The Nano-research team, led by Professors Helge Weman and Bjorn-Ove Fimland of the Electronic Systems Department of the Norwegian University of Science and Technology, managed to create LEDs or LEDs from a nanomaterial that emits ultraviolet light.
This is the first time anyone has created ultraviolet light on the surface of graphene.
"We have shown that it is possible, which is really exciting," says the doctor. Candidate Ida Marie Hoyais, who works on the doctoral project candidate Andreas Lloyd Muloy.
"We have created a new electronic component that has the potential to become a commercial product. It is non-toxic and may be cheaper and more stable and durable than today's fluorescent lamps. If we can make the diodes effective and efficient much cheaper, it is easy to imagine that this equipment is becoming commonplace in people's homes. This would greatly increase market potential, "said Hoaas.
Dangerous – but useful
Although it is important to prevent too much exposure to solar ultraviolet radiation, ultraviolet light also has many useful properties.
This applies especially to UV light with short wavelengths of 100-280 nanometers, called UVC light, which is especially useful for its ability to kill bacteria and viruses.
Fortunately, the dangerous UVC rays from the sun are trapped by the ozone layer and oxygen and are not reaching the Earth. But it is possible to create 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 UN Convention on Minamas, which came into force in 2017, sets out measures to phase out mercury extraction and reduce mercury use.
The convention was declared a Japanese fishing village where the population was poisoned by mercury emissions from a factory in the 1950s.
Building a graphene
The graphite layer on the glass forms a substrate for the new researchers' diode, which generates ultraviolet light.
Graphene is a super-strong and ultra-thin crystalline material consisting of one layer of carbon atoms. Researchers have succeeded in growing nanopowders of aluminum gallium nitride (AlGaN) on the graphene grid.
The process is carried out in a high-temperature vacuum chamber where the aluminum and gallium atoms are deposited or grown directly on the graphene substrate with high precision and in the presence of nitrogen plasma.
This process is known as molecular beam epitaxy (MBE) and is conducted in Japan, where NTNU's research team collaborates with Professor Katsumi Chishino at the Tokyo University of Technology.
let it be light
After cultivating the sample, it is transported to NTNU NanoLab, where researchers make metallic contacts of gold and nickel on graphene and nanopowders. When the power is sent from graphene and through nanowires, they emit UV light.
Graphene is transparent to light from all wavelengths, and the light emanating from nanowires shines through graphene and glass.
"It is exciting to be able to combine nanomaterials in this way and create functioning LEDs," says Hiaais.
The analysis estimated that the market for UVC products would increase by NOK 6 billion, or approximately US $ 700 million. from now to 2023. The growing demand for such products and the gradual elimination of mercury is expected to lead to an annual market increase of almost 40%.
Along with her doctor. research at NTNU, Høiaas works with the same industry platform technology for CrayoNano. The company is a specialist from the NTNU Nano Research Group.
Use less electricity cheaper
UVC LEDs that can replace fluorescent bulbs are already on the market, but CrayoNano's goal is to create much more energy-efficient and cheaper diodes.
According to the company, one of the reasons why today's UV LEDs are expensive is that the substrate is made of expensive aluminum nitride. Graphene is cheaper to produce and requires less material for LED diodes.
Further development is needed
Hoiaas believes that much improvement is needed before the process developed in NTNU can be increased to the level of industrial production. Necessary improvements include conductivity and energy efficiency, more sophisticated nanowire structures, and shorter wavelengths to create UVC light.
CrayoNano has advanced yet, but their results have not yet been published.
"CrayoNano's goal is to commercialize the technology somewhere in 2022," says Hiaais.
Better solar cells, better LED light and enormous optical capabilities
Ida Marie Høiaas et al., GaN / AlGaN nanocolour UV light diode using a dual layer graphite substrate and a transparent electrode, Nano Letters (2019). DOI: 10.1021 / acs.nanolett.8b04607
The new nanomaterial will replace mercury (2019, 25 April)
drawn up on 25 April 2019
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