Thin-film solar cells are a type of made by depositing one or more thin layers ( or TFs) of material onto a substrate, such as glass, plastic or metal. Thin-film solar cells are typically a few nanometers () to a few microns () thick–much thinner than the used in conventional (c-Si) based solar cells, which can be up to 200 μm thick. Thin-film solar cells are commercially used in several technologies, including (.