Rational Tailoring of Hole-Selective Self-Assembly Monolayers Based on Sulfur-Containing Heterocycles for...

Conventional hole‑selective self‑assembled monolayers (SAMs) for perovskite solar cells (PSCs) have largely focused on tuning electronic properties while neglecting their roles as crystallization templates and defect passivators. We address this by replacing unstable Lewis‑basic thioalkyl groups with sulfur‑containing heterocycles (thiophene derivatives) in a carbazole‑based SAM framework. Two novel non‑centrosymmetric SAMs, TP, and BTP, are synthesized; BTP, with an extended conjugated scaffold, exhibits reduced sulfur electron density, superior stability, and stronger intermolecular C-H···π and S···π interactions. These properties enable dense, ordered assembly on ITO, enhancing hole mobility, built‑in potential, and wettability. BTP also passivates undercoordinated Pb²⁺ ions at the buried interface via Lewis acid-base interactions, reducing trap density and non‑radiative recombination. The champion inverted PSC achieves 26.85% efficiency with a fill factor of 86.67% and retains 96% of initial efficiency after 1100 h at 65 °C. This work presents a molecular engineering strategy that simultaneously optimizes electronic properties, interfacial assembly, and defect passivation for high‑performance, stable PSCs.