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- ItemSemitransparent Perovskite Solar Cells with an Evaporated Ultra-Thin Perovskite Absorber(Weinheim : Wiley-VCH, 2023) Zhang, Zongbao; Ji, Ran; Jia, Xiangkun; Wang, Shu‐Jen; Deconinck, Marielle; Siliavka, Elena; Vaynzof, YanaMetal halide perovskites are of great interest for application in semitransparent solar cells due to their tunable bandgap and high performance. However, fabricating high-efficiency perovskite semitransparent devices with high average visible transmittance (AVT) is challenging because of their high absorption coefficient. Here, a co-evaporation process is adopted to fabricate ultra-thin CsPbI3 perovskite films. The smooth surface and orientated crystal growth of the evaporated perovskite films make it possible to achieve 10 nm thin films with compact and continuous morphology without pinholes. When integrated into a p-i-n device structure of glass/ITO/PTAA/perovskite/PCBM/BCP/Al/Ag with an optimized transparent electrode, these ultra-thin layers result in an impressive open-circuit voltage (VOC) of 1.08 V and a fill factor (FF) of 80%. Consequently, a power conversion efficiency (PCE) of 3.6% with an AVT above 50% is demonstrated, which is the first report for a perovskite device of a 10 nm active layer thickness with high VOC, FF and AVT. These findings demonstrate that deposition by thermal evaporation makes it possible to form compact ultra-thin perovskite films, which are of great interest for future smart windows, light-emitting diodes, and tandem device applications.
- ItemA Highly Active Cobalt Catalyst for the General and Selective Hydrogenation of Aromatic Heterocycles(Weinheim : Wiley-VCH, 2023) Bauer, Christof; Müller, Felix; Keskin, Sercan; Zobel, Mirijam; Kempe, RhettNanostructured earth abundant metal catalysts that mediate important chemical reactions with high efficiency and selectivity are of great interest. This study introduces a synthesis protocol for nanostructured earth abundant metal catalysts. Three components, an inexpensive metal precursor, an easy to synthesize N/C precursor, and a porous support material undergo pyrolysis to give the catalyst material in a simple, single synthesis step. By applying this catalyst synthesis, a highly active cobalt catalyst for the general and selective hydrogenation of aromatic heterocycles could be generated. The reaction is important with regard to organic synthesis and hydrogen storage. The mild reaction conditions observed for quinolines permit the selective hydrogenation of numerous classes of N-, O- and S-heterocyclic compounds such as: quinoxalines, pyridines, pyrroles, indoles, isoquinoline, aciridine amine, phenanthroline, benzofuranes, and benzothiophenes.
- ItemOn the Preparation and Spectroelectrochemical Characterization of Certain 2,5-Bis(het)aryl Substituted Thiophenes(Weinheim : Wiley-VCH, 2024) Dmitrieva, Evgenia; Barche, Jens; Popov, Alexey A.; Hartmann, HorstIn this work, a series of novel 2,5-bis(het)aryl and 2,5-bis-thienyl substituted thiophenes have been synthesized and characterized by ultraviolet-visible-near infrared (UV-Vis-NIR) absorption and fluorescence spectroscopy as well as cyclic voltammetry. From the electron paramagnetic resonance (EPR)/UV-Vis-NIR spectroelectrochemical data, information about the optical and magnetic properties of the charged species of these compounds have been provided. The spin distributions in the electrochemically generated radical ions were estimated experimentally and compared with theoretical data.
- ItemGelation Kinetics and Mechanical Properties of Thiol-Tetrazole Methylsulfone Hydrogels Designed for Cell Encapsulation(Weinheim : Wiley-VCH, 2022) de Miguel‐Jiménez, Adrián; Ebeling, Bastian; Paez, Julieta I.; Fink‐Straube, Claudia; Pearson, Samuel; del Campo, AránzazuHydrogel precursors that crosslink within minutes are essential for the development of cell encapsulation matrices and their implementation in automated systems. Such timescales allow sufficient mixing of cells and hydrogel precursors under low shear forces and the achievement of homogeneous networks and cell distributions in the 3D cell culture. The previous work showed that the thiol-tetrazole methylsulfone (TzMS) reaction crosslinks star-poly(ethylene glycol) (PEG) hydrogels within minutes at around physiological pH and can be accelerated or slowed down with small pH changes. The resulting hydrogels are cytocompatible and stable in cell culture conditions. Here, the gelation kinetics and mechanical properties of PEG-based hydrogels formed by thiol-TzMS crosslinking as a function of buffer, crosslinker structure and degree of TzMS functionality are reported. Crosslinkers of different architecture, length and chemical nature (PEG versus peptide) are tested, and degree of TzMS functionality is modified by inclusion of RGD cell-adhesive ligand, all at concentration ranges typically used in cell culture. These studies corroborate that thiol/PEG-4TzMS hydrogels show gelation times and stiffnesses that are suitable for 3D cell encapsulation and tunable through changes in hydrogel composition. The results of this study guide formulation of encapsulating hydrogels for manual and automated 3D cell culture.
- ItemCrystalline Carbosilane-Based Block Copolymers: Synthesis by Anionic Polymerization and Morphology Evaluation in the Bulk State(Weinheim : Wiley-VCH, 2022) Hübner, Hanna; Niebuur, Bart‐Jan; Janka, Oliver; Gemmer, Lea; Koch, Marcus; Kraus, Tobias; Kickelbick, Guido; Stühn, Bernd; Gallei, MarkusBlock copolymers (BCPs) in the bulk state are known to self-assemble into different morphologies depending on their polymer segment ratio. For polymers with amorphous and crystalline BCP segments, the crystallization process can be influenced significantly by the corresponding bulk morphology. Herein, the synthesis of the amorphous-crystalline BCP poly(dimethyl silacyclobutane)-block-poly(2vinyl pyridine), (PDMSB-b-P2VP), by living anionic polymerization is reported. Polymers with overall molar masses ranging from 17 400 g to 592 200 g mol−1 and PDMSB contents of 4.8–83.9 vol% are synthesized and characterized by size-exclusion chromatography and NMR spectroscopy. The bulk morphology of the obtained polymers is investigated by means of transmission electron microscopy and small angle X-ray scattering, revealing a plethora of self-assembled structures, providing confined and nonconfined conditions. Subsequently, the influence of the previously determined morphologies and their resulting confinement on the crystallinity and crystallization behavior of PDMSB is analyzed via differential scanning calorimetry and powder X-ray diffraction. Here, fractionated crystallization and supercooling effects are observable as well as different diffraction patterns of the PDMSB crystallites for confined and nonconfined domains.
- ItemCobalt-based Co3Mo3N/Co4N/Co Metallic Heterostructure as a Highly Active Electrocatalyst for Alkaline Overall Water Splitting(Weinheim : Wiley-VCH, 2024) Liu, Yuanwu; Wang, Lirong; Hübner, René; Kresse, Johannes; Zhang, Xiaoming; Deconinick, Marielle; Vaynzof, Yana; Weidinger, Inez M.; Eychmüller, AlexanderAlkaline water electrolysis holds promise for large-scale hydrogen production, yet it encounters challenges like high voltage and limited stability at higher current densities, primarily due to inefficient electron transport kinetics. Herein, a novel cobalt-based metallic heterostructure (Co3Mo3N/Co4N/Co) is designed for excellent water electrolysis. In operando Raman experiments reveal that the formation of the Co3Mo3N/Co4N heterointerface boosts the free water adsorption and dissociation, increasing the available protons for subsequent hydrogen production. Furthermore, the altered electronic structure of the Co3Mo3N/Co4N heterointerface optimizes ΔGH of the nitrogen atoms at the interface. This synergistic effect between interfacial nitrogen atoms and metal phase cobalt creates highly efficient active sites for the hydrogen evolution reaction (HER), thereby enhancing the overall HER performance. Additionally, the heterostructure exhibits a rapid OH− adsorption rate, coupled with great adsorption strength, leading to improved oxygen evolution reaction (OER) performance. Crucially, the metallic heterojunction accelerates electron transport, expediting the afore-mentioned reaction steps and enhancing water splitting efficiency. The Co3Mo3N/Co4N/Co electrocatalyst in the water electrolyzer delivers excellent performance, with a low 1.58 V cell voltage at 10 mA cm−2, and maintains 100 % retention over 100 hours at 200 mA cm−2, surpassing the Pt/C RuO2 electrolyzer
- ItemBifunctional Carbanionic Synthesis of Fully Bio-Based Triblock Structures Derived from β-Farnesene and ll-Dilactide: Thermoplastic Elastomers(Weinheim : Wiley-VCH, 2023) Meier‐Merziger, Moritz; Imschweiler, Jan; Hartmann, Frank; Niebuur, Bart‐Jan; Kraus, Tobias; Gallei, Markus; Frey, HolgerCurrent environmental challenges and the shrinking fossil-fuel feedstock are important criteria for the next generation of polymer materials. In this context, we present a fully bio-based material, which shows promise as a thermoplastic elastomer (TPE). Due to the use of β-farnesene and L-lactide as monomers, bio-based feedstocks, namely sugar cane and corn, can be used. A bifunctional initiator for the carbanionic polymerization was employed, to permit an efficient synthesis of ABA-type block structures. In addition, the “green” solvent MTBE (methyl tert-butyl ether) was used for the anionic polymerisation, enabling excellent solubility of the bifunctional anionic initiator. This afforded low dispersity (Đ=1.07 to 1.10) and telechelic polyfarnesene macroinitiators. These were employed for lactide polymerization to obtain H-shaped triblock copolymers. TEM and SAXS revealed clearly phase-separated morphologies, and tensile tests demonstrated elastic mechanical properties. The materials featured two glass transition temperatures, at - 66 °C and 51 °C as well as gyroid or cylindrical morphologies, resulting in soft elastic materials at room temperature.
- ItemUnraveling the Electrochemical Mechanism in Tin Oxide/MXene Nanocomposites as Highly Reversible Negative Electrodes for Lithium-Ion Batteries(Weinheim : Wiley-VCH, 2023) Gentile, Antonio; Arnold, Stefanie; Ferrara, Chiara; Marchionna, Stefano; Tang, Yushu; Maibach, Julia; Kübel, Christian; Presser, Volker; Ruffo, RiccardoLithium-ion batteries are constantly developing as the demands for power and energy storage increase. One promising approach to designing high-performance lithium-ion batteries is using conversion/alloying materials, such as SnO2. This class of materials does, in fact, present excellent performance and ease of preparation; however, it suffers from mechanical instabilities during cycling that impair its use. One way to overcome these problems is to prepare composites with bi-dimensional materials that stabilize them. Thus, over the past 10 years, two-dimensional materials with excellent transport properties (graphene, MXenes) have been developed that can be used synergistically with conversion materials to exploit both advantages. In this work, a 50/50 (by mass) SnO2/Ti3C2Tz nanocomposite is prepared and optimized as a negative electrode for lithium-ion batteries. The nanocomposite delivers over 500 mAh g−1 for 700 cycles at 0.1 A g−1 and demonstrates excellent rate capability, with 340 mAh g−1 at 8 A g−1. These results are due to the synergistic behavior of the two components of the nanocomposite, as demonstrated by ex situ chemical, structural, and morphological analyses. This knowledge allows, for the first time, to formulate a reaction mechanism with lithium-ions that provides partial reversibility of the conversion reaction with the formation of SnO.
- ItemCorrelation of Work Function and Conformation of C80 Endofullerenes on h-BN/Ni(111)(Weinheim : Wiley-VCH, 2024) Stania, Roland; Seitsonen, Ari Paavo; Jung, Hyunjin; Kunhardt, David; Popov, Alexey A.; Muntwiler, Matthias; Greber, ThomasChange of conformation or polarization of molecules is an expression of their functionality. If the two correlate, electric fields can change the conformation. In the case of endofullerene single-molecule magnets the conformation is linked to an electric and a magnetic dipole moment, and therefore magnetoelectric effects are envisoned. The interface system of one monolayer Sc2TbN@C80 on hexagonal boron nitride (h-BN) on Ni(111) has been studied. The molecular layer is hexagonally close packedbut incommensurate. With photoemission the polarization and the conformation of the molecules are addressed by the work function and angular intensity distributions. Valence band photoemission (ARPES) shows a temperature-induced energy shift of the C80 molecular orbitals that is parallel to a change in work function of 0.25 eV without charging the molecules. ARPES indicates a modification in molecular conformations between 30 and 300 K. This order–disorder transition involves a polarization change in the interface and is centered at 125 K as observed with high-resolution X-ray photoelectron spectroscopy (XPS). The temperature dependence is described with a thermodynamic model that accounts for disordering with an excitation energy of 74 meV into a high entropy ensemble. All experimental results are supported by density functional theory (DFT).
- ItemAnalysis of the Annealing Budget of Metal Oxide Thin-Film Transistors Prepared by an Aqueous Blade-Coating Process(Weinheim : Wiley-VCH, 2022) Tang, Tianyu; Dacha, Preetam; Haase, Katherina; Kreß, Joshua; Hänisch, Christian; Perez, Jonathan; Krupskaya, Yulia; Tahn, Alexander; Pohl, Darius; Schneider, Sebastian; Talnack, Felix; Hambsch, Mike; Reineke, Sebastian; Vaynzof, Yana; Mannsfeld, Stefan C. B.Metal oxide (MO) semiconductors are widely used in electronic devices due to their high optical transmittance and promising electrical performance. This work describes the advancement toward an eco-friendly, streamlined method for preparing thin-film transistors (TFTs) via a pure water-solution blade-coating process with focus on a low thermal budget. Low temperature and rapid annealing of triple-coated indium oxide thin-film transistors (3C-TFTs) and indium oxide/zinc oxide/indium oxide thin-film transistors (IZI-TFTs) on a 300 nm SiO2 gate dielectric at 300 °C for only 60 s yields devices with an average field effect mobility of 10.7 and 13.8 cm2 V−1 s−1, respectively. The devices show an excellent on/off ratio (>106), and a threshold voltage close to 0 V when measured in air. Flexible MO-TFTs on polyimide substrates with AlOx dielectrics fabricated by rapid annealing treatment can achieve a remarkable mobility of over 10 cm2 V−1 s−1 at low operating voltage. When using a longer post-coating annealing period of 20 min, high-performance 3C-TFTs (over 18 cm2 V−1 s−1) and IZI-TFTs (over 38 cm2 V−1 s−1) using MO semiconductor layers annealed at 300 °C are achieved.