[Image above] A team of researchers, led by the University of Minnesota, has discovered a new nanoscale thin film material with the highest-ever conductivity in its class. Credit: University of Minnesota
How much of your day is spent staring at display screens?
If you consider the chunk of time you spend in front of the computer (whether being productive or being distracted), looking at your phone, or watching television, screen time might eat up a rather hefty slice of the daily pie chart of your time. I know mine does.
Once you consider all that time your eyeballs are fixated on screens, it starts to make you think about the incredible technology that makes those crisp, clear, high-definition displays possible.
One of the main technologies in display screens is transparent conductor materials—integral materials in LCD displays, OLEDs, touchscreens, photovoltaics, and other technologies.
A ceramic material called indium tin oxide is the go-to transparent conductor material, controlling over 90% of the market share. But it’s not perfect—cost, performance, supply, and the material’s limited flexibility are all concerns with indium tin oxide—so scientists have long been searching for a replacement material.
Researchers from the University of Minnesota (Minneapolis, Minn.), Washington University (St. Louis, Mo.), Lawrence Berkeley National Lab (Berkeley, Calif.), and Nanyang Technological University (Singapore) now think they may have found the ideal replacement in a transparent perovskite oxide material that displays record high conductivity despite having a wide bandgap.
As I have explained in a past story here on Ceramic Tech Today, a bandgap is kind of like a no-fly zone for electrons. It’s the amount of energy needed for an electron in a semiconductor to move from a bound state to a free state—from a valence band to a conduction band, where electrons can conduct energy.
Wide bandgap semiconductors are essential in high-tech applications that reduce energy usage, but the materials usually have low conductivity or poor transparency.
But the new wide bandgap material, a thin film of barium stannate (BaSnO3), has neither—despite being optically transparent, it also displays record high conductivity.
“The high conductivity and wide bandgap make this an ideal material for making optically transparent conducting films, which could be used in a wide variety of electronic devices, including high-power electronics, electronic displays, touch screens, and even solar cells in which light needs to pass through the device,” Bharat Jalan, lead researcher of the study and a University of Minnesota chemical engineering and materials science professor, says in a University of Minnesota press release.
That’s partially because the scientists used molecular beam epitaxy to grow thin films of barium stannate using a chemical precursor of tin, rather than elemental tin. “The chemical precursor of tin has unique, radical properties that enhanced the chemical reactivity and greatly improved the metal oxide formation process,” according to the release.
The process allowed them to precisely control the film’s thickness, chemical composition, and the amount of defects, which was a critical component of improving the thin film’s conductivity.
Importantly, the scientists say that they can reproducibly manufacture barium stannate thin films at scale using their new technique. And because the precursor materials are less expensive than indium, it could mean that manufacturing better display screens and other technologies becomes cheaper at the same time.
“Even though this material has the highest conductivity within the same materials class, there is much room for improvement in addition to the outstanding potential for discovering new physics if we decrease the defects,” Jalan says in the release. “That’s our next goal.”
The open-access paper, published in Nature Communications, is “Wide bandgap BaSnO3 films with room temperature conductivity exceeding 104 Scm-1” (DOI: 10.1038/ncomms15167).