Flexible Conductive Electrodes For Energy Devices

At present,indium tin oxide(ITO)as electrodes is often used in commercial world.The intrinsic defects such as high mechanical brittleness,scarcity of indium,exorbitant price of sputtering and incompatible with solution process,which limit its applications in large area flexible devices.Therefore,there is an urgent demand for researching the novel electrodes applying in large area flexible devices with low prices,good mechanical properties and solution processing.The conductive polymer that poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)with high work function,high transmittance and good film-forming,has been commonly used as the transparent electrodes.However,PEDOT:PSS has several disadvantages,including low conductivity,high acidity and hygroscopic properties caused by insulating PSS,which will affect the performances of the devices.Carbon materials including carbon nanotubes and graphene(Gra)with good mechanical property,high mobility and excellent chemical durability have been widely studied.But the biggest problem is the difficult dispersion in most solvents,which limits the application in some degree.Metallic nanowires,another kind of conductive materials,are often used in place of ITO for their high conductivity and transmittance.However,the high roughness and junction resistance limit the further development.First,to solve the problems of low conductivity of PEDOT:PSS and difficulty of dispersing carbon materials,different ?-conjugated sulfonate templates,including dodecylbenzenesulfonate(DBS),2-naphthalenesulfonate(NAS),N,N'-bis(2,6-diisopropylphenyl)-perylenediimide-1,6,7,12-tetraoxyphenylsulfonate(PTS),as well as auxiliary assistance by Gra and multi-walled carbon nanotube(MWCNT),which instead of insulating PSS,have been utilized as single/double template(s)and for in-situ oxidative polymerizing 3,4-ethylenedioxythiophene(EDOT)to the novel nanocomposite electrodes.As a result,the obtained conductive PEDOT:MWCNT:PTS nanocomposite shows continuous interpenetrating network structure with well-dispersed MWCNT and more extended quinoid PEDOT due to in-situ oxidative polymerizing EDOT by double templates of ?-? interacted MWCNT dispersed by electron-deficient conjugated sulfonate which has the biggest conjugate plane.Furthermore,a high specific capacitance of 199 F g-1 at current density of 0.5 A g-1 for PEDOT:MWCNT:PTS electrode has been demonstrated.Next,a novel PEDOT:PSS:S-AgNWs nanocomposite has been further prepared via the in situ oxidative polymerization of EDOT using PSS and 4-mercaptobenzenesulfonic acid-modified silver nanowires(S-AgNWs)double templates,in which there are electrostatic interactions between PEDOT and sulfonic groups from PSS and S-AgNWs.When compared with commercial Clevios PH1000,a more crystalline and conductive PEDOT with quinoid conformation has been developed by partially substituting PSS with the S-AgNWs;this results in the formation of PEDOT:PSS:S-AgNWs showing a lower sheet resistance(64 ? sq-1 at?94.8%transmittance),reduced work function,hygroscopicity,and acidic properties.PEDOT:PSS:S-AgNWs has been used as a transparent electrode for the formation of organic solar cells(OSCs),displaying a power conversion efficiency(PCE)of 10.2%and good storage stability.Moreover,after preparing grids pattern by adopting the ultraviolet nanoimprint lithography technology,the flexible Ag grids-based electrode without contact junctions has been prepared by electrolessly depositing metallic Ag on the exposed polydopamine(PDA)through coordination-bond interactions,which shows better flexibility and interfacial adhesion with comparison to the commercial PET/ITO.The light-emitting diode lamp bulb connected with PET/PDA@Ag grids electrode is still brilliantly lit after 200 continuous bending cycles with radius of 3 mm,suggesting robust mechanical stability.In addition,the PET/PDA@Ag grids-based OSCs yield a PCE of 11.6%.Its PCE is not only comparable to that of conventional ITO electrode,but suitable for different active layer systems.We believe that replacing ITO by the novel commercial transparent electrode,will be realized soon.