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

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...

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Bibliographic Details
Published in:Materials 2017-03, Vol.10 (3), p.245
Main Authors: Hengst, Claudia, Menzel, Siegfried B, Rane, Gayatri K, Smirnov, Vladimir, Wilken, Karen, Leszczynska, Barbara, Fischer, Dustin, Prager, Nicole
Format: Article
Language:English
Subjects:
Bilayers
Channeling
Coatings
Crack propagation
Cracks
Electrical properties
Failure
Grain growth
Indium tin oxides
Mechanical properties
Microstructure
Modulus of elasticity
Morphology
Multilayers
Photovoltaic cells
Polyethylene terephthalate
Silicon
Solar cells
Strain analysis
Substrates
Tensile stress
Thickness
Thin films
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Summary: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.
ISSN:1996-1944
1996-1944
DOI:10.3390/ma10030245