Soluble europium complexes for light-emitting diodes

Soluble rare-earth complexes LiEu(TTA)(4), NaEu(TTA)(4), and KEu(TTA)(4) [T TA = 2-thenoyltrifluoroacetonato] were synthesized, and their luminescence properties doped in poly(N-vinylcarbazole) (PVK) thin films and in differen t solvents were observed. The results indicate that the emission comes from the Eu3+ ion. The photoluminescence spectra of NaEu(TTA)(4) are independen t of the solvent, with the exception of the luminescence intensity. When Na Eu(TTA)(4) is doped into PVK films, the luminescence intensity of the Eu3ion is enhanced with increasing NaEu(TTA)(4) concentration in the PVK film. The nature of the cations in the Eu3+ complexes does not affect the lumine scence performance and processability of the complexes. Single-, double-, a nd 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 invest igated.