The Nano research team around professors Helge Weman and Bjørn-Ove Fimland from the Department of Electronic Systems at the Norwegian University of Science and Technology (NTNU) has succeeded in producing light from ultraviolet nanomaterial emitting light emitting diodes (LEDs).
It's the first time anyone has produced ultraviolet light on a graphene surface.
"We have shown that this is possible, which is really exciting," says Ph.D. Candidate Ida Marie Høiaas, Ph.D. Candidate Andreas Liudi Mulyo.
"We have created a new electronic component that has the potential to become a commercial product, it is non-toxic and could be cheaper and more stable and durable than today's fluorescent lamps. We succeed in making the diodes efficient and much cheaper, It is easy to imagine that this equipment will become commonplace in people's homes, which would greatly increase the market potential, "says Høiaas.
This is especially true for UV light with short wavelengths of 100 to 280 nanometers, the so-called UVC light useful for its ability to destroy bacteria and viruses.
Fortunately, the sun's dangerous UVC rays are trapped by the ozone layer and oxygen and do not reach the earth. However, it is possible to generate UVC light that can be used to clean surfaces and hospital equipment or to purify water and air.
The problem today is that many UVC lamps contain mercury. The United Nations Minamata Convention, which entered into force in 2017, provides for measures to phase out mercury degradation and reduce the use of mercury.
The agreement was named after a Japanese fishing village in which the population was poisoned by mercury emissions from a factory in the US 1950s.
Based on graphene
A graphene layer applied to glass forms the substrate for the new diode of the researchers, which generates UV light.
Graphene is a super strong and ultra-thin crystalline material consisting of a single layer of carbon atoms. The researchers succeeded in growing aluminum gallium nitride (AlGaN) nanowires on the graphene grid.
The process takes place in a high-temperature vacuum chamber in which aluminum and gallium atoms are deposited or grown directly on the graphene substrate in the presence of nitrogen plasma.
This technique, known as Molecular Beam Epitaxy (MBE), is being conducted in Japan, where the NTNU research team is collaborating with Professor Katsumi Kishino at Sophia University in Tokyo.
Let There is Light
After the sample has been bred, it is transported to the NTNU NanoLab, where the researchers make metal contacts of gold and nickel on graphene and nanowires. When energy 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 by the nanowires shines through graphene and glass.
Being able to combine nanomaterials in this way and create functional LEDs, says Høiaas.
Multi-million dollar market
An analysis has revealed that the market for UVC products will rise by NOK 6 billion or more About $ 700 million by 2023. The Growing demand for such products and the withdrawal of mercury are expected to result in annual market growth of nearly 40 percent.
Simultaneously with her doctoral thesis at NTNU Høiaas works with the same technology on an industrial platform for CrayoNano. The company is a spin-off of NTNU's Nano Research Group.
Less Power Consumption
UVC LEDs that can replace fluorescent lamps on the market, but CrayoNano's goal is to create far more energy-efficient and cheaper diodes.
One reason that today's UV LEDs are expensive is the substrate of expensive aluminum nitride. Graphene is cheaper to manufacture and uses less material for the LED diode.
Further Development Required
Høiaas believes that many improvements are needed before the process developed at NTNU can be scaled up to industrial scale production levels. Necessary upgrades include conductivity and energy efficiency, more advanced nanowire structures, and shorter wavelengths for generating UVC light.
CrayoNano has made further progress, but its results have not been released yet.
"CrayoNano aims to commercialize the technology sometime in 2022," says Høiaas.
Better solar cells, better LED light and great optical possibilities
Ida Marie Høiaas et al., GaN / AlGaN Nanoscale Ultraviolet Light Emitting Diode Using Bilayer Graph as Substrate and Transparent Electrode, Nano Letters (2019). DOI: 10,1021 / acs.nanolett.8b04607
New nanomaterial replacing mercury (2019, April 25)
retrieved on April 25, 2019
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