The Study On The Interlayer Coupling And Optical Properties Of Two-Dimensional Layered Materials And Heterostructure

The two-dimensional layered materials represented by graphene,molybdenum disulfide,and tungsten disulfide have attracted extensive attention from scientific research and industry due to their excellent performance and huge application prospects.The bandgap of two-dimensional transition metal chalcogenide can be controlled by chemical or physical methods.When the thickness decreases to single layer,the indirect band gap becomes a direct band gap,and the luminous efficiency is also improved,and thus it has great application prospects in the field of photoelectric materials.In addition to two-dimensional materials,trihalide perovskite has also become a research hotspot in the field of photoelectric materials in recent years.The all-inorganic cesium lead halides perovskite?CsPbX₃?has a large absorption coefficient,long carrier diffusion length and long life,a narrow photoluminescence line width,and a fluorescence quantum efficiency of more than 90%.At the same time,the band gap adjustment can be achieved by adjusting the halogen element ratio.Compared to hybrid organic-inorganic perovskites,its stability is higher and it is a very promising optoelectronic material.Heterostructures prepared by stacking two-dimensional layered materials on each other further enriches the types of two-dimensional layered materials,and also because heterostructures combine the excellent properties of different constituent materials,it provides a platform for studying the interaction between materials and the energy or charge transfer mechanism.Heterostructure devices based on two-dimensional layered materials and perovskites have excellent performance such as high response speed and wide response wavelength range.Therefore,in order to further study the interlayer interaction based on layers two-dimensional transition metal chalcogenides and CsPbX₃ heterostructures,and study the dynamics of the carriers at the interface and the photoelectric properties of the device,we did the following works:1.Designed and built a system that integrates three functions of Raman,fluorescence,and photocurrent mapping.After system optimized,the signal collection capability of the system is greatly improved.Based on the optical path,through the preparation of the LabVIEW program,the stepper motor and the Keithley 2612B source table are linked to realize the photocurrent mapping function.Applying this system to material characterization and position sensitive detectors?PSDs?shows that the system meets the original design goals well and enriches the methods for material optical characterization and photodetection in the laboratory.2.The transfer process of carriers at the interface between the two materials was studied after monolayer WS₂ and CsPbBr₃ formed a heterostructure.After stacking mechanically exfoliated single-layer WS₂ and CsPbBr₃ prepared by chemical vapor deposition method into heterostructures,WS₂,CsPbBr₃ and their heterostructures were excited by lasers with different wavelengths.It is found that fluorescence quenching occurred after the formation of heterostructures between the two materials.Heterostructure device was fabricated as single-layer WS₂ and CsPbBr₃,and their photoelectric detection performance was improved,indicating that after the formation of heterostructures in the two materials,photo-generated electrons were transferred to WS₂,and vacancies remained in CsPbBr₃.At the interface,the separation of electron-hole pairs occurs at the interface.The effective separation of photogenerated electron-hole pairs improves the device performance.3.The changes of fluorescence of WS₂,CsPbBr₃ and their heterostructure with power and temperature were studied.In WS₂,we observed obvious xcitons,trions,and biexcitons luminescence,and the superlinear relationship of biexcitons change with power.In CsPbBr₃,with the increase of temperature,the fluorescence of CsPbBr₃shows an abnormal blue shift.This is due to the fact that thermal expansion plays a dominant role in this process,and it is found through the change of temperature that the luminescence at room temperature is the E peak,and the abnormal change of the E-peak with temperature may be due to the phase change.After the formation of heterostructure,both materials exhibit fluorescence quenching at low temperatures due to charge transfer.