Document Type

Thesis - University Access Only

Award Date

2012

Degree Name

Master of Science (MS)

Department / School

Electrical Engineering and Computer Science

First Advisor

Qiquan Qiao

Abstract

Electrospun carbon nanofibers, electrospun carbon nanofibers/carbon nanoparticles, and nickel incorporated carbon fibers/carbon nanotubes (NiC) composites have been demonstrated for the first time as efficient novel electrocatalysts in dye-sensitized solar cells (DSCs ). Electrospun carbon nano fiber and composite films exhibited a large cathodic peak current (lpc) and a low charge transfer resistance (R:1), indicating superior catalytic abilities compared to platinum films. DSCs based on electrospun carbon nanofibers (without use of a binder) yielded an efficiency of 5.5 % compared with 6.97 % for DSCs based on sputtered platinum. The major problem with electrospun carbon nanofiber-based DSCs was high series resistance (15.5 n cm2 compared to 4.8 n cm 2 for platinum-based DSCs ). The contact resistance was the main source of the series resistance and was ~8.55 ncm2 for a typical electrospun carbon nanofiber film without use of a binder. The use of an organic binder ( carboxymethyl cellulose sodium salt) with electrospun nanofibers reduced the contact resistance to ,_,Q.773 Ocm2 . DSCs with an electrospun carbon-nanofiber film had an efficiency of ,...,6.5 % compared to 7. 73 % for devices with a 40 nm thick sputtered platinum film. Raman spectroscopy of electrospun carbon nanofibers revealed that disordered carbon increased in the fibers as the carbonization temperature decreased from 1200°C to 900°C. DSCs based on electrospun carbon nanofibers carbonized at 900°C and 1200°C yielded 6.03 % and 6.50%, efficiencies, respectively. SEM images of electrospun carbon nanofiber films showed loosely-connected fibers with several micron-sized voids. Mixing carbon nanoparticles with nanofibers (I: I by weight) led to a compact film. DSC-based on electrospun carbon nanofibers/carbon nanoparticles composite counter electrode has an efficiency of 6.4 % compared to 7.3 % for platinum counter-based cells. DSCs based on NiC composite counter electrodes had an efficiency of 7.98 %, and DSC based on Pt counter electrodes (with film thickness of ~40 nm) had an efficiency of 8.32 %.

Library of Congress Subject Headings

Nanofibers
Carbon fibers
Electrospinning
Electrodes

Publisher

South Dakota State University

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Rights Statement

In Copyright