Molecular design of organic/inorganic hybrids for solar energy conversion
Creators: name: Heidari, Marzieh
Publisher: name: No Publisher Supplied
Year: 2024

description: This thesis comprises four chapters and three distinct research projects. Chapter 1 of this dissertation provides an introduction and background on solar energy conversion and storage systems, such as Dye-Sensitized Photoelectrosynthesis Cells (DSPECs) and Dye-Sensitized Solar Cells (DSSCs). It offers an overview of the components and application of dye molecules for sensitizing metal oxide (MOx) electrodes in DSSCs and DSPECs. Furthermore, it provides details on MOx electrodes and electron transfer processes occurring in these devices, which can potentially enhance or reduce their efficiency. Chapter 2 describes the first project, in which we explored how the structure of anchor groups forming covalent bonds to nanostructured semiconductors influences the binding of light harvesters to mesoporous TiO2 thin films. Specifically, we introduced a third coordination unit (X) into isophthalic acid derivatives (2-hydroxyisophthalic acid, 2,6-dicarboxypyridine, and 2,6-dicarboxypyridin-1-ium) and studied their effects, along with 1-ethynylpyrene as a chromophore, both in solution and on mesoporous TiO2 thin films.The introduction of X at C2 of isophthalic acid had significant implications for Highest Occupied Molecule Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energies, orbital’s electron distributions, and binding strength to TiO2 films.Chapter 3 describes the second project. In this project, a family of ruthenium-based rigid rods were anchored to mesoporous Indium Tin Oxide (ITO) nanocrystal films. These compounds featured different numbers of conjugated phenylacetylene units in the bridge that is between the ruthenium complex and a 1,3-dicarboxylate isophthalic anchoring group. Our investigations revealed that the presence of phenylacetylene bridge units had minimal impact on redox properties and visible light absorption spectra, but greatly influenced injection rates. The rate of electron transfer from ITO to the rigid rods was measured by tuning the Gibbs free energy change (-ΔG°), with pseudo-rate constants increasing as the length of bridge decreases. These findings provided insights into reorganization energy (λ) and electronic coupling matrix element (Hab) variations and their potential impact on solar energy conversion applications. This project was conducted in collaboration with Dr. Gerard J. Meyer’s group at the University of North Carolina-Chapel Hill. The focus of this thesis is on the synthesis of ruthenium complexes used in this study. The kinetic data were collected and analyzed by Quentin Loague in Dr. Meyer’s group at University of North Carolina-Chapel Hill and are briefly mentioned in this thesis.Chapter 4 summarizes the third project, which explores the influence of Self-Assembled Monolayers (SAMs) formed from disulfide lipoic acid-based compounds on Ag electrodes to improve the durability and efficiency of optoelectronic devices. These compounds offer double binding sites, potentially enhancing device performance compared to conventional thiol compounds that attach to the surface through a single site. By fabricating inverted organic semiconducting hole-only devices, we studied the influence of SAM structure on charge injection in the presence of (±)-α-lipoic acid, (±)-4-phenylbutyl 5-(1,2-dithiolan-3-yl) pentanoate, and iso-lipoic acid, which is an achiral form of lipoic acid. These SAMs can potentially enhance charge injection by altering the Ag work function or modifying the interaction between the metal surface and the polymer. This research details how SAM functional groups and bonding interactions influence the performance of organic semiconductor devices. Device performance studies were conducted in Dr. Deidre M. O’Carroll’s group at Rutgers University-New Brunswick.These projects contribute to the understanding of various aspects of Interfacial Electron Transfer (IET), metal oxide/metal electrodes, molecular design, and device optimization for energy conversion and storage applications.