AVS 51st International Symposium
    Surface Science Wednesday Sessions
       Session SS1-WeA

Paper SS1-WeA9
+ACQ+AHs+Dye Sensitization of the TiO+AEA-Sub 2+AEA- polymorph Anatase (101) Single Crystal Surface by a Series of Dicarboxylated Thiacyanine Dyes+AHs+AH0-

Wednesday, November 17, 2004, 4:40 pm, Room 210B

Session: Metal Oxides and Clusters II: TiO@sub 2@ and Photocatalysis
Presenter: N. Ruzycki, Colorado State University
Authors: N. Ruzycki, Colorado State University
S. Ushiroda, Colorado State University
Y. Lu, Colorado State University
M.T. Spitler, ChemMotif, Inc.
B.A. Parkinson, Colorado State University
Correspondent: Click to Email
+ACQ-Body +AHs-The dye sensitization of the TiO+AEA-Sub 2+AEA- polymorph anatase (101) is an important system of study because of its application to dye-sensitized solar cells such as the Gr+AEA-um A+AEA-tzel cell. The electrons per photon quantum yields for the dye sensitization of anatase are reported to be higher than those for the rutile polymorph of TiO+AEA-Sub 2+AEA-. The reason that anatase is a better substrate for photovoltaic purposes is yet unknown. The efficiency of solar cells is closely tied to the yield and rate of the electron transfer from the dye molecule to the surface, factors that will be influenced by the geometry of the dye binding and ordering at the surface. Studies that link UHV and electrochemical experiments are a first step towards understanding the mechanism of dye binding to the surface of this material. Dye sensitization of the single crystal anatase (101) surface was studied using a series of dicarboxylated thiacyanine dyes that bind to the surface through the carboxylate group. An ultraviolet (UV) light treatment of the anatase (101) surface, immediately prior to dye adsorption, improves both the reproducibility of dye coverage and the incident photon-to-current efficiencies (IPCE) for sensitization. The UV treatment does not pit or roughen the anatase surface and results in high IPCEs of up to 0.5 percent. The adsorption isotherms and adsorption and desorption kinetics of these dyes were studied. The photocurrent spectra showed features associated with surface-bound dye monomers, dimers and aggregates that could be followed as a function of the dye surface coverage. UHV studies on the single crystal anatase (101) surface were undertaken, including STM, for adsorption of a molecule (bis-isonicotinic acid) that had approximately the same backbone structure and carboxylate group as the dyes in order to elucidate structural models for the dye binding to the surface. +AEA.