Transparent WOx window layers for silicon based heterojunction solar cells

The fabrication of window layers more transparent than those based on amorphous silicon (a-Si:H) could be a key factor to enhance the efficiency of heterojunction (HJ) solar cells. In this work amorphous hydrogenated silicon oxide (a-SiO x :H) as a transparent passivating layer and substoichiometric tungsten oxide (WO x ), with its wide band gap and high work function, are proposed to form efficient hole-selective contacts on silicon-based HJ solar cells. A comparison is made between WO x films grown by RF sputtering and by thermal evaporation.