Which element is mostly used in making solar cells?

A solar cell, also called a photovoltaic (PV) cell, is a device that converts sunlight directly into electricity. Most solar cells in use today are made from silicon, which accounts for more than 90% of the world's solar cell production.

Silicon is a metalloid and a semiconductor. Its electrical conductivity lies between that of conductors (such as copper) and insulators (such as glass). It is the second most abundant element in the Earth's crust after oxygen, found mainly as silica (silicon dioxide, sand and quartz) and silicates.

How a silicon solar cell works:

Pure silicon is "doped" with small amounts of other elements. Adding phosphorus (with five valence electrons) creates n-type silicon, with extra electrons. Adding boron (with three valence electrons) creates p-type silicon, with "holes" (missing electrons).

A layer of n-type and a layer of p-type silicon are joined to form a p-n junction, which creates an electric field.

When sunlight (photons) falls on the cell, it knocks electrons loose from silicon atoms. The electric field at the junction pushes these electrons in one direction, creating an electric current. This is called the photovoltaic effect, first observed by the French scientist Edmond Becquerel in 1839.

Types of silicon solar cells include monocrystalline (most efficient, made from single crystals), polycrystalline (cheaper, made from many crystals) and thin-film amorphous silicon. Other materials, such as cadmium telluride, gallium arsenide and perovskites, are also used.

Silicon is also the basic material for computer chips and integrated circuits; this is why California's technology hub is called "Silicon Valley", and Bengaluru is called the "Silicon Valley of India".

India's National Solar Mission was launched in 2010, and India has set a target of 500 GW of non-fossil fuel capacity by 2030. The Production Linked Incentive (PLI) scheme supports domestic manufacturing of solar modules.

Why not the other options?

• ✗Germanium is a semiconductor too, but it is costlier and used in specialised cells and electronics.
• ✗Copper is a conductor used in wires.
• ✗Carbon (as graphite) is used in electrodes, not as the main material of solar cells.