Photovoltaic: How Does it work
The direct conversion of sun light into electric energy by means of solar cells is called Photovoltaic. The conversion is based on the photoelectric effect, which describes the release of positive and negative loads within a solid body by means of light beams.
Most of the worldwide produced solar cells consist of the semiconductor silicon. Two silicon layers with different loads are the essential element of a solar cell. A boundary layer is established between the two layers. Released loads can pass through the boundary layer by means of sun beams. The created electric power can be used via pins, connected on the front and back side of the solar cell. A full contact surface is usually on the backside of the solar cell. A thin grid is usually on the front to lead light direct on the surface.
In general solar cells are 10 x 10 cm, in recent times the dimension of 15 x 15 cm are more and more attractive. On the cell surface is covered with a transparent anti-reflection layer to protect the solar cell and to reduce reflection.
The voltage provided by the solar cell depends on the semiconductor, e.g., silicon produces 0.5 V. While the voltage is only slightly dependent on sun irradiation, the current increases with higher luminosity. The performance of a solar cell is temperature-dependent. Higher cell temperatures lead to lower performance and hence to a lower coefficient of efficiency. The coefficient of efficiency indicates how much of the sun light can be converted into usable electrical energy.
Cell types
| Material | Coefficient in % (Laboratory) |
Coefficient in % (Production) |
|---|---|---|
| Monocrystalline silicon | approx. 24 | 14 ... 17 |
| Polycrystalline silicon | approx. 18 | 13 ... 15 |
| Amorphous silicon | approx. 13 | 5 ... 7 |
Source: Wikipedia