In-Situ Probing of H2O Effects on a Ru-Complex Adsorbed on TiO2 Using Ambient Pressure Photoelectron Spectroscopy

Abstract

Dye-sensitized interfaces in photocatalytic and solar cells systems are significantly affected by the choice of electrolyte solvent. In the present work, the interface between the hydrophobic Ru-complex Z907, a commonly used dye in molecular solar cells, and TiO 2 was investigated with ambient pressure photoelectron spectroscopy (AP-PES) to study the effect of water atmosphere on the chemical and electronic structure of the dye/TiO 2 interface. Both laboratory-based Al Ja as well as synchrotron-based ambient pressure measurements using hard X-ray (AP-HAXPES) were used. AP-HAXPES data were collected at pressures of up to 25 mbar (i.e., the vapor pressure of water at room temperature) showing the presence of an adsorbed water overlayer on the sample surface. Adopting a quantitative AP-HAXPES analysis methodology indicates a stable stoichiometry in the presence of the water atmosphere. However, solvation effects due to the presence of water were observed both in the valence band region and for the S 1s core level and the results were compared with DFT calculations of the dye-water complex.

Laboratory-based high pressure X-ray photoelectron spectroscopy: A novel and flexible reaction cell approach

“…For such applications, it is necessary to introduce a pressure separator, i.e., an X-ray transparent window, between the high vacuum of the monochromator and the elevated pressure around the sample in the analysis chamber. Eriksson et al report the properties of the source using a reinforced aluminium-coated window 15,23 and Newberg et al use a silicon nitride window. 13 In this paper, we present a third approach using a polyimide window built into the reaction cell itself.…”

Coadsorption of Dye Molecules at TiO2 Surfaces: A Photoelectron Spectroscopy Study

“…This dye shows good long-term stability as well as stability toward humidity. 33,34 By using coadsorbents in the photoactive interface, the efficiency of the Z907 sensitized DSC could be improved. 10 Specifically, when using DPA as a coadsorbent the short circuit current (J sc ) increases, and this has been addressed to either higher quantum yield for electron injection and/or reduced recombination.…”

“…Dyes based on ruthenium have shown to be highly efficient light absorbers in DSCs. ,− Previously, solar cells using the amphiphilic dye Z907 have shown a respectable solar to power conversion efficiency. This dye shows good long-term stability as well as stability toward humidity. , By using coadsorbents in the photoactive interface, the efficiency of the Z907 sensitized DSC could be improved . Specifically, when using DPA as a coadsorbent the short circuit current ( J sc ) increases, and this has been addressed to either higher quantum yield for electron injection and/or reduced recombination .…”