Electroluminescent properties of a Eu-complex doped in phosphorescent materials

Electroluminescent spectra of thin films in which a Eu(III)-beta-diketonate complex is doped into a phosphorescent layer have been investigated. At lo w temperatures (77 K), the spectra consist of emissions both from the tripl et excited levels of the phosphorescent material and from the D-5(0) and D- 5(1) levels of the Eu3+ ion. In contrast, electroluminescent spectra from t he Eu complex at room temperature and photoluminescent spectra from the Eu complex consist predominantly of emissions from the D-5(0) level. Furthermo re, the electroluminescent spectra at room temperature depend on the host m aterials. Energy transfer from triplet states of the phosphorescent materia ls to the ligand triplet state of the Eu complex and emission saturation of the Eu3+ ion at a higher level of current-injection are discussed. (C) 199 9 Elsevier Science B.V. All rights reserved.