CdS/CdTe thin-film solar cells with Cu-free MoO3−x/Au back contacts

The development of high-efficiency CdS/CdTe thin-film solar cells with Cu-free back contacts is an important and challenging issue. In this study, we report on the performance of CdS/CdTe thin-film solar cells with Cu-free MoO_3-x/Au back contacts and standard Cu/Au back contacts. All cells were fabricated on SnO₂:F-coated soda-lime glass substrates with high resistive transparent SnO₂ buffer layers supplied by NSG. The CdS and CdTe layers were deposited by chemical bath deposition and close-spaced sublimation, respectively. The MoO_3-x/Au back contact layers were thermally evaporated after chloride activation. The incorporation of MoO_3-x layer was found to improve the open circuit voltage but reduce fill factor as compared to the cells using sole Au back contacts. We found that the fill factor is very sensitive to the thickness of the MoO₃ layer. With an optimal thickness of MoO_3-x, the best small-area cell (0.08 cm²) has achieved a nearly 13% efficiency under an AM1.5 illumination.