Quenching effects in organic electroluminescence - Publikacja - MOST Wiedzy


Quenching effects in organic electroluminescence


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>3.5 nm for the triplet exciton precursor pairs in the bimolecular recombination, and r CT=1.8+0.1 nm 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.

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Opublikowano w:
PHYSICAL REVIEW B nr 66, wydanie 23, strony 1 - 15,
ISSN: 2469-9950
Rok wydania:
Opis bibliograficzny:
Kalinowski J., Stampor W., Mężyk J., Cocchi M., Virgili D., Fattori V.: Quenching effects in organic electroluminescence// PHYSICAL REVIEW B. -Vol. 66., iss. 23 (2002), s.1-15
Politechnika Gdańska

wyświetlono 95 razy

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