semi-metallic chemical element, atomic weight of 14, an extensively used semiconductor material, a common constituent of sand and quartz in the form of an oxide, and commonly used in PV cells

NOTE 1 Silicon crystallises in a face-centred cubic lattice like a diamond

NOTE 2 The terms here are applied to materials, wafers, cells, and modules

a) amorphous silicon

(Symbol: a-Si, a-Si:H)

hydrogenated non-crystalline silicon alloy in a semi-stable condition deposited on a foreign substrate with a thickness of the order of 1 µm

b) crystalline silicon

(Symbol: c-Si)

general category of silicon materials exhibiting a crystalline structure, i.e., showing long range ordering of the silicon atoms

c) microcrystalline silicon

(Symbol: µc-Si)

hydrogenated silicon alloy deposited on a foreign substrate with a thickness of the order of 1 µm presenting grains < 1 µm of crystalline structure

d) multicrystalline silicon

(Symbol: mc-Si)

silicon material that has solidified at such a rate that many large grain single crystals (called crystallites, and ranging from 1 mm to 10 mm) are formed

NOTE 3 The atoms of each crystallite are symmetrically arrayed, but the multitude of crystallites is randomly jumbled

NOTE 4 Often moulded as a cast ingot or pulled ribbon

e) polycrystalline silicon

(Symbol: pc-Si)

silicon material deposited on a foreign substrate as a layer with a thickness of 10 µm to 30 µm and a grain size of 1 µm to 1 mm

NOTE 5 Polycrystalline silicon is known as thin film pc-Si

NOTE 6 Polycrystalline silicon is also a term used in the feedstock silicon fabrication process

f) single crystalline silicon

(Symbol: sc-Si)

silicon material characterized by an orderly and periodic arrangement of atoms such that it has only one crystal orientation: i.e., all of the atoms are symmetrically arrayed

NOTE 7 Single crystalline silicon is known as mono-crystalline and single crystal

g) solar photovoltaic grade silicon

(Abbreviation: SOG)

feedstock material with a high chemical purity adapted to the growth of crystalline silicon ingots