Study On Preparation And Optoelectronic Characteristics Of GO(rGO)/Si Heterojunction

Light is one of the most efficient carrier of information.Photodetectors can convert optical signals into electrical signals by the photoelectric effect,are commonly used in electrical devices for light detecting.However,as the size of miniature optoelectronic devices continues to shrink and develop towards the nanometer level,photodetectors based on traditional semiconductor materials have encountered an insurmountable bottleneck and cannot meet the current demand for device miniaturization and intelligence.Two-dimensional semiconductor materials represented by graphene,transition metal sulfides and black phosphorus are widely used in the field of integrated optoelectronic devices due to their unique optoelectronic properties.With the advantages of ultra-high carrier mobility,high light transmittance,and wide absorption spectrum,graphene has important research value and application prospects in photodetectors.But the low absorption rate and high dark current brought by the zero band gap structure of graphene severely limit the performance of graphene-based photodetectors.A common means is to prepare graphene oxide as a substitute for graphene.Graphene oxide opens up the zero band gap of graphene,giving it tunable band gap and hydrophilicity,which can not only improve the drawbacks of graphene-based photodetectors,but also make it easier to use cost-effective methods for production.In this work,the graphene oxide/n-type silicon heterojunction was prepared via dip-coating method.The graphene oxide aqueous solution used has a concentration of 12 mg/ml.The immersion time is 120 s to ensure that the substrate is completely wet.A uniform and rich-wrinkled graphene oxide thin film was prepared at a pulling speed of 500μm/s.The surface morphology and structural defects of the films were observed by SEM and Raman spectroscopy,and the main defects are sp³ hybridized carbon atoms.The prepared graphene oxide/p-type silicon heterojunction shows obvious rectification characteristics,and the rectifying ratio measured at±1V is about 68.3.At-2 V bias voltage,the heterojunction shows a good photoconductivity effect.The photoresponse current reaches 176.9μA,the photo-to-dark current ratio is 8.3,and the normalized detection rate up to 2.02×10¹² Jones.Then,the graphene oxide film prepared via dip-coating was reduced by a 30%HI solution prepared with ethanol as a solvent.The oxygen content of the reduced graphene oxide,which affected by the reduction time,can control the band gap of the prepared material.At±1 V bias voltage,the rectifying ratio of the reduced graphene oxide is 93.Compared with graphene oxide,the photovoltaic effect of reduced graphene oxide at zero bias is significantly improved.Under the light illumination of 4 m W/cm²,the device shows self-powered property,the photo-to-dark current ratio is 1485,and the normalized detection rate up to 2.94×10¹¹ Jones.The effects of oxidation degree on heterojunctions were compared.The higher the degree of oxidation of reduced graphene oxide,the larger the band gap,which corresponds to a larger work function.For reduced graphene oxide/n-type silicon heterojunction,higher oxygen content has a stronger light response.