Europium(II) Complexes with Substituted Tris(2‐aminoethyl)amine/Triethanolamine Ligand and their Application in Blue Spin‐Coated Organic Light‐Emitting Diodes

Abstract Luminescent Eu(II) complexes with characteristic d–f transitions have potential applications in many fields, especially organic light‐emitting diodes (OLEDs), due to their satisfactory advantages including short excited‐state lifetimes, 100% theoretical exciton utilization efficiency and tunable emission colors. Up to now, most light‐emitting layers in OLEDs are typically fabricated through high‐vacuum thermal evaporation process, which is uneconomical for large‐area and multi‐dopant devices. In this work, eight Eu(II) complexes with substituted tris(2‐aminoethyl)amine or triethanolamine ligands are designed and synthesized, and their structural and photophysical properties are studied. These complexes exhibit tunable maximum emission wavelengths in the range of 437–553 nm and high photoluminescence quantum yields up to 75%. Furthermore, this work demonstrates the application of Eu(II) complex in solution‐processed OLEDs with high efficiency and luminance for the first time. The optimized device show a maximum external quantum efficiency of 9.2% and a maximum luminance of 1780 cd m⁻² with an emission peak at 485 nm.