A Dual‐Site Molecule‐Engineered Hole‐Transporting Layer: Boosting Efficiency in Both Perovskite and Non‐Fullerene Organic Solar Cells

ABSTRACT Nickel oxide (NiO x ) with self‐assembled monolayers (SAMs) has been widely used as a hole‐transporting layer (HTL) for efficient p‐i‐n perovskite solar cells (PSCs), while suffering from inhomogeneous interfacial contact due to weak anchoring. In this study, we report a dual‐site ligand engineering strategy using amino acid‐derived molecules (denoted as DAB and DAB SH ) to modify the NiO x nanoparticles. Theoretical results and characterizations reveal that the additional thiol groups effectively suppress NiO x aggregation, enhance film uniformity, and regulate the Ni 3+ /Ni 2+ ratio to enhance conductivity. Simultaneously, the hydroxyl and carboxyl groups of the ligands promote dense and stable SAM assembly through hydrogen‐bonding interactions. Under these circumstances, the homogeneous NiO x /SAM HTL enables the growth of high‐quality perovskite films with large grains, reduced defect density, and negligible residual stress. As a result, the DAB SH molecule‐engineered p‐i‐n PSCs yields a champion efficiency of 26.82%, together with enhanced device operational stability. Notably, this dual‐site molecule‐engineered HTL is also compatible with non‐fullerene organic solar cells, delivering a best efficiency of 20.16%, providing a versatile platform for interfacial engineering toward high‐performing perovskite and organic optoelectronic applications.