Indian American helps design cheaper, better solar cellsSeptember 15th, 2008 - 10:58 am ICT by IANS
Washington, Sep 15 (IANS) An Indian-American researcher is working with a team of Utah University engineers to design cheaper, lighter and better solar cells. Dinesh Rakhwal, doctoral student in mechanical engineering, said: “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.”
Germanium serves as the bottom layer of the most efficient existing type of solar cell, but is used primarily on NASA, military and commercial satellites because of the high expense - raw germanium costs about $1,360 per kg.
The improved ‘wafer-slicing’ method will help make high-efficiency solar cells for use even on roof tops, where cost now is a factor, said Eberhard Bamberg, assistant professor of mechanical engineering.
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.
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 slices 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.
The findings of Bamberg and Rakwal will appear in the October edition of the Journal of Materials Processing Technology.
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