Highly improved electroluminescence from double-layer devices based on a carbazole-functionalized europium3+ complex

Abstract

A novel europium complex Eu(TTA)3(CPPO)2 (1) (TTA=thenoyltrifluoroacetone, CPPO=9-[4-(diphenyl-phosphinoyl)-phenyl]-9H-carbazole) based on the phosphine oxide ligand with bipolar structure was used to fabricate double-layer devices. The strong hole injection and transport ability of 1 was proved. The luminance of 414 cd m−2 was achieved with the device configuration ITO/Eu(TTA)3(CPPO)2(40 nm)/BCP (30 nm)/Mg:Ag (BCP = 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline), which is favorable among double-layer organic light emitting devices based on small molecular Eu3+ complexes. The maximum current efficiency of 2.44 cd A−1 and external quantum efficiency of 1.55% demonstrate the potential application of 1 as a promising candidate for high-efficiency, simple-structure and pure red-emitting devices.