Photovoltaics (PV) is the name of a method of converting solar energy into direct current electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon commonly studied in physics, photochemistry and electrochemistry.
The process is both physical and chemical in nature, as the first step involves the photoelectric effect from which a second electrochemical process takes place involving crystallized atoms being ionized in a series, generating an electric current.
The direct conversion of sunlight to electricity occurs without any moving parts or environmental emissions during operation. It is well proven, as photovoltaic systems have now been used for fifty years in specialized applications, and grid-connected PV systems have been in use for over twenty years. They were first mass-produced in the year 2000, when German environmentalists including Eurosolar succeeded in obtaining government support for the 100,000 roofs program.
When an incident light of enough energy strikes a metal surface it provides enough energy to an electron, which then escapes the boundary of the metal and thus is emitted out. This phenomenon is called photoelectric effect. It is important that the energy of the incident light should match the energy of the electron. In semiconductors, there is a relatively larger energy difference between the conduction and the valance band. The visible region of the electromagnetic spectrum provides sufficient energy for an electron to get excited and jump from the valance band to the