Published on January 28th, 2012 | by Nicholas Brown2
Startup Invents Peel-Off Solar Cell
January 28th, 2012 by Nicholas Brown
Astrowatt has developed a new manufacturing technique for solar cells that would enable them to attain the comparably high efficiency of traditional silicon wafer solar panels, but while using the silicon raw material much more efficiently.
Thin-Film Solar Cells
You’ve probably heard of thin-film solar cells by now. They are, literally, semiconductor ink that is printed using an inkjet printer on a substrate (surface) such as glass or plastic, and possibly encased in a protective solar panel.
The ink used is usually an electricity-generating semiconductor material such as CIGS and cadmium telluride. This type of solar cell can be printed onto flexible surfaces, while traditional silicon wafer solar cells are brittle and, thus, require a rigid and strong surface to prevent breakage.
But that’s not what Astrowatt’s innovation is about….
Astrowatt’s Efficient Solar-Cell Manufacturing
The Astrowatt manufacturing process is not inkjet-related, because their panels are not thin-film, even though it may sound like they are. Traditional (non-thin-film) solar-cell manufacturing techniques involve sawing fragile wafers of silicon into smaller squares to make solar cells, and, during this process, nearly half of the silicon wafer turns into sawdust and is wasted. Of course, the cost of the wasted material is included in the price of the solar panels, and this is an important issue for the cost of solar panels and solar power (the cost of solar power is mostly the capital cost of the solar setup, and the cost of the solar panels is a major part of such a setup).
The traditional wafer sawing process yields three solar cells from every 1 millimeter-thick wafer of silicon (solar cells are extremely thin), but the new method extracts five or more cells per wafer and, hence, eliminates most of the silicon wastage.
The Manufacturing Process
Astrowatt’s manufacturing process is commenced by sawing blocks of silicon into wafers that are each 1-millimeter thick, as mentioned above. Then, the top of each wafer is modified so that it can act as the back of a solar cell, and this process is completed by depositing a layer of metal onto the wafer.
Next, the wafer is heated. Heating causes stress in the material because the metal and silicon expand at different rates. In case you didn’t know, heating causes materials, in general, to expand (this is a decrease in density and increase in volume/size). A wedge is then applied to the edge of the stressed silicon, which causes a crack that propagates to the other edge. This allows the manufacturers to peel away the metal film mentioned above along with the a 25-micrometer-thick layer of silicon, and they continue to peel off successive 25-micrometer-thick layers until they are left with a thick silicon wafer that is still of adequate quality, unlike sawdust, that they can back into the furnace and recycle into another block.
Finally, the thin 25-micrometer-think layers peeled off are processed to produce complete solar cells.
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