Silicon is electrically neutral and on that the extra protons in the phosphorus balance out electrons, the missing protons in the boron balance out the missing electrons holes. That neutrality is disrupted when the holes and electrons mix at the junction between N-type and P-type silicon. Its not like that free electrons fill all the free holes if that happened then whole arrangement wouldn’t be very useful. However they mix when they form a barrier at the junction, because of that it becomes harder for electrons on the N side to cross to the P side. Occurring in due course, equilibrium is reached, and an electric field separating the two sides.
This electric field works as a diode, which allow electrons to flow from the P side to the N side, but not to other way around. Its function is just like a hill that electrons can easily go down the hill (to the N side), but cant climbs it (to the P side).
Now we got an electric field working as diode in that electrons can only move in one direction.
When light in form of photons hit the solar cell, its energy frees electron hole pairs.
Every photon with enough energy normally will free one electron, and result in free hole as well. If that happen so near to the electric field, or free electron and free hole happen wander into its range of influence, then the field will send the electron to the N side and the hole to the P side. This will cause further disruption in electrical neutrality, and if we provide an external current path then electrons will flow through the path to their original side (the P side) to unite with holes that the electric field sent there, and that will work along the way. Flow of electrons provides current and cell’s electric field causes a voltage. With combination of both we gets power and that’s generated by two.
There are few more steps before we use our solar cell. Silicon is a very shining material means it’s so much reflective. Because of that photons are reflected and can’t be used by the cell. For that antireflective coating is applied at the top of the cell to reduce reflection losses to less than 5%.
On final step glass cover plate is placed on it to protect the cell from the elements. By connecting several cells (usually 36) in series and parallel PV modules are made to achieve useful levels of voltage and current, and putting then in an strongly built frame complete with a glass cover and positive and negative terminals on the back.
A PV cell absorb sunlight at most 25% but usually that’s 15% or less.
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