Cadmium telluride solar cells (CdTe) is a special and comparably very efficient type of thin film solar cells.
Structure of CdTe solar cells
Cadmium telluride solar cells are based on cadmium telluride (CdTe) thin film layers as semiconductor to transform absorbed sunlight and generate electricity. In cadmium telluride solar cells, the lower electrode is made from a layer of copper-doped carbon paste while the upper layer is made of tin oxide (SnO2) or cadium-based stannous oxide (Cd2SnO4).
Between the upper layer and the semiconductor cadmium telluride, cadmium sulfide (CdS) is placed.
Composition of thin-film cells. Source: SolarFacts and Advice (HowStuffWorks)
Advantages and disadvantages
Due to its higher cell conversion efficiency - with a 21% record set by First Solar - as compared to amorphous silicon (a-Si) as well as production costs that are far below those of silicon based solar modules, CdTe solar cells are currently one of the mostly employed thin film types and rank only second to crystalline silicon panels.
Due to a sunlight absorption rate that is close to the ideal wavelength, CdTe thin film modules are much more efficient than comparable crystalline silicon produces. Moreover, Cadmium - as a waste and by-product in the mining industry - is a very abundant resource and thus less prone to price fluctuations.
This price advantage is however put into perspective by the relatively high difficulty to procure Tellurium, which is as scarce as gold and thus constraining the market potential of CdTe photovoltaics. Apart from that, CdTe is toxic and solar PV modules using CdTe solar cells are thus bound to restriction stipulated by the EU RoHS and partly China RoHS as well as further restrictions due to the mandatory coverage of solar products and their recycling in the EU's WEEE directive.