Preparation Of Flexible Transparent Conductive Layer Based On Silver Nanowires And The Study Of Its Application In Polymer Solar Cells

As people's demands for electronic products are getting higher and higher,much thinner or wearable flexible electronic devices are emerging in multitude in our daily life.However,traditional transparent conductive material indium tin oxide ITO cannot satisfy this demand due to their fragile characteristics.Silver nanowire(AgNW)is the most promising alternative to ITO as the next generation transparent conductive materials due to its excellent electrical conductivity and ductility.Since the adhesion between silver nanowires and surface of the substrates is weak and the high surface roughness of AgNW films,the conventional method for reinforcing the adhesion between the silver nanowires and the substrate cannot be used on a large scale,and it is necessary to find a method to solve the problem of weak adhesion and high surface roughness at the same time.Ordered arrangement of silver nanowires can be used to achieve optical anisotropy.Ordered nano-film materials with optical anisotropy property have many potential applications in flexible electronics,photovoltaics,polarized optics,sensing,and metamaterials.However,the existing methods of orderly silver nanowires depositing are complicated to operate and cannot be applied on a large scale.It is essential to solve the problem of large-scale coating and ordered deposition of silver nanowires at the same time,and promote the application of silver nanowires in production and life.It was found that the square applicator can obtain the orderly arrangement of silver nanowires in part.In this paper,a kind of coating device is designed to realize ordered deposition of nanowires according to the method of square coating apparatus and the characteristics of silver nanowire ink.Silver nanowires are subjected to the tension of the substrate and the coating device during the coating process so that they can be arranged in the order of the coating direction.This method can obtain a large area of silver nanowire array quickly and save the conductive ink.Cross-scratch coating can obtain conductive silver nanowire film that has better light transmittance than silver nanowire film obtained by conventional spin coating method under the same square resistance.A transparent conductive electrode was obtained by depositing silver nanowire AgNWs on a smooth glass substrate,and a layer of polyvinyl alcohol(PVA)aqueoussolution was spin-coated on AgNWs,dried and then peeled it off from the glass substrate to obtain a PVA: AgNWs electrode with smooth surface.Surface roughness can reach 3.68 nm and it is close to that of PET/ITO.The composite electrode is bonded to the plastic substrate ethylene phthalate(PET)by UV glue to obtain an Incurved bendable flexible transparent electrode PET/flip-AgNWs.A flexible transparent electrode with better light transmission performance could obtained through depositing silver nanowires by cross-scraping.In special,electrodes based on AgNWs behave higher light transmission in the UV and IR bands than PET/ITO.The square resistance of PET/flip-AgNWs was kept unchanged after it has been Incurved bended 1200 times with bending radius and angle are 5 mm and 180°respectively.PET/ITO losing its conductivity after several times bending tests.Based on PET/flip-AgNWs electrodes,flexible polymer solar cells with incurved bending resistance are obtained.The surface plasma scattering effect of silver nanowires improved the haze of the transparent conductive film,extended the propagation path of light in the active layer and promotes the absorption of light by the active layer material.The more light energy absorbed,the more photogenerated carriers can be generated,which improves the short-circuit current of the solar cell and improves the performance of the device.Compared to conventional PET/ITO,the device performance is improved from 4.2% to 4.7%,and the device remains at 75% of the initial efficiency value after 1050 Incurved bending tests.Through the experimental analysis,the reason of cells based on PET/flip-AgNWs electrode lose efficiency after the excessive bending test has been implemented is obtained.Since the silver nanowires will form protrusions on the surface of the electrode during the Incurved bending tests,which contact with the active layer causes short circuit of the device.This provides a new idea for further research on the incurved or Out-curved bending-resistant flexible thin film device.It needs to reduce the thickness of overall device and the extrusion or mutual stretching force exerted on silver nanowire network during the bending processes,and a flexible film device with much better bending resistant property could be otained.