Michael Grätzel's Solar Cells Get Stylish With Color and Translucent Materials

Michael Grätzel may be the closest thing to a living legend in the solar energy world. A professor at École Polytechnique Fédérale de Lausanne, the Swiss scientist discovered a new type of thin-film solar cell--dubbed the dye-sensitized solar cell (aka the Grätzel cell)--in 1991. Now, nearly two decades later, Grätzel's invention is taking off, with companies like Konarka, Hydrogen Solar, and Sony developing the cells for commercial use.

Grätzel's cells, which are inspired by the photosynthetic process, consist of a porous layer of titanium dioxide nanoparticles covered with a sunlight-absorbing molecular dye. The cells currently have a lower efficiency than single crystal silicon cells, and Grätzel's technology offers a number of advantages.

In a traditional silicon solar cell, the silicon acts as both a source of photoelectronics and an electric field. But in a dye-sensitized solar cell, the semiconductor is only used for transport, while the photoelectrons come from a separate photosensitive dye. As more research yields higher-efficiency Grätzel cells, companies need only switch out their dyes--the rest of the production process stays the same.

Dye-sensitized solar cells have another distinct advantage: The dyes can be manufactured in an array of colors. The Sunny Memories project, featured earlier this month at New York's Center for Architecture, exploited this feature with colorful solar designs.

Grätzel's cells can also be made translucent--a first in the solar industry. "In this respect they have a unique application, like for electric power-producing windows and glass facades," he says.

Right now, though, dye-sensitized cells are mostly found on solar phone chargers and solar energy-producing bags--a product of the cells' ability to be printed out on flexible sheets.

According to Grätzel, the cells are getting more efficient all the time. "We are making good progress with developing more efficient sensitizers that harvest light in the infrared region," he explains. "This year we hope to get to 13%, the next to 14%, once we have 15% we will be very happy because this would put us on par with other technologies in direct sunlight conditions."

Grätzel recently received the $1 million Millennium Technology Prize--an award that will help the scientist continue research on his cells. He says that most--if not all--of the money will be spent on his research, which includes a large laboratory and two small pilot lines that manufacture cells under controlled conditions.

The forward-thinking scientist believes that his technology will ultimately filter into our daily lives. "I think we're going to have a lot of these cells penetrating our living space and being integrated in buildings. A further important application of our cells will be to provide electric power for portable electronic equipment and electric cars," he says. Grätzel can't lift us out of our energy crisis, but he's certainly giving us a boost.

Ariel Schwartz can be reached on Twitter or by email.