Organic solar cells promise electricity generation at very low cost, and higher installation flexibility as compared to inorganic solar cells. The lower cost is achieved by cheaper semiconductors and easier manufacturing processes. The flexibility is naturally given by these ultra-thin, amorphous layers. Also the power conversion efficiency can be high enough for many applications. The organic molecules have to withstand the constant excitation by photons, transport of energy in form of excitons and charge. A small but significant amount of these photons has energy over the absorption gap, the excess of energy must be released without breaking the molecular bonds. In consequence, the solar cells can also heat up to temperatures at above 80°C. The objective of this work is to answer the question if the small molecules organic solar cells can be stable enough to operate under a very long time. The stability of organic doped layers in an organic solar cell is also addressed. This work starts with a general introduction followed by the description of the experimental procedures. The aging experiments of the solar cell were done with a self developed equipment. The fabrication of this equipment (a set of measurement boxes) was necessary to maintain the conditions, under which a solar cell can be aged, as constant as possible. The measurement boxes were used to control the electrical load of the cell, its temperature, the illumination intensity, and its electric connection to the IxV measurement equipment. A software package was also developed to control the equipment and to facilitate the work and visualization of the high volume of collected data. The model solar cells chosen for the aging experiments were donor-acceptor heterojunctions devices formed with the well-known materials C60 and ZnPc. Two basic different structures were analyzed, because they offered reasonable performance and potentially long lifetime: the flat heterojunction (FHJ) and the mixed heterojunction in a Metal-Insulator-p-Semiconductor (m-i-p) configuration. Variations of the FHJ and of the m-i-p structures are also used to verify the limits of the stability of electrically p- and n- doped organic semiconducting layers. The least stable solar cells are the FHJ devices. These devices show a fast initial decrease of all their characteristic conversion parameters but the Voc. After a few hundred hours, the saturation current (current under a reverse bias of 1 V) was almost stable. The saturation current is related to the number of absorbing centers, the decrease indicates that the degradation of the absorbing centers has stopped. With wavelength resolved external quantum efficiency measurements and chemical analysis, it was found that the degradation is related to the oxidation of C60. It was also shown that the use of organic dopants do not significantly affect the lifetime. The results show that the m-i-p solar cells are more stable than the FHJ devices. They are also stable under high temperatures up to 105°C. Outdoor testing also showed that the solar cells remained chemically, electrically and mechanically stable during a 900 h test.

Organic solar cells promise electricity generation at very low cost, and higher installation flexibility as compared to inorganic solar cells. The lower cost is achieved by cheaper semiconductors and easier manufacturing processes. The flexibility is naturally given by these ultra-thin, amorphous layers. Also the power conversion efficiency can be high enough for many applications. The organic molecules have to withstand the constant excitation by photons, transport of energy in form of excitons and charge. A small but significant amount of these photons has energy over the absorption gap, the excess of energy must be released without breaking the molecular bonds. In consequence, the solar cells can also heat up to temperatures at above 80°C. The objective of this work is to answer the question if the small molecules organic solar cells can be stable enough to operate under a very long time. The stability of organic doped layers in an organic solar cell is also addressed. This work starts with a general introduction followed by the description of the experimental procedures. The aging experiments of the solar cell were done with a self developed equipment. The fabrication of this equipment (a set of measurement boxes) was necessary to maintain the conditions, under which a solar cell can be aged, as constant as possible. The measurement boxes were used to control the electrical load of the cell, its temperature, the illumination intensity, and its electric connection to the IxV measurement equipment. A software package was also developed to control the equipment and to facilitate the work and visualization of the high volume of collected data. The model solar cells chosen for the aging experiments were donor-acceptor heterojunctions devices formed with the well-known materials C60 and ZnPc. Two basic different structures were analyzed, because they offered reasonable performance and potentially long lifetime: the flat heterojunction (FHJ) and the mixed heterojunction in a Metal-Insulator-p-Semiconductor (m-i-p) configuration. Variations of the FHJ and of the m-i-p structures are also used to verify the limits of the stability of electrically p- and n- doped organic semiconducting layers. The least stable solar cells are the FHJ devices. These devices show a fast initial decrease of all their characteristic conversion parameters but the Voc. After a few hundred hours, the saturation current (current under a reverse bias of 1 V) was almost stable. The saturation current is related to the number of absorbing centers, the decrease indicates that the degradation of the absorbing centers has stopped. With wavelength resolved external quantum efficiency measurements and chemical analysis, it was found that the degradation is related to the oxidation of C60. It was also shown that the use of organic dopants do not significantly affect the lifetime. The results show that the m-i-p solar cells are more stable than the FHJ devices. They are also stable under high temperatures up to 105°C. Outdoor testing also showed that the solar cells remained chemically, electrically and mechanically stable during a 900 h test.

In den vergangenen Jahren sind Lipide, Membranen und deren Organisationsformen mehr und mehr in den Fokus der biologischen Forschung gerückt. Es wurde vorgeschlagen, dass in zellulären Membranen selbstassemblierende, submikroskopische Aggregate aus Sphingolipiden, Cholesterol und bestimmten Proteinen existieren und man vermutet, dass insbesondere Viren diese “Lipid Rafts” für ihren Zusammenbau nutzen und auf diese Art ihre Proliferationseffizienz erhöhen. Gleichwohl sind die genaue biologische Funktion und auch die molekulare Basis der Assoziation bestimmter Protein mit Lipid Rafts auch weiterhin unbekannt. In der vorliegenden Arbeit wurde Fluoreszenz-Lebenszeit-Mikroskopie genutzt, um die Lipid-Raft-Anreicherung des HIV-1 Glycoproteins gp41 zu untersuchen. Förster-Resonanz-Energietransfer zwischen fluoreszenzmarkierten viralen und Raft-Marker-Proteinen wurde gemessen, um deren gemeinsame, lokale Aufkonzentrierung in Lipid Rafts nachzuweisen. Durch Verwendung verschiedener Deletions- und Mutationsvarianten des Proteins konnte nicht nur seine Lipid-Raft-Präferenz demonstriert, sondern auch das Cholesterol-Bindemotiv (CRAC) als entscheidender Faktor der lateralen Sortierung identifiziert werden. Wir haben in diesem Kontext auch eine systematische Zell-zu-Zell-Variabilität in unseren Daten bemerkt, die einen zugrundeliegenden zellbiologischen Mechanismus der Membranorganisation nahelegt. Mithilfe von Fluoreszenz-Polarisations-Mikroskopie konnte zudem eine klare CRAC-Abhängigkeit der gp41-Oligomerisierung aufgezeigt werden. Die von uns gewonnenen Daten erlauben einen tieferen Einblick in die molekulare Basis und die biologischen Folgen der cholesterol-abhängigen lateralen Proteinorganisation für Virusassemblierungsprozesse an biologischen Membranen. / In recent years, there has been a considerable interest in the molecular organization of biological membranes. It has been hypothesized that self-assembling, freely diffusing, submicroscopic domains consisting of sphingolipids, cholesterol and certain proteins exist and the prevailing view is that those lipid rafts serve as platforms for specific molecular interactions by the preferential exclusion and inclusion of proteins. It was presumed, that in particular viruses make use of plasma membrane lipid rafts to augment the infection process and spread efficiently. However, the exact biological function and physical basis of protein partitioning into microdomains remains an outstanding question in virus biology. In the present study, fluorescence lifetime imaging microscopy was used to study lipid raft partitioning of the HIV-1 glycoprotein gp41 by detecting Foerster Resonance Energy Transfer between fluorescently labeled viral and raft marker proteins in living cells. Plasma membrane microdomain association of gp41 was demonstrated and by introducing systematic mutations and truncations in different gp41 motifs, the cholesterol recognition amino acid consensus (CRAC) was identified as the crucial determinant of the lateral sorting. Interestingly, we observed a systematic cell-to-cell variability in our raft related data that suggests underlying cell-biological mechanisms of membrane organization. Moreover, fluorescence polarization microscopy revealed a distinct CRAC requirement for gp41 oligomerization whereas other properties, such as intracellular distribution and expression efficiency were clearly demonstrated to be CRAC independent. Our data provide further insight into the molecular basis and biological implications of the cholesterol dependent lateral protein sorting for virus assembly processes at cellular plasma membranes.

Nowadays, polymer-metal hybrids are covering a broad range of advanced applications, especially in the automotive or aerospace industries where high performance and lightweight components are highly demanded. Hybrid parts may offer additional functionality regarding strength, durability, impact and wear resistance without sacrificing size or weight of the full component. However, there are still challenges regarding improving the adhesion between dissimilar materials such as metals to polymers and its composites. There is a lack of research about the influence of a post heat treatment on adhesion and durability in polymer-metal hybrids manufactured through an overmolding processing chain. There is also a need for using adhesive promoters that may offer simultaneous corrosion protection to metallic substrates in order to extend the lifecycle of the part when subjected to diverse harsh environments. In this work, two organic coatings used as adhesive promoters on steel substrates were investigated: the first one is a polyester-based powder-coat adhesive developed in the Leibniz-Institute in Dresden. The second one is a high performance anti-corrosive electrophoretic paint that has never been reported in the literature as an intermediate adhesive layer in a thermoplastic-polyurethane (TPU) overmolding processing chain. A TPU was overmolded on both pre-coated steel substrates, and the adhesion of the polymer to the metal substrate was investigated after a heat treatment (annealing), and a subsequent hygrothermal aging at different temperature-humidity conditions. The influence of the annealing process on the adhesion and durability of the multilayered specimen was investigated in depth; similarly, failure modes and lifetimes were evaluated after the hygrothermal aging. Lifetime predictions calculated from kinetic parameters for solid decomposition -obtained from thermogravimetric analysis- were validated experimentally with polyurethane-steel hybrids commonly used as district heat pipes. Adhesion of TPU on the steel substrate using both organic coatings as adhesive promoters was successful due to the contribution of new physical-chemical and mechanical interactions at the polymer-coating interface, especially after annealing at 100 °C for 20 h. Additionally, heat treated hybrids exhibited a much better performance because of the apparent increased in the anchoring density at the polymer-metal interfaces. It is conclusive that progressive failure of the multilayered specimen is strongly dependent on water diffusion rather than thermolysis of any of the components, as it was detected by FTIR, and observed in the micrographs on the artificially-aged hybrid surfaces. Finally, accelerated aging was used to correlate lifetime predictions throughout the analysis of the kinetics of degradation using TGA experiments and mechanical tests. The calculated values of the activation energy evidence that durability of the polyurethane-based polymers is affected by temperature and humidity at the conditions described in this work. Lifecycle is directly related to kinetic parameters, and especially to the activation energy, EA. This kinetic parameter for pre-aged specimens, and particularly for those subjected to higher temperature conditions, were lower when compared to the fresh polymer; as it was demonstrated that TGA analysis is a primary tool to predict lifetime for thermoplastic and thermosetting polyurethanes.

Nanophotonische Systeme sind eine leistungsfähige Plattform für die Untersuchung von Licht-Materie-Wechselwirkungen. In solchen Systemen bricht die übliche Beschreibung einer elektromagnetischen Welle als eine Welle, die in Bezug auf ihre Ausbreitungsrichtung transversal polarisiert ist, zusammen. Dies ist auf die Einengung der geführten Lichtfelder zurückzuführen, welche zu einer longitudinalen Komponente der elektromagnetischen Felder führt. In dieser Arbeit nutzen wir dies in Verbindung mit unterschiedlichen Kopplungsstärken von Cäsiumatomen an \sigma^- und \sigma^+ polarisiertes Licht, um das Prinzip neuartiger nicht-reziproker optischer Bauelemente zu demonstrieren. Im ersten Teil dieser Arbeit demonstrieren wir die nicht-reziproke Verstärkung von fasergeführtem Licht mit Hilfe von Raman-Verstärkung durch spinpolarisierte Cäsiumatome, die an die Nanofasertaille eines verjüngten Faserabschnitts gekoppelt sind. Wir zeigen, dass unser neuartiger Mechanismus kein externes Magnetfeld benötigt und dass wir die Richtung der Verstärkung vollständig über den atomaren Spinzustand kontrollieren können. Darüber hinaus nutzen wir die chirale Licht-Materie-Wechselwirkung in unserem System, um einen nicht-reziproken antisymmetrischen optischen Phasenschieber zu realisieren. Diese Ergebnisse tragen zur Etablierung einer neuen Klasse von spin-gesteuerten, nicht-reziproken integrierten optischen Bauelementen bei und können den Aufbau komplexer optischer Netzwerke vereinfachen. In einem weiteren Forschungsprojekt tragen wir zum grundlegenden Verständnis von Atomen bei, indem wir die Lebensdauer eines angeregten Cäsiumzustands präzise messen. Wir messen die Lebensdauer des Cäsium 5D_{5/2} Zustands im freien Raum. Wir finden eine Lebensdauer von 1353(5) ns, die mit einer aktuellen theoretischen Vorhersage übereinstimmt. Unsere Messung trägt dazu bei, eine seit langem bestehende Unstimmigkeit zwischen verschiedenen experimentellen und theoretischen Ergebnissen zu beseitigen. / Nanophotonic systems are a powerful platform for the study of light-matter interactions. In such systems, the common description of an electromagnetic wave as a wave that is transversely polarized with respect to its propagation direction breaks down. This is due to the tight confinement of the guided light fields, which leads to a longitudinal component of the electromagnetic fields. In this thesis, we use this in conjunction with different coupling strengths of cesium atoms to \sigma^- and \sigma^+ polarized light to provide proof-of-principle demonstrations of novel non-reciprocal optical devices. In the first part of this thesis, we demonstrate non-reciprocal amplification of fiber-guided light using Raman gain provided by spin-polarized cesium atoms that are coupled to the nanofiber waist of a tapered fiber section. We show that our novel mechanism does not require an external magnetic field and that it allows us to fully control the direction of amplification via the atomic spin state. Moreover, we use the chiral light-matter interaction in our system to implement a non-reciprocal antisymmetric optical phase shifter. These results contribute to establishing a new class of spin-controlled, non-reciprocal integrated optical devices and may simplify the construction of complex optical networks. In an additional research project, we also contribute to the fundamental understanding of atoms by precisely measuring the lifetime of an excited cesium state. We measure the lifetime of the cesium 5D_{5/2} state in free space. We find a lifetime of 1353(5) ns, in agreement with a recent theoretical prediction. Our measurement contributes to resolving a long-standing disagreement between several experimental and theoretical results.