Kevin
The conversion of sunlight to direct current electricity occurs by a process called photovoltaics. The cell used in the conversion consists of semiconductor material with controlled impurities. One layer, called the n-type or donor layer, contains atoms with one more valence electron than the semiconductor; the other, called the p-type or acceptor layer, has atoms with one less valence electron. In the absence of light, the extra electrons in the n-type layer move to the p-type layer by diffusion. When light hits the n-type layer, the photoelectric effect creates an electric field across the junction; the field causes electrons to move from the p to the n layer, and a current flows in the cell.
Most effective in the developing regions of the lower latitudes, photovoltaics has widespread applications. It can be used for water pumping systems that supply the much needed liquid to villages and farms. Lamps can be made with small cells. Also, photovoltaic systems can provide enough electricity for small-scale usage. The high reliability of the systems allows for the importance of photovoltaics in the refrigeration of vaccines and other temperatures-sensitive goods.