Spectral and luminescent properties of mixed-ligand Eu(III) complexes were studied in solutions and in polyvinylcarbazole (PVC) thin films. Trends in their variations were found depending on the complex structure and excitation mode. The electroluminescence was observed in ITO/PEDOT/Eu complex:PVC/CaMg/Al devices. Their current-voltage and voltage-brightness characteristics were investigated.Introduction. Lanthanides (Ln) and their compounds are of enduring interest due to the variety of properties and expanding sphere of practical applications in science, medicine, and technology. These include optical light diodes, novel light sources, and functional materials of various designation [1][2][3]. In particular, the fabrication of white-light emission sources requires the mixing of three colors, i.e., red, green, and blue. Only complexes of rare-earth elements (REE) can provide "pure" color emission, in contrast with organic fluorescent dyes, which have broad emission bands. Complexes of REE combine a high efficiency and narrow emission band and, as a result, are very attractive for this purpose. The photophysics of organometallic complexes of various structures and the establishment of trends in the change of emission of such compounds as a function of their structures are definitely interesting.Complexes of Eu with β-diketones and Tb with acylpyrazolones, which contain β-diketone groups that form strong six-membered rings with the complexed ion, exhibit the strongest photo-and electroluminescence (PL and EL) [3]. β-Diketones are the only reagents of their type in complexes of which the energy-transfer quantum yield from the ligand to Ln(III) ion approaches unity [4]. Luminescence of Eu is studied most for β-dicarbonyl compounds. Compounds containing fluorinated substituents emit significantly stronger than those containing non-fluorinated analogs. Coordinatively unsaturated Ln(III) β-diketonates add readily donor ligands such as H 2 O, solvents, and organic bases. Organic bases [1,10-phenanthroline (Phen), trioctyl-and triphenylphosphine oxide (TOPO and TPPO), etc.] form very strong bonds to the Ln(III) ion and can eliminate H 2 O (OH-oscillators) from the inner coordination sphere of the complex. This increases drastically the luminescence intensity. This effect can also be achieved by increasing the ligand hydrophobicity through the introduction of fluorinated substituents with a long chain (-C 6 F 13 , -C 8 F 17 ). These were first synthesized [5] and proposed for highly sensitive luminescence determination of Eu(III) and Sm(III) in REE oxides. The highest intensity of Eu luminescence was observed in complexes with perfluoro-β-diketones with the same secondary substituent [6,7]. PL of Eu with naphthoyltrifluoroacetone (NTFA) was reported [8].The present work is a continuation of previously initiated investigations on the effect of the structure of Eu coordination compounds on their PL and EL properties. The spectral and luminescent properties of binary and mixedligand complexes Eu (TTA) 3 , Eu(TTA) 3 TPPO, and...