Comparison of ZnO:B and ZnO:Al layers for Cu(In,Ga)Se2 submodules

• Direct comparison between Cu(In,Ga)Se2 sub-modules employing ZnO:B and ZnO:Al.
• Higher current density and conversion efficiency in the ZnO:B module
• Lower parasitic absorption owing to free carriers in the ZnO:B module.
• Comparable series resistance between the ZnO:B and ZnO:Al modules

B-doped ZnO (ZnO:B) films with improved visible and near-infrared transparency have been applied as transparent conductive oxide (TCO) electrodes in Cu(In,Ga)Se2 submodules. The use of ZnO:B instead of conventional Al-doped ZnO (ZnO:Al) improved the short-circuit current density (Jsc) and the resulting conversion efficiency without decreasing the fill factor. The detailed optical and electrical analysis of the modules revealed that (i) the improvement in Jsc was due to lower parasitic absorption owing to free carriers in the TCO layer and (ii) the series resistance of the ZnO:B module originating from the TCO and TCO/Mo contacts is comparable to that of the ZnO:Al module.