An In Situ Crosslinked Disulfide Self‐Assembled Monolayer for Concurrent Defects Modulation and Perovskite Self‐Healing for Stable Photovoltaics

ABSTRACT Carbon‐based hole‑transport‑layer‑free perovskite solar cells (C‐PSCs) have attracted significant attention due to their low manufacturing costs and great potential for enhanced stability. However, the severe interfacial non‐radiative recombination caused by hydroxyl groups on the SnO 2 electron transport layer surface, along with the intrinsic degradation of perovskite under operational conditions, adversely affects device performance. This work proposes a multifunctional interfacial modification strategy based on bis‐[3‐(triethoxysilyl)propyl]‐disulfide (TESPD), a molecule featuring both siloxane and disulfide motifs. Through hydrolysis and condensation on the SnO 2 surface, followed by in situ cross‐linking of their multiple terminal silane groups, the molecules form a robust 3D covalent network, thereby forming a stable self‐assembled monolayer (SAM). This stable interlayer not only passivates surface ─OH defects on SnO 2 to suppress charge recombination but also repairs the perovskite lattice via its disulfide bond (S─S) as a redox mediator, converting Pb 0 and I 0 defects back into Pb 2+ and I − for in situ self‐healing. Utilizing this “static passivation–dynamic repair” synergy, the target device displays remarkable long‐term operational stability by retaining over 90% of its initial efficiency over 630 h of continuous 1‐sun illumination at 25°C in a N 2 atmosphere. This work provides a reliable interfacial engineering strategy for efficient and stable C‐PSCs.