Phosphonic acid modification of indium-tin oxide electrodes: Combined XPS/UPS/contact angle studies

被引:218
作者
Paniagua, Sergio A. [3 ,4 ]
Hotchkiss, Peter J. [1 ,2 ]
Jones, Simon C. [1 ,2 ]
Marder, Seth. R. [1 ,2 ]
Mudalige, Anoma [3 ]
Marrikar, F. Saneeha [3 ]
Pemberton, Jeanne E. [3 ]
Armstrong, Neal R. [3 ]
机构
[1] Georgia Inst Technol, Dept Chem & Biochem, Atlanta, GA 30332 USA
[2] Georgia Inst Technol, Ctr Organ Photon & Elect, Atlanta, GA 30332 USA
[3] Univ Arizona, Dept Chem, Tucson, AZ 85721 USA
[4] Univ Costa Rica, Dept Chem, San Jose, Costa Rica
关键词
D O I
10.1021/jp710893k
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Indium-tin oxide (ITO) electrodes have been modified with both fluorinated alkyl and aryl phosphonic acids [n-hexylphosphonic acid (HPA) and n-octadecylphosphonic acid (ODPA); 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl phosphonic acid (FHOPA), pentafluorobenzyl phosphonic acid (PFBPA), and tetrafluorobenzyl1,4-diphosphonic acid (TFBdiPA)]. These are modifiers designed to control both wetting properties toward nonpolar molecular solids and to provide a wide range of tunability in effective surface work function. The molecular nature of surface attachment and changes in electronic and wetting properties were characterized by X-ray photoelectron spectroscopy (XPS), UV-photoelectron spectroscopy (UPS), photoelastic modulation infrared reflection-absorption spectroscopy (PM-IRRAS), and contact angle measurements using both water and hexadecane. Interface dipoles from the PA modifiers contribute to shifts in the low kinetic energy regions of UPS spectra (local vacuum level shifts, which translate into changes in effective surface work function). We show that for ITO surfaces modified with FHOPA, and to a lesser extent with PFBPA, the high work function obtained by oxygen plasma cleaning can be maintained after modification, while decreasing the polar component of surface energy. This approach to oxide surface modification is a strategy that may be beneficial for the modification of transparent conducting oxide surfaces in both organic light emitting diodes and in organic solar cells, where oxide/organic compatibility can affect device performance.
引用
收藏
页码:7809 / 7817
页数:9
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