Last updated on Sunday, October 15th, 2023

The solar cell is a part of semiconductor physics.   You may be very well aware of the p-n junction diode working. Then how LED works? With the help of the different LED’s, you had also determined the Planck’s constant.

Solar Cell an Introduction

In a layman language, you can say that solar cell converts sunlight into the electricity. This solar cell made by a p n-junction diode. To construct the Solar cells silicon, gallium arsenide, cadmium sulphide are mainly used. As you know that silicon shows the thermal properties. What is it means?

Thermal property means of the silicon material;  when electron and hole recombination takes place energy release in terms of the heat. Because of its silicon diode or any other device starts to heat up and you feel hot after some time.

On the other hand, gallium arsenide shows the optical properties when electron-hole recombinations take places. It means when electron-hole recombination takes place a photon emits. The principle of light-emitting diode (LED).

So, the solar cell also a p-n junction diode on which when sunlight falls it behaves like a battery, but how it works?

Solar Cell Working

When sunlight falls on the p-n junction diode, photons are absorbed and electron-hole pairs are generated in p and n side of the diode.  The electron-hole pairs that are produced near to to the junction reach the space-charge region by the diffusion process.

Across the space-charge region, there is a strong barrier field that makes separated electrons and holes from a pair. So the electrons from p region move towards the n-region and same are true for the holes. They also move from the n-region towards the p-region.

By this process electron and holes accumulated across the junction and gives rise to a voltage. If any load is connected with the diode, a current will flow in the circuit. The current depends on the sunlight intensity directly.

Applications of Solar Cells

1. In satellites and space vehicles
2. Power supply for the household items

1Q. List Types of Solar Cells?

Ans. There are several types of solar cells, including:

Monocrystalline silicon solar cells: These are made from a single crystal of silicon and are highly efficient at converting sunlight into electricity.

Polycrystalline silicon solar cells: These are made from multiple crystals of silicon and are less efficient than monocrystalline cells, but they are also less expensive.

Thin-film solar cells: These are made from thin layers of semiconductor materials, such as cadmium telluride or copper indium gallium selenide, and are lightweight and flexible.

Amorphous silicon solar cells: These are made from non-crystalline silicon and are less efficient than crystalline silicon cells, but they can be manufactured at a lower cost.

Concentrated solar cells: These use lenses or mirrors to focus sunlight onto a small area of highly efficient solar cells.

Organic solar cells: These use organic materials, such as polymers, to absorb sunlight and generate electricity.

Dye-sensitized solar cells: These use a layer of dye molecules to absorb sunlight and generate electricity.

2Q. Which Solar Cell is more efficient?

Ans. Monocrystalline silicon solar cells are generally more efficient than other types of solar cells. They have a higher efficiency because they are made from a single crystal of silicon. It allows for a greater electron mobility and less energy loss. Monocrystalline solar cells typically have efficiencies in the range of 15-20%, while some advanced designs have achieved efficiencies of over 25%.

3Q. Which factors decides the solar cell efficiency?

Ans. The efficiency of a solar cell is based on several factors, it includes;

1. the quality of the materials used,
2. the design of the cell,
3. and the environmental conditions in which it will operate

Different types of solar cells are for different applications, depending on various factors such as cost, durability, and flexibility.

4Q. List fabrication process of solar cells?

Ans. The fabrication process of solar cells  following some steps:

1. Silicon production: The first step in making solar cells is to produce high-purity silicon, which is typically done through a process called the “Czochralski process”. This process involves melting silicon in a crucible and then slowly pulling a single crystal of silicon out of the molten material.
2. Wafer production: The silicon crystal is then sliced into thin wafers using a wire saw or other cutting tool.
3. Surface texturing: The surface of the silicon wafer is then treated to create a rough texture, that helps to trap more light, and improve the efficiency of the solar cell.
4. Doping: The silicon wafer is then doped with impurities (donor and/or acceptor) to create a p-n junction. It is the basis of the solar cell’s ability to convert light into electricity. This is typically done by diffusing boron into one side of the wafer and phosphorus into the other side.
5. Contact formation: The next step is to add metal contacts to the top and bottom of the solar cell. It allow the electricity generated by the cell to be collected and used. This is typically done by depositing a thin layer of metal, such as aluminum or silver, onto the surface of the cell.
6. Anti-reflection coating: Finally, an anti-reflection coating is added to the surface of the solar cell to reduce the amount of light that is reflected away and improve the efficiency of the cell.

When these steps are completed, the solar cells are typically assembled into modules or arrays that can be used to generate electricity.

5Q. List types of solar cell modules?

Ans. There are several types of solar cell modules:

Monocrystalline solar modules: These modules are made from monocrystalline silicon solar cells and are typically the most efficient type of solar module. They have a dark black color and a uniform appearance.

Polycrystalline solar modules: These modules are made from polycrystalline silicon solar cells and are slightly less efficient than monocrystalline modules. They have a blue color and a speckled appearance.

Thin-film solar modules: These modules are made from thin layers of semiconductor materials, such as cadmium telluride or copper indium gallium selenide, and are lightweight and flexible. Thin-film modules are less efficient than crystalline modules but can be more cost-effective in certain applications.

Bifacial solar modules: These modules have solar cells on both sides of the panel, which allows them to capture sunlight that is reflected off the ground or nearby surfaces. Bifacial modules can be more efficient than standard modules in certain conditions.

Concentrated solar modules: These modules use lenses or mirrors to focus sunlight onto a small area of highly efficient solar cells. Concentrated modules are typically used in utility-scale solar installations.

Building-integrated solar modules: These modules are designed to be integrated into the design of a building, such as solar shingles or solar glass. They can be more aesthetically pleasing than traditional solar panels and can be used to generate electricity while also serving as a building material.