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Faster Cheaper Method to Fabricate Solar Cells Using HVPE

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Background: Semiconductors including solar cells can be made of compounds from different groups of the periodic table. In particular Group III-V photovoltaics (e.g. based on gallium arsenide) are known for world-class efficiency as well as high production costs. Such devices require sharp interface transitions between multiple different layers. This level of control and quality has meant that almost all III-V solar cells are being manufactured by a method called MOVPE (metal-organic vapor phase epitaxy). MOVPE-based processes are slow very expensive and require costly precursor materials. An alternative method called HVPE (hydride vapor phase epitaxy) uses cheaper source materials and can achieve faster growth rates. However several challenges exist. Specifically HVPE reactors and growth conditions make it difficult to control interface sharpness and doping. Strategies for overcoming such problems include growing individual layers in separate reactors. Although simple this strategy can introduce impurities that degrade performance. Technology Description: UW–Madison researchers and others have developed an improved HVPE system to streamline production of Group III-V solar cells and other multilayer semiconductor devices. The HVPE reactor is adapted to allow steady state chemistry to be established in two or more reaction chambers. Reaction conditions like temperature are individually controlled in the different chambers. To grow multiple layers the device is moved between reaction chambers without resetting temperature or chemistry. The new system uses cheaper source materials (e.g. pure metals) and achieves growth rates of up to five micrometers per minute. Applications: Making optoelectronic devices like solar cells lasers and light-emitting diodes (LEDs)Opportunity for collaboration:The Wisconsin Alumni Research Foundation (WARF) is seeking commercial partners interested in developing a high throughput semiconductor deposition system that can be used to make photovoltaic devices.

Benefits:

1) Growth rates are up to six times greater than other deposition techniques 2) High throughput 3) Allows for inline production rather than requiring batch growth 4) Forms sharp interfaces5) Can be used to grow thick or clean thin films

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