A new method for making transparent electrodes in LCD screens could replace more expensive indium tin oxide ones (ITO).
The silver nanowire electrodes made by researchers at the University of California Los Angeles (UCLA) are flexible and highly conductive, and overcome the limitations associated with ITO.
Besides its high price, ITO has several drawbacks. It’s brittle, making it impractical for use in flexible displays and solar cells, and there is a lack of availability of indium, which is found primarily in Asia. Further, the production of ITO films is relatively inefficient.
For some time, silver nanowire (AgNW) networks have been seen as promising candidates to replace ITO, but complicated treatments have often been required to fuse crossed AgNWs to achieve low resistance and good substrate adhesion.
To address this, the UCLA researchers demonstrated that by fusing AgNWs with metal-oxide nanoparticles and organic polymers, they could efficiently produce highly transparent conductors.
Scientists can easily spray a surface with the nanowires to make a transparent mat, but the challenge is to make the silver nanowires adhere to the surface more securely without the use of extreme temperatures (200°C) or high pressures; steps that make the nanomaterials less compatible with the sensitive organic materials typically used to make flexible electronics.
To meet this challenge, the team developed a low-temperature method to make high-performance transparent electrodes from silver nanowires using spray coating of a unique combination of nanomaterials.
First, researchers sprayed a solution of commercially available silver nanowires onto a surface. They then treated the nanowires with a solution of titanium dioxide nanoparticles to create a hybrid film. As the film dries, capillary forces pull the nanowires together, improving the film’s conductivity. The scientists then coated the film with a layer of conductive polymer to increase the wires’ adhesion to the surface.
’In this work, we demonstrate a simple and effective solution method to achieve highly conductive AgNW composite films with excellent optical transparency and mechanical properties,’ said team leader, Prof Yang Yang of UCLA. ‘This is by far the best solution: a processed, transparent electrode that is compatible with a wide variety of substrate choices.’