What is the difference between Monocrystalline, Polycrystalline, and Thin Film Solar Panels?

With all the different types of solar panels out there, it can be confusing determining which type of panel is best. Here is a brief rundown of the types:

Monocrystalline: A monocrystalline cell (AKA: Single Crystal Cell) is the most efficient of the available panel types. The type of silicon cell is determined by the process in which they are created. A silicon ingot is drawn slowly from a molten vat, using a process called the Czochralski method. This is what makes the silicon monocrystalline.  Without getting into too much chemistry, an almost perfect lattice is formed on the atomic level which allows the electrons to pass through with little or no interference, giving the mono cells the highest efficiency. Once the ingot is formed, it is sliced into a series of thin wafers which are the substrate of the solar cell.  Mono panels typically have an efficiency of 15-17%.  The highest of efficiency monocrystalline panels readily available to the public is about 20%. The main downside is due to the process of manufacturing the wafers, the cost can be expensive.

Polycrystalline: Similar to mono’s, polycrystalline cells are still made from silicon, but the process differs. Instead of the long, arduous, expensive process of creating a single crystal solar cell (where the ingot is drawn slowly from a vat), the molten silicon is poured into a cast and cooled with a seed crystal (a piece of crystalline material used to grow a larger crystal).  Unlike the mono atomic structure, the casting method doesnt create uniform lattices, hence bringing the overall efficiency down. Polycrystalline panels are typically 12-14% efficient.

Amorphous/Thin Film: Thin Film solar panels are the least efficient of the 3 types, coming in anywhere from 6-8%. The panels are made using a CVD process (chemical vapor deposition). The silicon is deposited typically on glass, however the atomic lattice structure is anything but organized. While this leads to better performance in low light and higher ambient temperatures, it also greatly reduces the cell efficiency.

So, you should always buy mono right? Am I wasting my money with lower efficiency panels?
NO. This is the biggest misconception in the solar industry. $/watt is $/watt. That’s it.  While you may need almost twice the space for a thin film array to get the same wattage of a monocrystalline array, the cost per watt is what really matters.

If I buy a 20,000W solar system, and i pay $1.00/watt for the panels, i am getting 20,000W of power for $20,000. It doesn’t matter if its thin film, mono, or poly. You are getting the exact same amount of power. The only difference will be the physical size of the array.

What would I recommend:
Buy what works best for your situation. If you have the space and money is an issue, buy the best available deals out there right now (we currently have poly/mono/thin film panels  all under $.60/watt). Really you’re paying for watts of power, that’s it.

I would also mention that thin film really should be lumped in its own category as its efficiency and cost is usually much lower than mono/poly. The difference between mono and poly in my opinion is negligible and can almost always be substituted for one another unless you are literally counting the millimeters and watts for your array. Thin film is ideal for low cost systems with no space limitations.

Adam Loucks
Electrical Engineer

Posted in Solar Learning Center.

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