| Due to its unique electronic structure,graphene had become a research focus of infrared detection in recent years.Graphene films and its devices were prepared by reduction oxidation method.The optical absorption characteristics,energy band structure evolution and photoelectric response characteristics of reduced graphene oxide(RGO)films were all studied.Then,the complex sensitive material of PbS quantum dot and graphene were synthesized,and its photoelectric response characteristics and mechanism were also carried out.The main research results are as follows:(1)structure and energy band evolution of RGO: graphene oxide(GO)was prepared by Hummers method,and a stable GO dispersion aqueous solution was prepared by ultrasonic stripping and centrifugal separation.After high temperature annealing and reduction,GO at different temperatures was obtained.Its structure was characterized by XRD,FTIR,Raman and other test methods,and the optical band gap was obtained by fitting the TAUC plot.The results show that :(1)with the increase of temperature,the shedding sequence of oxygen functions is related to temperature,in which hydroxyl(O-H)in water is lost before 150?,carboxyl(COOH)and carbon and oxygen double bond(C=O)are lost between 150? and 230?,and epoxy(C-OH)is mainly lost between 150? and 230? and 230? and 400?.(2)the TAUC method was used to calculate the optical band gap of RGO at different reduction temperatures,and it was found that the optical band gap gradually decreased with the increase of temperature,and the changing tendency of the band gap was in a ladder shape.The experiment confirmed the loss of specific oxygen functional groups was at the four temperature stages same to that of corresponding band gap.(2)the photoelectric device characteristics and its response mechanism: The influence of electrode material on the photoelectric characteristics was carried out based on devices with symmetrical electrode of Pt-RGO-Pt,and asymmetric of Ag-RGO-Pt,respectively.The response of the asymmetric struture was superior to that of the symmetrical structure in that potential barrier formed between Ag and RGO due to matching of their working function which made electron hole pairs separate more easily.In addition,for symmetrical devices with annealing temperature up to 800?,its response time decreased from seconds to milliseconds,and the corresponding response mechanism varied from single photothermal effect to a composite effect of photovoltaic and photothermal,which was corresponding to the evolution of its bandgap.(3)composite sensitive material devices of PbS quantum dots and their response characteristics: PbS quantum dots were drop casted onto the graphene surface,which greatly improved the absorption capacity of the sensitive layer due to the size effect of nanomaterials.At the same time,due to the different work functions of PbS and graphene,the internal electric field was formed at the interface to promote the separation of carriers.Under the irradiation of980 nm laser light source,the rising time of the device reached 0.3s,the responsiveness was7 mA/W.Also,the size effect led to the formation of excitons in PbS quantum dots,and the internal electric field separated of these electron-hole and then fored photocurrent.In this paper,the physical causes of the step-like changes in the optical band gap during the reduction of GO and the direct relationship between the band gap and the structure have been confirmed.An asymmetric photoelectric device was constructed,the influence law of optical band gap and photoelectric response characteristics were studied,and the photoelectric response mechanism was defined,which laid a foundation for the application of graphene in the field of infrared photoelectric detection. |
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