What do touchscreen, LED lighting, and solar cells have in common? A rare metal called indium, which is a key ingredient in their manufacturing process. Indium is regarded as a technology critical element and is used in the production of thin films of indium tin oxide (ITO). Because of their high electrical conductivity and optical transparency, ITOs are perfect for a wide array of display technologies such as touchscreens.
Critical raw material
The problem, however, is that indium is relatively rare, scarcely occurring in elemental form in the Earth’s crust. This means that it is usually extracted in combination with other metals, such as zinc and lead. As a result, indium is listed as a critical raw material in Europe.
Because of its rarity, scientists are continuously looking for more common alternatives. With that goal in mind, researchers at Paragraf and the Queen Mary University of London have recently stumbled upon a very promising candidate — graphene.
What is graphene?
Graphene is a one-atom-thick sheet of carbon arranged in a hexagonal lattice, and is often touted as a wonder material because of its many amazing properties, especially in the realm of electronics and optics.
Swapping indium for graphene
As part of the new study, the team first deposited a layer of graphene onto a transparent substrate, using a method called metal-organic chemical vapor deposition. They then improved its conductivity by lacing it with nitric acid, and carved it with lasers into a special pattern to make an anode out of it. The end product was a graphene-based OLED device that performed just as well as those made with indium tin oxide.
“Because of its importance and scarcity there have been many attempts to replace ITO, but no material has been found to have a comparable performance in an electronic or optical device until now,” says Professor Colin Humphreys, author of the study. “Our paper is the first paper in the world to demonstrate that graphene can replace ITO in an electronic/optical device. We have shown that a graphene-OLED has identical performance to an ITO-OLED.”
While the study is an important breakthrough in our efforts to wean away from the use of rare metals in our day-to-day electronics, there are still a few more steps to go until we reach that point. While it’s rare, indium still remains relatively cheap compared to graphene, which is currently costly to make in bulk. That may soon change, however, as companies like Paragraf are working on cost-effective ways to produce graphene on larger scales.
Image source: Advanced Optical Materials – Wafer-Scale Graphene Anodes Replace Indium Tin Oxide in Organic Light-Emitting Diodes