Research On Preparation And Application Of Graphene Electrode

Graphene is a two-dimensional crystal composed of sp2-hybridized carbon with honeycomb crystal lattice.Its unique structure and many excellent properties make graphene have broad potential application.In this paper,the properties of graphene prepared by chemical vapor deposition(CVD)are investigated.The optoelectronic devices are fabricated with graphene film.Then the field emission properties of graphene film are studied based on the theory of field emission,and the method of improving field emission properties is proposed.The works can be divided into three parts:Firstly,the graphene film is prepared by CVD.And the graphene film is applied to fabricate optoelectronic devices(Organic light emitting diodes,Organic field effect transistors and Organic photovoltaic).By changing the thickness of the graphene film,the electrical performance of these optoelectronic devices is investigated.The results show that the electrical performance of the optoelectronic devices relies on the film thickness of graphene.This is attributed on the surface resistance and transmittance of the graphene film,which is highly depended on the transfer times while preparing the graphene film.Then,the influence of CVD parameters on the field emission properties of graphene film is studied.It is found that the deposition time has a significant effect on the field emission properties.The graphene film with the deposition time of 5 min exhibits the best field emission properties.The turn-on electrical filed is 9.8 V/?m and electrical threshold field is 13 V/?m.The reason is that the deposition time is too short to grow a continuous graphene film.The 5 min-sample has many "graphene islands",which contain numerous edge field emission regions.The improvement of field emission properties of graphene film is due to the increase of field emission regions.Finally,the method of improving the field emission properties of graphene film is proposed.First,the substrate of the graphene is laser ablated to improve its field emission properties.The surface of the copper foil is laser ablated in a scanning manner,and then graphene film is grown on as-treated copper foil.The field emission properties of as-prepared graphene film are improved.The turn-on electrical field and threshold electrical filed of as-prepared graphene film with the deposition time of 5 min decreases from 9.8 V/?m to 8.8 V/?m and from 13 V/?m to 12.2 V/?m,respectively,and the field enhancement factor increases from 640 to 1757.The second is to change the field emission mode,i.e.,the edge field emission properties of the graphene film are investigated.As the copper foil is flexible,the graphene on copper foil is crimped into a cylindrical shape,and the field emission test is carried out.The results indicate that the field emission properties are improved greatly.The turn-on electrical filed and threshold electrical field are 3.4 V/?m and 5.8 V/?m,respectively,and the field enhancement factor is up to 5068.The field emission current density also increases by an order of magnitude.In summary,this work has made the graphene prepared by the CVD as an electrode,applied to optoelectronic devices and investigated its properties,which laid the foundation for the development of high-performance optoelectronic devices.