Multifunctional Organic Bridge at Self‐Assembled Molecule/Perovskite Interface Enables High‐Performance Inverted Perovskite Solar Cells

Abstract Self‐assembled monolayer (SAM) hole transport layers (HTLs) enable inverted perovskite solar cells (PSCs) to surpass traditional cell designs in power conversion efficiency (PCE). However, simultaneously improving the quality and energy level arrangement of the SAM layer and its interaction with the perovskite layer in the buried interface remains a challenge. Here, a multifunctional interface bridge molecule 2‐bromo‐5‐difluoromethyl‐[1,3,4]thiadiazole (BFS) is chosen and integrated at the buried interface of SAM/perovskite. This bridge optimizes the SAM layer's morphology and energy level structure, and the N atoms in BFS coordinate with Pb ²⁺ in the precursor to regulate perovskite crystallization and passivate defects. Consequently, BFS‐modified PSCs achieve a PCE of 26.16% with a fill factor of 86.06%, compared to 24.49% for the control device. In particular, the strong electron‐withdrawing difluoromethyl group in BFS not only facilitates charge separation and transportation but also forms hydrogen bonds with formamide cation (FA ⁺ ) to improve device stability. The BFS‐based device maintains 90% and 81% of its initial efficiency after being stored in a nitrogen atmosphere for 4000 h and under maximum power point tracking (MPPT) conditions for 500 h, respectively. This study introduces a novel low‐cost SAM/perovskite interface modification strategy, offers valuable insights for the advancement of PSCs.