16 December 1998 Electrochemical models for the radical annihilation reactions in organic light-emitting diodes
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Abstract
Bilayer organic light emitting diodes (OLEDs), based upon vacuum deposited molecules, or single layer OLEDs, based upon spin-cast polymeric materials, doped with these same molecules, produce light from emissive states of the lumophores which are created through annihilation reactions of radical species, which can be modeled through solution electrochemistry. Difference seen in solution reduction and oxidation potentials of molecular components of OLEDs are a lower limit estimate to the differences in energy of these same radical species in the condensed phase environmental. The light emitted from an aluminum quinolate (Alq3)/triarylamine (TPD)-based OLED, or an Alq3/PVK single layers OLED, can be reproduce from solution cross reactions of Alq3/TPD+. The efficiency of this process increases as the oxidation potential of the TPD increases, due to added substituents. Radical cations and anions of solubilized version of quinacridone dopants (DIQA) which have been used to enhance efficiencies in these OLEDs, are shown to be electrochemically more stable than Alq3 and Alq3, and DIQA radical annihilation reactions produce the same emissive state as in the quinacridone-doped OLEDs. Electrochemical studies demonstrate the ways in which other dopants might enhance the efficiency and shift the color output of OLEDs, across the entire visible and near-IR spectrum. Chemical degradation pathways of these same molecular components, which they may undergo during OLED operation, are also revealed by these electrochemical studies.
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Neal R. Armstrong, Neal R. Armstrong, Jeffrey D. Anderson, Jeffrey D. Anderson, Paul A. Lee, Paul A. Lee, Erin McDonald, Erin McDonald, R. Mark Wightman, R. Mark Wightman, Hank K. Hall, Hank K. Hall, Tracy Hopkins, Tracy Hopkins, Anne Padias, Anne Padias, Sankaran Thayumanavan, Sankaran Thayumanavan, Stephen Barlow, Stephen Barlow, Seth R. Marder, Seth R. Marder, } "Electrochemical models for the radical annihilation reactions in organic light-emitting diodes", Proc. SPIE 3476, Organic Light-Emitting Materials and Devices II, (16 December 1998); doi: 10.1117/12.332611; https://doi.org/10.1117/12.332611
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