Hochschule Ulm

Neu-Ulm, Germany

Hochschule Ulm

Neu-Ulm, Germany
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Vajen K.,University of Kassel | Sparber W.,EURAC Bozen | Heilscher G.,Hochschule Ulm
30th ISES Biennial Solar World Congress 2011, SWC 2011 | Year: 2011

A committee of university teachers for renewable energies has been founded in German-speaking countries in 2005. The main aim was to install a forum for the exchange of experiences and ideas about teaching on higher education level. The paper discusses the experiences made in the last six years, organizational issues, prerequisites for the transfer of the concept of the committee to other regions, as well as an extension of the network on a European or even global scale.

Merdes S.,Helmholtz Center Berlin | Ziem F.,Helmholtz Center Berlin | Lavrenko T.,Hochschule Ulm | Walter T.,Hochschule Ulm | And 5 more authors.
Progress in Photovoltaics: Research and Applications | Year: 2015

Sequentially processed Cu(In,Ga)(Se,S)2 based solar cells with externally certified efficiencies exceeding 16% were achieved with atomic layer deposited Zn(O,S) buffers. • Efficiencies up to 13% were achieved with 30 × 30 cm2 large area modules.• Stability tests show that heat treatment has a minor impact on the open circuit voltage of the devices, whereas the fill factor drift remains below 10We report the development of Cd-free buffers by atomic layer deposition for chalcopyrite-based solar cells. Zn(O,S) buffer layers were prepared by atomic layer deposition on sequentially grown Cu(In,Ga)(Se,S)2 absorbers from Bosch Solar CISTech GmbH. An externally certified efficiency of 16.1% together with an open circuit voltage of 612 mV were achieved on laboratory scale devices. Stability tests show that the behavior of the ALD-Zn(O,S)-buffered devices can be characterized as stable only showing a minor drift of the open circuit voltage and the fill factor. © 2015 John Wiley & Sons, Ltd.

Ott T.,Hochschule Ulm | Walter T.,Hochschule Ulm | Unold T.,Helmholtz Center Berlin
Thin Solid Films | Year: 2013

Cu(In,Ga)Se2 solar cells exhibit non-idealities with respect to a standard diode especially at low temperatures: a blocking behavior of the dark current in forward direction, a crossover of the dark and illuminated current-voltage-characteristics and a saturation of the open circuit voltage with respect to temperature and illumination intensity. It will be demonstrated that at low temperatures a Cu(In,Ga)Se2 solar cell with a back barrier essentially behaves as a phototransistor with a ZnO-emitter and Schottky collector. Hereby, the base current is provided by photoexcited holes in the field-free region of the absorber. Comparing simulations with measurements it will be illustrated that these non-idealities can be quantitatively explained. It will be shown that depending on the barrier height of the back diode and the doping profile these characteristics even occur at room temperature. This back barrier might be due to a Schottky contact or to a low doping at the back contact and a higher doping level close to the heterointerface. © 2012 Elsevier B.V.

Gutenschwager K.,Hochschule Ulm | Volker S.,Hochschule Ulm | Radtke A.,SimPlan Integrations GmbH | Zeller G.,SimPlan AG
Proceedings - Winter Simulation Conference | Year: 2012

The routing of vehicles or personnel in complex logistics systems is a task that needs to be solved in numerous applications, e.g., detailed models of transport networks or order picking areas. The number of relevant nodes in such networks can easily exceed 10,000 nodes. Often, a basic task is finding the shortest path from one node (start) to another (destination). Within the last years various simulation tools have been extended by respective algorithms. However, the execution time of the simulation model may significantly depend on the number of nodes in the network. We present algorithms from the literature and a comparison of three simulation tools with respect to execution time and model size for different scenarios. We further present an approach to work with so called sub-networks, i.e., the network is separated into areas, where finding the shortest path includes the task of starting at a node in one sub-network with a destination in another one. © 2012 IEEE.

Some fragrances used in everyday products are strong contact allergens. Their application in cosmetic products is restricted. However, consumers who want to or need to avoid allergenic fragrances must invest a lot of efforts. Independent support for consumers, e. g. by the German Allergy and Asthma Association (Deutscher Allergie- und Asthmabund e. V., DAAB) or by "Öko-Test", could improve health protection. The analysis of such recommendations, however, reveals that today this support does not guarantee a sufficient consumer protection. Instead other solutions are needed, either easily understandable warning labels on products containing strong allergens, stronger restrictions, or even bans of allergenic fragrances in everyday products. © Springer-Verlag 2010.

Chua R.H.,Nanyang Technological University | Chua R.H.,Robert Bosch GmbH | Li X.,Nanyang Technological University | Walter T.,Hochschule Ulm | And 5 more authors.
Applied Physics Letters | Year: 2016

Zinc oxysulfide buffer layers with [O]:[S] of 1:0, 6:1, 4:1, 2:1, and 1:1 ratios were deposited by atomic layer deposition on Cu(In,Ga)(S,Se)2 absorbers and made into finished solar cells. We demonstrate using Time-Resolved Photoluminescence that the minority carrier lifetime of Zn(O,S) buffered solar cells is dependent on the sulfur content of the buffer layer. τ1 for devices with [O]:[S] of 1:0-4:1 are <10 ns, indicating efficient charge separation in devices with low sulfur content. An additional τ2 is observed for relaxed devices with [O]:[S] of 2:1 and both relaxed and light soaked devices with [O]:[S] of 1:1. Corroborated with one-dimensional electronic band structure simulation results, we attribute this additional decay lifetime to radiative recombination in the absorber due to excessive acceptor-type defects in sulfur-rich Zn(O,S) buffer layer that causes a buildup in interface-barrier for charge transport. A light soaking step shortens the carrier lifetime for the moderately sulfur-rich 2:1 device when excess acceptors are passivated in the buffer, reducing the crossover in the dark and illuminated I-V curves. However, when a high concentration of excess acceptors exist in the buffer and cannot be passivated by light soaking, as with the sulfur-rich 1:1 device, then cell efficiency of the device will remain low. © 2016 AIP Publishing LLC.

Pietzcker T.,Hochschule Ulm | Von Baum H.,Universitatsklinikum Ulm
Hygiene + Medizin | Year: 2014

Everyday life can no longer be imagined without watching movies. We chose 10 movies thematizing several topics of hospital hygiene and infection control procedures: personal hygiene (hand and skin hygiene), medical devices, food hygiene standards, nosocomial infections and outbreaks.

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