Solar cells can be classified into first, second and third generation cells. The first generation cells—also called conventional, traditional or wafer crystalline silicon, the commercially predominant PV technology, that includes materials such as and monocrystalline silicon. Second generation cells are thin film solar cells, that include amorphous silicon, CdTe and CIGS cells and are commercially significant in utility-scale photovoltaic power stations,building integrated photostatic or, in small stand-alone power system. The third generation of solar cells includes a number of thin-film technologies often described as emerging photovoltaics—most of them have not yet been commercially applied and are still in the research or development phase. Many use organic materials, often organometallic compounds as well as inorganic substances.