ILLINOIS RESEARCHERS CREATE BETTER SOLAR PANELS
Despite the fact that silicon is the market’s most commonly used semiconductor in the majority of electrical devices (which includes PV cells that solar panels employ to transform sunlight into power) it is hardly the most cost-efficient material on the market. For example, the semiconductor gallium arsenide plus connected compound semiconductors offer nearly twice the effectiveness of silicon in photovoltaic products, yet they are rarely utilized in utility-scale applications mainly because of their high production price!
At the University of Illinois (http://illinois.edu/) J. Rogers and X. Li researched much lower-cost methods to create thin films of gallium arsenide which widened the possible usefulness of these types of units.
Usually, gallium arsenide is transferred in a individual thin layers on a little wafer. Either the ideal device is made specifically on the wafer, or the semiconductor-coated wafer is cut up into chips of the preferred size. The Illinois team decided to deposit several layers of the material on a single wafer, creating a layered or “pancake” stack of gallium arsenide thin films. If you increase 10 levels in one growth, you only have to load the wafer 1 time. If you do this in ten growths, loading and unloading with temperature ramp-up and ramp-down takes a lot of time. If you also take into account exactly what is necessary for every growth – the machine, the research, and the workers’ time – the overhead saving that this approach offers equals a sizable price reduction. After that the researchers individually peeled off the levels and move them. To complete this, the stacks swap layers of aluminum arsenide with the gallium arsenide. Bathing the stacks in a solution of acid and an oxidizing agent dissolves the layers of aluminum arsenide, freeing the single thin sheets of gallium arsenide. A soft stamp-like system picks up the layers, just one at a time from the top down, and for move to another substrate – glass, plastic-type or silicon, depending on the application. After that the wafer may be used again for an additional growth.
By doing this it’s possible to make significantly more material faster and with greater price efficiently. This process could create bulk amounts of material, as opposed to merely the thin single-layer manner in which it is typically grown. Freeing the material from the wafer also starts the possibility of flexible, thin-film electronics made with gallium arsenide or different high-speed semiconductors. It is significant to make conforming products with advanced performance at lower costs.
In a paper published online 5/20/2010 in the newspaper Nature (http://www.nature.com/), the team explains its techniques and demonstrates 3 types of units making use of gallium arsenide chips manufactured in such multilayer stacks: light units, high-speed transistors and photovoltaic cells. The creators additionally supply a comprehensive cost comparison. An additional advantage of the multilayer method is the release from area constraints, especially important for solar cells. As the layers are taken away from the stack, they can be laid out side-by-side on another substrate in order to generate a significantly bigger surface area, whereas the typical single-layer procedure limits area to the dimension of the wafer. For solar panels, you want big area coverage to catch as much sunshine as achievable. In an extreme case we might increase sufficient layers to have 10 times the area of the standard.
Next, the team plans to explore many more potential item applications and other semiconductor resources which might adapt to multilayer growth.
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