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Proceedings Paper

Altering the interfacial morphology of polymer light-emitting diodes using polymer interlayers: effect on hole injection and device performance
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Paper Abstract

We report preliminary studies of the nature of hole injection from poly(3,4-ethylenedioxythiophene)/polystyrenesulphonic acid (PEDOT:PSS) into three commercial conjugated light emitting polymers (LEPs). Sumation's LUMATION Green 1300, LUMATION Blue, and Merck's SuperYellow LEPs are studied in combination with interlayers of poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB), and poly[9,9-dioctylfluorene-co-(bis-N,N'-(3-carboxyphenyl)-bis-N,N'-phenylbenzidine)] (BFA). Despite the highest occupied molecular orbitals (HOMOs) of the interlayers being close to that of PEDOT:PSS and the LEP, different interlayers have different effects on hole injection and OLED device performance. We use dark injection transient current method to show that interfacial morphology changes results in modulation of hole trap densities that in turn affect hole injection. Depending on the interlayer/LEP combination partial penetration of interlayer into the LEP layer may also occur resulting in additional changes in the bulk transport properties of the LEP. Our results show that it is not the interfacial energy level alignment but the physical morphology changes at the interface which are important for varying hole injection into the device. A combination of either improved or reduced hole injection due to variations in physical contact, intermixing and trapping at the interlayer/LEP boundary dominate device performance.

Paper Details

Date Published: 5 December 2006
PDF: 6 pages
Proc. SPIE 6333, Organic Light Emitting Materials and Devices X, 63331M (5 December 2006); doi: 10.1117/12.680649
Show Author Affiliations
M. James Harding, Imperial College London (United Kingdom)
Osram Opto Semiconductors, Inc. (United States)
Dmitry Poplavskyy, Osram Opto Semiconductors, Inc. (United States)
Vi-En Choong, Osram Opto Semiconductors, Inc. (United States)
Franky So, Osram Opto Semiconductors, Inc. (United States)
Alasdair J. Campbell, Imperial College London (United Kingdom)

Published in SPIE Proceedings Vol. 6333:
Organic Light Emitting Materials and Devices X
Zakya H. Kafafi; Franky So, Editor(s)

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