As the world increasingly looks to alternative sources of energy, inexpensive and environmentally-friendly polymer-based solar cells have attracted significant attention, but they still do not match the power-generating ability of their more expensive silicon-based counterparts.
Now, researchers at the RIKEN Center for Emergent Matter Science and Kyoto University, both in Japan, have shown that a newly developed polymer can minimize energy loss just as well as silicon-based solar cells when converting sunlight to electricity. The researchers report this work in a recent paper inNature Communications.
Solar cells work because photons from the sun strike electrons in the solar cell and move them into a position where they can create an electric current. Photon energy loss – the amount of energy lost when converting photon energy into electrical power – has always been greater in polymer-based solar cells than in silicon-based ones.
“In polymer-based plastic solar cells, larger photon energy loss causes lower voltage. This has been one of the largest limiting factors for efficiency,” explains Hideo Ohkita from Kyoto University. “The new polymer has the potential to lead to a breakthrough on this issue.”
When they began working with the new polymer, which has oxygen atoms rather than sulfur atoms located at key positions, the researchers found that the new material was able to overcome some of the key obstacles to extracting and utilizing greater energy from sunlight.
“Since this new polymer greatly reduces photon energy loss, it has allowed us to achieve a superb power conversion efficiency of nearly 9% with a very high open-circuit voltage in plastic solar cells,” explains Itaru Osaka from the RIKEN Center for Emergent Matter Science. An efficiency of 15% is usually seen as a breakthrough level that will allow polymer-based cells to be commercialized.
“By achieving both a high short-circuit current and a high open-circuit voltage, achieving a power conversion efficiency of 15% in single-junction cells is a realistic goal,” Osaka adds. “This would have huge implications for the solar energy sector.”