All-Vacuum Engineering of SnO₂-Based Buried Interfaces for Scalable and Thermally Stable Perovskite Photovoltaics

Closing the gap between lab-scale efficiency and module-scale reliability is critical for the commercialization of perovskite photovoltaics. However, scaling up aggravates spatial heterogeneity, interfacial energetic disorder, and thermomechanical degradation, particularly at vacuum-deposited oxide/perovskite junctions. Here, we report an all-vacuum engineering strategy for SnO₂-based buried interfaces that addresses both optoelectronic and thermomechanical losses in scalable perovskite photovoltaics. In situ Eu co-sputtering within a magnetron-sputtered SnO₂ framework regulates oxygen-vacancy chemistry and homogenizes the interfacial energetic landscape, thereby promoting more efficient electron extraction. Building on this, bifacial modules achieve power conversion efficiencies of 17.85% at the 6 × 6 cm² scale and 17.39% at a 175 cm² aperture area, while the 6 × 6 cm² modules retain 90.2% of their initial efficiency after 2000 h of maximum-power-point tracking under ISOS-L-3 conditions. Opaque devices with Au top electrodes further reach 19.89%, supporting the effectiveness of this buried-interface strategy across different electrode configurations. After further introducing an evaporated ultrathin KCl interlayer, the initial efficiency is largely preserved, while buried interfacial strain under thermal stress is relieved and thermal-cycling durability is improved, with 88.9% retention after 200 ISOS-LT-3 cycles. This work establishes all-vacuum buried-interface engineering as a practical route toward scalable and thermally stable perovskite photovoltaics.