The SiLEAN project is advancing alternatives to traditional silicon-based thin-film layers in silicon heterojunction (SHJ) solar cells. These efforts aim to reduce parasitic absorption, improve transparency, and ultimately enhance the efficiency of next-generation SHJ devices while keeping material use sustainable and scalable.
One line of research focuses on Transparent Passivating Contacts (TPCs). This architecture combines an ultra-thin (< 1.5 nm) silicon tunnel oxide (SiOx) layer, fabricated by a wet-chemical process, with hydrogenated nanocrystalline silicon carbide (nc-SiC:H(n)) layers grown via hot-wire chemical vapor deposition (HWCVD). Through stepwise optimization of process parameters, researchers at Forschungszentrum Jülich achieved highly homogeneous and efficient passivation on industrially relevant wafers. Laboratory-scale TPC solar cells demonstrated an increased short-circuit current density of up to 40.0 mA/cm², about 0.6 mA/cm² higher than conventional SHJ reference cells. The next steps will include optimization of passivation properties and the application of this approach to full M2+ size solar cells on high-quality epitaxially grown wafers.
See the extract from the report here
In parallel, project partner TU Delft is also investigating Transition Metal Oxides (TMOs) as alternatives to doped silicon-based thin films on the illuminated side of SHJ solar cells. These layers—particularly molybdenum oxide (MoOx)—offer excellent transparency and effective hole selectivity due to their high work function. Using thermal evaporation, MoOx-based SHJ solar cells achieved a power conversion efficiency of 23.94% on 4-inch wafers with compatible tools, and 22.03% on wafers processed with M2-compatible tools that reflect industrial conditions. Early tests with sputtered MoOx layers also delivered promising results, reaching up to 21.60% efficiency with optimized plasma treatments to minimize interface damage.
See the extract from the report here
Together, these advances illustrate the potential of novel passivating and contact layer concepts to overcome current efficiency limitations in SHJ solar technology.
