33 research outputs found
Wet chemical passivation of interface defects in a a SI H c Si heterojunction solar cells with randomly distributed pyramids
No full textWET CHEMICAL PASSIVATION OF INTERFACE DEFECTS IN a SI H c SI HETEROJUNCTION SOLAR CELLS WITH RANDOMLY DISTRIBUTED PYRAMIDS H. Angermann, J. Rappich, K. v. Maydell, E. Conrad, I. Sieber, D. Schaffarzik and M. Schmidt Hahn Meitner Institut Berlin, Kekul str.5, D 12489 Berlin Corresponding author H. Angermann, Hahn Meitner Institut Berlin HMI , Kekul str.5, D 12489 Berlin, Tel 49 30 8062 1368, Fax 49 30 8062 1333 e mail angermann helmholtz berlin.de ABSTRACT Two non destructive, very surface sensitive tech niques, the large signal field modulated surface photovoltage SPV method and pulsed photoluminescence spectroscopy PL were applied to investigate both wet chemically treated substrate surfaces and a Si c Si interfaces. In order to prepare silicon substrates with randomly distributed pyramids without surface micro roughness and native oxide contamination and to passivate them during the technological process, we investigated special combinations of wet chemical etching and cleaning procedures. Compared to conventional pre treatments, significantly lower densities surface states and recombination loss were achieved on silicon substrates textured with randomly distributed upside pyramids and on the resulting a Si c Si in terfaces after deposition. It was shown that the open circuit voltage Voc and solar cell efficiency of TCO a Si H n c Si p Al solar cells are mainly influence by the preparation induced morphology and electronic properties of substrate surface. Keywords silicon substrates, defect density, wet chemical pretreatmen
Diedrich Becker, Musician. Approximation to a musician and his era
No full textDie Untersuchung über Diedrich Becker versucht einen Brückenschlag zwischen musikhistorischer und soziokultureller Betrachtung eines sogenannten "Kleinmeisters": Diedrich Becker (1623-1679), der als Komponist von Sonaten- und Suitensammlungen eine gewisse musikhistorische Bedeutung hat, dessen Biographie aber etliche Lücken aufweist, wird daher im sozialen wie auch kulturellen Kontext seiner Zeit dargestellt. Eine eingehende Betrachtung der Lebensstationen wie die Zeit als Mitglied der Celler Hofkapelle, aber auch sein Wirken als Ratsmusikant in Hamburg lassen auf zahlreiche Verbindungen zu anderen Künstlern seiner Zeit schließen. Beckers Wirken als Komponist zeigt sich in Sonaten und Suiten für Streicherensembles sowie in geistlichen Werken; vor allem die Überlieferungsgeschichte weist wiederum auf das dichte Beziehungsgeflecht hin, innerhalb dessen sich Becker bewegte. Im Anhang finden sich das Werkverzeichnis, Dokumente zur Biographie Beckers sowie alle erhaltenen Kompositionen.The study of Diedrich Becker tries to bridge the gap between music history and socio-cultural consideration of a so-called "small master": Diedrich Becker (1623-1679), the composer of sonatas and suites collections has some music historical significance, but whose biography has many gaps, is therefore shown in both social and cultural context of his time. An in-depth look at the life stages as time as a member of the Celle court orchestra, but also his work as a "Ratsmusikant" in Hamburg to make numerous connections to other artists of his time close. Becker's work as a composer is evident in sonatas and suites for string ensembles, as well as sacred music, especially the tradition history again indicates the dense network of relationships within which Becker moved. The appendix contains the catalogue of works, documents of Becker's biography and all conserved compositions
Wet Chemical Conditioning of Silicon Substrates for a Si H c Si Heterojunctions
No full textThe influence of wet chemical silicon Si substrate pre treatments on surface morphology and electronic interface properties is discussed for various hetero interfaces of crystalline Si c Si and Si oxides SiOx , or amorphous materials such as Si a Si H , Si nitride a SiNx H and Si carbide a SiC H , which are typically applied in Si heterostructure solar cells. Combined application of surface sensitive tech niques, the field modulated surface photovoltage SPV , ex situ and in situ photoluminescence PL measurements, atomic force microscopy AFM , scanning electron microscopy SEM , spectroscopic ellipsometry in the ultra violet and visible region UV VIS SE and Fourier Transform infrared ellipsometry FTIR SE , total hemispherical UV NIR reflectance measurements, microwave detected photo conductance decay W PCD and quasi steady state photo conductance QSSPC provides detailed information about the influence of wet chemical treatments on preparation induced micro roughness, surface charge, energetic distribution of interface states Dit E and the resulting interface recombination behaviour of wet chemically passivated Si substrates with special surface morphology. The stability of wet chemical surface passivation during storage in ambient air is found to be strongly influenced by the preparation induced surface morphology. As shown for various heterojunction structures, the effect of optimized wet chemical pre treatments can be preserved during the subsequent soft plasma enhanced chemical vapour deposition of a Si H, a SiNx H or a SiC H. As demonstrated for selected examples, the results of these investigations could be successfully used to enhance the energy conversion efficiency of hetero junction solar cells prepared on flat, saw damage etched and textured Si substrates. Implementation of optimised wet chemical surface pre treatments prior to a Si H deposition in ZnO a Si H n c Si p Al heterojunction solar cells with pyramidal texturisation increased significantly the solar cell parameters Isc, Voc, fill factor and enhanced the solar cell efficiency from 17.4 confirmed to 18.
Review of German, Jew, Muslim, Gay: The Life and Times of Hugo Marcus By Marc David Baer.
No full textWhen Hugo Marcus (1880–1966), a German Jewish gay author, philosopher, and activist, converted to Islam in 1925, he “did not know yet what significance the word ‘jihad’ would one day mean to [him]. For it also signifies the duty to leave the country that is under godless rule, even if in so doing one has to give up one’s homeland. In this sense,” he wrote retrospectively in 1951, “I have been on a pilgrimage for the last twelve years” (135). In a footnote to this quotation from Marcus’s unpublished manuscript, Marc David Baer, author of this fascinating, erudite, and unusual biography, clarifies Marcus’s probable confusion between the Islamic terms jihad (holy war) and hejira (exile, migration). Driven away from his homeland in 1939, Marcus interpreted his own life in the religious vocabulary of Islam. But, ascending to become one the most prominent Muslims in pre-war Berlin, he also interpreted Islam in the light of his own experiences, worldviews, and wishes: as a German Jewish gay man. Not only was Marcus assigned with the monumentally significant project of editing and annotating the Qur’an’s translation into German, aimed at rendering it accessible to non-Arab speakers (reminiscent of Martin Buber and Franz Rosenzweig’s project of the Hebrew Bible’s translation into German, which would be an interesting point of comparison), but he also published numerous articles discussing Islam and philosophy as well as homoerotic fiction with Islamic themes
Russian merchants in Livonia in the 17th century
No full textThe paper describes the trade activity of Russian merchants in Livonia (in the widest sense of
the term, including Estonia), which was under the rule of Sweden and Poland in the 17th century and later
only under the Swedish rule. The main purpose of Russian merchants in the beginning of the 17th century
was Reval (Tallinn) and later Narva. They also visited Riga and much less Dorpat (today’s Tartu). The author
was able to identify new evidence of this by working in the archives of Baltic cities. Shopping yards for
Russian merchants were established in Riga, Narva and Dorpat, which served as living quarters and a place
for storing and selling goods. Interesting information about this is provided by the accounts of German farm
administrators in Narva and Derpt, which are analyzed in this article for the first time. Russian guests in
Livonia were mainly middle and minor merchants, as well as representatives of the largest trading companies
in Novgorod and Pskov, commissioners of the tsars and, on the other hand, artisans, peasants and fishermen.
Their activities served the extensive European trade in linen, hemp, leather, fat and fur as the main Russian
supplies. The Livonian inhabitants were also supplied with industrial and agricultural products. The number
of visitors to Livonia from northwest Russia and beyond was significantly higher than the number of Livonian
merchants trading in Novgorod, Pskov and Moscow
A radiation and propagation problem for a Helmholtz equation with a compactly supported nonlinearity
No full textThe present work describes some extensions of an approach, originally
developed by V.V. Yatsyk and the author, for the theoretical and numerical
analysis of scattering and radiation effects on infinite plates with cubically
polarized layers. The new aspects lie on the transition to more generally
shaped, two- or three-dimensional objects, which no longer necessarily have to
be represented in terms a Cartesian product of real intervals, to more general
nonlinearities (including saturation) and the possibility of an efficient
numerical approximation of the electromagnetic fields and derived quantities
(such as energy, transmission coefficient, etc.). The paper advocates an
approach that consists in transforming the original full-space problem for a
nonlinear Helmholtz equation (as the simplest model) into an equivalent
boundary-value problem on a bounded domain by means of a nonlocal
Dirichlet-to-Neumann (DtN) operator. It is shown that the transformed problem
is equivalent to the original one and can be solved uniquely under suitable
conditions. Morever, the impact of the truncation of the DtN operator on the
resulting solution is investigated, so that the way to the numerical solution
by appropriate finite element methods is available
Active Learning for Real Time Detection of Polyps in Videocolonoscopy
No full textAbstractIn this paper a method to perform real-time detection of polyps in videocolonoscopy is introduced. Polyps are at the origins of colorectal cancer which is one of the deadliest diseases in the world. Many methods to improve detection of polyps have been proposed so far. However performance of these methods strongly depends on the available computational resources and, until now, are not able to perform real-time detection during a standard examination. The proposed method, based on active learning, is able to solve these issues. Most precisely, this approach allows us to detect approximately 90% of polyps on a freely available database introduced to the community in 2012, for a F2 score of 65%, and matches real-time constraint by making possible the analysis of a frame in only 0.023s (average value) on a standard computer not necessarily dedicated to that kind of application
IPA free texturization of n type Si wafers Correlation of optical, electronic and morphological surface properties
No full textThe application of an Isopropanol IPA free potassium hydroxide KOH solution was evaluated in order to prepare random pyramids on as cut crystalline n type Si wafers to reduce reflection losses of substrates for high efficiency hetero junction solar cells. The influence of saw damage removal and texturization processes on the resulting pyramid morphology and the corresponding interplay between optical and electronic properties are revealed. It is shown that both the depth of the saw damage etching SDE and the duration of the texturization etching have crucial influence on the resulting pyramid size distribution. Reflection losses can be reduced with decreasing fraction of small pyramids. By intermediate saw damage removal and texture etching times in IPA free KOH solution the densities of electronic interface states were found to be strongly decreased Dit,min lt; 5 E 11 cm 2eV 1 , in comparison to pyramids prepared in IPA containing solutions. For the purpose of fabricating amorphous crystalline a Si H c Si heterojunction solar cells the Si substrate surfaces were passivated with an intrinsic layer of amorphous silicon a Si H i leading to minority charge carrier lifetimes taueff of 2 to 4 ms, depending on the preceding texturization process
Reduction of the Interface Defect Density on Crystalline Silicon Solar Cell Substrates by Wet chemical Preparation of Ultrathin SiOx Passivation Layers
No full textUltrathin SiO tunneling layers can be implemented in a wide range of solar cell applications, like for the passivation of the heterojunction interface in a Si H c Si solar cells. Here we present the successful preparation of ultrathin SiO layers by wet chemical oxidation in HCl H O. Applying surface photovoltage SPV and spectral ellipsometry SE measurements during the initial phase of oxidation, the influence of substrate morphology, the oxidation parameters and the preceding process steps on the resulting interface state density was systematically investigated. With respect to the standard RCA process, optimized sequences of smoothing, oxide removal and oxidation of textured Si wafers allow for a distinct reduction of the density of interface states both on hydrophilic and hydrophobic substrate surfaces, as required for different subsequent layer depositions e.g contact layers, passivation layers or solar cell fabricatio
Effect of wet chemical substrate smoothing on passivation of ultrathin SiO2 n Si 111 interfaces prepared with atomic oxygen at thermal impact energies
No full textUltrathin SiO2 layers for potential applications in nano scale electronic and photovoltaic de vises were prepared by exposure to thermalized atomic oxygen under UHV conditions. Wet chemical substrate pre treatment, layer deposition and annealing processes were applied to improve the electronic Si SiO2 interface properties. This favourable effect of optimized wet chemical pre treatment can be preserved during the subsequent oxidation. The corresponding atomic scale analysis of the electronic interface states after substrate pre treatment and the subsequent silicon oxide layer formation is performed by field modulated surface photovolt age SPV , atomic force microscopy AFM and spectroscopic ellipsometry in the ultra violet and visible region UV VIS S
