The influence of dipolar doping on charge injection and transport in small molecular organic semiconductors

The present work investigates the effect of dipolar doping on charge injection and charge carrier dynamics in organic semiconducting thin films. In this context, the term dipolar doping refers to the dilution or doping of a non-polar matrix molecule with a polar guest. For this purpose, the hole-conductors N,N ’-Di(1-naphthyl)-N,N ’-diphenyl-(1,1’-biphenyl)-4,4’-diamine (NPB) and 4,4-N,N ’-Dicarbazole-1,1’-biphenyl (CBP) will serve as the host molecules. Dopants include Tris-(8-hydroxyquinoline)aluminum (Alq3) and OXD-7 (1,3-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl]benzene. The main focus, however, is on the system NPB:Alq3, which has also been studied extensively in the past [1–3]. In general, doping of (organic) semiconductors is a well known concept to tune conductivity [4] or optimize emitting properties of OLEDs [5]. The specific effect of doping with polar species, however, was not thoroughly investigated so far, although many guest molecules are indeed polar [6]. Because organic molecules are extended objects, their orientation with respect to the substrate surface [7], other molecules in the film [8] or e.g. the direction of light output from OLEDs [9] plays a crucial role in device performance. The key figure of polar molecules in this regard is their permanent dipole moment, arising from the non-uniform charge distribution on the molecule. If this dipole moment does not orient perfectly isotropic, it will lead to the build-up of a giant surface potential (GSP) and thus to a macroscopic dielectric polarization of the organic film. Despite this being a known fact [1, 7, 10], the implications of such high potentials on charge transport and injection within and into an organic layer stack have only been studied recently [3, 7, 11]. Dipolar doping now allows to introduce and tune the GSP in a former unpolar organic material [2]. The concentration dependence of the magnitude of the GSP in dipolar doped systems is the first major part of this work. Additionally, dipolar doping can be utilized to create hole conducting films that exhibit a GSP, which allow to study the impact of film polarization also in the hole conducting layer (HTL) of an OLED. In neat film, a GSP was previously seen mostly for electron conductors [6, 12]. Therefor, the prototypical, hole conducting mixture NPB:Alq3 is investigated at different doping concentrations and with varied substrate material with respect to hole injection and charge transport. The mixtures are studied in single-layer, monopolar devices with only the HTL present, as well as bilayer OLEDs with Alq 3 -doped NPB as HTL and neat Alq3 as electron transport layer, respectively. The latter are treated as metal insulator semiconductor (MIS) structures following and applying our recently developed method of charge extraction by linearly increasing voltage (CELIV) on polar OLEDs [13,14]. Furthermore, ultraviolet photoelectron spectroscopy allows to compare the electrical observations with the energy alignment between contact and doped NPB. For all device types, an optimum in device performance and carrier injection for moderate doping concentrations of about 5% is found. By comparing all different methods with a focus on charge injection barriers, a complex relationship of carrier transport, substrate workfunction, modified injection and the effect of polarization is found. This effectively manipulates charge carrier injection across the metal-organic interface and charge transport in the device.Die vorliegende Arbeit befasst sich mit den Auswirkungen von polarer Dotierung auf Ladungsträgertransport und -injektion in organischen Halbleitern. „Polare Dotierung“ bezieht sich hierbei auf das Verdünnen oder Dotieren einer unpolaren Matrix aus organischen Molekülen mittels polaren Gast-Molekülen. Für diesen Zweck dienen die organischen Lochleiter N,N ’-Di(1-Naphthyl)-N,N ’-Diphenyl-(1,1’-Biphenyl)-4,4’-Diamin (NPB) und 4,4-N,N ’-Dicarbazole-1,1’-Biphenyl (CBP) als Matrix. Dotiert werden sie mit Tris-(8-Hydroxyquinolin) Aluminium (Alq3) und 1,3-bis[2-(4-tert- butylphenyl)-1,3,4-oxadiazo-5-yl]Benzen (OXD-7). Der Fokus dieser Arbeit liegt allerdings auf dem System NPB:Alq3, welches auch vorher bereits gründlich untersucht wurde [1–3]. Im Allgemeinen ist die Dotierung von (organischen) Halbleitern eine etablierte, zentrale Methode zur Optimierung der Leitfähigkeit [4] oder der Emittereigenschaften von organischen Leuchtdioden [5]. Die Folgen einer Dotierung mit polaren Molekülen im Speziellen wurde allerdings bisher noch nicht systematisch untersucht, obwohl viele häufig verwendete Dotanden durchaus polare Moleküle sind [6]. Organische Moleküle sind ausgedehnte Objekte mit komplexen Formen, deren Orientierung zur Substratoberfläche [7], zu anderen Molekülen in der Schicht [8] oder auch zum Emissionsvektor einer OLED [9] einen großen Einfluss auf die Effizienz des Bauteils hat. Die wichtigste Eigenschaft von polaren Molekülen ist in diesem Zusammenhang ihr permanentes Dipolmoment, das sich auf eine ungleichmäßige Verteilung der Elektronendichte im Molekül zurückführen lässt. Falls sich das Dipolmoment nicht vollständig isotrop orientiert, hat es ein makroskopisches Oberflächenpotential (engl. giant surface potential, GSP) bzw. eine dielektrische Polarisation der gesamten Dünnschicht zur Folge. Die Existenz des GSP ist bereits seit einiger Zeit bekannt [1, 7, 10]. Seine Auswirkungen auf den Ladungstransport bzw. -injektion in Bezug auf organische Halbleiter werden erst seit kurzem häufiger untersucht [3,7,11]. Das Konzept der polaren Dotierung erlaubt nun, ein GSP in ursprünglich unpolare organische Matrizen einzubauen [2]. Mittels Dotierung lassen sich auch polare Lochleiter herstellen, die im weiteren Verlauf der Arbeit eine Untersuchung der Auswirkungen des GSP auf die Lochleiterschicht in einer OLED erlauben. In undotierten Schichten wurde ein GSP bisher hauptsächlich in Elektronenleitern beobachtet [6, 12]. Exemplarisch wird dazu das Mischsystem NPB:Alq3 in verschiedenen Konzentrationen und auf verschiedenen Substraten in Bezug auf Lochinjektion und Lochtransport näher untersucht. Es werden sowohl monopolare Bauteile, die ausschließlich Lochtransport aufweisen, als auch vollständige OLEDs verwendet. Bei OLEDs kommt dabei eine im Laufe dieser Arbeit mit entwickelte neue Methode zum Einsatz, die diese OLEDs wie sog. Metall-Isolator-Halbleiter-Dioden (engl. metalinsulator-semiconductor, MIS) behandelt und Rückschlüsse auf die Energiebarriere für Ladungsinjektion erlaubt [13, 14]. Des Weiteren stehen Ergebnisse aus der ultravioletten Photoelektronenspektroskopie zur Verfügung, die einen Vergleich mit der Ausrichtung der Energieniveaus von NPB am Kontakt ermöglichen. Mittels des Vergleichs verschiedener Messmethoden im Bezug auf die Injektionseigenschaften kann der Effekt des GSP auf verschiedene Parameter im Bauteil nachgewiesen werden, deren Zusammenspiel in sämtlichen Bauteiltypen zu einem Optimum bei moderaten Dotierkonzentrationen von ca. 5% führt

The effect of age on short-term and mid-term outcomes after thoracoscopic Ivor Lewis esophagectomy: a propensity score-matched analysis

Background: The number of elderly patients diagnosed with esophageal cancer rises. Current information about outcomes in elderly patients undergoing thoracoscopic Ivor Lewis esophagectomy is limited. The objective of this study was to evaluate the influence of age on short-and mid-term outcomes after thoracoscopic Ivor Lewis esophagectomy. Methods: A retrospective review of 188 patients with esophageal cancer undergoing thoracoscopic Ivor Lewis esophagectomy between August 2014 and July 2019 was performed. Patients were divided into patients aged > 75 years (elderly group (EG), n = 37) and patients = grade III) were compared. Results: After matching 74 patients remained (n = 37 in each group). Postoperatively, no significant differences in major and overall complications, intra-hospital and 30-day mortality, disease-free or overall survival up to 3 years after surgery were noted. The incidence of pulmonary complications (65% vs. 38%) and pneumonia (54% vs. 30%) was significantly higher and the median hospital length of stay (12 vs. 14 days) significantly longer in the EG versus YG. Conclusion: Thoracoscopic Ivor Lewis esophagectomies resulted in acceptable postoperative major morbidity and mortality without compromising 3-years overall and disease-free survival in elderly compared to younger patients with esophageal cancer. However, the incidence of postoperative pulmonary complications was higher in patients aged over 75 years

Requerimento ao Conselho da Cidade de Leipzig

This is a translation by Rubens Russomanno Ricciardi and Dorothea Hofmann, with commentary notes, of a manuscript application written by Bach in 1730 and addressed to the City Council of Leipzig. Albeit referring to sacred music, Bach focuses on the artistic conditions for the musical performance of its vocal and instrumental ensembles. He also vindicates a greater number of scholarships for his students, as well as stricter criteria in student admission to the St. Thomas Church school. Finally, Bach, in his pedagogy, divides the students into three categories: the employable, the not-yet-employable, and the unemployable.Trata-se da tradução, com notas comentadas, feita por Rubens Russomanno Ricciardi e Dorothea Hofmann, de um requerimento manuscrito, redigido por Bach, em 1730, endereçado ao Conselho da Cidade de Leipzig. Não obstante se referir à música sacra, Bach se concentra em condições artísticas para a performance musical de seus conjuntos vocal e instrumental. Reivindica também um número maior de bolsas para seus alunos, bem como critérios mais rigorosos na admissão de estudantes para Escola da Igreja de Tomé. Por fim, Bach, em sua pedagogia, divide os alunos em três categorias: os utilizáveis, os ainda não utilizáveis e os incapazes

Structurally and functionally unique complexins at retinal ribbon synapses

Ribbon synapses in retinal sensory neurons maintain large pools of readily releasable synaptic vesicles. This allows them to release several hundreds of vesicles per second at every presynaptic release site. The molecular components that cause this high transmitter release efficiency of ribbon synapses are unknown. In the present study, we identified and characterized two novel vertebrate complexins (CPXs), CPXs III and IV, that are the only CPX isoforms present in retinal ribbon synapses. CPXs III and IV are COOH-terminally farnesylated, and, like CPXs I and II, bind to SNAP receptor complexes. CPXs III and IV can functionally replace CPXs I and II, and their COOH-terminal farnesylation regulates their synaptic targeting and modulatory function in transmitter release. The novel CPXs III and IV may contribute to the unique release efficacy of retinal sensory neurons

Feline leukaemia virus: half a century since its discovery

In the early 1960s, Professor William (Bill) F.H. Jarrett was presented with a timeGÇôspace cluster of cats with lymphoma identified by a local veterinary practitioner, Harry Pfaff, and carried out experiments to find if the condition might be caused by a virus, similar to lymphomas noted previously in poultry and mice. In 1964, the transmission of lymphoma in cats and the presence of virus-like particles that resembled GÇÿthe virus of murine leukaemiasGÇÖ in the induced tumours were reported in Nature. These seminal studies initiated research on feline leukaemia virus (FeLV) and launched the field of feline retrovirology. This review article considers the way in which some of the key early observations made by Bill Jarrett and his coworkers have developed in subsequent years and discusses progress that has been made in the field since FeLV was first discovered

Humoral Immune Response following SARS-CoV-2 Vaccination in Liver Transplant Recipients

As COVID-19 remains an issue in transplantation medicine, a successful vaccination can prevent infections and life-threatening courses. The probability of poor immune response in liver transplant recipients gained attention and insecurity among those patients, leading us to investigate the humoral immune response alongside the influence of underlying diseases and immunosuppressive regimen on seroconversion rates. We included 118 patients undergoing anti-spike-protein-IgG testing at least 21 days after completed SARS-CoV-2 vaccination. Ninety-seven patients also underwent anti-spike-protein-IgA testing. The influence of baseline demographics, immunosuppressive regimen and underlying disease on seroconversion was analyzed, and 92 of 118 patients (78.0%) developed anti-spike-protein-IgG antibodies. Patients with a history of alcoholic liver disease before transplantation showed significantly lower seroconversion rates (p = 0.006). Immunosuppression also significantly influenced antibody development (p < 0.001). Patients run on a mycophenolate mofetil (MMF)-based regimen were more likely not to develop antibodies compared to patients run on a non-MMF regimen (p < 0.001). All patients weaned off immunosuppression were seropositive. The seroconversion rate of 78.0% in our cohort of liver transplant recipients is promising. The identification of alcohol-induced cirrhosis as underlying disease and MMF for immunosuppression as risk factors for seronegativity may serve to identify vaccination non-responder after liver transplantation

Hypoxia Attenuates Pressure Overload-Induced Heart Failure

Background Alveolar hypoxia is protective in the context of cardiovascular and ischemic heart disease; however, the underlying mechanisms are incompletely understood. The present study sought to test the hypothesis that hypoxia is cardioprotective in left ventricular pressure overload (LVPO)–induced heart failure. We furthermore aimed to test that overlapping mechanisms promote cardiac recovery in heart failure patients following left ventricular assist device‐mediated mechanical unloading and circulatory support. Methods and Results We established a novel murine model of combined chronic alveolar hypoxia and LVPO following transverse aortic constriction (HxTAC). The HxTAC model is resistant to cardiac hypertrophy and the development of heart failure. The cardioprotective mechanisms identified in our HxTAC model include increased activation of HIF (hypoxia‐inducible factor)‐1α–mediated angiogenesis, attenuated induction of genes associated with pathological remodeling, and preserved metabolic gene expression as identified by RNA sequencing. Furthermore, LVPO decreased Tbx5 and increased Hsd11b1 mRNA expression under normoxic conditions, which was attenuated under hypoxic conditions and may induce additional hypoxia‐mediated cardioprotective effects. Analysis of samples from patients with advanced heart failure that demonstrated left ventricular assist device–mediated myocardial recovery revealed a similar expression pattern for TBX5 and HSD11B1 as observed in HxTAC hearts. Conclusions Hypoxia attenuates LVPO‐induced heart failure. Cardioprotective pathways identified in the HxTAC model might also contribute to cardiac recovery following left ventricular assist device support. These data highlight the potential of our novel HxTAC model to identify hypoxia‐mediated cardioprotective mechanisms and therapeutic targets that attenuate LVPO‐induced heart failure and mediate cardiac recovery following mechanical circulatory support