silver nanowire network
LOS ANGELES, UNITED STATES: The indium tin oxide (ITO) transparent electrodes used in many electronic devices have huge demand in the market with increasing price. Scientists have been searching for a less costly and more dynamic alternative, particularly for use in future flexible electronics. Besides 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.
Now, researchers at UCLA reported in the journal ACS Nano that they have developed silver nanowires in combination with other nanomaterials which are flexible and highly conductive and overcome the limitations associated with ITO.The complications with silver nanowires are to fuse crossed AgNWs to achieve low resistance and good substrate adhesion.
The team of researchers represents a collaboration between the department of materials science and engineering at the UCLA Henry Samueli School of Engineering and Applied Science; the department of chemistry and biochemistry in the UCLA College of Letters and Science; and the California NanoSystems Institute (CNSI) at UCLA.The team is led by Yang Yang, a professor of materials science and engineering, UCLA and Paul Weiss, director of the CNSI and a professor of materials science and engineering and of chemistry and biochemistry.
"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 Yang. 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, Rui Zhu, the paper's first author, 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.
The AgNW composite meshes are highly conductive, with excellent optical transparency and mechanical properties. The research team also built solar cells using the new electrodes and found that their performance was comparable to that of solar cells made with indium tin oxide.
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