Drastic performance enhancement by using a WOx buffer before ZnO back reflector in amorphous silicon solar cells fabricated at 121 degrees C

Abstract

We report on drastic performance improvement by inserting amorphous tungsten oxide (WOx) with a wide optical band gap at the n-type amorphous silicon (n-a-Si)/zinc oxide (ZnO) back reflector interface in a-Si-based solar cells fabricated at 121 degrees C. We found that a 3-nm-thick WOx film could remarkably reduce the defect density at the n-a-Si/ZnO interface, resulting in decreased series and increased shunt resistances. Consequently, the fill factor and conversion efficiency could be markedly enhanced by 8.6% and 9.2%, respectively. A maximum efficiency of 8.05% was obtained. This technique may be applied to all kinds of thin-film solar cells.