Document Type

Thesis - University Access Only

Award Date

2012

Degree Name

Master of Science (MS)

Department / School

Electrical Engineering and Computer Science

First Advisor

Hongshan He

Abstract

Dye sensitized solar cells (DSCs) are an inexpensive alternative to silicon solar cells due to inexpensive raw materials, simple cell design and efficiencies of 11 %. DSCs use Ru-complex dyes, which are expensive and toxic. A potential alternative is porphyrin dyes, which use inexpensive Zn metal complexes. Reports suggest that co-adsorbers such as COCA and DPA can reduce porphyrin dye aggregation and enhance the electron injection efficiency. Also porphyrins can be co-sensitized with complementary dyes to broaden the absorption band. The objectives of this research were to study the effect of porphyrin orientation on the Ti02 nanoparticles surface, the effect of co-adsorbers and cosensitizers towards on efficiency. Three porphyrin dyes; o-TMPZn-COOH (oporphyrin), m-TMPZn-COOH (m-porphyrin) and p-TMPZn-COOH (p-porphyrin) were tested in Ti02 nanoparticles based DSCs. The effect of porphyrin dye orientations, co-adsorbers and co-sensitizers were investigated using UVNis, fluorescence spectroscopy, 1-V, EQE and impedance spectroscopy. M-porphyrin dye cells had the highest efficiency of 3.58% with COCA coadsorber with an optimized molar ratio of 1 :2 and a 3-hour dye loading time. The orientation of porphyrin dyes relative to the Ti02 surface has a significant influence on the efficiency of the sensitized solar cells since it can reduce dye aggregation and increase electron injection. p-porphyrin dye cells with a perpendicular (para) dye attachment had lower efficiency d ue to reduced porphyrin aggregation. Dye loading time was critical for porphyrin sensitized solar cells; the m-porphyrin showed highest efficiency for 3-hour and where pporphyrin had the highest efficiency for 1-hour. COCA and DPA co-adsorbers can reduce aggregation of p-porphyrin, efficiency increased from 1.09% without co-adsorber to 3.10% and 2.74% respectively with co-adsorbers. BET dye can serve as both a co-sensitizer and co-adsorber for p-porphyrin, where cell efficiency was 2.90%. The lower efficiencies of porphyrin dyes in this work versus the best reported efficiency for YD2 porphyrin dyes (6.8% to 11 %) was attributed to the simpler molecular structure of the porphyrin dyes used versus those in the literature. The simplified structure can result in lower cost versus complicated fabrication process required for the more complex porphyrin structures. In order to improve efficiency of Ti02 nanoparticles based DSCs, future work should focus on improving charge transport using Ti02 nanotubes.

Library of Congress Subject Headings

Porphyrins
Dye-sensitized solar cells
Nanoparticles
Photovoltaic power generation

Publisher

South Dakota State University

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Rights Statement

In Copyright