Explain the working principle of a solar cell. Mention its applications.

Explanation

Priniciple :
(i) A solar cell, also known as photovoltaic cell, converts light energy directly into electricity or electric potential difference by photovoltaic effect.
(ii) it is basically a p-n junction which generates emf when solar radiation falls on the p-n junction. (iii) A solar cell is of two types: p-type and n-type.
Construction :
(i) Both types use a combination of p-type and n-type Silicon which together forms the p-n junction of the solar cell.
(ii) The difference is that p-type solar cells use p-type Silicon as the base with an ultra thin layer of n-type Silicon while n-type solar cell uses the opposite combination.
(iii) The other side of the p-Silicon is coated with metal which forms the back electrical contact. On top of the n-type Silicon, metal grid is deposited which acts as the front electrical contact.
(v) The top of the solar cell is coated with antireflection coating and toughened glass.
Working :
(i) In a solar cell, electron-hole pairs are generated due to the absorption of light near the junction.
(ii) Then the charge carriers are separated due to the electric field of the depletion region.
(iii) Electrons move towards n-type Silicon and holes move towards p-type Silicon layer.
(iv) The ectrons reaching the n-side are collected by the front contact and holes reaching p-side are collected by the back electrical contact.
(v) Thus a potential difference is developed . across solar cell. (vi) When an external load is connected to the solar cell, photocurrent flows through the load.
(vii) Many solar cells are connected together either in series or in parallel combination to form solar panel or module. Many solar panels are connected with each other to form solar arrays.
(viii) For high power applications, solar panels and solar arrays are used.
Applications :
(i) Solar cells are widely used in calculators, watches, toys, portable power supplies, etc.
(ii) Solar cells are used in satellites and space applications.
(iii) Solar panels are used to generate electricity.