© Fraunhofer IVV

Multilayer barrier structures on ETFE substrate filmsOliver Miesbauer, Mira Pfrogner, Cindy Steiner, John Fahlteich, Klaus Noller

AIMCAL Web Coating & Handling Conference Europe

Dresden, May 31, 2016

© Fraunhofer IVV

Multilayer barrier structures on ETFE substrate films

Multilayer barrier concept

Climate stability

Dimensional stability of ETFE films

Permeation through mechanically stressed ZTO coated ETFE

films

ETFE films with improved dimensional stability

© Fraunhofer IVV

Barrier requirements of thinfilm photovoltaics

Source: Fraunhofer ISE

Source: R. Pätzold, Belectric OPV

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Inorganic barrier layers Evaporated or sputtered transparent oxides

Hybrid polymeric layers (ORMOCER) Application by wet chemical coating

Left: Magnetron sputter deposition (Fraunhofer FEP)Right top: ORMOCER (Fraunhofer ISC)Right bottom: Wet chemical coating (Fraunhofer IVV)

Barrier layers on polymeric substrate films

© Fraunhofer IVV

Barrier effects in multilayer structures

Decoupled defects ⇒ Tortuous path Extended lag time of permeation Reduced mechanical stress

Left: Tortuous path effect. Right: Simulation result.Figures: O. Miesbauer, Fraunhofer IVV

Alternating inorganic and polymeric layers

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PET Melinex / ZTO / ORMOCER / ZTO WVTR: (2.0 ± 1.2)⋅10-4 gd-1m-2 at 38°C, 90% r.h. Roll-to-roll production

Fraunhofer POLO high barrier film

Left: Fraunhofer POLO barrier film structureRight: WVTR values measured for POLO barrier film (Fahlteich et al., LOPE-C 2013)

© Fraunhofer IVV

Polyester films ⇒ degradation by UV and humidity Concepts for UV stable substrate films Protection of the substrate by UV blocking coating Improved UV stability of polyester due to additives Intrinsically UV stable films

ETFE ⇒ excellent resistance against UV and weathering

Climate stability

Facade of Allianz Arena with ETFE film panels (Source: Wikipedia)

© Fraunhofer IVV

Encapsulation film

SpecificationInorganic barrier layers

Weathering and UV testsAntireflection

Substrate selection andoptimization

R2R lacquer application andprocess adaption

Weathering and UV stablelacquers

Smoothing and adhesionpromoting layers

Project flex25

Source: J. Fahlteich

The project is funded by the German Federal Ministry of Education andResearch within the programme: Validierung des Innovationspotenzials wissenschaftlicher Forschung – VIP under no. 03V0224

© Fraunhofer IVV

ETFE: low dimensional stability at elevated temperature⇒ Strain of ETFE film during roll-to-roll deposition of ORMOCER:

120°C in combination with tensile stress⇒ Formation of cracks within inorganic layers

a W.A. MacDonald, in: C. Brabec, V. Dyakonov, U. Scherf (eds.), Organic Photovoltaics, Wiley-VCH, 2008, 471–489b G. Guerra et al., Die Makromolekulare Chemie 194 (1993) 2, 389–396Right: Materials Today 9 (2006) 4, 38-45

Dimensional stability of ETFE films

Young‘s modulus/ Nm-2

23°C 120°C

PET a 4⋅109 2⋅109

ETFE b 5⋅108 1⋅108

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ETFE: Significant strain in machine direction and shrinkage in transverse direction at 120°C

Dimensional change in machine direction: for ETFE one order of magnitude higher than for PET

Dimensional change of ETFE films in the R2R lacquering machine

Glass transition of ETFE: 90°C

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Dimensional change is significantly reduced if ETFE film was already stressed in a previous process, e.g. application of primer layer

⇒ Heat stabilization of ETFE film

Dimensional change of ETFE films in the R2R lacquering machine

Conditions for pre-stressing

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Mechanical stress of ETFE / ORMOCER / ZTO (150 nm)⇒ Increase of oxygen permeability by two orders of magnitude; similar on top of

PVDF and ECTFE⇒ Barrier loss of ZTO due to dimensional change of substrate film

Permeation through mechanically stressed ETFE barrier films

ETFE

ORMOCER

ZTO

© Fraunhofer IVV

Application of ORMOCER on ETFE / ORMOCER / ZTO (150 nm)⇒ No significant improvement of oxygen barrier due to ORMOCER

⇒ Contrast: Barrier performance of PET / ZTO / ORMOCER better by two orders of magnitude

Permeation through mechanically stressed ETFE barrier films

ETFE

ORMOCER

ZTOORMOCER

© Fraunhofer IVV

Reduction of dryer temperature or web tension Reduction of ZTO thickness Improvement of the dimensional stability of ETFE films

How to avoid barrier loss of inorganic layers during wet chemical coating process

Source: Fahlteich et al., Mechanical Durability of Single And Multi Layer Permeation Barriers on Flexible Substrates, 15th Inter-national Conference on Plasma Surface Engineering, Garmisch-Partenkirchen, 2012

© Fraunhofer IVV

Permeation through mechanically stressed ETFE barrier films – Influence of ZTO thickness Mechanical stress of ETFE / ORMOCER / ZTO in lacquering machine Barrier loss of ZTO (160 nm) at 80°C or 120°C and of ZTO (50 nm) at 120°C No barrier loss of ZTO (50 nm) at 80°C

ETFE

ORMOCER

ZTO

© Fraunhofer IVV

Permeation through mechanically stressed ETFE barrier films – Influence of ZTO thickness Mechanical stress of ETFE / ORMOCER / ZTO (50 nm) in lacquering machine

at 120°C ⇒ Loss of barrier performance ORMOCER application ⇒ Improvement of barrier performance

ETFE

ORMOCER

ZTOORMOCER

© Fraunhofer IVV

Permeation through mechanically stressed fluoro-polymer barrier films

Fluoropolymer / ORMOCER / ZTO (50 nm) / ORMOCER

QO2 / (cm3⋅d-1⋅m-2⋅bar-1)(23°C, 50% r.F.)

WVTR / (g⋅d-1⋅m-2)(38°C, 90% r.F.)

ETFE (100 µm) < 0.1 0.06ECTFE (50 µm) < 0.1 0.04PVDF (80 µm) < 0.1 0.04

WVTR / (g⋅d-1⋅m-2)(38°C, 90% r.F.)

0.002

⇒ High barrier structure on top of ETFE filmETFE

ORMOCER

ZTO (50 nm)ORMOCER

ZTO (50 nm)

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Film stretching Lamination with PEN film ⇒ promising results

Improved dimensional stability of ETFE films

Source: Brückner Maschinenbau

Source: MacDonald et al., Journal of the SID 15/12 (2007), 1075-1083

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Film, mechanically stressed at 120°C QO2 / (cm3⋅d-1⋅m-2⋅bar-1)(23°C, 50% r.h.)

ETFE / ORMOCER / ZTO (160 nm) 67PEN / ETFE / ORMOCER / ZTO (150 nm) < 0.4

WVTR / (g⋅d-1⋅m-2)(23°C, 85% r.F.)

PEN / ETFE / ORMOCER / ZTO / ORMOCER / ZTO 0.002 – 0.003

Permeation through mechanically stressed PEN / ETFE barrier films

⇒ Dimensional stability of ETFE improved by lamination withPEN film

⇒ High barrier structure on top of ETFE film, also with 150 nmthick ZTO layers

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Conclusions

Fluoropolymer films: climate stability but dimensional change in roll-to-roll processes

⇒ Damage of barrier layers Adjusting process parameters and layer thicknesses Lamination of fluoropolymer with PEN film⇒ High barrier films based on fluoropolymers⇒ Equipment of fluoropolymer films with functionalities like

barrier, electrical conductivity, UV protection … for long term outdoor applications, e.g. for OPV modules and displays in building and automotive sector

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Acknowledgement

Eva Heidenreich, Intzi Moufti Chalil, Veronika Prusko, Ulrich Galster, Mira Pfrogner and the members of the Fraunhofer IVV for the coating trials and material characterizations

Cindy Steiner, John Fahlteich for the sputtered ZTO layers Sabine Amberg-Schwab, Karl Deichmann, Mark Mirza for the

ORMOCER lacquers The project partners and Rainer Brandt, Sandra Kiese, Esra

Kucukpinar, Matthias Reinelt, Klaus Noller for fruitful discussion This work was part of the flex25 project funded by the BMBF within the

programme Validierung des Innovationspotenzials wissenschaftlicherForschung – VIP under no. 03V0224.

© Fraunhofer IVV

Thank you for your attention!

Dipl.-Phys. Oliver Miesbauer M.Sc., Fraunhofer IVVPhone: +49(0)8161/491-522Email: oliver.miesbauer@ivv.fraunhofer.de