Co‐Assembly with Donor‐Acceptor Self‐Assembled Monolayers to Enhance Interfacial Hole Extraction, Wettability, and Crystallization in Inverted Perovskite Solar Cells

ABSTRACT Self‐assembled monolayers (SAMs) are commonly employed as hole‐selective layers in inverted perovskite solar cells. However, the widely used Me‐4PACz (Me4) often faces issues such as solution aggregation, poor precursor wettability, insufficient interfacial contact, and suboptimal crystallinity at the perovskite buried interface, leading to non‐radiative losses. This study proposes two newly designed donor‐acceptor (D‐A) SAMs, LYS‐H and its fluorinated derivative LYS‐F , and employs a co‐assembly strategy with Me4 to overcome these limitations. The D‐A structure enhances interfacial dipole moments to facilitate hole extraction, while distinct functional groups enable effective passivation at the perovskite buried interface. Additionally, the multi‐directional phenyl rings of the triphenylamine (TPA) group in LYS‐H and LYS‐F can interact with the carbazole units of Me4 via π–π stacking. This interaction helps suppress Me4 aggregation and enhances the uniformity of SAM. This approach simultaneously improves precursor wettability and promotes enhanced perovskite crystallinity. Compared to LYS‐H , fluorination of LYS‐F deepens its highest occupied molecular orbital (HOMO) and increases its effective work function, enabling better alignment with the perovskite valence band. The Me4+ LYS‐F ‐based device demonstrates superior interfacial energy level alignment and reduced interface defects, ultimately achieving a power conversion efficiency of 25.02% and a high fill factor of 83.64%. Furthermore, both unencapsulated Me4+ LYS‐H and Me4+ LYS‐F devices demonstrate substantially improved operational stability compared to the pristine Me4 device, when measured in air (RH ≈ 30%) under dark conditions at 25 °C.