SALT LAKE CITY University of Utah engineers devised a new way to slice thin wafers of the chemical element germanium for use in the most efficient type of solar power cells. They say the new method should lower the cost of such cells by reducing the waste and breakage of the brittle semiconductor.
The expensive solar cells now are used mainly on spacecraft, but with the improved wafer-slicing method, "the idea is to make germanium-based, high-efficiency solar cells for uses where cost now is a factor," particularly for solar power on Earth, says Eberhard "Ebbe" Bamberg, an assistant professor of mechanical engineering. "You want to do it on your roof."
Dinesh Rakwal, a doctoral student in mechanical engineering, adds: "We're coming up with a more efficient way of making germanium wafers for solar cells to reduce the cost and weight of these solar cells and make them defect-free."
Bamberg and Rakwal are publishing their findings in the Journal of Materials Processing Technology. Their study has been accepted, and a final version will be published online late this month or in early October, and in print in 2009.
Brass-coated, steel-wire saws now are used to slice round wafers of germanium from cylindrical single-crystal ingots. But the brittle chemical element cracks easily, requiring broken pieces to be recycled, and the width of the saws means a significant amount of germanium is lost during the cutting process. The sawing method was developed for silicon wafers, which are roughly 100 times stronger.
The new method for slicing solar cell wafers known as wire electrical discharge machining (WEDM) wastes less germanium and produces more wafers by cutting even thinner wafers with less waste and cracking. The method uses an extremely thin molybdenum wire with an electrical current running through it. It has been used previously for machining metals during tool-making.
|Contact: Lee Siegel|
University of Utah