The typical monocrystalline solar cell is a dark black colour, and the corners of cells are usually missing as a result of the production process and the physical nature of monocrystalline silicon. Polycrystalline, on the other hand, is identifieable by its signature light or dark blue colour, but not uniformly so: some patches are lighter than others. The differences in appearance come about as a result of the manufacturing process.
Chemical Definition: This type of Silicon has an ordered crystal structure, with each atom ideally lying in a pre-ordained position and exhibits predictable and uniform behaviour. What-that-means: This type of Silicon goes through several cycles of slow and energy intensive filtration and separation processes and thus is the most expensive type of silicon.
Interesting point: These cells are usually created in a circular shape or a ‘square-without-corners’. This is because, when they are grown from an ingot, the only way to create high purity crystal structures is to extruded the molten liquid and gravity does the rest with respect to creating a cylindrical block out of which the smaller cells are cut. Usually manufacturers will leave cells in a circular shape however due to advances in recycling, the cells are being chopped into squares-without-corners to maximize the packing density of the modules.