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Quantum dots are key to spray-on solar cells

Technology News |
By eeNews Europe

Illan Kramer and colleagues from the University of Toronto have invented a way to spray solar cells onto flexible surfaces using miniscule light-sensitive materials known as colloidal quantum dots (CQDs) – a major step toward making spray-on solar cells easy and cheap to manufacture.

“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 The
Edward S. Rogers Sr. Department of Electrical & Computer Engineering at the University of Toronto and IBM Canada’s Research and Development Centre.

Solar-sensitive CQDs printed onto a flexible film could be used to coat all kinds of weirdly shaped surfaces, from patio furniture to an airplane’s wing. A surface the
size of your car’s roof wrapped with CQD-coated film would produce enough energy to power three 100-Watt light bulbs – or 24 compact fluorescents.

Until now, it was only possible to incorporate light-sensitive CQDs onto surfaces through batch processing – an inefficient, slow and expensive assembly-line approach to chemical coating. SprayLD blasts a liquid containing CQDs directly onto flexible surfaces, such as film or plastic, like printing a newspaper by applying ink onto a
roll of paper. This roll-to-roll coating method makes incorporating solar cells into existing manufacturing processes much simpler. In two recent papers in the
journals Advanced Materials and Applied Physics Letters, Kramer showed that the sprayLD method can be used on flexible materials without any major loss in solar-cell
efficiency.

Kramer built the sprayLD device using parts that are readily available and affordable going so far as to source a spray nozzle used in steel mills to cool steel with a fine mist of water and using a few regular air brushes from an art store.

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

“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,” said Professor Ted Sargent (ECE), vice dean, research in the Faculty of Applied Science & Engineering at University of Toronto and Kramer’s
supervisor. “We were thrilled when this attractively manufacturable spray-coating process also led to superior performance devices showing improved control and
purity.”

In a third paper in the journal ACS Nano, Kramer and his colleagues used IBM’s BlueGeneQ supercomputer to model how and why the sprayed CQDs perform just as well as – and in some cases better than – their batch-processed counterparts. This work was supported by the IBM Canada Research and Development Centre, and by King Abdullah University of Science and Technology.

Related articles and links:

https://news.engineering.utoronto.ca

News articles:

Quantum dot solar concentrator opens energy harvesting window

Nanoengineering quadruples carrier multiplication in quantum dots

Are quantum dot solar cells commercially viable?


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