Which one of the following materials is used in photo-voltaic devices in the form of thin films ?
Cadmium telluroide
Thin-film solar cells use a light-absorbing semiconductor layer only a few micrometres thick, deposited on glass or another substrate.
Cadmium telluride (CdTe) is the leading thin-film photovoltaic absorber. It has a direct band gap of about 1.45 eV, close to the ideal value for converting sunlight, and absorbs light strongly, so a very thin layer is sufficient. Commercial CdTe modules are produced on a large scale.
Cadmium sulphide serves only as a thin n-type window or buffer layer paired with CdTe, not as the main absorber. Cadmium oxide is used as a transparent conducting coating, and cadmium sulphate is an ionic salt that is not a photovoltaic semiconductor.
Therefore the material used as the thin-film photovoltaic absorber is cadmium telluride.
Hence, Cadmium telluroide.