“You can just imagine the area in New York, Chicago, or Hong Kong: There are huge buildings with big windows. That area is just wasted.” That’s Alan Heeger, a Nobel chemistry laureate, getting enthusiastic about new uses for thin, flexible, semi-transparent solar cells he’s developing using a “liquid ink” material. The transparent solar cells can generate power for air conditioning and even serve to screen from the sun’s rays. “It’s like wearing sunglasses,” Heeger explained; the cells act as a solar insulator, reducing the amount of heat radiating in the building.

Dr. Alan Heeger holds a flexible plastic solar cell made with a roll-to-roll printing tool.
Courtesy Photo

The liquid solar cell material can be printed from a roll-to-roll printing press, much as newspaper is printed; comes in different colors; is durable; and being bendable, can be placed along curved surfaces like the outer walls or windows of high rises. Its lightweight and rugged aspect is very attractive to urban planning specialists because it allows endless possibilities on where and how the solar cells can be applied to surfaces.

Another interesting use of these solar cells is on greenhouses. They are light enough to be placed on the roof and sides of the structure, and their transparency lets the sun shine through toward the plants. Heeger suggested that tinting the color of the cells may increase the productivity of the plants below.

The possibilities of solar installation are endless with the new variables of flexibility and lightweight technology. This alone may allow people who’ve never considered using solar cells to find ways to apply them to their structures.

Solar cells need a reasonably high efficiency to make the cells productive. Heeger explained that he and his colleagues originally sparked the idea in 1995 in the laboratory and created cells that were about one percent efficient. He explained, “Many people around the world see the potential value in this research. Now, the efficiencies [of our solar cells] are steadily rising up to about 12 percent, and we foresee 15-20 percent in the reasonable future. By utilizing tandem cells, we could probably obtain even higher efficiencies, which is fantastic.”

Heeger has collaborated with many people in various departments to conduct his research, explaining that the strong boundaries between physics, chemistry, and material sciences are a thing of the past. Although the liquid solar cells have not yet reached the desired efficiency, Heeger is optimistic that they’ll be a giant stepping stone toward new innovations in the world of solar cell research.

“We will get there,” Heeger said. “[Science] is exciting, and there’s nothing more exciting than discovery.”

Karen Housel is a fourth-year undergrad studying Environmental Science at UC Santa Barbara. She is interested in marine biology, sustainability, ecotoxicology, and restoration, and hopes ultimately to improve air and water quality in urban and rural areas.


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