I hope you found the Basics of Solar power – Part I useful. Please feel free to pop in and leave a comment or a question – here on this blog or let’s talk on Google+, Facebook or Twitter. In this part of the series, we are going to see what solar cells are made of.
(Image of Silicon: Wikimedia)
What is solar cell made of?
Solar cells are made of a semiconductor material, typically silicon. Silicon is the second most abundant element on earth, first one being oxygen. It is a metalloid, an element which displays properties that are both like a metal and a non-metal. Pure silicon however can neither conduct well nor insulate well, hence it needs to be doped.
What is doping?
Doping is a process in which impurities are added to increase or decrease the number of electrons. In other words, doping is a process of adding elements which can either donate or withdraw electrons from silicon. This process causes either excess of electrons or electron deficiency in the silicon material. When an element with 5 valence electrons is added to a silicon that naturally has 4 valence electrons, it becomes n-type (more electrons). When an element with 3 valence electrons is added to it, it becomes p-type (less electrons or more holes). These are known as pentavalent and trivalent impurities respectively.
Is silicon the only material used for making solar cells?
Apart from silicon, gallium arsenide (GaAs); cadmium telluride (CdTe) and copper indium gallium selenide (CIGS) are also used. One also needs to know that solar panels are wrapped in a safety glass and given an anti-reflection coating for better and longer performance. So, these materials too are a crucial part of the entire solar panel system. A hunt for new materials continues to achieve greater efficiencies. Not just for solar cells but also for anti-reflection coatings.
Let us now focus on silicon as the material of construction.
Kinds of silicon:
Solar cells are made of three kinds of silicon:
How do I know which one is the best?
The choice for the kind of silicon depends on various factors such as:
Geography: The place you are going to assemble the solar panels at determines the choice of the panel. This is because each of these materials reacts differently to climatic conditions.
Type of application: Will it be placed on a building or your car? Amorphous panels take up a lot of space and hence cannot be used on a car. These are the ones you can see on calculators.
Efficiency: Monocrystalline panels have the highest efficiency of them all.
Durability: Monocrystalline panels live longest.
Budget: Monocrystalline panels are the most expensive.
Researchers are trying to discover and invent new materials that are cheaper and more efficient. They are also working on engineering techniques for modulating existing materials because each one of them has its own beauty. Keep an eye on the third part of this series to know more about new findings!
See you soon!
This blog post was first published at GreenHatters on March 6, 2014. Version edited for minor corrections. It’s a part of a series on solar power fundamentals.
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