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Proceedings Paper

Electron-blocking mechanisms at the hole transport layer-emissive layer interface in polymer light-emitting diodes: enhanced device performance with a novel electron-blocking interlayer
Author(s): He Yan; Tobin Jay Marks
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Paper Abstract

The interface between the hole transport layer (HTL) and emissive layer (EML) in polymer light-emitting diodes (PLEDs) has attracted intense research attentioin since the initial discovery of PLEDs in 1989. In this contribution, we analyze the electron-blocking properties of various HTL at this interface and their effect on PLED device performance. We find that poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) - a conventional PLED HTL - does not possess optimum electron-blocking properties and that PLED device performance can be significantly enhanced by inserting a new type of electron-blocking layer (EBL) between the PEDOT-PSS HTL and EML. The new EBLs developed in this study consist of two major components: a siloxane-derivatized, crosslinkable, TPD-like triarylamine hole-transporting material, such as 4,4’-bis[(p-trichlorosilylpropylphenyl)phenylamino]biphenyl (TPDSi2), and a hole-transporting polymer, such as poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl) diphenylamine) (TFB). TPDSi2 undergoes crosslinking in air and rendering the TPDSi2 + TFB blend insoluble. With the TPDSi2 + TFB EBL inserted between PEDOT-PSS and BT layers, PLED device current density is reduced, device light output and current efficiency are dramatically increased (maximum current efficiency ~ 17 cd/A). Our result shows: 1) insufficient electron-blocking by PEDOT-PSS is another reason for the poor performance of PEDOT-PSS/BT based devices; 2) PLED device performance can be dramatically enhanced with a triarylamine siloxane-based EBLs.

Paper Details

Date Published: 10 November 2004
PDF: 9 pages
Proc. SPIE 5519, Organic Light-Emitting Materials and Devices VIII, (10 November 2004); doi: 10.1117/12.559906
Show Author Affiliations
He Yan, Northwestern Univ. (United States)
Tobin Jay Marks, Northwestern Univ. (United States)

Published in SPIE Proceedings Vol. 5519:
Organic Light-Emitting Materials and Devices VIII
Zakya H. Kafafi; Paul A. Lane, Editor(s)

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