Beyond Solution Processing: Vacuum Evaporation of Carbazole‐Phosphonic Self‐Assembled Molecules Enables Flexible Perovskite Solar Cells with >25.4% Efficiency

Abstract High‐quality and uniform self‐assembled molecule (SAM) films are critical for the controllable fabrication of high‐performance inverted flexible perovskite solar cells (F‐PSCs). However, solution‐processed SAMs suffer from poor surface coverage and inadequate chemical anchoring on conducting substrates, especially for flexible substrates with high roughness, compromising the charge transport efficiency and device stability. Herein, we introduce thermal evaporation for depositing carbazole‐phosphonic SAM films and establish the correlations between molecular configurations and surface properties. Vacuum‐evaporated SAMs exhibit enhanced substrate coverage and surface wettability compared to solution‐processed counterparts through the regulated molecular packing. The increased surface energy of vacuum‐evaporated SAM films accelerates perovskite nucleation kinetics, balances growth rates across the films, and optimizes interfacial contact quality. Molecular configuration tailoring in the SAM backbones further refines the morphological quality and energetic alignment at the buried interface, thus promoting efficient charge transport and reduced non‐radiative recombination loss. As a result, the optimized devices using vacuum‐evaporated SAM films achieve an impressive power conversion efficiency (PCE) of 25.47% (certified 25.38%), among the highest PCEs reported for F‐PSCs. Furthermore, the optimized devices demonstrate enhanced mechanical durability and operational stability, underscoring a practical methodology route toward efficient and stable F‐PSCs.