Solar Cell – Basic Principle of Operation:

 

 

 

Solar Cell Structure and Principle of Operation

Solar cells basically consist of p-type and n-type semiconductors with two metal contacts, one in p-type and the other in n-type as shown in figure. These two types of semiconductors form a p-n junction with n-type facing the sun.

Absorption of Solar Radiation

Sunlight is composed of photons containing energy which correspond to the different wavelengths of the solar spectrum. When photons strike a solar cell, depending upon the type of semiconductor used, some low energy photons (infrared) are not absorbed by the electrons in the semiconductor material while some high energy photons are absorbed for excitation of electrons into the conduction band and the excess of energy is released as heat.These excited electrons are attracted toward the n-type semiconductor. This causes more negative charges in the n-type and more positive charges in the p-type semiconductors. If an electric load is connected between the two types of semiconductors through the metal contacts,electrons start flowing from n-type to p-type semiconductors via the load. Thus photon energy is directly converted to electrical energy without an intermediate mechanical or thermal process.

The cell is a current source of DC type. This DC current is used directly in applications. AC current can also be produced by using inverters.