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Document Type

Thesis - University Access Only

Award Date

2013

Degree Name

Master of Science (MS)

Department

Electrical Engineering and Computer Science

First Advisor

Xing Zhong Yan

Second Advisor

David Galipeau

Abstract

Organic-based solar cells including polymer, small organic, and dye sensitized solar cells are considered as a promising source for clean and renewable energy. The reason behind this is that organic-based solar cells offer light weight and use low cost materials. They can be fabricated through solution processed deposition technique to enable roll-to roll processing over a large area. Moreover, the efficiencies of organic solar cells based on bulk heterojunctions have continued to rise from 1% in 1995 to 10.6% in 2012. However, organic solar cells have stability issues and liquid electrolyte based dye sensitized solar cells suffer from the problem of solvent leakage and sealing. Semiconductor Sb2S3 sensitized hybrid solar cells are an attractive option since crystalline Sb2S3 has a tunable band gap, high absorption coefficient, high extinction coefficient, and large intrinsic dipole moment. These solar cells incorporated with ZnO nanorod arrays possess advantages including solution processability, high electron mobility, and chemical stability of ZnO nanorods.In this thesis, a new type of hybrid solar cells was developed by integrating ZnO nanorod arrays, antimony sulfide (Sb2S3) thin film, and poly (3-hexylthiophene) (P3HT) layer deposited by solution-based processing. Chemical bath deposition was developed for growing the ZnO nanorod arrays and depositing the Sb2S3 thin films. Spin-coating was utilized for depositing the P3HT film. A scanning electron microscope and an atomic force microscope were used for characterizing the structure of the films. The optical band gap of the semiconductor films were extracted from UV-Vis spectral data. The optimum band gap of 1.85 eV for Sb2S3 thin films was obtained by varying the growth time and reaction temperature. This material was employed as a light absorber in a p-i-n junction of P3HT/Sb2S3/ZnO. An efficiency of 0.23% was achieved. The low efficiency was attributed to charge carrier recombination at the defect and trap states in the Sb2S3 layer or between its adjacent interfaces. Moreover the poor interface between Sb2S3 and ZnO nanorods might have resulted in low efficiency. Coating the ZnO nanorods with a thin TiO2 (interfacial) layer increased the efficiency of the device to 0.36%. Cell performance could be improved by optimizing the solution-based deposition processing by controlling reaction time, reaction temperature, and annealing temperature, which may reduce the defect and trap densities at the interfaces or in the intrinsic Sb2S3 thin films.

Library of Congress Subject Headings

Hybrid solar cells
Antimony trisulfide
Zinc oxide
Nanostructures

Description

Includes bibliographical references (pages 100-111).

Format

application/pdf

Number of Pages

123

Publisher

South Dakota State University

Rights

In Copyright - Educational Use Permitted
http://rightsstatements.org/vocab/InC-EDU/1.0/

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