Quenching effects in organic electrophosphorescence (Articolo in rivista)

Type
Label
  • Quenching effects in organic electrophosphorescence (Articolo in rivista) (literal)
Anno
  • 2002-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1103/PhysRevB.66.235321 (literal)
Alternative label
  • Kalinowski J., Stampor W., Mezyk J., Cocchi M., Virgili D., Fattori V., Di Marco P. (2002)
    Quenching effects in organic electrophosphorescence
    in Physical review. B, Condensed matter and materials physics (Online)
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Kalinowski J., Stampor W., Mezyk J., Cocchi M., Virgili D., Fattori V., Di Marco P. (literal)
Pagina inizio
  • 236321 (literal)
Pagina fine
  • 37636 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 66 (literal)
Rivista
Note
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • ISOF-CNR (literal)
Titolo
  • Quenching effects in organic electrophosphorescence (literal)
Abstract
  • We examine various electronic processes that underlie the quenching of the emission from highly efficient phosphorescent and electrophosphorescent organic solid-state molecular systems. As an example, we study the luminescent efficiencies from the phosphorescent iridium (III) complex, fac tris (2-phenylpyridine) iridium [Ir(ppy)3] doped into a diamine derivative doped polycarbonate hole-transporting matrix and in the form of vacuum-evaporated films, as a function of electric field. We demonstrate that the observed decrease in electrophosphorescence efficiencies at high electric fields, and electric-field-induced quenching of phosphorescence from neat [Ir(ppy)3] solid films is due to the field-assisted dissociation of Coulombically correlated electron-hole (e-h) pairs. They are formed in a bimolecular recombination process prior to the formation of emissive triplet excitons, or are charge-transfer (CT) states originating from the localized electronic excited states as a result of the initial charge separation upon photoexcitation, respectively. It is found that the high-field dependence of the quenching efficiency in both cases follows the three-dimensional Onsager theory of geminate recombination, the fit yielding the initial intercarrier distance (r0) of the carrier pairs. We find re-h>~3.5nm for the triplet exciton precursor pairs in the bimolecular recombination, and rCT=1.8±0.1nm for the initial carrier separation from the photo-excited electronic states. Triplet-triplet and triplet-charge carrier annihilation processes are shown to play major roles in the decrease of the electrophosphorescence efficiency within the lower-field regime at lower current densities. Summarizing the results allows us to point out some emitter features important for identifying phosphors useful for practical electroluminescent devices. (literal)
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