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Experts Show Us Little Known Ways to Make More Helpful Photovoltaic Panels
Shannon Combs
2010-06-08
Although silicon is actually the industry common semiconductor in the majority of electrical products, including the photovoltaic cells that sun panels use to convert sunlight into energy, it is not really the most effective component readily available.
For example, the semiconductor gallium arsenide and related compound semiconductors offer nearly two times the performance as silicon in photovoltaic units, but they are rarely employed in utility-scale applications mainly because of their high manufacturing cost.
University. of Illinois teachers J. Rogers and X. Li investigated lower-cost techniques to manufacture thin films of gallium arsenide that also granted versatility in the sorts of units they might be integrated into.
If you could reduce substantially the expense of gallium arsenide and other compound semiconductors, then you can expand their variety of applications.
Usually, gallium arsenide is placed in a single thin layer on a little wafer. Either the preferred unit is made specifically on the wafer, or the semiconductor-coated wafer is broken up into chips of the ideal size. The Illinois team considered to put in numerous levels of the material on a individual wafer, creating a layered, "pancake" stack of gallium arsenide thin films.
If you increase ten levels in 1 growth, you simply have to load the wafer a single time. If you do this in 10 growths, loading and unloading with temp ramp-up as well as ramp-down get a lot of time. If you consider exactly what is required for every growth - the machine, the procedure, the period, the people - the overhead saving this method provides is a significant price reduction.
Following, the scientists separately peel off the layers and move them. To accomplish this, the stacks swap layers of aluminum arsenide with the gallium arsenide. Bathing the stacks in a formula of acid and an oxidizing agent dissolves the layers of aluminum arsenide, freeing the individual small sheets of gallium arsenide. A soft stamp-like system selects up the layers, just one at a time from the top down, for exchange to another substrate - glass, plastic or silicon, based on the application. Next the wafer can be reused for one more growth.
By doing this it’s possible to generate significantly more material much more rapidly and more price efficiently. This process could make mass quantities of material, as opposed to simply the thin single-layer manner in which it is generally grown.
Freeing the material from the wafer also opens the probability of flexible, thin-film electronics produced with gallium arsenide or other high-speed semiconductors. To make products which can conform but still retain higher efficiency, that is considerable.
In a paper written and published online May 20 in the journal Nature, the group explains its methods and shows three kinds of products using gallium arsenide chips produced in multilayer stacks: light units, high-speed transistors and solar cells. The authors additionally offer a comprehensive cost comparison.
An additional benefit of the multilayer method is the release from area constraints, particularly important for photovoltaic cells. As the layers are removed from the stack, they can be laid out side-by-side on one more substrate in order to produce a significantly greater surface area, whereas the standard single-layer procedure restricts area to the dimension of the wafer.
For photovoltaics, you want large area coverage to get as much sunlight as achievable. In an extreme case we might grow sufficient layers to have 10 times the area of the traditional.
Up coming, the team programs to investigate more prospective product applications and additional semiconductor resources which might adapt to multilayer growth.
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