Efficient Red Light-Emitting Diodes Based on Novel Europium Complexes in Poly(9,9-Dioctylfluorene) Host

The derivatives of tri(4,4,4-trifluoro-l-phenyl-1,3- butanedione) (1,10-phenanthroline) europium(III) (Eu(TPD)₃Phen), i.e. Eu(Ph-TPD)₃Phen and Eu(BiPh-TPD)₃Phen, were synthesized. Efficient red polymer light-emitting diodes (PLEDs) based on the europium complexes are fabricated with poly(9,9-dioctylfluorene) (PFO) in the presence of 30 wt.% electron-transporting compound 2-(4biphenylyl)-5-(ptertbutylphenyl)-1,3,4,oxadiazole (PBD) as the host. A significant improvement in the electroluminescent (EL) performances was observed by increasing the conjugated length of the europium complexes, and for the complex Eu(TPD)₃Phen, Eu(Ph-TPD)₃Phen and Eu(BiPh-TPD)₃Phen, the maximum luminance efficiency were respectively 0.12 cd/A, 0.45 cd/A and 1.27 cd/A, and the maximum brightness were 54 cd/m², 91 cd/m² and 231 cd/m², respectively.