図 1: ほとんどの LED は可視光を放射しますが、理化学研究所の物理学者は、遠紫外線の狭い領域で放射し、人間には安全ですが、ウイルスやバクテリアには致命的な LED を作成しました。 クレジット：理化学研究所
強力な LED ランプは、人々の安全を保ちながら表面を効率的に消毒できます。
理化学研究所の物理学者は、抗菌性および抗ウイルス性でありながら人間にとって安全な高効率の LED ランプを設計しました。 いつの日か、人でいっぱいの部屋で病原体を殺すことで、国々が流行の影から抜け出すのを助けることができるかもしれません.
紫外線殺菌灯は、細菌やウイルスを殺すのに非常に効果的です。 実際、医療用表面や器具を滅菌するために、病院で日常的に使用されています。
城正史と 2 人の共同研究者は、疫病から社会を守るのに役立つ LED ランプを設計しました。 クレジット：理化学研究所
このタイプのランプは LED を使用して作成できるため、エネルギー効率が高くなります。 ただし、これらの LED ライトは、有害な範囲の紫外線を生成します。[{” 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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