The effect of Zn1−xSnxOy buffer layer thickness in 18.0% efficient Cd‐free Cu(In,Ga)Se2 solar cells

The influence of the thickness of atomic layer deposited Zn_1−xSn_xO_y buffer layers and the presence of an intrinsic ZnO layer on the performance of Cu(In,Ga)Se₂ solar cells are investigated. The amorphous Zn_1−xSn_xO_y layer, with a Sn]/(Sn] + Zn]) composition of approximately 0.18, forms a conformal and in‐depth uniform layer with an optical band gap of 3.3 eV. The short circuit current for cells with a Zn_1−xSn_xO_y layer are found to be higher than the short circuit current for CdS buffer reference cells and thickness independent. On the contrary, both the open circuit voltage and the fill factor values obtained are lower than the references and are thickness dependent. A high conversion efficiency of 18.0%, which is comparable with CdS references, is attained for a cell with a Zn_1−xSn_xO_y layer thickness of approximately 13 nm and with an i‐ZnO layer. Copyright © 2012 John Wiley & Sons, Ltd.