Aromatic interaction-driven out-of-plane orientation for inverted perovskite solar cells with improved efficiency

Formamidinium and caesium metal halide perovskites enable high efficiency in inverted perovskite solar cells, but uncontrolled crystallization limits their performance. Here we regulate the nucleation and growth of the perovskite through aromatic interactions between naphthalene ammonium salts and naphthalenesulfonates. The ammonium groups of the naphthalene ammonium salts occupy the formamidinium site, while the sulfonate groups of the naphthalenesulfonates coordinate with lead ions. Their naphthalene moieties form tight aromatic stacking adjacent to the [PbI₆]⁴⁻ octahedra. These interactions promote ordered out-of-plane crystallization along the (100) plane, enhancing defect passivation and carrier transport. We achieve a power conversion efficiency of 27.02% (certified 26.88%) for inverted solar cells. Encapsulated devices retain 98.2% of their initial efficiency after 2,000 h of maximum power point tracking under continuous illumination in ambient air. Furthermore, we demonstrate a certified steady-state efficiency of 23.18% for inverted mini-modules with an aperture area of 11.09 cm² and a certified efficiency of 29.07% for all-perovskite tandem solar cells.