Chemicals or ultraviolet radiation exposure are two methods commonly used sanitise and disinfect areas. The UV radiation is in the 200nm to 300nm range and known to destroy COVID-19 virus. Widespread adoption of this approach requires UV radiation sources that emit sufficiently high doses of UV light. Devices with these high doses exist, but the UV radiation source is typically an expensive mercury-containing gas discharge lamp which requires high power, has a relatively short lifetime, and is bulky.
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The solution is to develop high-performance, UV light emitting diodes, which would be far more portable, long-lasting, energy efficient and environmentally benign. According to Penn State University, these LEDs exist, but applying a current to them for light emission is complicated by the fact that the electrode material has to be transparent to UV light.
"You have to ensure a sufficient UV light dose to kill all the viruses," said Roman Engel-Herbert, Penn State University associate professor of materials science, physics and chemistry. "This means you need a high-performance UV LED emitting a high intensity of UV light, which is currently limited by the transparent electrode material being used."
While finding transparent electrode materials operating in the visible spectrum for displays, smartphones and LED lighting is a long-standing problem, the challenge is said to be more difficult for ultraviolet light.
"There is currently no good solution for a UV-transparent electrode," said Joseph Roth, doctoral candidate in Materials Science and Engineering at Penn State. "Right now, the current material solution commonly employed for visible light application is used despite it being too absorbing in the UV range. There is simply no good material choice for a UV-transparent conductor material that has been identified."
The Penn State team, in collaboration with the University of Minnesota, recognised that the solution might be found in a recently discovered new class of transparent conductors. When theoretical predictions pointed to the material strontium niobate, the researchers obtained films of the material from their collaborators in Japan and tested their performance as UV transparent conductors. While these films held the promise of the theoretical predictions, the researchers needed a deposition method to integrate these films in a scalable way.
Roth said the films were grown successfully using sputtering, marking a critical step towards technology maturation which makes it possible to integrate this new material into ultra violet LEDs at low cost and high quantity.
"While our first motivation in developing UV transparent conductors was to build an economic solution for water disinfection, we now realise that this breakthrough discovery potentially offers a solution to deactivate COVID-19 in aerosols that might be distributed in HVAC systems of buildings," Roth said.
The team's findings are detailed in a paper published in Physics Communications.
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