Solar cell (Photovoltaic cell) |
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A solar cell is a huge p-n junction diode with a thin (0.5 micron) n-type layer on top and p-type below. Recombination of holes and electrons across the junction establishes a small voltage (barrier potential of 0.65 V in silicon). Electrons, excited to the conduction band by sunlight in the upper n-type layer, are forced across the junction by the barrier potential. Electrons then flow around the circuit to finally recombine in the p-type layer. High voltages are achieved with many cells in series. The conversion of sunlight (flux of 1020 W/m2 at ground level) to electrical power is 12-15% efficient at best. Large areas are required to generate useful power. The cells work best at low temperatures and have wide application.
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Solar cell technology is clever but capital intensive. |
