Silver nanowire network. Clear conductor: This scanning-electron micrograph shows a transparent conducting film made up of silver nanowires (apparent as lines), titanium nanoparticles, and a conductive polymer. Image: UCLA
As the market for liquid crystal displays and other
electronics continues to drive up the price of indium—the material used to make
the indium tin oxide (ITO) transparent electrodes in these devices—scientists
have been searching for a less costly and more dynamic alternative,
particularly for use in future flexible electronics.
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
Now, researchers at the University
of California, Los Angeles (UCLA) report in ACS Nano that they have developed a
unique method for producing transparent electrodes that uses silver nanowires
in combination with other nanomaterials. The new electrodes are flexible and
highly conductive and overcome the limitations associated with ITO.
For some time, silver nanowire (AgNW) networks have been
seen as promising candidates to replace ITO because they are flexible and each
wire is highly conductive. 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.
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 was led by Yang Yang, a professor of materials
science and engineering, 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,” says Yang who
also directs the Nano
Center at the CNSI.
“This is by far the best solution: a processed, transparent electrode that
is compatible with a wide variety of substrate choices.”
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
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
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.