In 1839, a French physicist named Edmund Bequerel first noticed that some materialsproduce small amounts of electrical current when exposed to light. In 1905, Albert Einstein described the photovoltaic effect which is what modern solar technology is based on. The first photovoltaic panel was built in 1954 by Bell Laboratories. It was called a solar battery and was mostly a curiosity project because it was so expensive and unrealistic for widespread use. In the ‘60s, the space industry started seriously using photovoltaics to provide power to spacecrafts. During the energy crisis in the ‘70s, photovoltaics gained recognition as a possible source of power for non-spacecraft uses. Today, we see and hear about solar as an alternative power source for the average home. There are even rebates and incentives for using solar energy. So, what is a solar cell and how does it work?
The Solar Cell
Solar cells are the basic building block of a photovoltaic energy system. Photovoltaics is the direct conversion of light into electricity. A solar cell absorbs photons, which are tiny particles of sunlight.
Solar cells are usually shaped like a square with the corners clipped. They are manufactured out of a semiconductor material. This material is made into a thin wafer that is specially treated to form an electrical field. The wafer is positive on one side and negative on the other.
When photons strike the solar cell, electrons are knocked loose from atoms in the semiconductor material. Photons act like the cue ball in a game of pool. The cue ball transfers its energy to the colored balls it strikes. Likewise, energy is transferred from the photons to the electrons.
When electrical conductors are attached to both sides of the wafer, it forms an electrical circuit. These free electrons can then be captured in the form of an electrical current (electricity). When these free electrons are captured, an electric current is created. This current can then be used as electricity to power a load, such as a light fixture.
Solar Cell Materials
Semiconductor materials, like silicon, share properties of conductors and insulators. Semiconducting materials have a range known as the band gap, which represents the spectrum of energies that cannot excite the material’s electrons. Silicon has a band gap that can be crossed over by a single photon’s worth of energy, which makes silicon an excellent material for solar cells.
Silicon is the most widely used material in photovoltaic cells, but graphene is one of the contenders. In theory, graphene could be a much better base material for solar cells, due to its potential to be packed more densely on the panels and high electrical efficiency. However, graphene’s main drawback is its band gap, which prevents the material to be properly excited by a photon’s energy. There are complex graphene devices that are currently available, but the cost of producing them offsets the potential benefits, for the time being.
What to Expect
Solar technology is sure to continue evolving in a multi-faceted fashion. While progress may grow incrementally or by leaps and bounds, the future seems to be heading towards a more widespread use of solar systems.