Simulation of ZnMgO as the window layer for CdTe Solar Cells

CdS has been used as window layer for CdTe solar cells during the last decades of years. New wider band gap (Eg) materials is being found to replace CdS in order to remove blue loss so that short-circuit current (JSC) of CdTe solar cells can be significantly increased. ZnMgO, synthesized by incorporating Mg content into ZnO, is one of the potential candidates. Some researchers have already successfully made high efficiency CdTe solar cells using ZnMgO. In this work, ZnMgO is used as the window layer and systematic computer simulation is finished to investigate the influence of the resistivity (R) of ZnMgO and the conduction band offset (∆EC) between ZnMgO layer and CdTe layer on the performance of CdTe solar cells. Simulation results indicate that low resistivity and high doping is needed for ZnMgO and the influence of conduction band offset is quite different when the doping concentration of ZnMgO varies. +0.2eV is an acceptable value for conduction band offset and the ideal Mg content in ZnMgO is around 10%. Finally, a new optimized CdTe solar cell with highest efficiency is designed and a flat band diagram is plotted. Index Terms — CdTe solar cells, window layer, ZnMgO, resistivity, conduction band offset.