Structure Design,Optoelectronic Properties Of Novel Perovskite-based Materials And Photon Detection Imaging Application

With the escalating energy crisis and environmental issues,the development of novel energy technologies becomes increasingly crucial.Against this backdrop,the large-scale industrialization of photovoltaic cells based on low-cost and easily processable perovskite materials has become a highly regarded field,showing strong momentum in its development.In addition to photovoltaic cells,research on perovskite materials in fields such as LEDs and photon detection is also flourishing towards industrialization,demonstrating extensive application prospects.Among the numerous types of perovskite materials,hybrid organic-inorganic halide perovskite materials are one of the most extensively researched and applied types.These materials are assembled from the halides of organic amines and octahedral inorganic metal halides through various intermolecular forces.The structural,conformational,and dimensional differences of organic amine halides introduce rich and adjustable intermolecular interactions,profoundly affecting the diversity of perovskite crystal structures and growth dimensions.This provides perovskite materials with greater flexibility and tunability in structure and performance,laying the groundwork for broad application prospects in optoelectronic devices.By controlling the structure and size of organic amine molecules and introducing functional intermolecular forces,directional regulation of material properties is achieved,providing more candidate materials for addressing existing issues in photon detection,photovoltaic cells,LEDs,and other fields.Perovskite materials exhibit excellent optoelectronic properties such as high charge carrier mobility,long charge carrier diffusion lengths,and high defect tolerance.The diversity and functional designability of perovskite materials and their composites provide broad application prospects for the development of optoelectronic devices.This thesis primarily focuses on addressing the stability issues of perovskite materials and improving their charge collection efficiency in photon detection imaging applications through the targeted design of organic cations in low-dimensional perovskite materials.The impact of the design of organic cations in hybrid organic-inorganic halide perovskite materials on their molecular assembly structure,electronic band structure,optoelectronic performance,and charge collection efficiency in photon detection imaging applications,as well as the minimum detection limit,is discussed.By deeply exploring their performance and potential mechanisms,new ideas and directions are provided for the design and development of perovskite materials with high photoconversion efficiency,high water and thermal stability in the future.The main contents include:1.Electrostatic interaction-coupled perovskite composite materials and their infrared Ⅱ region photon detection imaging application.Addressing the stability issues of three-dimensional perovskite materials and their low utilization of infrared photons above 1000 nm in sunlight,a quasi-twodimensional perovskite-coupled PbS QDs heterojunction composite material bridged by fluorobenzylamine iodide was designed.The perovskite-based composite material simultaneously possesses excellent electrical conductivity of quasi-two-dimensional perovskite materials and high infrared responsivity of PbS QDs.A broad-spectrum photon detector based on this composite material was prepared,and its detection performance for infrared Ⅱ region photons was studied.High-gain response capability(4500%)and fast response speed(60 μs)to 1200 nm infrared light with low light irradiance of 8.8 pW cm-2 were achieved.Imaging of a butterfly wing with 1200 nm infrared light at 31 μW cm-2 was realized,revealing the clear skeletal structure of the butterfly wing that is not visible to the naked eye.The imaging resolution reached 3.9 lp mm-1.2.Cation-π interaction enabled lithographic perovskite materials and their high-performance X-ray detection and imaging application.Cation-π interaction-dominated lithographic perovskite materials and their high-performance X-ray detection and transmission imaging applications.Addressing the stability issues of perovskite materials in water,heat,and electric fields,aromatic amine molecules capable of introducing cation-πhydrophobic interactions were designed.A novel low-dimensional perovskite material rich in cation-π interactions based on aromatic amine iodides was synthesized.By controlling the crystallization dynamics,two-dimensional and onedimensional aromatic amine iodide perovskites were obtained.Reversible dimensional transformation was achieved through water/heat driving,accompanied by the miacrstrain release and defect repair process.The cation-π interactions guided the tight assembly structure of one-dimensional aromatic amine iodide perovskites,realizing a special band structure where the organic part contributes to the valence band and the inorganic part contributes to the conduction band.An Xray photon detector based on this high X-ray attenuation coefficient onedimensional aromatic amine iodide perovskite was prepared.Excellent optoelectronic properties such as high sensitivity(2.5×106μC Gy air-1 cm-2),low minimum detection limit(<5 nGyair s-1),strong water stability(no decomposition after soaking in water for 48 days),high thermal stability(stable operation at 150℃for at least 8 hours),and strong electric field stability(stable operation in an 800 V mm-1 electric field for at least 8 hours)were achieved.For the first time,direct combination with lithography technology successfully prepared large-area microarray X-ray flat panel detectors,and X-ray transmission imaging of teeth was completed in line scan mode.The spatial resolution of single pixel X-ray transmission imaging reached 17.2 lp mm-1,the highest spatial resolution reported for direct X-ray detectors to date.3.Hydrogen bond enabled thermally stable perovskite materials and the impact of their charge transfer behavior on X-ray detection performance.Based on the research results of the second chapter,in order to further obtain high-performance and highly stable X-ray photon detectors,cytosine molecules capable of introducing a large number of hydrogen bonds were designed.A novel one-dimensional perovskite material based on cytosine bromide salt with rich hydrogen bonds and high density(3.51 g cm-3)and high thermal decomposition temperature(285℃)was synthesized.A special band structure where the organic part contributes to the conduction band and the inorganic part contributes to the valence band was achieved.An X-ray photon detector based on this high X-ray attenuation coefficient perovskite material was prepared.High sensitivity(1.2×105μC Gy air-1 cm-2),ultra-low minimum detection limit(<1 nGyair s-1),and low noise equivalent dose(44.6 pGyair),comparable to the state-of-the-art MAPbI3 single crystal X-ray flat panel detector(90 pGyair),were achieved.