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Proceedings Paper

Interface effects on the defect state formation in organic devices
Author(s): T. P. Nguyen; C. Renaud
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Paper Abstract

We have investigated the role of interfaces in the formation of traps in organic devices using poly(9,9-dihexylfluorene-co-N,N-di(9,9-dihexyl-2-fluorenyl)-N-phenylamine) (PF-N-Ph) as an emissive material. The basic structure of the studied diodes is ITO/PEDOT:PSS/PF/M where M is Al or Ca/Al. Trap parameters have been measured by Charge based Deep Level Transient Spectroscopy (Q-DLTS) in diodes having different electrode configurations. Five trap levels have been identified in the basic device structures with activation energies in the range of 0.1 - 0.6 eV and trap densities in the range of 1016 - 1017 cm-3. On the cathode side, no noticeable changes have been observed when changing the electrode from aluminium to calcium. On the anode side, comparing the trap parameters in devices with and without a PEDOT:PSS layer, we show that the hole injection layer introduced new trap levels, which are electron-traps. The density of these traps is of the order of 1016 cm-3 and their levels are at ~ 0.3 and ~ 0.5 eV from the band edges. The findings confirm and complete quantitatively earlier results by other groups on the role of the PEDOT:PSS /organic interface in the trap formation in OLEDs.

Paper Details

Date Published: 12 February 2009
PDF: 8 pages
Proc. SPIE 7213, Organic Photonic Materials and Devices XI, 721314 (12 February 2009); doi: 10.1117/12.807037
Show Author Affiliations
T. P. Nguyen, Institute des Matériaux Jean Rouxel, Univ. of Nantes, CNRS (France)
C. Renaud, Institute des Matériaux Jean Rouxel, Univ. of Nantes, CNRS (France)


Published in SPIE Proceedings Vol. 7213:
Organic Photonic Materials and Devices XI
Robert L. Nelson; François Kajzar; Toshikuni Kaino, Editor(s)

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