@phdthesis{HechtgebWagener2019,
  author    = {Hecht [geb. Wagener], Reinhard Johannes},
  title     = {Processing and Characterization of Bulk Heterojunction Solar Cells Based on New Organic n-Type Semiconductors},
  doi       = {10.25972/OPUS-16138},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-161385},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2019},
  abstract  = {This thesis established the fabrication of organic solar cells of DA dye donors and fullerene acceptors under ambient conditions in our laboratory, however, with reduced power conversion efficiencies compared to inert conditions. It was shown that moisture had the strongest impact on the stability and reproducibility of the solar cells. Therefore, utilization of robust materials, inverted device architectures and fast fabrication/characterization are recommended if processing takes place in air. Furthermore, the dyad concept was successfully explored in merocyanine dye-fullerene dyads and power conversion efficiencies of up to 1.14 \% and 1.59 \% were measured under ambient and inert conditions, respectively. It was determined that the major drawback in comparison to comparable BHJ devices was the inability of the dyad molecules to undergo phase separation. Finally, two series of small molecules were designed in order to obtain electron transport materials, using the acceptor-core-acceptor motive. By variation of the acceptor units especially the LUMO levels could be lowered effectively. Investigation of the compounds in organic thin film transistors helped to identify promising molecules with electron transport properties. Electron transport mobilities of up to 7.3 × 10-2 cm2 V-1 s-1 (ADA2b) and 1.39 × 10-2 cm2 V-1 s-1 (AπA1b) were measured in air for the ADA and AπA dyes, respectively. Investigation of selected molecules in organic solar cells proved that these molecules work as active layer components, even though power conversion efficiencies cannot compete with fullerene based devices yet. Thus, this thesis shows new possibilities that might help to develop and design small molecules as substitutes for fullerene acceptors.},
  subject      = {Heterosolarzelle},
  language  = {en}
}
@phdthesis{Muzha2022,
  author    = {Muzha, Andreas},
  title     = {Herstellung und Charakterisierung kolloidaler L{\"o}sungen diamantbasierter und verwandter Materialien},
  doi       = {10.25972/OPUS-29668},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-296685},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {In der vorliegenden Publikation wurden stabile kolloidale L{\"o}sungen aus CVD-Diamant, Detonationsdiamant sowie artverwandten Materialien hergestellt und charakterisiert Besonderes Augenmerk wurde bei der Zerkleinerung von CVD Diamant daraufgelegt, dass die nanoskaligen Partikel ihre materialspezifischen Eigenschaften auch bei Reduktion der Gr{\"o}ße beibehalten. Systematisch wurde die Zerkleinerung in einer Planetenm{\"u}hle analysiert. Es wurde sowohl die minimal erreichbare Partikelgr{\"o}ße, als auch die Menge an erzeugtem, nanoskaligem Material bewertet. Um die Vermahlung zu verbessern, wurden die Geschwindigkeit der M{\"u}hle, die Gr{\"o}ße der Mahlk{\"o}rper, die Dauer der Vermahlung, sowie die eingesetzten L{\"o}semittel variiert. Des Weiteren konnten durch die Vermahlung unterschiedlich hergestellter CVD Diamantfilme in einer Vibrationsm{\"u}hle die Einfl{\"u}sse von Schichtdicke und Korngr{\"o}ße der Diamantkristalle untersucht werden. Durch Bearbeitung von Detonationsdiamanten und Kohlenstoffnanozwiebeln wurden stabile kolloidale L{\"o}sungen hergestellt, mit Partikelgr{\"o}ßen im unteren Nanometerbereich. Diese sind im alkalischen pH-Bereich stabil sein, hierf{\"u}r wurde durch Luft und S{\"a}ureoxidation oxidierter Detonationsdiamant und oxidierte Kohlenstoffnanozwiebeln hergestellt. Mithilfe der thermogravimetrischen Analyse und Infrarotspektroskopie wurde die hierf{\"u}r optimale Temperatur und Dauer bestimmt.},
  subject      = {Diamant},
  language  = {de}
}
@phdthesis{GamachegebRupp2021,
  author    = {Gamache [geb. Rupp], Mira Theresa},
  title     = {Ligand Design for Ru(II) Photosensitizers in Photocatalytic Hydrogen Evolution},
  doi       = {10.25972/OPUS-24676},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-246766},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {This thesis investigates different ligand designs for Ru(II) complexes and the activity of the complexes as photosensitizer (PS) in photocatalytic hydrogen evolution. The catalytic system typically contains a catalyst, a sacrificial electron donor (SED) and a PS, which needs to exhibit strong absorption and luminescence, as well as reversible redox behavior. Electron-withdrawing pyridine substituents on the terpyridine metal ion receptor result in an increase of excited-state lifetime and quantum yield (Φ = 74*10-5; τ = 3.8 ns) and lead to complex III-C1 exhibiting activity as PS. While the turn-over frequency (TOFmax) and turn-over number (TON) are relatively low (TOFmax = 57 mmolH2 molPS-1 min-1; TON(44 h) = 134 mmolH2 molPS-1), the catalytic system is long-lived, losing only 20\% of its activity over the course of 12 days. Interestingly, the heteroleptic design in III-C1 proves to be beneficial for the performance as PS, despite III-C1 having comparable photophysical and electrochemical properties as the homoleptic complex IV-C2 (TOFmax = 35 mmolH2 molPS-1 min-1; TON(24 h) = 14 mmolH2 molPS-1). Reductive quenching of the excited PS by the SED is identified as rate-limiting step in both cases. Hence, the ligands are designed to be more electron-accepting either via N-methylation of the peripheral pyridine substituents or introduction of a pyrimidine ring in the metal ion receptor, leading to increased excited-state lifetimes (τ = 9-40 ns) and luminescence quantum yields (Φ = 40-400*10-5). However, the more electron-accepting character of the ligands also results in anodically shifted reduction potentials, leading to a lack of driving force for the electron transfer from the reduced PS to the catalyst. Hence, this electron transfer step is found to be a limiting factor to the overall performance of the PS. While higher TOFmax in hydrogen evolution experiments are observed for pyrimidine-containing PS (TOFmax = 300-715 mmolH2 molPS-1 min-1), the longevity for these systems is reduced with half-life times of 2-6 h. Expansion of the pyrimidine-containing ligands to dinuclear complexes yields a stronger absorptivity (ε = 100-135*103 L mol-1 cm-1), increased luminescence (τ = 90-125 ns, Φ = 210-350*10-5) and can also result in higher TOFmax given sufficient driving force for electron transfer to the catalyst (TOFmax = 1500 mmolH2 molPS-1 min-1). When comparing complexes with similar driving forces, stronger luminescence is reflected in a higher TOFmax. Besides thermodynamic considerations, kinetic effects and electron transfer efficiency are assumed to impact the observed activity in hydrogen evolution. In summary, this work shows that targeted ligand design can make the previously disregarded group of Ru(II) complexes with tridentate ligands attractive candidates for use as PS in photocatalytic hydrogen evolution.},
  subject      = {Fotokatalyse},
  language  = {en}
}
@phdthesis{Roos2021,
  author    = {Roos, Markus},
  title     = {Synthesis, Photophysics and Photocatalysis of [FeFe] Complex Containing Dyads and Bimolecular Systems},
  doi       = {10.25972/OPUS-23453},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-234537},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {In the course of this work, a total of three photocatalytically active dyads for proton reduction could be synthesized together with the associated individual components. Two of them, D1 and D2, comprised a [Ru(bpy)3]2+ photosensitizer and D3 an [Ir(ppy)2bpy]+ photosensitizer. A Ppyr3-substituted propyldithiolate [FeFe] complex was used as catalyst in all systems. The absorption spectroscopic and electrochemical investigations showed that an inner-dyadic electronic coupling is effectively prevented in the dyads due to conjugation blockers within the bridging units used. The photocatalytic investigations exhibited that all dyad containing two-component systems (2CS) showed a significantly worse performance than the corresponding bimolecular three-component systems (3CS). Transient absorption spectroscopy showed that the 2CS behave very similarly to the associated multicomponent systems during photocatalysis. The electron that was intended for the intramolecular transfer from the photosensitizer unit to the catalyst unit within the dyads remains at the photosensitizer for a relatively long time, analogous to the 3CS and despite the covalently bound catalyst. It is therefore assumed that this intramolecular electron transfer is likely to be hindered as a result of the weak electronic coupling caused by the bridge units used. Instead, the system bypasses this through an intermolecular transfer to other dyad molecules in the immediate vicinity. In addition, with the help of emission quenching experiments and electrochemical investigations, it could be clearly concluded that all investigated systems proceed via the reductive quenching mechanism during photocatalysis.},
  subject      = {Fotokatalyse},
  language  = {en}
}
@phdthesis{Rang2023,
  author    = {Rang, Maximilian},
  title     = {Metall{\"a}hnliche Reaktivit{\"a}t \(in\) \(situ\) erzeugter Borylene},
  doi       = {10.25972/OPUS-24046},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240465},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Einfach Lewis-Basen stabilisierte Borylene wurden durch Reduktion in situ hergestellt und in Gegenwart von Kohlenstoffmonoxid oder Distickstoff umgesetzt. Die entstandenen Verbindungen wurden mittels NMR-, ESR-, UV/Vis- und IR-Spektroskopie sowie Einkristallr{\"o}ntgenstrukturanalyse charakterisiert. Im Zuge dessen konnten f{\"u}r die erhaltenen Spezies Eigenschaften ermittelt werden, die denen analoger {\"U}bergangsmetallkomplexe {\"a}hneln. Ferner konnten die zugrundeliegenden mechanistischen Vorg{\"a}nge der Reaktionen durch gezielte Variation der Reaktionsparameter aufgekl{\"a}rt werden. Zudem wurden Redoxverhalten und Reaktivit{\"a}ten der isolierten Produkte in weiterf{\"u}hrenden Studien n{\"a}her untersucht.},
  subject      = {Bor},
  language  = {de}
}