Solar cells that convert sunlight to electricity at 1 or 2 percent efficiency don’t sound very exciting in a world where standard silicon cells produce at rates in the teens and even higher.

But what if the cells were so thin and light that you could stack layers of them atop each other? That might be an entirely different efficiency story, and that’s a concept MIT researchers are offering up in a new paper.

In this depiction of the solar cell, graphene is shown in blue, molybdenum atoms in red and sulfur in yellow. (image via Jeffrey Grossman & Marco Bernardi/MIT)

The MIT team said it found that an effective and outrageously thin solar cell could be made from a stack of two one-molecule-thick materials: Graphene, a one-atom-thick sheet of carbon atoms, and molybdenum disulfide.

“Stacking a few layers could allow for higher efficiency, one that competes with other well-established solar cell technologies,” Marco Bernardi, an MIT postdoc and lead author of the paper, said in a statement.

A potential advantage of such modules would be low weight, something that has been a focus of more than a few researchers and manufacturers over the years. Low weight (and, along with that, low material requirements and low cost) was always the premise behind thin-film CIGS solar. SoloPower is probably the best example – the company has tried to build a business by offering up panels said to be light and flexible enough to go on commercial rooftops that couldn’t stand the weight of standard solar modules and racks.

Scaling up and lowering costs has proved to be a monumental challenge, however, and how well the MIT concept might fare in that regard is utterly unknown.

Still, the thinness that the researchers are talking about – one nanometer, or a billionth of a meter – makes for some intriguing possibilities. “It’s 20 to 50 times thinner than the thinnest solar cell that can be made today,” MIT engineering professor Jeffrey Grossman said. “You couldn’t make a solar cell any thinner.”

That alone could make the cells cost-effective, MIT said: “The material itself is much less expensive than the highly purified silicon used for standard solar cells – and because the sheets are so thin, they require only minuscule amounts of the raw materials.”

That means, MIT said, there could be applications in things like spacecraft or aviation — the next great leap from Solar Impulse, perhaps.

by Pete Danko