polysilicon (poly-Si)
polycrystalline silicon
multicrystalline silicon → πολυκρυσταλλικó πυρíτιο, πολυπυρίτιο
Polycrystalline silicon, or multicrystalline silicon, also called polysilicon or poly-Si, is a high purity, polycrystalline form of silicon, used as a raw material by the solar photovoltaic and electronics industry.
Polycrystalline silicon - Wikipedia