Solar Cell: Definition, Types, Construction & Working

What is Solar Cell?

A solar cell, or photovoltaic cell, is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon. Individual solar cell devices can be combined to form modules, otherwise known as solar panels.

Solar cells can be found almost everywhere, from children’s toys, flashlights, calculators, and satellites, etc. Solar cells are also known as photovoltaic cells (PV). Photo means “light” and voltaic means “electricity”, which generates electricity directly from visible light means of photovoltaic effect.

A group of PV cells that are electrically connected and placed in a frame is called a module (or solar panel), which can then be combined into larger groups of modules to form a solar system.

Photovoltaic cells are made of semiconductors such as silicon, which is most commonly used. When light hits the cell, some of it is absorbed in the semiconductor material. The energy of the absorbed light is transferred to the semiconductor. The transferred energy then releases electrons and lets them flow freely.

PV cells have electric fields that force electrons released by light absorption to flow in a specific direction. This flow of electrons is an electric current; With the metal contacts attached to the top and bottom of the PV cell, we can draw the power for external use.

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For more information read our article: 1. What is Solar energy? 2. What is Solar penal? 3. What is a solar power system( off-grid and on-grid)?

Solar Cell

Construction of Solar Cells

The semiconductor materials such as arsenide, indium, cadmium, silicon, selenium and gallium are used to manufacture the PV cells. Usually, silicon and selenium are used to manufacture the cell.

Consider the following figure, which shows the structure of the silicon photovoltaic cell. The top of the cell is made of a thin layer of p-type material so that the light can easily enter the material. The metal rings are arranged around p-type and n-type material that act as positive and negative output terminals, respectively.

Solar cell Diagram

The multi-crystalline or monocrystalline semiconductor material forms the individual unit of the PV cell. The single-crystal cell is cut out of the volume of the semiconductor material. The multi-cells are obtained from the material that has many sides.

The output voltage and current obtained from each unit of the cell are very small. The output voltage is 0.6V and the current is 0.8V. The various combinations of cells are used to increase output efficiency.

Solar cell Diagram

Solar cell Diagram

Working of Solar Cell

When sunlight strikes a solar cell, electrons in the silicon are ejected, which results in the formation of “holes”—the vacancies left behind by the escaping electrons. If this happens in the electric field, the field will move electrons to the n-type layer and holes to the p-type layer.

I know, I know it looks like rocket science, but not let’s discuss it in detail. A solar cell is made of two types of semiconductors, called p-type and n-type silicon.

The p-type silicon is produced by adding atoms such as boron or gallium that have one less electron in their outer energy level than does silicon. Because boron has one less electron than is required to form the bonds with the surrounding silicon atoms, an electron vacancy or “hole” is created.

The n-type silicon is made by including atoms that have one more electron in their outer level than silicon, such as phosphorus. Phosphorus has five electrons in its external energy level, not four. It bonds to its neighboring silicon atoms, but an electron is not involved in the bond. Instead, it can move freely within the silicon structure.

A solar cell consists of a layer of p-type silicon, which is arranged next to a layer of n-type silicon. There is an excess of electrons in the n-type layer and there is an excess of positively charged holes in the p-type layer.

Near the junction of the two layers, the electrons on one side of the junction (n-type layer) move into the holes on the other side of the junction (p-type layer). This creates an area around the junction called the depletion zone where the electrons fill the holes.

When all the holes in the depletion zone are filled with electrons, the p-type side of the depletion zone (where holes were originally present) will now contain negatively charged ions and the n-type side of the depletion zone (where electrons were present) will now contain positively charged ions.

The presence of these oppositely charged ions creates an internal electric field that prevents electrons in the n-type layer from filling holes in the p-type layer.

If you connect the n-type and p-type layers with a metallic wire, the electrons will travel from the n-type layer to the p-type layer by crossing the depletion zone and then go through the external wire back of the n-type layer, creating a flow of electricity.

Types of Solar cell

The following are the different types of solar cells:

  • Amorphous Silicon solar cell (a-Si)
  • Biohybrid solar cell.
  • Cadmium telluride solar cell (CdTe)
  • Concentrated PV Cell (CVP and HCVP)
  • Copper indium gallium selenide solar cells (CI(G)S)
  • Crystalline silicon solar cell (c-Si)
  • Float-zone silicon.

Most solar cells have some other type of silicon. In fact, about 90% of all solar or photovoltaic cells contain silicon. The efficiency of a solar cell to convert sunlight into power is directly proportional to the purity of their silicon molecules.

Also, the better the efficiency, the more expensive the solar panel is. However, this aspect should not be the deciding factor for choosing one type and not the other.

In addition to the hybrid version, solar panels are classified into three types, mainly in commercial production. All three types are silicon semiconductor-based.

1. Monocrystalline solar cells

These solar panels are made using thin wafers of silicon, which are extracted from artificially grown crystals. Single crystals developed in isolation help to form these cells and make them the most efficient.

This is why these are the most expensive among the other types. Compared to their counterpart polycrystalline cells, monocrystalline solar cells are about 35% more expensive and provide an efficiency rate between 15–24%.

Monocrystalline solar cell

2. Polycrystalline solar cells

Polycrystalline solar cells are also made using thin silicon wafers derived from artificially grown crystals, the only difference being that these are not single crystals. Rather, they use multiple interlocking silicon crystals propagated simultaneously.

Therefore, their production is less expensive and they still offer an efficiency rate of 13–18%.

3. Amorphous solar cells

The cheapest form of solar cells is an amorphous solar cell. These are newly launching cells that are manufacture in a unique way. They avoid the use of crystals. Instead, their production process involves thin silicon deposits on the backing substrate.

Amorphous solar cells provide two major benefits, ie. Flexibility in solar cells with its extremely thin silicon layer, and high efficiency in low levels of light during winter.

But, while these promise the above benefits, they also compromise on efficiency. They provide the lowest efficiency rates of 7% – 9% compared to the other two variants. Thus, they require about twice the panel area to give the same output.

Until now, they do not even have an approved production technology in the industry, and therefore, they are less robust than the other two types of solar panels.

4. Hybrid solar cells

It is not a completely solar cell, but a hybrid solar cell is a mixture of monocrystalline solar cells and amorphous solar cells. Hybrid solar cells called HET (heterojunction with intrinsic thin layer) solar cells.

Compared to each individual type of solar cell, the hybrid type is the most efficient due to the combination of the power of the two solar cells. These work best during sunny seasons, ie beyond the 250C temperature. In view of the same, this helps generates about 10% more electricity.

If one has to choose the best, polycrystalline cells prove to be the most suitable for most installations due to their value for money, design and efficiency rate.

Material Uses in Solar Cell

Solar cells are typically named after the semiconducting material they are made of. These materials must have certain characteristics in order to absorb sunlight.

  • Crystalline silicon
  • Amorphous Silicon (a-Si)
  • Copper-Indium Gallium Diselenide (CIGS)
  • Gallium arsenide thin film
  • Cadmium Telluride (CdTe)
  • Monocrystalline silicon
  • Epitaxial silicon development
  • Polycrystalline silicon
  • Ribbon silicon
  • Mono-like-multi silicon (MLM)

Advantages of Solar Cell

  • Renewable energy: The energy can be used to generate electricity as well as heat in the house, either through solar PV or solar thermal energy.
  • Economical Energy: Solar cells are a great way to save money on your electricity bill because you don’t pay for the energy you generate.
  • Environmentally friendly energy: There is almost no pollution with solar cells. Discharge of waste and pollution are inevitable in connection with the manufacture of solar cells.
  • Innovative energy: Photovoltaics is a popular topic in green energy and is considered a good solution for preventing climate change.
  • Infinite Energy: If you have the ability to draw energy from the sun’s rays, it is a source of energy that will never be depleted.
  • Long-term energy: PV systems often have a long service life and a good service life.
  • Selling energy: If your home has solar panels, it is often easier to sell the property at a higher price.

Disadvantages of solar cell

  • Interior needs: Not all households that meet their requirements and can get the most out of their solar cells.
  • High investment requires: The installation costs for solar modules are relatively high.
  • Seasonal energy: Compared to other types of renewable energies, the solar power plant is highly seasonal.
  • Difficult to install Solar panels in your home: It may be more difficult to install solar panels in older households as they often have different designs that can provide shade.

Use of Solar Cell

  • Solar cells are very useful in powering space vehicles such as satellites and telescopes.
  • It may be used to charge batteries.
  • Used in light meters.
  • It is used to power calculators and wristwatches.
  • It can be used in spacecraft to provide electrical energy.

For more information read our article:


What is a Solar cell?

A solar cell, or photovoltaic cell, is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon. Individual solar cell devices can be combined to form modules, otherwise known as solar panels.

How do solar cell works?

When sunlight strikes a solar cell, electrons in the silicon are ejected, which results in the formation of “holes”—the vacancies left behind by the escaping electrons. If this happens in the electric field, the field will move electrons to the n-type layer and holes to the p-type layer.

What are the types of solar cells?

Types of solar cells:
1. Amorphous Silicon solar cell (a-Si)
2. Biohybrid solar cell.
3. Cadmium telluride solar cell (CdTe)
4. Concentrated PV Cell (CVP and HCVP)
5. Copper indium gallium selenide solar cells (CI(G)S)
6. Crystalline silicon solar cell (c-Si)
7. Float-zone silicon.