Heteroatom substitution and molecular configuration engineering in self-assembled materials for high-efficiency and stable perovskite solar cells

Abstract

The strategies of heteroatomic substitution and configuration modulation in self-assembled materials (SAMs) are promising to advance perovskite solar cells (PSCs). Herein, we developed a novel β-position thiophene-substituted SAM (β-Th-2PACz) as a hole-selective layer (HSL) for inverted PSCs. Compared with the conventional carbazole-based SAM (2PACz) and its α-thiophene-based counterpart (α-Th-2PACz), β-Th-2PACz exhibited a reduced π-conjugation and an “outward” sulfur orientation, which mitigated self-agglomeration, enhanced interfacial interactions, and optimized energy alignment. Theoretical and experimental analyses revealed that β-Th-2PACz achieved superior surface coverage, reduced defect density, and a robust buried interface. Consequently, the β-Th-2PACz-based device achieved a champion power conversion efficiency (PCE) of 24.34%, outperforming 2PACz (22.79%) and α-Th-2PACz (20.97%). Benefitting from the optimized buried interface, an unencapsulated device retained 88% of its initial PCE after storing for 1200 hours in ambient air. Our work not only reveals the structural–property–performance relationship of these heteroatom-substituted SAMs but also provides guidance for the molecular design of highly efficient SAMs.