Solar cells ( also called photovoltaics) absorb sunlight and convert it directly to electricity. Solar cells are very thin ( about 1/ 100th of an inch thick). Most are rectagular or circular wafers made of silicon ( sand), but some sonsist of a thin film that is mounted on glass or thin matal.
Irradiance is a measure of the sunpower available at surface of the earth and has an averages of 1000 wats per square meter(m2) with typical crystalline solar cells effetive around 14-17% that means we can only expect to generate about 140-170w per square meters of solar cells placed in full sun.
Most solar cells are used in a first generation devices based on crystalline silicon wafers.”Second generation” or thin film solar cells, used in semiconductor materials only and are few micrometers thick. The performance of a solar cell is measured in terms of its efficiency at turning light in to electricity.
The efficiency for first generation cells are around 15 percent that is about one-sixth of the light striking the cell and turns it into electricity. The efficiency for second generation products that are being manufactured today,range from three to 7 percent.
SINGLE CRYSTAL SILICON: