NREL solar scientists epitomize teamwork
A Colorado carpenter's son, an African American from Indiana, a post-doctoral researcher from Senegal, and a young woman from China are working together to solve one of the most important problems in solar-cell efficiency.
When they're not laughing with each other, or meeting with a group of 20 to share strategies, the foursome of scientists at the U.S. Department of Energy's National Renewable Energy Laboratory is trying to control semiconductors' band gaps to make solar cells less expensive and more efficient. And along the way they're attempting to solve fundamental scientific questions about the nature of new opto-electronic materials.
They're the new face of science - collaborative and diverse, living proof that the age of the solo scientist shouting "Eureka!" has been replaced in the 21st century by multi-disciplinary teams with complementary skills.
David Ginley, the son of a carpenter, who grew up in suburban Denver near NREL's Golden, Colo., campus, leads the team.
He is joined by Joe Berry, a senior scientist, who hails from Indiana; Yi Ke, a graduate student from China who is doing her doctoral dissertation work at Colorado School of Mines and is experimenting with materials in NREL's Pulse Laser Deposition (PLD) lab; and Paul Ndione, the post-doc who oversees the PLD.
NREL team searching for better top layer
Despite tremendous gains made in processing and developing solar cells, most arrays on individual rooftops or in grid-connected solar fields still operate well below the nearly 30 percent theoretical conversion efficiency possible for a single absorber device. There are many opportunities to significantly improve the existing efficiency, sometimes while reducing the cost.
That means any breakthrough to add a percentage point or two to that efficiency is huge, and a big step toward making clean solar energy competitive with fossil fuels.
Most solar photovoltaics are composed of an active semiconductor absorber that absorbs the light, a junction to turn photons into charge carriers, and contacts to efficiently remove the carriers without blocking light. To accomplish this, the top layer, the one facing the sun, needs to be both transparent and able to conduct electrons with very little loss.
It's that top layer that is the subject of the NREL team's work. Lately, solar manufacturers have been using indium tin oxide for that transparent conducting oxide layer. However, indium is difficult to extract and is very expensive. So, scientists are searching for alternatives.
Zinc oxide is a promising candidate because it is both highly transparent and conductive, as well as being much more abundant, Ke said. It is also about 1 percent of the cost of indium tin oxide.
Ginley and his team want to add magnesium to the zinc oxide to improve its transparency and then to dope the ZnMgO with another material to boost its conductivity, all in the name of developing more efficient and more cost-effective solar cells.
Read more at www.nrel.gov.