Researchers from Paragraf and the Queen Mary University of London demonstrated the successful fabrication of an Organic Light-Emitting Diode (DLED) with a monolayer graphene anode, replacing ITO in organic light-emitting diodes.
Indium is one of the nine rarest elements in the Earth’s crust, with the limited elemental abundance in the Earth’s crust. Nonetheless, due to the lack of a viable replacement, indium tin oxide (ITO) is a key part of the touch screens on our mobile phones and computers. Most homes will have many items containing indium; it’s used in flatscreen TVs, solar panels, as well as LED lights in our homes.
The new research opens the door to a radical change in the potential of high-tech devices of the future by removing a limiting ingredient, indium. Graphene is considered a promising material for replacing ITO in an electronic/optical device. But for this to become possible, a low-cost and scalable fabrication method that produces graphene with comparable performance to ITO is required.
Graphene is a single layer of carbon atoms and exhibits a variety of fascinating optical and electronic properties. Carbon is very abundant on the Earth and, unlike indium, is a sustainable material.
By taking advantage of high-quality monolayer graphene directly deposited on a transparent substrate using a commercially available metal-organic chemical vapor deposition (MOCVD) system, researchers developed graphene-based OLEDs without the use of metal catalysts or a graphene transfer process. The graphene is patterned using photolithography, and its conductivity is enhanced by doping with nitric acid prior to deposition of the OLED stack.
The electrical and optical performances of the resulting graphene-based OLEDs are identical to the control devices with conventional ITO anodes.
“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 of Queen Mary and Paragraf. “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. ITO-OLEDs are widely used as the touch screens on our mobile phones.”
The research showed that graphene can replace ITO as anodes in OLED devices in a technologically and commercially effective manner.