Document Type
Thesis - University Access Only
Award Date
2009
Degree Name
Master of Science (MS)
Department / School
Mechanical Engineering
Abstract
In the process of photovoltaic energy conversion, photons with the energy below the band-gap cannot be absorbed and do not contribute to energy conversion. If these lost photons can be converted to photons with higher energy, and then absorbed and used by the solar cells, the efficiency of the photovoltaic devices may be enhanced. Multi-photon absorption of organic materials has attracted great attention in recent years, especially the two-photon absorption process. Two-photon absorption (TPA) induced fluorescence is one of the approaches that convert low energy incident photons towards higher energy photons via active material. The TP A efficiency of an organic molecule is characterized by TP A cross section. Organic material with large TP A cross-section can be used as the up-converter material to potentially further increase the efficiency of the solar cells. The main advantage of combining solar cells with the up-converter is that it can in principle be applied to most of the existing solar cells. In this paper, quantum-chemical techniques were applied to theoretically investigate one- and two-photon absorption properties of some new molecules with "A" shape. TPA cross-sections of these derivatives were obtained using two-state, three-state, and sum-over-state models, respectively. Geometrical structure of molecule was optimized using Hartree-Fock Theory (HF) and properties of excited states of molecule were obtained based on Configuration Interaction with single excitations method (CIS). The effects of donor, acceptor, and 1t center on the TPA behaviors of the designed molecules were investigated. The study of TP A properties of organic material was also carried out at the experimental level. It was found that several designed molecules have attractive TP A properties. Further work should include improving the TP A properties of these molecules, and verifying the theoretical results by conducting the two-photon excitation (TPE) experiments of these compounds.
Library of Congress Subject Headings
Photoabsorption
Organic compounds
Photovoltaic cells
Solar cells
Electrooptics -- Materials
Format
application/pdf
Number of Pages
99
Publisher
South Dakota State University
Recommended Citation
Wang, Wei, "Theoretical Study of One- and Two-photon Absorption Properties of Organic Conjugated Materials for Photovoltaic Devices" (2009). Electronic Theses and Dissertations. 1615.
https://openprairie.sdstate.edu/etd2/1615
