A low electric resistive and stable back contact on p-type CdTe semiconductor is crucial for the commercial employment of high efficiency CdTe thin film solar cell. In this study, V2O5 was deposited as a buffer layer between CdTe and metal electrode in the back contact of CdTe solar cells. Different back contact structures were fabricated on CdTe to study the effect of a V2O5 buffer layer on cell device performance. Both the quantitative band alignment and the device performance of the CdTe solar cells with a V2O5 buffer layer demonstrated that a much lower Schottky barrier was formed compared to the cells with an Au-only back contact. The defect states related to oxygen vacancy within the band gap of the V(2)O(5)played a crucial role in reducing the energy barrier for hole carrier transport. Employing a back contact structure of Cu/V2O5/Cu/Au, a CdTe solar cell with an efficiency as high as 14.0% was fabricated. Long term device stressing test demonstrated that, compared to the CdTe cells with a Cu/Au back electrode, solar cells with the insertion of a V2O5 buffer layer showed much enhanced device stability. (C) 2015 Elsevier B.V. All rights reserved.