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Proceedings Paper

The role of isoelectronic dopants in organic light emitting diodes
Author(s): B. K. Crone; I. H. Campbell; D. L. Smith
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Paper Abstract

Power efficiency is an important parameter for all OLEDs, and is particularly critical for lighting applications. To maximize the power efficiency one must optimize charge injection, carrier transport, and radiative quantum efficiency, while minimizing energy losses. In this work we discuss how isoelectronic dopants can be used to address these problems. It can be difficult to produce efficient electrical contacts, particularly to large energy gap organic materials, and thus the contacts often limit the performance and stability of OLEDs . Recent results by several groups have attributed improved hole injection in poly (9,9' dioctylfluorene) [PFO] based LEDs to charge trapping, but the origin of the traps is unknown. In order to understand the role of traps in improving injection we studied poly[2-methoxy, 5-(2'- ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) devices with C60 molecules at the anode to improve hole injection. Isoelectronic dopants are used widely as recombination centers in organic light emitting diodes (OLEDs). In these systems one wants to maximize quantum efficiency by effectively trapping charges on the emitting dopants, while at the same time maximizing power efficiency by maintaining good charge transport. An understanding of the influence of the depth of the dopant on charge capture, and charge transport will aid in optimizing doped organic LEDs. We have looked at the OLED system consisting of the polymer PFO, and the organometallic molecule PhqIr. We show that PhqIr acts as a shallow hole trap in PFO, and that the charge transport and luminescence properties of this system are described by quasi-equilibrium statistics.

Paper Details

Date Published: 16 October 2007
PDF: 9 pages
Proc. SPIE 6655, Organic Light Emitting Materials and Devices XI, 665519 (16 October 2007); doi: 10.1117/12.732079
Show Author Affiliations
B. K. Crone, Los Alamos National Lab. (United States)
I. H. Campbell, Los Alamos National Lab. (United States)
D. L. Smith, Los Alamos National Lab. (United States)

Published in SPIE Proceedings Vol. 6655:
Organic Light Emitting Materials and Devices XI
Zakya H. Kafafi; Franky So, Editor(s)

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