The Sunlight falling on the earth is basically bundles of Photons or packets of small energy. Each photon in a bundle or packet possess a finite amount of energy. In a solar spectrum , there are many bundles or photons of different energy capacity.
For generation of electricity, these photons must be absorbed by the solar cells. This absorption of photon largely depends on the energy of the photon and the band gap energy of the semi-conductor material of a solar cell.
The photon and the band gap energy of semi conductor material is described in terms of Electron-Volt (eV). The eV is a unit of energy.
Also Read : What is a solar cell?
So, the working of a solar cell can be explained as follows :
- Photons in the sunlight falling on the solar cell/s front face are absorbed by the semi-conducting materials.
- Free electron-hole pairs are generated. Electrons are considered as negative charge and holes are considered as positive charge. When a solar cell is connected to electrical load, a potential difference generates at both the ends. The holes and electrons near the junction are separated by from each other. The holes are collected at positive terminal or the anode and the electrons get deposited at the negative terminal or cathode. Electron potential is built at the terminals due to the separation of negative and positive charges. Due to the difference between the electric potentials at the terminals we get voltage across the terminals.
- Voltage developed at the terminals of a solar cell is used to drive the current in the circuit. The current in the circuit will be direct current or DC current.
So,the solar cell with day light falling on it can directly drive DC electrical appliances. But, the amount of electricity generated is proportional to the light rays falling on the solar plates.
So, the amount of electricity generated throughout the day is not constant and is lower in the morning and the evening in comparison to the mid-day.
The current generated also depends on several other factors. I will discuss on the parameters that affect the generation of current from a solar cell in another post.