Optimization of a rear system based on Titanium Nitride for a flexible CuInSe2 solar cell

•The good crystallization of CISe deposited onto glass at 550 °C. The gap value is in good agreement with the literature.•The CISe layers deposited on Inox 316 exhibits a bad crystallization and stoichiometry.•The high deposition temperature of CISe promotes the diffusion of metallic impurities from Inox 316 to the absorbent layer.•The TiN / Ti bilayer improves the surface condition of the Inox 316 substrate.•The TiN / Ti decrease the diffusion of iron from 9.7 % to 1.9 % and Cr from 3.8 % to 0.5 %.