Les cellules solaires organiques ont longtemps été qualifiées de cellules solaires« polymères ». Cette appellation découle du fait que la couche active de telles cellules solaires a majoritairement été réalisée avec un polymère donneur d’électrons. L’utilisation d’un polymère au sein de la couche active a permis d’envisager la production de cellules solaires organiques par voie liquide avec des procédés d’impression à grande vitesse. Il existe cependant un autre type de matériau donneur d’électrons : les petites molécules. Ces dernières déposées par évaporation thermique permettent d’obtenir des cellules à haut rendement. A cause de leur faible propriété filmogène, les petites molécules n’ont cependant pas été envisagées pour un procédé d’impression industrielle. Or, en 2012 plusieurs petites molécules déposables par voie liquide font leur apparition et permettent d’obtenir des rendements suffisamment élevés à l’échelle laboratoire, pour envisager leur à l’échelle industrielle. Ces travaux de thèse ont été conduits en collaboration avec ARMOR, une entreprise visant à commercialiser les cellules solaires organiques, dans le but d’évaluer le potentiel d’industrialisation des petites molécules donneuses d’électrons. Le p-DTS(FBTTh2)2 a été choisi pour cette étude. Il a été montré qu’il était possible d’atteindre des rendements de 2% avec ce matériau à l’air, avec des solvants non toxiques en utilisant un procédé d’enduction à racle. L’industrialisation du p-DTS(FBTTh2)2 n’a cependant pas été poursuivie car ce dernier est très instable à l’air. Ces travaux présentent une méthodologie pouvant être utilisée pour évaluer l’industrialisation d’autres matériaux de ce type. / Organic solar cells are often called “polymer” solar cells. This term comes from the fact that the active layer of such solar cells have been widely made with a donor polymer. The use of polymer inthe active layer gives interesting filming properties that can be used to produce these solar cells industrially with a high speed printing process. Yet, another type of donor materials exists: the small molecules. Deposited by thermal evaporation, this type of materials can allow to reach high efficiency solar cells. Because of their poor filming properties, small molecules were not a good candidate for an industrialization using high speed printing. However, in 2012 several solution processable small molecules were proven particularly promising by demonstrating high efficiency at a laboratory scale.These encouraging results let imagine that it could be possible to produce organic solar cells with such materials. This PhD work has been done in collaboration with ARMOR, a company highly implied in the commercialization of organic solar cells, in order to evaluate if small molecules materials could be use dindustrially with a high speed printing process. The p-DTS(FBTTh2)2 has been chosen for this study. It has been shown that it is possible to reach efficiencies as high as 2 % with such a material, using non toxicsolvents and by making the solar cell in the air with a Doctor Blade. Nevertheless, the industrialization ofthe p-DTS(FBTTh2)2 has not been pursued due to the rapid degradation of this molecule in the air. This work presents a method that can be used to evaluate the industrialization of other efficient small molecules.

The thesis entitled “New DNA-Targeting Small Molecules as Potential Anticancer Agents and for in vivo Specificity toward Enhanced Silk Production” encompasses design, computational calculations, and syntheses of diverse small molecular scaffolds to explicitly target duplex and higher order DNA morphologies (G-quadruplex DNA). Some of these molecules have a potential as anticancer agents. Besides, an attempt has been made elucidate the importance of novel oligopyrrole carboxamides in the enhancement of silk yield, hence proving to a boon in the field of sericulture. The work has been divided into six chapters. Chapter 1. DNA Binding Small Molecules as Anticancer Agents Figure 1. DNA targeting by small molecules. Cancer has always been a dreadful disease and continues to attract extensive research investigations. Various targets have been identified to restrain cancer. Among these DNA happens to be the most explored one. A wide variety of small molecules, often referred to as “ligands”, has been synthesized to target numerous structural features of DNA (Figure 1). The sole purpose of such molecular design has been to interfere with the transcriptional machinery in order to drive the cancer cell toward apoptosis. The mode of action of the DNA targeting ligands focuses either on the sequence-specificity by groove binding and strand cleavage, or by identifying the morphologically distinct higher order structures like that of the G-quadruplex DNA. Chapter 2. Ligand 5, 10, 15, 20-tetra(N-methyl-4-pyridyl)porphine (TMPyP4) Prefers the Parallel Propeller-type Human G-Quadruplex DNA over its other Polymorphs The binding of ligand 5, 10, 15, 20-tetra(N-methyl-4-pyridyl)porphine (TMPyP4) with telomeric and genomic G-quadruplex DNA has been extensively studied. However, a comparative study of interactions of TMPyP4 with different conformations of human telomeric G-quadruplex DNA, namely parallel propeller-type (PP), antiparallel basket-type (AB), and mixed hybrid-type (MH) G-quadruplex DNA has not been done. We considered all the possible binding sites in each of the G-quadruplex DNA structures and docked TMPyP4 to each one of them. The resultant most potent sites for binding were analyzed from the mean binding free energy of the complexes. Molecular dynamics simulations were then carried out and analysis of the binding free energy of the TMPyP4-G-quadruplex complex showed that the binding of TMPyP4 with parallel propeller-type G-quadruplex DNA is preferred over the other two G-quadruplex DNA conformations. The results obtained from the change in solvent excluded surface area (SESA) and solvent accessible surface area (SASA) also support the more pronounced binding of the ligand with the parallel propeller-type G-quadruplex DNA (Figure 2). Figure 2. Ligand TMPyP4 prefers parallel propeller-type G-quadruplex DNA morphology. Chapter 3. A Theoretical Analysis on the Selective Stabilization of Intermolecular G-quadruplex RNA with a bis-Benzimidazole Ligand EtBzEt over TMPyP4 in K+ Environment Ever since the discovery of G-quadruplex RNA, a constant urge exists to target these higher order RNA conformations. These structures play a significant role in the transcriptional and translational mechanism. Herein we have determined the mode and extent of association of certain G-quadruplex DNA binding bisbenzimidazole ligand (EtBzEt) in comparison to a known porphyrin ligand (TMPyP4). We have performed docking studies of the known G-quadruplex DNA binding ligands with the parallel propeller G-quadruplex RNA (PPR) to determine the most potent binding conformation which showed EtBzEt to be a better RNA binder than others. Furthermore, a molecular dynamics (MD) simulation (6 ns) was performed for the most stable docked complex in explicit solvent environment. The role of K+ ions, Hoogsteen hydrogen bond formation and backbone dihedral angle between the tetrads were carefully analyzed during the entire simulation run to determine the stability of each ligand associated PPR complex. All the analyses conclusively showed that while TMPyP4 merely stabilized the PPR, the ligand EtBzEt stabilized PPR very efficiently (Figure 3). Figure 3. Stabilzation and destabilization by EtBzEt and TMPyP4, repectively. Red and green ovals represent EtBzEt and TMPyP4, repectively. Chapter 4A. Design and Synthesis of New DNA Binding Fe(III) and Co(II) Salen Complexes with Pendant Oligopyrrole Carboxamides Extensive research on these oligopyrrole carboxamides has shown their specificity toward AT-rich sequences with high binding affinity. Here we have designed and synthesized Fe (III)-and Co (II)-based salen complexes attached with minor groove targeting oligopyrrole carboxamide side-chains (Figure 4). While the ligands showed excellent activity toward DNA damage, they also exhibited high affinity toward the minor grooves of the ds-DNA. This was also reflected in the high efficiency of the ligands toward cancer cell cytotoxicity. Further studies revealed that the ligands resulted in prominent nuclear condensation and fragmentation thereby driving the cells toward apoptosis. The presence of metal coordinated salen moiety conjugated with positively charged pendants ending with minor groove binding oligopyrrole carboxamides might have resulted in the increased activity of the ligands toward DNA targeting and cancer cell death. Figure 4. Chemical structures of the ligands used in this study. Chapter 4B. Design and synthesis of novel oligopyrrole based salen metal complexes and their efficiency toward stabilization of G-quadruplex DNA DNA targeting has been the key strategy toward the restriction of cancer cell proliferation. In a similar effort, we have designed and synthesized novel salen based Ni(II) and Pd(II) metal complexes with positively charged flanking side-chains comprising attached N-methylpyrrole carboxamides of varying lengths (Figure 5). The ligands showed efficient stabilization of the G-quadruplex DNA morphologies, with specificity over the duplex DNA. Sufficient inhibition of the telomerase activity was observed by the TRAP-LIG assay which was ascertained by the prominent restriction of cancer cell proliferation in the long-term cell viability assay. The ligands exhibited condensation and fragmentation of the nucleus when observed under confocal microscopy which is indicative of the cells undergoing apoptosis. Further annexin V-FITC and PI dual staining showed apoptosis to be the mechanistic pathway underlying the cancer cell cytotoxicity by the ligands. Modeling studies clearly showed the stacking of the salen moiety over the G-tetrads with the association of the pendant oligopyrrole carboxamide units to the grooves. Figure 5. Chemical structures of the ligands used in this study. Chapter 5A. Role of Metal Ions in Novel Fluorescein based Salen and Salphen Complexes toward Efficient DNA Damage and their Effect on Cancer Cells Metal ions play an important role toward DNA damage and numerous ligands have been synthesized for their use in anticancer therapy. Herein, we have designed and synthesized Fe(III) and Co(II) based salen/salphens by bridging two fluorescein moieties with varying spacers (Figure 6). Although the ligands exhibit dual binding mode, the more flexible salen ligands prefer to associate to the minor groove of the DNA while the relatively rigid salphen ligands show greater intercalation. The biophysical experiments reveal better binding affinity of the salphens toward duplex DNA as compared to the salen ligands. The metal coordination resulted in efficient DNA cleavage of plasmid at low ligand concentrations. The ligands also showed cancer cell cytotoxicity, cellular internalization with apoptosis as the proposed mechanism for cell death. Figure 6. Chemical structures of the salen and salphen ligands used in this study. Chapter 5B. Fluorescein based Salen and salphen Complexes as stabilizers of the Human G-quadruplex DNA and Promising Telomerase Inhibitors Metal based salen complexes have been considered as an important scaffold toward targeting of DNA structures. In the present work we have designed and synthesized nickel(II)-and palladium(II)-salen and salphen ligands by using fluorescein as the backbone to provide an extended aromatic surface (Figure 7). The ligands exhibit sufficient affinity toward the human telomeric G-quadruplex (G4) DNA in preference to the duplex DNA and also exhibit promising inhibition of telomerase activity. This is ascertained by their potency in the long-term cell viability assay which shows significant cancer cell cytotoxicity in presence of the ligands. Confocal microscopy showed cellular internalization followed by nuclear localization. Considerable population at the sub-G1 phase of the cell cycle showed cell death via apoptotic pathway. Figure 7. Chemical structures of the ligands used in this study. Chapter 6. Knockdown of Broad-Complex Gene Expression of Bombyx mori by Oligopyrrole carboxamides Enhances Silk Production Bombyx mori (B. mori) is important due to its major role in the silk production. Though DNA binding ligands often influence gene expression, no attempt has been made to exploit their use in sericulture. The telomeric heterochromatin of B. mori is enriched with 5′-TTAGG-3′ sequences. These sequences were also found to be present in several genes in the euchromatic regions. We examined three synthetic oligopyrrole carboxamides that target 5′-TTAGG-3′ sequences in controlling the gene expression in B. mori (Figure 8). The ligands did not show any defect or feeding difference in the larval stage, crucial for silk production. The compounds caused silencing of various isoforms of the broad-complex transcription factor and cuticle proteins which resulted in late pupal developmental defects. This study shows for the first time use of oligopyrrole carboxamide drugs in controlling gene expression in B. mori and their long term use in enhancing silk production. Figure 8. Chemical structures of the ligands used in this study (top) and increased cocoon size on ligand treatment.

Du fait de leur faible coût de production et de leur intégration possible sur substrat flexible, les cellules photovoltaïques organiques sont prometteuses pour répondre aux besoins futurs en énergie. Leurs performances reposent sur l'architecture de la cellule et sur la nature des matériaux choisis. Par conséquent, le contrôle à l'échelle nanométrique de la couche active (formation de nanodomaines purs, organisation moléculaire...), ainsi que le développement de nouvelles molécules aux propriétés électroniques et structurales optimisées apparaissent comme des paramètres clés. Dans ce contexte, les travaux présentés dans cette thèse visent à étudier le lien entre la morphologie des films minces et les propriétés de transport à l'échelle nanométrique en fonction des matériaux actifs utilisés. Pour cela deux voies ont été explorées. La première voie repose sur l'utilisation des propriétés d'auto-organisation des cristaux liquides pour améliorer la formation et l'organisation de nanodomaines. Pour cette étude, nous avons choisi d'associer un donneur d'électron classique, le poly-3-hexylthiophène (P3HT), et de le mélanger avec un complexe de nickel [Ni(4dopedt)2] possédant des propriétés cristallines liquides colonnaires. L'étude par Microscopie à Force Atomique (AFM), Conductive-AFM (C-AFM), absorption UV-visible et spectrométrie Raman des films de mélanges démontre l'effet structurant du cristal liquide sur les chaînes de P3HT, en fonction de l'épaisseur de la couche et des traitements thermiques effectués. La deuxième voie explorée repose sur l'ingénierie moléculaire. Suite à une étude bibliographique, nous avons conçu puis synthétisé différentes petites molécules fluorées capables d'agir comme accepteurs d'électrons. Leur synthèse est réalisée en plusieurs étapes, privilégiant une méthode de couplage innovante, l'hétéroarylation directe. Les molécules obtenues ont été caractérisées par les techniques analytiques classiques, puis soumises à une étude de relation structures/propriétés. D'une part, les analyses optiques, électrochimique et thermique ont révélé leur grande stabilité et leur intérêt potentiel pour l'application visée. D'autre part, leur étude en film mince, par spectroscopie d'absorption UV-visible, de fluorescence et par AFM, révèle l'influence de la substitution du squelette conjugué par des atomes de fluor ainsi que de la modification des chaînes alkyles des groupements terminaux sur les propriétés optoélectroniques et structurelles des molécules. / Organic solar cells appear as a promising technology to meet future energy requirements, owing to their low production costs, their great flexibility and their ability to be integrated into light devices. Their performances rely on their architecture and the nature of the chosen materials. As a consequence, two of the key parameters for their development are the control the active layer at a nanometric scale (molecular organisation and the formation of pure compound nanodomains) and the development of new small molecules with optimized electronic and structural properties. This work comes in that aim : the study of the relation between thin film morphology and transport properties at the nanometric scale as function of the chosen materials. Two ways have been explored. The first way relied on self-organisation properties of a liquid crystal for improving the formation and organisation of nanodomains. In this purpose, we have associated a well-known electron donor, the poly-3-hexylthiophene (P3HT), with a complex of nickel, named as [Ni(4dopedt)2], exhibiting columnar liquid crystal properties. Atomic Force Microscopy (AFM), Conductive-AFM (C-AFM), UV-visible absorption and Raman spectroscopy on bulk films have shown the structuring effect of the liquid crystal on the P3HT chains as a function of the films thicknesses and thermal annealing. The second way was based on molecular engineering. Following a bibliographic study, we have designed and synthetized different fluorinated small molecules with electron acceptor capability. For this, a more economical and cleaner synthesis technique has been employed: the direct arylation. These molecules have been characterized by classical analytic technics, and a study of the relation between structure and properties has been carried out. On the one hand, optical, electrochemical and thermal analyses have shown their good stability and their potential for the aimed application. On the other hand, their study in thin film by UV-visible absorption, fluorescence and AFM have shown the influence of backbone substitution by fluorine atoms as well as the impact of the nature of alkyl end chains on the optoelectronic and structural properties of these molecules.

Current fossil fuels (Coal and Petroleum) based economy is not sustainable in the long run because of its dwindling resources, and increasing concerns of climate change due to excessive carbon dioxide (CO2) emission. To mitigate CO2 emission and climate change, scientists across the world have been looking for clean and sustainable energy sources. Among them hydrogen gas (H2) could be more promising because it is the most clean fuel and can be produced from cheap source (water) which is renewable and abundant. Nevertheless, the bottleneck for hydrogen economy is lying in the cost of hydrogen production from water. Still there are no any efficient systems developed which can deliver hydrogen from water in economically viable way. Meanwhile, recent research on old molecule ammonia-borane (H3N•BH3, AB) as hydrogen source has increased the hope towards the hydrogen economy, however, catalytic recycling (or efficient regeneration) of AB from the dehydrogenated product polyborazylene (PB or BNHx) is the biggest hurdle which prevents use of AB as practical hydrogen storage material. Therefore, it is imperative to understand the dehydrogenation pathways of ammonia-borane (or related amine-boranes) which lead to polymeric or oligomeric product(s). On the other hand, methane (CH4) is abundant (mostly untamed) but cleaner fuel than its higher hydrocarbon analogs. To develop highly efficient catalytic systems to transform CH4 into methanol (gas to liquid) is of paramount importance in the field of catalysis and it could revolutionize the petrochemical industry. Therefore, to activate CH4, it is crucial to understand its binding interaction with metal center of a molecular catalyst under homogenous condition. However, these interactions are too weak and hence σ–methane complexes are very elusive. In this context, σ-H2 and σ-borane complexes bear some similarities in σ-bond coordination (and four coordinated boranes are isoelectronic with methane) could be considered as good models to study σ-methane complexes. Studying the H−H and B−H bond activation in H2 and amine-boranes, respectively, would provide fundamental insights into methane activation and its subsequent functionalization. Moreover, the proposed methanol economy by Nobel laureate George Olah seems more promising because methanol can be produced from CH4 (CO2 as well). This in turn will gradually reduce the amount of two powerful greenhouse gases from the earth’s atmosphere. Thus, efficient and economic production of methanol from CH4 and CO2 is one of most challenging problems of today in the field of catalysis and regarded as the holy grails. Furthermore, very recently formic acid (HCOOH) is envisaged as a promising reversible hydrogen storage material because it releases H2 and CO2 in the presence of a suitable and efficient catalyst or vice versa under ambient conditions. Objective of the research work: Taking the account of the above facts, the research work in this thesis is mostly confined to utilize electrophilic Ru(II)-complexes for activation of small molecules such as ammonia-borane (H3N•BH3) [and related amine-borane (Me2HN•BH3)], hydrogen (H2), methane (CH4), formic acid (HCOOH) and carbon dioxide (CO2) and investigation of their mechanistic pathways using NMR spectroscopy under homogeneous conditions. Though these molecules are small, they have huge impacts on chemical industries (energy sector and chemical synthesis: drugs/natural products) and environment [CO2 and CH4 are potent green house gases] as well. However, they are relatively inert molecules, especially CH4 and CO2, and impose very tough challenges to activate and functionalize them into useful products under ambient conditions. The partial oxidation of the strong C−H bond in CH4 for its transformation into methanol under relatively mild condition using an organometallic catalyst is considered as a holy grail in the field of catalysis which is mentioned earlier. More importantly, to develop better and highly efficient homogeneous catalytic systems for the activation of these molecules, it is imperative to understand the mechanistic pathways using well defined homogeneous metal complexes. Thus, an understanding of the interaction of these inert molecules with metal center is obligatory. In this context, discovery of a σ-complex of H2 gave remarkable insights into H−H bond activation pathways and its implications in catalytic hydrogenation reactions. Subsequently, σ-borane complexes of amine-boranes were discovered and found to be relatively more stable because of stronger M−H−B interaction and hence act as good models to study the M−H−C interaction of elusive σ-methane complex. On the other hand, HCOOH, a promising hydrogen storage material and its efficient catalytic dehydrogenation/decarboxylation and CO2 hydrogenation back to HCOOH using well defined homogeneous catalysts could lead to a sustainable energy cycle. Therefore, it is quite significant to understand the mechanistic pathways of formic acid dehydrogenation/decarboxylation and carbon dioxide reduction to formic acid for the development of next generation efficient catalysts. Chapter highlights: Keeping all these in view, we carried out thorough studies on the activation of these small molecules by electrophilic Ru(II)-complexes. This thesis provides useful insights and perspective on the detailed investigation of mechanistic pathways for the activation of small molecules such as H3N•BH3 [and Me2HN•BH3], H2, CH4, HCOOH and CO2 using electrophilic Ru(II)-complexes under homogeneous conditions using NMR spectroscopy. In Chapter 1 we provide brief overview of small molecule activation using organometallic complexes. This chapter presents pertinent and latest results from literature on the significance of small molecule activation. Although there are several small molecules which need our attention, however, we have focused mainly on H3N•BH3 [and Me2HN•BH3], H2, CH4, HCOOH and CO2. In Chapter 2, we present detailed investigation of mechanistic pathways of B−H bond activation of H3N•BH3 and Me2HN•BH3 using electrophilic [RuCl(dppe)2][OTf] complex using NMR spectroscopy as a model for methane activation. In these reactions, using variable temperature (VT) 1H, 31P{1H} and 11B NMR spectroscopy we detected several intermediates en route to the final products at room temperature including a σ-borane complex. On the basis of elaborative studies using NMR spectroscopy, we have established the complete mechanistic pathways for dehydrogenation of H3N•BH3/Me2HN•BH3 and formation of B−H bond activated/cleaved products along with several Ru-hydride and Ru-(dihydrogen) complexes. Keeping the B−H bond activation of amine-boranes in view as a model for methane activation, we attempted to activate methane using [RuCl(dppe)2][OTf] complex. In addition, [Ru(OTf)(dppe)2][OTf] complex having better electrophilicity than [RuCl(dppe)2][OTf], was synthesized and characterized. The [Ru(OTf)(dppe)2][OTf] complex has highly labile triflate bound to Ru-metal and therefore its reactivity studies toward H2 and CH4 were carried out where H2 activation was successfully achieved, however, no any spectroscopic evidence was found for C−H bond activation of CH4. The Chapter 3 describes the synthesis and characterization of several Ru-Me complexes such as trans-[Ru(Me)Cl(dppe)2], [Ru(Me)(dppe)2][OTf], trans-[Ru(Me)(L)(dppe)2][OTf] (L = CH3CN, tBuNC, tBuCN, H2) with an aim to trap corresponding σ-methane intermediate at low temperature. However, interestingly, we observed spontaneous but gradual methane elimination and orthometalation of [Ru(Me)(dppe)2][OTf] complex at room temperature. We thoroughly investigated mechanistic details of methane elimination and orthometalation of [Ru(Me)(dppe)2][OTf] using VT NMR spectroscopy, NOESY and DFT calculations. Furthermore, H2 activation was confirmed unambiguously by [Ru(Me)(dppe)2][OTf] and Ru-orthometalated complexes using NMR spectroscopy under ambient conditions. An effort was also made to activate methane using Ruorthometalated complex in pressurized condition of methane in a pressure stable NMR tube. Moreover, preliminary studies on protonation reaction of [Ru(Me)(dppe)2][OTf] using VT NMR spectroscopy to trap σ-methane at low temperature was carried out which provided us some useful information on dynamics between proton and Ru-Me species. The Chapter 4 provides useful insights into the mechanistic pathways of dehydrogenation/decarboxylation of formic acid using [RuCl(dppe)2][OTf]. Catalytic dehydrogenation of HCOOH using [RuCl(dppe)2][OTf] was observed in presence of Hunig base (proton sponge). In addition, a complex [Ru(CF3COO)(dppe)2][OTf] was synthesized and characterized using NMR spectroscopy, and found to readily dehydrogenate HCOOH. Moreover, preliminary results on transfer hydrogenation of CO2 into formamide using [RuCl(dppe)2][OTf] as a precatalyst and tert-butyl amine-borane (tBuH2N•BH3) as secondary hydrogen source was confirmed using 13C NMR spectroscopy. The mechanisms were proposed for HCOOH dehydrogenation and transfer hydrogenation of CO2 based on our NMR spectroscopic studies. Furthermore, a few test reactions of transfer hydrogenation of selected alkenes such as cyclooctene, acrylonitrile, 1-hexene using [RuCl(dppe)2][OTf] as pre-catalyst and tert-butyl amine-borane (tBuH2N•BH3) as secondary hydrogen source showed quantitative conversion to hydrogenated products.

Recently, non-cellular viral agents became the focus of a large number of scientific groups. A prominent and widespread group of these viruses are flaviviruses, which include, for example, Zika virus, Dengue fever virus, tick-borne encephalitis virus and West Nile virus. There is a considerable diversity among these viruses, however, highly conserved proteins can be found throughout this viral genus. The largest and most conserved protein encoded by flaviviruses is the nonstructural NS5 protein. Its N-terminal domain bears the methyltransferase (MTase) activity. Thanks to the methylation of its genome, it allows the virus to initiate translation and at the same time mask it from the host's immune system. By blocking the active site of this enzyme with a small molecule, viral infection could be stopped not only in one flavivirus, but, due to the high conservation of MTases, in all other flaviviruses. This diploma thesis deals with the aforementioned MTase domain of the NS5 protein, specifically of the West Nile virus (WNV). After designing an insert encoding the WNV MTase domain, amplifying it and ligating it into the vector, the MTase domain was prepared by a recombinant expression, followed by purification. Subsequently, complexes of the protein with small molecules (MTase ligands) were formed, in...

Organic solar cells (OSCs) is an emerging photovoltaic technology that opens up new application areas where common inorganic techniques are not able to score. Some of those key features are flexibility, light weight, semitransparency, and low cost processing. The current industry-standard for the transparent electrode, indium tin oxide (ITO), cannot provide these properties because it is brittle and expensive. This thesis aims to investigate an alternative type of promising transparent electrode: silver nanowire (AgNW) networks. They exhibit similar or even better optical and electrical performance than ITO down to a sheet resistance of 12 Ohm/sq at 84% transmission (including the glass substrate). Furthermore, AgNWs are more flexible, solution-processable, and more cost-effective than ITO. However, two challenges occur during implementation as bottom electrode in OSCs. First, their inherently high roughness causes devices to shunt. Second, the AgNW network structure exhibits – in contrast to the continuous ITO – µm²-sized voids that have to be bridged electrically by the organic layers. In the first part of this thesis, solution-processed small molecule charge transport layers are investigated. In the case of hole transport layers (HTL), the host BF-DPB and the dopant NDP9 are investigated using tetrahydrofuran as a solvent. It is shown that BF-DPB is already doped by NDP9 in solution via the formation of a hybrid molecule complex. Solution-processed layers exhibit similar conductivities as compared to the reference deposition, which is thermal evaporation in high vacuum. The layers sufficiently smoothen the AgNW electrode such that DCV5T-Me:C60 organic solar cells with an efficiency up to 4.4% are obtained. Moreover, the influence of the square micrometer large network voids is investigated using HTLs of varying conductivity. As a result, a minimum conductivity of 1e−4 S/cm is needed to avoid macroscopic performance losses. Equivalent circuit simulations are performed to confirm these results. As a second planarization method, the AgNWs are buried in an insulating polymer that serves concurrently as flexible and ultrathin substrate. Out of three different polymers tested, the optical adhesive ’NOA63’ gives the best results. The roughness is strongly reduced from 30 nm down to (2 ± 1) nm. Two different OSC types are employed as testing devices with fully-flexible alumina encapsulation against moisture ingress. Maximum power conversion efficiencies of 5.0% and 5.6% are achieved with a fullerene-free cascade layer architecture and a DCV5T-Me:C60 OSC, respectively. To evaluate the applicability of these fully-flexible and encapsulated devices, degradation studies are performed under continuous illumination and a humid climate. Although employing the intrinsically stable DCV5T-Me:C60 stack design, within one day a fast degradation of the fully-flexible solar cells is observed. The degradation is attributed to AgNW electrode failure that results from photo-oxidation and -sulfurization, photo-migration, and electromigration. It is further shown that the cascade organic solar cell lacks intrinsic stability. In summary, efficient, fully-flexible, and encapsulated devices are shown. However, in terms of competitive OSCs, the low stability of AgNW electrodes is a challenge to be taken care of. In current research, this issue needs to be addressed more frequently. / Organische Solarzellen (OSZ) sind ein junges Forschungsgebiet der Photovoltaik, welches neue Anwendungsgebiete erschließt, für die herkömmliche anorganische Solarzellen nicht einsetzbar sind. Einige der Haupteigenschaften sind Flexibilität, niedriges Gewicht, Teiltransparenz und geringe Herstellungskosten. Indiumzinnoxid (ITO), der aktuelle Industriestandard transparenter Elektrodentechnologie, ist nicht in der Lage, diese Eigenschaften zu gewährleisten. Dies liegt vor allem an der Brüchigkeit von ITO und der begrenzten Verfügbarkeit von Indium, welche mit einem hohen Preis einhergeht. Das Ziel dieser Dissertation ist die Integration einer alternativen und vielversprechenden Elektrodentechnologie: Netzwerke aus Silbernanodrähten (AgNWs). Mit einem Schichtwiderstand von 12 Ohm/sq bei einer Transmission von 84% (inklusive Glassubstrat) besitzen sie ähnliche oder sogar bessere optische und elektrische Eigenschaften als ITO. Des Weiteren sind AgNW-Elektroden flexibler und kostengünstiger als ITO und aus flüssiger Phase prozessierbar. Es gibt allerdings zwei Herausforderungen, welche die Integration als Grundelektrode in OSZ erschweren. Zum einen sind AgNW-Netzwerke sehr rauh, sodass organische Bauteile kurzgeschlossen werden. Zum anderen weisen AgNW-Elektroden, im Gegensatz zu einer vollflächigen ITO-Schicht, Lücken zwischen den einzelnen Drähten auf. Diese Lücken müssen von den organischen Schichten der OSZ elektrisch überbrückt werden. Im ersten Teil der Arbeit werden daher flüssigprozessierte Ladungsträgertransportschichten aus kleinen Molekülen untersucht, welche die AgNW-Elektroden glätten und die verhältnismäßig großen Lücken füllen sollen. Im Falle von Lochleitschichten (HTL) wird BF-DPB als Matrix und NDP9 als Dotand in Tetrahydrofuran gelöst und zur Anwendung gebracht. BF-DPB wird dabei schon in Lösung von NDP9 dotiert, wobei sich ein Hybridmolekülkomplex ausbildet. Die Leitfähigkeit der entstehenden Schichten ist ähnlich zu Referenzschichten, die durch thermisches Verdampfen im Hochvakuum hergestellt wurden. Die erhaltenen HTLs glätten die AgNW-Elektroden, sodass DCV5T-Me:C60-Solarzellen mit einer Effizienz von maximal 4.4% hergestellt werden können. Weiterhin wird der Einfluss der quadratmikrometergroßen Löcher auf die makroskopische Effizienz der Solarzelle in Abhängigkeit der HTL Leitfähigkeit untersucht. Um signifikante Effizienzverluste zu verhindern, muss der HTL eine minimale Leitfähigkeit von etwa 1e−4 S/cm aufweisen. Simulationen eines Ersatzschaltkreises bestätigen hierbei die experimentellen Ergebnisse. Im zweiten Teil der Arbeit wird eine Planarisierungsmethode untersucht, in welcher die AgNWs in nichtleitfähigen Polymeren eingebettet werden. Diese Polymere fungieren anschließend als flexibles Substrat. Der optische Kleber ”NOA63” erzielt hierbei die besten Ergebnisse. Die Rauheit der AgNW-Elektroden wird von etwa 30 nm auf 1 bis 3 nm stark reduziert. Anschließend werden diese AgNW-Elektroden in zwei unterschiedlichen OSZ Konfigurationen getestet und mit einer vollflexiblen Schicht aus Aluminiumoxid gegen Wasserdampfpermeation verkapselt. Somit können maximale Effizienzen von 5% mithilfe einer organischen Kaskadenstruktur und 5.6% mit DCV5T-Me:C60 OSZ erreicht werden. Um die Anwendbarkeit dieser vollflexiblen und verkapselten OSZ zu bewerten, werden Alterungsstudien unter konstanter Beleuchtung und feuchtem Klima durchgeführt. Es wird gezeigt, dass die in das Polymer eingebettete AgNW-Elektrode aufgrund von Photooxidation und -schwefelung und Photo- und Elektromigration instabil ist. Dieser Sachverhalt ist für die Anwendung von AgNW-Elektroden in kommerziellen OSZ von großer Bedeutung und wurde in der Forschung bisher nicht ausreichend thematisiert.

We demonstrate a new approach for fabricating alternating current driven organic electroluminescent devices using the concept of doping in organic semiconductors. Doped charge transport layers are used for generation of charge carriers within the device, hence eliminating the need for injecting charge carriers from external electrodes. The device is an organic-inorganic hybrid: We exploit the mechanical strength and chemical stability of inorganic semiconductors and combine it with better optical properties of organic materials whose emission color can be chemically tuned so that it covers the entire visible spectrum. The device consists of an organic electroluminescence (EL) layer composed of unipolar/ambipolar charge transport materials doped with organic dyes (10 wt% ) as well as molecularly doped charge generation layers enclosed between a pair of transparent insulating metal oxide layers. A transparent indium doped tin oxide (ITO) layer acts as bottom electrode for light outcoupling and Aluminium (Al) as top reflective electrode. The electrodes are for applying field across the device and to charge the device, instead of injection of charge carriers in case of direct current (DC) devices. Bright luminance of up to 5000 cd m-2 is observed when the device is driven with an alternating current (AC) bias. The luminance observed is attributed to charge carrier generation and recombination, leading to formation of excitons within the device, without injection of charge carriers through external electrodes.

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The thesis describes utilizing mass spectrometry and computational methods to study two groups of molecular systems: small organic molecules and oligopeptides. The gas-phase acidities were measured and the structures of the molecular species were calculated. The small molecules investigated included methylparaben, ibuprofen, and triclosan, all known to have some biological activity. The gas-phase acidity measurements made for these small molecules had the solvent and collisional gas pressures adjusted in order to observe their potential influences. The results obtained provide insight into the ion chemistry of these molecules and how the energetics may change the observed behavior of the ion as well as the resulting thermochemical properties measured. The oligopeptides studied were a family of tri-peptides in which a cysteine probe was placed within an alanine backbone. The cysteine probe was either in the L- or D- configuration in order to detect any fundamental differences among the diastereotopic peptides. Compared to the L-cysteine isomers, the D-cysteine peptides appear to display a change in gas-phase behavior and their respective dissociation profiles. These changes may have an implication of altering the biochemical properties when chirality changes in biological systems.