Solution-Processed MoO _<i>x</i> Thin Films as Hole-Selective Contacts for Silicon Solar Cells

Molybdenum oxide (MoOx) has emerged as a promising material to be used as hole-selective contacts in silicon solar cells due to its high work function. However, the poor thermal stability of the MoOx layer prepared by thermal evaporation remains a bottleneck for its industrial adoption. In this study, we investigate the hole selectivity and thermal stability of MoOx films prepared by solution deposition in combination with different capping layers. It is found that solution-deposited MoOx films, with an optimized capping layer, provide better surface passivation and improved thermal stability compared to thermally evaporated MoOx on both n-type and p-type silicon substrates. A carrier lifetime up to τeff = 740 μs can be achieved for solution-deposited MoOx, but the bare MoOx film exhibits poor thermal stability. With the addition of an indium-oxide-based capping layer, enhanced thermal stability can be achieved with a lifetime of τeff > 400 μs maintained up to 300 °C. However, the surface passivation advantages provided by solution MoOx come at the cost of higher specific contact resistivity ρc ≈0.3 Ω cm2, which is still low enough to be used in full-area solar cell contacts. These results highlight the potential of solution processing as an alternative approach to form high-quality hole-selective contacts, possibly overcoming the thermal stability challenges of evaporated MoOx.