zhaw icp research report 2009

School of Engineering

ICP Institute ofComputational Physics

Zürcher Fachhochschule www.zhaw.ch

Research Report 2009

Das Titelbild zeigt eine dreidimensionale optische Finite-Elemente Simulation einer Leuchtdiode mit strukturier-ter Oberflache, die ihr Licht in den freien Raum ab-strahlt. Mit Hilfe von detaillierten numerischen Simulatio-nen untersucht das ICP, zu welchem Grade sich Abstrahl-charakteristik und Effizienz von Leuchtdioden durch denEinsatz von mikroskopischen Oberflachenstrukturen, bei-spielsweise Pyramiden, verbessern lassen.

The title graphic shows a three-dimensional finite elementoptical simulation of a light-emitting diode with a texturedsurface radiating into free space. Based on full-wave nu-merical simulations the ICP investigates to which extentthe radiation characteristics and optical efficiency of suchdevices can be improved by applying various surface tex-tures such as micro-pyramids.

Contents

1 Einleitung 5

2 Introduction 7

3 Sensors and Actuators 93.1 Numerical modeling of anisotropic plastic deep-drawing . . . . . . . . . . . . . . . . 103.2 Beruhrungslose Schichtcharakterisierung

durch Hochgeschwindigkeits-Infrarotsensorik . . . . . . . . . . . . . . . . . . . . . . 113.3 Velocimetry in railcars by a run-time measurement of thermal markers . . . . . . . . 123.4 Automatic mesh generation based on

geometrical and mathematical algorithms . . . . . . . . . . . . . . . . . . . . . . . . 13

4 Electrochemical Cells and Energy Systems 154.1 Status of model based investigation of PEM fuel cell performance . . . . . . . . . . . 164.2 Development and application of a electrode micromodel to optimize performance

and to predict degradation phenomena in mixed conductors Ni-YSZ anodes . . . . . 174.3 Status of numerical simulation for the development of a SOFC system . . . . . . . . 184.4 Feasibility of a portable SOFC for Hilti’s mobile machine tools . . . . . . . . . . . . . 194.5 Time-dependent analysis of Hexis 5-cell stack (U,i)-data to predict degradation be-

havior on the stack level and for natural gas as fuel . . . . . . . . . . . . . . . . . . . 204.6 Modeling of fixed-bed wood gasifiers for combined heat and power applications . . . 21

5 Organic Electronics and Photovoltaics 235.1 Advanced experimentally validated integrated OLED model . . . . . . . . . . . . . . 245.2 Efficient areal organic solar cells via printing . . . . . . . . . . . . . . . . . . . . . . . 255.3 Cost efficient thin film photovoltaics for future electricity generation . . . . . . . . . . 265.4 Three-dimensional full-wave optical simulation of light - emitting diodes . . . . . . . 275.5 Modeling, simulation and loss analysis of dye-sensitized solar cells . . . . . . . . . . 285.6 Optoelectronic research laboratory . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295.7 Organic electroluminescent pictograms for push-button applications . . . . . . . . . 30

6 Student Projects 316.1 Characterization of optically pulsed solar cells . . . . . . . . . . . . . . . . . . . . . . 326.2 Transient measurement of electroluminescence in organic light-emitting devices . . 336.3 Analysis of the emission profile in organic light-emitting devices . . . . . . . . . . . . 346.4 Benchmarking of optoelectronic device simulations with SETFOS . . . . . . . . . . . 356.5 High Performance Grating Spectrometer . . . . . . . . . . . . . . . . . . . . . . . . . 366.6 Reflectometer with algorithm for refractive index extraction . . . . . . . . . . . . . . . 376.7 Motorisiertes Reflektometer zur optischen

Charakterisierung von Dunnschichtsystemen . . . . . . . . . . . . . . . . . . . . . . 386.8 Innovative Schichtcharakterisierung mit

Hochgeschwindigkeits-Infrarot-Sensorik . . . . . . . . . . . . . . . . . . . . . . . . . 396.9 Aufbau und Inbetriebnahme eines Experimental - Holzvergasers . . . . . . . . . . . 40

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6.10 Optimierung eines Prufstands fur thermomechanischeBelastungstests von Hochtemperatur-Brennstoffzellen . . . . . . . . . . . . . . . . . 41

7 Appendix 437.1 Scientific Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447.2 News Articles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447.3 Conferences and Workshops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447.4 Prizes and Awards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457.5 Teaching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467.6 ICP Team Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477.7 Location and Contact Info . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

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Research Report 2009 ICP Institute of Computational Physics

Kapitel 1

Einleitung

Im Jahr 2009 wurden wir am Institute of Computational Physics unserem Namen erneut gerecht.Wir bearbeiteten verschiedenste Forschungsprojekte im Bereich der numerischen Modellierungvon Multiphysik-Systemen und durften in unserer Forschungstatigkeit viele spannende Heraus-forderungen zusammen mit unseren Industrie- und Hochschulpartnern meistern. Wie Sie diesemBericht entnehmen konnen, haben wir im Jahr 2009 in 16 Projekten mit nicht weniger als 37 exter-nen Forschungspartnern zusammengearbeitet.An der Schnittstelle zwischen akademischer und angewandter Forschung sehen wir uns taglichneuen Herausforderungen gegenuber. Wie konnen wir mit unseren Modellen und Simulationenfur unsere Forschungspartner einen Mehrwert schaffen? Die Antwort ist vielschichtig. Zum einenmussen wir das Vertrauen unseres Partners gewinnen und zeigen, dass wir mit unseren Berech-nungen Erkenntnisse erzielen, welche allein durch experimentelle Untersuchungen nur schwierigzu erreichen sind. Andererseits mussen wir auch uberzeugend darlegen, dass wir numerische Si-mulationen nicht nur unserem Handwerk zuliebe durchfuhren, sondern im Sinne der Projektzieleoptimal einsetzen. Eine Zusammenarbeit beginnt denn typischerweise auch mit einer umfang-reichen Analyse des vorhandenen Problems und der Bedurfnisse des Partners. Oft ist es dannwahrend der Zusammenarbeit zentral aufzuzeigen, wie unsere Simulationsresultate mit der Rea-litat verknupft sind. Dies erfolgt, indem wir z.B. mit Hilfe des Vergleichs zwischen Experiment undSimulation, Parameter bestimmen oder mit Simulationen Wege zur Verbesserung der Systemei-genschaften aufzeigen. Auch wenn die Verfugbarkeit von schnellen Rechnern und benutzerfreund-licher Simulationssoftware weiter steigt, stellen wir fest, dass dies alleine z.B. einem Industriein-genieur nicht genugt um eigenhandig mit Multiphysiksimulationen Fortschritte zu erzielen. In derRegel ist einschlagige Erfahrung in der Beschreibung physikalischer Phanomene auf verschie-denen Langenskalen unabdingbar. Es gibt zu viele Beispiele, bei denen in der Industrie oder ananderen Hochschulen Simulationssoftware beschafft wird, welche dann aufgrund von Schwierig-keiten in der Einarbeitung kaum weiter genutzt wird. Es gibt also viele Anzeichen dafur, dass wirauch in Zukunft als Partner attraktiv bleiben. Die Opportunitatskosten fur den Fall, dass man derSimulation als Entwicklungsmethode fern bleibt, steigen weiter an.Um diesen Leistungsauftrag zu erfullen, durfen wir auf finanzielle Unterstutzung von verschie-denen Forderagenturen und Forschungsstiftungen zahlen. Letztlich sind fur unsere Arbeit aberauch die Mitarbeiterinnen und Mitarbeiter zentral. Leider ist in der zweiten Halfte des vergangenenJahres unser Kollege und ICP Pionier Hansueli Schwarzenbach schwer erkrankt. Dies hat unserschuttert. Wir bewundern seine Offenheit gegenuber diesem Schicksal und wunschen ihm undseiner Familie viel Kraft.Im Jahr 2009 begrussten wir mehrere neue Mitarbeiter am ICP, welche unsere Kompetenzenverstarken. Mit Thomas Lanz ist erneut ein diplomierter ETH Physiker zu uns gestossen, welcheran unserem Institut eine Doktorarbeit absolviert. Unser Umfeld mit internationalen Forschungspart-nern und -Themen und der Status als wissenschaftliche Assistenten macht eine Dissertation ander ZHAW attraktiv. Wir schatzen diesbezuglich auch die Offenheit und Unterstutzung der involvier-ten ETH Professoren. Mit Dr. Rebekka Axthelm, Beat Odermatt und Dr. Martin Loeser sind zudemdrei wissenschaftliche Mitarbeiter zu uns gestossen. Es freut uns auch, dass wir im vergangenJahr gleich drei frisch diplomierte Bachelor of Science in Systems Engineering (Mechatronik) von

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ICP Institute of Computational Physics Research Report 2009

unserer Schule aufnehmen konnten. Es sind dies Kai Brossi, Martin Neukom und Adrian Gentsch.Die Attraktivitat einer Tatigkeit an unserer Schule bzw. unserem Institut wurde auch erhoht mitdem im Herbst 2008 lancierten Masterprogramm MSE (Master of Science in Engineering), dases den Master-Studenten ermoglicht, neben dem Unterrichtspensum in aktuellen Forschungspro-jekten mitzuarbeiten. Mit Benjamin Perucco schloss im Dezember 2009 der erste Master Studentunseres Instituts aber auch unserer Schule das MSE Studium ab.Im Bachelor Unterricht waren Dozenten unseres Instituts in Grundlagenmodulen zur Physik undMathematik in verschiedenen Studiengangen sowie in mehreren hohersemestrigen Modulen derStudiengange Mechatronik und Maschinentechnik tatig. Wir betreuten im vergangenen Jahr ins-gesamt knapp zehn Studentenprojekte und nahmen auch erstmals einen IAESTE Studenten ausBelgien fur ein Praktikum auf.Unsere Sichtbarkeit als Institut in der Schweiz haben wir im Jahr 2009 auch mit verschiedenenTeilnahmen an Messen und Tagungen gepflegt, so zum Beispiel auf nationaler Ebene an den zweiTagungen zu Nanotechnologie und Organischer Elektronik, welche wir in Zusammenarbeit mit demVerband Electrosuisse an der ZHAW organisierten. Am lokalen Anlass zum nationalen Tag derTechnik mit dem Thema erneuerbare Energien sprach ich zum Thema Forschung an Solarzellender nachsten Generation und an der Nacht der Technik referierte Nils Reinke uber Lichtquellender Zukunft. International trugen wir letztjahrig an Tagungen in Spanien, Italien, Osterreich undDeutschland bei. Eine ausfuhrliche Liste von Vortragen, Publikationen etc. im vergangenen Jahrentnehmen Sie dem Anhang.Nennenswert ist auch der weitere Ausbau des Mess- und Validierungslabors am ICP (kurz ”OLAB”)unter der Leitung von Nils Reinke. Es wird in neu bezogenen Raumlichkeiten im benachbartenLaborgebaude weitergefuhrt. Dank diesem Labor konnen wir vermehrt eigene Messungen zurValidierung von Simulationsresultaten ausfuhren oder sogar einen Beitrag in der Entwicklung vonMesstechnik und Sensorik allgemein leisten. Letztlich ist dieses Labor auch bestens geeignet umStudentenarbeiten auf Stufe Bachelor und Master im Bereich Mechatronik, Elektrotechnik undInformatik auszufuhren.An dieser Stelle mochte ich im Namen des ICP Teams der School of Engineering der ZHAWsowie dem Kanton Zurich fur die Unterstutzung und insbesondere unseren Forderagenturen fur dieerfolgreiche Zusammenarbeit danken. Ich freue mich, die eingangs genannten Herausforderungengemeinsam im ICP Team anzupacken und mochte mich bei jedem einzelnen ICP Mitglied fur denpersonlichen Einsatz im vergangenen Jahr bedanken.

Nun wunsche ich Ihnen eine spannende Lekture.

Beat RuhstallerInstitutsleiter

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Chapter 2

Introduction

In 2009 the Institute of Computational Physics again lived up to its name: We carried out numerousresearch projects in the field of numerical modeling of multiphysics systems and enjoyed tacklingmany challenges in our R&D activities together with academic and industrial partners. As you canread in the following, we collaborated with some 16 projects and as many as 37 external researchpartners.At the boundary between academic and applied research we are facing many challenges on adaily basis. How can we generate value to our research partners with our numerical models andsimulations? The answer is not straightforward. On the one hand we must earn the trust of ourpartners and demonstrate that our calculations indeed help gaining insights which could hardlybe obtained by experimental means. On the other hand we must explain convincingly, that wedo not perform numerical simulations just for the fun of it but rather because they are the mostefficient way of achieving the objectives. Thus a collaboration typically starts with an analysis ofthe problems at hand and the needs of the partners. Generally it is crucial to demonstrate how thesimulation results are connected to reality. This happens with the help of comparisons betweenexperiment and simulation, parameter extraction or by formulating possible ways of improvementof the system properties. Although the availability of fast computers and user-friendly simulationsoftware is further advancing, we can state that this alone won’t allow an engineer to get up tospeed with multiphysics simulations. In general, appropriate experience is indispensable. Thereexist too many examples of simulation software purchases in industry and at universities, in whichthe software is hardly used any longer after initial training difficulties. Thus there are numeroussigns that we will remain attractive partners also in the future. The opportunity cost for the case inwhich simulation software is not taken advantage of is large.In order to fulfill our mission we count on financial support of various research funding agencies.But after all, our staff members are crucial. Unfortunately, our colleague and ICP pioneer HansueliSchwarzenbach is suffering a severe illness since the end of last summer. We are very sad aboutthis but admire his way of facing this destiny and wish him and his family all the best.In 2009 we welcomed several new staff members which strengthen our competences. ThomasLanz is a physics graduate from ETH that joined us and is writing a Ph.D. thesis at our institute.Our work environment with international research partners and topics and the status as scientificassistant makes a Ph.D. thesis at the ZHAW attractive. We are grateful for the openness and sup-port of the involved ETH professors. In addition, three research associates, namely Dr. RebekkaAxthelm, Beat Odermatt and Dr. Martin Loeser joined the ICP. We are happy that we recruitedthree Bachelors of Science in Systems Engineering (Mechatronics) from our own school of engi-neering. Their names are Kai Brossi, Martin Neukom and Adrian Gentsch. The attractivity of theworking environment at our school and institute was increased also with the launch of the Master ofScience in Engineering (MSE) program in Fall 2008. It allows the students to get practical trainingin research projects besides attending classes. Benjamin Perucco in December 2009 was the firstMSE master student of our institute and our school (!) to graduate with an MSE Master of Sciencedegree.At bachelor level our lecturers of the ICP were teaching entry-level courses in physics and math-ematics in several degree programs as well as higher-level courses in in mechatronics and me-

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chanical engineering. We coached a total of almost ten student projects last year and for the firsttime welcomed an IAESTE student from Belgium.The visibility of our institute was maintained with the attendance of various conferences and sym-posia in 2009. For instance at national level we organized the two conferences on Nanotechnologyand Organic Electronics in collaboratoin with the Electrosuisse association. At the local event ofthe national day of technology with its focus on renewable energy I gave a presentation on researchon next generation solar cells. Nils Reinke spoke about light sources of the future at the ”Nachtder Technik” event of our School of Engineering. Internationally, we contributed to conferencesin Spain, Italy, Austria and Germany. A detailed list of talks, publications etc. is provided in theappendix.Please note the further extension of our laboratory for measurement and validation lead by NilsReinke. It moved to a new location in the neighboring laboratory building. Thanks to this laboratorywe are able to carry out some of the measurements for validation of the simulation results onour own. We may even contribute to the development of suitable measurement techniques andsensors in general. This laboratory is also ideally suited for student thesis projects at bachelor andmaster level in the fields of mechatronics, electrical engineering and computational science.On behalf of the ICP team I would like to express our gratitute to the School of Engineering andthe Canton of Zurich for supporting us and the research funding agencies for the successful col-laboration. I am looking forward to tackle the above-mentioned challenges together with our teamand would like to thank each ICP team member for her/his commitment in 2009.

Enjoy reading this report!

Beat RuhstallerHead of the institute

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Chapter 3

Sensors and Actuators

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3.1 Numerical modeling of anisotropic plastic deep-drawing

Contributors: Guido Sartoris

Partners: Alcan Technology and Management AGFunding: Commission for Technology and Innovation (CTI)Duration: 2008–2009

Modern laminates for the production of pharma-ceutical blisters have a complex inner structure.Several layers of different plastic and aluminasheets of thickness between 5 − 100 µm arepacked, stacked and glued together with the in-tent to provide the best environmental protec-tion from external agents. When forming theblisters by deep-drawing, the overall functionalrole of the layers in the original laminate shouldbe preserved and no holes, cracks or layer de-lamination are allowed to evolve during defor-mation. One may try to get physical insight onthe disruptive processes of the sandwiched lay-ers by running complex, time-consuming exper-iments, but they do not necessarily yield ulti-mate and correct answers on the causes of fail-ure. Therefore a numerical approach to lami-nate deep-drawing is almost a necessity and nu-merical modeling is expected to provide a bet-ter and more detailed insight of the deformationprocesses with respect to a solely experimentalapproach.From the numerical point of view, the major con-cern is the correct description of the anisotropicelasto-plastic behavior at large strains. The the-ory of anisotropic plasticity at finite strain hasnot yet reached full acceptance and an ultimatemodel is not yet established. This is in opposi-tion to the isotropic case, where valid numericalmodels are available and ready to be used. Forour case of orthotropic plasticity, we have cho-sen to use the more physically sounded multi-plicative approach of plasticity instead of the ad-ditive one, which, however, is numerically moreexpensive. In general, by requiring fully spa-tial covariance of the material laws, one just de-rives isotropic laws, so that to handle anisotropiceffects, one needs to add some tensorial de-pendencies representing privileged crystal di-rections. The problem is for a given physicalsituation to identify these structural tensors, butthen we can apply well known theorems on therepresentation of isotropic tensor functions toderive anisotropic material laws depending ona limited number of scalar invariants. For or-thotropy which is assumed here, the structuraltensor is known to be a symmetric 2nd ordertensor. With some additional assumptions on

the physical processes involved, e.g. incom-pressibility condition of the plastic flow, one canshown the dependency of the elastic law to befrom nine invariants and that of the yield functionto be from seven ones. These invariants mustbe combined together to form functions depend-ing on constant material parameters which needto be fitted from experimental data.In general, it is not a simple task to fit these ma-terial parameters since we can have quite someparameters and a large sensitivity. One maythink to proceed automatically with some opti-mization algorithms, however, because of thelarge sensitivity, these functionals may have alot of local minima and the optimum or even anacceptable solution can be hard to find. There-fore, for the initial phase, we have opted for athree steps manual approach with a low numberof material parameters. As first one fits the elas-tic behavior, then the yield function at the onsetof plasticity and as least the hardening functionduring plastic flow. In general, there is a lowsensitivity with respect to the elastic coefficientsand a high one for the plastic ones.The next figure shows uniaxial stress-strain re-lations for an OPA specimen in a logarithmicscale together with fitted curves. Several stripshave been cut at increasing angles of 15 de-grees. One clearly can observe sharp transi-tions between elastic and plastic behavior, theorthotropic behavior and good fitting character-istics.

Fig.1 Fitted stress-strain relations for an OPA speci-men.

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3.2 Beruhrungslose Schichtcharakterisierungdurch Hochgeschwindigkeits-Infrarotsensorik

Contributors: Nils A. Reinke, Kai A. Brossi, Remo Ritzmann, Andor Bariska (IDP)

Partners: Flo-IR und weitere 5 IndustriepartnerFunding: Kommission fur Technologie und Innovation (KTI)Duration: 2007 – 2009

Die beruhrungs- und zerstorungsfreie Cha-rakterisierung von Schichtsystemen auf nicht-metallischen Substraten wie Kunststoffen undKeramiken ist ein kaum gelostes Messproblemder Industrie. Die School of Engineering (SoE)der Zurcher Hochschule fur Angewandte Wis-senschaften (ZHAW) und die Firma Flo-IR ent-wickeln ein Messverfahren, welches die Cha-rakterisierung von Mehrschichtsystemen durchHochgeschwindigkeits-Infrarotsensorik erlaubt.Dazu gehoren die Bestimmung von Schichtdi-cken, thermophysikalischer Parameter, chemi-schen Zusammensetzungen der Schichten so-wie das Erkennen von Haftungsproblemen.

Fig. 1 Messprinzip

Im vorgestellten Messverfahren wird dieuntersuchte Probe pulsartig durch einenLichtblitz aufgeheizt und das zeitliche Ver-halten der Oberflachentemperatur mit ei-nem Hochgeschwindigkeits-Infrarotsensor ge-messen. Das zeitliche Verhalten der Ober-flachentemperatur wird durch die Filmdicke, dieAbsorptivitat sowie die Warmeleitfahigkeit dereinzelnen Schichten dominiert. Das Absorpti-onsverhalten und das thermische Verhalten desgesamten Schichtsystems werden mathema-tisch beschrieben. Aus dem ermittelten Verlaufder Oberflachentemperatur werden numerischdie physikalischen Parameter des zugrunde lie-genden Schichtsystems bestimmt.

Fig. 2 Prototyp I

Das vorgestellte Messsystem bestimmt Schicht-dicken in vier nebeneinanderliegenden Punk-ten von je vier Quadratmillimetern Grosse. Eslassen sich Schichtdicken im Bereich von 5µm bis hin zu einigen 1000 µm bestimmen.Die Messqualitat ist unempfindlich gegenuberVerkippung und eignet sich damit auch furunformige Messobjekte. Die Messdauer betragtje nach Art der Beschichtung etwa 40 ms bis400 ms. Die Genauigkeit der Messung ver-bessert sich mit zunehmendem Kontrast zwi-schen den thermophysikalischen Parameternder einzelnen Schichten des Messobjekts. DasMessverfahren wurde bereits erfolgreich fur un-terschiedliche Lack- und Pulverbeschichtungenauf Kunststoff-, Metall- und Holzsubstraten ge-testet.

Fig. 3 Beschichtete Holzprobe

An der School of Engineering arbeiten das Insti-tute of Computational Physics (ICP) und das In-stitut fur Datenanalyse und Prozessdesign (IDP)gemeinsam an der Entwicklung des Messproto-typen und der statistischen Signalanalyse.

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3.3 Velocimetry in railcars by a run-time measurement of ther-mal markers

Contributors: Nils A. Reinke, Beat Odermatt, Andor Bariska

Partners: Siemens Transportation SystemsFunding: Commission for Technology and Innovation (CTI)Duration: 2008 – 2009

State-of-the-art velocimetry for transportationsystems using the Doppler method, dynamic im-age analysis and global positioning systems suf-fers from unreliabilities to a greater or lesser ex-tent. This disaffection arises from a liability tointerference towards environmental influences.Leaves, snowfall, rainfall and artificial lighting(light pollution) may lead to severe distortions inthe measured velocity.This feasibility project verifies a patent pend-ing velocimetry technique which is based ona run-time measurement of thermal markers.The thermal-marker is applied from the railcarby optical excitation and subsequently photo-thermally detectation by an infrared sensor. Thevelocity of the railcar can be determined by mea-suring the run-time from excitation to detectionand the spatial distance between excitation anddetection setup.

Fig. 1: Corroded steel disc spinning behind the ger-manium zoom lens of the infrared detector

In recent years significant progress has beenmade in developing powerful, compact and in-expensive solid-state lasers. Nowadays, solid-

state lasers replace traditional gas-lasers due totheir higher reliability and low maintenance cost.At the same time, fast and inexpensive sensorsfor the mid-infrared regime (MIR) become moreand more available. Improvements in laser tech-nique and MIR sensors enable this innovativevelocimetry technique.This project includes three sequential steps:

• Computational modeling for estimating theamount of light necessary to deposit thethermal marker with different optical exci-tation sources (Laser, LED, flashlamps).The optical deposition of the thermalmarker leads to a transient temperaturedistribution inside the rail. In order to de-tect the deposited thermal marker by theinfra-red sensor, the amplitude of this tem-perature distribution has to be sufficientlyhigh.

• An experimental setup has to be devel-oped from scratch. This experimentalsetup has to reflect conditions close to re-ality, e.g. the optical and thermal proper-ties of the rail. Computational modelingwill help to specify the individual compo-nents used in this experiment. The exper-imental setup will be controlled and dataacquired by LabView.

• In a final step of the project test measure-ments will be performed and analyzed toverify results from computational simula-tions and to proof the concept of the pend-ing patent.

A prototype experimental setup comprising a fix-ture for a spinning steel disc and an infra-reddetector is shown in fig. 1. Results of this feasi-bility project will be further investigated in a fieldtest, if the third step turns out to be successful.

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3.4 Automatic mesh generation based ongeometrical and mathematical algorithms

Contributors: M. Robbiani, H. Schwarzenbach, G. Sartoris, M. Roos

Partners: ZAMP, Numerical Modeling GmbHFunding: Gebert Ruef StiftungDuration: 2009–2010

A key element of the numerical solution of par-tial differential equations (PDE) by the finite el-ement method in a multidimensional domain isthe generation of the computational grid. Sincethe characteristics of the grid crucially influ-ences the quality and the efficiency of the nu-merical solution, the success of modeling phys-ical processes is closely linked to the develop-ment procedures for generating suitable grids.It is therefore not surprising that grid generationis a rapidly growing autonomously mathemati-cal discipline of applied mathematics. Generallythe development of techniques for mesh gener-ation lags behind the techniques for discretizingthe PDEs and so is often the lack of experiencein constructing the grid which prevents the opti-mal numerical solution of PDEs. When solvinga system of three-dimensional nonlinear PDEson a domain of complex geometry - a frequenttask in today’s engineering life - the effort nec-essary to construct the computational grid, canby far dominate the remaining task of computingthe numerical solution. The starting position be-comes even more demanding if the geometry ofthe computational domain changes dynamicallyduring the simulation. As techniques for flex-ible, robust and efficient dynamic grid genera-tion are still missing, an effort in the engineeringcommunity is underway to overcome these dif-ficulties. For the FE-simulation of e.g. thermo-, electro- or fluid-dynamic processes there aretwo main approaches for grid generation: geom-etry import from CAD tools, with subsequent au-tomatic mesh generation or algebraic and func-tional grid construction from simple domainsmapped and combined together to form the realgeometry. The simplicity of the first apporach al-lows the treatment of complex geometries withlittle user interaction but it is counterbalanced bythe fact that unnecessarily large grids are cre-ated. The second approach is time consuming

and requires quite a bit of skills to discover ap-propriate maps but has an inherent mathemat-ical description enabling easy variations of thegeometry and a better control of the numeri-cal error. The AutoGrid project aims to developnew methods for algebraic automatic grid gen-eration which are relevant to practical applica-tions. The actual practical limitations of the al-gebraic approach should be explored and newtheoretical methods investigated, validated andimplemented in efficient algorithms ready to beused in real engineering problems. Likewise anopen-source version of the project for the 2Dcase should be made available to a wider audi-ence. AutoGrid is a project of the newly foundedCenter of Mathematics and Physics (ZAMP) incollaboration with the Institute of ComputationalPhysics (ICP) and the industrial partner Numer-ical Modeling GmbH.

Fig. 1 Algebraic mesh adaption.

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Chapter 4

Electrochemical Cells and EnergySystems

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4.1 Status of model based investigation of PEM fuel cell per-formance

Contributors: Yasser Safa, Jurgen O. Schumacher, Felix N. Buchi

Partners: Paul Scherrer Institute PSI (Villigen, Switzerland)Funding: Swiss Federal Office of Energy SFOEDuration: 2007-2010

The principle of Proton Exchange MembraneFuel Cell (PEMFC) as an energy producer isbased on the electro-chemical reaction betweenan anodic fuel (mainly hydrogen) and a ca-thodic gas containing oxygen. This gives riseto a vapor condensation phenomenon whereliquid water may affect the transport propertiesin the porous Gas Diffusion Layer (GDL) of thePEMFC. An accurate numerical prediction of thewater distribution is thus of great importance inorder to provide a guideline design of a reliablePEMFC.Our ICP’s contribution to the ongoing efforts inthis technology is the advanced study of thetwo phase flow in the porous GDL with focuson modelling, numerical code programing andindustrial test cases simulations. The so calledMulti-Phase Mixture Model (M2) is adopted todescribe the two-phase flow. An important fea-ture of M2 is its usability in the domain wheresingle and double-phase zones coexist.In order to account for the momentum evolutioncaused by the water phase changing we sug-gest a new approach for an advanced use ofthe M2 concept without violating the momen-tum conservation (Fig. 1). We have to find theglobal velocity, the global pressure, and the liq-uid water saturation (u, p, s`) such that

u = −κλ∇p,∇ · u = fa

ρa+ f`

ρ`,

φ∂s`

∂t +∇ ·(q` G(u,∇pc) + κλaq`∇pc

)= f`

ρ`,

1 where G(u,∇pc) is a corrected global veloc-ity, and q` and q` are corrected fractional flowrates of water. This correction reflects the mo-mentum exchange between the two phases ofwater. Material parameters of the GDL are theabsolute permeability κ, the global mobility ofwater λ(s`), and the porosity φ. Here, λa(s`)is the mobility of the air phase. fa and f` aresource terms that are determined by the evapo-ration and condensation rates of water.The numerical methods used for solving the

system of equations were implemented in Math-ematica. A degeneracy in the transport problem

Fig. 1 Simulations with relatively high Evaporation-Condensation Rates and relatively high permeability

Fig. 2 Dynamic simulation result for the GDL.

is treated by perturbating the diffusive coeffi-cient to obtain a non-degenerate problem. Thesaturation equation is solved by a stabilizedGalerkin approximation (SUPG) and the Darcyproblem is solved by a stabilized mixed finite el-ement method (GLS). The time discretization isachieved by a semi-implicit scheme. Since thetime-scale of the total flow is longer than that ofthe water saturation evolution, a multi-time stepdiscretization is introduced.A dynamic simulation result for the GDL mate-rial “E-Tek Cloth A” is shown in Fig. 2. A lineartime-sweeping of the electrical current density(0.05 A

cm2 s ) was used as simulation input. Anasymmetric profile of the average liquid watersaturation is observed that is due to a trans-port limitation of the water through the porousGDL. Liquid water saturation profiles of differ-ent GDL material types are investigated in thisstudy, both, as a function of time and space.

1Incompressible liquid phase has been assumed. The terms ∂p∂t

and ua.∇ρa have been neglected

ZHAW 16


4.2 Development and application of a electrode micromodel tooptimize performance and to predict degradation phenom-ena in mixed conductors Ni-YSZ anodes

Contributors: Thomas Hocker

Partners: Boris Iwanschitz, Andreas Mai, Hexis AG and several Swiss partners.Funding: SOF-CH, SwissElectric Research, Swiss Federal Office of EnergyDuration: 2008 – 2010

The development of a FE-based electrodemodel that mimics the real 3D microstructure ofmixed conducting electrodes has been finished.It is especially suited for investigating the impactof microstructure on electrode performance anddegradation. For example, it allows one to as-sess the effect of experimentally obtained singledegradation phenomena such as particle coars-ening and electrode poisoning on the electrodeperformance. Since the electrode model is di-rectly linked with a repeat unit model (a com-plete cell plus current collectors on both sides)it predicts the impact of electrode degradationon the repeat unit performance.

Fig. 1 FE-based microstructure model of a mixed-conducting Ni/YSZ-anode. The electrode model islinked to local cell as well as repeat unit models.

To mimic realistic solid-phase networks, up toeight different particle sizes can now be speci-fied for each solid phase. Furthermore, the limit-ing effect of sinter necks on the ion and electrontransport is taken into account via contact re-sistances between neighboring particles. Whencompared with literature data, the electrodemodel exhibits all main observations knownfrom experimental analyses. Comparisons havebeen made with common electrode character-istics discussed in the following review-article:S. Sunde, ”Simulations of Composite Electrodesin Fuel Cells”, Journal of Electroceramics, 5, pp.153-–182, 2000. The model has been validatedagainst conductivity- and EIS-data at Hexis.

Fig. 1 gives an overview about the developedmodeling framework that spans from a finite el-ement model to resolve the microstructure of anelectrode up to a continuum model for a repeatunit, i. e. a complete cell with nonhomogeneouselectrical current collection. Fig. 2 shows resultsof a finite-element model of two adjacent elec-trode particles, both of cylindrical shape. Due tothe sintering process, the two particles are de-formed and form a more or less narrow sinterneck. During this process the particle volumesare preserved. This ”two-particle model” inves-tigates limitations in the charge transport for dif-ferent sintering scenarios. With narrow sinternecks (see right picture in Fig. 2), the drop ofthe electrical potential happens over a short dis-tance in the vicinity of the sinter neck. Underthose conditions the sinter neck becomes limit-ing for the overall charge transport.The model allows one to calculate effective con-ductivities that account for limited charge trans-port by sinter necks. These effective conductiv-ities are then used in the microstructure modelof a complete electrode, see Fig. 1.

Fig. 2 Rotational-symmetric FE-model of two adja-cent particles of cylindrical shape to investigate thelimitation of sinter necks on the charge transport. Thecolors indicate electrical potentials that go from high(yellow) to low (black) values.

17 ZHAW


4.3 Status of numerical simulation for the development of aSOFC system

Contributors: Yasser Safa, Thomas Hocker

Partners: Hexis AG (Winterthur), EPFL (Industrial Energy Systems Laboratory)Funding: Swiss Federal Office of Energy SFOE, SwissElectric ResearchDuration: 2007–2010

The concept of SOFC heater “Galileo System”,established by Hexis AG, is devoted to coverthe essential power and heat requirement fora representative Central European single-familyhome. In this project we develop an advancedcomputational reactive flow model of the cou-pled transport phenomena in SOFC. The phys-ical model that we study is governed by a sys-tem of nonlinear partial differential equations de-scribing the conservation law for mass, charge,energy and species. The fluid flow in theporous media is described by Darcy Law. Toreduce the computing time without losing con-sistency certain geometric restrictions are as-sumed. For example a low aspect ratio existsbetween the thickness and the cross-section ofthe cell. Therefore, the cell is treated in one di-mension only and is coupled with the flow in-side the gas channels. A slip boundary condi-tion appears on the surface which constitutesthe contour of a porous body through which thefluid flow also takes place. In several known ap-proaches the slip velocity is taken as a a pri-ori known quantity and it usually serves as aboundary condition to solve the momentum con-servation equation like Navier-Stokes. The limi-tation of those approaches is that slip conditionsare most frequently estimated in an empiricalway and do not necessarily correspond to allreal situations. A simultaneous solution of theequations describing the flow in both media iscarried out. At the interface the slip velocity isconsidered as an arbitrary quantity not known apriory and which can be determined by match-ing the shear stresses on the porous wall of thechannel. As presented in Fig. 1 we start solv-ing the 1D Channel problem on the center level.The boundary values are used to update thoseon the boundary of the channel-electrode inter-face. Then we solve the 1D Channel problem atthe porous wall level and the obtained value isused as Dirichlet boundary condition for the 1DCell problem.

Fig. 1: Iterative solving 1+1D cell-channels moddel

Fig. 2: Oxygen Concentration in the Air Channel

Fig. 3: Oxygen Concentration in the Cathod

In a new iterative step, we solve the cell prob-lem and the outer species flux is applied as asource term for the 1D Channel on the centrallevel. Note that in each step the species flowsare computed in both the anodic and the ca-thodic gas channels.

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4.4 Feasibility of a portable SOFC for Hilti’s mobile machinetools

Contributors: Roman Gmur, Christoph Meier, Thomas Hocker

Partners: ETH Gauckler group, Hilti Corporation, Schaan.Funding: Direct funding by Hilti CorporationDuration: 2008 – 2010

Solid oxide fuel cell (SOFC) systems operate attemperatures between 700 ◦C and 900 ◦C. Theyare typically designed for stationary combinedheat and power (CHP) applications in the smallto medium power ranges, i. e. from about 1 kWup to several MWs. However, due to their po-tential for high power densities and their toler-ance for different hydrocarbon fuels, SOFC sys-tems were recently proposed for portable appli-cations with electrical outputs from about 20 Wto 250 W. The fabrication of the SOFC mem-branes used in these systems is usually basedon classical thick film processing such as tapecasting or screen printing which results in mem-brane thicknesses of several tenths of a millime-ter. Driven by the progress in thin film technol-ogy, micro-fabrication and micro-packaging, theconcept of a so-called micro-SOFC (µ-SOFC)has been recently investigated. In contrast toconventional SOFCs, µ-SOFCs are character-ized by membrane thicknesses of only a few mi-crometers and operation temperatures as lowas 500 ◦C. Feasibility studies of such systemssuggest electrical power outputs as low as 1 W.µ-SOFCs could be employed in combinationwith or as replacement of batteries to powersmall electronic devices, such as laptop com-puters, portable digital assistants, camcorders,or industrial scanners. Compared to state-of-the-art energy storage devices such as Li-ionand NiMH batteries, up to ten times higher en-ergy densities (per volume or weight) were an-ticipated.The development of µ-SOFCs still is in researchstatus. To assess the potential of such mem-branes for commercial applications already atan early stage, simple, yet physically soundmodeling tools are required. Such tools needto incorporate all relevant system parametersincluding operation conditions, material proper-ties as well as basic features of the layouts ofthe various system components. We developedsuch a model and subsequently applied it to dif-ferent application scenarios. The model em-ploys the global conservation principles for thespecies masses, the electrical charges and theenergy for each system component. It allowsone to calculate the efficiency of the overall sys-

tem, its dimensions and weight. A schematicoverview of the ONEBAT R© µ-SOFC system isgiven in Fig. 1 and 2. Shown are the mass andenergy flows entering and leaving the system aswell as the internal heat sources. The core ofthe ONEBAT R© µ-SOFC system is the so-called”hot module“ which consists of the gas process-ing unit (GPU), the SOFC stack (Cells) and thepost combustion unit (PCU).

Fig. 1 Schematic of ONEBAT R© µSOFC with enteringand leaving mass flows.

Fig. 2 Schematic of ONEBAT R© µSOFC with enteringand leaving energy flows and internal heat sources.

19 ZHAW


4.5 Time-dependent analysis of Hexis 5-cell stack (U,i)-data topredict degradation behavior on the stack level and fornatural gas as fuel

Contributors: Markus Linder, Thomas Hocker

Partners: Roland Denzler, Andreas Mai, Hexis AG and several Swiss and EU-partners.Funding: AccelenT, Swiss Federal Office of EnergyDuration: 2009 – 2011

A simplified, Mathematica-based model toanalyze the current-voltage characteristics ofSOFC-stacks has been developed and is in reg-ular use at Hexis. The model predicts the start-ing performance for a large number of current-voltage stack data without the need for any fit-ting parameters. It has been used to studythe sensitivity of various input parameters suchas changes in mass-flows, fuel composition,temperature, and humidity. For the remainingproject year it shall be extended to the HexisGalileo system to perform model-based analy-sis of field tests. Here the goal is to explain un-usual system behavior that, for example, couldresult from composition changes in the naturalgas supply, and to assess long-term degrada-tion from the field test results. Furthermore, weplan to implement a statistics tool to automati-cally discriminate between reproducible and un-reproducible data. The prior will be used to as-sess long-term performances, the latter to in-vestigate phenomena not yet well understood.The model development is shared between theSOF-CH and the AccelenT-projects. The latterfocuses on methods to accelerate the testing ofSOFC stack performances and related degrada-tion phenomena.

Fig. 1 Typical area specific resistances as obtainedwith the Uj-Analyzer.

Fig. 1 shows a model-based analysis of ASR-values (ASR = Area-Specific Resistance) for afive-cell Hexis stack that runs on natural gas.The total resistance (ASRstack) has been ob-tained from five current-voltage curves. Thesimplified system model has been used to sub-divide the total resistance into a gas contributionthat accounts for the details of the reforming pro-cess and possible fuel leakages. The remain-ing losses are denoted as ASR RU they repre-sent the sum of the resistances of the repeatunit. They can be further subdivided into theohmic losses of the electrolyte and the polariza-tion losses of the anode and cathode.

Fig. 2 Time-dependent area-specific resistances asobtained with the Uj-Analyzer.

The difference between the repeat unit lossesand the sum of ASRohm and ASRpol is de-noted as ASR?. ASR? specifies all contribu-tions that are not explicitly accounted for by themodel. One sees from Fig. 2 that for the first700 hours of operation, ASR? remains constantand is rather small. However, after 700 hours,one or more degradation processes commenceto significantly reduce the stack performance.Note also that two cells show a degradation ratethat is different from that of the other three cells.This could be a temperature-effect, since evensmall differences in the operation temperature(say around 20◦C) have a rather large impacton the stack performance.

ZHAW 20


4.6 Modeling of fixed-bed wood gasifiers for combined heatand power applications

Contributors: Thomas Hocker, Christoph Meier

Partners: ITFE Institut fur Thermo- und Fluid-EngineeringFunding: GEBERT RUF STIFTUNGDuration: 2009–2011

Wood gasification is a thermo-chemical conver-sion of wood into a combustible gas. Due totheir simple design, fixed-bed reactors are oftenthe technology of choice for small range appli-cations up to 5 MWth. Several CHP pilot plantswith wood gas driven internal combustion en-gines went on grid throughout Europe during thelast decade. Since carbon monoxide and hy-drogen are the main contributors to the woodgas caloric value (typically 4 - 6 MJ/m3), andas the gasification takes place between 600 and1000◦C, solid oxide fuel cells are a potential al-ternative to combustion engines, promising re-markable high efficiencies for micro-CHP with arenewable fuel. The aim of our project is to de-velop a toolbox of flexible, application-orientedmodels to design and optimize fixed-bed gasi-fiers by combining known approaches with ob-servations from plant operators and own exper-iments. Key issues are the minimization of tarsin the produced gas and more flexibility towardswood modality. However, until now model baseddesign only plays a minor role for plant develop-ers and operators. To validate models and to

identify different gasification mechanisms a lab-oratory gasifier was built, suited to a wide rangeof operation conditions and fuels. Gas composi-tion, temperature and pressure distribution aremeasured on-line. Experiments with single par-ticles are conducted as well. Several types ofgasification models are under development, asshown in Figure 1. Combining thermal equi-librium calculations with energy and mass bal-ances, an overall model predicts the output gasspecies for a given input composition. This con-catenates e.g. wood moisture and stoichiomet-ric combustion coefficient λ with the process ef-ficiency. But since equilibrium achievement de-pends on the reactor design and operation con-ditions, the usability of this approach as predic-tive model is rather limited. Introducing reactionkinetics and single particle sub-models leads tomore comprehensive results. Thus, stage mod-els can predict e.g. the required dimensions forpyrolysis and char gasification zones consider-ing particle shape and size distribution. Furtherdevelopments are planned toward continuous,transient multiphase models.

Pyrolysis and Oxidation

Char Gasification

Wood Drying

Continuous ModelsOverall Model Stage Modeling

Moist Wood

Inert Char-Ash Woodgas and Char-Ash

Air and Biomass

Thermal Equilibrium

Input

Output

Operation

λ = 0.4λ = 0.3

λ = 0.5

η

86.2%73.8%61.4%

Pyrol.

CharGasif.

1m

2m

0m

Predicted Reactor Heights for Different Particle Shapes

Air andBiomass

Air

Woodgas and Char-Ash

600 1000°C

Gas Phase Temperature

Wood devolatilisation:→ C-O-H Gas Species → Charcoal, Tars

C + CO2 ↔ 2 COC + H2O ↔ CO + H2C + 2 H2 ↔ CH4

Fig. 1: Model Development and Process Overview.

21 ZHAW


ZHAW 22


Chapter 5

Organic Electronics andPhotovoltaics

23 ZHAW


5.1 Advanced experimentally validated integrated OLED model

Contributors: Evelyne Knapp, Beat Ruhstaller

Partners: Philips Research Aachen and Eindhoven, Technical University Dresden,University of Cambridge, University of Groningen, Eindhoven University of Technology,Sim4tec, Fluxim

Funding: EU FP7Duration: 2008 – 2011

Organic Light-Emitting Diodes (OLEDs) aresolid-state devices composed of thin films of or-ganic molecules that create light when a voltageis applied. They can be used for displays as wellas lighting. OLEDs are energy-efficient and verythin, and in fact can be put on flexible materials(plastic or metal foil) to make bendable displays.The European project AEVIOM aims at amore accurate physical and numerical de-scription of OLEDs. The developed modelshould be continuously validated with experi-ments and measurements. This is what AE-VIOM - Advanced Experimentally Validated In-tegrated OLED Model- stands for.So far, the basic concepts of OLED oper-ation -charge carrier injection, charge trans-port, exciton formation, radiative decay and lightextraction-as shown in Fig. 1 have been refinedand integrated in a second generation model.

Fig1.: Fundamental processes in the OLED opera-tion: electrons and holes are injected and transportedin the organic material until they form excitons. Thenthey decay and emit light.

The main difference to the first generation modelis that the disordered nature of organic semi-conductors is taken into account in terms of aGaussian density of states. This affects theabove mentioned fundamental processes. Anew description for the charge injection with bar-rier lowering, a density-, field- and temperature-dependent mobility (Extended Gaussian Disor-

der Model), the generalized Einstein relationand traps were obtained within AEVIOM andsimulated for disordered semiconductors.In the second year of the project, the disorder-enhanced physics has been added to the nu-merical solver of the ZHAW. This simulatorsolves the semiconductor equations consistingof the Poisson equation and the continuity equa-tions for electrons and holes in a coupled man-ner for transient and steady-state problems. Theresults have been cross-checked with other sim-ulation methods developed within the AEVIOMproject like the Monte Carlo, Master equationand Bonham-Jarvis approach and experimentaldata as shown in Fig. 2.

0 0.5 1 1.5

10−15

10−10

10−5

100

105

injection barrier ! [eV]

curre

nt d

ensi

ty J

[A/m

2 ]

EGDM (ZHAW)no image potential (ZHAW)3D master−equation model 1D continuum model (Bonham−Jarvis)1D continuum model (no im. pot., B−J)

Fig 2.:The current density depending on the injec-tion barrier is shown for different simulation methods.Also the effect of the image charge potential and theelectric field on the current density is displayed.

As a further way to validate models and their pa-rameters, the ZHAW has extended its solver toconduct a small-signal analysis. To study the acresponse of an OLED under small-signal condi-tions, the steady-state voltage V0 is modulatedwith a sinusoidal voltage of amplitude V ac andwith angular frequency ω: V = V0 + V aceiωt.The calculated impedance will be validated withmeasurements.

ZHAW 24


5.2 Efficient areal organic solar cells via printing

Contributors: M. T. Neukom, T. Lanz, N. A. Reinke, B. Ruhstaller

Partners: TU/e Eindhoven University of Technology (NL), University Jaume I (E), CSEM, BASFFunding: Swiss Federal Office of EnergyDuration: 2008 – 2011

This international research project with universi-ties and industry aims at creating more efficientand stable organic solar cells. The ICP is sim-ulation partner and provides a comprehensiveelectro-optical model to numerically character-ized organic solar cells.The electron and hole mobilities are essen-tial parameters that influence the cell efficiency.Measuring the mobilities accurately is thereforeimportant. The CELIV and photo-CELIV experi-ment is a established method to extract mobilityvalues of organic solar cells. The results areusually analysed with a simple analytical model.We use a comprehensive numerical model to in-vestigate the accuracy of this analytical modeland show the possibilities of the CELIV method.

0 2 4 6 8

−3

−2

−1

0

time (µs)

volta

ge (

V)

a

0 2 4 6 8

0

5

10

15

20

time (µs)

j (m

A/c

m2 )

b

Analytical formulaNumerical simulation

Fig. 1: (a) Applied voltage ramp. (b) Transient currentwith typical overshoot

In the CELIV technique (charge extraction withlinearly increasing voltage) charge carriers in-side of a solar cell are extracted with a triangu-lar voltage pulse. The transient current is anal-ysed and the mobility of the faster charge carrier

can be calculated with the position of the cur-rent peak according to Juska et al.1 In figure 1a voltage ramp and the corresponding currentof a typical CELIV experiment is shown. Dueto the linear increasing voltage a constant dis-placement offset occurs.

0 2 4 6 8 10

0

5

10

15

20

25

time (µs)

j (m

A/c

m2 )

MeasurementSimulation

Fig. 2: CELIV measurement and numerical simula-tion of an organic solar cell

In our numerical model we assume that incom-ing photons directly generate free charge car-riers inside the donor/acceptor blend. With adrift-diffusion model the charge transport insidethe cell is simulated. All models used are imple-mented in the software SETFOS that is devel-oped by the ICP spin-off Fluxim AG2. We simu-late the CELIV experiment and compare it withmeasurements as shown in figure 2. With ourcurrent model CELIV experiments can be repro-duced and device parameter can be extracted.We can show the accuracy and the limitations ofthe analytical formulas frequently used to anal-yse CELIV experiments. Because several ef-fects are neglected in the analytical model onlythe order of magnitude of the mobility value canbe determined. The numerical simulation offersa more accurate mobility determination. By fit-ting simulation to measured currents we showthat CELIV experiments can be reproduced withour numerical model. We also demonstrated thepossibility to extract minor and major mobilities.

1G. Juska, K. Arlauskas, M. Viliunas, J. Kocka, Phys. Rev. Lett. 84 (2000) 49462Semiconducting thin film optics simulator (SETFOS) by Fluxim AG, Switzerland (www.fluxim.ch)

25 ZHAW


5.3 Cost efficient thin film photovoltaics for future electricitygeneration

Contributors: Thomas Lanz, Nils A. Reinke, Beat Ruhstaller

Partners: EPFL, EMPA, PSI, Oerlikon Solar, Greatcell, Solaronix, FlisomFunding: SwissElectric ResearchDuration: 2007 – 2010

The extension of the optical model for arbitrarycombinations of coherent and incoherent layershas been completed. This now allows to treatthe light propagation in selected layers exclu-sively using the intensity. The extension is phys-ically motivated by the finite coherence length ofthe sunlight which is on the order of 1 µm. Lay-ers with a thickness that exceeds the coherencelength may be treated as incoherent, effectivelyreducing the interference fringes obtained in co-herent simulations that are not observable in theexperiment.

400 600 800 10000.0

0.2

0.4

0.6

0.8

1.0

Wavelength @nmD

Ab

sorb

ance

Total

i a-Si

Al

Fig. 1: Layer absorbances for an a-Si:H solar cell cal-culated with the extended transfer-matrix formalism.The glass and the aluminum layer are treated as in-coherent.

Figures 1 and 2 illustrate the use of incoher-ence in the optical simulation of an a-Si:H so-lar cell. As the cover glass layer has a thick-ness of 1 mm it is treated as incoherent in bothcases. The interference effects observed in thelayer absorbances in Figure 1 in the wavelengthrage from 600 to 1000 nm can be attributed tointernal reflections in the intrinsic a-Si:H layer.Scattering of the light caused by rough layer in-terfaces may cause some of the interference ef-fects to average out. Measurements from cellsthat are built using textured substrates show sig-nificantly less interference effects. This may bereproduced by introducing incoherence in thesimulation of these devices. Figure 2 illustratesthe layer absorbances for the same device asin Figure 1 but with an incoherent intrinsic ab-sorber layer.

400 600 800 10000.0

0.2

0.4

0.6

0.8

1.0

Wavelength @nmDA

bso

rban

ce

Total

i a-Si

Al

ITO

p a-Si

Fig. 2: Layer absorbances for an a-Si:H solar cell cal-culated with the extended transfer-matrix formalism.The glass, the aluminum and the intrinsic layer aretreated as incoherent.

Scattering at rough layer interfaces is employedin thin film silicon solar cells to increase the ab-sorption by prolonging the optical path in theabsorbing layers. Even though the suppres-sion of interference effects caused by scatter-ing can be reproduced by incoherence, the in-crease in absorption can not. For an accuratemodeling of solar cells containing rough layer in-terfaces, scattering needs to be incorporated inthe optical model. This is achieved in the net-raditation method. Figure 3 illustrates the layerabsorbances of an a-Si:H solar cell containing arough layer interface that were computed usingthe net-radiation method.

400 500 600 700 800 9000.0

0.2

0.4

0.6

0.8

1.0

Wavelength @nmD

Lay

erA

bso

rban

ce

ip

TCO

Ag

R

Fig. 3: Layer absorbances for an a-Si:H solar cellcalculated with the net-radiation method. The TCO/pinterface is rough and scatters the transmitted light.

ZHAW 26


5.4 Three-dimensional full-wave optical simulation of light -emitting diodes

Contributors: Martin Loeser, Beat Ruhstaller

Partners: Osram Opto Semiconductor, Fluxim AGFunding: ICPDuration: 2009

Modern light-emitting diodes with material sys-tems optimized for the visible range usually suf-fer from poor outcoupling efficiencies due tothe large refractive index contrast between thesemiconductor material and the surrounding air.Taking conventional GaN LEDs as an exam-ple, it is well known that internal reflections trapmore than 90% of the internally generated light.Many efforts have been made to improve the op-tical design of such optoelectronic devices, andartificial surface textures are among the mostpromising approaches for increasing the deviceefficiency. In general, either random texturessuch as surface roughening, or systematic tex-tures such as photonic crystals can be applied,and it has already been shown in literature thatboth approaches can boost the outcupling effi-ciency.

Fig. 1: Light emitted from a device featuring a tex-tured surface.

The design of such surface textures is a chal-lenging task, and to keep development timesshort numerical simulations are of utmost im-portance. The lack of particular symmetries in

most devices mandates three-dimensional sim-ulations. It is the combination of large sim-ulation domains, inherent for LEDs, and sub-wavelength structures that makes accurate op-tical simulations a complicated task. In general,large domains call for approximative ray-opticalmethods such as ray-tracing whereas small sub-structures require full-wave methods such as Fi-nite Elements (FEM) or Finite-Difference Time-Domain (FDTD). However, it is well known thatfor these full-wave methods the computationalcost explodes with increasing device size suchthat so far only small device structures can beefficiently simulated.This project investigates to which extent anovel and very efficient finite-element basedapproach—the Ultra-Weak Variational Formu-lation (UWVF)—can reduce the computationalcost when running three-dimensional opticalsimulations. At present, the ICP is further devel-oping a software, written in C++, that incorpo-rates the UWVF-formalism to solve the opticalproblem on arbitrary structures.

Fig. 2: Light propagation in a complex structure thathas been imported from a CAD tool.

In order to enhance the computational effi-ciency, the entire software has been parallelizedwith using the Message Passing Interface. Spe-cial care is also taken to guarantee maximumuser-friendliness. Thus, the software does notonly offer advanced pre- and post-processingfeatures, but also allows to import and simulatearbitrarily complex CAD drawings.

27 ZHAW


5.5 Modeling, simulation and loss analysis of dye-sensitizedsolar cells

Contributors: Matthias Schmid, Adrian Gentsch, Jurgen O. Schumacher

Partners: EPFL Laboratoire de Photonique et Interfaces (LPI)Funding: Gebert Ruf StiftungDuration: 2008 – 2010

In September 2008 the ICP started a researchproject for the modeling of dye-sensitized solarcells (DSCs). The objective of this project is todevelop validated mathematical models for theDSC. The models aim at describing the cou-pled optical, electrical and electrochemical pro-cesses taking place within the solar cell.In the past year, we finished the work on theoptical part of the model. The optical modelallows us to simulate absorption and reflectionloss and the spatially resolved sensitizer excitedstate generation rate. The optical model hasbeen validated by optical reflection and trans-mission measurements. The generation ratecalculated from the optical model serves as aninput for the electrical model, which describesthe injection of

1.0

0.8

0.6

0.4

0.2

0.0

EQ

E

800700600500400l / nm

C101, 11.2 µm fabs simulation

EE

SE

Fig. 1: Measured EQE for illumination from the sub-strate side (SE, open circles) and the electrolyte side(EE, open triangles) on a 11.2 µm thick test cell sen-sitized with the dye C101. Red bold lines are the sim-ulated EQEs for bothillumination cases. The simu-lated fraction of absorbed light (dotted red lines) isalso shown.

electrons into the TiO2 conduction band andtheir consequent transport through the nano-porous TiO2 layer. The electrical model takesinto account recombination of conduction bandelectrons with the oxidized electrolyte species(tri-iodide) and trapping of electrons to an ex-ponential distribution of band gap states. Us-ing the coupled optical and electrical model wecan calculate the IV characteristics, the externalquantum efficiency (EQE) and the spatially re-solved concentrations of charged species (elec-

trons and ions) within the DSC. It is also possi-ble to precisely quantify the different loss chan-nels within the DSC. By comparing the mea-surements of the EQE to our simulations (seeFig. 1), we extracted the relevant model param-eters of the stationary model, the electron diffu-sion length and the electron injection efficiency.The measurements are performed on test DSCcells of different thicknesses sensitized with dif-ferent dye types and for illumination from boththe substrate and the electrolyte sides.The stationary model has been extended to sim-ulate time-dependent perturbations around thestationary state

Fig. 2: Simulated (red line) and measured (black line)transient short circuit current density for a small per-turbation induced by a red light pulse (642 nm). TheDSC was exposed to white bias light from a filteredXenon lamp.

of the DSC. Comparing the time-dependentmeasurements to simulations we find the life-time for conduction band electrons, the effectivedensity of states of trapped electrons and theshape of the (exponential) trap distribution (Fig.2).We equipped our simulation software with agraphical user interface (GUI). The GUI allowsthe user to run the different simulation tools (sta-tionary, transient, impedance spectroscopy) us-ing different sets of parameters. In the forthcom-ing project year we will further extend our modelto incorporate additional physical and electro-chemical effects.

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5.6 Optoelectronic research laboratory

Contributors: Kai Brossi, Martin Neukom, Nils A. Reinke

Partners: Various project partnersFunding: ICP, School of EngineeringDuration: ongoing

True-to-life modeling always is based on accu-rate input parameters from the real world. Thepurpose of the optoelectronic research labora-tory (O-LAB) is both providing such input pa-rameters and experimentally validating simula-tion results. Combining advanced computa-tional methods and state-of-the-art experimen-tal methods allows us to develop innovations inmeasurement engineering.

Fig. 1: Optical microscopy image of an organic pho-tovoltaic cell.

The O-LAB is a consequent expansion of ourexisting computational toolbox, facilitating thecollaboration with experimentally-oriented part-ners and industry. Our current investigationscomprise the following fields of interest:

• Ultra-fast photo-thermalheating and detection

• Thin film optical spectroscopy

• Transient optoelectronicdevice characterization

Fig. 1 shows an microscopical photography ofelectrode organic solar cell. An impedance an-alyzer used for the characterization of organic

semiconducting devices is depicted in Fig. 2.Our experimental toolbox comprises fast oscil-loscopes, signal generators, impedance analyz-ers, IR-sources, detectors and cameras, opticalflashers and spectrometers covering the spec-tral range from 0.35 and 14 µm. A measuringsetup for time resolved fluorescence and phos-phorescence spectra is currently under con-struction.The O-LAB supports industrial needs in thecharacterization of sensors and actuators andseveral ICP projects related to thermal labeling,thin-film spectroscopy, organic light emitting de-vices and photovoltaics. In addition, our labora-tory is ideally suited for educational purposes inteaching B.Sc. and M.Sc. students in mecha-tronics, electronics and informatics. The O-LABgives young scientists and engineers the possi-bility of getting in contact with R&D and workingon exciting issues in ongoing projects.

Fig. 2: Impedance analysing instruments for organicsemiconducting device characterization

29 ZHAW


5.7 Organic electroluminescent pictograms for push-button ap-plications

Contributors: Nils A. Reinke, Roger Hausermann, Beat Ruhstaller

Partners: CSEM, Ciba, EAOFunding: Commission for Technology and Innovation (CTI)Duration: 2007 – 2009

The novelty of the envisioned product in thisproject is the possibility to produce very thin,custom-designed self-luminous pictograms forapplications in push-buttons. They combine ex-isting pushbuttons (EAO) with patterned emis-sive pictograms (CSEM) made from electrolu-minescent semiconductor materials (Ciba SC).The characterization and optimization of mate-rial properties, device and system architectureis supported by computational engineering andsimulation software3 development at ZHAW asillsutrated by prototypes in Fig. 1.

Fig. 1: Transparent PLED (left) and backlighted PLEDprototype (right) developed in this project. The com-bination of blue backlight and yellowish emission fromthe PLED yields a white color emission.

The numerical simulation activities subdivideinto electronic and optical device modeling aswell as advanced analysis algorithms. Theelectronic device model contains charge drift-diffusion and exciton rate equations for mod-eling organic semiconductor devices includingmultiple excitons, several charge mobility and in-jection models and charge doping and trapping.The numerical algorithm delivers charge distri-bution profiles, transient electroluminescence,as well as current-voltage curves. The opticalsolver evaluates the angular emission charac-teristics as well as the substrate, thin-film andplasmon modes. The modes can be visualizedand integrated to extract relative mode contri-butions and position-dependent lifetimes. Keyperformance figures such as luminous efficacy,CIE, CRI, etc. are calculated. Advanced analy-sis features allow to extract device parameters,

for instance the shape of the emission zone,from experimental data. Our model fits experi-mental current-voltage curves of PLEDs consid-ering a field dependent charge carrier mobility(cf. Fig. 2).

Fig. 2: Experimental and simulated current-voltagecurves considering a field dependent mobility.

In large-area OLEDs non-uniformities in the lu-minance arise from potential drops across alow-conductive electrode. FEM-simulations al-low to study such potential drops (cf. Fig. 3).

0 V

0 V

10 V

Fig. 3: SESES simulation of the potential drop.

3SETFOS Semiconducting Emissive Thin Film Optics Simulator, Fluxim AG, Switzerland, www.fluxim.com.

ZHAW 30


Chapter 6

Student Projects

31 ZHAW


6.1 Characterization of optically pulsed solar cells

Students: Martin T. Neukom

Category: Bachelor thesisMentoring: Beat Ruhstaller, Nils A. ReinkePeriod: January 2009 – June 2009

Photovoltaic energy conversion is considered asa key technology to secure the worldwide en-ergy need without enforcing climate change. Or-ganic solar cells have the potential of signifi-cantly lower costs for solar cells that are flexible,thin and even transparent.

Fig. 1 Sample with 8 Organic Solar Cells

With these possibilities it would be possible tocoat the surface of a window with a solar cell ora facade of a building. Despite the flexibility ofusage and the huge interest of the industry thereis no single product available on the market withthis technology. The reason for that is the lowpower conversion efficiency and the short life-time. Normally, solar cells are measured with asteady state current voltage characteristic. Butthis does not allow extracting fundamental phys-ical parameters which are essential to increasethe efficiency systematically. A very promis-ing approach is the dynamic measurement. Inthis thesis a measurement setup was built forpulsed and steady-state measurements on or-ganic solar cells. The recording of IV charac-teristics was completely automated. Beside es-tablished methods in this thesis a new way ofmeasurement has been developed to close thecap between steady state and dynamics. It isbased on dynamic measurement after pulsed il-lumination with variable load resistors. The in-

terpretation of the measured data was done withSETFOS, a simulation software developed byFluxim AG. With SETFOS organic solar cellscan be numerically described. The numericalmodel includes the light-penetration into the cellas well as the electrical transport of the gener-ated free charge carriers. With simulation theeffects that have been measured could be re-produced and quantified. During the Bachelorthesis the cells showed effects of ageing. Thiseffect allowed also elaborating degradation oforganic solar cells.This thesis enables insight into the physical pro-cesses of organic solar cells and allows identi-fying limiting factors for efficiency or lifetime. Itcontributes to further developments of organicsolar cells and to reach market entry of this fu-ture technology.

Fig. 2 Transient photo-current with varying light inten-sity

ZHAW 32


6.2 Transient measurement of electroluminescence in organiclight-emitting devices

Students: Kai A. Brossi, Mario Luchsinger

Category: Bachelor thesisMentoring: Beat Ruhstaller, Nils A. ReinkePeriod: January 2009 – June 2009

The particular attraction of organic light-emittingdiodes (OLED) lies in the thin design, thelarge viewing angle and the high theoretical ef-ficency. Despite these advantages, OLEDs arenot widely used on the mass market. Two rea-sons are the limited efficiency and lifetime. Itis widely assumed that those limiting parame-ters can be identified and quantified by dynamicmeasurements. The aim of this work is to realizea measurement setup for dynamic characteriza-tion of OLEDs.

Fig. 1: Sample with eight light-emitting devices.

For the characterization, the applied voltage, thecurrent and the electroluminescence have to bemeasured. The measurement of electrolumi-nescence makes high requirements concerningsensitivity and response time. To measure thevery short rise time and the weak intensity ofelectroluminescence as exactly as possible, themeasurement has been done with a highly sen-sitive avalanche photodiode (APD) as a detec-tor. The measurement of dark current in unipo-lar devices gives the feasibility to determine thecharge carrier mobility in organic semiconduc-

tors. This requires the measurement of a lowcurrent in a nanosecond range with high dynam-ics. To setting up the dark current measurementsetup, a new measurement method has beendeveloped, that allows an elegant correction ofRC effects. The developed measurement setupgives the possibility to drive 25 OLEDs sequen-tially. The measured signals can be checked onfrequency and voltage dependency by the de-veloped software. The measurement setup hasbeen used to determine the charge carrier mo-bility in OLEDs. The metrologically determineddata has been analyzed with the simulation soft-ware SETFOS and compared with the simulateddata.

Fig. 2: Measurement box and two compact digital os-cilloscopes.

This work has been prepared at the Institute ofComputational Physics (ICP) and it helps to val-idate simulation results obtained by the simu-lation software SETFOS. The developed mea-surement setup and methods will be importantfor the research on OLEDs in the Optical Labo-ratory at the ICP.

33 ZHAW


6.3 Analysis of the emission profile in organic light-emittingdevices

Students: Benjamin Perucco

Category: Master thesisMentoring: Beat Ruhstaller, Nils A. ReinkePeriod: July 2009 – December 2009

Organic light-emitting devices (OLEDs) areideal light sources for future display applica-tions, general lighting and chemical sensorsfor their low power consumption and beneficialemission characterisitics. The outcoupling ef-ficiency of OLEDs is sensitive to the shape ofthe emission profile. Unfortunately, this shapeis typically unknown and the analysis of light ex-traction is therefore often based on the assump-tion of a delta-shaped emission profile. Theemission profile is determined by the recombi-nation profile and exciton diffusion mechanisms,as well as other electrical and device parame-ters. Already in the early days, Tang used lu-minescent sensing layers to estimate the shapeof the emission profile. Recently, experimentalinvestigations were performed using a combina-torial method for device fabrication for compre-hension of the emission profile and its relation toelectrical parameters. In recent years, modelshave been developed to accurately simulate theoptical and electrical behavior of OLEDs. Withthe help of optical simulation, Roberts illustratedhow the shape and location of the emission pro-file is related to the outcoupling efficiency. Therehave also been several reports, where simula-tion results were combined with a fitting methodto extract the emission profile. Kuma et al. mea-sured electroluminescence (EL) spectra, whichwere used for a least-square fit of simulated ELspectra as a function of the emission profile.Generally, a superposition of simulated emis-sion spectra originating from different positionsof the emissive dipoles in the light-emitting layerhas been used for the determination of the emis-sion profile. Van Mensfoort et al. have pre-sented new aspects of parameter extraction andintroduced an asymmetric analytical shape forthe description of the emission profile in single-layer polymer LEDs, which goes to zero at thelayer boundaries. They studied spectral and an-gular emission data and estimated the resolu-tion of the method based on the condition num-ber of a related matrix equation. However, I amnot aware of any publication where different fit-ting methods and aspects of parameter extrac-tion (i.e. a linear fitting method vs. a nonlin-

ear fitting method, the incorporation of angularinformation, multi-emitter OLEDs, noise on theemission spectrum, etc.) have been summa-rized, evaluated with adequate examples andvalidated on the basis of consistency checks.The objective of this study is thus to present andtest numerical fitting algorithms for the extrac-tion of the emission profile and source spec-trum. This is achieved by an optical model,where a transfer-matrix theory approach formulti-layer systems is used in combination witha dipole emission model. The optical model isimplemented in the semiconducting thin film op-tics simulator (SETFOS). With SETFOS, I sim-ulate the emission spectrum of an OLED basedon an assumed emission profile together witha known source spectrum. The fitting meth-ods are then applied to the calculated emissionspectra in order to estimate the emission pro-file and source spectrum. The comparison be-tween the obtained and assumed emission pro-file and source spectrum is an indication of howsuccessfully the inverse problem can be solved.

0 2e+26 4e+26 6e+26 8e+26 1e+27

1.2e+27 1.4e+27 1.6e+27 1.8e+27

0 0.2 0.4 0.6 0.8 1

Emis

sion

pro

file

(1/m

3)

Relative position from anode

(b)

ref: (0.3,50nm)ref: (0.5,70nm)ref: (0.9,70nm)fit: (0.3,50nm)fit: (0.5,70nm)fit: (0.9,70nm)

0 2e+26 4e+26 6e+26 8e+26 1e+27

1.2e+27 1.4e+27 1.6e+27 1.8e+27

540 560 580 600 620 640 660 680 700

Emis

sion

inte

nsity

(W/(m

2*nm

*sr))

Wavelength (nm)

(a)

ref: (0.3,50nm)ref: (0.5,70nm)ref: (0.9,70nm)fit: (0.3,50nm)fit: (0.5,70nm)fit: (0.9,70nm)

Fig. 1: Comparison between the assumed and ex-tracted emission profiles. A linear method was usedhere without incorporation of angular information.The values in parenthesis show the combination ofparameters used for the assumed emission profile tocalculate the emission spectrum. The first value in-dicates the relative position, the second value standsfor the width of the profile.

ZHAW 34


6.4 Benchmarking of optoelectronic device simulations withSETFOS

Students: Michiel Boes

Category: IAESTE internshipMentoring: Thomas Lanz, Beat RuhstallerPeriod: September 2009

The goal of this internship was to provide anoverview of the different fields of research wheresimulation results can be obtained with the soft-ware SETFOS. The topics that were consideredare passive optics, light outcoupling in organiclight emitting diodes (OLEDs), optical as well aselectrical calculations for organic solar cells, flu-orescence biosensors and purely electrical sim-ulations for OLEDs. Figure 1 illustrates the re-sult of a reflectance calculation as function ofwavelength and incidence angle.

Fig. 1: Dependence of the reflectance on wavelengthand incidence angle1.

One main quantity of interest when optimizingOLEDs is the light outcoupling behavior. SET-FOS allows to calculate the emission from sucha device as a function of emission angle andwavelength. Figure 2 displays the result of thiscalculation for a structure based on the materi-als TPD and Alq 2.

Emission Cs+

0.0E0

5.0E-2

1.0E-1

1.5E-1

2.0E-1

2.5E-1

3.0E-1

3.5E-1

4.0E-1

4.5E-1

5.0E-1

5.5E-1

6.0E-1

Cs

+

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0

Angle

400

450

500

550

600

650

700

750

800

Wa

vele

ng

th (

nm

)

Fig. 2: Study of the outcoupling from an OLED struc-ture as a function of wavelength and outcoupling an-gle.

One approach to optimize the performance oforganic solar cells is to improve the light incou-pling into the device by adding a coating layeron the device that minimizes the external reflec-tion 3. Figure 3 illustrates the effect of a coatinglayer (cap) on the generation inside an organicsolar cell.

Fig. 3: Influence of the thickness (y-axis) and the in-dex of refraction (x-axis) of a coating layer (cap) onthe generation inside an organic solar cell.

1Jorg Frischeisen, Christian Mayr, Nils. A. Reinke, Stefan Nowy, Wolfgang Brutting, Surface plasmon resonance sensorutilizing an integrated organic light emitting diode, Optics Express 22 (16), 2008

2Stefan Nowy, Nils A. Reinke, Jorg Frischeisen, Wolfgang Brutting, Light extraction and optical loss mechanisms inorganic light-emitting diodes, Experimental Physics IV, University of Augsburg, 86135 Augsburg, Germany

3Brendan O’Connor, Kwang H. An, Kevin P. Pipe, Yiying Zhao, Max Shtein, Enhanced optical field intensity distributionin organic photovoltaic devices using external coatings, Applied Physics Letters 89 (2006) 233502

35 ZHAW


6.5 High Performance Grating Spectrometer

Students: Martin Neukom, Simon Hubscher

Category: Project Work in MechatronicsMentoring: Nils A. Reinke, Christoph StammPeriod: Oktober 2008 – Januar 2009

In this work a grating spectrometer with a fo-cal length of 30cm is constructed from scratch.The exploded assembly drawing in Fig. 1 showsthe external and internal compartments of thedevice. The spectrometer offers both fixed en-trance slits ranging from 20µm to 1mm and anadjustable entrance slit. An additional mount al-lows to connect optical fibers to the device. Aholographic grating with 1200 lines/mm is usedas a dispersive element. The concave cur-vature of the grating defines the focal lengthof the device making additional optical compo-nents needless. The curved grating thus allowsa very compact design of the device and re-duces optical aberrations and losses. The spec-trum is detected with a highly sensitive CCD linesensor comprising 3000 pixels.

Fig. 1: Exploded assembly drawing of the spectrom-eter comprising the internal and external body, themounted holographic grating and the CCD line sen-sor.

The inner shielding of the device encapsulates

the CCD sensor from optical noise. The de-tectable spectrum ranges from 450nm to 750nmat a maximum spectral resolution of 0.1 nm de-pending on the width of the entrance slit. Thesensor is both powered and controlled by anUSB 2.0 interface. The developed LabView soft-ware allows calibrating both spectral positionsand absolute intensities by a build-in polyno-mial fitting routine and reading calibration datafrom a file, respectively. A screenshot of the de-veloped LabView software is displayed in Fig.2. The software offers the basic functionalityof background subtraction and setting the inte-gration time. During long acquisition processesthe user is informed about remaining recordingtime. Transient processes can be recorded at aspeed of 300 scans per second which can beaccelerated up to 3000 scans per second usingan alternative line sensor.

Fig. 2: Spectrometer software developed in LabView.

This high performance spectrometer offers highresolution, high sensitivity and high speed mak-ing it competitive with upper-class commercialproducts. This spectrometer will thus be a valu-able tool for prospective projects in the field ofthin-film optical spectroscopy and bio-sensingapplications.

ZHAW 36


6.6 Reflectometer with algorithm for refractive index extrac-tion

Students: Oliver Kunz, Felix Muller

Category: Bachelor ThesisMentoring: Beat Ruhstaller, Nils A. ReinkePeriod: February 2009 – June 2009

The task of this bachelor thesis was to developa reflectometer. A reflectometer is a device tomeasure reflectance of film systems and is usedto determine characteristics such as thicknessand refractive index of thin film systems like so-lar cells and light emitting diodes (LEDs). Moreprecisely, light is coupled into a Y-glass fiberto irradiate the film system. The outer channelof the fiber guides the reflected waves back to-wards a spectrometer, where the reflected lightintensity is measured. Subsequently a math-ematical algorithm is used to fit the measureddata to the physical model, defined by the user.In this way, unknown and/or variable parame-ters of the film system can be determined. Thisthesis is concentrated on building the respectivemeasurement setup and on developing an anal-ysis software. The spectrometer mentioned wasdeveloped in a previous student thesis 4.The user interface and the measuring proce-dures were implemented using the graphicalprogramming language LabVIEW. The user canenter specifications and estimations of the re-spective film system and perform the measure-ment. Due to performance reasons, fitting thephysical model to measurement data is imple-mented using the programming language C. ADLL interface links the two implementations.As a physical model of thin film optics, parts

of the software Setfos of Fluxim AG were im-plemented and extended. The challenge ofthis thesis was the interaction between mea-suring technique, numerical optimization algo-rithms and optics. The developed software pro-vides interfaces between user and the variousprogram modules. It is capable of determiningrefractive index parameters of various models(Cauchy, Tauc-Lorentz oscillator) as well as filmthicknesses with nanometer accuracy.

Fig. 1: Measurement setup of the reflectometer. Thegraphical user interface of reflectometer software isvisible on the screen. The measurement setup in-cluding spectrometer, light source and sample fixtureis shown in the front.

4Semester thesis ”High Performance Grating Spectrometer” by Martin Neukom and Simon Hubscher.

37 ZHAW


6.7 Motorisiertes Reflektometer zur optischenCharakterisierung von Dunnschichtsystemen

Students: Timon Low, Joel Lehner

Category: ProjektarbeitMentoring: Nils A. Reinke, Beat RuhstallerPeriod: September 2009 – Januar 2009

Wichtige Parameter fur die opto–elektronischeSimulation von Solarzellen sind das Streuver-halten, Brechungsindizes, die Absorptivitatensowie die Dicken ihrer einzelnen Schichten. DieQualitat der durchgefuhrten Simulationen steigtund fallt mit der Gute dieser Parameter. Eine ef-fiziente Methode zur Bestimmung der genann-ten Parameter ist die so genannte Reflektome-trie, bei welcher das Reflexionsvermogen voneiner Probe als Funktion der einfallenden Wel-lenlange gemessen wird. In Vorarbeiten wur-de ein Reflektometer mit einer Y-Glasfaser, ei-ner Faserlichtquelle und einem Faserspektro-meter aufgebaut, welcher die Reflektivitat ei-nes Schichtsystems bei einem festen Winkelvon 90◦ misst. Die Messdaten konnen automati-siert mit einem PC ausgewertet und die Proben-parameter Brechungsindex, Absorptivitat undSchichtdicke numerisch ermittelt werden.

Abb. 1 Aufgebautes Reflektometer mit motorisiertenSende- und Empfangsarm.

In dieser Projektarbeit wurde aufbauend aufbisherigen Vorarbeiten ein motorisiertes Re-flektometer konzipiert, welches eine auto-matisierte Reflexionsmessung unter variablenEinfalls- und Ausfallswinkel erlaubt. Die mit die-sem Instrument gewonnenen Messdaten sol-len die Extraktion von Brechungsindizes von

dunnen Schichten (n,k–Daten) sowie Die Er-mittlung von winkelabhangigen Verteilungsfunk-tionen von Grenzschichten ermoglichen, wel-che die Lichtstreuung an Grenzflachen inner-halb von Solarzellen beschreiben. Die Arbeitumfasste die folgenden Punkte:

• Konzeption und Aufbau eines Reflektome-ters mit motorisierten Sende- und Detek-torarm

• Konzeption und Aufbau einer Faserlicht-quelle

• Ansteuerung des Aufbaus unter LabViewund Entwicklung einer graphischen Benut-zerschnittstelle

Die Abbildungen 1 und 2 zeigen das aufgebautemotorisierte Reflektometer und die entwickeltegraphische Benutzeroberflache. Das Reflekto-meter wird in laufenden und zukunftigen Projek-ten fur die Charakterisierung und Optimierungvon Solarzellen eingesetzt.

Abb. 2 Graphische Benutzeroberflache zur Steue-rung des motorisierten Reflektometers.

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6.8 Innovative Schichtcharakterisierung mitHochgeschwindigkeits-Infrarot-Sensorik

Students: Markus Suter, Nenad Tripic

Category: PraktikumsarbeitMentoring: Nils A. Reinke, Andor BariskaPeriod: January 2009 – June 2009

Seit Jahren bedient man sich der Infrarot-Technologie, beispielsweise fur einfache An-wendungen, wie in Fernbedienungen furelektronische Gerate oder die Beheizungvon Raumstationen. Aufgrund des brei-ten Wellenlangenbereichs deckt die Infrarot-Technologie eine riesige Vielfalt an Anwendun-gen ab.In dieser Arbeit werden Teile eines photother-mischen Messsystems zur Untersuchung vonBeschichtungen untersucht und optimiert. Dasphotothermische Messsystem ist in Kollaborati-on zwischen dem ICP und dem IDP entstandenund soll bestehendes Messproblem der Indus-trie losen: Die Charakterisierung von Schicht-systemen auf elektrisch nicht leitfahigen Sub-straten aus Kunststoff oder Keramik.

Abb. 1 Testprobe Acryllack auf Naturholzuntergrund.

In Vorarbeiten wurde bereits ein erster Pro-totyp des Messsystems entwickelt. Dieser be-leuchtet die zu untersuchende Materialober-flache mit einem kurwelligen Xenon–Lichtblitzund erhoht somit fur einen kurzen Moment dieOberflachentemperatur. Gleichzeitig misst eineInfrarotkamera die von der Oberflache ausge-hende Warmestrahlung.Mit Hilfe der experimentell ermitteltenUbertragungsfunktion lassen sich die Parame-

ter des zugrundeliegenden Schichtsystems be-stimmen. In dieser Projektarbeit wurden die Li-mitierungen und das Potential des bestehendenPrototyps anhand von Messungen und Messda-tenanalyse ermittelt. Verbesserungen am Pro-totypen sollen helfen, das Potential dieser inno-vativen Messmethode voll auszuschopfen.

Abb. 2 Mikroskopische Aufnahme der Testprobe inLangsschnitt.

Es konnten die folgenden Arbeitspakete erfolg-reich ausgefuhrt werden:

• LabView–Steuerung des Offset-Abgleichsder IR–Kamera

• Aufbau einer Bibliothek aus Testproben

• Messung und Auswertung der Testproben

Bei einer der Testprobe handelt es sich um ei-ne mit einem Acrlyllack mehrfach beschichteteNaturholzplatte (siehe Abb. 1). Wie in der mi-kroskopischen Aufnahme in Abb. 2 zu erkennenist, zieht der Acryllack nach der Beschichtung indie Naturholzplatte ein. Neben der photothermi-schen Schichtcharakterisierung existieren keinezerstorungsfreie Messmethoden, solche Effektegezielt zu untersuchen.

39 ZHAW


6.9 Aufbau und Inbetriebnahme eines Experimental - Holzver-gasers

Students: Claudio Roffler, Fabian Senn, Marcel Weiss

Category: Bachelorarbeiten MaschinentechnikMentoring: Thomas Hocker, Christoph Meier, Markus Weber (ITFE)Period: Juni - August 2009

Unter der Holzvergasung versteht man denverfahrenstechnischen Prozess der Teilverbren-nung unter Luftmangel, um aus Holz ein brenn-bares Gasgemisch zu gewinnen. Im Rahmenzweier Bachelorarbeiten ist ein Holzvergaseraufgebaut und in Betrieb genommen worden.Nebst dem mechanischen Aufbau ist viel Zeitin die umfangreicher Messtechnik investiert wor-den, da der Vergaser zur Modellvalidierung ein-gesetzt werden soll.

Abbildung 1: Experimental-Holzvergaser auf demDach des Maschinenlabors

Insgesamt wurden zehn Messungen durch-gefuhrt. Mit Ausnahme der eingesetzten Bio-masse kann der Prozess ausschliesslich uberdie zugefuhrte Luftmenge gesteuert werden.Der auf den Reaktordurchmesser bezogeneLuftmassenstrom ist dabei zwischen 35 und 200

g/(m2s) variiert worden. Die Luftuberschusszahlλ bewegte sich dadurch zwischen 0.23 und 0.95(λ = 1 bedeutet stochiometrische Verbrennung),die Flammfrontgeschwindigkeit zwischen 0.12und 0.21 mm/s, der Restkohlenanteil zwischen2 und 28 Massen-% bezuglich der unvergasten,trockenen Biomasse.

Abbildung 2: Erste Zundung des Vergasers durchMarcel Weiss

Bei drei Versuchen wurde ausserdem die Gas-zusammensetzung ermittelt. Die erste Stufe derMessgasaufbereitung besteht aus einer beheiz-ten Gasentnahmesonde und einem Konden-satabscheider. Die Kuhlung ist mit einem Ab-scheiden von Teeren verbunden, da diese alslangere Kohlenwasserstoffe bei Raumtempe-ratur nicht mehr gasformig vorliegen. Die ei-gentliche Teerabscheidung erfolgt in Wasch-flaschen mit Rapsol, in welchem die entstan-denen Teere eine gute Loslichkeit aufweisen.Nach einem Feinfilter werden die GasspeciesCO, CO2, CH4 infrarotbasierend und H2 mit-tels Warmeleitfahigkeitssensor gemessen. DieElementarbilanz fur die Elemente C, H, Ound N ist befriedigend genau ausgefallen, wasauf ein funktionierendes Messkonzept hindeu-tet. Die Durchfuhrung von Versuchen ist nochstorungsanfallig. Auf der Prozessseite soll derkontinuierliche Betrieb des Reaktors die Bilan-zierung vereinfachen und die Reproduzierbar-keit der Messungen verbessern. Hierzu sindVorschlage ausgearbeitet und zum Teil bereitsumgesetzt worden.

ZHAW 40


6.10 Optimierung eines Prufstands fur thermomechanischeBelastungstests von Hochtemperatur-Brennstoffzellen

Students: Marcio Ferreira dos Santos, Jakob Spillmann

Category: Bachelorarbeit MaschinentechnikMentoring: Thomas Hocker sowie Dirk Haberstock und Thomas Gamper (Hexis AG)Period: 15. Juni bis 17. August 2009

Der Brennstoffzellen-Stapel bildet den Kernder Brennstoffzellen-Heizgerate der Hexis AG,Winterthur. Die Hexissysteme sind mit ca.60 Keramik-Brennstoffzellen bestuckt. Um Er-kenntnisse uber das Verhalten der Zellen beiinhomogenen Zellentemperaturen zu erhalten,wurde in vorangegangen Studentenarbeiten einPrufstand fur thermomechanische Belastungs-test entwickelt. Mit diesem Prufstand werdenVersuche durchgefuhrt, in denen die Brennstoff-zellen durch vorgegebene Temperaturgradien-ten zerstort werden. Die auftretenden Zellenris-se werden uber einen Akustiksensor detektiert,siehe Fig. 1

Fig. 1 Akustiksignal aufgrund eines thermisch indu-zierten Risses der Brennstoffzelle.

In dieser Bachelorarbeit soll dieser Prufstandoptimiert werden. Wichtig sind dabei eine deutli-che Verkurzung der Versuchsdauer, das Detek-tieren des Risszeitpunktes und das Erhohen dermaximal erreichbaren homogenen Temperatur-verteilung. Im Prufstand (siehe Fig. 2) wird dieBrennstoffzelle zwischen zwei ubereinander an-geordneten Stahlplatten eingeklemmt. Die obe-re Stahlplatte kann durch drei unabhangige Hei-zungen erhitzt werden. An der unteren Plattesind Temperatursensoren und die Anbindung aneinen Akustiksensor, welcher den Zellbruch re-gistriert, angebracht.Ein typischer Messzyklus lauft wie folgt ab: zu-erst wird der Prufstand homogen auf eine Ba-sistemperatur aufgeheizt, dann wird ein Tempe-raturgradient induziert und so lange erhoht, bisdie Zelle bricht. Anschliessend wird abgekuhlt.Mit einer Vielzahl an Verbesserungsmassnah-men wurde der Prufstand Schritt fur Schritt op-timiert. Durch den Einsatz einer Isolationsbox,

einer verbesserten Regelung und einem Rede-sign des Prufstands konnte die Aufheizzeit von103 min auf 12.5 min verkurzt werden. Das Ver-wenden einer aktiven Kuhlung erbrachte eineZeitersparnis von weiteren 20 min. Insgesamtwurde die Zykluszeit von 170 min auf 50 minverkurzt.Eine verbesserte Anbindung des Akustiksen-sors an den Prufstand erlaubt nun ein zu-verlassiges Erkennen des Zellrisses, solangedie Keramikummantelung intakt bleibt. Die ma-ximal erreichbare Basistemperatur konnte von255◦C auf 500◦C erhoht werden. Zudem wurdedie Regelung optimiert und der Prufstand beina-he vollstandig automatisiert. In FE-Rechnungenwurde die T-Verteilung uber der Zelle simuliert,siehe Fig. 3. Das Modell konnte anhand derMessdaten verifiziert werden.

Fig. 2 Warmebildaufnahme des Prufstands.

Fig. 3 Seses FE-Rechnungen der T-Verteilung uberdie Zelle als Funktion der Zeit.

41 ZHAW


ZHAW 42


Chapter 7

Appendix

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7.1 Scientific Publications

• J.O. Schumacher, J. Eller, G. Sartoris: A 2+1D Model of a Proton Exchange Membrane FuelCell with Glassy-Carbon Micro-Structures, 6th Vienna International Conference on Mathe-matical Modelling, ARGESIM-Publishing House, ARGESIM Report no. 34, Eds. I. Troch andF. Breitenecker, ISBN 978-3-901608-34-6, Vienna, Austria, 2396–2405 (2009).

• S. Wenger, M. Schmid, G. Rothenberger, M. Gratzel, J.O. Schumacher: Model-based Opticaland Electrical Characterization of Dye-Sensitized Solar Cells, 24th European PhotovoltaicSolar Energy Conference EU PVSEC, Hamburg, Germany, 21-25 September 2009 (2009).

• Th. Lanz, B. Perucco, D. Rezzonico, F. Muller, N. A. Reinke, R. Hausermann, B. Ruhstaller:Optical Simulation of Arbitrary Thin Film Solar Cells with Rough Interfaces, 24th EuropeanPhotovoltaic Solar Energy Conference and Exhibition EU PVSEC, Hamburg, Germany, 21-25September 2009 (2009).

• Y. Safa and T. Hocker: Numerical Simulation of Reactive Transport Phenomena in the HexisSOFC Stack, ECS Transactions, 25 (2) 1221-1230 (2009).

• Y. Safa and J. O. Schumacher: Numerical Modelling of The Two Phase Transport in a PEMFuell Cell, Proceedings of Third European Fuel Cell Technology & Applications Piero LunghiConference EFC2009,161–162 (December 15-18, 2009).

• R. Hausermann, E. Knapp, M. Moos, N. A. Reinke, Th. Flatz, and B. Ruhstaller: Coupledoptoelectronic simulation of organic bulk-heterojunction solar cells: Parameter extraction andsensitivity analysis, J. Appl. Phys. 106, 10450 (2009).

• J. Frischeisen, N. A. Reinke, W. Brutting: ORGANIC EMITTERS: OLEDs enable integratedsurface-plasmon-resonance sensor, Laser Focus World Art. No. 359812 (2009).

7.2 News Articles

• B. Ruhstaller: Organische Solarzellen eroffnen kostengunstige Moglichkeiten, energeia Newslet-ter des Bundesamts fur Energie, Ausgabe 6 (November 2009).

• H.U. Schwarzenbach: Moglichkeiten und Grenzen der Modellbildung, Innovation (Juni 2009).

• R. Hausermann and B. Ruhstaller: Organische Solarzellen, SEV Bulletin (Mai 2009).

• B. Ruhstaller: Brillante Bilder und leuchtende Wande, Polyscope (April 2009).

7.3 Conferences and Workshops

• B. Ruhstaller: Optoelectronic simulation of organic semiconductor devices for displays, light-ing and photovoltaics, Case Study Seminar Computational Science and Engineering at ETHZ,Zurich, 26 February (2009).

• J. O. Schumacher and Y. Safa: Numerical simulation of transport phenomena in PEM fuelcells, ALGORITMY 2009 Conference on Scientific Computing, Vysoke Tatry, PodbanskeMarch 15-20 (2009).

• E. Knapp, H. Schwarzenbach, R. Hausermann, N. A. Reinke, B. Ruhstaller: Advanced Simu-lation Methods for Charge Transport in OLEDs, Deutsche Physikalische Gesellschaft (DPG)Fruhjahrestagung, Symposium Organic Photovoltaics, Dresden, March (2009).

• N. A. Reinke, R. Hausermann, E. Knapp, M. Moos, T. Flatz, B. Ruhstaller: Fully Cou-pled Opto-electronic Modelling of Organic Solar Cells, Deutsche Physikalische Gesellschaft(DPG) Fruhjahrestagung, Symposium Organic Photovoltaics, Dresden, March (2009).

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• R. Hausermann, N. A. Reinke, E. Knapp, T. Flatz, M. Moos, B. Ruhstaller: CT-State Dissoci-ation and Charge Carrier Recombination in OPV cells, Deutsche Physikalische Gesellschaft(DPG) Fruhjahrestagung, Symposium Organic Photovoltaics, Dresden, March (2009).

• N.A. Reinke, R. Hausermann, E. Knapp, M. Moos, T. Flatz, B. Ruhstaller: Fully CoupledOpto-electronic Modelling of Organic Photovoltaic Cells, Hybrid and Organic PhotovoltaicsConference (HOPV), Benidorm, Spain, 10-13 May (2009).

• Hausermann, Reinke, Ruhstaller: CT-State Dissociation and Charge Recombination in Or-ganic Photovoltaic Cells, Hybrid and Organic Photovoltaics Conference (HOPV), Benidorm,Spain, 10-13 May (2009).

• B. Ruhstaller: Organische Halbleiterbauelemente fur Bildschirme, Beleuchtung und Photo-voltaik: Modellbildung und Simulation, Electrosuisse Fachtagung ”Elektronik der Zukunft”,Winterthur, 2. Juli (2009).

• B. Ruhstaller, R. Hausermann, N.A. Reinke: Comprehensive simulation of organic solar cells,2nd International User Workshop 2009, Winterthur, July (2009).

• B. Ruhstaller, E. Knapp: Advanced simulation of charge transport in OLEDs, 2nd Interna-tional User Workshop 2009, Winterthur, July (2009).

• B. Ruhstaller: Next Generation (Organic) PV: Modeling and Simulation, 3rd Generation Pho-tovoltaics Meeting of the Swiss Laser Net, CSEM Basel, Switzerland, 19 August (2009).

• S. Wenger, M. Schmid, G. Rothenberger, M. Gratzel and J.O. Schumacher: Model-basedoptical and electrical characterization of dye-sensitized solar cells, 24th European Photo-voltaic Solar Energy Conference and Exhibition (EU PVSEC), Hamburg, Germany, Septem-ber (2009).

• Th. Lanz, B. Perucco, D. Rezzonico, F. Muller, N. A. Reinke, R. Hausermann, B. Ruhstaller:Optical Simulation of Arbitrary Thin Film Solar Cells with Rough Interfaces, 24th EuropeanPhotovoltaic Solar Energy Conference and Exhibition (EU PVSEC), Hamburg, Germany,September (2009).

• B. Ruhstaller: OLEDs fur Beleuchtung, FutureLight Meeting, ZHAW, Winterthur, 22 October(2009).

• B. Ruhstaller: Forschung an Solarzellen der nachsten Generation, Nationaler Tag der Tech-nik an der ZHAW, Winterthur, 10 November (2009).

• Y. Safa, T. Hocker: Numerical Simulation of Reactive Transport Phenomena in the HexisSOFC-Stack: Modelling Concept & Numerical Methods, 216th ECS Meeting and 11th In-ternational Symposium on Solid Oxide Fuel Cells (SOFC-XI), Vienna, Austria, October 4-9,(2009).

7.4 Prizes and Awards

• Martin Neukom received the Thales–Preis for his Bachelor Thesis Characterisation of opticalpulsed solar cells.

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7.5 Teaching

Bachelor of Science

• ”Mathematik fur Ingenieure 1” (MAE 1) - R. Axthelm

• ”Diskrete und Numerische Mathematik” fur Mechatroniker (DNM) - H. Schwarzenbach

• ”Signale und Systeme 1” (SiSy 1) - J.O. Schumacher

• ”Signale und Systeme 2” (SiSy 2) - J.O. Schumacher

• ”Physik 1” fur Maschinentechniker (PHMT1) - M. Schmid

• ”Physik 1” fur Wirtschaftsingenieure (PhWI 1) - T. Lanz

• ”Physik 1” fur Unternehmensinformatiker (PhUI 1) - N. A. Reinke

• ”Physik 2” fur Maschinentechniker (PHMT2) - J.O. Schumacher

• ”Physik 2” fur Wirtschaftsingenieure (PhWI 2) - M. Roos

• ”Physik 2” fur Unternehmensinformatiker (PhUI 2) - N. A. Reinke

• ”Modellbildung und Simulation fur Material- und Verfahrenstechniker (MBS)” - Th. Hocker

• ”Mensch, Technik, Umwelt” fur Maschinentechniker (MTU)- Th. Hocker

Master of Science

• ”Material Properties of Crystals / Tensors for Engineers” (Engineering)- M. Roos

• ”Heat and Mass Transfer with Two-Phase Flow” (Engineering) - Th. Hocker

• ”Multiphysics Modelling and Simulation” (Engineering) - J.O. Schumacher

• ”Applied Photonics” (Mirco and Nano Technolgoy) - B. Ruhstaller

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7.6 ICP Team Members

The ICP team members as of December 2009 are listed below.

Name Title FunctionAxthelm, Rebekka Dr. rer. nat., Dipl. Math Research AssociateBrossi, Kai B.Sc. in Systems Engineering Research AssistantFlatz, Thomas Dipl. Ing. FH MSE StudentGentsch, Adrian B.Sc. in Systems Engineering Research AssistantHausermann, Roger Dipl. Phys. ETH Research Assistant, PhD studentHocker, Thomas Prof. Dr. Chem. Eng. LecturerKnapp, Evelyne Dipl. Rech. Wiss. ETH Research Assistant, PhD StudentLanz, Thomas M.Sc. Physics ETH Research Assistant, PhD StudentLindner, Markus MSc. in Engineering MSE StudentLoeser, Martin Dr. sc. ETH, Dipl. Ing. TUM Research AssociateNeukom, Martin B.Sc. in Systems Engineering Research AssistantOdermatt, Beat Dipl. Ing. FH Research AssociatePerucco, Benjamin Dipl. Ing. FH Research Assistant, MSE StudentReinke, Nils A. Dr. rer. nat., Dipl.-Phys. LecturerRoos, Markus Prof. Dr., Dipl. Phys. ETH LecturerRuhstaller, Beat Prof. Dr., Dipl. Phys. ETH, e-MBA Lecturer, Head of the ICPSafa, Yasser Dr. es sc., MSc. Research AssociateSartoris, Guido Dr., Dipl. Phys. ETH Research AssociateSchmid, Matthias Dr. es sc., Dipl. Phys. ETH Research AssociateSchwarzenbach, Hansueli Prof. Dr., Dipl. Math. ETH LecturerSchumacher, Jurgen Dr. rer. nat., Dipl.-Phys. LecturerTiefenauer, Andreas Dipl. Ing. FH MSE StudentToniolo, Lilian Administrative Assistant

The following visiting scientists were staying at the ICP for some time during 2009:

• Michiel Boes, IAESTE trainee, Ghent University, Belgium: August – September 2009

• Remo Ritzmann, LED Hardware Designer, Pfunzle.ch, Switzerland: May 2009

7.7 Location and Contact Info

Institute of Computational PhysicsZurich University of Applied SciencesWildbachstrasse 21 (TK)8401 WinterthurSwitzerlandwww.icp.zhaw.ch

Head of the instituteProf. Dr. Beat RuhstallerPhone +41 (0)58 934 78 36Fax +41 (0)58 934 77 97E-Mail: [email protected]

AdministrationLilian TonioloPhone +41 (0)58 934 73 06E-Mail: [email protected]

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Zürcher Hochschule für Angewandte Wissenschaften

School ofEngineering

ICP Institute of Computational PhysicsTechnikumstrasse 9PostfachCH-8401 WinterAthur

Tel. +41 58 934 71 71Fax +41 58 935 71 71

[email protected]

zhaw icp research report 2009

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