Boosting the efficiency of plastic solar cells

Researches at Wake Forest University have been working towards increasing the efficiency of plastic solar cells. Currently, plastic solar cells top out at about 4.8% efficiency, which is nowhere near the efficiency of silicon based photovoltaics, which range from 14-20% for most silicon cells, with some concentrator cells hitting 40%. But the big advantage of plastic cells is that they offer flexibility and light weight, and ultimately could be incorporated into a much wider range of products at a cheaper cost.

David Carroll and his team of researchers at Wake Forest’s Center for Nanotechnology and Molecular Materials have begun to incorporate nanoscale polymer trees to increase efficiency. “They look kind of like trees going from one contact to the next, grasping this polymer, grabbing the charge and shunting it out of this device,” Carroll says. “The material up at the top at the limbs moves charge differently than the material down at the trunk.”

By building the nanoscale “trees” into the cell, they’ve been able to create cells that are 6% efficient, which would be a world record once its independently verified. Also, the polymer that they’re using to build the cell, which is known as P3HT, allows for the plastic cells to be a little thicker than before, which allows for more light to be captured, and higher durability. One of the drawbacks of current plastic cells is that they tend to lose efficiency over time, but the Wake Forest cells have shown higher durability.

Carroll and his team are also exploring taking the efficiency much much higher. They have shown that they can incorporate fiber optics into their cells. Fiber optics can guide light into the cell and trap it there until its absorbed. Because the fibers guide the light in, you can set them up to catch a very wide range of angled light, such as on a rooftop. Doing that will lead to a huge jump in efficiencies.

Lawrence Kazmerski, director of the Department of Energy’s National Center for Photovoltaics in Colorado says that if such superefficient cells could be made cheaply and easily it would transform the world of energy. “If they can have a breakthrough it could kill everything else,” Kazmerski says. “It could be the killer technology.”

Check out the Scientific American article here.

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