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Here is a typical poly-Si slice and a solar cell made from a similar slice.
The dimensions are 10 cm x 10 cm. |
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While the poly-Si slice is relatively fine grained (probably form about
1993), the solar cell (from about 1998) shows coarser grain structures - demonstrating the progress made in casting technology
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How good are polycrystalline solar cells? Not too bad, actually, but not as good as solar
cells from very good single crystals. |
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Below are four color coded maps showing essential parameters lod solar cells locally
. These maps are not easy to obtains; they result from a new technique, developed by a university of Kiel research group,
called "CELLO" (short for "Cell Local").
More details via the link. The parameters measured are: |
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"Current", meaning the maximum (short-circuit
current) that can be drawn from a pixel. |
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"Voltage", meaning the voltage a pixel would
produce if it would be an isolated cell by itself. |
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"Series resistance
", essentially meaning the ohmic resistance that would be found in an equivalent circuit for one pixel |
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"Process defects", a lumped parameter that displays
serious local problems like, e.g., locally leaking pn-junctions. |
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© H. Föll (Semiconductors - Script)