Functional Composite System Of Graphene/Organic-Inorganic Perovskite Materials And Its Optoelectronic Properties

Photodetector is a device based on the wave-particle duality,which converts optical signals into electrical signals,and has been widely used in civilian uses,industrial,military,and other fields.According to the principle,there are two types of photodetectors.One is based on the photovoltaic effect.This photodetector mainly works at zero bias or reverse bias,has low dark current and good quantum efficiency,and is used to detect weak light or single photon.The representative products are Hg Cd Te and In Ga As photodetector.The other is based on the photoconductive effect.It must work under a bias voltage.Photogenerated carriers are generated by light to increase the carrier concentration,thereby increasing the conductivity of the material,and reducing the resistance.Therefore,the current can be clearly observed in the circuit.Perovskite materials are one of the most popular research directions in recent years,mainly because of their high broadband absorption,long carrier lifetime,large diffusion length,low non-radiative recombination rate,and up to 10~5 absorption in the ultraviolet to near infrared spectrum.Graphene and its derivatives have high mobility,high light transmittance,adjustable wettability,solution processability and other characteristics,but poor in light absorption.Therefore,combining graphene and perovskite together,graphene as the channel layer and perovskite as the light absorption layer,with the help of reduced graphene oxide,a new photodetector could be fabricated based on the photoconductivity effect.The main contents and results of this paper are as follows:Chemical vapor deposition method was used to grow the single-layer graphene on a copper foil,and then wet method was used to transfer the single-layer graphene onto a silicon wafer.Dimethyl sulfoxide(DMSO)and N,N-dimethylformamide(DMF)were used to dissolve lead iodide(PbI₂)and methylammonium iodide(MAI)to obtain a perovskite precursor solution.At the same time,reduced graphene oxide(Ag-rGO)was added into the perovskite precursor solution,and then the perovskite(CH₃NH₃PbI₃)film was prepared by spin-coating the precursor solution on the single-layer graphene or silicon wafers by one-step method.Finally,chromium gold alloy electrode was grown on the film to fabricate a photodetector.The study has found that the perovskite film prepared on the graphene substrate has a good surface morphology and can improve the crystallinity.According to the theory,the electrons in the graphene will enter the perovskite film to occupy the vacancies in the perovskite and work as a gate.Therefore,the responsivity of the photodetector is higher than that of the pure perovskite photodetector.Finally,although we lost some performance by adding Ag-rGO into the precursor solution,Ag-rGO can passivate the surface of the perovskite to reduce the defects,and play a role as a bridge.The Ag atoms were attached on the surface of the film,as a result absorbance was increased due to the surface plasmon resonance.Carriers were separated more rapidly,so that the responsivity was relatively optimized for about four orders of magnitude.In this paper,by studying the system of graphene/perovskite composite material,a process method for spin-coating perovskite film on graphene has been explored,and the performance of the photodetectors have been analyzed.This work also promotes the development of graphene perovskite photodetectors.