How Do Solar Cells Work?

Solar Cell Converting Sunlight_To_Electricity_How_It_Works

We are pretty well aware of the process that converts electrical current into light from which we can pierce darkness and find our way around a house, street or entire neighborhood. But what has taken a lot of time to master has been converting light (specifically, sunlight) back into electric current to power homes, calculators, satellites and many other items through the use of solar energy.

One of the tools used to make this solar-powered electricity has been the solar cell, also knowns as a photovoltaic, or PV cell. It takes many PV or solar cells to make a single solar panel that goes on top of a home, but it takes only a few to make the solar panel that runs a basic calculator.

The solar cell is where the magic happens in turning sunlight into usable energy. How do solar cells work to make this happen? Let’s take a deeper look into the construction and operation of a solar cell.

Sunlight as a Hammer

The first thing that has to be understood is the power of solar energy and what sunlight can do to contribute to electric power. In physics, there is a photoelectric effect, in that any material can eject electrons when sunlight shines on it. Sunlight is like a hammer on a rock; the photons in sunlight hit the atoms and molecules of a material (for solar cells, we use silicon) and breaks the bonds that hold electrons in the “orbit” of the atom, releasing the electrons.

There free electrons are what makes the electric current. The key is corralling all these free-wheeling electrons and getting them to move in an orderly fashion so as to create an electric current. This is where the solar cell does its work.

Solar Cells: The Silicon Corral

A solar cell is made of a semi-conducting material, such as silicon. When sunlight hits the silicon in the solar cell, some of the sun’s energy is absorbed by the silicon like a sponge, and that energy breaks loose some electrons from the silicon atoms and they become “free agents,” so to speak.

The silicon in the solar cell is actually two types thanks to “doping” with other elements – one is n-type, which has spare electrons, and p-type, which has gaps where electrons should be. These two types of silicon are right next to each other and they provide a sort of “channel” that gathers these “free agent” electrons, corrals them, and – thanks to metal contacts on either end of the broader solar panel – send them in an orderly fashion down the channel and toward the contacts to produce electric current.

Solar Cells: Why So Expensive?

This is an interesting question. It is well known that silicon is very abundant on the earth, and is the cheapest semi-conducting material on the planet. So if it’s so cheap, how come solar power is so expensive?

It’s a complex question, but from a scientific point of view the reason is this – silicon possesses a high electric resistance, which means there are a lot of electrons that are not able to achieve an electric current. This means the solar panels have to be much larger in order to generate the current needed to power the electricity of a home, water heater or parking garage. Plus, silicon absorbs a lot of energy, which means there is wasted sunlight in a sense that is unable to be converted into electricity.

One of the ways that solar power and solar cells could eventually be cheaper is to make them smaller. There is a semi-conducting material called gallium arsenide, which allows free electrons to flow up to five times faster on its surface than silicon, and it has properties that allow it to absorb less sunlight energy and convert more of it into electricity. It works well for satellites and some military applications, but it is very expensive to produce and very difficult to make in a large commercial scale for solar panels.

However, with further development and research, scientists are looking into a thin-layer gallium arsenide overlay on silicon solar cells (as well as silicon wafers for microchips) to at least bring some of the characteristics of gallium arsenide to a silicon solar cell, potentially degrading its resistance and absorption and increasing the efficiency of the cell to make it more powerful and thus, cheaper in the long run.

Leave a Reply