The Photovoltaic Effect

The generation of power in solar cells is made possible through the photovoltaic effect, where the energy from photons of incident sunlight is used to produce a potential difference across the solar cell, in turn driving a current through an external load. The photovoltaic effect is similar to the photoelectric effect in the sense that photons of particular energies may excite electrons from bound to free states. However, where electron emission occurs in the photoelectric effect, the photovoltaic effect includes a mechanism to direct the newly freed electrons within the material of solar cells, in order to produce an electric current.

To understand this mechanism, which is the distinguishing feature between the photoelectric and photovoltaic effects, we must first identify the electrical properties of semiconductors which make them perfectly suited for the fabrication of solar cells. In particular, we must look at the concepts of atomic structure, the exclusion principle, ‘band gap’ energies and silicon doping.