Stable Energy‐Level Regulation of NiO x for Efficient Deep‐Blue Perovskite LEDs

ABSTRACT NiO x offers tunable energy‐level via interfacial molecular modification, making it a promising hole injection layer for perovskite light‐emitting diodes (PeLEDs). However, conventional modifiers often detach during perovskite deposition, reverting energy‐level to the intrinsic state. While simply enhancing electron‐withdrawing strength can improve anchoring, it causes excessive energy‐level shifts. Here, we employ a multidentate anchoring strategy to enhance modifier adsorption stability on NiO x , preventing the regulated energy‐level from shifting back. These interactions correspondingly provide multiple charge‐transfer pathways, which effectively disperse the charge density and thereby mitigate the localized strong electron transfer that causes excessive energy‐level modulation. Specifically, tridentate anchor 4‐bromophenylphosphonic acid (BPA) engages in multiple Ni‐O coordination bonds, achieving a high adsorption strength of −6.47 eV and retaining over 95% surface‐coverage after polar solvent rinsing. Concurrently, multiple charge‐transfer pathways effectively distribute the electron‐withdrawing effect of ─PO 3 H 2 group, yielding favorable energy‐level alignment with a small barrier of less than 0.69 eV. We integrate this strengthened NiO x with pure‐halide quasi‐2D perovskites to fabricate deep‐blue PeLEDs. The obtained PeLEDs exhibit a champion external quantum efficiency (EQE) of 15.8% at 463 nm and a record‐low turn‐on voltage of 2.4 V. This approach also enables large‐area (3 × 3 cm 2 ) PeLEDs fabrication, with an EQE of 11.2%.