| Lead halide perovskites possess excellent properties,including high carrier mobility,tunable emission wavelength,narrow emission peak,and high quantum yield,which is a kind of remarkable semiconductor been widely researched and used in photovoltaic,lighting and display fields,and so on.However,it still faces the two severe challenges of lead toxicity and poor stability,which limit its application in real life.Thus,it is necessary and significant to develop and synthesize stable and efficient new kinds of perovskite materials.Compared with the high-temperature hydrothermal method,the anti-solvent method can synthesize high-quality single crystals under room temperature and atmospheric pressure.Also,it can help us observe the whole process of the growth of single crystals,which is conductive to in-depth study of the single crystal growth process.In addition,the synthesized single crystal is more conducive to phase identification of the product and discovery of new materials and structures.In recent years,transition metal perovskite variants represented by Cu have been reported to have outstanding optoelectronic properties due to the reorganization of lowdimensional electronic structure and excited state structure,but they are still limited to the study of Cs3Cu2I5.At the same time,studies have found that Ag elements,which is of the same family as Cu element,are easy to form[AgCl6]5-octahedrons in perovskite materials and cause self-trapped excitons emission.However,those researches are mainly focused on double perovskite materials.There are few studies on Ag-based halide perovskites.Based on the above discussion,the thesis uses anti-solvent method to synthesis stable all-inorganic lead-free halide perovskite variants——CsAgCl2 and Cs2AgCl3 single crystals and Cs3Cu2I5 powders,which advances the research on transition metal halide perovskite materials.The main research contents and results are as follows:(1)The ultra-broadband orange luminescent all-inorganic low-dimensional leadfree perovskite variant CsAgCl2 single crystal was prepared by anti-solvent vapor diffusion method,of which emission peak at 615 nm and full width at half maxima(FWHM)of 245 nm.Through the study of luminescence properties like fluorescence spectrum,quantum efficiency and fluorescence lifetime,it is found that 2D CsAgCl2 exhibits stronger localization,greater Stokes shift,and wider FWHM,compared with traditional 3D lead-based perovskites.In this paper,we use single crystal X-ray diffraction,structure refinement and scanning electron microscopy to analyze its structure and morphology and evaluate its long-term storage stability and thermal quenching performance.Low-temperature variable-temperature spectroscopy and firstprinciples calculations are used to deeply study its luminescence mechanism,and finally attributed to self-trapped exciton emission caused by the distortion of[AgCl5]4polyhedral.(2)Cs2AgCl3 single crystals and Cs3Cu2Cl5 powders were prepared by a method similar to the synthesis of CsAgCl2 single crystals.Both materials can emit broadband green light with a peak at 520 nm and a FWHM of about 100 nm under ultraviolet light excitation of 254 nm ultraviolet light.In this paper,through the analysis of the synthesis process and by-products,combined with scanning electron microscopy,XRD and other methods,the factors affecting the crystal quality and the reasons for the existence of impurity phases are discussed.At the same time,through a series of characterization methods,the micro morphology and optical properties of Cs2AgCl3 single crystals and Cs3Cu2Cl5 powders were studied,which provided a realistic basis for the expansion of lead-free perovskite material family members and related properties. |
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