages of high resolution synchrotron XRD and transient spectroscopic measurements,we studied the great disparity in photoluminesence quantum yields(PLQY)of colloidal CsPbBr3 nanocrystals with varied shape.We proposed and verified the viewpoint that the lattice strain will induce the formation of defects and therefore decrease the PLQY.Charpter 6,based on the scanning system in COSMIC imaging endstation of Advanced Light Source(ALS),multiple scanning trajectories were developed,like concentric scan,spiral scan,continuous scan,etc.To make Ptychography more efficient,firstly we optimized the ptychography scan trajectory utilizing scanning transmission X-ray micorscopy(STXM)image.In addition,using the STXM and Ptychography,a combined spectroscopy imaging method and the related data analysis method were developed.Charpter 7,the work of this thesiswas briefly summarized,and the outlook of further development of synchrotron XRD and Ptychograpy was put forword. |
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