08_Making_Solar_Cells

08_Making_Solar_Cells - Making Solar Cells ELEG620: Solar...

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ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 S. Bremner Making Solar Cells
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ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 S. Bremner Making Solar Cells We will look at some the differences that stand between solar cells that are research and commercial in particular the following features - materials that are used (semiconductor, quality of semiconductor) - processing used (complexity, number of steps) - designs
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ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 S. Bremner Research • Generally have more freedom in design since cost effectiveness is not main concern • However, the idea is to develop a high efficiency design and then try to implement as a commercially viable process sometimes • Because of the lack of restrictions in materials and processes the efficiencies reported for research devices are generally significantly higher than for commercial solar cells • Sizes tend to be small also, not always striaght forward to scale up
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ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 S. Bremner Commercial • Want material that is generally inexpensive though can be mitigated by high efficiency • Processing has to be relatively straightforward (in general people with PhDs will not be doing this) • Want as few processing steps as possible (more steps = more expensive and more chance for something to go wrong) • Processes must be robust i.e. it works all the time if you have set up correctly • Must be easily scaleable • Ideally the disruption to current production is minimal – we don’t want to have to build a new factory
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ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 S. Bremner • Materials for solar cells are usually one or more of the following: • Group IV (Si and Ge) • III-V (GaAs, InP and variants) • II-VI – CuInSe 2 (CIS) – CuInGaSe 2 (CIGS) –C dT
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ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 S. Bremner Silicon • First need to decide on type of silicon to be used – Float Zone: gives best diffusion lengths etc. . As impurities are reduced particularly oxygen. Popular for high efficiency devices in research – Czochralski: good quality material with low impurities. Mainstay for single crystalline devices both research and commercial. Not as expensive as Float Zone – Multi(Poly)crystalline: not as good as CZ or FZ, but much cheaper, efficiency will be highly variable from cell due to grain boundaries etc. . Very popular commercially. – Amorphous: very cheap, not crystalline so low efficiencies. Easy to deposit with relatively high quality. Some research done but mostly used in ‘disposable’ consumer applications
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ELEG620: Solar Electric Systems University of Delaware, ECE Spring 2009 S. Bremner Refining Silicon Start with silica or sand (want low impurity concentrations) Fire with carbon to get metallurgical grade silicon
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This note was uploaded on 12/14/2011 for the course ELEG 620 taught by Professor Honsberg,c during the Fall '08 term at University of Delaware.

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08_Making_Solar_Cells - Making Solar Cells ELEG620: Solar...

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