Effective ionic charge polarization using typical supporting electrolyte and charge injection phenomena in molecularly doped polymer light-emitting diodes

An effective method of enhancing charge injection and electroluminescence efficiency of polymer-based light-emitting diodes is introduced. Spin-coated films of poly (N-vinylcarbazole) blended with electron-transport material (Bu–PBD), laser dye (Coumarin6), and the typical supporting electrolyte [te...

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Veröffentlicht in:Journal of applied physics 2002-11, Vol.92 (10), p.5971-5976
Hauptverfasser: Itoh, Eiji, Yamashita, Takanori, Miyairi, Keiichi
Format: Artikel
Sprache:eng
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Zusammenfassung:An effective method of enhancing charge injection and electroluminescence efficiency of polymer-based light-emitting diodes is introduced. Spin-coated films of poly (N-vinylcarbazole) blended with electron-transport material (Bu–PBD), laser dye (Coumarin6), and the typical supporting electrolyte [tetraethylammonium perchlorate (TEAP)] were examined and it was found that the injection current and luminance of the light emitting diodes doped with TEAP were enhanced dramatically after heat treatment at 80 °C and appropriate biasing in an external electric field of 1.5×108 V/m at this temperature. A charge injection model based on Fowler–Nordheim tunneling is proposed, taking into account electric field distortion due to the accumulation of ionic space charges at the electrode/film interface. The relaxation time of ionic polarization is found to be related to the cation size of the electrolyte.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.1513886