The sun is practically an unlimited source of energy. On a bright sunny day, 1000 W/m2 of energy reaches the earth's surface. We harness this energy in our homes and offices, calculators, emergency road signs, and satellites. Our dependence on the sun continues to increase as solar technology develops
What is a Solar Cell?
A solar cell is a device that converts light energy (sunlight) to electricity. It does not necessarily store electricity, but simply converts sunlight when it is available. Solar cells are based on the concepts of photovoltaics, or the science of converting sunlight into electricity, first discovered by Edmond Becquerel in 1839. The first solar cell was actually created in1954.
Parts of a Solar Cell
Semiconductor: the semiconductor in a solar cell is often made of silicon. As a semiconductor, silicon has both the properties of a metal (conductor) and an insulator.
Dopants: small amounts of impurities introduced to the silicon. In a solar cell, phosphorus and boron dopants are used. The elements establish an N-type side and a P-type side.
N-type side: the negative type side is doped with phosphorus. This results in the silicon having an excess of electrons.
P-type side: the positive type side is doped with boron, resulting in "holes" in the silicon. Holes carry a positive charge
Junction: The result when N-type side and P-type side are combined to form an electric field. The junction creates a barrier, which only allows electrons to flow to the N-side.
How a Solar Cell Works
When energy is received from the sun in the form of photons, some of the photons are absorbed near the junction, freeing the electrons and holes in the silicon. The photons of light give enough energy for the electrons to cross the junction, where they can be picked up on the metal contacts on the surface of the solar cell and move through an external circuit. After moving through the external circuit and performing work (such as powering a lamp or motor) the electrons return to the solar cell.
With demand and efficiency in solar cells rising, solar power is becoming increasingly competitive with fossil fuels. New research will provide cost breakthroughs and mass consumption will decrease prices. As an environmentally friendly resource, solar power looks to have a bright and sunny future.