Perovskite Solar Cells on Polymer-Coated Smooth and Rough Steel Substrates

Fabricating efficient perovskite solar cells on steel substrates could enable easy building integration of this photovoltaic technology. Herein, an n–i–p perovskite solar cell is developed on steel substrates for top illumination. The optimized stack uses a Ti bottom electrode, covered with an indium tin oxide (ITO) interlayer and a SnO₂ electron transport layer passivated by [6,6]-phenyl-C₆₁-butyric acid. The active layer is a triple-cation perovskite. A thermally evaporated tris(4-carbazoyl-9-ylphenyl)amine)/MoO₃ bilayer acts as hole transport layer. The transparent top contact consists of ITO with a MgF₂ antireflective coating. Optical analysis shows small parasitic absorption and reflectance losses for this stack, which provides 15.9% power conversion efficiency when fabricated on glass. On steel, covered with a polyamide imide planarization coating to moderate the surface roughness (R _p), the highest efficiency is 15.2% for high-gloss steel (R _p≈ 200 nm), 14.9% for battery steel (R _p≈ 500 nm), 14.2% for packaging steel (R _p≈ 1500 nm), and 13.8% for construction steel (R _p≈ 2500 nm). While the short-circuit current density and open-circuit voltage are invariant, the fill factor decreases with increasing R _p due to increasing series resistance and decreasing shunt resistance. The yield of working devices remain high, also for the roughest substrates.