Silicon-based solar cells, by far the most prevalent type of solar cell available today, might provide clean, green energy but they are bulky, rigid and expensive to produce. Organic (carbon-based) semiconductors are seen as a promising way to enable flexible, lightweight solar cells that would also be much cheaper to produce as they could be “printed” in large plastic sheets at room temperature. New research from physicists at Rutgers University has strengthened hopes that solar cells based on organic semiconductors may one day overtake silicon solar cells in cost and performance, thereby increasing the practicality of solar-generated electricity as an alternative energy source to fossil fuels.
Vitaly Podzorov, assistant professor of Physics at Rutgers, and his colleagues observed that excitons – particles that form when semiconducting materials absorb photons, or light particles – can travel a thousand times farther in an extremely pure crystal organic semiconductor called rubene than the typically observed 20 nanometers previously observed in other organic semiconductors.
“This is the first time we observed excitons migrating a few microns,” said Podzorov, noting that they measured diffusion lengths from two to eight microns, or millionths of a meter. This is similar to exciton diffusion in inorganic solar cell materials such as silicon and gallium arsenide.
Once the exciton diffusion distance becomes comparable to the light absorption length, you can collect most of the sunlight for energy conversion,” he said.
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