A photovoltaic cell is a photo-electric device that converts light energy into electric energy. It is a semiconductor device. Using the junction of a p-type and an n-type semiconductor. A semiconductor is a material that behaves as an insulator at ordinary temperature and pressure. Whereas at high temperatures its conductivity increases and it behaves as a metallic conductor. Edmond Becquerel was the first person to demonstrate the functioning of a photovoltaic cell in 1839.
How Does A Photovoltaic Cell Function?
A photovoltaic cell formation is when p-type and n-type semiconductors join in an alternate manner i.e. a p-type then n-type. The p-type semiconductor has holes in excess and electrons in less number i.e. in the p-type semiconductor holes are majority charge carriers and electrons are minority charge carriers while in the n-type semiconductor electrons are majority charge carriers and holes are minority charge carriers. Holes basically implies the empty spaces left behind when electrons migrate from that region.
Before learning the functioning of a photovoltaic cell, you know about p-type and n-type semiconductors.
A p-type semiconductor is nothing. But a silicon or germanium disk with a trivalent impurity (elements having three electrons in the valence shell) such as Boron, Gallium or Indium. Because a trivalent impurity has been doped, the atom of the impurity occupies a position of semiconductor material’s atom which is tetravalent in nature. Thus, the empty space left due to the migration of the tetravalent semiconductor atom is referred to as a hole.
An n-type semiconductor just like a p-type semiconductor device is composed of materials such as silicon (Si) or germanium (Ge). They have four electrons in the valence shell or are tetravalent in nature. It is doped with a pentavalent impurity such as phosphorus (P), arsenic (As), etc. On being doped, the tetravalent atoms of semiconductors are replaced by the pentavalent atoms of the impurity. Because of the presence of one extra electron in the semiconductor substance, the n-type has electrons as majority charge carriers.
Working Of A Photovoltaic Cell
- When light is incident on a photovoltaic cell, the electrons from the n-type semiconductor migrate from the n-region towards the p-type semiconductor. This is possible because the light composition is of particles. The photons carry energy in the form of small packets. These small quanta of energy excite the electrons in the n-type semiconductor.
- The electrons from the n-type semiconductor move towards the p-n junction. Due to this movement of electrons, a direct current is set up in the device whose direction is opposite to the direction of the flow of electrons.
This flow of direct current is responsible for the production of electric power.
It is to note that the flow of electrons from the n-type semiconductor is only possible when the energy of photons present in light is greater than the work function or threshold energy of the semiconductor device.
Where Do You Use Photovoltaic Cell?
It is to note that a photovoltaic cell doesn’t function only in the presence of sunlight. Rather, other synthetic sources of light can also be of use to run a photovoltaic cell. Today, the chief use of a photovoltaic cell is for the production of electricity and most of the industries use this form of electricity.
This phenomenon is in action in solar power plants, space vehicles, satellites, telescopes, etc. In these devices, you have the use of a collection of a large number of photovoltaic cells in the form of grids. These grids are responsible for concentrating solar energy. Which is later in use for energy production.