Preparation Of High-performance Silver Nanowire Electrodes And Their Application In Flexible Organic Solar Cells Research

The solar cell is an effective electronic device that can convert solar energy into electrical energy.Compared to other inorganic photovoltaic technologies,organic solar cells（OSCs）have advantages such as lightweight,flexibility,low cost,and large-scale preparation by printing.Flexible organic solar cells（FOSCs）in OSCs have significant flexibility and can be widely used in wearable devices,various portable electronics and communication devices,and transportation,making them an important research direction in the field of organic photovoltaics.High-performance transparent electrodes are an important part of preparing efficient FOSCs.Although indium tin oxide（ITO）films are widely used in the processing of transparent electrodes,they are not suitable for processing flexible transparent electrodes due to their high brittleness and easy breakage.Silver nanowires（AgNWs）have many advantages such as high conductivity,low resistance,high transmittance,and solution processability.They also have excellent flexibility and can be widely used in flexible optoelectronics by dispersing in water or alcohol solutions as transparent electrodes.However,AgNWs also have many disadvantages,such as high roughness,poor interface adhesion,and poor storage stability.In addition,because AgNWs have a high aspect ratio（length of 5-100μm and diameter of 10-200 nm）,they are prone to aggregation in suspension and thin film electrodes,which reduces their overall optoelectronic performance and hinders their application in flexible optoelectronic devices.To solve these problems,this study used modified and improved AgNWs to prepare a high-performance silver nanowire transparent composite electrode with low surface roughness,high transmittance,high interface adhesion,and stability,and constructed a flexible organic solar cell.The main results of this study include:（1）Introducing the zwitterionic molecule 3-sulfopropyl tetradecyl dimethyl ammonium bromide（SB3-14）into the AgNWs suspension to obtain stable and uniformly dispersed SB3-14@AgNWs suspension,and spin-coating to obtain a transparent conductive film with excellent optoelectronic performance.It is then semi-embedded in polyimide substrate to obtain AgNWs composite electrode（SB3-14@AgNWs@PI）with excellent performance.Based on SB3-14@AgNWs@PI composite electrode,high-efficiency FOSCs were prepared.The SB3-14 molecule consists of cationic and anionic groups with opposite charges in equal amounts,separated by a short molecular chain.SB3-14 molecules can be adsorbed on the surface of AgNWs through the electrostatic interaction between-SO₃^-and Ag⁺.Due to the strong hydration effect of zwitterionic molecules and the electrostatic repulsion of cations,stable and uniformly dispersed AgNWs suspension can be obtained,and an orthogonal AgNWs grid with an angle close to 90o can be formed during film formation.The AgNWs electrode prepared by it has good optoelectronic performance(sheet resistance R_sh is about 11.8?cm^-2,transmittance of 550 nm(T₅₅₀)is about 94.4%)and good storage stability.By the method of semienbedding AgNWs into polyimide（PI）substrate,a transparent conductive electrode with excellent optoelectronic performance,low surface roughness（RMS is about0.56 nm）,and high mechanical stability（after 30,000 cycles of bending at a small bending radius of 1 mm,the initial efficiency can still be maintained at92%）was prepared.The photovoltaic conversion efficiency of FOSCs prepared with it reached 15.41%.（2）By introducing sodium alginate（SA）into the AgNWs suspension,a transparent conductive film with excellent optoelectronic performance and interface adhesion was obtained after spin-coating modified AgNWs.SA is a material containing abundant carboxyl and hydroxyl groups,which can form hydrogen bonds with the PVP molecules remaining on the surface of AgNWs or directly form ionic bonds with Ag⁺.Therefore,SA can be combined with the surface of AgNWs to improve the dispersion and suspension stability of silver nanowires.It can also form hydrogen bonds between SA and PET to significantly improve the adhesion between AgNWs and PET substrate.SA can also fill the blank spaces in the AgNWs network,reducing the electrode roughness.After treatment with Ca Cl₂ solution,Na⁺in SA can undergo ion exchange reaction with Ca²⁺to crosslink SA,thereby improving the solvent resistance of AgNWs electrode.At the same time,Cl^–can promote the welding at the junctions of AgNWs,thereby reducing the junction resistance and increasing the electrode conductivity.A highly dispersed and stable AgNWs suspension was prepared,and an AgNWs@PET flexible transparent composite electrode with high conductivity,high transmittance,strong interface adhesion,low surface roughness,and excellent solvent resistance was obtained.