Dye Sensitized Solar Cells Thesis Statements

EFFICIENCY ENHANCEMENT IN DYE-SENSITIZED SOLAR CELLS THROUGH LIGHT MANIPULATION

Author:
Abrams, Neal Mathew
Graduate Program:
Chemistry
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
September 14, 2005
Committee Members:
  • Thomas E Mallouk, Committee Chair
  • Karl Todd Mueller, Committee Member
  • Christine Dolan Keating, Committee Member
  • Vincent Henry Crespi, Committee Member
Keywords:
  • dye sensitized solar cell
  • Gratzel cell
  • photonic crystal
  • solar cell
Abstract:
<p> Solar energy conversion is dominated by expensive solid-state photovoltaic cells. As low-cost cells continue to develop, the dye sensitized solar cell has generated considerable interest as an efficient alternative. Although already moderately efficient, this cell offers numerous areas for improvement, both electronically and optically. Solar conversion efficiencies have been studied by modifying optical pathways through these dye-sensitized solar cells, or Grätzel cells. Monochromatic incident-to-photon current efficiency (IPCE) data reveals that an inverse opal photonic crystal or other disordered layer coupled to a nanocrystalline TiO<sub>2</sub> layer enhances photocurrent efficiency by illumination from the counter electrode direction. Modifying the cell architecture to allow for illumination through the working electrode yields similar increased enhancements by proper selection of the photonic bandgap. Direct growth of TiO<sub>2</sub> inverse opals on a nanocrystalline slab was accomplished by polymer infiltration of the slab, followed by crystal growth and liquid phase deposition. Results demonstrate that the bilayer architecture contributes to the enhanced light harvesting rather than the inverse opal layer and is due, in part, to strong light localization, Bragg diffraction and enhanced scattering. These effects occur solely at the bilayer interface and largely contribute to the photocurrent enhancements in the 540 – 750 nm region where the sensitizer dye is a poor absorber. TiO2 sculptured thin films were also studied and offer promise for the development of efficient solid-state dye cells.</p> <p> Visible light undergoes effective solar energy conversion by the typical dye-sensitized solar cells, but is detrimental to silicon solar cells. In contrast, near-infrared light is not utilized by these dye cells, but results in high efficiencies for silicon. Spectrum-splitting tandem cell architectures consisting of a Grätzel cell and a silicon photovoltaic module have been designed and tested. Spectral ranges were separated by reflecting near-infrared light using a hot-mirror coating on the Grätzel cell. A cell module was fabricating using 12 individual Grätzel cells and a single silicon concentrator and tested under solar conditions, yielding proof-of-principle data for the development of future modules. Colloidal crystals are large-scale analogs of inorganic crystals, and their synthesis has been developed into an educational lab for high school and undergraduate students.</p> <p> Colloidal crystals are self-assembled onto glass substrates, followed by polymer templating. This lab effectively introduces majors and non-majors alike to a unique area of materials synthesis with a modular approach towards synthesis, instrumentation, and characterization. The adaptability of this lab to various skill levels as well as opportunities for cooperative based learning makes this lab an excellent curricular addition.

Reference:

Wills, K., 2014. Copper dyes for dye-sensitized solar cells. Thesis (Doctor of Philosophy (PhD)). University of Bath.

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Abstract

This thesis studies the application of copper(I) complexes as the sensitizing component of dye sensitized solar cells (DSCs). Ruthenium(II) polypyridyl complexes have been widely studied and shown great success for the past two decades; however the metal is rare and expensive. A copper(I) based DSC could offer a viable alternative to using ruthenium(II) dyes, taking into account the cost and sustainability advantages. Interest in copper(I) DSCs has reignited over the past five years and the work in this thesis begins by reproducing the synthesis of one of the first reported complexes, [Cu(6,6’-dimethyl-2,2’-bipyridine-4,4’-dicarboxylic acid)2][Cl]. A more detailed study of the dye and its properties will be described, including assessing the effect of TiO2 film dye time on DSC performance, electrochemical studies and coupling the dye with a Co2+/3+ mediator. In the following chapters, improvements to the basic 2,2’-bipyridine framework are investigated. An experimental and computational investigation with a [Cu(2,2'-biquinoline-4,4'-dicarboxylic acid)2][HNEt3] complex is presented, where the 2,2’-biquinoline ligand has been chosen as a bulkier, more conjugated alternative to the 2,2’-bipyridine ligand. Although DSC efficiencies with this complex are comparatively low, an investigation into possible reasons for this is described. This thesis then considers functionalisation of a 2,2’-bipyridine ligand with halide and thiophene substituents. Several new ligands and copper(I) complexes are described and characterised. A top DSC efficiency of 1.41% was obtained with a [Cu(6,6'-dimethyl-[2,2'-bipyridine]-4,4'-diyl)bis(thiophene-2-carboxylic acid)2][PF6] dye. The synthetic route towards this complex and an analysis of its features, such as emissive behaviour, electrochemical properties and electron diffusion length, are described.

Item TypeThesis (Doctor of Philosophy (PhD))
CreatorsWills, K.
DepartmentsFaculty of Science > Chemistry
Research CentresCentre for Sustainable Chemical Technologies
Publisher Statementk_wills_PhD_thesis_submitted_april_2014_WITH_CORRECTIONS_approved_PURE2.pdf: © The Author
StatusUnpublished
ID Code43316

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