CdS/CdTe thin‐film solar cells with Cu‐free transition metal oxide/Au back contacts

Superstrate CdS/CdTe thin‐film solar cells with Cu‐free transition metal oxide (TMO)/Au and Au‐only back contacts have been fabricated. The TMOs include MoO3‐x, V2O5‐x, and WO3‐x. The incorporation of the TMO buffer layers at the back contacts resulted in significant improvement on open‐circuit voltage (VOC) as compared with the cells with Cu‐free Au‐only back contacts. Among the cells using TMO buffer layers, the ones with MoO3‐x buffer layers exhibited the best performance, yielding an efficiency of 14.1% under AM1.5 illumination with VOC of 815 mV and a fill factor of 67.9%. Though the performance is slightly behind the best reference cell with a Cu/Au back contact fabricated in our lab with VOC of 844 mV, fill factor of 76.3%, and efficiency of 15.7%, the use of Cu‐free back contacts may lead to improved long‐term cell stability.