Work by a research team at Penn State and Rice University could lead to the development of flexible solar cells. The engineers' technique centers on control of the nanostructure and morphology to create organic solar cells made of block polymers. Image Credit: Penn State/Curtis Chan.
Work by a team of chemical engineers at Penn State and Rice University may lead to a new class of inexpensive organic solar cells. "Imagine if you could make solar cells as easily as you can print posters or newspapers -- you could make sheets of this," said Enrique Gomez, assistant professor of chemical engineering. Most solar cells today are inorganic and made of crystalline silicon. The problem with these, Gomez explained, is that inorganic solar cells tend to be expensive, rigid and relatively inefficient when it comes to converting sunlight into electricity. But organic solar cells offer an intriguing alternative that's flexible and potentially less expensive. The problem is that the bulk of organic solar cells employ fullerene acceptors -- a carbon-based molecule that's extremely difficult to scale up for mass production. Gomez's approach skips the fullerene acceptor altogether and seeks to combine molecules in a solution. He says, "It's like trying to mix oil and water." The issue is that weak intermolecular interactions and disorder at junctions of different organic materials limited the performance and stability of previous organic solar cells. But by controlling the nanostructure and morphology, the team essentially redesigned the molecules to link together in a better way. The engineers were able to control the donor-acceptor heterojunctions through microphase-separated conjugated block copolymers. The result is an organic solar cell made of block copolymers that's three percent efficient. Though the team's prototype is not as efficient as some solar cells that are commercially available, Gomez explained the work shows flexible organic solar cells are indeed possible.