Electron-Transfer Processes in Zinc Phthalocyanine鈥揚hosphonic Acid Monolayers on ITO: Characterization of Orientation and Charge-Transfer Kinetics by Waveguide Spectroelectrochemistry

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• 作者：Hsiao-Chu Lin ; Nathan W. Polaske ; Luis E. Oquendo ; Matthew Gliboff ; Kristina M. Knesting ; Dennis Nordlund ; David S. Ginger ; Erin L. Ratcliff ; Brooke M. Beam ; Neal R. Armstrong ; Dominic V. McGrath ; S. Scott Saavedra
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2012
• 出版时间：May 3, 2012
• 年：2012
• 卷：3
• 期：9
• 页码：1154-1158
• 全文大小：272K
• 年卷期：v.3,no.9(May 3, 2012)
• ISSN：1948-7185

文摘

Using a monolayer of zinc phthalocyanine (ZnPcPA) tethered to indium tin oxide (ITO) as a model for the donor/transparent conducting oxide (TCO) interface in organic photovoltaics (OPVs), we demonstrate the relationship between molecular orientation and charge-transfer rates using spectroscopic, electrochemical, and spectroelectrochemical methods. Both monomeric and aggregated forms of the phthalocyanine (Pc) are observed in ZnPcPA monolayers. Potential-modulated attenuated total reflectance (PM-ATR) measurements show that the monomeric subpopulation undergoes oxidation/reduction with k_s,app = 2 脳 10² s^鈥?, independent of Pc orientation. For the aggregated ZnPcPA, faster orientation-dependent charge-transfer rates are observed. For in-plane-oriented Pc aggregates, k_s,app = 2 脳 10³ s^鈥?, whereas for upright Pc aggregates, k_s,app = 7 脳 10² s^鈥?. The rates for the aggregates are comparable to those required for redox-active interlayer films at the hole-collection contact in organic solar cells.

Keywords:

electron-transfer kinetics; molecular orientation; organic photovoltaic; solar cell; organic donor layer; attenuated total reflectance; transparent conductive oxide