Evaluation of ZnSnO buffer layers for CuIn0.5Ga0.5Se₂ solar cells

Thin ZnSnO films are evaluated as new buffer layer material for Cu(In,Ga)Se 2 ‐based solar cell devices. A maximum conversion efficiency of 13.8% ( V oc = 691 mV, J sc (QE) = 27.9 mA/cm 2 , and FF = 71.6%) is reached for a solar cell using the ZnSnO buffer layer which is comparable to the efficiency of 13.5% ( V oc = 706 mV, J sc (QE) = 26.3 mA/cm 2 , and FF = 72.9%) for a cell using the standard reference CdS buffer layer. The open circuit voltage ( V oc ) and the fill factor (FF) are found to increase with increasing tin content until an optimum in both parameters is reached for Sn/(Zn + Sn) values around 0.3–0.4.