The silicon used to make mono-crystalline solar cells (also called single crystal cells) is cut from one large crystal. This means that the internal structure is highly ordered and it is easy for electrons to move through it. The silicon crystals are produced by slowly drawing a rod upwards out of a pool of molten silicon.
Each cell will also have a uniform pattern as all of the crystals are facing the same way. Mono-crystalline silicon solar cells are the most efficient type of solar cells, however they are also the most expensive due to the technology involved in making large highly uniform silicon crystals.
Polycrystalline solar cells use liquid silicon as raw material. Since the polycrystalline silicon involves solidification process the materials contain various crystalline sizes. Hence, the efficiency of this type of cell is less than Mono crystalline solar cell. Efficiency of this type of solar cell is 13-15 %.
Elements allowing the silicon to exhibit n-type or p-type properties are mixed into the molten silicon before crystallization. You can identify mono-crystalline solar cells by the empty space in their corners where the edge of the crystal column was.
Since the Mono crystalline silicon is pure and defect free, the efficiency of cell is higher. Efficiency of this type of solar cell is 14-17 %. Polycrystalline solar cells use liquid silicon as raw material. Since the polycrystalline silicon involves solidification process the materials contain various crystalline sizes.
During the past few decades, crystalline silicon solar cells are mainly applied on the utilization of solar energy in large scale, which are mainly classified into three types, i.e., mono-crystalline silicon, multi-crystalline silicon and thin film, respectively .