Effect of window layer composition in Cd1-xZnxS/CdTe solar cells

To improve CdS/CdTe cell/module efficiencies, CdS window layer thinning is commonly applied despite the risk of increased pin-hole defects and shunting. An alternative approach is to widen the band gap of the window layer (2.42eV for CdS) via alloying, for example, by forming compositions of Cd1-xZnxS. In this study, the performance of Cd1-xZnxS/CdTe thin-film solar cells has been studied as a function of x (from x=0 to 0.9), widening the window layer band gap up to and over 3.4eV. Optimum Cd1-xZnxS compositions were clearly identified to be around x=0.7, and limitations to the achievable photocurrent and conversion efficiencies have been addressed. Copyright (c) 2012 John Wiley & Sons, Ltd.