Game-changing UV light kills bacteria and viruses without harming humans

Most LEDs emit visible light, but RIKEN physicists have created an LED that emits in a narrow far ultraviolet region, safe for humans, but deadly for viruses and bacteria. (CREDIT: Creative Commons)

Three RIKEN physicists have developed a high-efficiency LED that is deadly to germs and viruses but harmless to humans. He might one day help countries emerge from the shadow of pandemics by killing pathogens in rooms full of people.

UV germicidal lamps are extremely effective at killing bacteria and viruses, and they are commonly used in hospitals to sterilize surfaces and medical instruments.

Such lamps can be manufactured using LEDs, which makes them energy efficient. But these LEDs use ultraviolet light in a range that damages DNA, and therefore shouldn’t be used around people. The hunt is on to develop efficient LEDs that emit light in a narrow band of far ultraviolet light that appears to be good at disinfecting and safe for humans.

Germicidal LED lamps that work in the absence of a person are often made of aluminum, gallium and nitrogen. By increasing the amount of aluminum they contain, these LEDs can be modified to operate in the wavelength range that is safe for humans. But traditionally, this sharply reduced their power.

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To get around this, Masafumi Joe, Yuri Itokazu, and Hideki Hirayama at the RIKEN Quantum Optodevices Lab created a more complex LED design. They put together several layers, each containing slightly different proportions of aluminum, and added small amounts of silicon or magnesium to some of the layers.

This effectively created an obstacle course for the electrons, preventing them from moving through the material and keeping them longer in certain areas. This, in turn, increased the amount of light emitted by the device and reduced the amount of light it absorbed.

To determine the best design, the team used computer simulations to simulate every possible effect. “Then we grew the samples to see if it was effective or not,” says Joe. The biggest experimental challenge was precisely controlling the thickness of each layer.

They created a far-ultraviolet LED with a power output almost ten times higher than their previous best.

The COVID-19 pandemic has brought new awareness of the importance of being able to kill viruses and germs on surfaces. “We believe that our discoveries and technologies will be very useful in protecting society from this and future pandemics,” says Joe.

Most LEDs emit visible light, but RIKEN physicists have created an LED that emits in a narrow far ultraviolet region, safe for humans, but deadly for viruses and bacteria. (CREDIT: GIFTOSTOCK/SCIENTIFIC PHOTO LIBRARY)

Joe adds that the trio will be looking to further improve the performance of their LEDs. “There is still a lot of room for improvement in power output and energy efficiency,” he notes.

Their study is published in Applied Physics Letters.

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Note. Materials provided above by Riken. Content can be edited for style and length.

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