佩多:嘘
拉曼光谱
X射线光电子能谱
材料科学
聚合物
导电聚合物
吸光度
紫外光电子能谱
化学工程
分析化学(期刊)
化学
有机化学
光学
工程类
复合材料
物理
色谱法
作者
Margreet M. de Kok,Michael Buechel,S. I. E. Vulto,Peter van de Weijer,Eric A. Meulenkamp,Suzanne H.P.M. de Winter,A. Mank,H. J. M. Vorstenbosch,Christ H. L. Weijtens,V. van Elsbergen
出处
期刊:Physica status solidi
[Wiley]
日期:2004-05-01
卷期号:201 (6): 1342-1359
被引量:190
标识
DOI:10.1002/pssa.200404338
摘要
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. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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