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Materials 2017, 10(3), 245;

Mechanical Properties of ZTO, ITO, and a-Si:H Multilayer Films for Flexible Thin Film Solar Cells

IFW Dresden, SAWLab Saxony, Helmholtzstrasse 20, D-01069 Dresden, Germany
IEK5-Photovoltaik, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
TU Dresden, Semiconductor and Microsystems Technology Laboratory, D-01062 Dresden, Germany
Fraunhofer Institute for Electron Beam and Plasma Technology, Winterbergstrasse 28, D-01277 Dresden, Germany
Author to whom correspondence should be addressed.
Academic Editor: Fu Hsiang Ko
Received: 10 January 2017 / Revised: 8 February 2017 / Accepted: 24 February 2017 / Published: 1 March 2017
(This article belongs to the Special Issue Stretchable and Flexible Electronic Materials & Devices)
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The behavior of bi- and trilayer coating systems for flexible a-Si:H based solar cells consisting of a barrier, an electrode, and an absorption layer is studied under mechanical load. First, the film morphology, stress, Young’s modulus, and crack onset strain (COS) were analyzed for single film coatings of various thickness on polyethylene terephthalate (PET) substrates. In order to demonstrate the role of the microstructure of a single film on the mechanical behavior of the whole multilayer coating, two sets of InSnOx (indium tin oxide, ITO) conductive coatings were prepared. Whereas a characteristic grain–subgrain structure was observed in ITO-1 films, grain growth was suppressed in ITO-2 films. ITO-1 bilayer coatings showed two-step failure under tensile load with cracks propagating along the ITO-1/a-Si:H-interface, whereas channeling cracks in comparable bi- and trilayers based on amorphous ITO-2 run through all constituent layers. A two-step failure is preferable from an application point of view, as it may lead to only a degradation of the performance instead of the ultimate failure of the device. Hence, the results demonstrate the importance of a fine-tuning of film microstructure not only for excellent electrical properties, but also for a high mechanical performance of flexible devices (e.g., a-Si:H based solar cells) during fabrication in a roll-to-roll process or under service. View Full-Text
Keywords: silicon-based solar cells; flexible substrates; ITO; multilayers; mechanical properties silicon-based solar cells; flexible substrates; ITO; multilayers; mechanical properties

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Hengst, C.; Menzel, S.B.; Rane, G.K.; Smirnov, V.; Wilken, K.; Leszczynska, B.; Fischer, D.; Prager, N. Mechanical Properties of ZTO, ITO, and a-Si:H Multilayer Films for Flexible Thin Film Solar Cells. Materials 2017, 10, 245.

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