Scientists use graphene to create diode for cheaper and more durable fluorescent lamps

Helge Weman, CSO at CrayoNano AS and a professor at NTNU, is part of the team that has developed LEDs from nanomaterials that can emit UV light. Photo by NordForsk, provided by Norwegian University of Science and Technology.

Researchers at the Norwegian University of Science and Technology succeeded in creating light-emitting diodes, or LEDs, on a graphene surface.

According to a brief that explains their research, professors Helge Weman and Bjørn-Ove Fimland, and Ph.D. candidates Ida Marie Høiaas and Andreas Liudi Mulyo were able to create a new electronic component that has the potential to become a commercial product. The diode is non-toxic and could turn out to be cheaper, and more stable and durable than today’s fluorescent lamps.

“The problem today is that many UVC lamps contain mercury. The UN’s Minamata Convention, which went into effect in 2017, sets out measures to phase out mercury mining and reduce mercury use,” the scientists’ statement reads. “The convention was named for a Japanese fishing village where the population was poisoned by mercury emissions from a factory in the 1950s.”

The Norwegian group’s invention consists of a layer of graphene placed on a glass surface. This forms the substrate for the new diode that generates UV light.

An early prototype of the UV LED in which researcher Ida Marie Høiaas is working on at CrayoNano. Photo by Mona Sprenger, provided by Norwegian University of Science and Technology..

Graphene is a high-quality form of graphite that ‘evolves’ into a material made of a single layer of carbon atoms. It is super-strong, ultra-thin and crystalline.

Using nanowires of aluminium gallium nitride (AlGaN) grown on graphene lattice and delivered to them from Japan, the researchers make metal contacts of gold and nickel on the graphene and nanowires. When power is sent from the graphene and through the nanowires, they emit UV light.

“Graphene is transparent to light of all wavelengths, and the light emitted from the nanowires shines through the graphene and glass,” Høiaas said. “It’s exciting to be able to combine nanomaterials this way and create functioning LEDs.”

According to the Ph.D. student, who is working with the same technology on an industrial platform for startup CrayoNano, UVC LEDs that can replace fluorescent bulbs are already on the market, but her goal is to create far more energy-efficient and cheaper diodes because one reason that today’s UV LEDs are expensive is that the substrate is made of aluminium nitride. Graphene, on the other hand, is cheaper to manufacture and requires less material for the LED diode.

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