Tellurides as back contacts for substrate CdTe thin film solar cells on flexible foil substrates

The formation of a low resistance ohmic contact on p-type CdTe is a significant challenge for the superstrate solar cell configuration, where surface preparation techniques including wet etches are often used in order to modify the surface of CdTe prior to applying the contact material(s). It is even a greater challenge for the less commonly used substrate configuration, since the p-contact/CdTe interface will be formed first and will be exposed to the remaining solar cell fabrication steps. This paper presents results on the properties of two tellurides and their performance as back contacts in substrate type CdTe solar cells fabricated on flexible foil substrates. Solar cell efficiency is limited by the properties of the back contact and is currently in the 6.0-6.5% range.