December 15, 2015

Transparent metal films for smart phone, tablet and TV displays

Samples of the correlated metals strontium vanadate (two squares on left) and calcium vanadate
(two squares on right) with two uncoated squares in center. Image: Lei Zhang / Penn State

(December 15, 2015)  A new material that is both highly transparent and electrically conductive could make large screen displays, smart windows and even touch screens and solar cells more affordable and efficient, according to the Penn State materials scientists and engineers who discovered it.

Indium tin oxide, the transparent conductor that is currently used for more than 90 percent of the display market, has been the dominant material for the past 60 years. However, in the last decade, the price of indium has increased dramatically. Displays and touchscreen modules have become a main cost driver in smartphones and tablets, making up close to 40 percent of the cost. While memory chips and processors get cheaper, displays get more expensive from generation to generation. Manufacturers have searched for a possible ITO replacement, but until now, nothing has matched ITO's combination of optical transparency, electrical conductivity and ease of fabrication.

A team led by Roman Engel-Herbert, assistant professor of materials science and engineering, reports today (Dec 15) online in Nature Materials a new design strategy that approaches the problem from a different angle. The researchers use thin -- 10 nanometer -- films of an unusual class of materials called correlated metals in which the electrons flow like a liquid. While in most conventional metals, such as copper, gold, aluminum or silver, electrons flow like a gas, in correlated metals, such as strontium vanadate and calcium vanadate, they move like a liquid. According to the researchers, this electron flow produces high optical transparency along with high metal-like conductivity.

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