High work function metal oxides for the hole contact of silicon solar Cells

The applicability of molybdenum, tungsten and vanadium oxide as a hole contact for silicon wafer based solar cells is explored. The Si heterojunctions for which these materials are in direct contact with the c-Si absorber, featuring an additional a-Si:H passivation layer or where these materials are used as an additional contact layer in-between the TCO / a-Si:H(p) Schottky contact are addressed. Compared to the standard TCO / a-Si:H(p) / a-Si:H(i) / c-Si heterojunction an efficiency (1 %abs) and fill factor gain (1.5 %abs) is obtained if a-Si:H(p) is replaced by molybdenum and if tungsten oxide is applied as an additional contact layer at the TCO / a-Si:H(p) contact. For the simple structure without intrinsic and doped a-Si:H and tungsten or vanadium oxide in direct contact to the c-Si absorber, efficiencies comparable to the reference were obtained.