The thesis primarily focuses on the pressure influence on the reaction rate of char gasification using laboratory thermogravimetric analysis (TGA). It discusses also the gasification of char with a mixture of gasifying agents (CO2 + steam) under a pressure of 40 bar and temperatures up to 1100°C, which has not been reported in the literature to the best of found knowledge. The first section investigates the pressure impact on char gasification kinetics by varying the total and partial pressure of the gasifying agent. The second section investigates the effect of gasifying agent at 40 bar and combining the pyrolysis step in the investigation, which was done in-situ under inert atmosphere. Then, mixtures of the two gasifying agents were used for the gasification in separate experiments. The third section uses raw coal as material and gives attention to the char structure formed after the pyrolysis under the high pressure. The fourth section includes measurements for char characteristics during the gasification reaction and compares them with the reference char data performed previously in this research group under atmospheric pressure.:Abstract 1. Introduction 1 1.1 Scope of the thesis 1 1.2 Layout of the thesis 2 2. Literature Review 4 2.1 Background 4 2.2 Coal and gasification 5 2.2.1 Coal classification and characteristics 5 2.2.2 Introduction to gasification process 7 2.2.3 Coal Analysis 10 2.2.4 Pyrolysis 13 2.2.5 Gasification reactions 13 2.2.6 Mechanism of solid-gas reaction and Thermodynamic background 14 2.2.7 Regimes of gas-Solid Reactions 17 2.2.8 Summary 19 2.3 Effect of Pressure on gasification process 20 2.3.1 Advantages of high-pressure operation 20 2.3.2 Influence on the pyrolysis step 20 2.3.3 Effect of Pressure on coal swelling 21 2.3.4 Pressure influence on char morphology 23 2.3.5 Effect of pyrolysis pressure on char surface area 23 2.3.6 Effect on reaction order n 24 2.3.7 Summary 24 2.4 Pressure influence on char gasification reaction kinetics 24 2.4.1 Pressure influence on gasification reaction kinetics 25 2.4.2 Summary 27 2.5 Char gasification using gasifying agent mixtures 27 2.5.1 Mechanism 29 2.5.2 The role of the inhibition and the catalytic effect 29 2.5.3 Summary 32 2.6 Thermodynamic aspects and the estimation of the reaction rate 32 2.6.1 Background 32 2.6.2 Basic definitions of reaction rate 34 2.6.3 Intrinsic kinetic models 35 2.6.4 Theoretical models 36 2.6.5 Empiric Models 39 2.6.6 Intrinsic kinetic models expressed by CO2 concentration 40 2.6.7 Arrhenius Activation Energy 40 2.6.8 Differentiation of a polynomial fit data (Differential method): 41 2.6.9 Summary 43 3. Experimental Analysis 44 3.1 Thermogravimetry 44 3.2 Testing of the gas volume fraction and the total pressure influence on char gasification 45 3.2.1 Testing of the gas volume fraction influence 45 3.2.2 Testing of system pressure influence on char gasification 56 3.2.3 Discussion 65 3.3 Coal gasification at 40 bar with pure CO2, H2O and their mixtures 65 3.3.1 Gasification with pure CO2 and H2O 66 3.3.2 Coal gasification using CO2 / H2O mixtures at high system pressure 87 3.3.3 Discussion 96 3.4 Pressure influence on coal gasification 100 3.4.1 Coal gasification under different system pressures 100 3.4.2 The effect of increasing pressure on coal morphology 104 3.4.3 Discussion 117 3.5 Influence of the pressure on the char properties during gasification 118 3.5.1 Discussion 129 4. General discussion 134 5. Conclusions 139 5.1 Significance of the findings 143 5.2 Recommendations 144 6. Appendix 146 6.1 Literature and Results 146 6.1.1 Conditions influence on gasification of the (a) temperature, (b) partial pressure 146 6.1.2 TGA-DMT 147 6.1.3 Testing of the gas volume fraction influence on coal gasification 148 6.1.4 Testing of system pressure influence on char gasification 150 6.1.5 Coal gasification at 40 bar with pure CO2, H2O and their mixtures 152 6.1.6 Coal gasification under different pressures 162 6.1.7 Summary of gas mixture gasification studies 167 6.2 Figures Index 169 6.3 Tables Index 175 6.4 References 177

To meet the global hydrocarbon energy demand, it is imperative either to enhance the production from existing fields by applying innovative engineering solutions or discovering new field /resource areas. Both of these options are investigated by petroleum engineers intensively to tackle the challenges of meeting the ever-increasing demand. Meeting the energy demand as, like any other developing country, Jordan is facing a formidable challenge and requires exploration for conventional and unconventional hydrocarbon resources. As Jordan has a long exploration history for conventional reservoirs, Unconventional resource exploration and production seems to be the way to find new energy sources. Different exploration wells were drilled to evaluate the hydrocarbon potential. This research work is focusing on an experimental investigation to evaluate Jordanian hydrocarbon potential as well as to provide recommendations for future exploration activities in shale resources. The Evaluations were performed through comprehensive laboratory experiments that include measurements of Total Organic Content, Grain density, Pore Size Distribution, Specific Surface Area (BET), Mineralogy, Thermogravimetry Analysis, and Rock-Eval pyrolysis. The petrophysical properties (TOC, grain density, pore size distribution) of Jordanian shale (nine different wells) are investigated. The TOC and grain density are in an inversely proportional relationship. The TOC results show a gradual increment with the depth. All the samples have higher porosity dominated by macro pores. Fourteen (14) samples were selected primarily based on TOC (above 1.5%) for further analysis. The specific surface area results show a proportional relationship with the TOC content. Considering the petrophysical properties and mineralogy, these Jordanian shales broadly can be considered as high porosity clay and mudstone type of shale. Thermogravimetry analysis (TG/DTG) results indicate quantitative information related to organic and inorganic matter. Detection of thermos-reactive minerals, especially clay, carbonate, muscovite, pyrite is possible due to the combination of TG/DTG/DSC. The samples are examined under three different procedures which includes different heating programs. The oxidizing and inert atmospheric conditions (procedure i & ii) have the same heating program whereas procedure iii (inert atmospheric condition) has a heating program similar to the Rock-Eval pyrolysis program. The results of these samples show the complex nature of shale as well as organic matter by reacting in different stages (two or, three stages). Depending of the maturity of organic matter, the reaction occurring temperature range varies. Maximum oxidization reaction peaks happen between 479°C to 502°C. The maximum pyrolysis reaction peaks between 498°C to 521°C. Compared with complex heating (procedure iii) and rock Eval pyrolysis, S2 results indicate a high amount of inorganic compounds. Considering TGA reaction peaks and rock Eval pyrolysis results, these Jordanian shales indicate immature with low hydrocarbon generation potential. The Jordanian shale samples are analyzed by using Rock-Eval pyrolysis. Analysis results are used to interpret petroleum potential in rocks. The most important information includes organic matter types (also connected with the depositional settings), organic matter thermal maturity, and the remaining hydrocarbon generation potential in the current form. The organic geochemical analysis results indicate mostly poor to no source rock potential except JF2-760 samples. The hydrogen index (HI) and oxygen index (OI) result suggests that type iii kerogen and type iii/ iv kerogen are most likely from terrestrial and varied settings origin. The low hydrogen, as well as, low S2 value indicate very little hydrocarbon generation potential. Similarly, The Tmax and PI data indicate immature to early mature source rock status and low conversion scenario. Furthermore, the supercritical CO2 is injected into the samples, which is similar to gas flooding experiments to understand the recovery process. Hydrocarbon recovery or, CO2-shale interaction is determined by comparing three different properties (TOC, SSA, and TGA) pre-and-post supercritical CO2 injection. Supercritical CO2 injection in immature shale shows very limited property changes (TOC, SSA, and TGA) to the samples. However, in presence of hydrocarbon the pre-and post-injection property changes TOC, TGA, and SSA (BET) are noticeable enough to conclude HC recovery. Although in the case of immature shale with no hydrocarbon potential the kerogen or bitumen extraction has not been detected, which can be significant in the case of greenhouse gas storage, especially CCUS. This could reduce the risk of Organic Matter (OM) migration possibility in case immature shale formation is present in a suitable geological location.

It is known that boron containing compounds exhibit interesting chemical and physical properties. In the past 50 years modern preparative methods have led to an overwhelming number of different structures of novel and often unexpected boron–sulfur and boron–selenium compounds. Among all these new compounds, there was only one which comprises rare earth metal (RE), boron and heavier chalcogen, namely sulfur, the europium thioborate Eu[B2S4] [1]. Selenoborates of rare earth metals are hitherto unknown. On the other hand, rare earth oxoborates represent a well-known class of compounds [2] with a wide range of applications, especially in the field of optical materials. In addition, well-defined boron compounds containing the heavier group 16 elements are fairly difficult to prepare due to the high reactivity of in situ formed boron chalcogenides towards most container materials at elevated temperatures. The chalcogenoborates of the heavier chalcogens are sensitive against oxidation and hydrolysis and therefore have to be handled in an inert environment. Therefore, developing and optimization of preparative routes for the syntheses of pure and crystalline RE thio- and selenoborates was needed. In the course of this study, the application of different preparation routes, such as optimized high-temperature routes (HT), metathesis reactions and high-pressure high-temperature routes (Hp – HT), led to sixteen new rare earth thioborates. Their crystal structures were solved and/or refined from powder and single crystal X-ray diffraction data, while the local structure around rare earth metal was confirmed from the results of the EXAFS analyses. Quantum mechanical calculations were used within this work in order to investigate the arrangement of intrinsic vacancies on the boron sites in the crystal structures of rare earth thioborates. Thermal, magnetic and optical properties of these compounds are also discussed. The rare earth thioborates discovered during this work are the first examples of ternary thioborates containing trivalent cations. These compounds can be divided into two groups of isotypic compounds: the rare earth orthothioborates with general formula REIII[BS3] (RE = La – Nd, Sm, Gd and Tb) [3] and the rare earth thioborate sulfides with general formula REIII¦9B5S21, (RE = Gd – Lu, and Y) [4]. In the crystal structure of RE[BS3] (orthorhombic, space group Pna21, Z = 4), the sulfur atoms form the vertices of corrugated kagome nets, within which every second triangle is occupied by boron and the large hexagons are centered by RE cations. The structural features of the isotypic RE[BS3] phases show great similarities to those of rare earth oxoborates RE[BO3] and orthothioborates of alkali and alkaline earth metals as well as to thallium orthothioborate, yet pronounced differences are also observed: the [BS3]3– groups in the crystal structures of RE[BS3] are more distorted, where the distortion decreases with the decreasing size of the RE element, and the coordination environments of the [BS3]3– groups in the crystal structures of RE[BS3] are different in comparison with the coordination environments of the [BO3]3– groups in the crystal structures of λ-Nd[BO3] [5] and of o-Ce[BO3] [6]. The results of the IR and Raman investigations are in agreement with the presence of [BS3]3– anions in the crystal structure of RE[BS3]. Thermal analyses revealed the thermal stability of these compounds under inert conditions up to ~ 1200 K. Analyses of the magnetic properties of the Sm, Gd and Tb thioborates showed that both Gd and Tb phases order antiferromagnetically. The magnetic susceptibility for Sm orthothioborate approximately follows the Van-Vleck theory for Sm3+. Between 50 K and 62 K a transition appears which is independent of the magnetic field: the magnetic susceptibility becomes lower. This effect might indicate a discontinuous valence transition of Sm which was further investigated by means of XANES and X-ray diffraction using synchrotron radiation, both at low temperatures. The series of isotypic RE thioborate sulfides with composition RE9B5S21, was obtained by the application of Hp – HT conditions to starting mixtures with the initial chemical composition “REB3S6“, after careful optimization of the pressure, temperature and treatment time, as well as the composition of the starting mixtures. Their crystal structures adopt the Ce6Al3.33S14 [7] structure type (hexagonal, space group P63, Z = 2/3). The special features of the RE9B5S21 crystal structures, concerning boron site occupancies and different coordination environments of the two crystallographically independent boron sites, were investigated in more detail by means of quantum chemical calculations, electron diffraction methods, optical and X-ray absorption spectroscopy as well as by 11B NMR spectroscopy. The results obtained from these different experimental and computational methods are in good mutual agreement. The crystal structures of the RE9B5S21 compounds are characterized by two types of anions: tetrahedral [BS4]5– and trigonal planar [BS3]3– as well as [(S2–)3] units. Isolated [BS4]5– tetrahedra (all pointing with one of their apices along the polar [001] direction) represent a unique feature of the crystal structure which is observed for the first time in a thioborate compound. These tetrahedra are stacked along the three-fold rotation axes. Vacancies are located at the trigonal-planar coordinated boron site with preferred ordering –B–B––B–B–– along [001]. No superstructure is observed by means of electron diffraction methods as adjacent columns are shuffled along the c axis, giving rise to a randomly distributed vacancy pattern. Positions of the sulfur atoms within the [(S2–)3] substructure as well as planarity of the [BS3]3– units were investigated in more detail by means of quantum mechanical calculations. Results of the IR and Raman spectroscopy, as well as of the 11B NMR spectroscopy are in agreement with the presence of the boron atoms in two different coordination environments. Thermal analyses showed that compounds RE9B5S21 are stable under inert conditions up to ~ 1200 K. In accordance with the combined results of experimental and computational investigations, the chemical formula of the RE9B5S21 compounds is consistent with RE3[BS3]2[BS4]3S3. A short overview of investigations towards rare earth selenoborates, where in most of the cases only known binary rare earth selenides could be identified, is presented as well in this work. Investigations in the RE–B–Se systems were conducted by the application of different preparation routes by varying the experimental parameters and the initial compositions of the starting mixtures. Although no crystal structure of a ternary phase in these systems could be solved, there are indications that such phases exist, but further investigations are needed. [1] M. Döch, A. Hammerschmidt, B. Krebs, Z. Anorg. Allg. Chem., 2004, 630, 519. [2] H. Huppertz, Chem. Commun., 2011, 47, 131; and references therein. [3] J. Hunger, M. Borna, R. Kniep, J. Solid State Chem., 2010, 182, 702; J. Hunger, M. Borna, R. Kniep, Z. Kristallogr. NCS, 2010, 225, 217; M. Borna, J. Hunger, R. Kniep, Z. Kristallogr. NCS, 2010, 225, 223; M. Borna, J. Hunger, R. Kniep, Z. Kristallogr. NCS, 2010, 225, 225. [4] M. Borna, J. Hunger, A. Ormeci, D. Zahn, U. Burkhardt, W. Carrillo-Cabrera, R. Cardoso-Gil, R. Kniep, J. Solid State Chem., 2011, 184, 296; [5] H. Müller-Bunz, T. Nikelski, Th. Schleid, Z. Naturforsch. B, 2003, 58, 375. [6] H. U. Bambauer, J. Weidelt, J.-St. Ysker, Z. Kristallogr., 1969, 130, 207. [7] D. de Saint-Giniez, P. Laruelle, J. Flahaut, C. R. Séances, Acad. Sci. Ser. C, 1968, 267, 1029.

In der vorliegenden Arbeit wurden Thiophenoligomere nach dem Konzept Akzeptor – Donator – Akzeptor (A-D-A) und Donator – Akzeptor – Donator (D-A-D) synthetisiert und umfassend charakterisiert. Oligothiophene unterschiedlicher Kettenlänge stellen dabei den Donatoranteil des Moleküls dar, während 2,2-Dicyanovinyle (DCV), 1,3,2-2H-Dioxaborine (DOB), 2,1,3-Benzothiadiazole (BTDA) die Akzeptorstruktur im Molekül repräsentieren. Diese Materialien sollen als Absorber in der intrinsischen Schicht von organischen Solarzellen (OSC) eingesetzt werden. Zusätzliche Untersuchungen an DOB-substituierten Fluorenen, die als Elektronentransportmaterialien in der n-Schicht von OSC Anwendung finden sollten, erwiesen sich in diesem Fall nicht als vielversprechend. Alle untersuchten Verbindungen wurden, abhängig von ihrer Löslichkeit bzw. Verdampfbarkeit im Vakuum, durch Absorption in Lösung und im dünnen Film, durch Cyclovoltammetrie (CV) und durch DFT-Rechnung charakterisiert. Die thermische Stabilität wurde durch TG/DTA-Messungen untersucht. Die Ladungsträgerbeweglichkeit der DCV-Verbindungen wurde in organischen Feldeffekttransistoren untersucht, sowie Solarzellen mit verschiedenen Schichtdicken der Quinquethiophenverbindung DCV2-5T als Donatormaterial der intrinsischen Schicht angefertigt. Eine gezielte Modifikation der Verbindungen durch Wahl des Akzeptors und die Länge des aromatischen Systems ermöglichte die Synthese von Molekülen mit abstimmbaren Eigenschaften. Eine bathochrome Verschiebung des Absorptionsmaximums kann durch eine Vergrößerung des π-Systems erreicht werden. CV-Messungen und DFT-Rechnungen zeigen, dass E(LUMO) maßgeblich vom Akzeptor bestimmt wird, während E(HOMO) mehr durch den Donatorteil des Moleküls beeinflusst wird. Diese Eigenschaften sind unabhängig vom Aufbau (A-D-A oder D-A-D) der Verbindungen. Bezüglich der thermischen Stabilität sind die D-A-D – Verbindungen gegenüber den A-D-A – Verbindungen zu favorisieren. Ein weiterer wichtiger Schlüsselpunkt der Arbeit ist die Erkenntnis, dass die bisher verwendeten Alkylketten am Rückgrat des Oligothiophens die Löcherbeweglichkeit der Verbindungen stark herabsetzen. Zwei Solarzellen in einer m-i-p– Anordnung (Metall – intrinsisch – p-dotiert) erreichen mit dem DCV2-5T (Schichtdicke 6 bzw. 10 nm) als Donatormaterial eine Effizienz von 2.8 %. Die Zellen zeichnen sich durch einen hohen Füllfaktor (bis zu 58 %) aus und erreichen eine Leerlaufspannung von bis zu 1.03 V. Die Interpretation der J-V-Kennlinien führt zu der Annahme, dass die Exzitonendiffusionslänge kürzer als 10 nm ist, weswegen es bei einer höheren Schichtdicke des Thiophens zu einer Rekombination der erzeugten Exzitonen kommt. / The present thesis deals with thiophene oligomers according to the concept acceptor-donor-acceptor (A-D-A) or donor-acceptor-donor (D-A-D). Thiophenes represent the donor-part of the molecule whereas the acceptor-part can either be 2,2-dicyanovinyle (DCV), 1,3,2-2H-dioxaborine (DOB) or 2,1,3-benzothiadiazole (BTDA). These materials are supposed to work as absorbers in the intrinsic layer of an organic small molecular solar cell (OSC). Additional studies on substituted fluorenes, however, known to work as electron transport material in the n-layer of OSC, have not proved promising in this case. Depending on their solubility in organic solvents or their suitability for vacuum sublimation, all compounds were characterised by absorption measurements in solution and thin film, cyclic voltammetry (CV) and DFT-calculations. The thermal stability was determined by thermal analysis. Charge carrier mobility measurements using organic field effect transistors were applied to investigate the DCV-compounds. The quinquethiophene DCV2-5T was used in varying thicknesses as a donor material in the intrinsic absorbing layer of an OSC. Systematic variation of the compounds by applying different accepting groups and/or modifying the lengths of the aromatic systems permitted the synthesis of molecules with tunable properties. A bathochromic shift of the absorption maximum can be achieved by increasing the number of thiophene units. CV measurements and DFT calculations reveal a dependency of E(LUMO) on the accepting group whereas E(HOMO) is more influenced by the donor part of the molecule. These properties are independent from the concept A-D-A or D-A-D. Concerning thermal stability, D-A-D compounds seem to be more stable than A-D-A materials. Another important point is the knowledge that alkyl chains used so far at the backbone of the oligothiophene chain significantly decrease the hole mobility. Two OSCs arranged in an m-i-p-stack (metal – intrinsic – p-doped) with the quinquethiophene DCV2-5T (layer thickness 6 and 10 nm) both reach an efficiency of 2.8 %. They show a high fillfactor (up to 58 %) and reach an open circuit voltage of 1.03 V. Interpretation of the other parameters leads to the assumption that the exciton diffusion length of the molecule is shorter than 10 nm. This results in a recombination of the excitons in the cell with the thicker layer of DCV2-5T.

In der vorliegenden Arbeit wurden Thiophenoligomere nach dem Konzept Akzeptor – Donator – Akzeptor (A-D-A) und Donator – Akzeptor – Donator (D-A-D) synthetisiert und umfassend charakterisiert. Oligothiophene unterschiedlicher Kettenlänge stellen dabei den Donatoranteil des Moleküls dar, während 2,2-Dicyanovinyle (DCV), 1,3,2-2H-Dioxaborine (DOB), 2,1,3-Benzothiadiazole (BTDA) die Akzeptorstruktur im Molekül repräsentieren. Diese Materialien sollen als Absorber in der intrinsischen Schicht von organischen Solarzellen (OSC) eingesetzt werden. Zusätzliche Untersuchungen an DOB-substituierten Fluorenen, die als Elektronentransportmaterialien in der n-Schicht von OSC Anwendung finden sollten, erwiesen sich in diesem Fall nicht als vielversprechend. Alle untersuchten Verbindungen wurden, abhängig von ihrer Löslichkeit bzw. Verdampfbarkeit im Vakuum, durch Absorption in Lösung und im dünnen Film, durch Cyclovoltammetrie (CV) und durch DFT-Rechnung charakterisiert. Die thermische Stabilität wurde durch TG/DTA-Messungen untersucht. Die Ladungsträgerbeweglichkeit der DCV-Verbindungen wurde in organischen Feldeffekttransistoren untersucht, sowie Solarzellen mit verschiedenen Schichtdicken der Quinquethiophenverbindung DCV2-5T als Donatormaterial der intrinsischen Schicht angefertigt. Eine gezielte Modifikation der Verbindungen durch Wahl des Akzeptors und die Länge des aromatischen Systems ermöglichte die Synthese von Molekülen mit abstimmbaren Eigenschaften. Eine bathochrome Verschiebung des Absorptionsmaximums kann durch eine Vergrößerung des π-Systems erreicht werden. CV-Messungen und DFT-Rechnungen zeigen, dass E(LUMO) maßgeblich vom Akzeptor bestimmt wird, während E(HOMO) mehr durch den Donatorteil des Moleküls beeinflusst wird. Diese Eigenschaften sind unabhängig vom Aufbau (A-D-A oder D-A-D) der Verbindungen. Bezüglich der thermischen Stabilität sind die D-A-D – Verbindungen gegenüber den A-D-A – Verbindungen zu favorisieren. Ein weiterer wichtiger Schlüsselpunkt der Arbeit ist die Erkenntnis, dass die bisher verwendeten Alkylketten am Rückgrat des Oligothiophens die Löcherbeweglichkeit der Verbindungen stark herabsetzen. Zwei Solarzellen in einer m-i-p– Anordnung (Metall – intrinsisch – p-dotiert) erreichen mit dem DCV2-5T (Schichtdicke 6 bzw. 10 nm) als Donatormaterial eine Effizienz von 2.8 %. Die Zellen zeichnen sich durch einen hohen Füllfaktor (bis zu 58 %) aus und erreichen eine Leerlaufspannung von bis zu 1.03 V. Die Interpretation der J-V-Kennlinien führt zu der Annahme, dass die Exzitonendiffusionslänge kürzer als 10 nm ist, weswegen es bei einer höheren Schichtdicke des Thiophens zu einer Rekombination der erzeugten Exzitonen kommt.:Abstract 1 Kurzfassung 2 Tagungsbeiträge und Veröffentlichungen 3 1 Einleitung und Problemstellung 5 2 Physikalische Grundlagen 9 2.1 Organische Halbleiter 9 2.2 Aufbau und Funktionsweise organischer Solarzellen 11 2.3 Wichtige Parameter zur Charakterisierung organischer Solarzellen 16 2.4 Messmethoden zur Bestimmung der Grenzorbitale 17 2.4.1 Cyclovoltammetrie (CV) 17 2.4.2 DFT-Rechnungen 22 3 Motivation 25 4 Bisheriger Kenntnisstand 29 4.1 Absorbermaterialien der intrinsischen Schicht 29 4.1.1 Phthalocyanine (MPc (M = Zn, Cu)) 29 4.1.2 Oligothiophene 31 4.1.3 Fulleren C60 33 4.2 n-Leiter 35 4.2.1 Fulleren C60 (dotiert) 35 4.2.2 Bathophenanthrolin (BPhen) und Bathocuproin (BCP) 36 4.2.3 Transparenter n-Leiter: Naphthalentetracarboxyl Dianhydrid (NTCDA) 38 4.3 „Bandgap engineering“ – Zusammenspiel zwischen Donator und Akzeptor 39 4.3.1 Dicyanovinyle 41 4.3.2 1,3,2-(2H)-Dioxaborine 41 4.3.3 2,1,3-Benzothiadiazole 43 4.4 Thiophene 44 4.4.1 Ringaufbauende Reaktionen 44 4.4.2 Substitutionsmöglichkeiten am Thiophen 47 4.4.3 Übergangsmetallkatalysierte Kupplungsreaktionen zum Aufbau von Oligothiophenketten 48 4.5 Fluorene 49 5 Ergebnisse und Diskussion 51 5.1 Akzeptorsubstituierte Oligothiophene 51 5.1.1 Akzeptor-Donator-Akzeptor-Strukturen 51 5.1.1 Donator-Akzeptor-Donator-Strukturen 57 5.2 Fluorene 64 5.3 Unsymmetrische Donator-Akzeptor-Verbindungen mit neuen Akzeptoren – Ausgangspunkt für zukünftige Forschung 65 5.4 Auswertung und Vergleich physikalischer Messungen 66 5.4.1 Absorptionsmessungen in Lösung und im Film 66 5.4.2 Ergebnisse aus Cyclovoltammetrie-Messungen 75 5.4.3 Ergebnisse aus DFT-Rechnungen 85 5.4.4 Thermogravimetrie und Differentialthermoanalyse-Messungen 91 5.4.5 Beweglichkeitsmessungen 104 5.4.6 Eintragung der erhaltenen Ergebnisse ins Spinnennetzdiagramm und ihre Bewertung 107 5.4.7 Solarzelle mit DCV2-5T 116 6 Zusammenfassung und Ausblick 121 6.1 Zusammenfassung 121 6.2 Ausblick 123 7 Experimenteller Teil 125 7.1 Allgemeine Angaben 125 7.2 Synthese und Charakterisierung der akzeptorsubstituierten Oligomere 128 7.3 Synthese und Charakterisierung der Fluorenverbindungen 160 7.4 Synthese und Charakterisierung unsymmetrischer Donator-Akzeptor-Verbindungen mit neuen Akzeptoren 167 8 Anhang 173 8.1 Abkürzungs- und Trivialnamenverzeichnis 173 8.2 Literaturverzeichnis 176 Danksagung 181 Versicherung 183 / The present thesis deals with thiophene oligomers according to the concept acceptor-donor-acceptor (A-D-A) or donor-acceptor-donor (D-A-D). Thiophenes represent the donor-part of the molecule whereas the acceptor-part can either be 2,2-dicyanovinyle (DCV), 1,3,2-2H-dioxaborine (DOB) or 2,1,3-benzothiadiazole (BTDA). These materials are supposed to work as absorbers in the intrinsic layer of an organic small molecular solar cell (OSC). Additional studies on substituted fluorenes, however, known to work as electron transport material in the n-layer of OSC, have not proved promising in this case. Depending on their solubility in organic solvents or their suitability for vacuum sublimation, all compounds were characterised by absorption measurements in solution and thin film, cyclic voltammetry (CV) and DFT-calculations. The thermal stability was determined by thermal analysis. Charge carrier mobility measurements using organic field effect transistors were applied to investigate the DCV-compounds. The quinquethiophene DCV2-5T was used in varying thicknesses as a donor material in the intrinsic absorbing layer of an OSC. Systematic variation of the compounds by applying different accepting groups and/or modifying the lengths of the aromatic systems permitted the synthesis of molecules with tunable properties. A bathochromic shift of the absorption maximum can be achieved by increasing the number of thiophene units. CV measurements and DFT calculations reveal a dependency of E(LUMO) on the accepting group whereas E(HOMO) is more influenced by the donor part of the molecule. These properties are independent from the concept A-D-A or D-A-D. Concerning thermal stability, D-A-D compounds seem to be more stable than A-D-A materials. Another important point is the knowledge that alkyl chains used so far at the backbone of the oligothiophene chain significantly decrease the hole mobility. Two OSCs arranged in an m-i-p-stack (metal – intrinsic – p-doped) with the quinquethiophene DCV2-5T (layer thickness 6 and 10 nm) both reach an efficiency of 2.8 %. They show a high fillfactor (up to 58 %) and reach an open circuit voltage of 1.03 V. Interpretation of the other parameters leads to the assumption that the exciton diffusion length of the molecule is shorter than 10 nm. This results in a recombination of the excitons in the cell with the thicker layer of DCV2-5T.:Abstract 1 Kurzfassung 2 Tagungsbeiträge und Veröffentlichungen 3 1 Einleitung und Problemstellung 5 2 Physikalische Grundlagen 9 2.1 Organische Halbleiter 9 2.2 Aufbau und Funktionsweise organischer Solarzellen 11 2.3 Wichtige Parameter zur Charakterisierung organischer Solarzellen 16 2.4 Messmethoden zur Bestimmung der Grenzorbitale 17 2.4.1 Cyclovoltammetrie (CV) 17 2.4.2 DFT-Rechnungen 22 3 Motivation 25 4 Bisheriger Kenntnisstand 29 4.1 Absorbermaterialien der intrinsischen Schicht 29 4.1.1 Phthalocyanine (MPc (M = Zn, Cu)) 29 4.1.2 Oligothiophene 31 4.1.3 Fulleren C60 33 4.2 n-Leiter 35 4.2.1 Fulleren C60 (dotiert) 35 4.2.2 Bathophenanthrolin (BPhen) und Bathocuproin (BCP) 36 4.2.3 Transparenter n-Leiter: Naphthalentetracarboxyl Dianhydrid (NTCDA) 38 4.3 „Bandgap engineering“ – Zusammenspiel zwischen Donator und Akzeptor 39 4.3.1 Dicyanovinyle 41 4.3.2 1,3,2-(2H)-Dioxaborine 41 4.3.3 2,1,3-Benzothiadiazole 43 4.4 Thiophene 44 4.4.1 Ringaufbauende Reaktionen 44 4.4.2 Substitutionsmöglichkeiten am Thiophen 47 4.4.3 Übergangsmetallkatalysierte Kupplungsreaktionen zum Aufbau von Oligothiophenketten 48 4.5 Fluorene 49 5 Ergebnisse und Diskussion 51 5.1 Akzeptorsubstituierte Oligothiophene 51 5.1.1 Akzeptor-Donator-Akzeptor-Strukturen 51 5.1.1 Donator-Akzeptor-Donator-Strukturen 57 5.2 Fluorene 64 5.3 Unsymmetrische Donator-Akzeptor-Verbindungen mit neuen Akzeptoren – Ausgangspunkt für zukünftige Forschung 65 5.4 Auswertung und Vergleich physikalischer Messungen 66 5.4.1 Absorptionsmessungen in Lösung und im Film 66 5.4.2 Ergebnisse aus Cyclovoltammetrie-Messungen 75 5.4.3 Ergebnisse aus DFT-Rechnungen 85 5.4.4 Thermogravimetrie und Differentialthermoanalyse-Messungen 91 5.4.5 Beweglichkeitsmessungen 104 5.4.6 Eintragung der erhaltenen Ergebnisse ins Spinnennetzdiagramm und ihre Bewertung 107 5.4.7 Solarzelle mit DCV2-5T 116 6 Zusammenfassung und Ausblick 121 6.1 Zusammenfassung 121 6.2 Ausblick 123 7 Experimenteller Teil 125 7.1 Allgemeine Angaben 125 7.2 Synthese und Charakterisierung der akzeptorsubstituierten Oligomere 128 7.3 Synthese und Charakterisierung der Fluorenverbindungen 160 7.4 Synthese und Charakterisierung unsymmetrischer Donator-Akzeptor-Verbindungen mit neuen Akzeptoren 167 8 Anhang 173 8.1 Abkürzungs- und Trivialnamenverzeichnis 173 8.2 Literaturverzeichnis 176 Danksagung 181 Versicherung 183

It is known that boron containing compounds exhibit interesting chemical and physical properties. In the past 50 years modern preparative methods have led to an overwhelming number of different structures of novel and often unexpected boron–sulfur and boron–selenium compounds. Among all these new compounds, there was only one which comprises rare earth metal (RE), boron and heavier chalcogen, namely sulfur, the europium thioborate Eu[B2S4] [1]. Selenoborates of rare earth metals are hitherto unknown. On the other hand, rare earth oxoborates represent a well-known class of compounds [2] with a wide range of applications, especially in the field of optical materials. In addition, well-defined boron compounds containing the heavier group 16 elements are fairly difficult to prepare due to the high reactivity of in situ formed boron chalcogenides towards most container materials at elevated temperatures. The chalcogenoborates of the heavier chalcogens are sensitive against oxidation and hydrolysis and therefore have to be handled in an inert environment. Therefore, developing and optimization of preparative routes for the syntheses of pure and crystalline RE thio- and selenoborates was needed. In the course of this study, the application of different preparation routes, such as optimized high-temperature routes (HT), metathesis reactions and high-pressure high-temperature routes (Hp – HT), led to sixteen new rare earth thioborates. Their crystal structures were solved and/or refined from powder and single crystal X-ray diffraction data, while the local structure around rare earth metal was confirmed from the results of the EXAFS analyses. Quantum mechanical calculations were used within this work in order to investigate the arrangement of intrinsic vacancies on the boron sites in the crystal structures of rare earth thioborates. Thermal, magnetic and optical properties of these compounds are also discussed. The rare earth thioborates discovered during this work are the first examples of ternary thioborates containing trivalent cations. These compounds can be divided into two groups of isotypic compounds: the rare earth orthothioborates with general formula REIII[BS3] (RE = La – Nd, Sm, Gd and Tb) [3] and the rare earth thioborate sulfides with general formula REIII¦9B5S21, (RE = Gd – Lu, and Y) [4]. In the crystal structure of RE[BS3] (orthorhombic, space group Pna21, Z = 4), the sulfur atoms form the vertices of corrugated kagome nets, within which every second triangle is occupied by boron and the large hexagons are centered by RE cations. The structural features of the isotypic RE[BS3] phases show great similarities to those of rare earth oxoborates RE[BO3] and orthothioborates of alkali and alkaline earth metals as well as to thallium orthothioborate, yet pronounced differences are also observed: the [BS3]3– groups in the crystal structures of RE[BS3] are more distorted, where the distortion decreases with the decreasing size of the RE element, and the coordination environments of the [BS3]3– groups in the crystal structures of RE[BS3] are different in comparison with the coordination environments of the [BO3]3– groups in the crystal structures of λ-Nd[BO3] [5] and of o-Ce[BO3] [6]. The results of the IR and Raman investigations are in agreement with the presence of [BS3]3– anions in the crystal structure of RE[BS3]. Thermal analyses revealed the thermal stability of these compounds under inert conditions up to ~ 1200 K. Analyses of the magnetic properties of the Sm, Gd and Tb thioborates showed that both Gd and Tb phases order antiferromagnetically. The magnetic susceptibility for Sm orthothioborate approximately follows the Van-Vleck theory for Sm3+. Between 50 K and 62 K a transition appears which is independent of the magnetic field: the magnetic susceptibility becomes lower. This effect might indicate a discontinuous valence transition of Sm which was further investigated by means of XANES and X-ray diffraction using synchrotron radiation, both at low temperatures. The series of isotypic RE thioborate sulfides with composition RE9B5S21, was obtained by the application of Hp – HT conditions to starting mixtures with the initial chemical composition “REB3S6“, after careful optimization of the pressure, temperature and treatment time, as well as the composition of the starting mixtures. Their crystal structures adopt the Ce6Al3.33S14 [7] structure type (hexagonal, space group P63, Z = 2/3). The special features of the RE9B5S21 crystal structures, concerning boron site occupancies and different coordination environments of the two crystallographically independent boron sites, were investigated in more detail by means of quantum chemical calculations, electron diffraction methods, optical and X-ray absorption spectroscopy as well as by 11B NMR spectroscopy. The results obtained from these different experimental and computational methods are in good mutual agreement. The crystal structures of the RE9B5S21 compounds are characterized by two types of anions: tetrahedral [BS4]5– and trigonal planar [BS3]3– as well as [(S2–)3] units. Isolated [BS4]5– tetrahedra (all pointing with one of their apices along the polar [001] direction) represent a unique feature of the crystal structure which is observed for the first time in a thioborate compound. These tetrahedra are stacked along the three-fold rotation axes. Vacancies are located at the trigonal-planar coordinated boron site with preferred ordering –B–B––B–B–– along [001]. No superstructure is observed by means of electron diffraction methods as adjacent columns are shuffled along the c axis, giving rise to a randomly distributed vacancy pattern. Positions of the sulfur atoms within the [(S2–)3] substructure as well as planarity of the [BS3]3– units were investigated in more detail by means of quantum mechanical calculations. Results of the IR and Raman spectroscopy, as well as of the 11B NMR spectroscopy are in agreement with the presence of the boron atoms in two different coordination environments. Thermal analyses showed that compounds RE9B5S21 are stable under inert conditions up to ~ 1200 K. In accordance with the combined results of experimental and computational investigations, the chemical formula of the RE9B5S21 compounds is consistent with RE3[BS3]2[BS4]3S3. A short overview of investigations towards rare earth selenoborates, where in most of the cases only known binary rare earth selenides could be identified, is presented as well in this work. Investigations in the RE–B–Se systems were conducted by the application of different preparation routes by varying the experimental parameters and the initial compositions of the starting mixtures. Although no crystal structure of a ternary phase in these systems could be solved, there are indications that such phases exist, but further investigations are needed. [1] M. Döch, A. Hammerschmidt, B. Krebs, Z. Anorg. Allg. Chem., 2004, 630, 519. [2] H. Huppertz, Chem. Commun., 2011, 47, 131; and references therein. [3] J. Hunger, M. Borna, R. Kniep, J. Solid State Chem., 2010, 182, 702; J. Hunger, M. Borna, R. Kniep, Z. Kristallogr. NCS, 2010, 225, 217; M. Borna, J. Hunger, R. Kniep, Z. Kristallogr. NCS, 2010, 225, 223; M. Borna, J. Hunger, R. Kniep, Z. Kristallogr. NCS, 2010, 225, 225. [4] M. Borna, J. Hunger, A. Ormeci, D. Zahn, U. Burkhardt, W. Carrillo-Cabrera, R. Cardoso-Gil, R. Kniep, J. Solid State Chem., 2011, 184, 296; [5] H. Müller-Bunz, T. Nikelski, Th. Schleid, Z. Naturforsch. B, 2003, 58, 375. [6] H. U. Bambauer, J. Weidelt, J.-St. Ysker, Z. Kristallogr., 1969, 130, 207. [7] D. de Saint-Giniez, P. Laruelle, J. Flahaut, C. R. Séances, Acad. Sci. Ser. C, 1968, 267, 1029.:I INTRODUCTION ......................................................................... 7 1. Motivation and scope of the work .............................................. 9 2. Literature overview .................................................................. 11 2.1. The binary subsystems of the ternary systems RE–B–Q (RE = rare earth metals, Y; Q = S, Se) ......................................................... 12 2.1.1. RE–Q ............................................................................... 12 2.1.2. RE–B ............................................................................... 19 2.1.3. B–Q ................................................................................. 22 2.2. Related ternary compounds ................................................... 25 2.2.1. RE oxoborates .................................................................. 25 2.2.2. Thio- and selenoborates of alkaline, alkaline earth, transition and post transition metals ......................................................................... 33 2.2.3. The RE thioborate Eu[B2S4]................................................ 45 II PREPARATIVE METHODS AND EXPERIMENTAL TECHNIQUES .......... 47 1. Starting materials and their characterization ............................... 49 2. Synthetic approaches and optimizations .................................... 51 2.1. High-temperature routes ...................................................... 52 2.2. Metathesis reactions ............................................................ 53 2.3. Spark Plasma Sintering (SPS) ............................................... 54 2.4. High-Pressure High-Temperature (Hp – HT) Syntheses ........... 55 3. Analytical methods and samples characterization ....................... 55 3.1. Powder X-ray diffraction ...................................................... 55 3.2. Crystal structure investigations using synchrotron radiation .... 57 3.3. Single crystal X-ray diffraction analysis .................................. 57 3.4. Metallographic investigations ................................................ 58 3.5. Electron microscopy ............................................................ 58 3.5.1. Scanning electron microscopy and energy dispersive X-ray spectroscopy ............................................................................ 58 3.5.2. Transmission electron microscopy ...................................... 59 3.6. Optical spectroscopy ........................................................... 59 3.6.1. Infra-Red spectroscopy .................................................... 59 3.6.2. Raman spectroscopy ........................................................ 60 3.7. X-ray absorption spectroscopy ............................................ 60 3.8. Thermal analysis ................................................................. 62 3.9. Magnetic susceptibility measurements ................................... 63 3.10. 11B NMR spectroscopy ..................................................... 63 3.11. Quantum chemical calculations ........................................... 64 3.11.1. Total energy calculations ................................................ 64 3.11.2. Charge transfer analysis ................................................ 64 3.11.3. Chemical bonding........................................................... 64 III RARE EARTH THIOBORATES ................................................. 67 1. Reinvestigation of the only reported rare earth thioborate – EuB2S4 ....69 2. RE[BS3] (RE = La – Nd, Sm, Gd, Tb) .................................... 69 2.1. Syntheses and phase analyses .......................................... 70 2.2. Crystal structure determinations ........................................ 74 2.3. X-ray absorption spectroscopy: EXAFS data analysis for Pr[BS3] ..... 79 2.4. Crystal chemistry .............................................................. 80 2.5. Optical spectroscopy ......................................................... 83 2.6. Thermal analysis ............................................................... 86 2.7. Magnetic susceptibility ....................................................... 88 2.8. X-ray absorption spectroscopy: XANES data analysis for Sm[BS3] .. 91 2.9. Crystal structure investigation at low temperature using synchrotron radiation ................................................................................... 91 2.10. Summary ......................................................................... 95 3. Gd[BS3] : Ce, Eu, Tb ............................................................. 97 3.1. Syntheses and phase analyses ............................................. 97 3.2. Crystal structure determinations ......................................... 101 3.3. Crystal chemistry .............................................................. 103 3.4. Optical spectroscopy ......................................................... 104 3.5. Thermal analysis ............................................................... 106 3.6. Summary ......................................................................... 107 4. RE9B5S21 (RE = Tb – Lu, Y) ................................................ 107 4.1. Syntheses and phase analyses ........................................... 108 4.2. Crystal structure determinations ........................................ 109 4.3. Crystal chemistry .............................................................. 112 4.4. Electronic structure, charge transfer and chemical bonding .... 115 4.5. X-ray absorption spectroscopy: EXAFS data analysis for Lu9B5S21 .............................................................................. 119 4.6. Thermal analysis ............................................................... 121 4.7. 11B NMR investigations ..................................................... 122 4.8. Optical spectroscopy ......................................................... 123 4.9. Summary ......................................................................... 126 IV ON THE WAY TO RARE EARTH SELENOBORATES .................... 127 1. Towards ternary phases in the systems RE–B–Se, with RE = Sm, Tb – Lu.......................................................................................... 129 2. The system La–B–Se ........................................................... 134 3. The system Gd–B–Se .......................................................... 136 4. The system Y–B–Se ............................................................ 137 5. Summary ........................................................................... 139 V SUMMARY AND OUTLOOK ..................................................... 141 VI APPENDIX .......................................................................... 149 VII REFERENCES .................................................................... 163 VIII LIST OF FIGURES ............................................................. 181 IX LIST OF TABLES ................................................................ 193 X CURRICULUM VITAE ........................................................... 199 XI VERSICHERUNG ............................................................... 203