Taking solar from microscopic to market

Ted Sargent thinks small.  And he sees the day when making cells for solar PV installations will involve little more than a paint sprayer.  Manufacturers would buy solar cells in a liquid and spray them on panels like paint.

Sargent, a professor in the Electricial and Computer Engineering department at the University of Toronto, is the leader of a project to create solar cells using tiny particles whose size is measured in nanometres.  

“A nanometre is a billionth of a metre, so it’s incredibly small.  It’s actually the same size scale molecules are configured on,” explains Sargent.

He says this scale is interesting for two reasons. “First,” he says, “we can disperse these particles in a solvent so it’s a bit like making a paint.  But our paint consists of a semiconductor that we can make into a solar cell.”

He adds that the second advantage of using nanoparticles to make solar cells is that they can be configured to capture a very broad range of the sun’s light spectrum.

Sargent has been working on the nanometre concept since 2005.  He and his team at U of T have proven the concept can work but they haven’t made the process efficient enough to be commercially viable.  This means they aren’t yet able to harvest enough of the sun’s energy to justify the cost of building and installing the technology.

“We’ve gotten about half of the way towards what we consider to be a very compelling commercial opportunity. Our hope is that in a small number of years we can get to very exciting efficiencies.  Then we’ll need to proceed to scale up our prototypes.  At the moment they are measured in centimetres.  Obviously to make a big solar cell we’re thinking of covering square metres of, say, somebody’s roof.”

Sargent’s lab on the University of Toronto’s St. George campus is bustling with post-graduate students in white lab coats who are building and testing these prototypes.  For many of them, this is a dream assignment.

“Renewable energy is a passion of mine,” says Kyle Kemp, a PhD student who is testing the latest round of prototypes from the lab. “Ultimately, I hope I can be a part of progressing the field at large.  It would also be nice to get a device up the level where it could be commercialized and be available for sale.”

The small solar cell he’s testing as he explains his passion turns out to be about five percent efficient, meaning it can harness about five percent  of the energy it’s exposed to during the test.  This is a good result, close to some of the best results they’ve achieved to date.

Because the project still has a ways to go before it might attract investors, it relies on support from the university and grants from organizations such as the Ontario Power Authority with its technology development fund.

As Professor Sargent explains: “The OPA is enabling us to take these materials the final way toward a proven performance, proven robustness, proven capacity to scale, so that we should then be in a position to go to investors and to take this technology commercial.”

And the results might not just be lucrative, but they could also benefit the world at large.

“Renewable energies, solar in particular, offer a lot of potential in emerging economies, where people in some cases may not even be connected to an electricity grid. And solar stations or even solar cells that allow you to charge a battery to run a light bulb at night can transform whole societies.”