New extended fluorenylpyridine ligands FlnPy (n=1,3,5) and their triscyclometalated iridium (III) complexes Ir[FlnPy]33, 4, and 5 have been synthesised and their photophysical properties have been
studied. The lowest energy (emissive) excited state of the complexes 3-5 is dominated by ligand centered
3(π→π*) triplet states, as observed in their ligands. Efficient white-polymeric light-emitting diodes (PLED)
were fabricated as a single active layer containing blue emitting poly (9,9-bis(2-ethylhexyl)fluorine-2,7-
diyl) endcapped with bis(4-methylphenyl)phenylamine (PF2/6am4), and yellow-orange emitting from
Iridium complex 4. The fluorene-like ligands in the blended device prevent phase segregation and also
enhance energy transfer from the polymer host to the guest due to efficient overlap of wavefunction
(Dexter process) and host singlet emission and guest absorption bands (F&diaero;rster process) which reduces the
loading level required to produce white emission. The two emitted colours complement each other and
doping levels between 2% to 3% produce white emission. Above a certain current density depending on the
doping level the device CIE coordinates become bias independent and a stabilised white emission can be
obtained. A white emission PLED (coordinate (0. 348, 0.367) of peak external quantum efficiency (EQE)
of 2.8 %, and luminance of 16000 cd/m2) at applied voltage of 5V (ie. 4.57 cd/A) was obtained. device CIE
coordinates become bias independent and a stabilised white emission can be obtained. A white emission
PLED (coordinate (0. 3477, 0.3667) of peak external quantum efficiency (EQE) of 2.8 %, and luminance of
16000 cd/m2 at applied voltage of 5V (ie. 4.57 cd/A) was obtained.
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