Superstrate design for increased CdS/CdTe solar cell efficiencies

James W. McCamy1, Zhixun Ma1, Jason M. Kephart2, Russell M. Geisthardt2, W.S. Sampath2, Victor V. Plotnikov3, Alvin Compaan3 1PPG Industries, Cheswick, PA, United States /2Colorado State University, Fort Collins, CO, United States /3Lucintech, Inc., Toledo, OH, United States

The optical and electrical properties of the glass superstrate and window layer materials play critical roles in the performance of CdTe photovoltaic devices.  The compositional modifications made to tailor the transmission spectra in these materials so as to maximize the Jsc of the device will be reviewed.  Progress towards improving the electrical characteristics (e.g., carrier mobility) of the transparent conductive oxides as well as materials design to improve the interface behavior at the window layer will be presented.  Recent results showing the impact of these changes on achieving thinner CdS window layers and improved device performance in devices made by both thermal and energetic deposition methods will be discussed.