What is a solar cell? How do solar cells work?
Solar cells are sandwiched between two paper-thin wafers of silicon. Like a food sandwich, a solar cell sandwich also varies according to its application. At present, a total of six types of solar cells are being used.
The solar cell is a sandwich that absorbs the sun’s rays and generates electricity by playing catch between its two layers. It consists of two wafers of 160-micron thick silicon bonded together. (1 micron is equal to 1/1,000 mm)
Why solar cell is called a Photovoltaic cell?
Sun rays are particles of light coming from the sun and reaching the earth at a speed of 3 lakh kilometers in a second. A particle of light is called a photon. Einstein called them grains of light. In a solar cell, the electricity is generated by playing with photons so it is called a photovoltaic cell.
When did solar cells start?
In 1839, French physicist Edmond Becquerel discovered that sunlight can generate electricity. However, the tool to actually implement it (solar cells) was invented for satellites in the 1960s. Then in the 1980s, people started installing solar panels on their roofs. Solar cells with the highest power output were discovered after 2000.
How do solar cells generate electricity?
When a photon hits silicon at a speed of 300,000 kilometers per second, the electrons of the silicon atom are thrown out by its impact. As its space becomes vacant, the neighboring electron rushes there. When its space becomes vacant, its neighboring electron rushes to fill that space. The movement of electrons is called electricity. A thin one-micron layer of phosphor is deposited on a wafer before sandwiching two wafers of silicon so that all electrons run in the same direction. A similarly thin layer of boron is deposited on another wafer of silicon. Phosphorus has more electrons than silicon while boron has less than silicon. A silicon sandwich is electron-rich on one side and electron-deficient on the other. Now, if a photon hits this sandwich, all the released electrons immediately rush to the less-electron side. There are billions of light rays. Each contains millions of photons. If it continues to strike, millions of electrons are pushed from one side and start running to the other side. If it runs in one direction, an electric current is created.
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Types of Solar cells
Organic solar cells
with atomic layers of various carbon-based natural materials produces only 11 percent of electricity and solar cells do not last as long, but natural materials are more suitable for large-scale use. Electricity can be made by applying such a layer on cloth.
Transparent solar cells
In transparent solar cells, solar concentrator chemicals are sprayed on the solar concentrator. By spraying solar concentrator chemicals onto transparent glass or plastic, they block sunlight’s ultraviolet and infrared rays and convert their energy into electricity. These solar cells are rapidly becoming popular.
Crystalline solar cell
A crystalline solar cell is approximately made from 95 percent of silicon. By adding other substances in place of phosphorus and boron in it, increasing or decreasing electricity is produced. In making silicon, silicon crystals are joined by pressure in the cold process method. It generates 22 percent of electricity. Another method is to melt silicon into glass in a melt process. The solar cell in this method is fragile, but it can generate 26.6 percent of electricity.
Thin film solar cell
This method is used to make solar cells used in calculators. In thin film solar cells, instead of cutting a 200-micron wafer of silicon, 15-20 micron layers of semiconductor materials such as cadmium telluride and copper indium gallium selenide are sprayed onto glass or plastic. So 22.1 percent to 23.3 percent of electricity is generated.
How much electricity can a solar cell generate?
A solar cell generates 1.5 watts of electricity. If 36 solar cells are connected, then 54 watts are obtained. That much electricity can charge a 12-watt battery continuously. 36 solar cells are joined together to form a module. One module can charge a 432-watt battery continuously. 36 such modules are paired to form an array. One array can charge a 15,552-watt battery continuously. The condition is that intense sunlight should fall on the solar cell. If the light is weak, the electricity will be less.
A typical solar cell generates 16.5 percent of electricity from sunlight. New ideas sandwiched between solar cells create incremental electricity. That is, different type of solar cell is used in different work according to its requirement.
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