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Electrophosphorescence from a Polymer Guest–Host System with an Iridium Complex as Guest: Förster Energy Transfer and Charge Trapping
Author(s) -
Gong X.,
Ostrowski J.C.,
Moses D.,
Bazan G.C.,
Heeger A.J.
Publication year - 2003
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200304334
Subject(s) - iridium , materials science , phosphorescence , oled , fluorene , electroluminescence , quantum efficiency , photochemistry , luminous efficacy , optoelectronics , phosphorescent organic light emitting diode , fluorescence , polymer , nanotechnology , chemistry , optics , catalysis , organic chemistry , physics , layer (electronics) , composite material
We report high‐efficiency green electrophosphorescent light‐emitting diodes obtained by using tris[9,9‐dihexyl‐2‐(phenyl‐4′‐(‐pyridin‐2″‐yl))fluorene]iridium( III ) (Ir(DPPF) 3 ) as the guest, and a blend of poly(vinylcarbazole) (PVK) with 2‐ tert ‐butylphenyl‐5‐biphenyl‐1,3,4‐oxadiazol (PBD) as the host. The electrophosphorescent emission is characteristic of Ir(DPPF) 3 , with its maximum at 550 nm. An external quantum efficiency of 8 % photons per electron and luminous efficiency of 29 cd A –1 , with maximum brightness of 3500 cd m –2 , were achieved at 1 wt.‐% concentration of Ir(DPPF) 3 . The devices exhibited no emission from PVK or PBD, even at the lowest concentration of Ir(DPPF) 3 (0.1 wt.‐%). The results indicate that Förster energy transfer plays a minor role in achieving high efficiencies in these devices. Direct charge trapping appears to be the main operating mechanism.