The first several times, NREL researchers peering through microscopes at the copper saw not ribbons, but beads, representing discontinuity of the metal, a serious imperfection that causes poor performance of the cell. It was back-and-forth forensics work, examinations of tiny sections of large silicon wafers 156 millimeters on a side, larger than a CD case.
"We'd e-mail TetraSun the results; they'd see all those imperfections and try a different recipe or approach. We'd test it again, and e-mail the results again," Al-Jassim said. "Eventually, we got what we wanted to see.
"It was a very laborious process because we had to sample many parts from various areas of the cell," Al-Jassim added, noting that the copper grids are about one-twenty-fifth the width of a human hair. "But that's where NREL shines when we are measuring at the nanoscale."
NREL also helped TetraSun increase cell yields while keeping a high efficiency. "We told them why the good cells were good, and why the bad ones were bad," Al-Jassim said. "It really is scientific detective work. It's not easy, but NREL is very well equipped to do this."
In addition, NREL performed tests to validate the TetraSun cell's reliability:
Maximizing Savings More Essential Than Ever
The importance of squeezing every last penny of savings from a solar cell has grown rapidly the past five years, as manufacturers try to ramp up to gigawatt scale and as the Chinese industry has lowered costs and margins.
Lately, companies almost always have had to increase cos
|Contact: David Glickson|
DOE/National Renewable Energy Laboratory