Silicon solar cells Amorphous silicon (a-Si) is a popular solar cell material owing to its low cost and ease of production. Owing to its disordered structure (
Urbach tail), its absorption extends to the energies below the band gap, resulting in a wide-range spectral response; however, it has a relatively low
solar cell efficiency. Protocrystalline Si (pc-Si:H) also has a relatively low absorption near the band gap, owing to its more ordered crystalline structure. Thus, protocrystalline and amorphous silicon can be combined in a tandem solar cell, where the top thin layer of a-Si:H absorbs short-wavelength light whereas the underlying protocrystalline silicon layer absorbs the longer wavelengths == See also ==