Analysis of heterointerface recombination by Zn1 xMgxO for window layer of Cu(In,Ga)Se2 solar cells

An adjustment of a conduction band offset (CBO) of a window/absorber heterointerface is important for high efficiency Cu(In,Ga)Se2 (CIGS) solar cells. In this study, the heterointerface recombination was characterized by the reduction of the thickness of a CdS layer and the adjustment of a CBO value by a Zn1 xMgxO (ZMO) layer. In ZnO/CdS/CIGS solar cells, open-circuit voltage (Voc) and shunt resistance (Rsh) decreased with reducing the CdS thickness. In constant, significant reductions of Voc and Rsh were not observed in ZMO/ CdS/CIGS solar cells. With decreasing the CdS thickness, the CBO of (ZnO or ZMO)/CIGS become dominant for recombination. Also, the dominant mechanisms of recombination of the CIGS solar cells are discussed by the estimation of an activation energy obtained from temperature-dependent current–voltage measurements. 2008 Elsevier Ltd. All rights reserved.