Hydrogen Bonding Enhanced Molecular Assembly of Hole-Selective Contact for Thermally Stable Perovskite Solar Cells

The formation of closely packed and highly ordered self-assembled monolayers (SAMs)-based hole-selective contacts is of paramount importance for achieving durable perovskite solar cells (PSCs). However, conventional molecular design strategies, often centered on extending π-conjugated cores to strengthen π-π stacking, typically encounter a trade-off: excessive π-π interactions can induce molecular aggregation and interfacial instability, thus degrading device stability. In this work, we introduce a hydrogen-bond-enhanced assembly strategy to address this challenge. This concept is realized through two novel dual-anchoring carbazole-based molecules, MeO-CzPACA and MeO-CzPA2, which incorporate an additional anchor onto the ortho-position of the primary phosphonic acid based anchor. The dual-anchor features an intramolecular six-membered hydrogen-bonding motif that stabilizes the deprotonated form in the processing solution, thereby enhancing Brønsted acidity for efficient condensation with hydroxyl-rich metal oxide substrates. Upon assembly on ITO with the primary anchor, the additional anchor groups engage in intermolecular hydrogen bonds that significantly promote intermolecular interactions. Based on this molecular design strategy, the corresponding single-junction and all-perovskite tandem devices achieved champion power conversion efficiencies of 26.9% and 29.6%, respectively. Moreover, the cooperation of intra- and intermolecular hydrogen-bonding interactions results in SAMs with robust structural integrity even at elevated temperatures. This work establishes hydrogen bonding as a powerful stabilization mechanism that complements chemisorption on ITO, offering a promising strategy for developing long-term stable PSCs.