Thèse doctorat : Micro-ondes et Micro-technologies : Lille 1 : 2003. / N° d'ordre (Lille 1) : 3408. Bibliogr. à la suite de chaque chapitre.

Thèse de doctorat : Electronique : Lille 1 : 2001. / N° d'ordre (Lille) : 2978. Résumé en français et en anglais. Bibliogr. en fin de chapitres.

Tez (Yüksek Lisans) - Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, Fizik Anabilim Dalı, 2007. / Kaynakça var.

Conducting metallopolymers have been investigated for a variety of applications due to their ability to take advantage of both the mechanical processability of the polymer material, as well as the optical and electronic properties of the metal. Our project goal is to design, synthesize and characterize novel iridium(III)-containing conducting metallopolymers for use as the active layer in polymer light-emitting diodes. We have utilized thiophene functionalized ligands that can be readily electropolymerized into conducting polymer thin films and can be easily incorporated into a device structure. Iridium(III) was chosen as the metal center due to its promising photophysical properties, as similar complexes have demonstrated high luminescent quantum yields and short phosphorescent lifetimes. The coordination environment around the metal can be altered synthetically to tune the emission wavelength across the visible spectrum. The synthetic control over the polymer backbone, as well as the iridium(III) ligand environment, allowed us to independently vary each component, which has provided a variety of materials. The materials are characterized through 1H and 13C NMR, mass spectrometry, elemental analysis, electrochemistry, X-Ray diffraction and X-Ray Photoelectron Spectroscopy. The photophysical properties of the materials are studied through UVvii Visible absorption spectroscopy, UV-Vis-NIR spectroelectrochemistry and steadystate/ time-resolved emission spectroscopy. / text

Solution deposition of thin film photovoltaic materials leads to large variations in the morphological and chemical compositions of the film. In order to improve device functionality, it is important to understand how morphology and chemical composition affects charge generation, separation, and collection. This PhD work will first study bulk methods in order to characterize materials in solution and films. The results are then correlated with microscopy studies examining morphology. Other methods used in this PhD work will directly couple spectra and microscopy. Microscopic regions of such films and devices can be illuminated using scanning confocal microscopy or near-field scanning optical microscopy (NSOM), which allows for one to directly probe regions of the film at or below the optical diffraction limit. By scanning the sample over a fixed laser spot we can simultaneously create image maps of the topographical, electrical and optical properties. This technique, known as laser beam induced current (LBIC) allows one to directly probe a local area of a device with 100-300nm resolution. Along with bulk device efficiency studies, near field and confocal data of inorganic and organic materials are investigated. These include devices fabricated with a blend of P3HT (poly[3-hexylthiophene]) and perylene diimide derivatives, and Cu(InxGa1-x)Se2 [CIGS] nanoparticle devices. Finally, we use a new device architecture, a lateral organic photovoltaic (LOPV) in order to spatially resolve transport in functional organic devices. / text

Wide band gap based nanostructures have being attracting much research interest because of their promise for application in optoelectronic devices. Among those wide band gap semiconductors, gallium nitride (GaN) and zinc oxide (ZnO) are the most commonly studied and optoelectronic devices based on GaN and ZnO have been widely investigated. This thesis concentrates on the growth, optical and electrical properties of GaN and ZnO nanostructures, plus their application in solar cells and light emitting diodes (LEDs). GaN-nanowire based dye sensitized solar cells were studied. Different post-growth treatments such as annealing and coating with a TiOx shell were applied to enhance dye absorption. It was found that TiOx increased the dye absorption and the performance of the dye sensitized solar cell. ZnO nanorods were synthesized by vapor deposition and electrodeposition. Post-growth treatments such as annealing and hydrothermal processing were used to modify the defect chemistry and optical properties. LEDs based on GaN/ZnO heterojunctions were studied. The influence of ZnO seed layers on GaN/ZnO LEDs was investigated. GaN/ZnO LEDs based on ZnO nanorods with MgO and TiOx shells were also prepared in order to modify the LED performance. The coating condition of the shell was found to influence the current-voltage (I-V) characteristics and device performance. Moreover, high brightness LEDs based on GaN with InGaN multiple quantum wells were also fabricated. The origin of the emission from GaN/ZnO LEDs was studied using different kinds of GaN substrates. Direct metal contacts on bare GaN substrates were also employed to investigate the optical emission and electrical properties. It is found that the emission from the GaN/ZnO LEDs probably originated from the GaN substrate. GaN/ZnO LEDs with MgO as an interlayer were also fabricated. The MgO layer was expected to modify the band alignment between the GaN and the ZnO. It was shown that GaN/MgO/ZnO heterojunctions (using both ZnO nanorods and ZnO films) have quite different emission performance under forward bias compared to those that have no MgO interlayer. An emission peak was around 400 nm could originate from ZnO. Nitrogen doped ZnO nanorods on n-type GaN have been prepared by electrodeposition. Zinc nitrate and zinc acetate were used as ZnO precursors and NH4NO3 was used as a nitrogen precursor. Only the ZnO nanorods made using zinc nitrate showed obvious evidence of doping and coherent I-V characteristics. Cerium doped ZnO based LEDs were fabricated and showed an emission that depended on the cerium precursor that was employed. This indicates that the choice of precursor influences the growth, the materials properties and the optical properties of ZnO. / published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Over the last decade, many significant developments have been made to improve the active materials in a new generation of organic light emitting devices (OLEDs). Current OLED technology is focused on organo-transition metal complexes, which emit from the triplet excited state and exhibit bright phosphorescence. Efficient in devices have been reported using these luminescent materials, such as iridium and platinum complexes, however, rare metal abundance concerns, high price and toxicology have inspired the study of alternative phosphorescent materials, such as copper or silver complexes. In this research, novel copper complexes have been synthesized, such as trinuclear and mononuclear copper (I) complexes, using a range of ligands, such as alkynyl, phosphine alkynyl and pyridine ligands. The synthesised complexes have been characterised by with a range of techniques, such as UV/Vis absorption and emission spectroscopy, nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), cyclic voltammetry (CV) and scanning electron microscopy (SEM). Most of the copper complexes have shown very interesting luminescent properties in solution and solid state and some of them were studied for future application in a device.

Controlled patterning of light emitting diodes on semiconductors enables a vast variety of applications such as structured illumination, large-area flexible displays, integrated optoelectronic systems and micro-total analysis systems for real time biomedical screening. We have demonstrated a series of techniques of creating quantum-based (QD) patterned inorganic light emitting devices at room temperature on silicon (Si) substrate. In particular: (I) A combination of QDs self-assembly and microcontact printing techniques were developed to form the light emission monolayer. We expand the self-assembly method with the traditional Langmuir-Schaeffer technique to rapidly deposit monolayers of core: shell quantum dots on flat substrates. A uniform film of QDs self-assembled on water was transferred using hydrophobic polydimethylsiloxane stamps with various nano/micro-scale patterns, and was subsequently stamped. A metal oxide electron transport layer was co-sputtered onto the QDs. The structure was completed by an e-beam evaporating thin metal cathode. Multicolor light emission was observed on application of voltage across the device. (II) We also demonstrate the photolithographic patterning capability of a metal cathode for top emitting QDLEDs on Si substrates. Lithographic patterning technique enables site-controlled patterning and controlled feature size of the electrode with greater accuracy. The stability of inorganic silicon materials and metal oxide based diode structure offers excellent advantages to the device, with no significant damage observed during the patterning and etching steps. Efficient electrical excitation of QDs was demonstrated by both the methods described above. The technique was translated to create localized QD-based light sources for two applications: (1) Three-dimensional scanning probe tip structures for near field imaging. Combined topographic and optical images were acquired using this new class of “self-illuminating” probe in commercial NSOM. The emission wavelength can be tuned through quantum-size effect of QDs. (2) Multispectral excitation sources integrated with microfluidic channels for tumor cell analyses. We were able to detect the variation of sub-cellular features, such as the nucleus-to-cytoplasm ratio, to quantify the absorption at different wavelength upon the near-field illumination of individual tumor cells towards the determination of cancer developmental stage. / text

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy