Investigation of thin Poly-Si/SiOx passivated contacts p-type silicon cells radiation hardness

Standard satellites photovoltaic arrays (PVA) are powered with III-V multi-junction cells. These cells, three orders of magnitude more expensive than silicon cells, count for about one third of the PVA cost. In parallel, crystalline-silicon (c-Si) modules for the terrestrial market experienced outstanding price reductions, with prices currently around 0.2 _/Wp, and have reached industrial maturity over the last decades. This significant cost gap combined with the huge photovoltaic volume required by the growing Low Earth Orbit (LEO) constellations (orders of magnitude above actual III-V market) call for a re-assessment of Si photovoltaics for space. Within this context, understanding Si radiation hardness through the prism of modern cell materials and passivated contact architectures appears as a key issue. In this work, we focus more precisely on polycrystalline silicon (Poly-Si) on tunnel oxide passivated contacts Si cells (i.e. Poly-Si/SiOx) since they allow premium efficiencies and represent a growing fraction of the terrestrial PV technology share. CEA has developed an innovative cell architecture for terrestrial applications, relying on poly-Si/SiOx stacks integrated on both the front and rear Si wafer surfaces. To avoid parasitic front side light absorption, ultra-thin poly-Si layers (6-15 nm) are used in combination with transparent conductive oxide. Initially developed on thick n-type substrates, the first cells results on p-type Ga-doped wafers, with thicknesses down to 60 mu m and resistivity up to 20 Ohm.cm, are presented here. The radiation hardness of these ultra-thin passivated contacts cells is studied by 1 MeV electrons irradiation.