Solvation‐Driven Grain Boundary Passivation Improving the Performance of Perovskite Solar Cells

Abstract The efficiency of perovskite solar cells (PSCs) is hindered by substantial defects within the grain boundaries (GBs) of polycrystalline perovskite films. Conventional post‐treatment strategies struggle to precisely repair these defects at GBs. Here, a targeted grain boundary passivation strategy through solvent effects by incorporating symmetrical biphenyl molecules is proposed, 4,4′‐diaminodiphenyl sulfone (DDS) and 4,4′‐sulfodiphenol (SDP), aiming to mitigate defects at GBs and optimize energy level arrangements through their electric dipole effects. Compared to the pristine device, the SDP‐modified device exhibits significant improvements, including a champion efficiency of 24.39% and an impressive fill factor, along with excellent operation stability. This work provides an effective and straightforward solution for improving the performance of PSCs.