Solar cells (photovoltaic cells) convert the energy of the sun into electricity.

Whether they’re embedded in your calculator, laying on the roof of your house, or orbiting the earth on a satellite, they rely on the same principle –  the photoelectric effect.

This is the ability of a material object to emit electrons after being struck by light.

Silicon has some of the properties of metals as well as some of the properties of electrical insulators.

It is what we refer to as a semiconductor.

For these reasons, it is a critical component of solar cells.

Making Electricity

Sunlight is made of wave or particles we call photons.

Photons are emitted by the sun and pretty much provide all of the power used on Earth. When photons strike a silicon atom, electrons are released. These electrons can be used as energy to provide, for example, power for machines.

But this is only part of what solar cells do. It then has to funnel these loose electrons into a stream, or an electric current.This is done by creating an imbalance in the cell.

Electricity does not “like” imbalances, and so, it moves to overcome the imbalance. By manipulating this property of electricity, we can use solar cells to channel the electrons it has collected into an electrical system, or to charge a battery.

Internal Organization

It is the internal organization of silicon that makes it possible to create this imbalance and compel electrons to move in the direction we wish it to move.

Silicon atoms are densely packed in a tightly bound formation. By forcing small amounts of other substances into the structure of the silicon, we can create two types of silicon - n-type and p-type.

N-type silicon has a surplus of electrons while p-type has a deficit of electrons. In this situation, we have the needed imbalance to compel an electric current to move in the direction we wish it to move.

By placing these two types of silicon side by side within solar cells, we cause electrons that are shaken loose by photons to move into the p-type silicon. The electrons fill the gaps in the p-type silicon causing the n-type to become positively charged while the p-type becomes negatively charged.

We have now created an electric field within the cell.

The insulating properties of silicon allow it to maintain the imbalance. As photons break more electrons free, this electric field will move the electrons along tidily in a flow which becomes an electric current to generate valuable energy.