How does solar panel work?

Solar energy is fast gaining popularity across the world as a source of clean and renewable form of energy. We can see the number solar panels installed for commercial as well as non commercial purposes increasing with each passing day. It would be interesting to see how the sunlight falling on these solar panels is converted to electricity for lighting up our homes and also many other purposes.

Solar panels are made of smaller units called solar cells. Silicon is the most common semiconductor used for making solar cells. Each individual solar cell is basically a crystalline silicon junction which is sandwiched between conductive layers. Silicon junction is where electricity is generated and the conductive layers carry the generated electricity to the external circuit.

A solar cell uses 2 different layers of silicon – N  type silicon (which has extra electrons) and P type silicon (which has extra spaces for electrons, called holes). Electrons can wander across across the junction between P type silicon and N type silicon. This creates a positive charge on one side and a negative charge on the other side. This positive and negative charge creates what is called an electric field. Let’s now see how this structure of the silicon is used to generate flow of electricity.

Light can be considered as a flow of tiny individual light particles called photons. These photons keep on striking the silicon solar cells which are exposed to sunlight. Normally, there is a bond between each silicon atom and its neighbouring atoms which keeps the electrons in one place. Some of the photons strike the silicon solar cells with enough energy to knock off an electron from the silicon bond, leaving behind a hole. Now the negatively charged electron is free to move around. But as we saw above, there is an electric field formed at the P-N junction. Due to the presence of the electric field, the electron is drawn to the N side, while the hole is drawn towards the P side. When many such electrons move towards the N side, they form the electric current in a solar cell. These moving electrons are collected by the thin metal plates at the top of the solar cell. Now the electrons flow through whichever external circuit is connected to the cell, such as that for lighting up a bulb.

Depending on the power requirement, it is possible to connect multiple solar cells together and provide power to the external circuit.


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