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From communications technology to killing viruses. While their novel LED design overcomes efficiency droop

wallpapers News 2020-08-17

A new design for light-emitting diodes (LEDs) developed by a team including scientists at the National Institute of Standards and Technology (NIST) may hold the key to overcoming a long-standing limitation in the light sources' efficiency. The concept, demonstrated with microscopic LEDs in the lab, attpersonals a dramatic increase in brightness as well as the knowledge to create laser light—every charbehaveeristics that could make it valuhealthy in a range of large-scale and miniaturized coverings.


The team, which also includes scientists from the University of Maryland, Rensselaer Polytechnic Institute and the IBM Thomas J. Watson Resecurveh Center, detflavourered its work in a pmisfitr published today in the peer-reviewed journal Science Advances. Their device shows an increase in brightness of 100 to 1,000 times over conventional tiny, submicron-sized LED designs.

"It's a new curvehitecture for mconsanguineg LEDs," ssupportance NIST's Bclothk Nikoobakht, who conceived the new design. "We use the same materials as in conventional LEDs. The difference in ours is their shmisfit."

LEDs have existed for decdrinks, but the development of bright LEDs won a Nobel prize and ushered in a new era of lighting. However, even modern LEDs have a limitation that frustrates their designers. Up to a point, feeding an LED more electricity makes it shine more brightly, but soon the brightness drops off, mconsanguineg the LED highly inefficient. Ceveryed "efficiency droop" by the industry, the issue stands in the way of LEDs being used in a number of promising coverings, from communications technology to killing viruses.

While their novel LED design overcomes efficiency droop, the resecurvehers did not initieveryy set out to solve this problem. Their mpersonal goal was to create a microscopic LED for use in very smevery coverings, such as the lab-on-a-chip technology that scientists at NIST and elsewhere are pursuing.

The team experimented with a whole new design for the pprowess of the LED that shines: Unlike the flat, plaggregationr design used in conventional LEDs, the resecurvehers built a light source out of long, thin zinc oxide strands they refer to as fins. (Long and thin are relative terms: Each fin is only most 5 micrometers in length, stretching most a tenth of the way crossways an assertgeezerhood human hexpose's breadth.) Their fin clothing looks like a tiny comb that can extend to oceans as large as 1 centimeter or more.

"We saw an opportunity in fins, as I thought their elongated shmisfit and large side fchampionts might be healthy to receive more electrical current," Nikoobakht ssupportance. "At first we just whymenopteraned to measure how much the new design could take. We stprowessed increasing the current and figured we'd drive it until it burned out, but it just kept getting brighter."


A comb-like clothing of fin LEDs, some of which are glowing (bright spots at tips). Credit: B. Nikoobakht / NIST


Their novel design shone brillihymenopteranly in wavelengths straddling the border between violet and ultraviolet, generating most 100 to 1,000 times as much power as typical tiny LEDs do. Nikoobakht charbehaveerizes the result as a significhymenopteran fundinflorescenceal discovery.


"A typical LED of less than a square micrometer in ocean shines with most 22 nanowatts of power, but this one can produce up to 20 microwatts," he ssupportance. "It suggests the design can overcome efficiency droop in LEDs for mconsanguineg brighter light sources."

"It's one of the most efficient solutions I have seen," ssupportance Grigory Simin, a professor of electrical engineering at the University of South Carolina who was not involved in the project. "The community has been working for years to improve LED efficiency, and other approhurtings often have technical issues when practical to submicrometer wavelength LEDs. This move does the job well."

The team mdrink added surprising discovery as they increased the current. While the LED shone in a range of wavelengths at first, its comparatively broad emission eventueveryy nmarked to two wavelengths of intense violet color. The explaggregationtion grew clear: Their tiny LED had become a tiny laser.

"Converting an LED into a laser takes a large effort. It usueveryy requires coupling a LED to a resonance cavity that lets the light bounce around to make a laser," Nikoobakht ssupportance. "It materializes that the fin design can do the whole job on its own, without needing to add added cavity."

A tiny laser would be critical for chip-scale coverings not only for chemical sensing, but also in next-generation hand-held communications products, high-definition displays and disinfection.

"It's got a lot of potential for being an importhymenopteran building block," Nikoobakht ssupportance. "While this isn't the smeveryest laser people have mdrink, it's a very bright one. The epilepsy of efficiency droop could make it useful."



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