Essig, S.; Dréon, J.; Rucavado, E.; Mews, M.; Koida, T.; Boccard, M.; Werner, J.; Geissbühler, J.; Löper, P.; Morales-Masis, M.; Korte, L.; de Wolf, S.; Ballif, C.: Toward Annealing-Stable Molybdenum-Oxide-Based Hole-Selective Contacts For Silicon Photovoltaics. Solar RRL 2 (2018), p. 1700227/1-5
10.1002/solr.201700227
Open Accesn Version

Abstract:
Molybdenum oxide (MoOX) combines a high work function with broadband optical transparency. Sandwiched between a hydrogenated intrinsic amorphous silicon passivation layer and a transparent conductive oxide, this material allows a highly efficient hole-selective front contact stack for crystalline silicon solar cells. However, hole extraction from the Si wafer and transport through this stack degrades upon annealing at 190°C, which is needed to cure the screen-printed Ag metallization applied to typical Si solar cells. Here, we show that effusion of hydrogen from the adjacent layers is a likely cause for this degradation, highlighting the need for hydrogen-lean passivation layers when using such metal-oxide-based carrier-selective contacts. Pre-MoOX-deposition annealing of the passivating a-Si:H layer is shown to be a straightforward approach to manufacturing MoOX-based devices with high fill factors using screen-printed metallization cured at 190°C.