Now that we’ve got a basic understanding of electricity, let’s dive into something that’s super important for solar panels (and modern tech in general): semiconductors.
What Are Semiconductors?
You probably know what a conductor is—materials like copper and aluminum that allow electricity to flow easily because of all those free-moving electrons.
And then there are insulators, like rubber, that stop electricity dead in its tracks by holding on tightly to their electrons.
So, where do semiconductors fit in?
Well, as the name suggests, semiconductors are materials that fall somewhere in between conductors and insulators.
They can conduct electricity, but not as well as metals, and they can block electricity, but not as efficiently as insulators.
Basically, they’re a bit of both—a “halfway house” for electricity flow.
But here’s the cool part: we can control when and how semiconductors conduct electricity.
And this ability to switch between conducting and insulating is what makes semiconductors so special.
Why Are Semiconductors So Special?
1. Valence Electrons
Semiconductor materials, like silicon, have exactly 4 valence electrons in their outer shell.
Why is that important?
Think of those 4 valence electrons as being at a crossroads.
They’re not too tightly bound to the atom like in an insulator (where it’s almost impossible to pull them away), but they’re also not freely floating around like in a conductor.
It’s like these electrons are sitting on the fence, waiting for a little push to decide whether they’ll stay put or break free and start conducting electricity.
This “fence-sitting” behavior is what makes semiconductors so unique.
With the right conditions—like adding a small amount of energy (more on that later)—we can give those 4 valence electrons the nudge they need to move and carry a current.
And voilà!
Now we have a material that can flip between acting like an insulator and a conductor.
This ability to control the flow of electrons is exactly why semiconductors are used in everything from solar panels to smartphones. They give us the power to make electricity flow when we need it and stop it when we don’t.
Pretty cool, right?
Well, it’s not as cool as the next property.
2. Crystalline Structure
Remember in the previous section when we talked about how atoms like to be stable?
Well, here’s the thing: silicon atoms, with their 4 valence electrons, aren’t quite there yet. They are most stable when their outer has 8 electrons, so they need 4 more electrons to reach this point.
But instead of trying to steal or give away electrons, silicon does something interesting—it shares its electrons with neighboring atoms.
This sharing of electrons forms covalent bonds.
So, each silicon atom “shares” its 4 valence electrons with 4 neighboring silicon atoms.
In return, it also “borrows” 1 electron from each neighbor.
This means that every silicon atom now feels like it has 8 electrons in its outer shell—4 of its own and 4 shared.
This electron sharing forms a crystalline structure—a perfectly ordered grid where every atom is tightly bound to its neighbors.
In this state, silicon is stable and happy, with a full outer shell of electrons.
3. Doping
So far, we’ve talked about how semiconductors, like silicon, form stable crystalline structures by sharing electrons with their neighbors.
But in this pure form, silicon isn’t all that great at conducting electricity. Sure, it can conduct a little, but it’s like trying to get a spark from a wet match—it’s not exactly efficient.
That’s where doping comes in. And no, we’re not talking about athletes cheating in the Olympics.
In the world of semiconductors, doping is the process of adding a tiny bit of another element to supercharge the material and change how it behaves.
For example, each silicon atom has 4 valence electrons that can bond with 4 other atoms.
Now, what do you think would happen if we added an element like phosphorus (P) that has 5 valence electrons to our material?
Exactly!
Each Phosphorous atom will bind with 4 Silicon atoms, leaving 1 electron to move around freely.
This is called an N-type semiconductor. It works by doping a small amount of a material with more than 4 valence electrons to increase the number of free electrons.
Now, let’s see what happens when we dope the material with an element like Boron (B), which has only 3 valence electrons.
Since Boron has fewer electrons than Silicon, it can only bond with 3 neighboring silicon atoms, leaving one bond unfilled.
This creates what we call a “hole.”
This hole acts like a positive charge. In other words, it acts like a magnet, attracting nearby electrons from other atoms.
When an electron from a neighboring atom moves into the hole, it fills it, essentially completing the bond.
But here’s the interesting part: the electron that moved to fill this hole leaves behind another hole, let’s call it hole 2, in the atom it came from.
Now, hole 2 acts just like the first one—it behaves like a positive charge, attracting another electron (electron 2) from a nearby atom to fill it.
And when electron 2 moves to fill hole 2, it leaves behind yet another hole, and the process continues.
This chain reaction of electrons filling holes creates the appearance that the holes are moving through the material, even though it’s actually the electrons doing the hopping. This movement of holes is what allows P-type semiconductors to conduct electricity.
