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MAY 2020  
Environmental Research
Ultraviolet LEDs: Prove Effective in Eliminating Coronavirus from Surfaces

Researchers at UC Santa Barbara’s Solid State Lighting & Energy Electronics Center (SSLEEC) are developing ultraviolet (UV) LEDs that have the ability to decontaminate surfaces-and potentially air and water-that have come in contact with the coronavirus. 'One major application is in medical situations-the disinfection of personal protective equipment, surfaces, floors, within the HVAC systems, etc.,'said materials doctoral researcher Christian Zollner, whose work centres on advancing deep UV light LED technology for sanitation and purification purposes. He added that a small market already exists for UV-C disinfection products in medical contexts. Indeed, much attention of late has turned to the power of UV light to inactivate the novel coronavirus. As a technology, UV light disinfection has been around for a while. UV light shows a lot of promise: SSLEEC member company Seoul Semiconductor in early April 2020 reported a ‘99.9 per cent sterilization of coronavirus (COVID-19) in 30 seconds’ with their UV LED products. Their technology currently is being adopted for automotive use, in UV LED lamps that sterilize the interior of unoccupied vehicles.

It is worth noting that not all UV wavelengths are alike. UV-A and UV-B-the types we get a lot of on the Earth-have important uses, but the rare UV-C is the ultraviolet light of choice for purifying air and water and for inactivating microbes. These can be generated only via human-made processes. ‘UV-C light in the 260-285 nm range most relevant for current disinfection technologies is also harmful to human skin, so for now it is mostly used in applications where no one is present at the time of disinfection,’ Zollner said. In fact, the World Health Organization warns against using UV disinfection lamps to sanitize hands or other areas of the skin as even brief exposure to UV-C light can cause burns and eye damage.

Before the COVID-19 pandemic gained global momentum, materials scientists at SSLEEC were already at work advancing UV-C LED technology. This area of the electromagnetic spectrum is a relatively new frontier for solid-state lighting; UV-C light is more commonly generated via mercury vapour lamps and, according to Zollner, ‘many technological advances are needed for the UV LED to reach its potential in terms of efficiency, cost, reliability, and lifetime.’ In a letter published in the journal ACS Photonics, the researchers reported a more elegant method for fabricating high-quality deep-ultraviolet (UV-C) LEDs that involves depositing a film of the semiconductor alloy aluminium gallium nitride (AlGaN) on a substrate of silicon carbide (SiC)-a departure from the more widely used sapphire substrate.

According to Zollner, using silicon carbide as a substrate allows for more efficient and cost-effective growth of high-quality UV-C semiconductor material than using sapphire. This, he explained, is due to how closely the materials’ atomic structures match up.

'As a general rule of thumb, the more structurally similar (in terms of atomic crystal structure) the substrate and the film are to each other, the easier it is to achieve high material quality,' he said. The better the quality, the better the LED’s efficiency and performance.

Sapphire is dissimilar structurally, and producing material without flaws and misalignments often requires complicated additional steps. Silicon carbide is not a perfect match, but it enables a high quality without the need for costly, additional methods. In addition, silicon carbide is far less expensive than the 'ideal- aluminium nitride substrate, making it more mass production-friendly, according to Zollner.

Portable, fast-acting water disinfection was among the primary applications the researchers had in mind as they were developing their UV-C LED technology; the diodes’ durability, reliability and small form factor would be a game changer in less developed areas of the world where clean water is not available. The emergence of the COVID-19 pandemic has added another dimension. As the world races to find vaccines, therapies and cures for the disease, disinfection, decontamination and isolation are the few weapons we have to defend ourselves, and the solutions will need to be deployed worldwide. In addition to UV-C for water sanitation purposes, UV-C light could be integrated into systems that turn on when no one is present, Zollner said. ‘This would provide a low-cost, chemical-free and convenient way to sanitize public, retail, personal, and medical spaces,’ he further said.

For the moment, however, it is a game of patience, as Zollner and colleagues wait out the pandemic. Research at UC Santa Barbara has slowed to a trickle to minimize person-to-person contact. ‘Our next step, once research activities resume at UCSB, is to continue our work on improving our AlGaN/SiC platform to hopefully produce the world’s most efficient UV-C light emitters,’ he said. 

Source: www.sciencedaily.com

   
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Nominations open for CSP Today India awards 2013


The inaugural CSP Today India awards ceremony takes place on March 12, and CSP developers, EPCs, suppliers and technology providers can now be nominated.

CSP has made tremendous progress since the announcement of the Jawaharlal Nehru National Solar Mission in 2010. With Phase I projects now drawing closer to completion, the first milestone in India’s CSP learning curve is drawing closer. CSP Today has chosen the next CSP Today India conference (12-13 March, New Delhi) as the time for the industry to reflect upon its progress and celebrate its first achievements.

At the awards ceremony, industry leaders will be recognized for their achievements in one of 4 categories: CSP India Developer Award, CSP India Engineering Performance Award, CSP India Technology and Supplier Award, and the prestigious CSP India Personality of the Year.

Matt Carr, Global Events Director at CSP Today, said at the opening of nominations that “CSP Today are excited to launch these esteemed awards, which will enhance the reputation of their recipients. I am particularly excited to launch the CSP India Personality of the Year award, a distinguished honor for the industry figure deemed worthy by their peers.”

All eyes will be on the CSP Today India 2013 Awards when nomination entry closes on February 4 and the finalists are announced on February 11. The awards are open to all industry stakeholders to nominate until February 4 at
http://www.csptoday.com/india/awards-index.php or by e-mail to [email protected]

Contact:
Matt Carr
+44 (0) 20 7375 7248
[email protected]