IZO or IOH Window Layers Combined with Zn(O,S) and CdS Buffers for Cu(In,Ga)Se2 Solar Cells.

CdS and Zn(O,S) grown by chemical bath deposition are well-established buffer materials for Cu(In,Ga)Se₂ (CIGS) thin-film solar cells and modules. Typically these buffers were combined with a ZnO:Al (AZO) or ZnO:B window layer and i-ZnO or (Zn,Mg)O as high-resistive interlayer. Nowadays, alternative transparent conductive oxide (TCO) materials with higher mobility as compared to AZO like indium zinc oxide (IZO) and hydrogen-doped indium oxide (IOH) are under investigation. In the present contribution, we report on the performance of CIGS cells with solution-grown Zn(O,S) or CdS buffer layers in combination with different stacking sequences including i-ZnO, (Zn,Mg)O, IZO, and IOH. Devices with the commonly used AZO window layer are used as references. Efficiencies above 16% without anti-reflective coating (ARC) are achieved for cells with Zn(O,S)/(Zn,Mg)O combined with IZO, IOH, and AZO whereas poor results are obvious with all Zn(O,S)/i-ZnO combinations. Nevertheless, CdS-buffered reference cells with the different TCO materials exhibit efficiencies in the range of 17-18% without ARC mainly due to higher open-circuit voltages. [ABSTRACT FROM AUTHOR]