Carboxyl/Phosphoryl Synergistic‐Functionalized Self‐Assembled Monolayer for Strengthening Interface Contact for Efficient Inverted Perovskite Solar Cells

The close interfacial contact between NiO x and self‐assembled monolayers (SAM) is crucial for enhancing the efficiency and stability of inverted perovskite solar cells (PSCs). The commonly used phosphonic acid‐based SAMs as the interfacial layer on NiO x have proven effective in improving photovoltaic performance of PSCs, but poor wetting and heterogeneous distribution of SAMs give rise to unwanted interfacial losses and thus limiting further enhancement of the device performance. Herein, a carboxyl/phosphoryl synergistic‐functionalized SAM by incorporating 4‐pyrazolecarboxylic acid (4‐PCA) into self‐assembled [4‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl) butyl] phosphonic acid (Me‐4PACz), is proposed. The carboxyl groups of 4‐PCA coabsorbed with Me‐4PACz on NiO x are discovered to effectively fill the molecular vacancies retained in Me‐4PACz SAM through bidentate coordination, forming a compact and homogeneous 4‐PCA/Me‐4PACz SAM. Such SAM significantly strengthens the NiO x /perovskite interfacial contact, thereby promoting oriented perovskite crystallization, accelerating hole extraction, and reducing nonradiative recombination. As a result, the inverted PSCs based on the 4‐PCA/Me‐4PACz SAM achieve a power conversion efficiency of 23.84%, which outperforms the control device with Me‐4PACz SAM (21.47%). Additionally, the device retaining 90.8% of their initial efficiency after 1000 h of storage in ambient air (25%–50% relative humidity) without encapsulation, highlighting improved interfacial integrity and device durability.