Versuche zur stufenweisen epoxid/methacrylat-photopolymerisation mit diaryliodoniumsalz-photoinitiatoren

DSC-investigations confirm the experimental result that the selective photopolymerization of MMA and phenylglycidether (PGE) from a mixture of both monomers is possible with diaryliodoniumsalts/benzoinmethylether as a photoinitiator. The separation of both processes is dependent on light-intensity and on the composition of the monomer mixture. From a monomer mixture (80 weight-% MMA and 20 Weight-% PGE) it is possible to polymerize selectively MMA with light intensity I = 0.7 mJ/s cm², if the reaction is cut off immediately after the appearence of the gel effect (30 minutes). The epoxide polymerization can be completed afterwards by means of unfiltered light from a Hg-pressure lamp. The time separation of both processes will only succeed if MMA is the main part of the monomer mixture.     

Experimentelle Ermittlung von Kennwerten für den hydraulischen Transport von Erzen

Hydraulischer Erztransport. Optimierung hinsichtlich Energieverbrauch und Betriebssicherheit. Ermittlung der kritischen Geschwindigkeit und der Widerstandszahl der hydraulischen Förderung als Funktion der Erzkonzentration. Betriebsnahe Versuche auf einer Pilotanlage.     

New energetic materials from triazoles and tetrazines

Abstract

Nitrotriazoles and tetrazines - among them compounds without nitro groups - are multi-purpose energetic materials. We found examples for all classes of explosives: primary explosives, IHE, and gas generators. By reaction with methazonic acid 3-amino-5-nitro-1,2,4-triazole (ANTA) could be converted into a new explosive with theoretically improved performance, a bitriazolyl compound. Starting with 3, 6-diamino-1,2,4,5-tetrazine three compounds of differing explosive behaviour were prepared. Physical data and small scale explosive properties of the new substances are published.     

Ordnungszustände in Eisen-Silizium-Legierungen

Konzentrations- und Temperaturabhängigkeit des Fernordnungsgrades in Eisen-Silizium-Legierungen. Anisotrope Nahordnung zwischen 9 und 14 At-% Si. Gitterphysikalische Deutung der Ordnungszustände.     

Perovskite-Inspired Lead-Free Ag2BiI5 for Self-Powered NIR-Blind Visible Light Photodetection

In recent years,solution-processible semiconductors with perovskite or perovskite-inspired structures have been extensively investigated for optoelectronic applications.In particular,silver-bismuth-halides have been identified as especially promising because of their bulk properties and lack of heavily toxic elements.This study investigates the potential of Ag2BiI5 for near-infrared(NIR)-blind visible light photodetection,which is critical to emerging applications(e.g.,wearable optoelectronics and the Internet of Things).Self-powered photodetectors were realized and provided a near-constant≈100 mA W−1 responsivity through the visible,a NIR rejection ratio of>250,a long-wavelength responsivity onset matching standard colorimetric functions,and a linear photoresponse of>5 orders of magnitude.The optoelectronic characterization of Ag2BiI5 photodetectors additionally revealed consistency with one-center models and the role of the carrier collection distance in self-powered mode.This study provides a positive outlook of Ag2BiI5 toward emerging applications on low-cost and low-power NIR-blind visible light photodetector.     

Strong Depletion in Hybrid Perovskite p–n Junctions Induced by Local Electronic Doping

A semiconductor p–n junction typically has a doping‐induced carrier depletion region, where the doping level positively correlates with the built‐in potential and negatively correlates with the depletion layer width. In conventional bulk and atomically thin junctions, this correlation challenges the synergy of the internal field and its spatial extent in carrier generation/transport. Organic–inorganic hybrid perovskites, a class of crystalline ionic semiconductors, are promising alternatives because of their direct badgap, long diffusion length, and large dielectric constant. Here, strong depletion in a lateral p–n junction induced by local electronic doping at the surface of individual CH₃NH₃PbI₃ perovskite nanosheets is reported. Unlike conventional surface doping with a weak van der Waals adsorption, covalent bonding and hydrogen bonding between a MoO₃ dopant and the perovskite are theoretically predicted and experimentally verified. The strong hybridization‐induced electronic coupling leads to an enhanced built‐in electric field. The large electric permittivity arising from the ionic polarizability further contributes to the formation of an unusually broad depletion region up to 10 µm in the junction. Under visible optical excitation without electrical bias, the lateral diode demonstrates unprecedented photovoltaic conversion with an external quantum efficiency of 3.93% and a photodetection responsivity of 1.42 A W^?1.     

Kinetische Untersuchung zur platinkatalysierten Hydrosilylierung von Vinylsiloxanen mit Hydrogensiloxanen

Kinetic Investigation of the Platinum-catalysed Hydrosilylation of Vinylsiloxanes with Hydrogensiloxanes A kinetic investigation of the platinum-catalysed hydrosilylation of monofunctional oligomeric vinylsiloxanes by monofunctional oligomeric hydrogensiloxanes was performed under stoichiometric conditions with use of quantitative ¹H-NMR spectrometry. The reaction rate up to 50% conversion can be expressed by v=k [Pt]. During further hydrosilylation the kinetic changed to second order. No induction period was observed. A hydrogensiloxane with a dimethylsilyl end group gives much higher rates than a siloxane with a methylsiloxy group. The main reactions of all hydrosilylations, determined by GC-MS and ²⁹Si-NMR, are β-additions. Less then 5% α-products are obtained.     

Molecular Structure‐Dependent Charge Injection and Doping Efficiencies of Organic Semiconductors: Impact of Side Chain Substitution

Due to the highly anisotropic nature of π ‐conjugated molecules, the molecular structure of organic semiconductors can significantly affect the device performance of organic optoelectronics. Here, the molecular structure dependence on charge injection and doping efficiencies is investigated by characterizing the typical hole transport material of N,N′‐bis(naphthalen‐1‐yl)‐N,N′‐bis(phenyl)‐benzidine (NPB) and its derivatives N,N′‐bis(naphthalen‐1‐yl)‐N,N′‐bis(phenyl)‐9,9‐dimethyl‐fluorene (DMFL‐NPB) and N,N′‐bis(naphthalen‐1‐yl)‐N,N′‐bis(phenyl)‐9,9‐diphenyl‐fluorene (DPFL‐NPB)]. Using photoelectron spectroscopy data and density functional theory calculation, it is identified that the side chain substitution in NPB and its derivatives plays a crucial role in the intrinsic injection and transport properties, and doping efficiency. The inner twist of the two main benzene rings in NPB is changed from out‐of‐plane to in‐plane due to the alkyl or phenyl side chains of DMFL‐NPB or DPFL‐NPB, which reduces the ionization energies and thus decreases the hole injection barriers at the indium tin oxide/organic interface. The doping efficiency in 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F₄‐TCNQ) doped systems is also highly dependent on the degree of intermolecular orbital energy hybridization with respect to the side chain substitution. These findings show that the rational design of molecular structures with suitable side chains is crucial for achieving high‐performance organic devices.     

Direct Observation of Conductive Polymer Induced Inversion Layer in n‐Si and Correlation to Solar Cell Performance

Heterojunctions formed by ultrathin conductive polymer [poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate)—PEDOT:PSS] films and n‐type crystalline silicon are investigated by photoelectron spectroscopy. Large shifts of Si 2p core levels upon PEDOT:PSS deposition provide evidence that a dopant‐free p–n junction, i.e., an inversion layer, is formed within Si. Among the investigated PEDOT:PSS formulations, the largest induced band bending within Si (0.71 eV) is found for PH1000 (high PEDOT content) combined with a wetting agent and the solvent additive dimethyl sulfoxide (DMSO). Without DMSO, the induced band bending is reduced, as is also the case with a PEDOT:PSS formulation with higher PSS content. The interfacial energy level alignment correlates well with the characteristics of PEDOT:PSS/n‐Si solar cells, where high polymer conductivity and sufficient Si‐passivation are also required to achieve high power conversion efficiency.