Effects of oxygen plasma treatment on the performance of CdTe thin-film solar cells

CdTe solar cell devices are a promising technology, but they still have room for improvement before the theoretical efficiency of 30% is reached. In this study, we fabricate CdTe devices using close space sublimation to deposit CdTe and chemical bath deposition for the CdS layer. We explore the effects of oxygen plasma treatment on both the F-doped SnO2 (FTO) layer of commercial glass substrates and the CdS layer before depositing the CdTe absorber layer. While plasma cleaning the FTO results in a marked improvement in conversion, treating the CdS layer further improves performance. X-ray diffraction and scanning electron microscopy show no distinct changes in morphology on the CdS layer as a result of the plasma treatment. It is anticipated that plasma treatment induces a drastic reduction in the amount of organics on the substrates and modifies the chemistry of the surface of CdS layers; which may account for the observed performance improvements.