CdTe thin film solar cells have shown to be competitive in terms of scalability and efficiency, the latest record efficiency exceeds 22%. Because of the CdTe high electron affinity the insertion of copper has demonstrated to deliver the highest efficiency device, however degrading the cell. For this reason other possible degradation effects are generally neglected. In this work CdTe solar cells were prepared with different transparent conductive oxides (TCOs), delivering similar conversion efficiencies. However aged cells show that stability is strictly connected with the different TCOs. Analysis of capacitance-voltage and drive level capacitance profiling shows a different defects distribution for solar cells with less stable front contact and admittance spectroscopy highlights the different defects formation after aging. (C) 2016 Elsevier B.V. All rights reserved.