Liposomes are versatile biocompatible and biodegradable carriers for a variety of medical applications. As the first nanoparticles, they have been approved for pharmaceutical use so far, and many liposome-based preparations are in clinical trials. Classical methods of liposome preparation represent potential limitations in technology transfer from laboratory to industrial scale. New, microfluidic techniques overcome these limitations and offer new possibilities for controlled, continuous preparation of liposomal particles in a laboratory and industrial scale. An important element in the development of new nanoparticle systems is their complex characterization and purification. In addition to the established chromatographic techniques, the Field flow fractionation technique, in particular the Asymmetrical flow Field-flow fractionation, is described. This relatively new technique in conjunction with the MALS/DLS/DAD-UV/dRI online detectors enables the purification and characterization of complex samples. The main advantage of this technique lies in the possibility of separation under native conditions, which plays an important role in the separation of biopolymers in particular. Separation in the “empty” channel then eliminates sample degradation due to unwanted interactions at the stationary phase-sample interface. The theoretical part of this thesis describes the possibilities of preparation, modification, and characterization of liposomal nanoparticles. For this purpose, optical methods based on dynamic light scattering, multi-angle dynamic light scattering and nanoparticle tracking analysis techniques are described, as well as a non-optical method using "particle by the particle" analysis, tunable resistive pulse sensing method. A separate chapter of the theoretical part is dedicated to the technique Asymmetrical flow Field-flow fractionation in connection with the above-mentioned detectors. Important results associated with this work are summarized in the attached scientific paper, together with the result summaries and the author's contributions.

This master thesis deals with study of chitosan-lignohumate, chitosan-polystyrenesulfonate, chitosan-alginate and chitosan-carrageenan polyelectrolyte complexes. The work was motivated by research of finding suitable alternative substance for lignohumate. The molecular weights of substances were characterized using SEC-MALLS. A degree and a character of the interactions between polyelectrolyte were studied by isothermal titration calorimetry and dynamic light scattering method. The calorimetric experiments proved that decreasing concentration of samples causes decreasing of heat flow. The best calorimetric measurements were provided by adding chitosan into polymer solution. The interactions between chitosan and polyanions and influence of mixing order were proved also by measuring intensity of zeta potential, Z-average of particle size and turbidity. New chitosan-based materials have a big potential in agriculture and medicine.

This diploma thesis deals with the utilization of physico-chemical analysis in study on microbial stress–response. The main content of this work was to propose and optimize techniques and methods which are generally used in different industries. Two bacterial strains, Cupriavidus necator H16 and its mutant strain Cupriavidus necator PHB-4 producing polyhydroxyalkanoates (PHA) under certain conditions, were used as model microorganisms. Initially, microscopic teques such as transmission electron microscopy (TEM), cryo scanning electron microscopy (cryo SEM) and atomic force microscopy (AFM) were proposed and tested for the characteriozation of morphological differences of bacteria. Furthermore, viscoelastic properties of bacteria were determined and compared by the oscillatory tests of the rheology method considering another type of samples. Thermal analysis methods, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) in particular, focused on water transport and behavior of intracellular water influenced by presence of the granules of PHB in bacteria. The last technique, utilized in the study, was dynamic and electrophoretic light dispersion during pH changes for characterization of the surface properties of bacteria such as size, zeta potential and the isoelectric point.

This diploma thesis is focused on the determintaion of viscoelastic properties of agarose hydrogels containing different polyelectrolytes by microrheological and macrorheological techniques. From microrheological techniques the dynamic light scattering was used. Firstly, the influence of different polyelectrolyte volume was studied. Then the effect of variously charged polyelectrolyte and ionic strenght on microrheological properties of agarose hydrogels were determined. Classic rheology was used to compare the results obtained using the DLS microrheology method. Finally, the results from macro- and microrheology were correlated with each other.

First artificial PHB granules were prepared under the terms of this thesis. The effect of used PHB solvent, ultrasonic bath temperature and time, solvent evaporation temperature and stabilizing agent nature was investigated using dynamic and electrophoretic light scattering. The most proper parameters were demonstrated at samples which were prepared by dissolving of PHB in chloroform, stabilizing with CTAB or lecithin, ultrasonifying at 35 °C followed by chloroform evaporating at 60 °C. Based on ATR-FTIR and Raman spectroscopy results, it was found out that PHB within the artificial granules were in crystalline form. The native PHB granules were isolated from Cupriavidus necator using either lysosyme, deoxyribonuclease and cell disruption by ultrasonification or digestion with alcalase, SDS and EDTA. Granules obtained by both isolation procedures were characterized by ATR-FTIR, Raman spectroscopy, light scattering techniques and DSC. According to the analyses results, the second mentioned procedure turned out to be more effective for obtaining the polymer in amorphous state. Furthermore, the polymer within granules recovered by using this procedure was thermally more stable. Last but not least, the native PHB granules samples were exposed to effect of acetone, lipase and sodium hypochlorite, assuming that polymer crystallinity should be increased by these chemicals in varying degrees. The highest degree of crystallinity was achieved after their treatment with lipase.

This master thesis is dealing with the use of light scattering techniques in the study on formation of polyelectrolyte complexes in the system biopolymer-surfactant. Sodium hyaluronate was chosen as biopolymer and cetyltrimethylammonium bromide and karbethopendecinium bromide were selected as surfactants. The first precipitation experiments were performed to determine the optimal concentration range of surfactants for subsequent titration measurements performed on Zetasizer Nano ZS and for SEC-MALS analysis. The key parameters obtained from these measurements were the values of critical aggregation concentrations in hyaluronate-surfactant systems. It was found out that the increasing molecular weight of hyaluronan in these systems is causing reduction of obtained values of critical aggregation concentrations. Changes of Z-average particle size, zeta potential, polydispersity index, conformation plot, radius of gyration and molecular weight in the hyaluronan-surfactant system were monitored during experiments.

Les structures immergées telles que des hydroliennes génèrent des écoulements turbulents pouvant fortement perturber les fonds marins. La compréhension de l’impact de la présence de ces structures nécessite de comprendre la dynamique tridimensionnelle des tourbillons qu’elles génèrent. Les méthodes optiques, par leur aspect non intrusif, permettent d’analyser de telles dynamiques. L’imagerie interférométrique en défaut de mise au point est une technique développée à l’originepour la mesure de taille de particules sphériques transparentes telles que des gouttes ou des bulles. Nous proposons ici l’extension de cette technique à la mesure simultanée de particules irrégulières et sphériques. Un premier montage expérimental a permis de valider la méthode pour la mesure de taille et de position tridimensionnelle de grains de sable et de bulles d’air dans l’eau. Un second dispositif a été réalisé sur un canal à houle de plus grandes dimensions, permettant d’introduire les notions de suivi tridimensionnel de particules irrégulières et d’analyse de variation de leur orientation. Un troisième montage composé de deux dispositifs d’imagerie interférométrique selon deux angles d’observations est utilisé pour la reconnaissance de forme de différentes familles de particules irrégulières. Grâce à des comparaisons avec des simulations, les dimensions et l’orientation de ces particules sont déterminées. Ce type de montage devrait être adapté à la caractérisation de cristaux de glace dont divers types de formes sont connus. Ces travaux ouvrent des perspectives pour l’extension de la technique aux mesures de vitesses de particules dans des écoulements hostiles, combinées avec la reconnaissance de forme et la détermination de la rotation de particules. / Submerged structures such as tidal turbines generate turbulent flows that can strongly disrupt the seabed. Understanding the impact of the presence of these structures requires understanding the three-dimensional dynamics of the vortices they generate. Optical methods, by their non-intrusive aspect, make it possible to analyze these dynamics. Interferometric Particle Imaging is a technique originally developed for the measurement of transparent spherical particles such as droplets orbubbles. We offer here an extension of this technique for the simultaneous characterization of irregular and spherical particles in a flow. A first experimental set-up has confirmed the validity of the method for the size and three-dimensional position measurement of grains of sand and air bubbles in water. A second device was used on a wave flume of bigger dimensions, introducing the notions of three-dimensional tracking of irregular particles and the analysis of the variation of their orientation.A third device made of two Interferometric Particle Imaging set-ups at two angles of observation is described for the shape recognition of different families of irregular particles. Through comparisons with simulations, dimensions and orientations of these particles are determined. This kind of device should be suitable for the characterization of ice crystals for which various shapes are known. The prospects that such results provide include the extension of the technique to the particle velocitymeasurement in hostile conditions, combined with the shape recognition and the determination of rotation of particles.

Les particules de suie, issues de la combustion incomplète, peuvent, en fonction des conditions de combustion, contenir une part plus ou moins importante de composés organiques (OC/TC). Par ailleurs, dès lors que ces nanoparticules sont émises dans l'atmosphère, des composés organiques volatiles peuvent s'adsorber, formant une gangue autour de ces agrégats fractals. L'impact de cette composition initiale ou de ce « vieillissement atmosphérique » sur les propriétés morphologiques et radiatives de ces particules n'est pas bien connu. Ceci a un impact sur les modèles radiatifs climatiques mais aussi sur l'interprétation des signaux délivrés par les différents diagnostics optiques pouvant être utilisés pour la métrologie des aérosols. En particulier, ce travail vise à juger de la pertinence de l'usage de diagnostics optiques pour caractériser les particules de suie en conditions atmosphériques. Afin d'étudier l'impact des composés organiques initialement présents dans la particule ou adsorbés en post-combustion sur leurs propriétés radiatives, nous avons étudié en laboratoire des suies produites par une flamme de diffusion (miniCAST) pour différentes richesses globales et avons ajouté un revêtement organique d'acide. Dans le but de générer en laboratoire une couche d'acide oléique sur des particules de référence, un dispositif de « coating » a été mis en œuvre et qualifié. Les particules ainsi générées et recouvertes ou non, ont été caractérisées en masse (mesures TEOM), en taille (mesures SMPS) et morphologiquement (densité effective). L'épaisseur de coating ainsi que la restructuration morphologique causée par l'ajout d'une gangue de matière organique ont ainsi été quantifiées. Les propriétés radiatives, ont été mesurées par extinction spectrale (Turbidimétrie) et diffusion (diffusion angulaire et spectrale). Un effort particulier a été mené pour que des mesures expérimentales puissent valider des résultats de calculs numériques préexistants. Par ailleurs, ces différentes techniques de mesures (optiques et non optique) ont conduit à la généralisation de la théorie Rayleigh Debye Gans for Fractal Aggregates (RDG-FA) à des particules de type agrégats fractals polydispersés recouverts d'un revêtement organique (RDG-CFA). Ceci permettant d'appréhender de façon phénoménologique l'impact du coating sur les propriétés radiatives et d'entrevoir une implantation plus aisée dans les codes de simulation climatique ou pour l'interprétation des mesures optiques dans l'atmosphère. Enfin, une attention particulière a été portée sur la technique d'incandescence induite par laser (LII) afin d'étudier la faisabilité de l'application de cette technique aux particules organiques ou ayant interagi avec les composés atmosphériques au cours de leur vieillissement. / Soot particles resulting from incomplete combustion may contain a more or less important part of organic compounds (OC / TC), depending on the combustion conditions. Moreover, once these nanoparticles are emitted into the atmosphere, volatile organic compounds can adsorb, forming a coating around these fractal aggregates. The impact of the initial composition or the atmospheric aging on the morphological and radiative properties of these particles is not well known. This has an impact on the radiative climate models but also on the interpretation of the signais delivered by the different optical diagnostics that can be used for aerosol metrology. In particular, this work aims to evaluate the relevance of the use of optical diagnostics to characterize soot particles in atmospheric conditions. In order to study the impact of organic compounds initially present in the particle or adsorbed in post-combustion on their radiative properties, we have studied soot produced by a diffusion flame (miniCAST) for different global richnesses and added an organic acid coating. In order to produce an oleic acid layer on reference particles, a coating device has been implemented and qualified. Particles thus generated, coated or not, were characterized in mass (TEOM measurements), in size (SMPS measurements) and morphologically (effective density). The coating thickness as well as the morphological restructuring caused by the addition of an organic coating was thus quantified. The radiative properties were measured by spectrally resolved light extinction and scattering (angular and spectrally resolved). A special effort was made to allow experimental measurements to validate pre-existing numerical results. Moreover, these different measurement techniques (optical and non-optical) have led to the generalization of the Rayleigh Debye Gans for Fractal Aggregates (RDG-FA) theory to particles of the polydispersed fractal aggregate type coated with an organic layer (RDG-CFA). This allows to understand phenomenologically the impact of a coating on the radiative properties and to permit an easier implementation in climate simulation codes or for the interpretation of optical measurements in the atmosphere. Finally, special attention was paid to the laser induced incandescence technique (LII), to study the applicability of this technique to organic particles or having interacted with atmospheric compounds during their aging processes.

Organische, lichtemittierende Dioden (OLEDs) bezeichnen neuartige Lichtquellen, welche zur Beleuchtung oder für Displayanwendungen nutzbar sind. Im Allgemeinen ist die Lichtausbeute durch den hohen Brechungsindex und die Dünnschichtgeometrie der OLED begrenzt. Der hohe Brechungsindex sorgt dafür, dass ein signifikanter Anteil des emittierten Lichts in der OLED durch Totalreflexion (TIR) gefangen ist. Durch den Dünnschichtaufbau der OLED wird außerdem die Lichterzeugung für resonante Moden der kohärenten optischen Mikrokavität erhöht. Dies gilt im Besonderen für die nichtstrahlenden Moden. In dieser Arbeit wurden zwei Methoden untersucht, um die Lichtausbeute aus OLEDs zu erhöhen. Zuerst wurde die Implementierung von Materialien mit niedrigem Brechungsindex angrenzend zum undurchsichtigen metallischen Rückkontakt untersucht. Die Modifizierung des Brechungindexes verändert die Dispersionsrelation der an der Grenzfläche zwischen Metall und Dielektrikum angeregten nicht-strahlenden Oberflächenplasmonpolariton-Resonanz (SPP). Dadurch wird der Phasenraum verkleinert, in welchen effizient Strahlung abgegeben werden kann. Da die SPP-Resonanz eine nichtstrahlende Verlustquelle der Mikrokavität darstellt, wird so die Auskopplungseffizienz der OLED erhöht. In experimentellen Umsetzungen konnte die externe Quanteneffizienz (EQE) sowohl für einen Emitter gesteigert werden, welcher eine isotrope Verteilung der Strahlungsquellen besitzt (Ir(ppy)3 , +19 %), als auch für eine vorzugsweise horizontale Ausrichtung (Ir(ppy)2 (acac), +18 %). Die Steigerung der EQE korrespondiert sehr gut mit der berechneten Steigerung der Auskopplungseffizienz für die jeweiligen Mikrokavitäten (+23 %, bzw. +19 %). Weitere optische Simulationen legen den Schluss nahe, dass dieser Ansatz ebenso für perfekt horizontale Ausrichtung der Quellen sowie für weiße OLEDs anwendbar ist. Als zweiter Ansatz wurde die erhöhte Lichtausbeute durch Bragg-Streuung an periodische Linienstrukturen untersucht. In dieser Arbeit wurden Methoden untersucht, bei denen die Oberflächen strukturiert wurde, auf welche die organischen Halbleiterschichten der OLEDs aufgebracht wurden. Für bottom-OLEDs (durch ein Substrat emittierende OLEDs), wurde direkt die transparente Elektrode durch ein Laserinterferenzablationsverfahren (DLIP) modifiziert. Zusätzlich wurden top-OLEDs untersucht (direkt aus der Mikrokavität Licht emittierende OLEDs), für welche alle Schichten auf eine periodisch strukturierte Photolackschicht aufgedampft wurden. Für die bottom-OLEDs konnte für eine Gitterkonstante von 0.71 μm eine Steigerung der EQE um 27 %, verglichen zu einer optimierten unstrukturierten Referenz, ermittelt werden. Eine Vergrößerung der Gitterkonstante führt zu einer Abnahme der EQE. Die erhöhte EQE wird auf die Überlagerung des planaren Emissionsspektrums mit Beiträgen von Bragg-gestreuten, ursprünglich nicht-strahlenden Moden zurückgeführt, wobei die Intensitäten der Anteile von der Gitterkonstante und der Strukturhöhe abhängen. Für die top-OLEDs konnte eine Steigerung der EQE um 13 % für eine Gitterkonstante von 1.0 μm festgestellt werden. Im Gegensatz zu den bottom-OLEDs wird für kleinere Gitterkonstanten (0.6 μm) hier die EQE nicht erhöht. Vielmehr kommt es durch die starke Veränderung des Emissionsspektrums zu einer Erhöhung der photometrischen Lichtausbeute um 13.5 %. Die starke Veränderung des Emissionspektrums wird auf eine kohärente Kopplung zwischen den Bragg-gestreuten Moden zurückgeführt, bedingt durch die starke optische Mikrokavität dieses OLED-Typs. Um diese Effekte quantitativ zu beschreiben, wurde ein entsprechendes Modell entwickelt und implementiert. Die Qualität der Simulationsergebnisse wird anhand von Literaturreferenzen überprüft, wobei eine gute Übereinstimmung zu experimentell gemessenen Spektren erzeugt wird. Mit dem Simulationsmodell werden Vorhersagen über das Emissionspektrum und die resultierenden Effizienzen möglich. Für bottom-OLEDs wurde festgestellt, dass eine starke Veränderung des Emissionspektrums für Gitterkonstanten unterhalb von 0.5 μm erzeugt werden kann. Hingegen sind für top-OLEDs sehr schwache Strukturen oder große Gitterkonstanten notwendig, um eine nur schwache Veränderung des Emissionsspektrums und damit einen allgemeinen Effizienzgewinn zu erzeugen. Bezüglich der Gitterkonstante, ist diese Erkenntnis ist im Gegensatz zur üblichen Herangehensweise zur Implementierung periodischer Streuschichten in OLEDs. Mit der implementierten Simulationsmethode werden jedoch Aussagen bzgl. Emissionspektrum und Effizienz für eine breite Spanne an OLED-Strukturen vor der experimentellen Umsetzung möglich.:1. Introduction 1.1. Motivation 1.2. Scope and outline of this work 2. Organic light emitting diodes - basic concepts 2.1. Amorphous organic semiconductors – electronic properties and transport of charge carriers 2.2. Charge injection into organic semiconductors 2.3. Doping of organic semiconductors and the p-i-n concept for OLEDs 2.4. Charge carrier recombination mechanisms 2.4.1. Displaced harmonic oscillator model for the photoluminescence spectrum of organic emitters 3. OLEDs from thin homogeneous films - theoretical introduction into the optics 3.1. Maxwell’s equations 3.1.1. Boundary conditions 3.1.2. Poynting’s theorem, energy density, and energy flux density 3.2. Optics of thin planar films 3.2.1. Plane waves solution for the homogeneous Maxwell’s equations 3.2.2. Transfer-matrix formalism 3.3. Radiation from electric dipoles embedded into stratified media 3.4. Remarks on the normalized power dissipation 3.5. Description of outcoupled light as resonances 3.6. Basics of optimizing efficiency of OLEDs 3.6.1. Efficiencies for OLED characterization 3.6.2. Optimization of light outcoupling of OLEDs 3.6.2.1. Optimization of the basic cavity layout 3.6.2.2. Optimization of the emitter distribution 3.6.3. Enhancing OLED efficiency beyond the planar limit 4. Experimental fabrication and characterisation methods 4.1. Fabrication methods for organic semiconductors 4.2. Electrical and optical characterisation 4.3. Experimental realization of periodic corrugated surfaces 5. Enhancing the outcoupling efficiency by introducing low-refractive index layers 5.1. Dispersion relations of surface plasmon polaritons in thin film optical microcavities 5.1.1. Bulk surface plasmon polaritons 5.1.2. Coupled surface plasmon polariton states for thin film geometries 5.2. Theoretical potential for outcoupling enhancement due to low refractive index interlayers 5.3. Experimental validation for top-emitting OLEDs with isotropic or anisotropic green phosphorescent emitter 6. Bragg scattering for improved light outcoupling from OLEDs 6.1. Field expansion for periodic photonic crystals 6.2. Bragg scattering in weakly periodically perturbed bottom-emitting monochrome OLEDs 6.2.1. Device details and experimental characterization 6.2.2. Quantitative assignment of Bragg scattering effects within electroluminescence spectrum 6.3. Bragg scattering in top-emitting monochrome OLEDs 6.3.1. Device details and experimental characterization 6.3.2. Analysis of electroluminescence spectrum and description of scattered light from resonance model 6.4. Simulation of the spectral radiant intensity for periodically corrugated OLEDs 6.4.1. Theoretical flowchart 6.4.2. Preliminaries and source representation 6.4.2.1. Plane wave expansion and z-depended field coefficient representation 6.4.2.2. Pseudo-periodic polarization source 6.4.2.3. Solution to the inhomogeneous Maxwell’s equations for a pseudo-periodic source 6.4.3. Field propagation and scattering matrix 6.4.3.1. Reducing the Maxwell’s equation 6.4.3.2. Representation-transformation matrices 6.4.3.3. Formulation of transfer-matrix formalism for periodically perturbed media 6.4.3.4. Iterative calculation of the scattering matrix in plane wave basis 6.4.4. From electromagnetic fields to measurement 6.4.4.1. Far-field solutions in superstrate/substrate media 6.4.4.2. System matrix for pseudo-periodic sources within periodically corrugated cavity 6.4.4.3. Radiant intensity from far-field solutions 6.4.4.4. Treatment of incoherent thick superstrate and substrate 6.4.4.5. Including electroluminescence spectra of organic emitter materials 6.5. Simulation of light emission from emitters embedded into periodically perturbed microcavities 6.5.1. Comparison to experimental data and existing simulation approaches 6.5.2. Simulated light emission for periodically perturbed microcavities 6.5.2.1. Simulation of light emission from corrugated bottom-emitting OLEDs 6.5.2.2. Comparing simulation to experiment for top-emitting OLEDs on corrugated photoresist 6.5.3. A-priori simulation of optical microcavities 6.5.3.1. Variation of lattice constant and aspect ratio to maximize total radiant intensity 7. Conclusions 8. Outlook Appendices A. Materials – Abbreviations and optoelectronic modeling parameters A.1. Organic semiconductors and ZnO:Al A.1.1. Active emitter materials A.1.2. Dielectric functions A.2. Metals B. Power dissipation spectra and oSPP shifts for top- and bottom-emitting OLEDs incorporating silver and aluminum anode layers C. Further comments on theoretical derivations leading to the simulation of emission from photonic crystal optical microcavities C.1. Numerical approximation of the integration of Maxwell’s equation C.2. Details on the far-field approximation of the periodic plane wave expansion C.3. Derivation of the efficient iterative calculation scheme for the scattering-matrix C.4. On the equality of the two system matrices C.5. Calculation of the complete scattering-matrix for the passive periodically perturbed microcavity Bibliography / Organic light-emitting diodes (OLEDs) are an attractive new light source for display and lighting applications. In general, the light extraction from OLEDs is limited due to the high refractive index of the active emitter material and the thin film geometry. The high refractive index causes the trapping of a significant portion of the emitted light due to total internal reflection (TIR). Due to the thin film layout, the light emission is enhanced for resonant modes of the coherent optical microcavity, in particular for light affected by TIR. In this work two approaches are investigated in detail in order to increase the light extraction efficiency of OLEDs. In a first approach, the implementation of a low refractive index material next to the opaque metallic back-reflector is discussed. This modifies the dispersion relation of the non-radiative surface plasmon polariton (SPP) mode at the metal / dielectric interface, causing a shift of the SPPs dispersion relation. Thereby, the phase space into which power can be efficiently dissipated by the emitter is reduced. For the SPP this power would have been lost to the cavity, such that in total the outcoupling efficiency is increased. In experiment, an increased external quantum efficiency (EQE) is observed for an emitter exhibiting isotropic orientation of the sources (Ir(ppy)3 ,+19 %), as well as for an emitter which shows preferential horizontal orientation (Ir(ppy)2 (acac), +18 %), compared to an optimized device which uses standard material. This corresponds very well to the enhancement of the outcoupling efficiencies of the corresponding microcavities (+23 %, resp. +19 %) reducing the refractive index of the hole transport layer by 15 %. Optical simulations indicate that the approach is generally applicable to a wide range of device architectures. These in particular include OLEDs with emitters showing a perfectly horizontal alignment of their transition dipole moments. Furthermore, the approach is suitable for white OLEDs. Bragg scattering was investigated as second option to increase the light extraction from OLEDs. The method requires a periodically structured surface. For the bottom-emitting OLEDs, this is achieved by a direct laser interference patterning (DLIP) of the transparent electrode. Additionally, top-emitting devices were fabricated onto periodically corrugated photoresist layers. Using a periodic line pattern with a lattice constant of 0.71 μm, the EQE of the bottom-emitting devices was enhanced by 27 % compared to an optimized planar reference. For the bottom-emitting layout, increasing the lattice constant leads to lower EQEs. The increased EQE is attributed to the superposition of the radiative cavity resonances by Bragg scattered intensities of trapped modes. The intensities depend on the lattice constants as well as the height of the periodic surface perturbation. For top-emitting OLEDs comprising a lattice constant of 1.0 μm the EQE was increased by 13 %. Reducing the lattice constant (0.6 μm) decreases the EQE, albeit the luminous efficacy is increased by 13.5 % due to a heavily perturbed emission spectrum. The perturbation is attributed to a coherent interaction of the Bragg scattered modes due to the strong optical microcavity for the top-emitting OLEDs. Thus, for strong perturbation specific emission patterns can be achieved, but an overall enhanced efficiency is difficult to obtain. To investigate the observed results theoretically, a detailed simulation approach is outlined. The simulation method is carefully evaluated using reference data from literature. Using the simulation approach, the emission patterns as well as the efficiencies of the devices can be estimated. The emission spectra reproduced from simulation are in good agreement with the experiment. Furthermore, for the bottom-emitting layout, a strong interaction can be found from simulations for lattice constants below 0.5 μm. For top-emitting OLEDs, the weak interaction regime seems to be more likely to result in an overall enhanced emission. This requires, in contrast to conventional opinion, very shallow perturbations or lattice constants which exceed the peak wavelength of the emission spectrum. However, with the established simulation approach a-priori propositions on the emission spectrum or particular beneficial device layouts become feasible.:1. Introduction 1.1. Motivation 1.2. Scope and outline of this work 2. Organic light emitting diodes - basic concepts 2.1. Amorphous organic semiconductors – electronic properties and transport of charge carriers 2.2. Charge injection into organic semiconductors 2.3. Doping of organic semiconductors and the p-i-n concept for OLEDs 2.4. Charge carrier recombination mechanisms 2.4.1. Displaced harmonic oscillator model for the photoluminescence spectrum of organic emitters 3. OLEDs from thin homogeneous films - theoretical introduction into the optics 3.1. Maxwell’s equations 3.1.1. Boundary conditions 3.1.2. Poynting’s theorem, energy density, and energy flux density 3.2. Optics of thin planar films 3.2.1. Plane waves solution for the homogeneous Maxwell’s equations 3.2.2. Transfer-matrix formalism 3.3. Radiation from electric dipoles embedded into stratified media 3.4. Remarks on the normalized power dissipation 3.5. Description of outcoupled light as resonances 3.6. Basics of optimizing efficiency of OLEDs 3.6.1. Efficiencies for OLED characterization 3.6.2. Optimization of light outcoupling of OLEDs 3.6.2.1. Optimization of the basic cavity layout 3.6.2.2. Optimization of the emitter distribution 3.6.3. Enhancing OLED efficiency beyond the planar limit 4. Experimental fabrication and characterisation methods 4.1. Fabrication methods for organic semiconductors 4.2. Electrical and optical characterisation 4.3. Experimental realization of periodic corrugated surfaces 5. Enhancing the outcoupling efficiency by introducing low-refractive index layers 5.1. Dispersion relations of surface plasmon polaritons in thin film optical microcavities 5.1.1. Bulk surface plasmon polaritons 5.1.2. Coupled surface plasmon polariton states for thin film geometries 5.2. Theoretical potential for outcoupling enhancement due to low refractive index interlayers 5.3. Experimental validation for top-emitting OLEDs with isotropic or anisotropic green phosphorescent emitter 6. Bragg scattering for improved light outcoupling from OLEDs 6.1. Field expansion for periodic photonic crystals 6.2. Bragg scattering in weakly periodically perturbed bottom-emitting monochrome OLEDs 6.2.1. Device details and experimental characterization 6.2.2. Quantitative assignment of Bragg scattering effects within electroluminescence spectrum 6.3. Bragg scattering in top-emitting monochrome OLEDs 6.3.1. Device details and experimental characterization 6.3.2. Analysis of electroluminescence spectrum and description of scattered light from resonance model 6.4. Simulation of the spectral radiant intensity for periodically corrugated OLEDs 6.4.1. Theoretical flowchart 6.4.2. Preliminaries and source representation 6.4.2.1. Plane wave expansion and z-depended field coefficient representation 6.4.2.2. Pseudo-periodic polarization source 6.4.2.3. Solution to the inhomogeneous Maxwell’s equations for a pseudo-periodic source 6.4.3. Field propagation and scattering matrix 6.4.3.1. Reducing the Maxwell’s equation 6.4.3.2. Representation-transformation matrices 6.4.3.3. Formulation of transfer-matrix formalism for periodically perturbed media 6.4.3.4. Iterative calculation of the scattering matrix in plane wave basis 6.4.4. From electromagnetic fields to measurement 6.4.4.1. Far-field solutions in superstrate/substrate media 6.4.4.2. System matrix for pseudo-periodic sources within periodically corrugated cavity 6.4.4.3. Radiant intensity from far-field solutions 6.4.4.4. Treatment of incoherent thick superstrate and substrate 6.4.4.5. Including electroluminescence spectra of organic emitter materials 6.5. Simulation of light emission from emitters embedded into periodically perturbed microcavities 6.5.1. Comparison to experimental data and existing simulation approaches 6.5.2. Simulated light emission for periodically perturbed microcavities 6.5.2.1. Simulation of light emission from corrugated bottom-emitting OLEDs 6.5.2.2. Comparing simulation to experiment for top-emitting OLEDs on corrugated photoresist 6.5.3. A-priori simulation of optical microcavities 6.5.3.1. Variation of lattice constant and aspect ratio to maximize total radiant intensity 7. Conclusions 8. Outlook Appendices A. Materials – Abbreviations and optoelectronic modeling parameters A.1. Organic semiconductors and ZnO:Al A.1.1. Active emitter materials A.1.2. Dielectric functions A.2. Metals B. Power dissipation spectra and oSPP shifts for top- and bottom-emitting OLEDs incorporating silver and aluminum anode layers C. Further comments on theoretical derivations leading to the simulation of emission from photonic crystal optical microcavities C.1. Numerical approximation of the integration of Maxwell’s equation C.2. Details on the far-field approximation of the periodic plane wave expansion C.3. Derivation of the efficient iterative calculation scheme for the scattering-matrix C.4. On the equality of the two system matrices C.5. Calculation of the complete scattering-matrix for the passive periodically perturbed microcavity Bibliography

Die Funktionalisierung von tetra-PEG Makromolekülen mit fotoreaktiven Gruppen und die anschließende Umsetzung zu Hydrogelen durch fotochemische Vernetzung werden beschrieben. Die Funktionalisierung der Makromoleküle wird mittels UV-Vis- und NMR-Spektroskopie nachgewiesen, während der Verlauf der Vernetzung über die dynamische Lichtstreuung und IR-Spektroskopie betrachtet wird. Die hergestellten Hydrogele werden hinsichtlich des Sol-Anteils und der Quelleigenschaften untersucht. Über den Umsatz wird die Konzentration der Netzketten theoretisch berechnet. Einen weiteren Schwerpunkt bildet die Charakterisierung der Hydrogele hinsichtlich der mechanischen Eigenschaften. Über den Speichermodul wird die Konzentration der Netzketten experimentell bestimmt. Mittels dynamischer Lichtstreuung werden die kooperativen Diffusionskoeffizienten und Maschenweiten der Hydrogele bestimmt.