Flexibility meets rigidity: a self-assembled monolayer materials strategy for perovskite solar cells.

Self-assembled monolayer (SAM) materials have emerged as promising materials for interface engineering in perovskite solar cells. However, achieving an optimal balance between molecular packing density, charge transport efficiency, and defect passivation remains a challenge. In this work, we propose a SAM material design strategy that synergizes flexible head groups with rigid linking groups. Using (4-(diphenylamino)phenyl)phosphonic acid as a model molecule, Compared to traditional materials such as (4-(9H-carbazol-9-yl)phenyl)phosphonic acid and (4-(diphenylamino)phenethyl)phosphonic acid, our material generates a high-quality perovskite layer. This design achieves superior energy level alignment, improved hole extraction, and enhanced charge transport efficiency, effectively reducing non-radiative recombination. (4-(diphenylamino)phenyl)phosphonic acid-based device achieve power conversion efficiency of 26.21% and 24.49% for small- (0.0715 cm) and large-area (1 cm), respectively. This work establishes an effective approach to SAM molecular design, providing a clear pathway for improving both the efficiency and long-term stability of perovskite solar cells through interface engineering.