CH3NH3PbI3 perovskite single crystals: surface photophysics and their interaction with the environment

Here we identify structural inhomogeneity on a micrometer scale across the surface of a CH₃NH₃PbI₃ perovskite single crystal. At the crystal edge a local distortion of the crystal lattice is responsible for a widening of the optical bandgap and faster photo-carrier recombination. These effects are inherently present at the edge of the crystal, and further enhanced upon water intercalation, as a preliminary step in the hydration of the perovskite material.     

Reversible photo-induced trap formation in mixed-halide hybrid perovskites for photovoltaics

We report on reversible, light-induced transformations in (CH₃NH₃)Pb(Br_xI_1–x)₃. Photoluminescence (PL) spectra of these perovskites develop a new, red-shifted peak at 1.68 eV that grows in intensity under constant, 1-sun illumination in less than a minute. This is accompanied by an increase in sub-bandgap absorption at ∼1.7 eV, indicating the formation of luminescent trap states. Light soaking causes a splitting of X-ray diffraction (XRD) peaks, suggesting segregation into two crystalline phases. Surprisingly, these photo-induced changes are fully reversible; the XRD patterns and the PL and absorption spectra revert to their initial states after the materials are left for a few minutes in the dark. We speculate that photoexcitation may cause halide segregation into iodide-rich minority and bromide-enriched majority domains, the former acting as a recombination center trap. This instability may limit achievable voltages from some mixed-halide perovskite solar cells and could have implications for the photostability of halide perovskites used in optoelectronics.     

Neural correlates of semantic and syntactic processes in the comprehension of case marked pronouns: Evidence from German and Dutch

Background  

It is well known that both semantic and syntactic information play a role in pronoun resolution in sentences. However, it is unclear what the relative contribution of these sources of information is for the establishment of a coreferential relationship between the pronoun and the antecedent in combination with a local structural case constraint on the pronoun (i.e. case assignment of a pronoun under preposition governing). In a prepositional phrase in German and Dutch, it is the preposition that assigns case to the pronoun. Furthermore, in these languages different overtly case-marked pronouns are used to refer to male and female persons. Thus, one can manipulate biological/syntactic gender features separately from case marking features.     

Analyticity for Some Operator Functions from Statistical Quantum Mechanics

For rather general thermodynamic equilibrium distribution functions the density of a statistical ensemble of quantum mechanical particles depends analytically on the potential in the Schr?dinger operator describing the quantum system. A key to the proof is that the resolvent to a power less than one of an elliptic operator with non-smooth coefficients, and mixed Dirichlet/Neumann boundary conditions on a bounded up to three-dimensional Lipschitz domain boundedly maps the space of square integrable functions to the space of essentially bounded functions. Dedicated to Günter Albinus Submitted: November 21, 2008. Accepted: March 31, 2009.     

Beitrag zur Charakterisierung von hochborhältigen Chrom-Nickel-Molybdän-Kupfer-Stählen mit Hilfe der stereometrischen Analyse

Zusammenfassung Eine Serie von Chrom-Nickel-Molybdän-Kupfer-Bor-Stählen mit Borgehalten von 0,5 bis 1,9 Gew.% wurde mit Methoden der stereometrischen Analyse untersucht. Mit verschiedenen Verfahren der Phasenanalyse wurden Informationen über die Verteilung der Elemente und die chemische Zusammensetzung der Phasen dieser Werkstoffe gewonnen. Diese Informationen dienten als Ausgangspunkt für die Strukturanalyse der Boridphase, in deren Rahmen in erster Linie die Frage des Einflusses der chemischen Zusammensetzung auf die Größe der Elementarzelle und damit die Dichte der Boridphase untersucht wurde. Die Werkstoffserie wurde schließlich gefügeanalytisch charakterisiert, wobei die Technik der automatischen Linearanalyse mit der Mikrosonde und die chemische Isolierung der Boride mit lichtoptischer Untersuchung des Isolates angewendet und beispielhaft gegenübergestellt wurden. Die mit den Methoden der Struktur-, Phasen- und Gefügeanalyse gewonnenen Informationen wurden schließlich in einer Bilanz verknüpft.

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On the characterization of Cr-Ni-Mo-Cu-B-alloys by means of stereometric analysis

Summary A series of Chromium-Nickel-Molybdenum-Copper-Boron steel with Boron concentrations in the range from 0,5–1,9 wt.% has been investigated with the methods of stereometric analysis. Different techniques of phase analysis are used to gain information about the distribution of the different elements and the composition of the phases. These informations are the basis for structure analysis of the boride phase. Within this chapter mainly the influence of chemical composition of the boride on the lattice parameters and consequently on the density of the phase are investigated. Furthermore this series of steel is investigated with different methods of quantitative metallography (automatic linear analysis with an electron microprobe and chemical isolation of the boride phase with subsequent light microscopical investigation). The results obtained with the two techniques are compared for one sample. Finally the informations obtained with structure analysis, phase analysis and quantitative metallography are combined to form a balance of stereometric analysis.

     

ICP-AES法测定色漆可溶性金属含量

用ICP-AES法测定了色漆中的“可溶性”金属铬、镉、铅元素，考察了不同酸度对分析结果的影响，优化了测试条件。进行了回收率和精密度试验。并用原子吸收光谱国标方法进行对照，结果一致。