Ph.D Thesis


Ph.D StudentMoshe Moshonov
SubjectSelf-Assembled Organic Molecules as Metal Oxide Templates
for Hybrid Photovoltaics
DepartmentDepartment of Materials Science and Engineering
Supervisor Full Professors Frey Gitti
Full Thesis textFull thesis text - English Version


Abstract

Hybrid nano-materials, or nanocomposites, are composed of organic and inorganic constituents mixed on the molecular level. These nanocomposite materials are designed to exploit the properties of their individual components and obtain synergetic functionalities that are distinct or unattainable from the separate constituent species. The hybrid desirable functionalities depend on the organic-inorganic interfaces and morphology. Here, we aim to direct and control the morphology and interfacial interactions in a hybrid film through the self-assembly of the organic component which then templates the deposition of the inorganic phase. To do so, we synthesized small molecules and polymers designed to self-organize into supramolecular π-conjugated hierarchical assemblies. The small molecules are composed of donor-acceptor photoactive moieties and use noncovalent interactions to self-assemble into supramolecular assemblies. The self-assembled structures template the polycondensation of metal oxide sol-gel precursors in solution, leading to hybrid films with molecular level control over interfaces, structure, and morphology. The polymer approach utilized the self-assembly of conjugated rod-coil block copolymers into assemblies that are then used as templates for the deposition of metal oxides from the gas phase in an Atomic Layer Deposition (ALD) chamber. The selectivity of one block only to the metal oxide precursors leads to the formation of hybrid films with control over morphology and structure. Furthermore, the self-assembly of the block copolymer was manipulated through its chemical composition or the solvent used for film deposition. This manipulation is translated to the morphology of the organic template and then to the hybrid film morphology. In few cases, the functionality of the directed hybrid film was tested by integration into hybrid photovoltaic devices. Furthermore, chemical modifications to the BCP were introduced and their influence on the ability to direct a metal oxide via ALD was analyzed. Subsequently, we combined the self-assembly of amphiphilic, optically active, organic small molecules into supramolecular assemblies, providing a template for the sol-gel synthesis of a metal oxide. Accordingly, two analogous chromophores contradistinct by merely a methyl group were used, in which the first possess the ability to self-assemble while the other does not. This system demonstrated that the chemical structure of the amphiphilic chromophore can be used to tune the self-assembly and hence the morphology of the hybrid film, and in turn translated directly to opto-electronic properties of the hybrid film.