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 (V-OC) 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 V-OC of 815mV 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 V-OC of 844mV, 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. Copyright (c) 2013 John Wiley & Sons, Ltd.