Synergistic Interface–Bulk Passivation Induced by a Pre-Additive Modifier for Efficient Near-Infrared Perovskite Light-Emitting Diodes

Buried-interface engineering plays a decisive role in determining the performance and operational stability of perovskite light-emitting diodes (PeLEDs), yet most existing strategies focus exclusively on interfacial passivation without regulating defect formation and ion migration in the perovskite bulk. Here, we report a preadditive buried-interface modification strategy based on formamidinium thiocyanate (FASCN) to engineer the ZnO/PEIE/perovskite contact in near-infrared PeLEDs. FASCN forms a stable modification layer at the buried interface, passivating interfacial defects and optimizing energy-level alignment, which leads to improved charge injection and film formation. During perovskite deposition, we further find that FASCN partially dissolves into the perovskite layer and participates in bulk defect regulation, where the thiocyanate anion interacts with Pb2+ ions and suppresses iodide ion migration. As a result, the NIR-PeLEDs achieve a peak external quantum efficiency of 21.1% at 110 mA cm–2 and a half-lifetime of 37.5 h with an initial radiance of 44 W sr–1 m–2, representing a comprehensive improvement over control devices. This work demonstrates an effective route toward simultaneously enhancing efficiency and operational stability in PeLEDs through coupled buried-interface and bulk-defect engineering.