Analysis of the Dye/Titania Interface as Photo-Anode in Dye Sensitized Solar Cells

Author: Herri Trilaksana

Trilaksana, Herri, 2018 Analysis of the Dye/Titania Interface as Photo-Anode in Dye Sensitized Solar Cells, Flinders University, College of Science and Engineering

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The understanding of the unwanted process such as charge recombination, in Dye Sensitised Solar Cells (DSSCs) are still a challenging issue to gain the effort of improving this promising photovoltaic technique. The dye/titania and dye/electrolyte interfaces are playing a crucial factor of photovoltaic and this is the focus of this thesis. Four main issues have been chosen for investigations of this study which cover the corresponding influence of the electrolyte exposure, the organic and the metal-organic dyes-titania attachment in term of monolayer versus a multilayer, the aging effect, and the application of the co-adsorbent. The dye formation and the change of its electronic and molecular structure were studied.

Electron spectroscopy techniques including X-ray Photoelectron Emission Spectroscopy (XPS), Ultra-violet Photoelectron Spectroscopy (UPS) and Metastable Induced Electron Spectroscopy (MIES) have been employed to directly observe the changes with respect to the electronic structure representing the molecular restructuring and reorientation of the dye. Neutral Impact Collision Ion Scattering Spectroscopy (NICISS) is an ion spectroscopy technique used to study the molecular coverage and concentration depth profiling of the dye. These spectroscopic methods are capable in probing various depths where each technique is potentially able to determine the exact position of a component in the sample. FT-IR spectroscopy was used as a complementary method of electron and ion spectroscopy to determine the organic compound. FTIR is useful in determining the organic functional groups on the sample however it is not surface sensitive. FTIR is used to study sample with corresponding to the organic material such as co-adsorbent in this thesis.

The ruthenium-based dye N719 and Z907 are used to study the effect of the electrolyte exposure through the investigation of the iodine as a representative component of the electrolyte. The study investigated the changes of the electronic and molecular structure such as the indication of dipole layer formation, which can be attributed to the change of the work function, and the restructuring or reorientation of the outermost dye molecules.

The L0Br organic dye was used to investigate the formation of monolayer and multilayer dye molecule on the mesoporous titania semiconductor by determining the concentration depth profiles and its molecular coverage from the adsorption isotherm. The result showed that the L0Br formed more monolayer than the multilayer.

The effects of aging and electrolyte exposure were also observed using the PD2 and LEG1 organic dyes using two different electrolytes with containing and not containing the TBP. As a result of this study, it was observed that the LEG1 dye showed larger work-function changes than the PD2 and the electrolyte containing the TBP were affecting less to the formation of a dipole on the titania/dye interface which can be attributed to the change of the electronic structure or work-function of the dye.

The final chapter studied how the Chenodeoxycholic Acid (CDCA) as co-adsorbent influenced to the dye formation from the perspectives of the enhancement of the monolayer dye formation and preventing the dye aggregation. It was shown that the co-adsorbent suppressed the formation of multilayer dye and it was found to be dependent on the concentration of the co-adsorbent. These spectroscopic studies contribute to the better understanding of the electronic and molecular structure and also morphology of dye in titania/dye/electrolyte interface in DSSC.

Keywords: Dye-Sensitized Solar Cells, Electron Spectroscopy, XPS, UPS, MIES, NICISS, Iodine, Titania, Electrolyte, Chenodeoxycholic Acid

Subject: Physics thesis

Thesis type: Doctor of Philosophy
Completed: 2018
School: College of Science and Engineering
Supervisor: Gunther Andersson