Solar cells are the smallest unit of a solar panel. Understanding how solar cell works easy if you know how a P-N junction diode works? Do you know that. I know most of you know that. However I will explain how solar cell works in step by step using images. You can also watch the video I embeded below.
Solar cells, also called photovoltaic cells are made up of semiconductors, materials that have a conductivity between that of an insulator and conductor. In essence, a solar cell is a junction of two dissimilar semiconducting materials, known as p-type and n-type semiconductors. Both of these can be made from crystalline silicon.
Since silicon on its own does not conduct electricity other atoms are added to silicon’s structure. This process of adding other atoms called impurities to silicon structure is called doping. Pure silicon has a diamond-like structure called silicon lattice. Its four valence bond electrons allow it to perfectly bond to four of its silicon neighbors. However, this silicon lattice is essentially an insulator as there are no free electrons for any charge movement, and is therefore not a semiconductor. This crystalline structure can be turned into a semiconductor when doped.
If we are doping pure silicon with phosphorous atoms which has five valence bond electrons, it’ll cause extra electrons which are free to move around throughout the structure. Electrons are subatomic particles with a negative electric charge, silicon doped in this way is known as n-type semiconductors.
If we are doping pure silicon with boron which has three valence bond electrons, it’ll cause lack of an election. This lack or missing of the electron is known as holes. Since the absence of a negatively charged particle, silicon doped in this way is known as a p-type semiconductor.
P-N Junction formation
When we put together p-type and n-type semiconductors p-n junction is formed. When a PN junction is formed some of the electrons from the N region which have reached the conduction band is free to diffuse across the junction and combine with holes. Filling the hole makes a negative ion and leaves behind a positive ion on the n side.
This diffusion of electrons from n region to P region a charge separation as shown, which results in an electric field. The diffusion of electrons continues until the strength of the electric field become sufficient to stop further diffusion of electrons from the N side. This creates an area around the junction called the depletion region. The depletion region is the heart of s solar cell. You can see that the n-type material is kept thin to allow the light to pass through the PN junction and reach the depletion region.
How solar cell works?
When sunlight strikes a solar cell, electrons in the silicon are ejected, which results in the formation of holes. If this happens in the depletion zone, the electric field will move the electrons to the n-type layer and holes to the p-type layer.
If we connect a load between two layers electrons will travel from the p type layer to the n type layer by crossing the depletion region, then go through the external load by creating a flow of current.
If You have any doubts about how solar cell works watch the above video once again. If the doubts still persists dont hesistate to put them below in the comment section. Happy learning. If those images helped you to learn leave a thank you note to Vysakh. He is my friend, a photoshop expert. I dont have much skill in such computer software. So I Asked him for help. He was very happy to help as usual. Thank you my friend.
OK then, see you next week with another tutorial.