Methoxy Functionalization of Phenethylammonium Ligand for Efficient Perovskite Light‐Emitting Diodes

Abstract Although the electroluminescent performances of perovskite light‐emitting diodes (PeLEDs) are continuously improved through defect management strategies, the complicated design of passivation ligands brings great challenges to the rational defect‐annihilation process. Herein, considering the bonding strength with uncoordinated Pb²⁺, the methoxy group with strong electron donating ability is introduced to commonly used phenethylammonium ligand as an efficient additive, namely 4‐methoxy‐phenethylammonium iodide (4‐MeO‐PEAI), to facilitate passivation process in perovskite light‐emitting materials. It is demonstrated that the 4‐MeO‐PEAI agent substantially increases the crystal orientation, enlarges the crystalline grain size, and mitigates the deep‐level trap centers through strong bonding between the methoxy group with unpaired Pb²⁺ ions. The external quantum efficiencyvalue of the PeLEDs with optimized passivation reaches a maximum of 21.6%, with an emission peak of 790 nm. In addition, a nearly threefold increase of the operational half‐lifetime T₅₀ of the 4‐MeO‐PEAI‐mediated devices is observed as compared to the reference sample. Further theoretical calculation results suggest that the adhesion of the ligands on perovskite surface via vacancies leads to an increased dissociation barrier of perovskite; thus, ameliorating the degradation of the PeLEDs under electric field. The findings provide an effective design strategy of the passivation agents to produce high‐performance perovskite‐based optoelectronics devices.