Study On The Growth,preparation,control And Photoelectric Properties Of All-inorganic Perovskite CsPbBr₃ Crystal

Perovskite material is a kind of semiconductor material with great potential emerging in recent years,and it has important applications in the field of optoelectronics,relying on its excellent optoelectronic properties.The all-inorganic perovskite CsPbX₃（X=Cl,Br,I）,as an important type,enjoys the advantages of high photoelectric performance and also makes up for the shortcomings of poor tolerance of hybrid perovskites due to containing organic molecular groups,and attracting a lot of research attention.As the core material and decisive part of optoelectronic devices,it directly affects the generation,migration,and recombination processes of carriers in the device.As a new type of semiconductor material,just like the challenges encountered in the development process of traditional semiconductor materials,how to prepare high-quality samples determines the application and upper limitation of the material,also guides the study of the intrinsic material characteristics and the device performance.A lot of research work has successfully prepared all-inorganic perovskite,but the still have problems such as small grain size,low crystal quality,high grain boundary density and defect density,which limit the performance of all-inorganic perovskite-based optoelectronic devices,especially in some special optoelectronic devices,such as high-energy radiation single-photon detectors,in which defects will greatly affect the collection and detection of precision photocurrent signals.Therefore,efforts and breakthroughs are still needed to improve the quality of materials.The growth and preparation of high-quality all-inorganic CsPbX₃ perovskite with large grain size,high film coverage,high crystallinity,complete crystal structure,low grain boundary density and low defect density is still an important issue that needs to be solved urgently.This thesis focuses on the growth and preparation of high-quality all-inorganic CsPbX₃ perovskite for the application requirements of high-performance optoelectronic devices.The focus is on the solution method and chemical vapor deposition（CVD）preparation of all-inorganic perovskite CsPbBr₃ semiconductor materials.Here successfully prepared all-inorganic perovskite CsPbBr₃ quantum dots,thin films and single crystals through different solution system designs and preparation methods;through the analysis of the crystal growth theory,combined with the control of experimental parameters,using CVD method successfully achieved the millimeter lateral size all-inorganic perovskite CsPbBr₃ single crystal film,the millimeter size single crystal film used on a specially designed planar PIN diode to verify the effect of material quality and the photoelectric performance of the device.The main work of the thesis is as follows:（1）The all-inorganic perovskite CsPbBr₃ quantum dots,thin films and single crystals were successfully prepared by the solution method.The crystal structure,optical properties and stability properties of materials with different morphologies were studied.For CsPbBr₃ quantum dots,the instability problem caused by the ligand connection was verified;for CsPbBr₃ thin film prepared by spin coating,the size and quality of the crystal grains on the film are adjusted under the influence of the substrate temperature controlled;the crystal structure and optical properties of the CsPbBr₃single crystal grown by two solution crystallization methods are also compared.（2）By coordinating the experimental parameters of the CVD method,a high-quality all-inorganic perovskite CsPbBr₃ single crystal film with millimeters size grain was successfully grown for the first time.The grown single crystal grain exhibits excellent crystal quality.The influence of various experimental parameters on the growth of perovskite materials was further studied.A detailed analysis and verification was made from the crystallization kinetics and crystal growth mechanism,and the influence of gas flow rate,deposition position,and temperature on the crystal structure and morphology of the material were researched.（3）Based on the large-size all-inorganic perovskite CsPbBr₃ single crystal grains grown by the CVD method,a planar PIN diode based on the Schottky junction was fabricated.By comparing large-size single crystal devices with higher open circuit voltage V_OC（750 m V,50%increased）and higher short-circuit current J_SC（more than 3times increase）that are superior to small crystal devices,it is verified that high-quality materials are decisive for device performance.The influence proves that reducing the defect density and grain boundary density of the film will have better carrier transport characteristics.Optoelectronic devices based on all-inorganic perovskite single crystal have verified that all-inorganic perovskite CsPbBr₃ materials have great potential to be used in high-efficiency optoelectronic devices.