Imidazole Post-Treated Self-Assembled Monolayers for Inverted Perovskite Solar Cells

Inverted perovskite solar cells have emerged as promising candidates for next-generation photovoltaics due to their compatibility with tandem architectures and flexible substrates. A critical factor for high device performance is the optimization of buried interfaces using self-assembled monolayers (SAMs), with Me-4PACz standing out for its excellent charge extraction properties. However, a polarity mismatch between the hydrophobic carbazole terminal and the polar perovskite precursors hinders film coverage and efficient device reproducibility. Here, we report a facile post-treatment strategy employing two chlorinated imidazole derivatives, 4,5-dichloroimidazole (4,5-DI) and 4,5-dichloro-2-methylimidazole (4,5-D-2-MI), at the Me-4PACz/perovskite interface. These molecules enhance carbazole-imidazole interactions, convert the surface from nonpolar to polar, and improve the wettability of the SAM, resulting in an enhanced perovskite morphology. The resulting interfacial dipole modifications alter the work function and reduce the band offset at Me-4PACz/perovskite interface, ultimately enhancing the device fill factor and photovoltage. Ultimately, the target devices delivered an efficiency of approximately 25% with improved long-term stability under varied environmental conditions, highlighting the effectiveness of interfacial engineering via SAM post-treatment for high-performance and durable devices.