Imide‐Based Molecular Passivation Enables Efficient Wide‐Bandgap Perovskite and Perovskite/Silicon Tandem Solar Cells

ABSTRACT Wide‐bandgap perovskite absorbers are essential for achieving high‐efficiency perovskite/silicon tandem solar cells. However, in p‐i‐n architectures, their inherent strong p ‐type (or weak n ‐type) characteristics hinder electron extraction, causing significant open‐circuit voltage ( V _OC ) deficits. To address these challenges, we developed 3‐phthalimidopropanoic acid (DPA). This molecular passivation material leverages the electron‐deficient properties of its phthalimide core. DPA delivers three synergistic effects: it acts as an interface dipole layer to precisely align surface energy levels, enhance the surface n ‐type characteristics, and boost quasi‐Fermi level splitting (QFLS); it forms a gradient distribution during anti‐solvent processing to modulate crystallization kinetics, improve film morphology, and minimize defects; and it achieves carboxyl‐group chelation of undercoordinated Pb ²⁺ to effectively passivate surface and bulk traps, thereby significantly enhancing device stability. Consequently, a DPA‐modified wide‐bandgap (1.68 eV) perovskite solar cell achieves an efficiency of 22.91%. Moreover, a two‐terminal perovskite‐silicon tandem solar cell delivers an efficiency of 31.66%. This approach provides a robust strategy for efficient and stable tandem photovoltaics, advancing n ‐type interface engineering.