Far ultraviolet LED can kill bacteria and virus efficiently without harming people

A highly efficient LED, deadly to microbes and viruses but safe to humans, was developed by three RIKEN physicists. It could one day help countries emerge from the shadow of pandemics by killing pathogens in rooms full of people.

Ultraviolet germicidal lamps are extremely effective in destroying bacteria and viruses and are routinely used in hospitals to sterilize surfaces and medical instruments.

Such lamps can be made with LEDs, which makes them energy efficient. However, these LEDs use ultraviolet light in a range that damages DNA, so they cannot be used near humans. The search is on for efficient LEDs that emit a narrow band of far-ultraviolet light that appears to be both good at disinfecting and safe for humans.

Germicidal LED lamps that work in the absence of people are often made from aluminum, gallium, and nitrogen. By increasing the aluminum content, these LEDs can be modified to operate in a wavelength range that is harmless to humans. But traditionally this has dramatically reduced their power.

To get around this, Masafumi Jo, Yuri Itokazu, and Hideki Hirayama, all at the RIKEN Quantum Optodevice Laboratory, created an LED with a more complex design. They layered together several layers, each containing slightly different percentages of aluminum, while also adding tiny amounts of silicon or magnesium in some layers.

This effectively created an obstacle course for electrons, impeding their movement through the material and trapping them longer in certain areas. This in turn increased the amount of light emitted by the device and decreased the amount of light absorbed.

To determine the best design, the team used computer simulations to model all the possible effects. “We then cultured samples to see if it was effective or not,” says Jo. The main experimental challenge was to precisely control the thickness of each layer. They created an LED that operates in the far ultraviolet and has an output power nearly ten times their previous best.

The COVID-19 pandemic brought a renewed awareness of the importance of being able to destroy viruses and microbes on surfaces. “We trust that our insights and technology will be very useful in protecting society from this and future pandemics,” says Jo.

Jo adds that the trio will strive to further improve the performance of their LEDs. “There’s still a lot of room for improvement in terms of power output and energy efficiency,” he notes.

Your study appears in Applied physics letters.