Engineers and materials scientists at University of California in Los Angeles improved the design of solar cells built in a thin semi-transparent film that nearly doubles their ability to generate power. A team from the lab of engineering professor Yang Yang described its findings online in Friday’s issue of the journal Energy and Environmental Science (free registration required).
Yang’s lab developed an earlier form of the solar cell with a near-infrared light-sensitive polymer. The cell produces energy by absorbing mainly infrared light, not visible light. The cell developed in that first round was 70 percent transparent, and achieved a power-generating efficiency of 4 percent.
The new version of the solar cell from Yang’s lab is a tandem device with two thin light-activated polymer solar cells that absorb more light than the single-cell version. The new device also combines transparent and semi-transparent polymer cells, and a layer between the two cells to reduce energy loss.
Tests conducted by Yang’s team show the tandem device achieves a conversion rate — percentage of energy from the sun converted to electric power — of 7.3 percent, compared to 4 percent in the earlier version. The new device captures up to 80 percent of infrared light, with a small amount of light from the visible spectrum, compared to about 40 percent of infrared light absorbed in the earlier single-cell version.
The process to generate the solar cells, say the researchers, uses low temperatures, which makes production of the cells more feasible. The cells can also be produced to appear in various shades of light gray, green, or brown to blend in with building exteriors, windows, or electronic surfaces.
“We anticipate this device,” says Yang, “will offer new directions for solar cells, including the creation of solar windows on homes and office buildings.”