Paint-On Solar Power Is Inching Its Way Out of The Lab

University of Toronto Professor Ted Sargent Photo: University of Toronto
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A team of researchers from University of Toronto Engineering is developing a way to manufacture inexpensive solar cells in the form of a paint-on coating.

The new paintable solar cell could be applied to a variety of surfaces, including building materials. It could also be used to run portable electronic devices such as laptops.

Professor Ted Sargent, a member of the UT research team, foresees using the solar coating on objects where minimal weight is an advantage.

Laptops, smartphones and other portable devices are some examples. Another example would be auto body parts.

A solar coating could be used to help power the electrical equipment in a liquid-fueled vehicle, or it could help extend the battery range in electric vehicles.

“Since our solar cells are inherently lightweight, they can be integrated onto a wide variety of surfaces including building materials,” Sargent says.

In order to be commercially viable however, the new technology would have to achieve a fairly high level of efficiency.

The UT team has achieved a key breakthrough in that direction: the new solar cell can harvest energy from the invisible, infrared end of the light spectrum as well as from visible sunlight.

All things being equal, a solar cell that can convert the greatest range of the light spectrum to electricity will be the most efficient.

But getting that to happen is not simple. Different materials absorb different parts of the light spectrum with varying degrees of efficiency, and getting them to act in tandem is a challenge.

The UT team approached the problem using colloidal quantum dots. A quantum dot, affectionately known as a q-dot, is basically an ultra-small particle (colloidal refers to the even distribution of quantum dots in a solution).

Quantum dots can be manipulated or “tuned” to absorb different parts of the light spectrum, giving them an advantage over conventional solar cell materials like silicon.

While efficiency is a key factor in making low cost solar power a reality, it is far from the only step toward creating a low cost solar product. The use of relatively cheap materials is another key variable, and the cost of the manufacturing process must also be considered.

UT’s coating has a potential advantage because colloidal quantum dots are created by a chemical reaction, which could save on energy and equipment compared to the mechanical processes involved in conventional solar cell manufacturing. Ease of application and adaptability to a range of surfaces could also make a difference.

However, don’t expect to run out to the local hardware store any time soon to buy a can of solar paint. While the new coating shows promise, Sargent notes that further development is needed to boost its efficiency. He predicts another five years before it’s ready for commercial use.

In any case, the process involves applying three separate layers under controlled conditions, so the solar paint would most likely be applied in a factory environment, rather than being purchased for use at home.

Do-it-yourselfers can take heart, though. Michael A. Filler, a member of the Nanoscience and Nanotech faculty at Georgia Tech College of Engineering, is optimistic about the prospects for an inexpensive “solar wallpaper” based on thin film solar cell technology, which could be sold in rolls and customized at home.

Whether it’s solar paint or solar wallpaper, Filler cautions that another key factor in developing more efficient, less expensive solar cells is the wiring that conveys the electrical charge from the cell to its point of use.

“Most of the energy is lost in getting it out of the cell,” says Fuller. “The hard part is how to get the charge out.”

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