期刊
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
卷 201, 期 6, 页码 1342-1359出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/pssa.200404338
关键词
-
Poly(3,4-ethylenedioxythiophene): poly (styrenesulphonic acid) (PEDOT:PSS) is commonly used as an anode in polymer light-emitting diodes (PLED). We have studied the effect of the pH and Na+ ion concentration of the aqueous PEDOT: PSS dispersion on the bulk and surface properties of spincoated films by various techniques, including UV-vis-NIR optical absorbance spectrometry, Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoemission Spectroscopy (UPS). A pH increase by addition of NaOH modifies the PEDOT: PSS properties in a similar way as electrochemical dedoping: the IR absorbance decreases, the Raman peaks shift, sharpen and increase in intensity, and the work function decreases. Consequently, a barrier for hole injection is introduced for several classes of light-emitting polymers. We argue that the mechanism of the pH-effect is different from electrochemical dedoping, and originates from a change in the relative stability of polarons and bipolarons on the doped thiophene. The changes in the electronic properties of PEDOT: PSS point to the determining role of the counter-ion in the stabilisation of oxidised thiophene units. Polymer LEDs comprising Na+-rich, proton poor PEDOT: PSS can show lower lifetime and efficiency than the corresponding Na+-free, proton-rich devices. For light emitting polymers which suffer from the addition of sodium to the hole injecting PEDOT: PSS, the decreased lifetime hints at hole injection as limiting factor in the degradation of these PLEDs. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据