The Research Of Organic Electroluminescent Devices Based On Transparent Flexible Electrodes

Organic light-emitting diode(OLED)is playing an increasingly important role in the display field due to its high color gamut,surface luminescence,large viewing angle,good color gamut,low power consumption,cheap price,etc.The anode commonly used in OLED devices is Indium Tin Oxide(ITO).However,ITO is not the best choice for flexible electrodes,because of the poor flexibility of ITO and the lack of metal indium in ITO.Many electrodes are now used as ITO replacement electrodes,such as graphene,carbon nanotubes,metal nanowires,conductive polymers,etc.Because silver nanowires and graphene have excellent bending characteristics,throughput and conductivity,this paper selects silver nanowires and graphene as ITO replacement electrodes for research.In this paper,the research of silver nanowire electrode is mainly focused on reducing the surface roughness of silver nanowire film and reducing the sheet resistance of silver nanowire film.First,a multi-step spin coating method was used to prepare the silver nanowire film,and the optimal spin coating rate was obtained by comparing the different rotation speeds.In order to reduce the surface roughness of the silver nanowire film,we spin-coated polymethyl methacrylate(PMMA)as a flat layer on the surface of the silver nanowire,after applying pressure imprinting,the surface roughness of silver nanowires was reduced from 42.9nm to 4.88 nm,finally,in order to reduce the sheet resistance of the silver nanowire film,we used plasma for treatment.After plasma treatment,the sheet resistance of the silver nanowire electrode was reduced from 50? / sq to 20? / sq.After repeated bending and adhesive tape testing,the resistance of the silver nanowire sheet changed little.The OLED device prepared by untreated silver nanowires as anodes broke down at a lower voltage and the brightness was lower.The OLED device prepared by the treatment process in this paper.The L-V curve and C-V curve of the OLED device are smooth,no breakdown occurs with increasing voltage,and the light emission is excellent.In view of spin coating PMMA imprinting,plasma treatment can improve the performance of silver nanowire electrodes,we believe that this method can be used to improve the performance of silver nanowire electrodes.Graphene has been widely studied as an ITO replacement electrode due to its advantages of high transmittance,good bendability,excellent electrical conductivity,and low price.However,graphene has high sheet resistance,and it is easy to damage graphene during the transfer process,resulting in a high surface roughness of graphene,which is not conducive to the production of OLED devices.In this paper,the research on graphene electrodes is mainly focused on reducing the surface roughness and sheet resistance of graphene films.This article uses Chemical Vapor Deposition(CVD)to prepare graphene.First,polish the graphene-grown copper foil,then spin-coat PMMA,tightly combine graphene and PMMA,then dissolve the copper foil,then transfer the graphene / PMMA to the PET substrate to obtain an electrode with the structure of graphene / PMMA / PET,and finally apply nitric acid to reduce the sheet resistance of the graphene electrode.After the bending test,the graphene electrode did not change much.The graphene / PMMA / PET electrode treated with nitric acid was used as the anode to prepare the OLED device.After testing,the OLED device had good brightness.Experimental results show that the treatment of graphene electrodes in this paper can effectively improve the performance of OLED devices based on graphene electrodes.