図1：ほとんどのLEDは可視光を放射しますが、RIKEN物理学者は人間にとって安全ですが、ウイルスや細菌には致命的な極端な紫外線の狭い領域から放出されるLEDを作成しました。 クレジット：RIKEN
強力なLEDは、人々に安全な状態を維持しながら、表面を効率的に消毒することができます。
理研物理学者は微生物やウイルスにとって致命的ですが、人間にとって安全な高効率LEDを設計しました。 いつかは、人々でいっぱいの部屋で病原体を殺すことによって、国家が感染症の陰から離れるのを助けることができます。
紫外線殺菌ランプは、細菌やウイルスを根絶するのに非常に効果的です。 実際、彼らは病院で日常的に使用されており、表面や医療機器を殺菌します。
Masafumi Joと2人の同僚は、感染症から社会を守るのに役立つLEDを設計しました。 クレジット：RIKEN
このタイプのランプはLEDで構成できるため、エネルギー効率が高くなります。 しかしながら、これらのＬＥＤは損傷を受ける範囲の紫外線を発生する。[{” 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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