Influence of a-Si:H/ITO Interface Properties on Performance of Heterojunction Solar Cells☆

Abstract In this study, we focus on the influence of the contact properties between Indium Tin oxide (ITO) and hydrogenated amorphous Silicon (a-Si:H) on the performance of a-Si:H/c-Si HeteroJunction (HJ) solar cells. We experimentally found that an increase of the (p) a-Si:H layer thickness can improve the open-circuit voltage (Voc) but also and especially the Fill-Factor (FF) of the cell. Thanks to simulation we propose an explanation of this unexpected increase. The deposition of ITO with low effective workfunction on (p) a-Si:H actually leads to a depletion of the emitter of the cell, which results in an increase of its effective activation energy and of its resistance affecting Voc and FF. Thanks to this new insight we give guidelines which can help to further optimize the HJ front stack.