By Sunil Bhardwaj

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Solar cells were discovered in 1954 by Chapin, Faller and Pearson.

Principle: Sunlight is converted into-electrical energy.

Construction: It is consist of iron plate which is used as a base for cell. Over this plate, the thin layers of large no. of n and p type of semiconductors, which are very small thickness just like wafer. The function of large no. of layers is to obtain large quantity of electricity. When the solar radiations are incident at the junction i.e. semiconductor. The electron in the case of n-type or positive holes in case of p-type of semiconductor. The energy of the electrons increases become unstable and move towards the Ag plate which is called collector electrode and these electrons move from Ag to Fe. When these electrons are received by Fe, circuit is completed and current is. produced which flow from Fe to Ag. This current is obtained in terms of deflection of galvanometer. The magnitude of the current is directly proportional to the intensity of sun radiations incident at the junction. One microwatt sun radiations are capable to produce 0.08 u. amp. current.

Advantages:

(1) The material used are having low cost.

(2) No electrolyte is required.

(3) Natural energy (solar) is converted into electrical energy.

Disadvantages:

(1) Efficiency is low.

(2) Long term instability, it is due to the reaction of semi-conductors with O2 and water vapour,

Uses:

(1) In space vehicles.

(2) In instrumentations to convert transmitted light from sample to electrical energy.