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Durham University

Department of Physics

Staff profile

Publication details for Associate Professor Fernando Dias

Tavasli, M, Bettington, S, Bryce, MR, Al Attar, HA, Dias, FB, King, S & Monkman, AP (2005). Oligo(fluorenyl) pyridine ligands and their tris-cyclometalated iridium(III) complexes: synthesis, photophysical properties and electrophosphorescent devices. Journal Of Materials Chemistry 15(46): 4963-4970.
  • Publication type: Journal Article
  • ISSN/ISBN: 0959-9428
  • Keywords: LIGHT-EMITTING DEVICES; ENERGY-TRANSFER; RED ELECTROPHOSPHORESCENCE; PHOSPHORESCENT EMISSION; QUANTUM EFFICIENCY; CARBONYL-COMPLEXES; OPTICAL-PROPERTIES; DIODES; POLYMERS; ELECTROLUMINESCENCE

Author(s) from Durham

Abstract

The new extended tri- and penta-fluorenylpyridine ligands Fl(3)Py 2 and
Fl(5)Py 3 and their tris-cyclometalated iridium(III) complexes
Ir[Fl(3)Py](3) 5 and Ir[Fl(5)Py](3) 6 have been synthesised and their
properties compared with the known iridium( III) complex Ir[Fl(1)Py](3)
4. The lowest energy (emissive) excited states of the complexes 4-6 are
dominated by ligand centred (LC) (3)pi ->pi* triplet states, as
observed for their uncomplexed ligands 1-3. The emission maximum of
complex 4 is similar to 546 nm with a triplet lifetime of 2.8 mu s. For
complexes 5 and 6 the emission maxima are both similar to 566 nm with
triplet lifetimes of 7.4 mu s and 7.8 mu s, respectively. Devices made
from poly(9,9'-spirobifluorene) (PSF) as the host and doped with
complexes 4-6 show good stability; the EL spectra are unchanged after
repeated operation over several days. Devices containing complexes 5
and 6 exhibit higher external quantum efficiency (EQE) values. Turn-on
voltages of similar to 3 V, giving an EQE of 2.8% at a current density
of 30 mA cm(-2), with a power efficiency of 4.3 lm W-1 and
electroluminescence (EL) intensity of 25 000 cd m(-2) at 550 mA cm(-2)
were observed for ITO/PEDOT : PSS/PSF : 6/Ca/Al devices.