Research On Transient Absorption Spectrum And Application Of Optoelectronic Devices Of Several Two-dimensional Materials

In recent years,with the advent of atomic layer thickness of graphene,twodimensional(2D)materials have aroused researchers' great interest.2D materials have excellent characteristics in electronics,optics,thermodynamics,whose physical and chemical properties are quite distinct from bulk materials.However,the current research on 2D materials is still in an early stage;not only are there many new materials in the 2D material family that have not been discovered,but also their properties and the exploration of their application still has a long way to go for the discovered 2D materials.Therefore,it is necessary to do further research and exploration on the preparation,structure properties and applications of these 2D materials.In this paper,liquid-phase exfoliation,probe ultrasound and liquid/liquid interface synthesis were used to prepare several popular 2D materials.Through a series of characterization and detection methods,the morphological structure and steady-state optical properties of these materials were measured.Based on the principle of pumpprobe,a femtosecond transient absorption spectrometer was used to study the carrier dynamics of materials.Finally,combined with some of the superior properties of the materials,the application of optoelectronic devices based on 2D materials such as photodetector,fiber sensor and fiber laser were proposed and demonstrated.The main content and research results are as follows:(1)Indium selenide(InSe)with different sizes(from bulk to quantum dots)were prepared based on the liquid-phase exfoliation method.We systematically studied the carrier dynamics characteristics of InSe by femtosecond transient absorption spectrometer.Through fitting dynamic curves of different sizes of InSe by double exponential function and TD-DFT calculations,we found that the normal carrier dynamics at 700 nm is due to in-plane excitons and the abnormal non-size-dependent dynamic decay at 500 nm are attributed to stable surface-bound excitons.(2)Through a typical liquid/liquid interface synthesis method,we prepared 2D graphyne materials.The time-resolved transient absorption spectrum of graphyne was studied for the first time.The measurement results show that the transient absorption spectrum has two excited state absorption peaks near 640 nm and 880 nm,indicating that graphyne has rich excited state energy levels.By fitting the lifetimes of different wavelengths,we found that there are obvious short lifetimes(?2 ps)and long lifetimes(?24 ps);which can be attributed to the intraband cooling of the thermal excitons and the recombination process of the excitons,respectively.(3)We constructed a photoelectrochemical detector based on InSe.The measurement results show that the photoelectrochemical detector has excellent on/off photo-response,high responsivity and stability,and can be self-starting without an external power.In addition,for the first time,we have also constructed an all-fiber photothermal fiber sensor with enhanced sensitivity based on InSe nanosheets.And achieved 26.8 times magnification of sensitivity.Finally,the saturable absorption(SA)characteristics of graphyne at different wavelengths were measured by Z-scan technique.For the first time,the graphyne-PVP film was used as the SA of the ultrashort pulse laser,which was embedded in the constructed ring fiber resonator to achieve the pulse output of 1 ?m and 1.5 ?m in fiber mode-locked lasers,respectively.