Polycrystalline photovoltaic cell.

A solid object composed of randomly oriented crystalline regions. Polycrystallization occurs when fluid cools rapidly, with crystallization taking place in many seed regions at once. The randomly oriented crystals in a polycrystal affect its properties, e.g. optical ones. A large proportion of photovoltaic cells are polycrystalline because polycrystalline silicon is cheaper than monocrystalline, but they have slightly lower efficiency.