Regulating Crystal Orientation via Ligand Anchoring Enables Efficient Wide‐Bandgap Perovskite Solar Cells and Tandems

Abstract Wide‐bandgap (WBG) perovskite solar cells have attracted considerable interest for their potential applications in tandem solar cells. However, the predominant obstacles impeding their widespread adoption are substantial open‐circuit voltage (V_OC) deficit and severe photo‐induced halide segregation. To tackle these challenges, a crystal orientation regulation strategy by introducing dodecyl‐benzene‐sulfonic‐acid as an additive in perovskite precursors is proposed. This method significantly promotes the desired crystal orientation, passivates defects, and mitigates photo‐induced halide phase segregation in perovskite films, leading to substantially reduced nonradiative recombination, minimized V_OC deficits, and enhanced operational stability of the devices. The resulting 1.66 eV bandgap methylamine‐free perovskite solar cells achieve a remarkable power conversion efficiency (PCE) of 22.40% (certified at 21.97%), with the smallest V_OC deficit recorded at 0.39 V. Furthermore, the fabricated semitransparent WBG devices exhibit a competitive PCE of 20.13%. Consequently, four‐terminal tandem cells comprising WBG perovskite top cells and 1.25 eV bandgap perovskite bottom cells showcase an impressive PCE of 28.06% (stabilized 27.92%), demonstrating great potential for efficient multijunction tandem solar cell applications.