Soluble Europium Complexes for Light-Emitting Diodes

Soluble rare-earth complexes LiEu(TTA) 4, NaEu(TTA) 4, and KEu(TTA) 4 [TTA = 2-thenoyltrifluoroacetonato] were synthesized, and their luminescence properties doped in poly( N -vinylcarbazole) (PVK) thin films and in different solvents were observed. The results indicate that the emission comes from the Eu 3+ ion. The photoluminescence spectra of NaEu(TTA) 4 are independent of the solvent, with the exception of the luminescence intensity. When NaEu(TTA) 4 is doped into PVK films, the luminescence intensity of the Eu 3+ ion is enhanced with increasing NaEu(TTA) 4 concentration in the PVK film. The nature of the cations in the Eu 3+ complexes does not affect the luminescence performance and processability of the complexes. Single-, double-, and three-layer light-emitting diodes based on PVK doped with LiEu(TTA) 4, NaEu(TTA) 4, and KEu(TTA) 4 as an active layer were fabricated and investigated.