What is photovoltaic effect?

A PV system works on the principle of converting sunlight directly into electricity through the use of solar cells in combination with several other basic components.

The solar cell is the building block of a PV system. Several solar cells are connected together to form a solar panel. Several solar modules connected together make up a solar panel. And finally, many solar panels connected together form a solar array.

PV systems also include cabling, monitoring, tracking, and protection equipment as listed in the diagram. Inverters are used to convert the direct current produced by the solar modules to the alternating current required by most of the electrical equipment used in residential, commercial and industrial applications. Batteries can be used to store electricity for later use.

Let's take a closer look at the primary building block of a PV system, the solar cell.

The solar cell is made of semiconducting material, such as silicon that has been "doped" with an agent that has the propensity to either gain or lose electrons, such as phosphorus or boron.

Silicon that has been doped with phosphorus can lose electrons and is known as an N-type semiconductor. This is because phosphorus has 5 valence electrons as compared to silicons 4.Since an N-type semiconductor wants to lose electrons, it acquires a positive charge. Conversely, silicon that has been doped with boron has a shortage of electrons, or an abundance of "holes", and is known as a P-type semiconductor. This is because boron has 3 valance electrons as opposed to silicon's 4. So P-type silicon wants to lose holes and gain electrons, and as a result, acquires a negative charge.

When these two types of silicon are joined together they form a PN junction. This is the foundation of the solar cell. When the P and N zones are brought into contact the surplus holes and electrons from each side recombine, creating ions. This depletes the holes and electrons in this region, hence the term "Depletion Region". A voltage barrier forms in this zone.

Eventually, only ions are found in this region. They create an internal electric field (E) at the junction. The force of the electric field acts in the opposite direction to the diffusion force and prevents the remaining free charges in each zone to cross the junction to recombine.

When a photon hits a solar cell, one of three things can happen

-The photon can pass straight through the cell. This happens to low energy photons.

-The photon can be reflected by the surface of the solar cell.

-Or the photon can be absorbed the silicon to create electricity.

This is known as the photovoltaic effect.

How do solar panels work?

The Earth intercepts a lot of solar power: 173,000 terawatts. That’s 10,000 times more power than the planet’s population uses. So is it possible that one day the world could be completely reliant on solar energy? Richard Komp examines how solar panels convert solar energy to electrical energy.

How is the efficiency of a solar cell measured?

How to calculate how many solar modules you need?

How efficient are solar cells today?

Researchers are constantly working to improve the efficiency of solar cells. Each new wave of solar cells gives rise to a new generation of photovoltaic devices.

Today, there exist three generations. They are

- Crystalline Silicon

- Thin film

- and Emerging PVs

Efficiencies across the three generations vary between 10% and 46%. Let's look at this in detail.

What is the maximum possible efficiency of a solar cell?

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