Solar Cells To Cure Coal Fever With Quantum Dots

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The new “American Energy Dominance” energy policy aims to raise up coal and push down renewables, but as the saying goes, cream rises to the top. No matter which way the policy winds blow, the pace of innovation in the solar industry beats coal any day of the week. Among the latest developments, new “quantum dot” solar cells are poised to enter the market, helping to keep the cost of solar power sliding downhill while coal goes up.

The Quantum Dot Solar Cell Difference

The wait for the quantum dot solar cell of the future has been a long one. Quantum dots began surfacing on the CleanTechnica radar more than 10 years ago, after researchers at Los Alamos National Laboratory described how their bespoke quantum dots could be applied to engineer see-through windows that double as solar modules.

The discovery of quantum dots goes back to the 1980s, when researchers discovered that nanoparticles of matter in a solution behave differently from larger chunks of the same material. “Quantum dots are ultra-small bits of semiconductor matter that can be synthesized with nearly atomic precision via modern methods of colloidal chemistry,” Los Alamos explains, with colloidal referring to the field of solutions-based chemistry.

“Their emission color can be tuned by simply varying their dimensions,” the lab adds. “Color tunability is combined with high emission efficiencies approaching 100%” (see more quantum dot background here).

“Colloidal quantum dots are electronic materials and because of their astonishingly small size (typically 3-20 nanometers in dimension) they possess fascinating optical properties,” adds the US Department of Energy’s National Renewable Laboratory, which began tracking the efficiency of quantum dot solar cells in 2010.

There being no such thing as a free lunch, quantum dots can eat light, reducing the overall efficiency of a solar cell. Still, science loves a challenge. When NREL’s solar conversion efficiency tracker first added quantum dot solar cells, a lead sulfide formula yielded the best results at a rate of just 2.9%. By 2024, the figure for lead sulfide jumped to 12%, and in January of this year NREL researchers patted themselves on the back for achieving 13.4%.

“The improvement from the initial efficiency to the previous record came from better understanding of the connectivity between individual quantum dots, better overall device structures and reducing defects in quantum dots,” NREL explains.

Meanwhile, Solar Cells Are Coming For Your Fossil Fuels

Of course, solar cells that exceed 13.4% by a wide margin are already on the market, which raises the question of why quantum dots are needed, let alone wanted. The answer lies in the potential to lower the cost of multi-material solar cells while improving efficiency. Solar energy is already the most economical and accessible means of adding more electricity to the nation’s grid. It could get even more economical with the introduction of new solar conversion materials that lend themselves to low-cost, high-volume manufacturing processes.

The emerging combination of perovskite in tandem with silicon is one example, and now quantum dots are set to provide another pathway. Specifically, they are being put to work improving the solar conversion of CdTe (cadmium telluride) thin-film solar cells, to be deployed in a bifacial solar panel format by the US manufacturer First Solar.

The action began to surface on the CleanTechnica radar earlier this year, when the US quantum dot startup UbiQD acquired the perovskite innovator BlueDot, and it has been very busy since then. In July, UBiQD formed an agreement with First Solar, aimed at boosting the efficiency of First Solar’s bifacial solar panels.

Bifacial solar panels do just what they say. They collect solar energy from both sides. The technology has opened up new opportunities for solar deployment, one good example being the field of agrivoltaics, where bifacial solar panels can double as fencing to save more room for farming. Solar installers are beginning to pitch them for backyard use, too.

To gild the green lily, First Solar estimates that its bifacial solar panels will be 20% more efficient when a thin film of quantum dots is layered onto the back side.

More And Better Bifacial Solar Panels

In the latest development, UbiQE just announced that it has nailed down $6 million in growth capital from the Silicon Valley Bank branch First Citizens Bank, building on a funding relationship that goes back to 2017. The loan follows a new $20 million round of Series B funding along with the First Solar agreement.

The $6 million loan is relatively small in comparison, but a little goes a long way in the field of quantum dots. The debt financing will enable UbiQD to upgrade and scale up its manufacturing processes.

On its part, SVB apparently did not get the message about propping up old coal power plants. “UbiQD is driving critical innovation in quantum dot technology and manufacturing and is well positioned to expand production to support key sectors including agriculture and solar energy,” said Trent Walker, referring to the potential for using quantum dots to enhance greenhouse glass as well as solar cells.

In a move that indicates a keen interest in the greenhouse market, UbiQD also announced the appointment of Tony Beams as Chief Financial Officer. The new CFO comes in with a strong background in the high-tech vertical farming field. “Both the SVB financing and Beams’appointment are designed to align the company’s capital structure, talent, and infrastructure with its rapidly expanding commercial pipeline,” UbiQD explains.

New Solar Cells, New Hope For US Farmers

Quantum dots and bifacial solar panels are just two examples of the ways in which solar energy is being deployed to help US farmers earn revenue and conserve farmland since the early 2000s.

Coal, not so much. All else being equal, federal energy policy should be supporting farmers with opportunities to grow their business and gain access to an economical and widely available domestic energy resource. Instead, last August the US Department of Agriculture halted low-cost loans for solar equipment, while the Department of Energy has earmarked millions in taxpayer dollars to bring old coal power plants back to life.

On the brighter side, the fever dream of a coal revival will not last long. In addition to the rise of new solar cell technology, new energy storage systems are also meeting the moment for a more reliable, and affordable, power generation profile in the US.

If you have any thoughts about that, drop a note in the comment thread. Better yet, find your representatives in Congress and let them know what you think.

Photo: Quantum dots are opening up yet another chapter in the book of solar cell innovation, helping to keep the cost of solar power sliding downwards (cropped, courtesy of UbiQD).