Impact of hydrophilic side chains on the thin film transistor performance of a benzothieno-benzothiophene derivative

Side-chain engineering in molecular semiconductors provides a versatile toolbox for precisely manipulating the material's processability, crystallographic properties, as well as electronic and optoelectronic characteristics. This study explores the impact of integrating hydrophilic side chains, specifically oligoethylene glycol (OEG) units, into the molecular structure of the small molecule semiconductor, 2,7-bis(2(2-methoxy ethoxy)ethoxy) benzo[b]benzo[4,5] thieno[2,3-d] thiophene (OEG-BTBT). The investigation includes a comprehensive analysis of thin film morphology and crystallographic properties, along with the optimization of deposition parameters for improving the device performance. Despite the anticipated benefits, such as enhanced processability, our investigation into OEG-BTBT-based organic field-effect transistors (OFETs) reveals suboptimal performance marked by a low effective charge carrier mobility, a low on/off ratio, and a high threshold voltage. The study unveils bias stress effects and device degradation attributed to the high ionization energy of OEG-BTBT alongside the hydrophilic nature of the ethylene-glycol moieties, which lead to charge trapping at the dielectric interface. Our findings underscore the need for a meticulous balance between electronic properties and chemical functionalities in molecular semiconductors to achieve stable and efficient performance in organic electronic devices.This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 811284 (UHMob). Part of this work was undertaken using equipment facilities provided by the Henry Royce Institute, via the grant Henry Royce Institute, Cambridge Equipment: EP/P024947/1. Some of the work in Graz was funded by the Austrian Science Fund (FWF) [Grant-DOI: 10.55776/P33903-N]. Part of the computational results presented have been generated using the Vienna Scientific Cluster (VSC). The work in Mons has been funded by the Fund for Scientific Research (FRS) of FNRS within the Consortium des Equipements de Calcul Intensif (CECI) under grant 2.5020.11 and by the Walloon Region (ZENOBE Tier-1 supercomputer) under grant 1117545. J. C. is an FNRS research director. L. F. and M. M.-T. also acknowledge funds by MCIN/AEI/10.13039/501100011033/ERDF,UE with project SENSATION PID2022-141393OB-I00, and the “Severo Ochoa” Programme for Centers of Excellence in R&D (FUNFUTURECEX2019-000917-S).With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

Ab-initio investigations of the electronic structure of armchair graphene nanoribbons on the Au(111) surface

Armchair-Graphen-Nanob\ue4nder (AGNR) haben in den letzten Jahren erh\uf6hte Aufmerksamkeit erlangt, da es m\uf6glich wurde, sie \ufcber einen Bottom-up-Ansatz atomar pr\ue4zise herzustellen. Aufgrund ihrer anpassbaren Bandl\ufccke haben AGNRs das Potenzial, in opto-elektronischen Bauelementen eingesetzt zu werden und k\uf6nnten daher Silizium in bestimmten Anwendungen ersetzen. In Anbetracht dieser Aussichten ist es nicht verwunderlich, dass bereits viel Forschung betrieben wurde, um ihre elektronische Struktur zu verstehen. Allerdings gibt es immer noch eine L\ufccke im Verst\ue4ndnis, wie Oberfl\ue4chen ihre elektronische Struktur beeinflussen. Diese Arbeit versucht, diese L\ufccke zu schlie fen, indem sie den Einfluss einer Au(111)-Oberfl\ue4che auf die elektronische Struktur von 7-, 9- und 13-AGNR untersucht, also der AGNRs, die f\ufcr technische Anwendungen wahrscheinlich am relevantesten sind. Besonderes Augenmerk wird dabei auf die Simulation von winkelaufgel\uf6sten Photoemissionsspektroskopie (ARPES)-Experimenten gelegt. Die immer h\uf6here Aufl\uf6sung der ARPES erlaubt die direkte Messung der elektronischen Bandstruktur. Um die Ergebnisse von ARPES-Experimenten zu verstehen, sind deren Simulationen unerl\ue4sslich. Zus\ue4tzlich zu den ARPES-Simulationen wurden verschiedene andere Aspekte der AGNRs mit ab-initio-Simulationen untersucht. Dazu z\ue4hlen die elektronische Bandstruktur, die Zustandsdichte (DOS), die Bandl\ufccke, die Adsorptionsposition auf Au(111), die Adsorptionsh\uf6he und die Ladungsdichte. Um die ab-initio-Simulationen durchzuf\ufchren, wird in dieser Arbeit die Dichtefunktionaltheorie (DFT) verwendet. Mit Hilfe der Kohn-Sham-Orbitale aus der DFT-Simulation wurden die Photoemissionsintensit\ue4ten der ARPES-Experimente berechnet. Die ARPES-Simulationen stimmen gro fteils mit den Experimenten \ufcberein und best\ue4tigen damit die G\ufcltigkeit der verwendeten Methoden.Armchair graphene nanoribbons (AGNR) have gained increased attention in the recent years, because it became possible to produce them atomically precise via a bottom-up approach. Due to their tunable band gap, AGNRs have the potential to be used in opto-electronic devices and therefore could replace silicon in specific applications. Given these prospects, it is not surprising, that a fair amount of research has gone into understanding their electronic structure. However there is still a lack in understanding how surfaces affect their electronic structure.This work tries to fill this gap by investigating the effect of a Au(111) surface on the electronic structure of 7-, 9- and 13-AGNR, which are the AGNRs that are probably the most relevant for technical applications. Special focus is placed on the simulation of angle-resolved photoemission spectroscopy (ARPES) experiments. The ever increasing resolution of ARPES allows the direct measurement of the electronic band structure. In order to understand the results of ARPES experiments, simulations of it are essential. Additionally to the ARPES simulations, various other aspects of the AGNRs were investigated with ab-initio simulations. These include the electronic band structure, density of states (DOS), band gap, adsorption position on Au(111), adsorption height and charge density.To perform these ab-initio investigations, density functional theory (DFT) is employed in this work. Using the Kohn-Sham orbitals from the DFT simulation, the photoemission intensities of ARPES experiments were calculated. Simulated ARPES band and momentum maps of 7-AGNR/Au(111) are compared to multiple experiments. They consistently show good agreement, thereby confirming the validity of the used methods.Lukas ReichtZusammenfassungen auf Deutsch und EnglischMasterarbeit Karl-Franzens-Universit\ue4t Graz 2021 872

Designing Accurate Moment Tensor Potentials for Phonon-Related Properties of Crystalline Polymers

The phonon-related properties of crystalline polymers are highly relevant for various applications. Their simulation is, however, particularly challenging, as the systems that need to be modeled are often too extended to be treated by ab initio methods, while classical force fields are too inaccurate. Machine-learned potentials parametrized against material-specific ab initio data hold the promise of being extremely accurate and also highly efficient. Still, for their successful application, protocols for their parametrization need to be established to ensure an optimal performance, and the resulting potentials need to be thoroughly benchmarked. These tasks are tackled in the current manuscript, where we devise a protocol for parametrizing moment tensor potentials (MTPs) to describe the structural properties, phonon band structures, elastic constants, and forces in molecular dynamics simulations for three prototypical crystalline polymers: polyethylene (PE), polythiophene (PT), and poly-3-hexylthiophene (P3HT). For PE, the thermal conductivity and thermal expansion are also simulated and compared to experiments. A central element of the approach is to choose training data in view of the considered use case of the MTPs. This not only yields a massive speedup for complex calculations while essentially maintaining DFT accuracy, but also enables the reliable simulation of properties that, so far, have been entirely out of reach

Designing Accurate Moment Tensor Potentials for Phonon-Related Properties of Crystalline Polymers

The phonon-related properties of crystalline polymers are highly relevant for various applications. Their simulation is, however, particularly challenging, as the systems that need to be modeled are often too extended to be treated by ab initio methods, while classical force fields are too inaccurate. Machine-learned potentials parametrized against material-specific ab initio data hold the promise of being extremely accurate and also highly efficient. Still, for their successful application, protocols for their parametrization need to be established to ensure an optimal performance, and the resulting potentials need to be thoroughly benchmarked. These tasks are tackled in the current manuscript, where we devise a protocol for parametrizing moment tensor potentials (MTPs) to describe the structural properties, phonon band structures, elastic constants, and forces in molecular dynamics simulations for three prototypical crystalline polymers: polyethylene (PE), polythiophene (PT), and poly-3-hexylthiophene (P3HT). For PE, the thermal conductivity and thermal expansion are also simulated and compared to experiments. A central element of the approach is to choose training data in view of the considered use case of the MTPs. This not only yields a massive speedup for complex calculations while essentially maintaining DFT accuracy, but also enables the reliable simulation of properties that, so far, have been entirely out of reach

Anisotropic Phonon Bands in H‑Bonded Molecular Crystals: The Instructive Case of α‑Quinacridone

Phonons play a crucial role in the thermodynamic and transport properties of solid materials. Nevertheless, rather little is known about phonons in organic semiconductors. Thus, we employ highly reliable quantum mechanical calculations for studying the phonons in the α-polymorph of quinacridone. This material is particularly interesting, as it has highly anisotropic properties with distinctly different bonding types (H-bonding, π-stacking, and dispersion interactions) in different spatial directions. By calculating the overlaps of modes in molecular quinacridone and the α-polymorph, we associate Γ-point phonons with molecular vibrations to get a first impression of the impact of the crystalline environment. The situation becomes considerably more complex when analyzing phonons in the entire 1st Brillouin zone, where, due to the low symmetry of α-quinacridone, a multitude of avoided band crossings occur. At these, the character of the phonon modes typically switches, as can be inferred from mode participation ratios and mode longitudinalities. Notably, avoided crossings are observed not only as a function of the length but also as a function of the direction of the phonon wave vector. Analyzing these avoided crossings reveals how it is possible that the highest frequency acoustic band is always the one with the largest longitudinality, although longitudinal phonons in different crystalline directions are characterized by fundamentally different molecular displacements. The multiple avoided crossings also give rise to a particularly complex angular dependence of the group velocities, but combining the insights from the various studied quantities still allows drawing general conclusions, e.g., on the relative energetics of longitudinal vs transverse deformations (i.e., compressions and expansions vs slips of neighboring molecules). They also reveal how phonon transport in α-quinacridone is impacted by the reinforcing H-bonds and by π-stacking interactions (resulting from a complex superposition of van der Waals, charge penetration, and exchange repulsion)

Anisotropic Phonon Bands in H‑Bonded Molecular Crystals: The Instructive Case of α‑Quinacridone

Phonons play a crucial role in the thermodynamic and transport properties of solid materials. Nevertheless, rather little is known about phonons in organic semiconductors. Thus, we employ highly reliable quantum mechanical calculations for studying the phonons in the α-polymorph of quinacridone. This material is particularly interesting, as it has highly anisotropic properties with distinctly different bonding types (H-bonding, π-stacking, and dispersion interactions) in different spatial directions. By calculating the overlaps of modes in molecular quinacridone and the α-polymorph, we associate Γ-point phonons with molecular vibrations to get a first impression of the impact of the crystalline environment. The situation becomes considerably more complex when analyzing phonons in the entire 1st Brillouin zone, where, due to the low symmetry of α-quinacridone, a multitude of avoided band crossings occur. At these, the character of the phonon modes typically switches, as can be inferred from mode participation ratios and mode longitudinalities. Notably, avoided crossings are observed not only as a function of the length but also as a function of the direction of the phonon wave vector. Analyzing these avoided crossings reveals how it is possible that the highest frequency acoustic band is always the one with the largest longitudinality, although longitudinal phonons in different crystalline directions are characterized by fundamentally different molecular displacements. The multiple avoided crossings also give rise to a particularly complex angular dependence of the group velocities, but combining the insights from the various studied quantities still allows drawing general conclusions, e.g., on the relative energetics of longitudinal vs transverse deformations (i.e., compressions and expansions vs slips of neighboring molecules). They also reveal how phonon transport in α-quinacridone is impacted by the reinforcing H-bonds and by π-stacking interactions (resulting from a complex superposition of van der Waals, charge penetration, and exchange repulsion)

Infliximab Reduces Endoscopic, but Not Clinical, Recurrence of Crohn's Disease After Ileocolonic Resection.

BACKGROUND & AIMS: Most patients with Crohn's disease (CD) eventually require an intestinal resection. However, CD frequently recurs after resection. We performed a randomized trial to compare the ability of infliximab vs placebo to prevent CD recurrence. METHODS: We evaluated the efficacy of infliximab in preventing postoperative recurrence of CD in 297 patients at 104 sites worldwide from November 2010 through May 2012. All study patients had undergone ileocolonic resection within 45 days before randomization. Patients were randomly assigned (1:1) to groups given infliximab (5 mg/kg) or placebo every 8 weeks for 200 weeks. The primary end point was clinical recurrence, defined as a composite outcome consisting of a CD Activity Index score >200 and a >/=70-point increase from baseline, and endoscopic recurrence (Rutgeerts score >/=i2, determined by a central reader) or development of a new or re-draining fistula or abscess, before or at week 76. Endoscopic recurrence was a major secondary end point. RESULTS: A smaller proportion of patients in the infliximab group had a clinical recurrence before or at week 76 compared with the placebo group, but this difference was not statistically significant (12.9% vs 20.0%; absolute risk reduction [ARR] with infliximab, 7.1%; 95% confidence interval: -1.3% to 15.5%; P = .097). A significantly smaller proportion of patients in the infliximab group had endoscopic recurrence compared with the placebo group (30.6% vs 60.0%; ARR with infliximab, 29.4%; 95% confidence interval: 18.6% to 40.2%; P /=i2 (22.4% vs 51.3%; ARR with infliximab, 28.9%; 95% confidence interval: 18.4% to 39.4%; P < .001). Patients previously treated with anti-tumor necrosis factor agents or those with more than 1 resection were at greater risk for clinical recurrence. The safety profile of infliximab was similar to that from previous reports. CONCLUSIONS: Infliximab is not superior to placebo in preventing clinical recurrence after CD-related resection. However, infliximab does reduce endoscopic recurrence. ClinicalTrials.gov ID NCT01190839

Impact of hydrophilic side chains on the thin film transistor performance of a benzothieno–benzothiophene derivative

Side-chain engineering in molecular semiconductors provides a versatile toolbox for precisely manipulating the material's processability, crystallographic properties, as well as electronic and optoelectronic characteristics.</jats:p

Impact of Hydrophilic Side Chains on the Thin Film Transistor Performance of a Benzothieno-Benzothiophene Derivative

Side-chain engineering in molecular semiconductors provides a versatile toolbox for precisely manipulating the material’s processability, crystallographic properties, as well as electronic and optoelectronic characteristics. This study explores the impact of integrating hydrophilic side chains, specifically oligoethylene glycol (OEG) units, into the molecular structure of the small molecule semiconductor, 2,7-bis(2(2-methoxy ethoxy)ethoxy) benzo[b]benzo[4,5] thieno[2,3-d] thiophene (OEG-BTBT). The investigation includes a comprehensive analysis of thin film morphology and crystallographic properties, along with the optimization of deposition parameters for improving the device performance. Despite the anticipated benefits, such as enhanced processability, our investigation into OEG-BTBT-based organic field-effect transistors (OFETs) reveals suboptimal performance marked by a low effective charge carrier mobility, a low on/off ratio, and a high threshold voltage. The study unveils bias stress effects and device degradation attributed to the high ionization energy of OEG-BTBT alongside the hydrophilic nature of the ethylene-glycol moieties, which lead to charge trapping at the dielectric interface. Our findings underscore the need for a meticulous balance between electronic properties and chemical functionalities in molecular semiconductors to achieve stable and efficient performance in organic electronic devices