The performance and stability of CdS/CdTe solar cells as a function of layer thickness, back contact etch, and oxygen during the CdCl2 anneal was determined. Multiple linear regression models were used to analyze the statistical significance of various first order effects and interactions. With stress, all devices showed a reduction in open-circuit voltage (V-oc) and fill factor (FF) characteristic of increased recombination. Devices using thinner US were vulnerable to shunt formation. Oxygen during the CdCl2 anneal minimizes this effect. A thermodynamic model involving the formation of Cu-oxide is presented to explain the latter. (c) 2006 Elsevier B.V. All rights reserved.