Tailored Lattice-Matched Carbazole Self-Assembled Molecule for Efficient and Stable Perovskite Solar Cells

Self-assembled monolayer molecules have been widely employed as interfacial transport materials in inverted perovskite solar cells (PSCs), demonstrating high efficiency and improved device stability. However, self-assembling monolayer (SAM) molecules often suffer from aggregation and weak interactions with the perovskite layer, resulting in inefficient charge transfer and significant energy losses, ultimately limiting the power conversion efficiency and long-term stability of perovskite solar cells. In this work, we developed a series of novel skeleton-matching carbazole isomer SAMs based on the following key design principles: (1) introducing a benzene ring structure to distort the molecular skeleton of the SAM, thereby preventing aggregation and achieving a uniform distribution on fluorine-doped tin oxide (FTO) substrates; (2) strategically incorporating methoxy groups onto the benzene ring at different positions (ortho, meta, and para). These functional groups not only increase anchoring points with the perovskite layer but also fine-tune the molecular dipole moment. Among the SAMs, m-PhPACz exhibits the most favorable properties, with a maximum dipole moment of 2.4 D and an O–O distance that aligns excellently with the diagonal lead ions in the adjacent perovskite lattice, thereby enhancing SAM–perovskite interactions, facilitating efficient charge extraction, and improving interfacial stability. As a result, the new SAM-based PSCs achieved an impressive power conversion efficiency of 26.2%, with 12.9% improvement. Moreover, the devices demonstrated outstanding photothermal stability, retaining 96% of their initial PCE after 1000 h at 85 °C and maintaining 90% of their initial PCE after 300 h of UV-light exposure.