Fabrication of Si trench solar cells with improved radiation hardness for space applications

Mono-crystalline silicon (Si) space solar cells were fabricated with deep holes (0.5-0.7 × substrate thickness) etched into a standard p-doped Si substrate by a high etch rate plasma apparatus. After the etch an n⁺ emitter diffusion is done inside and outside of the holes followed by cleaning and thermal passivation. The cells have been electron irradiated by a 1 MeV radiation with different doses up to 3 10¹⁵ cm^-2 and the cell efficiency η, the short circuit current I_sc and the open circuit voltage V_oc have been measured before and after radiation and compared to a Si reference cell. The fabrication process of the trench cell has been kept fully compatible with standard Si cell processing