Europium(ii) complexes with substituted triethylenetetramine: new emitters to construct efficient deep blue organic light emitting diodes by spin coating

Abstract

Organic light-emitting diodes (OLEDs) have demonstrated commercial success in displays and lighting. However, deep blue OLEDs are still the bottleneck due to the lack of efficient luminescent materials. Benefiting from short excited-state lifetimes and tunable emission colors, luminescent Eu(II) complexes with characteristic 5d–4f transitions are promising emitters in OLEDs. Herein, three Eu(II) complexes with substituted triethylenetetramine are designed and synthesized. By adjusting the steric hindrance of ligands, these Eu(II) complexes exhibit blue and deep blue emissions with narrow full width at half maximums ranging from 31 to 36 nm and high photoluminescence quantum yields of up to 97%. Spin-coated OLEDs were further fabricated, and the optimized deep-blue emitting device shows a maximum external quantum efficiency of 4.7%, a maximum luminance of 1307 cd m⁻² and a Commission Internationale de l’Eclairage coordinate of (0.13, 0.08).