Photoconductive Lifetime of CdS Used in Thin-Film Solar Cells

Thin-film CdS is used as a window layer in most of the current thin-film polycrystalline device technologies including absorbers based on cadmium telluride (CdTe) and copper indium selenide (CIS) and copper indium gallium selenide (CIGS). Device performance has been linked to the deposition technique and posttreatment of the CdS layer. Here we used the radio frequency photoconductive decay (RFPCD) technique to measure the photoconductive lifetime of CdS that had been deposited by various techniques. This includes chemical bath deposition (CBD) and laser deposition. CdCl2 treatment increases the photoconductive response and reduces shallow trapping effects. In addition, tellurium doping was found to significantly decrease the photoconductive response, as well as the hole lifetime, below that of the undoped material. The impact of these CdS properties on device performance will be discussed.