Two fluorine-functionalized 1,10-phenanthroline ligands, 2-(2-fluorophenyl) imidazo[4,5-f]1,10-phenanthroline (FPIP, L1), 3-ethyl-2-(2-fluorophenyl)imidazo[4,5-f]1,10-penanthroline (EFPIP, L2) and the corresponding Eu(III) complexes Eu(DBM)(3)(FPIP) (1) and Eu(DBM)(3)(EFPIP) (2) (DBM = dibenzoylmethanate) are successfully prepared. For comparative purpose, an unfunctionalized complex Eu(DBM)(3)(PIP) (3) (PIP = 2-Phenyl-imidazo[4,5-f]1,10-phenanthroline, L3) is also prepared. These Eu(III) complexes are characterized by elemental analysis, Fourier transform IR, and thermogravimetric analysis. Their photophysical properties are studied by absorption and emission spectra, temperature-dependence photoluminescence, and excited-state decay analysis. Comparing to the unfunctionalized complex 3, the fluorine functionalized complexes demonstrate higher photoluminescent efficiency. shorter excited-state decay lifetime, and better thermodynamic stability. Strikingly. the devices based on them exhibit an overall improvement in performances compared to those based on an Unfunctionalized complex, which is explained by energy-transfer mechanism and film-forming ability. (c) 2009 The Electrochemical Society. [DOI: 10.1149/1.3060228] All rights reserved.