Abbildung 1: Die meisten LEDs emittieren sichtbares Licht, aber RIKEN-Physiker haben eine LED entwickelt, die in einem schmalen Bereich ferne Ultraviolettstrahlen emittiert und für Menschen ungefährlich, aber für Viren und Bakterien tödlich ist. Kredit: RIKEN
Eine leistungsstarke LED-Lampe kann Oberflächen effizient desinfizieren und gleichzeitig die Sicherheit von Personen gewährleisten.
RIKEN-Physiker haben eine hocheffiziente LED-Lampe entwickelt, die antimikrobiell und antiviral, aber sicher für den Menschen ist. Eines Tages könnte es Ländern helfen, aus dem Schatten von Epidemien herauszukommen, indem es Krankheitserreger in Räumen voller Menschen tötet.
UV-Entkeimungslampen sind hochwirksam bei der Abtötung von Bakterien und Viren. Tatsächlich werden sie routinemäßig in Krankenhäusern verwendet, um medizinische Oberflächen und Instrumente zu sterilisieren.
Masafumi Jo und zwei Mitarbeiter haben eine LED-Lampe entworfen, die dazu beiträgt, die Gesellschaft vor Epidemien zu schützen. Kredit: RIKEN
Lampen dieser Art können mit LEDs hergestellt werden, was sie energieeffizient macht. Diese LED-Leuchten erzeugen jedoch ultraviolettes Licht in einem schädlichen Bereich[{“ attribute=““>DNA and therefore cannot be used around people. The search is on to develop efficient LEDs that shine light within a narrow band of far-ultraviolet light that appears to be both good at disinfecting while remaining safe for people.
Germicidal LED lamps that operate in the absence of humans are often made from aluminum, gallium, and nitrogen. By increasing the amount of aluminum they contain, these LEDs can be modified to work in a wavelength region that is safe for humans. This approach has been used before but has resulted in dramatically reduced power.
To work through this issue, three physicists at RIKEN Quantum Optodevice Laboratory, Masafumi Jo, Yuri Itokazu, and Hideki Hirayama, created an LED with a more complex design. They sandwiched together multiple layers, each containing slightly different proportions of aluminum. In addition, in some layers they also added tiny amounts of silicon or magnesium.
This effectively created an obstacle course for electrons, hindering their movement across the material and trapping them for longer in certain areas. This resulted in an increased amount of light emitted by the device and a reduced amount absorbed by it.
The team used computer simulations to model all possible effects to help pin down the ideal design. “We then grew samples to see if it was effective or not,” Jo says. Precisely controlling the thickness of each layer was the biggest experimental challenge. They ended up with an LED operating in the far ultraviolet, with an output power almost ten times higher than their previous best.
The COVID-19 pandemic brought a new consciousness of the importance of being able to eradicate viruses and microbes on surfaces. “We trust that our findings and technologies will be very useful for safeguarding society against this and future pandemics,” says Jo.
Jo adds that the trio will strive to improve their LED’s performance even further. “There’s still much room for improvement in the output power and the power efficiency,” he notes.
Reference: “Milliwatt-power far-UVC AlGaN LEDs on sapphire substrates” by Masafumi Jo, Yuri Itokazu and Hideki Hirayama, 25 May 2022, Applied Physics Letters.
DOI: 10.1063/5.0088454