Stretchy Solar Cells A Step Closer

Organic solar cells that can be painted or printed on surfaces are increasingly efficient, and now show promise for incorporation into applications like clothing that also require them to be flexible.

The Rice University lab of chemical and biomolecular engineer Rafael Verduzco has developed flexible organic photovoltaics that could be useful where constant, low-power generation is sufficient.

Verduzco and his team incorporate a network of elastic additives that make the electrically active material less brittle with little to no loss of current flow.

The research appears in the American Chemical Society journal Chemistry of Materials.

Organic solar cells rely on carbon-based materials including polymers, as opposed to hard, inorganic materials like silicon, to capture sunlight and translate it into current. Organics are also thin, lightweight, semitransparent and inexpensive. While middle-of-the-road, commercial, silicon-based solar cells perform at about 22 percent efficiency – the amount of sunlight converted into electricity – organics top out at around 15 percent.

“The field has been obsessed with the efficiency chart for a long time,” Verduzco said. “There’s been an increase in efficiency of these devices, but mechanical properties are also really important, and that part’s been neglected.

“If you stretch or bend things, you get cracks in the active layer and the device fails.”

Verduzco said one approach to fixing the brittle problem would be to find polymers or other organic semiconductors that are flexible by nature, but his lab took another tack. “Our idea was to stick with the materials that have been carefully developed over 20 years and that we know work, and find a way to improve their mechanical properties,” he said.