Ph.D Thesis

Ph.D StudentTamar Segal-Peretz
SubjectPhoto-Current Generation in Hybrid Organic-Inorganic
Photovoltaic Devices
DepartmentDepartment of Nanoscience and Nanotechnology
Supervisor Full Professors Frey Gitti
Full Thesis textFull thesis text - English Version


Hybrid films of organic-inorganic donor-acceptor materials are considered promising for low cost, solution processed solar cells because they combine the unique properties of inorganic semiconductors with the film forming properties of organic materials. In particular, metal oxide-conjugated polymer solar cells have been widely explored as organic-inorganic donor-acceptor photovoltaic pair. Nevertheless, although many metal oxide-conjugated polymer hybrid solar cells have been demonstrated, the origin of charge generation and the role of the hybrid interface in these devices are not understood well enough. In hybrid solar cells, the device performance is extremely sensitive to the nano-morphology; therefore, one of the main challenges in these systems is to manipulate the organic and inorganic phases into nanoscale and mesoscale morphologies which allow charge collection and charge transport to the electrodes.

In this research, this challenge is achieved by combining sol-gel chemistry and block copolymer (BCP) self-organization to co-assemble ruthenium dyes, conjugated polymer and titania precursor into hierarchical 3D mesostructure hybrid films, with highly ordered morphology and sub-20 nm periodicity. Importantly, judicious selection of the ruthenium dye and the conjugated polymer enable the control over the chemical composition and interfacial interactions at the hybrid interface, as confirmed by FTIR, energy filtered TEM, and solid-state NMR spectroscopy. These molecular level interactions are reflected at the macroscopic behavior of photovoltaic devices based on conjugated polymer-dye-titania mesostructure films. The highly uniform and ordered donor-acceptor structures are also used to study fundamental exciton dissociation processes at the hybrid interface through contactless time resolved microwave photoconductivity (TRMC) analysis. The correlation between the nano-scale chemical composition of the multicomponent interface and the macroscopic film performance can lead to better design of BCP-directed metal oxide mesostructures and other hybrid structured materials.