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Superficial fluoropolymer layers for efficient light-emitting diodes

Latini, G, Tan, LW, Cacialli, F and Silva, SRP (2012) Superficial fluoropolymer layers for efficient light-emitting diodes Organic Electronics, 13 (6). 992 - 998. ISSN 1566-1199

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Abstract

Fluoropolymers are characterized by high chemical inertness and, when in solid state, by superficial dipoles due to the C–F bond where the charge density is strongly displaced. These two characteristics are exploited here for fine control of charge balance in organic light-emitting devices and for preventing electrochemical interaction between heterogeneous layers. The insertion of a thin layer of polytetrafluoroethylene, PTFE, at the interface between poly(ethylene dioxythiophene):poly(styrene sulfonic acid), PEDOT:PSS, and an electroluminescent polymer leads to improved device efficiency and longevity. The presence of the superficial dipole increases the effective work function of the anode and improves the charge balance which enhances the external quantum efficiency, EQE, of the devices by up to a factor of two without significant effects on the luminance levels. The insertion of the PTFE layer reduces the photoluminescence quenching at the PEDOT:PSS/polymer interface, however we show that the EQE enhancement is mainly due to a better confinement of minority carrier electrons in the active layer. The lifetime of the devices shows a remarkable increase correlated with the insertion of the PTFE layer. Such improvements are ascribed to the reduced electrochemical interaction between the electroluminescent polymer and PEDOT:PSS due to the chemically inert nature of PTFE. The PTFE acts as a chemical zipper of two heterogeneous media with the added functionality of control over the charge balance.

Item Type: Article
Additional Information: NOTICE: this is the author’s version of a work that was accepted for publication in Organic Electronics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Organic Electronics, 13(6), June 2012, DOI 10.1016/j.orgel.2012.02.019.
Divisions: Faculty of Engineering and Physical Sciences > Electronic Engineering > Advanced Technology Institute > Nano-Electronics Centre
Depositing User: Symplectic Elements
Date Deposited: 30 Nov 2012 12:23
Last Modified: 23 Sep 2013 19:50
URI: http://epubs.surrey.ac.uk/id/eprint/735789

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