Sulfur-Modulated Fully-Conjugated Self-Assembled Monolayers for Synergistic Dual-Interface Optimization in Inverted...

To achieve high efficiency and stability in inverted perovskite solar cells (PSCs), it is essential to ensure uniform self-assembled monolayers (SAM) coverage on the substrate and to passivate defects effectively at the buried interface of perovskite. Herein, two sulfur-modulated fully-conjugated SAMs, 4-(bis(4-methylthiophenyl)amino)phenylphosphonic acid (SMe-TPA-PA) and 5-(4-bis(4-methylthiophenyl)amino)phenyl) thiophenylphosphonic acid (SMe-TPA-ThPA) are developed for inverted PSCs by employing substituent regulation and linker adjustment. The incorporation of methylthio substituents in both SAMs enhances their defect-passivation capability at the interface. Moreover, the thiophene linker in SMe-TPA-ThPA strengthens intermolecular interactions, improves energy level alignment with the perovskite, enables stable and uniform molecular coverage on ITO, and facilitates efficient hole extraction. As a result of synergistic dual-interface modification of the ITO/perovskite system, inverted PSCs based on SMe-TPA-ThPA and SMe-TPA-PA achieve significantly improved power conversion efficiencies (PCEs) of 26.52% and 25.40%, respectively, surpassing the control device based on methoxyl-substituted SAM (OMe-TPA-PA, 24.31%). Remarkably, devices incorporating SMe-TPA-ThPA also exhibit exceptional operational stability, retaining 91.8% of their initial PCE after 1700 h of continuous light soaking and 91.2% after 1700 h of continuous thermal aging at 65 °C.