The words ‘photo’ and ‘voltaic’ literally translate to ‘light’ and ‘current’ respectively. Sunlight is made of little packets of energy called ‘photons’ and the photovoltaic (PV) cells of a solar module are made of semiconductor materials Figure 1.
Figure 1: From Semi-conductor to Solar Cells to Solar Module
Thus, a solar cell is an electronic device which directly converts sunlight into electricity. Light shining on the solar cell produces both a current and a voltage to generate electric power. When the photons strike a typical photovoltaic cell, the energy from the light is absorbed by the semiconductor material in the solar cell and this releases electrons in the process. It is this flow of electrons that creates electric current.
Hence, the process of converting sunlight to electricity usually involves two basic stages. The first stage requires a material in which the absorption of light raises an electron to a higher energy state. In the second stage, there is a movement of the higher energy electron from the solar cell into an external circuit (e.g. the load). The electron then dissipates its energy in the external circuit and returns to the solar cell. This creates a complete path for electron movement and by extension current flow.
A variety of materials and processes can potentially satisfy the requirements for photovoltaic energy conversion, but in practice nearly all photovoltaic energy conversion uses semiconductor materials in the form of a p-n junction. Take Solar Power Quiz