Scientists create a new method to spray solar cells onto flexible surfaces that could help make it easier to mass produce.

Illan Kramer of IBM Canada. (Photo credit: Marit Mitchell/University of Toronto)

Illan Kramer of IBM Canada. (Photo credit: Marit Mitchell/University of Toronto)

We were intrigued when we spotted an article about spray-on solar power on the University of Toronto Engineering News site and decided to take a closer look.

The story explains how Illan Kramer and his colleagues “invented a new way to spray solar cells onto flexible surfaces using miniscule light-sensitive materials known as colloidal quantum dots (CQDs).” This process could help make spray-on solar cells easier to mass produce.

Not Impossible Now interviewed Kramer by email to learn more about spray-on solar power. 

NIN: What is your job title and how are you affiliated with the University of Toronto? 

Illan Kramer: I am a postdoctoral fellow with IBM Canada’s Research and Development Centre through the SOSCIP (Southern Ontario Smart Computing Innovation Platform) program. In this far-from-typical arrangement, I am an IBM employee who works with a university research group — in this case Ted Sargent’s group at the University of Toronto. I get my day-to-day research guidance from the university, while I get additional support — both technical and administrative — from IBM. 

NIN: What inspired you to create spray-on solar power technology? 

Kramer: Without fail, every solar cell group working on next-generation materials (including the Ted Sargent's group at the University of Toronto) loves to talk about how their material holds the potential for low-cost manufacturing through roll-to-roll processes similar to newspaper printing presses.

Unfortunately, that's usually where the discussion ends, and they go back to using processes that cannot be manufactured in a roll-to-roll way. We decided to put our money where our mouth is and try to build a research scale process that would enable roll-to-roll processing. Spray-coating seemed like a logical fit, so we started by buying a few art-store air brushes and the project evolved from there.

Can you describe how the spray-on process works? 

Kramer: The materials we work with are semiconducting nanoparticles suspended in a liquid. They are so small that you can't see them, but they make the liquid black, like an ink. Our aim was to spray such a fine mist that roughly a single, continuous layer of nanoparticles was deposited per spray cycle and then treated and rinsed to render the film conductive, rather than its initial, insulating state. 

Because we deposit and treat each nanoparticle layer one-at-a-time, we termed the process “sprayLD,” a play on the scientific process known as “ALD” (atomic layer deposition), where a single atom is deposited at a time and then treated. Once the desired number of deposit-treat-rinse-repeat cycles is achieved, the film is done. The process is so robust that we were able to make pretty good devices even on flexible films and on unconventional shapes, like a hemisphere. 

Illan Kramer’s lab. (Photo credit: Marit Mitchell/University of Toronto)

Illan Kramer’s lab. (Photo credit: Marit Mitchell/University of Toronto)

In an article for the University of Toronto Engineering News, you said that your dream is to have technicians with Ghostbusters backpacks come to your house and spray your roof. How soon do you think this will be possible? 

Kramer: This is a long way off, but that doesn't mean that there aren't some very compelling intermediate steps that could be commercially interesting. Specifically, the newspaper printing model, where you have a factory (or a printing press) that is able to continuously spray solar cell material over an area of many hundreds of meters seems like a good start model for low-cost, high-volume manufacturing. We would hope that something like this could be a reality in a five-to-10-year time period. 

What advice do you have for young science and technology students who have a unique idea like yours but aren’t sure how to take the first step? 

Kramer: There are a lot of experienced and talented people out there who probably either have a similar idea to or are receptive to yours. Seek out their help, advice or even mentorship. Working with the Sargent group has been great because even when the project — as all projects do — seemed to be hitting a wall, there was never a shortage of ideas on how to move forward. I’m not sure the model of the engineer or scientist tinkering away alone in his garage is the most effective. It’s far more efficient to collaborate. You’ll get a lot farther a lot faster if you stand on the shoulders of giants rather than reinventing the wheel.