Solar PV is praised for its generation of renewable energy. Whilst many of us understand the basics that they use sunlight, let’s get to grips with the silicon science behind the generation of electricity in PV panels.
Solar PV panels consist of silicon cells, a metal case, glass and wires (sometimes companies may use a different element instead of silicon although for the sake of this blog, I will stick with Silicon – which is most popular).
Silicon is a metalloid which means it lies between being a metal and a non-metal.
It is semi-conductive meaning it has both conductive and insulative properties which is largely due to its atomic structure which has four electrons in its outer shell (also called an ‘orbital’) that have covalent bonds (shared) with other silicon atoms (Figure 1).
As a result of the covalent bonds, silicon is a stable atom which doesn’t allow electricity to flow easily.
Therefore, to enable the flow of an electrical current, silicon is ‘doped’ with two other elements which are typically Phosphorus and Boron to create a ‘silicon cell’.
The doping elements are located above and below silicon in the Periodic Table. Boron has one less electron than silicon and phosphorus has an additional electron than silicon.
If you are a little nerdy like me, here is some additional information about the two additional elements:
- Phosphorus: known as the ‘N-type’ (negative charge) provides a free roaming electron to the silicon lattice which creates a negative charge.
- Boron: known as the ‘p-type’ (positive charge) only three electrons in its outer shell which creates ‘holes’ in the silicon lattice which creates a positive charge.
The two elements are sandwiched around the silicon creating a positive-negative (P-N) junction which enables the movement of an electric current (Figure 2).
An electric current is generated when sunlight (photons) excite the silicon cells causing the movement of free roaming electrons in the silicon cells.
In effect, the more sunlight your silicon cells receive, the more electricity will be generated!
Although, the efficiency of electricity generated is limited by temperature as temperatures too hot and too cold can reduce the total output of the panels.
How about in Layman Terms?
For those of you who are not science nerds and skipped the above part, no worries let me explain how PV panels make electricity in the simplest way possible and see Figure 3 for a simplistic overview of how a PV panel works.
- Energy from the sun interacts with a PV panel
- The sun’s energy facilitates the flow of an electrical current within the PV panel
- This electricity is then directed from your PV panel into your home which you can use to power your appliances.
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