Closing the Gaps: Multifunctional Molecular Filling for Highly Efficient and Stable Inverted Perovskite Solar Cells

Abstract

Self-assembled monolayers (SAMs) have shown exceptional promise as hole-transport layers (HTLs) in inverted perovskite solar cells (PSCs). Nevertheless, their typically incomplete surface coverage creates pathways for interfacial charge recombination, which compromises device performance. Herein, we introduce chloromethyltrichlorosilane (CMS) as a multifunctional molecular filler that simultaneously addresses two critical challenges of incomplete SAM coverage and interfacial ion migration. The highly reactive trichlorosilane groups readily chemisorb onto residual hydroxyl groups on the transparent conductive oxide (TCO) surface, effectively “closing the gaps” in the SAM layer, thereby suppressing interfacial charge recombination. Meanwhile, the chloromethyl terminal groups coordinate with the perovskite components, enhancing perovskite crystallization and passivating surface defects. As a result, CMS-modified devices achieved a power conversion efficiency (PCE) of 26.85% via the two-step fabrication—the highest reported to date for this method—and a similarly impressive 26.71% via the one-step approach, demonstrating the strategy’s broad universality. Beyond efficiency, the multifunctional modification anchors the HTL more robustly to the substrate and establishes a potent barrier against ion migration. Consequently, the unencapsulated devices exhibited exceptional long-term durability, retaining more than 98% of their initial efficiency after aging at 85 °C for 1200 hours and 96% after 1200 hours of maximum power point tracking. This work demonstrates that multifunctional molecular engineering at the buried interface offers a powerful strategy to simultaneously enhance efficiency and stability of inverted PSCs.