Junkyard Parts Lead to New Spray on Process for Quantum Dots

Novel process can apply quantum dots onto nearly every surface

2 min read
Junkyard Parts Lead to New Spray on Process for Quantum Dots
University of Toronto

For years, the University of Toronto research team helmed by Edward H. Sargent has been setting the standards for the use of colloidal quantum dots—including setting conversion efficiency records in photovoltaics and pointing towards their use in infrared optoelectronics.

Now researchers from Sargent’s research team, led by Illan Kramer, have demonstrated that colloidal quantum dots (CQDs) can be sprayed onto a flexible film and used to coat just about anything.

“My dream is that one day you’ll have two technicians with Ghostbusters backpacks come to your house and spray your roof,” said Kramer, a post-doctoral fellow with Sargent’s group, in a press release.

The new process, which Kramer has dubbed “sprayLD,” a play on the term atomic layer deposition (ALD), lays a liquid containing the quantum dots directly onto flexible surfaces, such as film or plastic. The layer of CQDs is laid on in a roll-to-roll process not unlike how newspaper printing presses operate. This makes the process fairly easy to incorporate into other manufacturing methods, say the researchers.

In the research, which was published in the journals Advanced Materials and Applied Physics Letters, Kramer demonstrated that the resulting CQDs do not lose any of their energy conversion efficiency in the process.

Prior to this research, the only way to get light-sensitive colloidal quantum dots onto a substrate involved batch processing, which is a chemical coating process that is comparatively slow and expensive. For this new roll-to-roll process, Kramer was able to fashion the deposition device out of a spray nozzle used in steel mills for cooling steel with a fine mist of water, plus a few regular airbrushes found in any art store.

“This is something you can build in a Junkyard Wars fashion, which is basically how we did it,” says Kramer. “We think of this as a no-compromise solution for shifting from batch processing to roll-to-roll.”

The device can be seen in operation in the video below.

Commenting on the research, Sargent said: “As quantum dot solar technology advances rapidly in performance, it’s important to determine how to scale them and make this new class of solar technologies manufacturable. We were thrilled when this attractively-manufacturable spray-coating process also led to superior performance devices showing improved control and purity.”

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Smokey the AI

Smart image analysis algorithms, fed by cameras carried by drones and ground vehicles, can help power companies prevent forest fires

7 min read
Smokey the AI

The 2021 Dixie Fire in northern California is suspected of being caused by Pacific Gas & Electric's equipment. The fire is the second-largest in California history.

Robyn Beck/AFP/Getty Images

The 2020 fire season in the United States was the worst in at least 70 years, with some 4 million hectares burned on the west coast alone. These West Coast fires killed at least 37 people, destroyed hundreds of structures, caused nearly US $20 billion in damage, and filled the air with smoke that threatened the health of millions of people. And this was on top of a 2018 fire season that burned more than 700,000 hectares of land in California, and a 2019-to-2020 wildfire season in Australia that torched nearly 18 million hectares.

While some of these fires started from human carelessness—or arson—far too many were sparked and spread by the electrical power infrastructure and power lines. The California Department of Forestry and Fire Protection (Cal Fire) calculates that nearly 100,000 burned hectares of those 2018 California fires were the fault of the electric power infrastructure, including the devastating Camp Fire, which wiped out most of the town of Paradise. And in July of this year, Pacific Gas & Electric indicated that blown fuses on one of its utility poles may have sparked the Dixie Fire, which burned nearly 400,000 hectares.

Until these recent disasters, most people, even those living in vulnerable areas, didn't give much thought to the fire risk from the electrical infrastructure. Power companies trim trees and inspect lines on a regular—if not particularly frequent—basis.

However, the frequency of these inspections has changed little over the years, even though climate change is causing drier and hotter weather conditions that lead up to more intense wildfires. In addition, many key electrical components are beyond their shelf lives, including insulators, transformers, arrestors, and splices that are more than 40 years old. Many transmission towers, most built for a 40-year lifespan, are entering their final decade.

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