How Electricity is Generated by a Solar Cell?

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Lets understand Solar Energy first

Solar energy is the energy force that sustains life on Earth for all plants, animals, and people. It provides a compelling solution for all societies to meet their needs for clean, abundant sources of energy in the future.

The source of solar energy is the nuclear interactions at the core of the Sun,
where the energy comes from the conversion of hydrogen into helium. Sunlight is readily available, secure from geopolitical tensions, and poses no threat to our environment and our global climate systems from pollution emissions.

The Earth is essentially a huge solar energy collector receiving large quantities of solar energy

The Solar Radiation & its transmission

Solar energy is primarily transmitted to the Earth by electromagnetic waves, which can also be represented by particles (photons). The Earth is essentially a huge solar energy collector receiving large quantities of solar energy. This energy manifest in various forms, such as direct sunlight used for plant photosynthesis, heated air masses causing wind, and evaporation of the oceans resulting as rain, which forms rivers and provides hydropower.

More energy from sunlight strikes the Earth in 1 hour (4.3 × 1020 J)
than all the energy consumed on the planet in a year (4.1 × 1020 J). Although the Earth receives about 10 times as much energy from sunlight each year as that contained in all the known reserves of coal, oil, natural gas, and uranium combined, renewable energy has been given a dismally low priority by most political and business leaders.

How we use solar energy

The solar energy that we use to produce electricity is generated by a process known as Photovoltaic Effect. It is made possible by using a semiconductor known as Silicon.

A semiconductor is neither a perfect conductor nor an insulator but falls between them. This is why a semiconductor is used to convert solar energy. By adding impurities into the silicon, it can be made possible for a silicon to act as a conductor or an insulator. This process of adding impurities is called Doping.

A semiconductor is neither a perfect conductor nor an insulator but falls between them.

Photovoltaic Effect

p-n junction

The photovoltaic effect put simply is just a movement of free electron from negative to positive. A solar cell is used for this process. It is a device that is made from silicon. In case of solar cell, If impurities are phosphorus-atoms, which have five outer electrons, only four electrons are required to fit the atom into the silicon crystal structure, the fifth electron is mobile and free.

So in this region of the crystal there are many (a majority) free negative charges, therefore it is called n-region.

The photovoltaic effect put simply is just a movement of free electron from negative to positive region

Vice versa for the p-region, by doping the crystal with boron atoms, which have only three outer electrons, one electron is always missing for a complete binding into the crystal structure.

This electron could be “borrowed“ from neighboring atoms, so the place of the missing electron is shifted. This missing electron could also be seen as a “hole“ with a positive charge that is mobile and wandering.

There are much more free holes than free electrons in the p-regions, so the electrons are called minority charge carriers there.

The Principal of Photovoltaic Effect

Due to the differences in concentration at the “frontier“ between the two regions, electrons diffuse into the p-regions and “holes“ into n-regions,
therefore an electrical field in the formerly electrical neutral junction comes into existence. It increases until a further practical diffusion of carriers is avoided by it.

Light (or sun radiation) falling into the semiconductor generates electron hole-pairs, causing an increase in the concentration of the minority charge carriers by several orders of magnitude.

These charge carriers diffuse to the space charge zone and are divided by the electric field there. Between the contacts of the n-side and p-side a tension V could be detected, as shown in the figure above. When a load resistor R is applied, a current I flows through it, and electric power is dissipated.

There you have it. Electricity generation through solar.

Reference: Solar Electric Power Generation – Stefan Krauter

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1 thought on “How Electricity is Generated by a Solar Cell?”

  1. Rajesh says:

    Nice Information

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