M.Sc Thesis


M.Sc StudentEyal Aharon
SubjectHybrid Photovoltaic Devices
DepartmentDepartment of Materials Science and Engineering
Supervisor Full Professors Frey Gitti


Abstract

Room temperature solution-processing of conductors and semiconductors provides the means to fabricate large area optoelectronic devices at very low cost. Conjugated polymers have unique physical properties as a result of π type bonds. The band gap in conjugated polymers, i.e. the gap between HOMO and LUMO, is derived from those π electrons and is in range of 1.5 eV-3.5 eV. Hence, conjugated polymers have semi-conductive properties. Processing inorganic materials from solution, on the other hand, is less developed. In this work we demonstrate the integration of solution-processed inorganic films in polymer light-emitting diodes and photovoltaic devices to form fully solution processed multilayer hybrid devices. Thin platelets of the inorganic semiconducting layered material SnS2 are obtained. These platelets self-assemble into oriented thin films on ITO substrates. The SnS2 film is spun onto semiconducting polymer film and a device is completed by evaporating metallic electrode. The hybrid device structure is: Glass/ITO/MEH-PPV/SnS2/Cathode, thus the energy levels offset at the polymer/inorganic heterojunction is designed to enhance charge separation in photovoltaic devices.

The research was divided into four main parts: microstructure analysis, optical characterization, electrical characterization and statistical analysis. Finally it was able possible to correlate the microstructure to the electrical characterizations and optimize the cell's performance. The microstructure, optical and electrical characterization of the films and the interface between them were studied using HRSEM, EDS, XRD and optical absorption. The cathodes examined were Au, Al and Ca. By correlating the device output with the film characteristics it was possible to associate the device performance with the quality of the organic/inorganic