CdTe polycrystalline thin film solar cells have shown an immense potential in scalability, up to now this is the sole thin film technology that has reached its maturity for industrial production, by the amazing results in terms of market and efficiency of First Solar that is ranked among the top ten solar modules manufacturers .
These modules have demonstrated long-term stable performance and high efficiency up to 22% under AM1.5 illumination . Amongst several attractive features, high chemical stability of CdTe and a simple compound formation are the most important ones for large area production of solar modules.
For this reason high efficiency devices can be obtained with a large variety of fabrication processes such as vacuum evaporation (15,6% from EMPA, CH) , sputtering (14% by University of Toledo, USA) , screen printing (10% from Matsushita) , close space sublimation (16.7% from NREL)  and vapour transport deposition (22% from First Solar) .
Further simplifications have been introduced recently like substituting the CdCl2 (carcinogenic) annealing step with a recrystallization treatment obtained by MgCl2 deposition  and annealing or treatment with Chlorine containing gases .
A lot has been discussed about the presence of cadmium in the finished product; this has been universally accepted as a perception issue more than a real problem since the thin film architecture allows an extremely low amount of cadmium (in a 60x120cm module there is less Cd than in a AA battery) and stored in an inert, non toxic compound . Moreover CdTe modules have performed the lowest environmental impact and the lowest pay back time .
Recent works on stable back contact have demonstrated that it is possible to produce devices with a remarkable stability versus time and with an additional higher performance in low light irradiation or high temperature conditions .
Moreover, there are new promising device configurations like bifacial solar cells , ultra-thin solar cells   and flexible devices . The highest efficiencies in CdTe solar cells have been obtained using CSS deposition methods, requiring a high substrate temperature (500÷550 °C). Instead, conventional physical vapor deposition (PVD) process where CdTe is evaporated in a vacuum evaporation (VE) system at lower substrate temperatures (typically 300°C) has provided solar cells with efficiencies of more than 15%. For these reasons VE process is attractive for a very simple in-line deposition of large area CdTe solar modules on soda-lime glass substrates, as well as on polymer foils thereby facilitating the roll-to-roll manufacturing of flexible solar modules .
Flexible CdTe/CdS solar cells of 14% efficiency in superstrate and 12% efficiency in substrate configurations have been developed . Flexible superstrate solar cells have been directly grown on commercially available polyimide foils or ultra thin glass.
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