Stable Self‐Assembled Monolayers Anchoring and Enhanced Antireflection in Four‐Terminal Perovskite/Silicon Tandem Solar Cells via a VO x ‐NiO x Composite Contact

ABSTRACT Self‐assembled monolayers (SAMs) have significantly boosted the power conversion efficiency (PCE) of perovskite solar cells (PSCs), but fragile interfacial anchoring has substantially limited their operational stability. To improve SAM anchoring, NiO x is widely used as the underlying platform. However, NiO x surfaces that favor strong binding are typically more oxidized and hydroxyl‐rich, which can also raise parasitic absorption and interfacial losses and becomes particularly critical for semitransparent and four‐terminal tandem devices. Here, a VO x ‐NiO x composite hole‐transporting architecture by integrating hydroxyl‐rich VO x nanoclusters with a compact NiO x overlayer is developed. This composite interface provides dense and chemically uniform reactive sites for robust SAM anchoring while preserving favorable energetic alignment for hole extraction and suppressing reflection and parasitic absorption. As a result, 0.148 cm 2 semitransparent PSCs with a bandgap of 1.67 eV deliver PCEs of 21.68% and retain 98% of the initial efficiency after 1472 h of one‐sun maximum power point tracking at 25°C and 90% after 1000 h of dark aging at 85°C. Integrated in four‐terminal perovskite/silicon tandems, a PCE of 31.25% is achieved on 1 cm 2 devices. By decoupling anchoring from optical losses, this work offers a scalable interface design principle for perovskite tandem photovoltaics.