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

The performance of sputtered CdS/CdTe solar cells with MoO 3− x /Au contacts was examined. The cells were fabricated on Pilkington SnO 2 :F-coated soda-lime glass with a high resistivity transparent SnO 2 buffer layer. The MoO 3- x /Au back contact layers were deposited by thermal evaporation. The incorporation of the MoO 3− x layer was found to improve the open circuit voltage ( V OC ) but reduce the fill factor (FF) of the sputtered CdS/CdTe cells. While V OC is not sensitive to the thickness of the MoO 3 layer, FF is very sensitive. The optimal thickness for the MoO 3 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.