Research On Flexible Organic Light-emitting Devices Based On Silver Nanowire Composite Anode

With the further study of organic conductive materials,many organic materials with excellent optical and electrical properties have been developed.The continuous development of organic materials has made the organic light emitting device(OLED)developed rapidly.At present,the OLED industry has begun to take shape,mainly using ITO as the anode,organic materials as the middle layer,metal as the cathode of the thin film light emitting devices.In the future,OLED will further integrate into the life of people as lighting and display technology.But with the improvement of product requirements,OLED is developing towards flexibility.However,the fragility and poor mechanical properties of ITO electrodes restrict the development of flexible OLED.So people are looking for other materials as alternatives to ITO in order to realize the industrialization of flexible OLED.The hot materials known at present are metal nanowires,graphene,carbon nanotubes,and conductive polymers.Silver nanowires(AgNWs)are most common in metal nanowires.Due to the flexibility of the silver material itself,nanowires with nano size and retained metal conductivity can be prepared.AgNWs is a very good flexible electrode material,and the film has high transmittance and excellent mechanical properties.Graphene has also been one of the most concerned materials in recent years.Due to its excellent mechanical properties,stability,thermal conductivity and light transmittance,it has been used in many fields.There are many reports about the application of graphene as transparent electrode because the transmittance of single graphene is as high as 97%and its internal electronic transmission ability is very strong.However,these two materials have some shortcomings and shortcomings.For example,the structure of the silver nanowires is rough,the lap joint is loose,and the conductive gap is large;the conductivity of the graphene is poor and the function function is low.When the OLED is prepared,the hole injection ability is insufficient,which has become an impediment to the development of graphene in OLED electrodes.In this work,silver nanowires and graphene are modified.In order to prepare flexible electrodes with high conductivity,high transmittance and high flexibility,we have mainly carried out the following two groups of work:(1)The preparation of AgNWs/graphene composite conductive electrode.An AgNWs thin film is prepared on graphene using low concentration AgNWs by spin coating.AgNWs provide good conductive paths between graphene sheets,play a role in bridge,and improve the conductivity of graphene films.Then,through the substrate transfer method,the composite electrode is transferred to form flexible electrode by using the light curing adhesive NOA63.The roughness of the composite electrode is greatly reduced due to the burying effect of NOA63,which solves the drawback of loosening the AgNWs.By using this method,the square resistance of the composite electrode is greatly reduced and the transparent conductive electrodes of composite electrodes are maintained over 75%in the visible wavelength range by optimizing the concentration of silver nanowires.(2)The preparation of silver/graphene composite conductive electrode.We have tried to grow a thin layer of ultra-thin silver film directly on the graphene film.We use the transfer method and graphene will sink to the NOA63.After,used the vacuum evaporation method to grow thin silver layer on the surface of graphene.The silver island growth,so in the case of thin silver is not forming a conductive film well.However relies on the role of graphene,the silver with thickness of 4nm,the sheet resistance of composite electrode was significantly reduced.When in 8nm,composite electrode block resistance can be reduced to 10?/sq.Finally,we used graphene/Ag(4nm)and graphene/Ag(8nm)electrode was prepared by organic electroluminescent devices,and compared with the graphene electrode device and ITO electrode devices.It is found that the luminescent properties of graphene/silver electrode devices are much better than those of single graphene electrode devices.The turn-on voltage of composite electrode devices are about 2.4V,the luminescence intensity can reach 1300cd/m~2 in 5V,in 9V can reach 40000cd/m~2.