Zero-dimensional and one-dimensional nanostructured materials for application in photovoltaic cells.

摘要

Zero-dimensional materials such as quantum dots and one-dimensional materials such as nanorods and nanowires have attracted significant attention in the past two decades and have been demonstrated as important building blocks for numerous electronic and optoelectronic device applications. Of course, the starting place for the field is the ability to grow various nanomaterials in different morphologies. In this thesis, we have demonstrated successful synthesis of both quantum dots and nanowires belonging to a totally new material class and have subsequently utilized them for photovoltaic cells in different device architectures. Apart from the photovoltaic cells, we have demonstrated a scalable way to fabricate carbon nanotube devices with a high on-off ratio on a wafer scale.;This dissertation describes the above-mentioned aspects in detail and accordingly consists of seven chapters. Following an overview and an introduction of fundamental knowledge of zero-dimensional and one-dimensional nanostructured materials in Chapter 1, Chapter 2 discusses synthesis of vertically aligned array of single crystalline TiO2 nanowires and their use in traditional dye-sensitized solar cells.;Chapter 3 discusses the continued work on TiO2 nanowire cells where we employ novel nanoparticles as sensitizers and demonstrate their advantages over traditional dye molecules.;Chapter 4 address the issue of liquid based electrolytes in the solar cell and proposes a novel physical vapor deposited hole transport material to replace the liquid electrolyte and thus paving a way for solid-state dye sensitized solar cell.;Chapter 5 deals with an important issue of ITO replacement for solar cells. Researchers have been very actively looking for materials that can work as transparent and conductive electrodes. We demonstrate the viability of silver nanowire based random network film as a potential replacement. We achieve remarkable performance in terms of sheet resistance and transparency which rivals that of ITO, supporting a very strong case for Ag nanowire film.;In chapter 6, we demonstrate a scale way to fabricate carbon nanowtube devices with high on-off ratio (a critical requirement for logic devices) by converting metal nanotubes to semiconducting ones. This conversion is realized using exposure of asgrown nanotubes to a broad band light source which induces photochemical reactions. We demonstrate a high device yield of 82%.;Finally in chapter 7, we conclude by discussing the future directions and work that needs to be done in order to carry forward the advance made in this thesis.