Research On Flexible Light Emitting Device Based On ZnO Nanowire/CsPbX₃ Quantum Dots Composite System

As a third-generation semiconductor material,ZnO is favored by researchers for its high bason-binding energy（60me V）,low growth temperature and low cost,and is an ideal UV optoelectronic material,especially for deep-UV luminescence and laser diodes with broad development potential in photochemistry and defense and military fields.Using the energy band engineering theory,ZnO systems obtained by doping with other ions（Al,Mg,Cd,Ga,etc.）can make ZnO more widely used in applications such as UV detectors,light emitting devices,solar cells,etc.The preparation of Mg ZnO alloy materials and light-emitting devices can achieve continuously tunable deep-UV emission at wavelengths.However,stable and reproducible p-type ZnO is still difficult to achieve and is the main bottleneck limiting the development of ZnO-based homojunction devices.Therefore,the development of heterojunction devices has become the main choice for current ZnO light-emitting device research.In this thesis,we have carried out a research work for the flexible white light prototype devices of the composite system based on ZnO/MgO core-shell layer nanowire arrays with MIS junction as the short-wavelength excitation source CsPbBr₃&CsPbI₃quantum dots as the fluorescence layer,and conducted an in-depth study on its electroluminescence as well as physical mechanism.The main contents are as follows.In this paper,ZnO nanowire arrays were prepared by hydrothermal synthesis,and the effects of acid-base ratio at different precursor solution concentrations on the morphology of ZnO nanowire arrays in terms of diameter,aspect ratio and surface density were investigated;magnetron sputtering technology was used to achieve co-axial growth coating of MgO shell layer on ZnO nanowire arrays by using reduced deposition rate,substrate rotation and tilt sputtering,and to study the effect of surface MgO layer The effect of MgO passivation on the optical properties of the nanowires was investigated;a translucent Au film was vaporized on the surface of the thin MgO layer at the top of the nanowire array as the top electrode of the device,and the effect of the MgO passivation layer on the electrical properties,carrier transport and composite process of the device was investigated to optimize the structure of the heterojunction device and realize the UV electroluminescence from ZnO nanowires;the"thermal injection method We have also used the"thermal injection method"to prepare chalcogenide quantum dots CsPbBr₃&CsPbI₃,and the composite system of ZnO nanowires/CsPbX₃quantum dots for the study of white light prototype devices on flexible substrates.In the experiments,the surface microstructures of nanowire arrays and core-shell layer structures were characterized by SEM;the crystalline properties of crystalline seed layers,nanowire arrays,and core-shell layer structures were characterized by X-ray diffraction;the surface hydrophile properties of one-dimensional nanostructured structures were characterized by contact angle;the electrical properties of core-shell layer structure MIS junction devices were characterized by EL;the optical properties of nanowire arrays,core-shell layer structures,and chalcogenide quantum dots were characterized by PL The optical properties of nanowire arrays,core-shell layer structures,and chalcogenide quantum dots were characterized using PL;the microscopic morphology of chalcogenide quantum dots was characterized using TEM.Finally,the optimal conditions were explored to realize the white light prototype device.It was found experimentally that the synthesized ZnO nanowire arrays had a cylindrical structure and were more dense when the solution concentration of the precursor was 20 mmol/L and 20 mmol/L.A co-axially encapsulated MgO passivation layer was grown on the ZnO nanowire arrays by substrate rotation and tilt sputtering to achieve the growth of a ZnO/MgO core-shell layer on a flexible ZnO foil substrate nanowire arrays on a flexible zinc foil substrate.Based on the above study,the all-inorganic CsPbBr₃&CsPbI₃chalcogenide quantum dots were prepared by the"thermal injection method",and the fluorescence center wavelengths of the produced dots were 531.4 nm and 619 nm.The ZnO nanowire/CsPbX₃quantum dot composite devices were prepared by homogenization method.The prototype white light device was realized by using MIS heterojunction as the short-wavelength excitation source and chalcogenide quantum dots as the fluorescence layer.The EL spectrum of the white light prototype device has two emission peaks in the UV and visible bands and the color coordinates are（0.3498,0.4245）with a color temperature of 5060 K.