The solar device is comprised of two thin polymer solar cells that can be made in shades from light green and gray to brown, which allows them to blend in with the surface of buildings or other structures. The solar cells absorb more light than single-layer solar devices, use light from a wider portion of the solar spectrum, and incorporate a layer of novel materials between the two cells to reduce energy loss.
Called a tandem-structure transparent organic photovoltaic (TOPV) device, the technology originally had an efficiency of only 4 percent, but the UCLA team has now gotten that number up to 7.3 percent.
"Using two solar cells with the new interfacial materials in between produces close to two times the energy we originally observed," said Yang Yang, an engineering professor who is also director of the Nano Renewable Energy Center at the California NanoSystems Institute at UCLA. "We anticipate this device will offer new directions for solar cells, including the creation of solar windows on homes and office buildings."