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Figura 1: La mayoría de los LED emiten luz visible, pero los físicos de RIKEN han creado un LED que emite en una región estrecha del ultravioleta lejano que es seguro para los humanos pero mortal para los virus y las bacterias. Crédito: RIKEN
El potente LED puede desinfectar superficies de manera efectiva sin dejar de ser seguro para los humanos.
Los físicos de RIKEN han creado un diodo emisor de luz altamente eficiente que es letal para los microbios y los virus, pero seguro para los humanos. Algún día podría ayudar a los países a salir de la sombra de una epidemia matando patógenos en habitaciones llenas de gente.
Las lámparas germicidas UV son extremadamente efectivas para matar bacterias y virus. De hecho, se utilizan comúnmente en hospitales para esterilizar superficies e instrumentos médicos.
Masafumi Jo y dos colegas han diseñado un diodo emisor de luz para ayudar a proteger a la sociedad de las epidemias. Crédito: RIKEN
Este tipo de lámparas se pueden construir con LED, lo que las hace energéticamente eficientes. Sin embargo, estos LED producen luz ultravioleta en un rango que es dañino[{» 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
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