[Technology] What is silicon semi-conductor and its impact on solar industry?
Sillicon the second most abundant material
Silicon is the second most abundant material on Earth (after oxygen) and the most common semiconductor that is used in electronic devices, cars, medical devices, planes and the list is long…
To summarize:
The silicon semi-conductor: you don’t buy it directly, but you really need it
Silicon is found in soil and rock, but it’s also contained in natural water, trees and plants. In nature, however, it is found in the form of compounds with Oxygen, Aluminum and Magnesium. As a result, the Silicon element must be extracted from the compound and purified. To do so, we need a high temperature (around 2000 C°) and a very sophisticated process.
But how do we produce this needed energy? Do renewable energy are sufficient for such an extremely high temperature? I will not dig deeper into it in this article but just to give you an idea, the majority of silicon semiconductor are created with the help of nuclear energy.
Let’s come back to our second most abundant material in our planet. In order to make a semi-conductor from it, we need a very sophisticated process and only few countries master this technic.
But what is the physical properties of the semi-conductor and why it is so important?
It’s benefit far outweigh the cost of its production, but I’ll just list one important feature:
It can behave as a conductor under certain condition but also as an insulator under other condition.
Before talking about the silicon semiconductor used in solar cells, I’ll do brief introduction on electricity and how it is generated. Don’t worry you don’t need to be technical to understand.
Electricity is nothing but the movement of the electrons from one point to another, as simple as that. And remember this: when an electron moves from one point to another, he leaves a “hole”.
If we do the analogy with hydraulics, the intensity of electricity (measured by the unit Ampère) is the flow of water. And the tension (measured with volts) is the pressure of the water.
Let’s come back to our silicon semi-conductor on solar cells:
A photovoltaic cell must have two types of semiconductors in layers. The n-type semiconductor is doped with a very small amount of an element containing an extra valence electron. The idea is to have a layer with extra electrons that can move freely.
The p-type semiconductor is doped with an element with one fewer valence electrons and the reason behind is to have the other layer with extra “holes” that can catch those free electrons.
When put together in a pn junction, an electric field forms at the junction that biases the flow of electrons and holes to opposite directions.
Congratulation, you now know the science behind the photovoltaic effect!
Summary:
During this article I tried to introduce the silicon semi-conductor, where we find it? how it is made? Where do we use it? And why it is so important.
Solar cell is one of the industries where we use this semi-conductor and every small impact on it will affect the solar panel market. But do we have other material more efficient and less complex in their production that we can use instead?
Brace yourself because this will be the subject of my next article…
