Amsterdam

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1 Eidgenössisches Departement für Umwelt, erkehr, Energie und Kommunikation UEK Bundesamt für Energie BFE Konferenzbericht th European Photovoltaic Solar Energy Conference and Exhibition Amsterdam S:\Administration\EU_Konferenz\29th_Europ_Konferenz_Amsterdam 2014\Zusammenfassung Bericht\Bericht 29. EUPSEC Amsterdam 2014.docx

2 Auftraggeber: Bundesamt für Energie BFE Forschungsprogramm Photovoltaik CH-3003 Bern Auftragnehmer: NET Nowak Energie und Technologie AG Waldweg 8 CH-1717 St.Ursen BFE-Bereichsleiter: Dr. Stefan Oberholzer BFE-Programmleiter: Dr. Stefan Nowak BFE-ertrags- und Projektnummer: SI/ / SI/ Für den Inhalt und die Schlussfolgerungen sind ausschliesslich die Autoren dieses Berichts verantwortlich.

3 Die 29 th European Photovoltaic Solar Energy Conference and Exhibition aus Schweizer Sicht Inhaltsverzeichnis S. Nowak, T. Biel Übersicht... 4 J.-W. Schüttauf, E. Moulin, A. Faes, H.-Y. Li, F. Meillaud and C. Ballif Thin-film silicon and crystalline silicon solar cells... 9 A.N.Tiwari II - I compound thin film solar cells T. Friesen, M. Marzoli, A. irtuani, R. Rudel P module performance, testing, qualification and certification BIP Building Integrated P U. Muntwyler P Inverters and Electrical System Technology F. Baumgartner P systems and grid integration R. Itten, R. Frischknecht Environmental aspects of P components and systems P. Hüsser Global aspects T. Biel Ausstellung Anhang - Liste der Beiträge mit Schweizer Beteiligung /51

4 Die 29. Europäische Photovoltaikkonferenz in Amsterdam Übersicht S. Nowak, T. Biel Programmleitung Photovoltaik BFE NET Nowak Energie & Technologie AG Waldweg 8, CH-1717 St. Ursen Tel. +41 (0) , Fax +41 (0) Allgemeines Die 29. Europäische Photovoltaikkonferenz (EU PSEC) war ein weiterer Photovoltaik Grossanlass. Insgesamt nahmen rund eingeschriebene Teilnehmer aus 76 Ländern (siehe Fig. 1) an der diesjährigen Konferenz teil, was jedoch einen weiteren Rückgang von etwa 20% gegenüber dem orjahr entspricht. Dennoch hat sich der Besuch der EU PSEC seit Jahren als idealer Ort etabliert, um sich über die neuesten Trends in Technologie und Markt zu informieren, Kontakte zu knüpfen, Geschäfte einzufädeln oder an den zahlreichen projektbezogenen Treffen teilzunehmen. Fig. 1: Übersicht der Konferenzteilnehmer nach Herkunftsländern Innerhalb der Konferenzteilnehmer hatte etwa die Hälfte einen wissenschaftlichen Hintergrund während die andere Hälfte grösstenteils aus ertretern der Industrie aber auch aus dem Finanz-, ersicherungs- und Dienstleistungsbereich sowie weiteren angrenzenden Beschäftigungsfeldern bestand. Eine kurze Übersicht hierzu findet sich in der folgenden Grafik: 4/51

5 Fig. 2: Übersicht zu Hintergrund der Konferenzteilnehmer Insgesamt gab es ca Konferenzbeiträge, davon wurden rund 300 mündlich präsentiert. Abgerundet wurde die wissenschaftlich-technologische Konferenz durch diesmal 8 Begleitveranstaltungen mit insgesamt 100 Beiträgen. Innerhalb dieser 8 Begleitveranstaltungen wurden folgende 3 eranstaltungen durch IEA-PPS organisiert und stiessen auf reges Interesse der Konferenzteilnehmer. Self-consumption Business Models - Technical and Economic Challenges jointly with IEA International Energy Agency PPS Task 1 / Task 14 P Performance Analysis and Module Reliability jointly with IEA International Energy Agency PPS Task 13 P Life Cycle Management & Recycling jointly with IEA International Energy Agency PPS Task 12 Die begleitende Industrieausstellung ist gegenüber dem orjahr nochmals deutlich geschrumpft, was anhand der Entwicklungen vor allem innerhalb der europäischen P Branche im Jahr 2014 auch zu erwarten war. Mit dem Becquerel-Preis wurde in Amsterdam Dr. Stefan Glunz ausgezeichnet und damit seine Pioniertätigkeit in der Entwicklung von hocheffizienten auf siliziumbasierten Solarzellen gewürdigt. 5/51

6 Wissenschaftlich-technische Entwicklungen In Amsterdam war ein Schwerpunkt bei den Beiträgen wieder auf den verschiedenen Typen von Solarzellen gelegt. Beim kristallinen Silizium ist weiterhin ein grosses Interesse an der Heterojunction Technologie (SHJ) festzustellen. Panasonic erreichte hier bereits im Januar 2014 einen neuen Rekord-Wirkungsgrad von 25.5% mit SHJ-IBC Zellen (>100 cm2). Sharp erreichte ebenfalls einen Wirkungsgrad von 25.1% mit SHJ-IBC Zellen, jedoch in kleinerem Massstab (<4 cm2). Benjamin Strahm stellte das Swiss-Inno HJT Projekt vor und gab einen Wirkungsgrad von 23.5% bekannt. Weitere Hersteller publizierten ebenfalls Wirkungsgrade von 22% bzw. 23%. Coshu Industry Co stellte an der EU-PSEC ein Smartwire-Modul mit 60 Zellen und einer Leistung von 327 Wp vor. Zu Stromgestehungskosten von Silizium- Photovoltaik gab es einen eigenen Keynote ortrag von M. Hermle vom Fraunhofer ISE. Weiterhin wurden Möglichkeiten präsentiert, wie sich innerhalb der Produktion einzelne Prozesse vereinfachen lassen bzw. gesamthaft Prozessschritte eingespart werden können. Bezüglich der in der Produktion eingesetzten Materialien besteht weiterhin ein Fokus auf der Reduktion des Silberanteils bei der Kontaktierung. Neben dem Siliziumwafer ist dies immer noch der zweithöchste Kostenfaktor. Als einen von vielen Lösungsansätzen präsentierte Meyer Burger seine SmartWire mit der der Silberverbrauch auf etwa 50 mg je HJT-Zelle reduziert werden kann und Kosten von nur noch 23 ct/wp entstehen. Zum Thema der Silizium-Dünnschicht-Solarzellen (vgl. Zusammenfassung von C. Ballif et al.) hatte C. Ballif vom IMT einen Plenary-ortrag, in dem er den aktuellen Status dieser Technologie weltweit und die aktuellen Arbeiten am IMT vorstellte. Zwischen den beiden Konferenzen in Paris und Amsterdam wurden unterschiedlichste Wirkungsgrade erreicht und in diesem Plenary vorgestellt. So erreichte das IMT einen Zellwirkungsgrad von 12.63% für mikromorphe Zellen. AIST aus Japan und das FZJ aus Deutschland erreichten Wirkungsgrade von 10.22% für single-junction a-si:h Zellen. Bezogen auf ein Modul erreichte TEL Solar einen Wirkungsgrad von 12.2%. Zum gesamten Thema der Silizium- Dünnschicht-Solarzellen gab es in Amsterdam 3 Parallelveranstaltungen. J.-W. Schüttauf eröffnete die eranstaltung zur Entwicklung von Silizium-Dünnschicht-Solarzellen und stellte hierbei u.a. triplejunction Zellen in unterschiedlichen Konfigurationen vor, wobei mit a-si/a-sige/µc-si ein stabiler Wirkungsgrad von 11.3% erreicht werden konnte und mit a-si/µc-si/µc-si Konfiguration 12.8%. Weiterhin wurde eine quadruple-junction Zelle vorgestellt und ein Ausblick gegeben, wie ein stabiler Wirkungsgrad von 14% erreicht werden kann. A. Zhang von der Nankai Universität in China präsentierte einen Wirkungsgrad von 16.1%, der kurzzeitig mit einer 0.25 cm 2 grossen a-si:h/a-sige:h/µc-si:h triplejunction Zelle erreicht werden konnte. Eine zweite Parallelsession befasste sich mit neuen Konzepten zum Licht-Management. Hier präsentierte u.a. E. Moulin vom IMT einen ergleich von 2 unterschiedlichen Typen von Reflektoren. L.. Mercaldo untersuchte das optische Zusammenspiel zwischen einem SiOx-basiertem Reflektor (IR) und dem Lichtmanagement in Tandemzellen. Dabei stellte sich heraus, dass IRs mit hoher Brechzahl n vor allem bei flachen TCOs bevorzugt werden sollten währenddessen sich IR Schichten mit kleiner Brechzahl bei rauen front-tco Subtraten besser geeignet sind. Die dritte Parallelveranstaltung befasste sich mit Prozessschritten und Materialien in der Herstellung. Hier stellte u.a. M. Stuckelberger vom IMT einen ergleich zwischen verschiedenen a-si:h Materialien unter Berücksichtigung der durch Licht beeinflussten Degradation und deren erwendung als Absorberschicht in Silizium-Dünnschicht-Solarzellen. Zum Thema Solarzellen auf der Basis von erbindungshalbleitern (vgl. Zusammenfassung von A.N. Tiwari et al.), gab es abermals viele Beiträge (insgesamt 146 mündliche und Poster-Präsentationen). Die ielzahl der Poster zeigen die weiterhin rege Forschungsarbeit in diesem Bereich Dünnschicht- Solarzellen. An der Konferenz in Amsterdam konnten auch wieder neue Rekorde bei den Wirkungsgraden sowohl im Labormassstab wie auch bei den Modulen vermeldet werden. So erreichte das ZSW bei einer CIGS-Solarzelle einen Wirkungsgrad von 21.7%. Für CdTe und CZTSSe liegen die derzeit höchsten Wirkungsgrade bei 21% bzw. 12.6%. Durch die Dotierung von CIGS mittels Kalium wurde es möglich hohe Spannungen bei CIGS Zellen zu erreichen. Zudem wurden alternative Konzepte für Zn(O,S) Pufferschichten und zur Oberflächenpassivierung diskutiert, womit grundsätzlich Cdfreie und effizientere Module mit festen sowie flexiblen Subtraten erreicht werden können. Im Bereich der Qualitäts- und Leistungstests (vgl. Zusammenfassung von R. Rudel et al.) liegt derzeit ein Fokus auf der Untersuchung der Zuverlässigkeit von P Modulen in Wüstenklimas. Zudem steigt weiterhin das Interesse an möglichst genauen Prognosen zur Lebensdauer und Zuverlässigkeit von P Systemen. Hierzu veröffentlichte das NREL Ergebnisse einer Studie zur Degradation weltweit und präsentierte ebenfalls neue Standards für unterschiedliche klimatische Bedingungen, die zukünftig eingeführt werden sollen. 6/51

7 PID wird innerhalb der P Branche immer mehr als ernste Bedrohung angesehen, da besonders bei langen Ketten von P Modulen ein hohes Potenzial von PID beobachtet werden konnte. Zu diesem Thema gab es an der EUPSEC eigens eine Session. In einem ortrag erörterte P.Lechner vom ZSW die Notwendigkeit, einen verbesserten indoor-testmodus zu entwickeln. Die ZHAW (Schär et al.) präsentierte ihren mobilen LED Flasher, mit dem auch vor Ort beispielsweise die Funktionalität der Beipassdiode im einzelnen Modul der P Anlage überprüft werden kann. Zudem zeigte A. Pozza (JRC) die Ergebnisse von Tests (LBIC und Elektroluminiszenz) an 20 Jahre alten c-si Modulen und den Zusammenhängen zu deren Leistungsdegradation. Bei der EDF wurde ein Modell zu Alterung von P Modulen bezogen auf verschiedene Klimazonen entwickelt. Dieses Alterungsmodell berücksichtigt ebenfalls mechanische Fehler wie hot-spots oder auch eindringendes Wasser und kann relativ gut den Einfluss des gewählten Parameters vorhersagen. Weiterhin gab es an der Konferenz in Amsterdam ein kleines Meeting zu bifacial P Modulen, wobei Strategien zur zukünftigen Forschung und die einzelne Rollenverteilung zwischen den beteiligten Institutionen besprochen wurden.. Zur gebäudeintegrierten Photovoltaik (vgl. Zusammenfassung von R. Rudel et al.) gab es in Amsterdam zwei Sessionen und einen Parallelevent. or allem im Hinblick auf die Politik der EU zu Nullenergie-Gebäuden, wobei nach 2019 alle Neubauten diesen Standard zu erfüllen haben, geben diesem Thema immer mehr Aufschwung. Dieses Ziel wäre leicht zu erreichen, jedoch fehlen momentan noch passende Tools zur Planung. Nach einer Studie der EPIA ist gebäudeintegrierte Photovoltaik derzeit nur für etwa 3% des erzeugten P Stroms verantwortlich. In der Session zu P als Teil von Baumaterialien wurden u.a. vorgefertigte Systeme zur Dachsanierung vorgestellt, womit eine Ersparnis von etwa 30% gegenüber einer herkömmlichen Dachsanierung mit anschliessender Installation einer P Anlage erwartet wird. F. Moralejo von CIEMAT präsentierte Ergebnisse seiner Untersuchungen zu den optischen Eigenschaften von BIP Modulen. Als dessen Schlussfolgerung wird ersichtlich, dass die aktuelle Norm EN410 zur Beurteilung des g-faktors von P Modulen nicht mehr ausreichend ist und überarbeitet werden sollte. In der zweiten Session zu Photovoltaik und Architektur wurden u.a. Fragestellungen, wie bzw. was Architekten brauchen oder wo die Unterschiede zwischen herkömmlichen Baumaterialien und denen mit integrierter P Technologie liegen, diskutiert. An der EU PSEC sind mittlerweile immer weniger ertreter der Wechselrichter- und der BOS- Branche (vgl. Zusammenfassung von U. Muntwyler et al.) vertreten. ereinzelt wurden unterschiedliche Batteriesysteme von Ausstellern präsentiert. Bei Batterien kommen weiterhin mehrheitlich Systeme auf Basis von Lithium und Blei zum Einsatz. Diese sind am weitesten ausgereift und bieten gute Gesamtpakete aus Anzahl Zyklen, Effizienz, Lebensdauer und Sicherheit. Die Preise liegen hier jedoch aktuell noch deutlich über /kwh, wobei in den kommenden Jahren eine deutliche Absenkung erwartet wird. Weiterhin kommen derzeit bisher eher vereinzelt Redox-Flow Batterien oder auch Hochtemperatur-Batterien zum Einsatz. Diese haben jedoch diverse Nachteile wie etwa Selbstentladung bei der Hochtemp.-Batterie oder die niedrige Effizienz von nur 60-74% der Redox-Flow Batterie. Mit anadium kann die Effizienz einer Redox-Flow Batterie auf mehr als 75% (M. Bruch, Fraunhofer ISE) gesteigert werden. Zukünftig rechnet das ISE hier mit Preisen von /kwh. Bezüglich der Sicherheit von Solarspeicher-Batterien hat das KIT eine Sicherheits-Checkliste publiziert. Balance of system (BOS) Aspekte wurden nur in wenigen Beiträgen angesprochen. Das Thema P Systeme und deren Netzintegration erhält auch an der EU PSEC immer mehr Gewicht (vgl. Zusammenfassung F. Baumgartner). Am Beispiel der Stadtwerke Ulm wurde u.a. ein konkretes Projekt mit dem Fokus auf der Kommunikation von P Anlagen im Smart Grid der Zukunft aufgezeigt. Weiterhin werden präzise Wettervorhersagen ein immer wichtigeres Instrument zur Planung des Day-Ahead Krafwerkseinsatzes für Regionen mit einer hohen P Pentration wie beispielsweise Bayern. In einer eigenen Session zu diesem Thema wurden neue Wetter-Algorithmen vorgestellt, mit denen Ungenauigkeiten von nur noch 2%, bezogen auf die Stundenprognose bei der Stromerzeugung durch P, möglich sind. Ein zweiter Schwerpunkt bildete die lokale Integration des P Stroms von z.b. Batterie Speichern oder andere Massnahmen zur Erhöhung des Eigenstrombedarfs. ela Solaris hat hier mittlerweile sein Planungstool Polysun erweitert, so dass der Eigenstromanteil von P-System mit Wärmepumpe (zwei Power Levels) und Batteriespeicher berechnet werden kann. In einem Beitrag wurden hier bereits realisierte grössere Lithium-Batterie-Containerlösungen mit beispielsweise 1.1 MW / 580 kwh vorgestellt, die seit März 2012 in Betrieb sind und Round Tripp Efficiency alues von bis zu 97% ermöglichen (Lebensdauer bis 20 Jahre seien ebenfalls möglich!). Zum Thema Umwelteinflüsse von P Systemen (vgl. Zusammenfassung von R. Frischknecht) gab es in Amsterdam nur wenige Beiträge. In einem Schweizer Beitrag wurden die Effekte des Imports aus 4 Weltregionen (China, Asien, Amerika und Pazifik) auf den ökologischen Fussabdruck des in der EU produzierten P Stroms aufgezeigt. Während die Energierücklaufzeit bei etwa 3 Jahren stabil geblieben ist gab es beim ökologischen Fussabdruck (bezogen auf CO2) eine weitere Steigerung aufgrund des grösseren Anteils Modulen aus China. Durch IEA-PPS wurde eine Parallel-Session 7/51

8 organisiert, die sich mit dem Management der Lebenszykluskosten und dem Recycling von P Modulen beschäftigte. Derzeit ist der Markt noch relativ klein und die aktiven Firmen sammeln weiterhin noch Erfahrung. Jedoch kann gesagt werden, dass die Qualität des zurückgewonnenen Materials doch eher gering ist. Dies lässt sich jedoch sehr wahrscheinlich auf die ebenfalls eher schlechte Qualität der recycelten Module zurückführen. Das Optimum (ökonomisch und ev. ökologisch) ist hierbei noch nicht erreicht. Unter dem Titel Global Aspects (vgl. Zusammenfassung von P. Hüsser) wurden neben Kosten/Preise diesmal vor allem auch Eigenverbrauch und Speicherung diskutiert. Grundsätzlich hat sich die Stimmung innerhalb der P Branche wieder gebessert. Die Marktentwicklung ist weiterhin positiv, der Preiszerfall der vergangenen Jahre hat sich stark abgeschwächt und es konnten Überkapazitäten abgebaut werden, sodass vor allem grosse chinesische Modulhersteller auch wieder Gewinne schreiben. Mit tiefen Zinsen und grösseren Analgen können in sonnigen Regionen Gestehungskosten von weniger als 8 UScents/kWh erreicht werden. Innerhalb der EU lagen die Kosten für eine kleinere P Anlage (4-20 kwp) im Mittel bei etwa für Der Eigenverbrauch wird vor allem in bereits ausgereiften Märkten immer mehr ein Thema, auf das die erteilnetzbetreiber nur langsam und mit unterschiedlichen Reaktionen (erhöhte Auflagen als Hindernisse oder auch innovative Angebote als Förderung) reagieren. Im Bereich der Speicherung gab es weiter deutliche Kostenreduktionen, sodass von einer Rentabilität noch vor 2020 ausgegangen werden kann. Die optimale Speichergrösse sollte sich dabei am Tagesbedarf orientieren. Die grössten Märkte bleiben mit China und Japan weiterhin in Asien, während auch der US Markt kontinuierlich mit etwa 6 GW weiter wächst. In der Industrie lag der Fokus auf der besseren Auslastung und der teilweisen Erneuerung der Produktionsanlagen. Schweizer Beiträge und Aussteller Die Schweiz war in Amsterdam wiederum gut vertreten. Insgesamt waren Schweizer Firmen und Forscherteams als Leiter oder Teilnehmer an 72 Konferenzbeiträgen beteiligt, was den weiterhin hohen Stand der Schweizer Photovoltaik sowohl in der Forschung wie auch in der Anwendung im internationalen ergleich belegt. Die Schweizer Beiträge umfassten 4 Plenarvorträge, 22 mündliche Beiträge sowie 46 Poster (siehe Anhang A). Der Anzahl der Schweizer Aussteller auf der Messe ist im ergleich zu Paris 2013 zwar deutlich gesunken, jedoch ist deren Anteil gesamthaft gesehen in etwa konstant geblieben. Schlussbemerkungen Die 29. Europäische Photovoltaikkonferenz war ein weiterer Meilenstein in der internationalen Konferenzwelt. Sie erlaubte einen guten Überblick über die aktuellen wissenschaftlichen Erkenntnisse und Entwicklungen, die Anwendungserfahrungen bezüglich Technik und Markt sowie die industrielle Dimension der Photovoltaik. Die Ausstellung spiegelte jedoch auch die aktuelle Situation auf dem Photovoltaik-Markt und insbesondere die schwierige Situation vor allem der europäischen Marktakteure wieder. Nächste EU P Konferenz Die nächste EU PSEC, die 30 th European Photovoltaic Solar Energy Conference and Exhibition, findet vom 14. September September 2015 in Hamburg statt. Nützliche Links: /51

9 Thin-film silicon and crystalline silicon solar cells J.-W. Schüttauf 1, E. Moulin 1, A. Faes 2, H.-Y. Li 1,2, F. Meillaud 1, and C. Ballif 1,2 1 Ecole Polytechnique Fédérale de Lausanne - EPFL Institute of Microengineering - IMT Photovoltaics and thin film electronics laboratory - Plab MC A2 304 (Microcity) Rue de la Maladière 71, 2000 Neuchâtel Phone: 0041(0) christophe.ballif@epfl.ch 2 CSEM P-Center Rue Jaquet-Droz Neuchâtel Introduction In this short report, we present some of the highlights of the 2014 EU-PSEC conference in the field of thin film silicon, crystalline silicon and module technology. Despite the fact that the general interest in thin-film Si has become smaller (as reflected in the number of sessions dedicated to this topic), several remarkably good results were presented. For singlejunction devices, new world records have been obtained for both a-si:h and µc-si:h in the last year. For a-si:h/µc-si:h tandem devices, a new world record of 12.63% was obtained at IMT. Furthermore, TEL Solar obtained an impressive stabilized module efficiency of 12.2% on Gen 5 (1.1 x 1.3 m 2 ). All these results were presented at this conference. For crystalline Si, the recent world record by Panasonic has triggered even more interest in Si heterojunction devices. Furthermore, many sessions focused on different types of high-efficiency n-type cells and modules, which are expected to strongly increase their market share in the upcoming years. Regarding cost reduction, the main trends are towards process simplification (using fewer processing steps) and to limit the use of silver in cell and module fabrication. Several very high efficiencies (in the 23-25% range) were presented, but no new world record. Regarding module technology, BIP was a popular topic in this year s PSEC. Discussions are mostly focused on the integration strategies from the perspectives of both architects and P engineers. Also the development of an international qualification standard for BIP elements is currently ongoing and requires synergetic efforts from both the building and P industries. On the module packaging materials, a trend exists that people keep searching for alternative encapsulants than EA. Due to the cost problem, at this moment EA is still unbeatable. PO is gaining more attention recently, thanks to its better PID-resistance. Yet, few c-si module producers are using PO-based encapsulants up to now. For reliability modeling, the focus is on the development of a lifetime prediction or lifetime classification test, instead of the existing qualification test. PID stays a hot topic. No new mechanistic study has been presented. Many researchers evaluated the PID resistance of different encapsulant materials. For the new module technology, the SWCT from Meyer Burger and Multi-Busbar technology from Schmid appear to be the more promising candidates for the next generation module technology for c-si based cell technology. IMT had four presentations as first author, including one plenary presentation on thin-film Si by C. Ballif. The other three oral presentations were given by J.-W. Schüttauf, E. Moulin and M. Stuckelberger. IMT also had four poster presentations (by Y. Riesen, G. Cattaneo, H.-Y. Li and M. Stuckelberger). The contribution by M. Stuckelberger won the best poster award. Furthermore, scientists from IMT were also co-author in several other contributions. CSEM had one oral presentation by A. Faes, as well as three poster presentations (by H.-Y. Li, A. Descoeudres and A. Faes) and contributed to several other oral and visual presentations. 9/51

10 Thin-film silicon solar cells There were in total this year three oral sessions and two poster sessions dedicated to the thin-film silicon (TF-Si) technology. In addition, a plenary talk was given by C. Ballif (IMT, Switzerland) who presented the status of this technology world-wide, at both the academic and industrial levels. After briefly introducing the new Microcity building and the CSEM P-Center, he highlighted the main advantages of the TF-Si technology, namely the low sales prices achievable (down to 35 /m 2 ) and the high level of flexibility for building integration (by several relevant examples). He summarized some of the main results achieved at IMT: among others, those related to the use of µc-si:f:h as absorber material (providing record photocurrent values of almost 32 ma/cm 2 ), and the implementation of the triple-junction-cell concept (giving a stable efficiency of 12.8%). He finally presented the status regarding cell and module stable-efficiency records released in the last year: the certified 12.63% cell efficiency on > 1 cm 2 obtained by IMT for micromorph cells; the 10.22% (certified) and 10.26% cell efficiencies by AIST (Japan) and FZJ (Germany), respectively, for single-junction a-si:h cells; the confirmed 11.37% efficiency obtained by AIST for µc-si:h cells deposited on a honeycomb texture. Regarding module efficiencies, he mentioned, among others, the impressive record efficiency of 12.2% achieved by TEL Solar on Gen-5 areas. Finally, he proposed an outlook, based on the further development of quadruple-junction solar cells and thin-film cells applying recrystallized silicon. J.-W. Schüttauf (IMT, Switzerland) opened the first of the parallel sessions, dedicated to the development of high-efficiency TF-Si devices. He showed thin-film triple-junction cells in two different configurations: in the a-si/a-sige/µc-si configuration, he presented an initial efficiency of 13.6% and a stabilized efficiency of 11.3%. In a-si/µc-si/µc-si configuration, efficiencies of 13.7% (initial) and 12.8% (stable) were shown. A first properly working- quadruple-junction device was also presented plus an outlook on how to achieve a stabilized efficiency of 14% in this device configuration on the short-term with building blocks currently available in the laboratory. X. Zhang (Nankai University, China) presented a 0.25 cm 2 a-si:h/a-sige:h/µc-si:h triple-junction solar cell on sputter-etched ZnO:Al with an initial efficiency of 16.1%. This result was obtained by implementing optimized p-type SiOx window layers to decrease parasitic absorption, n-type SiOx layers to redistribute spectral absorption and optimized sub-cells thickness and band gap. Unfortunately, only an I- curve was presented and no EQE data. Several upgrades were introduced to improve cell efficiency of the constituting component cells: the p-type µc-si:h layer conventionally applied at the TCO/p interface of single-junction a-si:h cells was replaced by a p-type nc-sic:h p-doped layer combined with an intrinsic a-sic:h buffer layer, resulting in a oc increase from 0.93 to A modified bandgap grading was adopted in a-sige:h solar cells, mainly leading to a FF boost from 65.5% to 68.3%, together with an efficiency gain from 7.8% to 8.2%. Finally, a photocurrent as high as 29.4 ma/cm 2 was demonstrated for 3.3-µm-thick µc-si:h solar cells on ZnO:Al applying an antireflective coating. D. Y. Kim (Delft University, Netherlands) presented their latest results on the optimization of the high bandgap (> 2 e) a-siox:h material and its implementation as absorber layer in single-junction and multijunction solar cells. By thinning the p-type a-siox:h window layer, replacing the n-type a-siox:h by a more transparent nc-siox:h layer, and thickening the absorber layer (from 150 nm to 200 nm), they were able to obtain an initial efficiency of 8.78% for single-junction cells on Asahi-U substrates. Once implemented in multi-junction solar cells, they achieved an initial efficiency of 10.9% for the micromorph configuration (200 nm for the top cell/2500 nm for the bottom cell) and 12.6% (initial) for the triple-junction configuration (80 nm/850 nm/3500 nm).. Smirnov (FZJ, Germany) showed the beneficial role of using nc-siox:h doped layers in TF-Si solar cells. In particular, the replacement of their standard n-type layer by an nc-siox:h layer boosted the photocurrent of their µc-si:h cells, leading to an efficiency of 9.7% for a 1.2-µm-thick absorber layer. Introduced in a-si:h cells, this layer mitigates the negative impact of light-induced degradation (LID), which allowed them to reach an efficiency of 10.26% (the highest reported so far, but not certified). In tandem cells, a systematical gain in photocurrent was demonstrated thanks to the implementation of such nc-siox:h doped layers; as a consequence, an efficiency of 11.8% (13.5% initial) could be obtained after 1000 h of LID. In the second parallel session on TF-Si solar cells, the focus was on light-management concepts. In this respect, A. Campa (University of Ljubljana, Slovenia) presented a way on how to improve light coupling and light trapping in a-si:h/µc-si:h tandem cells, using rigorous 3-D FEM (finite element method) simulations. Among the relevant upgrades he suggested, we noted the substitution of the conventional 2.3-µm-thick front-tco layer by a nano-imprinted glass superstrate coated with a thin IO:H layer combined with ZnO (with a thickness of 100 nm for both). With this approach, a photocurrent gain of around 0.7 ma/cm 2 (from 12.1 to 12.8 ma/cm 2 ) and 0.35 ma/cm 2 (from to 12.4 ma/cm 2 ) was forecast for the top and bottom cell, respectively, thanks to an improved light coupling and transparency of the front-tco layer. E. Moulin (IMT, Switzerland) presented a comparison of two types of back reflector (BR) schemes, the first made of the conventional dielectric-based 5-µmthick LPCD-ZnO rear electrode combined with an optically-decoupled white reflector; the second consisting of a thin LPCD-ZnO layer (~100 nm) coated with sputtered Ag. Thin-ZnO/Ag BRs were found to provide a better light trapping especially for smoother cells, i.e. cells deposited on smoother 10/51

11 front-tco electrodes and a higher lateral conductivity of the rear electrical contact. Both the improved optical and electrical properties led to a substantial efficiency gain from 9.3% to 10.0% for 1.1-µm-thick µc-si:h cells. C. Barugkin (ANU, Australia) presented results on pigmented dielectric reflector made of binder-free TiO 2 particles directly deposited by snow globe coating (SGC) at the rear of TF-Si solar cells. Interestingly, an even higher EQE response in the near-infrared wavelength region was obtained with this type of BR than with a (textured) thin-zno/ag BR design, due to lower parasitic absorption in the BR. L.. Mercaldo focused on the optical interplay between the SiOxbased intermediate reflector (IR) and the light management in tandem cells, for varying IR thicknesses and front-tco morphologies. They found that IRs with a higher refractive n should be privileged for locally flat TCOs; in contrast, IR layers with a lower n are ideal for rougher front-tco superstrates. The third parallel session on TF-Si cells was dedicated to processing and materials. In this context, J. Haschke (HZB, Germany) showed re-crystallized Si thin-film solar cells on glass with oc up to 656 m and efficiencies as high as 11.5% for cells based on a 10-µm-thick n-doped absorber layer. Two other groups showed a similar approach: one group in Jena, Germany (I. Höger et al.) and another group coming from Sydney, Australia (J. Han et al.), extending this concept to large areas, for industrial applications. In this approach, the a-si or µc-si material deposited by LPCD is entirely molten by e-beam or laser processing; It recrystallizes forming large grains, with sizes comparable to those found in multi-crystalline Si. This approach represents a fast and scalable alternative to the standard approach. S. Krause (Fraunhofer CSP, Germany) presented a precise and sensitive scribing of textured thin-film photovoltaic layers using selective femtosecond laser ablation. M. Stuckelberger (IMT, Switzerland) presented a comparison of different a-si:h materials with respect to light-induced degradation for the use as absorber layers in TF-Si solar cells. In particular, he demonstrated solar cells with wide-bandgap a-si:h showing oc values above 1, as well as cells with narrow-bandgap a-si:h providing photocurrent larger than 18 ma/cm2, and finally highlighted their different applications. The poster award in the session related to TF-Si solar cells went to M. Ghosh (FZJ, Germany) for his work on double-texture front-tco morphologies, combining 2-D periodic textures and random ZnO:Albased textures; he also showed the beneficial effect of an antireflective coating made of porous SiN deposited by flame-assisted CD at the air/glass interface of micromorph solar cells. Crystalline silicon solar cells There was still a large interest for silicon heterojunction technology (SHJ) this year at the EUPSEC in Amsterdam. Even if Panasonic was not presenting, the last world record efficiency for silicon based cell of 25.6% of the beginning of the year based on SHJ-IBC cells (>100 cm2) brings a lot of interest to this technology. Sharp presented a 25.1% efficiency, also on SHJ-IBC small cells (<4 cm2). They use photolithography and selective wet etching of the different doped layers. Benjamin Strahm of Roth&Rau Research introduced the Swiss-Inno HJT project with the initial encouraging results of 23.1 and 23.5% eff on Cz and FZ wafer, respectively (measure with Grid touch technique). The best module was measured at 307 Wp with 60 pseudo-square cells. AUOptronics show 23.1% eff (surprisingly high FF of 83% ) on 6 inch wafers as their record and 22.7% eff. for Cu plating (40 um fingers) on their pilot run and an impressive 323 Wp with a three-busbar soldered module. Choshu Industry Co describes the use of cerium-doped indium oxide (ICO) with mobilities up to 145 cm 2 /s after annealing. ICO shows higher FF values compared to ITO and higher Jsc values compared to tungsten doped indium oxide. With ICO, 23.4% eff rear-emitter cells (measured with the GridTouch from PASAN) were fabricated and show a SmartWire module of 327 Wp with 60 cells. Silevo, with tunnel oxide passivating layer, showed 23.1% cells thanks to rounded pyramids (+2.1% in oc) and Cu plating of 35 micron width fingers (+1.2% in Jsc). They reached 389 Wp module of 72 different 6 cells. ECN tested metal wrap through cells for SHJ technology, and found that the rear-emitter design works better to avoid shunts. The best cell they showed had an efficiency of 20.3% and they obtained 19.6% for a mini-module. INES Labfab show 20.1% average over 32k cells (best at 20.8%) and a record cell at 21.95%. The keynote talk from M. Hermle (ISE) was about levelized cost of electricity (LCOE), to beat mc-si with 18.5% efficiency. With the same fabrication cost, Cz p-type would need to reach 19.5% and Cz n-type 20.2%. High efficiency cells (BCBJ from Sunpower, for example) are predicted to be soon in direct competition with SHJ and TopCon cell architecture. IMEC concentrated on process step simplification for IBC by using laser ablation and screen-printing compared to photolitho with a 22.7% eff. The other approach to reduce the number of process steps is the boron-doped epitaxy (SEG). For n-type IBC the SEG can reduce the number for steps by 40% while keeping the eff at 22.8% compared to 23.1% for the photolitho baseline. SolarWorld describes the industrialization and optimization of PERC from cell to module. Initial values were 19.5% eff, whereas a 265 Wp module and a TCM loss of 5% were presented. The processes optimized were: (1) the crystal quality (low resistance material) that brings the cell efficiency to 20%, then (2) the cell front 11/51

12 (by ion implantation) which rises the efficiency to 20.5% and finally (3) the module design with half-cell and structured ribbon: TCM loss reduced to 3.5% and a module of 300 W with half-cells (laser cut) were shown. University of Konstanz shows boron oxygen defect regeneration using ns-laser for 1 sec over the cell with a long-term stability of 97% at 1 sun and 60 C. General trends are to go to co-diffusion, bifacial cells, back-contacted cells and simplified processes in general. For the metallization, the general trend is to reduce the silver consumption as it is still represents the second material cost in modules after the silicon wafer. Heraeus and Chimet propose a paste for low silver laydown. Applied-Material/Bachini shows some improvements on the dual print which increases the conductivity but also reduces the optical shadowing in the module. Merlin technology from GTAdvance Technologies presented a PbSn coated copper grid soldered at the front and the back of the busbar-less cell; the final consumption of silver can be reduced to 50 mg per cell. CSEM presented SmartWire Contacting Technology (SWCT) from Meyer Burger that changes the number of interconnecting wires to reduce the power dissipation loses in the silver finger. This enables a tremendous reduction in silver consumption down to 25 mg per SHJ cells reducing the cost of raw silver to 0.23 ct/wp. The other major trend is to use copper plating to reduce the high cost variation due to the volatility of the silver price. The standard way is to open the SiNx antireflective coating with laser ablation, then to plate Ni to form nickel-silicide (to increase the adhesion and avoid copper diffusion in the wafer), plate copper and finally use a finished layer of silver or tin. Large interest was seen during this EUPSEC for Cu plating. RENA proposes a low cost process based on Ni/Cu plating for both mc-si and mono-si with 17.7% and 19.6% eff, respectively. Hundai Heavy Industries concluded that Ni/Cu metallization is not yet cost competitive compare to silver screen-printing. AUO, Silevo and CSEM propose Cu plating for cells covered with TCO (SHJ like cells). MacDermid, ISE, ITRI, Chungnam Nat University presented their last work about Cu plating. Packaging and module design Proper evaluation methods for BIP elements BIP elements combine the functions of both photovoltaic modules and conventional building materials. The proper evaluation testing methods need to be developed to evaluate the overall performance of BIP elements, eventually towards a unified qualification standard for BIP elements. This issue has been well discussed during this EU PSEC. Kim et al. developed a comprehensive evaluation test for the BIP element as roof. The tests include P performance test, electrical safety test, fire test, wind load test and soundproof test. Maturi et al. reported a comprehensive temperature monitoring of BIP systems in the EU with different installation configurations and locations, as compared to the ground-mounted systems. They use a simplified model to describe the dependency of (T mod T amb ) on the solar irradiation, from which they calculated the equivalent thermal resistance. They found that the optimal placement of monitoring system is important for the proper T monitoring of BIP system. Pontecorvo et al. reported on the thermal transmittance measurements done on G-G BIP façades installed in Italy. They found that the transmittance of this standard configuration is higher than required by the Italian building legislation (2.6 W/(m 2 K); higher than 2.1 W/(m 2 K) ). New designs such as the replacement of an air chamber with inert gas will lead to a BIP façade element complying with legislations. Alsema and Anink developed a method to evaluate the life-cycle environmental impacts of BIP elements by integrating the material score and energy consumption indicator calculated by Dutch building codes. They clearly illustrated the environmental benefit of BIP over buildings without P elements. CIEMAT from Madrid presented their study on the optical characterization of semitransparent P modules for BIP applications. Dr. Hemmerle from TU Dresden presented their work on the evaluation of the mechanical resistance of BIP modules as construction products. They developed a modified four-point method as the suitable method for standard-size P modules. Module packaging materials Reiners et al. used simulation and experiment to show that the Saint Gobain Solar Albarino textured glass can enhance light penetration especially at high incident angle. The outdoor data showed that 3-7% more Isc can be obtained with this textured glass. In Peharz et al., the authors use both simulation and experimental approaches to study the photon recycling or trapping by the reflection of backsheet. Four types of Isovoltaic backsheets have been compared. The best one can enhance J sc by 2.1% in 60-cell standard c-si P modules. Beinert et al. showed that for EA without stabilizers, the U exposure can also result in fluorescent species in the degraded EA. In poster 1B.6.47 (Hodgson et al.), down-shifting fluorescent quantum dots were added to the packaging material on the front side. They show that this new material can enhance the Jsc by 4% as compared to nondownshifting materials. In poster 1B.6.37, Yingli in collaboration with Du Pont tested the idea of 12/51

13 using a thin ionomer encapsulant layer as the barrier to Sodium and charges. They demonstrate that by combining the thin ionomer layer and EA encapsulant, they achieve very good PID-resistance as compared to EA and PID-resistant EA. In poster 1B.6.35 by tuning the A% and additive level, STR successfully developed PID-resistant EA with similar volume resistivity as other PO-based encapsulants, while maintaining a low cost. In 5C.2.21 (Belluardo et al.), based on the outdoor monitoring data, the authors concluded that under clear sky, textured glass under study did not show a benefit over flat glass. Under non-clear sky, the benefit is trivial. In 5D.3.12, Mitsui presented their crosslinkable PO, ASCE. Compared to EA encapsulant, they claimed the ASCE is significantly PIDresistant and not corrosive to Ag fingers on the cells. In 5D.3.20, Japanese company TOYOBO presented a hydrolysis-free PE film as an alternative to common PET film used in the P backsheet. Reliability modeling In 5B.4.1, a comparison has been made on the fluorescence pattern on the c-si modules aged in different outdoor climates and indoor ALTs. From this comparison, it is found that the photochemical degradation is the driving force in fluorescence evolution. In 5B.4.3, through experimental study, a good correlation on the PET backsheet degradation behavior has been found between DH test and PCT at 120 deg C and 100% RH. This result allows even more accelerated aging test to screen backsheet material. In 5B.4.23, the authors evaluated the load cycle bending test as an accelerated test for thermal cycling test. It is concluded that the load cycle does not produce the same failure mode as TC. In 5B.4.22, the authors found that the standard TC can be split into one hot TC and one cold TC. They propose to use the hot TC as an accelerated TC for initial material/module screening tests. 5B.4.4 aims at answering the question on whether reliability of backsheets can be evaluated as a standalone film instead of within a laminated module. They conclude that for BS without barrier, standalone BS film is sufficient to study its actual degradation behavior in the module under DH exposure. 1B.6.33 compares the EA yellowing upon exposure to a U pulsed laser or fluoresecence tubes. They found that the U plused laser results in a more than 100 times enhanced yellowing rate, but the degradation process and products appear to be different as unveiled by Raman spectroscopy. In 5B.4.17, M. Koehl re-emphasized the necessity of using cycles of testing sequence (DH, TC, DH+U) to combine the major stress factors for P modules and better simulate the outdoor stresses. In 5B.4.9, the authors evaluated the effect of the EA curing time/initial gel content on the module reliability. In 5D.3.14, the degradation mechanism of c-si modules in DH was attributed mainly to the corrosion of electrical contacts. They propose that the lead-glass interfacial layer lying in between the Ag finger and the Si cell is actually the weakest point upon the attack of acidic species. New module technology In 5C.2.38, SCHMID reported the reliability study of their patented Multi-Busbar modules. They did not reveal the type of encapsulant used, but it is a G-BS module. The Multi-Busbar modules passed the high-pressure cooker test and TC with large margin, and showed better robustness as compared to the 3-Busbar modules. 1B.6.42 illustrates that the structured ribbon applied by gluing, i.e. light capturing ribbons, can enhance the Jsc by about 1.64% compared to soldered flat ribbon. In 1B.6.45, a similar observation was reported with the light capturing ribbon. Additionally, a thermoplastic encapsulant, likely to be PO based, was reported to be the best in PID-resistance compared to EA and PB. Bi-facial module designs have been the topic of several contributions, including 5C.2.11 on n-type c-si. Meyer Burger, in team with EPFL and CSEM, also presented several contributions on their patented SmartWire Connection Technology, including 5DO.16.3, 1B.6.36, and 2C PID 5D.3.2 presented the PID-resistance of modules encapsulated with different encapsulants, including several EA, PO and PB. It shows that the degradation rate under PID correlates well with the volume resistivity of the encapsulants. Interestingly, they also presented that the volume resistivity changes significantly before and after heat treatment. For one type of EA, the change can be nearly two orders of magnitude. 5D.3.3 used experimental data to confirm that the leakage current from P modules under PID depends on T following an arrhenius equation, while depending on RH following an exponential relationship. In 5D.3.9, the authors from AIST show that the PID-resistant EA exhibits much higher PID resistance than standard EA. 5D.3.10 compared the PID resistance of different encapsulants, including six EAs and two POs. They showed that two PO are all PID resistance. Three EA encapsulants showed a similar resistance as PO, while the other three showed much lower resisitance values. 5B.2.63 reported a fast detection method of the PID-affected P modules deployed in the field by flight therography. The chess board pattern is a feature pointing at PID. 13/51

14 II I compound thin film solar cells A. N. Tiwari Laboratory for Thin Films and Photovoltaics, EMPA Swiss Federal Laboratories for Materials Science and Technology Überlandstrasse 129, CH-8600 Dübendorf Tel +41 (0) , Fax +41 (0) ayodhya.tiwari@empa.ch General comments 24 oral presentations and more than 120 posters on thin film solar cells based on II-I, I-III-I and I-II- I-I chalcogenide absorbers did show that the intensive research of these technologies continues resulting in new record efficiencies on both laboratory-scale solar cells and commercial modules. The definitive highlight was the announcement of the new world record efficiency of 21.7% for CIGS solar cells by ZSW currently the highest efficiency for any thin film technology, exceeding 21.0% for CdTe and 12.6% for CZTSSe. The Potassium doping of CIGS was considered as one key enabler of high-voltage CIGS cells, whereas the alternative Zn(O,S) buffer layers and surface passivation concepts were discussed in several talks as means to achieve Cd-free and more efficient modules, both on rigid and flexible substrates. The Student Award went to H. Yoo from Univ. of Erlangen-Nuremberg for her investigations of reaction pathway for the formation of CZTSe thin films, whereas B.L. Williams from the Eindhoven Univ. of Technol. received a poster award for Identifying Parasitic Current Pathways in CIGS Solar Cells by Modelling Dark J Response. High Efficiency Thin Film Solar Cells 3AO.4.1 A 24.2%-Efficiency III-/CuInGaSe Mechanical Stacking Multi-Junction Solar Cells Using Semiconductor Bonding Method K. Makita et al. (AIST, Tsukuba, Japan) Mechanical stacking of epitaxial lifted-off GaAs top cell and CIGS bottom cell is made by a direct bonding method involving the use of conductive Pd nanoparticles arrays embedded in block copolymer template. Chemical mechanical polishing of the CIGS cell is used to reduce the surface roughness. The absorption losses due to the particles are below 2%. By using a triple junction involving GaInP/GaAs top cell, an efficiency of 24.2% was achieved. Main losses compared to theoretical limit are due to losses in oc. Further improvement is expected to lead to 28% efficient devices. 3AO.4.2 CIGS Thin-Film Solar Cells with an Improved Efficiency of 20,8% S. Paetel et al. (ZSW, Stuttgart, Germany) ZSW shows much statistical data on the influence of KF post-deposition treatment as function of average Cu and Ga content, and where they obtain maximum efficiencies. The KF PDT pushes the saturation of oc with increasing bandgap up to a Ga content of 0.49, and they observe a possibly higher FF due to the KF PDT for cells with efficiency above 19%. They report a higher doping due to KF PDT and a lower Na content in absorbers with a too high amount of K. A recent new processing step has allowed them to increase their record efficiency from 20.8% to 21.7%, what represents the new CIGS world record efficiency. They show many cells with efficiency clearly above 21%, supporting the good homogeneity of their process. 3AO.4.3 Sodium and Potassium Post-Deposition Treatments of Cu(In,Ga)Se 2 Absorbers Evaporated at Low Temperature P. Reinhard et al. (EMPA, Dübendorf, Switzerland) Empa investigated the influence of sequence and substrate temperature for the addition of alkali in a post-deposition treatment. Whereas only little influence of the sequence for NaF and KF addition is observed, a significant degradation of the oc and FF is observed when varying the temperature during deposition. This effect is attributed to a modified interface region and alkali interactions, and is most critical for deposition of KF at a higher temperature than the usual 350 C. Comparison of different samples is given in view of their electronic properties, and show that no direct proof for interface re- 14/51

15 combination can be derived, even if many signs hint towards this direction. A detailed mechanism to explain why the temperature is so crucial is still missing at the moment. 3AO.4.4 High Efficiency Ultra Thin CdTe Absorbers by Physical apor Deposition A. Salavei et al. (University of erona, Italy) Optimization of the deposition process of the different layers is shown for CdTe cells with a reduced absorber thickness. Highest efficiency of 13% with an absorber of 1.5-µm thickness is reported. CdCl 2 activation treatment and amount of Cu should be carefully controlled. Lower performance of cells with thinner absorbers can be attributed to reduced light absorption, whereas it is not affected by the smaller CdTe grains. 3AO.4.5 Cd-Free CIS Thin Film Solar Modules at 17% Efficiency J. Palm et al. (AANCIS, Munich, Germany) New materials and processes at AANCIS are shown, with a focus on how they were able to reach 17.1% efficiency with a Cd-free CIS solar module (30x30 cm 2, aperture area 667 cm 2 ) Introduction of an In x S y buffer layer instead of CdS, as well as a multilayer Mo back electrode have played a great role in their recent progress. The RTP selenization process was also optimized by using reflection spectroscopy as absorber growth control. 3AO.4.6 Manufacturing of High Efficiency CIGS Modules at High Deposition Rates P. Kratzert, et al. (Solibro, Bitterfeld-Wolfen, Germany) Solibro showed several aspects of their CIGS technology that can yield up to 21% efficiency record cell, especially their efforts in increasing the deposition rates during their single stage coevaporation process (up to 600 nm m/min). They announce a total area efficiency above 13% in production, and produced about 200 MW p since Their latest advancements were a better utilization of incoming photons by reducing the interconnect area, the reflection losses, and switching to a B:ZnO TCO deposited by LPCD with possible metallic grid. 3CP.1.2 Keynote Presentation: Current Status and Future Prospect of CIS-based Thin-Film P Technology in Solar Frontier K.K. K. Kushiya (Solar Frontier, Atsugi, Japan) A broad overview of Solar Frontier activities was given. Their technology is based on Cd-free, high efficiency CIGS solar cells, with efficiency up to 20.9%. They have 3 production plants summing up to about 1 GW p solar module, with a maximum power of 170 W/module. A 4th production plant will be built in 2015 with a production capacity of W products. In a near future they see a necessity for 16% modules, whereas current level of production averages about 14.6%. Main difficulties in increasing the efficiency are seen in dealing with a vertical carrier flow in cells whereas in modules the flow is rather horizontally. Novel Concepts and Materials 3AO.5.1 Present Status and Future Prospects of CBD-ZnS Buffer Layers for High Efficiency Chalcopyrite Cu(In,Ga)Se 2 Based Thin Film Solar Cells N. Naghavi et al. (CNRS, Chatou, France) This presentation gave an overview of some latest findings in solving the problems of metastabilities and lower performance when replacing the standard CdS buffer layer with a ZnOS buffer layer. Studies on the CIGS/buffer as well as buffer/tco interface were conducted to change the band alignment or the metastable behavior. By changing the bandgap of the CIGS at the interface, an optimum in oc was found for a CdS buffer layer, whereas oc keeps increasing for cells with a ZnOS buffer. Moreover, no metastable behavior was observed if no oxygen was used at the beginning of the ZnMgO sputtering or if the bath chemistry was modified. 3AO.5.2 Passivation of Interface Defects in CIGS-Based Thin-Film Solar Cells D. Hariskos et al. (ZSW, Stuttgart, Germany) The influence of formation and passivation of Se deficiencies by O or S was discussed. Detailed analysis of CIGS surfaces subjected to either air annealing or annealing with sulphur was shown. The goal was to change the surface termination from selenic to oxidic, which then showed a better buffer coverage during growth in a chemical bath. This was given as a reason for a possible decrease of the buffer layer thickness. 15/51

16 3AO.5.3 Flexible Cu(In,Ga)Se 2 Solar Cells with Chemical-Bath Deposited Zn(S,O,OH) Buffer Layers Y.E. Romanyuk et al. (EMPA, Dübendorf, Switzerland) First results were shown when trying to replace the CdS buffer layer with a ZnOS buffer layer, especially in view of combining lower parasitic losses in the buffer layer with improved junction quality usually observed due to a KF PDT. Possible ways of reducing metastable behavior by replacing i-zno with ZnMgO, a thicker ZnOS and divers annealing steps before or after TCO deposition were shown. A flexible mini-module with efficiency of 11.8% was reported. A Cd-dip before the ZnOS buffer layer deposition seems effective in reducing the oc loss due to the use of the alternative buffer layer. 3AO.5.4 Flexible Cu(In,Ga)Se 2 Thin Film Solar Cells for Space Applications - Recent Results from a German Joint Project C.A. Kaufmann et al. (HZB, Berlin, Germany) Development of flexible CIGS solar cells on polyimide substrate is shown, with a focus towards space application and low weight. Sodium is added by a post-deposition treatment or directly in the sputtered back contact. Main challenge is the sample transfer between the project partners, as well as an optimized low-temperature CIGS growth and buffer layer (In2S3) suitable for the sun spectrum in space. Highest cell efficiency at the moment is 17.9%. 3AO.5.5 Roll-to-Roll Manufacturing of High Efficiency and Low Cost Flexible CIGS Solar Modules P. Bolt et al. (TNO, Eindhoven, The Netherlands) Within an EU-project called R2R-CIGS progress in transferring static deposition processes towards in line deposition equipment is shown, with the final aim of having pilot lines able to produce modules on flexible substrates in a roll-to-roll configuration. CIGS is grown by a low-temperature multistage process and yields up to 16.9% mini-module efficiency at Empa. Spatial ALD equipment for growth of ZnOS, automatic laser scribing machine prototype and different moisture protection approaches are discussed. 3AO.5.6 Enhanced Performance of Ultra-Thin Cu(In,Ga)Se 2 (CIGSe) Solar Cells by Deposition at Low Substrate Temperature and Incorporation of Light Trapping Structures G. Yin et al. (HZB, Berlin, Germany) Strategies to reduce back contact recombination and incomplete absorption in cells with reduced absorber thickness are discussed. Dielectric nanoparticles (SiO 2 ) are used for anti-reflection at the ZnO/air interface, and as back scattering at CIGSe/Mo interface. Improvements in efficiency from 11.2 to 13.1% are reported for cells with an absorber of 500 nm, mainly due to a higher current density when using nanoparticle arrays approach. Characterisation of Chalcogenide Thin Film Solar Cells 3AO.6.1 Large Area 16% Efficiency Cu(InGa)(SSe) 2 Solar Module with Enhanced Bulk and Interface Characteristics D. Lee et al. (Samsung SDI, Yongin, Republic of Korea) Investigation of the influence of Cu content and Ga content on the photovoltaic parameters of solar cells with absorbers grown by sputtering and selenization/sulphurization is reported. Below a CGI of 0.9, no interface recombination is usually observed. Results are backed up by several material and electronic characterization techniques. By increasing the homogeneity of the CGI over the module area, a 16% record module was obtained (230W, 160 x 90 cm 2 ). 3AO.6.2 Impact of the Ordered acancy Compounds on the Efficiency of Cu(In,Ga)Se 2 Solar Cells: Raman Scattering Assessment of Electrodeposited Devices C. Insignares-Cuello et al. (IREC, Barcelona, Spain) Different excitation wavelengths have been used in order to characterize layers in finished solar cells by Raman spectroscopy, in view of developing a method compatible with large area processing. Experimental evidence of the OC phase on the efficiency of electrodeposition based devices is claimed, based on the attribution of a Raman peak attributed to the OC phase. There appears to have an optimal concentration of OC in the surface. 16/51

17 3AO.6.3 Regression Analysis of Capacitance Transients: a Method to Obtain Information on the Electric Structure of Thin-Film Solar Cells J. Lauwaert et al. (Ghent University, Gent, Belgium) Advanced electronic characterization techniques based on capacitance transients are used to assess the electronic behavior of thin film solar cells. DLTS experiments with normal and inverted pulses allow separating signals of non-ideal contacts from those of defects. Fitting parameters can then be used in device modeling. 3AO.6.4 Solution of Roll-over-Shaped J- Characteristics of Ag(In,Ga)Se 2 Solar Cells T. Umehara et al. (Tokyo Institute of Technology, Japan) The usually observed roll-over-shaped J- curve of AIGS solar cells is reported to be due to a different factor than a Schottky contact at the back interface. It is rather attributed to a much lower hole density in the AIGS layer, and a change to n-type semiconductor material near the back contact due to injected electrons. Solutions to the is problem are either a higher Se to metal fluxes to increase the hole density, or the insertion of a p + type layer such as PEDOT:PSS at back interface. 3AO.6.5 Rapid and Accurate Measurement of Ideality Factor and Parasitic Resistances of CIGS Solar Cells Y.-S. Kim et al. (Samsung SDI, Cheonan, Republic of Korea) The Sunshade method is introduced, where diode characteristics can be extracted by measuring I- curves under different illumination conditions. This method gives reliable values for series and shunt resistance, as well as n-factor, but is not applicable for devices with a shunt resistance below 2000 Ωcm -2. 3AO.6.6 Study of Metastable Effects in CIGS Solar Modules during Illumination and Current Injection. Huhn et al. (Forschungszentrum Jülich, Germany) Modules from Manz show an increased oc under illumination of about m within 10 hours, which can be even faster at higher temperature. After light soaking, a much brighter electroluminescence signal is observed. Illumination and dark carrier injection improve the CIGS module performance. Kesterite 3BO.7.1 Printing of Large Area Flexible CZTS Solar Modules A. Neisser et al. (Crystalsol, ienna, Austria) An overview of Crystalsol technology is given, where they develop flexible photovoltaic membranes based on the monograin membrane technology: crystalline semiconductor powder with a typical size of µm is used as a layer, and fixed by a polymer film. Best module efficiency of 5.8% is reported, and highest cell efficiency of 8.4% was achieved. They have demonstrated a fully functional R2R line, with up to 4m/min printing speed. 3BO.7.2 Enhancement of Carrier Collection in Cu 2 ZnSn(SeS) 4 Solar Cell with Hybrid Buffer Layer H. Hiroi et al. (Showa Shell Sekiyu, Atsugi, Japan) Enhancement of carrier collection in CZTS solar cells is reported by using a hybrid buffer layer consisting of CdS and In 2 S 3, both layers deposited by chemical bath. Improvement was not only due to oc increase, but also to a higher Jsc. Highest efficiency of 12.7% was achieved, whereas for a Cd-free buffer layer an efficiency of 9.3% was achieved. 3BO.7.3 Different Reaction Pathway for the Formation of Cu 2 ZnSnSe 4 Thin Film from Different Stacking Order of Elemental Layers H. Yoo et al. (University of Erlangen-Nuremberg, Germany) A very detailed analysis of the reaction leading to the formation of CZTS phase was given, starting from different stacking layers annealed at various temperatures. It is found that mainly ZnSe phase is critical to remove as soon as it has formed. 17/51

18 3BO.7.4 Optimization of CdS Buffer Layers for Improved CdS/Cu 2 ZnSnSe 4 Hetero-Junctions with 8.2% Efficiency M. Neuschitzer et al. (IREC, Barcelona, Spain) Acceptor like defects states in CdS are modifying the absorber/buffer band alignment and result in a red kink and crossover, probably due to a Cd. Those can be partially removed by light soaking, reducing series resistance and improving the FF. A change in the CdS growth process improved the Cd incorporation into the film, with a reduction of light active defects and removal of crossover and red kink. 3BO.7.5 Light Soaking Effect in Cd-Free Cu 2 ZnSn(S,Se) 4 -Based Solar Cells L. Grenet et al. (CEA, Grenoble, France) Substantial light soaking treatment was necessary to achieve 5.8% efficiency with a ZnOS buffer layer, compared to 7% with a CdS buffer layer. A lower short circuit current is measured, and attributed to a barrier at the buffer/absorber interface. 3BO.7.6 Exploration of Surface Potential Distribution for Identifying Secondary Phases on Cu 2 ZnSn(S,Se) 4 Thin-Films (n = 9.1% Conversion Efficiency) Grown by Sputtering G. Kim et al. (Ewha Womans University, Seoul, Republic of Korea) Work function of surface of CZTS absorbers was measured by Raman spectroscopy and Kelvin-probe force measurement to identify secondary phases. CZTSe, CTSe, ZnSe and MoSe 2 are identified. isual presentations 3D.1.6 Transparent Conductors with Metallic Grids on CIGS: Modeling and Experiments J. van Deelen et al. (TNO, Eindhoven, The Netherlands) Design rules for optimal power have been developed based on simulation for using transparent conductors with metallic grids. 3D.1.19 Characteristics of Sodium Distribution in Bridgman CuInSe (2+x) by XPS S. Park et al. (McGill University, Montreal, Canada) Single crystals CIS have been used in order to help understand the role of elementary sodium in chalcopyrites. The results support the theory that the improvement of P performance by Na addition in CIS and CIGS solar cells is due to enhancement of the formation of a n-type low Cu ternary at the surface, therefore lowering the interface recombination. 3D.1.26 On the Importance of the Back Contact for CIGS Thin Film Solar Cells T. Ott et al. (Ulm University of Applied Sciences, Germany) The phototransistor model can explain the anomalies observed for CIGS solar cells at low temperature, based on a Schottky barrier at the back contact. An approach to determine the height of this barrier was shown and complemented by simulations. 3D.1.33 Investigation of a K-Doped Molybdenum Back Contact for CIGS Solar Cells W. Hempel et al. (ZSW, Stuttgart, Germany) The use of potassium as dopant in CIGS solar cells is one of the hot topics in the last years. Usually added after growth of the CIGS layer, here it was directly incorporated in the back contact. 3D.2.1 Assessment of All-Laser Scribing Processes and Laser Equipment for High Throughput Industrial Patterning of CIGS Thin Film Solar Modules A. Burn et al. (BUAS, Burgdorf, Switzerland) By optimizing thin film solar cell growth and laser patterning, a module with a certified efficiency of 16.6% was processed. An approach allowing supplier and end-user to assess the laser scribing equipment quality has been developed in parallel. 3D.2.3 Chemical Bath Deposited i-zno/zno:al Window Layers on CIGS Solar Cells P. Fuchs et al. (EMPA, Dübendorf, Switzerland) A 14.1% efficient CIGS solar cell with a chemical bath deposited window layer is reported, where the losses compared to a reference cell with standard vacuum-based TCO layer can be reduced by applying a thicker CdS buffer layer. Proper encapsulation is necessary to avoid any degradation of the TCO. Similar transmission quality factors are obtained for vacuum and non-vacuum based Al:ZnO. 18/51

19 3D.2.33 Identifying Parasitic Current Pathways in CIGS Solar Cells by Modelling Dark J Response B.L. Williams et al. (Eindhoven University of Technology, The Netherlands) An equivalent circuit model was developed to describe dark J- characteristics of CIGS devices, accounting for different types of shunt mechanisms. This model can be used for rapid diagnosis of shunting in low efficiency devices. 3D.2.62 High Efficiency P Devices from Non-acuum Solution Processed CIS Absorbers Enabled by a Reduction in Carbon Impurities in the Light Absorbing Layer S. Whitelegg et al. (Nanoco Technologies, Manchester, United Kingdom) Low density Mo as back contact can act as a sink for impurities during crystal growth from nonvacuum based precursors. 15% efficiency is achieved using an organic nanoparticle (ternary or quaternary) ink coated absorber. 19/51

20 P Module performance, testing, qualification and certification BIP Building Integrated P T. Friesen, M. Marzoli, A. irtuani, R. Rudel SUPSI - DACD-ISAAC Scuola Universitaria Professionale della Svizzera Italiana ia Trevano, CH-6952 Canobbio Tel. +41 (0) Fax +41 (0) thomas.friesen@supsi.ch The latest topic for the reliability of P modules regards the soiling in desert climate. PI Berlin (T. Weber et al.) and some posters presented an analysis of the energy losses due to sand and new test methods to simulate the soiling characteristics indoor. The interest in the prediction of lifetime and reliability issues of P systems is increasing. An oral presentation of Jordan et al. (NREL) presented the results of a detailed degradation analyses over the world and S. Kurtz et al. (NREL) presented the new standards for different climate conditions to be introduced in future. A.irtuani et al. (SUPSI): a simple approach to model the performance of amorphous silicon P modules under real conditions based on aggregate daily solar/meteo parameters and reduced series of indoor testing (power, temperature coefficients, spectral-response, angle-of-incidence) is extended to cover the modelling of the energy performance of this technology for different geographical locations in Europe, using as solar/meteo input parameters satellite data provided by GeoModel Solar. The work confirms, in a quantitative way, that a-si is a technology more suited to warmer climates, and that on sunny days at high latitudes the main loss mechanisms are constituted by spectral effects, which become very serious in winter time. The topic of the characterization of bifacial solar modules is covered in the presentation of B. van Aken et al. (ECN), who compare indoor flash testing and outdoor test procedures. The challenges and main issues required in order to get reproducible and comparable measurements are discussed. M. Schweiger et al. (TU-Rheinland) gave a talk on the determination of the angular characteristic (AOI) of P modules by using an indoor characterization method based on a flasher. The main challenges compared to outdoor characterization are reviewed. The effect of AOI on the annual energy yield of modules during field exposure was reviewed by U. Yusufoglu et al. (RWTH) in the same session. D. Jordan et al. (NREL) gave a speech on reliability and geographic trends of P systems in the USA, where the energy performance of the P plants and their durability are correlated to the area and the year of installation and to the occurrence of local phenomena such as e.g. dust storms or frequent lightnings. S. Kurtz et al. (NREL) presented an amendment to the existing IEC standards with the proposal of covering different climate conditions (tropical, arid, temperate, etc.), in future standards. PID (Potential Induced Degradation) is a degradation mechanism, which is becoming perceived as a very serious threat by the P community, particularly due to the high potentials experienced by some modules in larger strings of P systems, which are continuously increasing in size. An entire session was dedicated to this problem (and in addition several posters). A talk given by P. Lechner et al.(zsw) addressed the issues of designing a correct indoor test procedure - with reference to the relevant draft standard - and the limits of indoor testing compared to more realistic outdoor test conditions. Another talk given by P. Borowsky et al. (Avancis) suggested countermeasures to be adopted in the design phase of the module by the CIGSS manufacturer to prevent the occurrence of the PID phenomena in the field. Details are very vague, but include wider (and cleaner) module s edges, use of different encapsulate materials, avoiding the use of frames. Moreover, a model for PID, and a correlation between laboratory tests and outdoor occurrence were demonstrated by C. Taubitz et al. (Hanhwa Q-cells). An electrical analysis and characterization (LBIC and Electroluminescence) of c-si P modules after 20 years of field exposure were shown by A. Pozza (JRC) and correlated to the power degradation of 20/51