Dipole-Moment-Tuned Self-Assembled Monolayers for Efficient Perovskite Solar Cells

Self-assembled monolayers (SAMs) serving as hole transport layers (HTLs) have greatly boosted the advances in efficient perovskite solar cells (PSCs). Nevertheless, the poor wettability and adsorbability, nonuniform coverage, and defects at the buried substrate-perovskite limit the further improvement of device performance. Herein, we propose an interfacial engineering strategy by incorporating 2-fluorobenzene-1,3-dicarboxylic acid (m-FBC) into the SAM layer. Leveraging the high dipole moment of m-FBC, the energy levels are effectively aligned, thereby reducing the charge-transport energy barrier. This modification concurrently enhances surface wettability and mitigates electronic inhomogeneity at the interface. As a result, the prepared PSCs with m-FBC modification achieved a high PCE of 25.03%, indicating a substantial improvement compared to the PCE (23.05%) of the controlled device. Furthermore, the optimized devices showed long-term stability, retaining 94% of their initial efficiency after 500 h of storage. This work not only provides a promising strategy for the design of multifunctional hole transport layer but also offers valuable insights into the structure-property relationships of SAMs in inverted PSCs.