• The cost of working with it is low.
• They have not any mobile parts.
• They have high reliabilities.
• High security
Solar energy can be converted directly or indirectly to the other types of energy such as heat and electricity. Photovoltaic effect can be used for converting the solar energy to electricity utilizing the solar cells. The basic structure of a solar cell is a p – n junction formed by semiconductor devices which produce the electrical energy with absorbing the light and migration of electrons between energy bands.
The principle of solar cells is the shining of light on a p – n junction and production of electron – hole pairs that makes the drift and diffusion currents. The condition of production of electron – hole pairs is that the photon energy be bigger than the band gap energy of the material used in solar cell. The band gap energy, Eg, is the energy level difference between the conduction and valence band of the semiconductor. Hence the band gap energy, Eg, is the necessary energy for transmitting the electron from the valence band to the conduction band and the additional energy is wasted in the heat form and the electron relaxation in the lowest point of the conduction bandtakes place. Therefore, the main condition for absorbing light by a material with the energy band gap Eg is as follows: