Author: Ching-Ching Oey

Publisher:

Published: 2017-01-26

Total Pages:

ISBN-13: 9781361070819

This dissertation, "Organic-inorganic Nanocomposites for Organic Optoelectronic Devices" by Ching-ching, Oey, 黃晶晶, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Organic - Inorganic Nanocomposites For Organic Optoelectronic Devices Submitted by Oey Ching Ching for the degree of Master of Philosophy at The University of Hong Kong in August 2005 Interest has been growing in the past few years in incorporating inorganic nanostructures into organic optoelectronic devices. These hybrid organic - inorganic nanocomposite systems are being studied more closely because it is possible to combine the desirable characteristics of organic and inorganic components within a single composite and their properties can be easily changed by varying the material composition, shape of the nanostructures, and concentration and size of the nanoparticles in the composites to match the device requirement. More importantly, they can retain the fabrication advantages of organic devices, i.e., easy processing, low production and material cost, and manufacture of devices on large and flexible substrates, which are very important factors for application and commercialization purposes. Therefore, developing improved performance in organic light emitting diodes (OLEDs) and organic solar cells by incorporating inorganic nanostructures in the organic materials has become an important topic of research. For OLEDs, modification of the commonly used indium tin oxide (ITO) anode is an active research area because bare ITO has a number of shortcomings. Different buffer layers on top of ITO have been reported to be useful in enhancing the device performance. In this work, blends of poly(3,4, -ethylene dioxythiophene): polystyrene sulfonic acid (PEDOT: PSS) polymer and different inorganic nanostructures: Ni nanoparticles, Cu nanoparticles, NiO nanoparticles and single-walled carbon nanotubes (SWCNTs) were investigated as the hole injection layers respectively for OLEDs based on a tris-(8-hydroxyquinoline) aluminum (Alq )/ 3N, N-di(naphthalene-1-yl)-N, N-diphenyl-benzidine (NPB) system. These novel nanocomposite OLEDs with different concentrations of inorganic nanostructures were fabricated and characterized by electroluminescence and current-voltage measurements. Experimental results showed that the addition of Ni nanoparticles and SWCNTs (with appropriate surfactants used in dispersing SWCNTs) resulted in improved OLED performance for optimized nanoparticle concentration compared to the devices with pure PEDOT: PSS. The PEDOT: PSS: Ni and PEDOT: PSS: SWCNTs layers were characterized by atomic force microscopy, absorption measurements and spectroscopic ellipsometry. The reasons for the improved OLED performance are also discussed. For organic solar cells, with the control of the nanostructure morphology, metal oxides are believed to act as promising alternatives as the electron acceptor and transporter in bulk-heterojunction device structure. In this work, bulk-heterojunction solar cells based on poly (2-methoxy-5-(2''-ethyl-hexyloxy)-p-phenylene vinylene) (MEH-PPV) and a highly porous TiO layer consisting of a 3D interconnected network of anatase crystallites were fabricated and characterized by white light efficiency and external quantum efficiency measurements. The influence of different treatments on ITO/porous TiO substrates and the use of different solvents for 2 spin-coating MEH-PPV, MEH-PPV layer thickness and device architecture on the solar cell device performance were studied. It was found that the optimized device structure is ITO/TiO (compact, 20 nm)/Ti