Mono means one while poly means many - just as in romantic relationships.
But what do they mean in terms of solar panels?
The difference starts during the process of creation. Monocrystalline silicon is created by slowly pulling a monocrystalline silicon seed crystal out of melted monocrystalline silicon using the Czochralski method to form an ingot of silicon. A seed crystal is a small piece of silicon which is used as a foundation for the molten molecules. By having a foundation, the molten molecules are able to connect together faster to form an ingot. While the seed crystal is being withdrawn, it is rotated slowly and temperature is lowered slowly. This helps form the cylindrical shape until it has the right diameter which is when temperature remains constant.
Polycrystalline silicon is made through a simpler method. Instead of going through the slow and more expensive process of creating a single crystal, molten silicon is just put into a cast and cooled with a seed crystal. By using the casting method, the crystal surrounding the seed isn’t uniform and branches into many, smaller crystals, thus "polycrystalline".
If the videos above, posted by youtube user globalchampion, are more information than required, here are the bullet point differences between the two methods:
Monocrystalline solar cells cost more than polycrystalline for the same size.
Monocrystalline cells have a higher efficiency than polycrystalline cells due to the structure being made from one large crystal as opposed to many small ones. In addition to having an overall better efficiency, monocrystalline panels can perform up to 10% better than polycrystalline panels in high ambient temperatures.
Since monocrystalline panels are more efficient per area, the size of the solar panel is less than a polycrystalline solar panel for the same wattage. If you are limited on size and want to get the most energy possible, monocrystalline panels are the better choice.
In terms of looks, monocrystalline panels have a nice uniform color and have a more circular cell shape. Polycrystalline cells are in squares and have inconsistencies in the color sort of like granite.
Even though a monocrystalline panel has the potential to last up to 50 years, most warranties only go up to 25 years which polycrystalline panels are able to reach just fine.
Overall, the production process for monocrystalline silicon is mature, and the process for polycrystalline in still maturing. As purity and process tolerances for polycrystalline Si improves, the performance gaps between the two are narrowing.
Take a look at our monocrystalline panels.
Take a look at our polycrystalline panels.