Sputtered CdS/CdTe solar cells with MoO3−x/Au back contacts

The performance of sputtered CdS/CdTe solar cells with MoO3−x/Au contacts was examined. The cells were fabricated on Pilkington SnO2:F-coated soda-lime glass with a high resistivity transparent SnO2 buffer layer. The MoO3-x/Au back contact layers were deposited by thermal evaporation. The incorporation of the MoO3−x layer was found to improve the open circuit voltage (VOC) but reduce the fill factor (FF) of the sputtered CdS/CdTe cells. While VOC is not sensitive to the thickness of the MoO3 layer, FF is very sensitive. The optimal thickness for the MoO3 layer is found to be 2–5 nm, which yields nearly 12% efficiency. The performance of these CdS/CdTe solar cells was further evaluated under thermal stress at 200 °C in controlled environments. We found that the cells degraded significantly under thermal stress in air, due to the increase of series resistance or decrease of FF.