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Title: Encapsulation and backsheet adhesion metrology for photovoltaic modules

Abstract

Photovoltaic modules are designed to operate for decades in terrestrial environments. However, mechanical stress, moisture, and ultraviolet radiation eventually degrade protective materials in modules, particularly their adhesion properties, eventually leading to reduced solar cell performance. Despite the significance of interfacial adhesion to module durability, currently there is no reliable technique for characterizing module adhesion properties. We present a simple and reproducible metrology for characterizing adhesion in photovoltaic modules that is grounded in fundamental concepts of beam and fracture mechanics. Using width-tapered cantilever beam fracture specimens, interfacial adhesion was evaluated on relevant interfaces of encapsulation and backsheet structures of new and 27-year-old historic modules. The adhesion energy, Gc [J/m2], was calculated from the critical value of the strain energy release rate, G, using G = βP2, where β (a mechanical and geometric parameter of the fracture specimen) and P (the experimentally measured critical load) are constants. Under some circumstances where testing may result in cracking of brittle layers in the test specimen, measurement of the delamination length in addition to the critical load was necessary to determine G. Relative to new module materials, backsheet adhesion was 95% and 98% lower for historic modules that were exposed (operated in the field) andmore » unexposed (stored on-site, but out of direct sunlight), respectively. Encapsulation adhesion was 87-94% lower in the exposed modules and 31% lower in the unexposed module. As a result, the metrology presented here can be used to improve module materials and assess long-term reliability.« less

Authors:
 [1];  [2];  [1];  [1]
  1. Stanford Univ., Stanford, CA (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
OSTI Identifier:
1351446
Alternate Identifier(s):
OSTI ID: 1401879
Report Number(s):
NREL/JA-5J00-66410
Journal ID: ISSN 1062-7995
Grant/Contract Number:  
AC36-08GO28308
Resource Type:
Accepted Manuscript
Journal Name:
Progress in Photovoltaics
Additional Journal Information:
Journal Volume: 25; Journal Issue: 1; Journal ID: ISSN 1062-7995
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; adhesion; reliability; delamination; photovoltaic; encapsulation; backsheet

Citation Formats

Tracy, Jared, Bosco, Nick, Novoa, Fernando, and Dauskardt, Reinhold. Encapsulation and backsheet adhesion metrology for photovoltaic modules. United States: N. p., 2016. Web. doi:10.1002/pip.2817.
Tracy, Jared, Bosco, Nick, Novoa, Fernando, & Dauskardt, Reinhold. Encapsulation and backsheet adhesion metrology for photovoltaic modules. United States. doi:10.1002/pip.2817.
Tracy, Jared, Bosco, Nick, Novoa, Fernando, and Dauskardt, Reinhold. Mon . "Encapsulation and backsheet adhesion metrology for photovoltaic modules". United States. doi:10.1002/pip.2817. https://www.osti.gov/servlets/purl/1351446.
@article{osti_1351446,
title = {Encapsulation and backsheet adhesion metrology for photovoltaic modules},
author = {Tracy, Jared and Bosco, Nick and Novoa, Fernando and Dauskardt, Reinhold},
abstractNote = {Photovoltaic modules are designed to operate for decades in terrestrial environments. However, mechanical stress, moisture, and ultraviolet radiation eventually degrade protective materials in modules, particularly their adhesion properties, eventually leading to reduced solar cell performance. Despite the significance of interfacial adhesion to module durability, currently there is no reliable technique for characterizing module adhesion properties. We present a simple and reproducible metrology for characterizing adhesion in photovoltaic modules that is grounded in fundamental concepts of beam and fracture mechanics. Using width-tapered cantilever beam fracture specimens, interfacial adhesion was evaluated on relevant interfaces of encapsulation and backsheet structures of new and 27-year-old historic modules. The adhesion energy, Gc [J/m2], was calculated from the critical value of the strain energy release rate, G, using G = βP2, where β (a mechanical and geometric parameter of the fracture specimen) and P (the experimentally measured critical load) are constants. Under some circumstances where testing may result in cracking of brittle layers in the test specimen, measurement of the delamination length in addition to the critical load was necessary to determine G. Relative to new module materials, backsheet adhesion was 95% and 98% lower for historic modules that were exposed (operated in the field) and unexposed (stored on-site, but out of direct sunlight), respectively. Encapsulation adhesion was 87-94% lower in the exposed modules and 31% lower in the unexposed module. As a result, the metrology presented here can be used to improve module materials and assess long-term reliability.},
doi = {10.1002/pip.2817},
journal = {Progress in Photovoltaics},
number = 1,
volume = 25,
place = {United States},
year = {2016},
month = {9}
}

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Works referenced in this record:

Moisture transport, adhesion, and corrosion protection of PV module packaging materials
journal, October 2006


Elastic solids with many cracks: A simple method of analysis
journal, January 1987


Interlaminar Fracture Behavior and Fiber Bridging of Glass-Epoxy Composite Under Mode I Static and Cyclic Loadings
journal, April 1989


Elastoplastic analysis of the peel test
journal, January 1988


Testing of packaging materials for improved PV module reliability
conference, January 2005

  • Jorgensen, G. J.; Terwilliger, K. M.; Kempe, M. D.
  • Conference Record of the Thirty-first IEEE Photovoltaic Specialists Conference, 2005.
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Peel adhesion. I. Some phenomenological aspects of the test
journal, March 1963


A Comparison of Fracture Toughness of Matrix Controlled Failure Modes: Delamination and Transverse Cracking
journal, March 1986


Effect of matrix cracking in cross-ply ceramic matrix composite beams on their mechanical properties and natural frequencies
journal, March 2003


On the use of planar shear-lag methods for stress-transfer analysis of multilayered composites
journal, June 2001


A parametric study of the peel test
journal, June 2008


Adhesion and debonding kinetics of photovoltaic encapsulation in moist environments: Adhesion and debonding kinetics of photovoltaic encapsulation
journal, July 2015

  • Novoa, Fernando D.; Miller, David C.; Dauskardt, Reinhold H.
  • Progress in Photovoltaics: Research and Applications, Vol. 24, Issue 2
  • DOI: 10.1002/pip.2657

Mechanics of the Peel Test for Thin Film Adhesion
journal, January 1988


Failure analysis on lattice matched GaInP/Ga(In)As/Ge commercial concentrator solar cells after temperature accelerated life tests: Failure Analysis on III-V commercial concentrator solar cells
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Capping vertically aligned InGaAs/GaAs(Sb) quantum dots with a AlGaAsSb spacer layer in intermediate-band solar cell devices: Capping the InGaAs QDs with a AlGaAsSb spacer layer
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A Triangular Double Cantilever Beam Test for Measuring Adhesive or Cohesive Fracture Energy
journal, June 1992


The interlaminar fracture of organic-matrix, woven reinforcement composites
journal, January 1980


Analytical Solution for Bending of Laminated Composites with Matrix Cracks
journal, January 2016


Environmental mechanisms of debonding in photovoltaic backsheets
journal, January 2014

  • Novoa, Fernando D.; Miller, David C.; Dauskardt, Reinhold H.
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Effective bending stiffness for plates with microcracks
journal, September 2003

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The peeling of flexible laminates
journal, March 1994

  • Kinloch, A. J.; Lau, C. C.; Williams, J. G.
  • International Journal of Fracture, Vol. 66, Issue 1
  • DOI: 10.1007/BF00012635

Theory of stress transfer in a 0°—90°—0° cross-ply laminate containing a parallel array of transverse cracks
journal, January 1992


Fracture and fatigue response of a self-healing epoxy adhesive
journal, March 2011


Compressive-shear adhesion characterization of polyvinyl-butyral and ethylene-vinyl acetate at different curing times before and after exposure to damp-heat conditions: Compressive-shear adhesion characterization of PVB and EVA
journal, September 2012

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Long Term Reliability of Photovoltaic Modules
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Equating damp heat testing with field failures of PV modules
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    Works referencing / citing this record:

    Fracture and fatigue response of a self-healing epoxy adhesive
    journal, March 2011


    Compressive-shear adhesion characterization of polyvinyl-butyral and ethylene-vinyl acetate at different curing times before and after exposure to damp-heat conditions: Compressive-shear adhesion characterization of PVB and EVA
    journal, September 2012

    • Chapuis, Valentin; Pélisset, Ségolène; Raeis-Barnéoud, Marylène
    • Progress in Photovoltaics: Research and Applications, Vol. 22, Issue 4
    • DOI: 10.1002/pip.2270

    A Triangular Double Cantilever Beam Test for Measuring Adhesive or Cohesive Fracture Energy
    journal, June 1992


    Mechanics of the Peel Test for Thin Film Adhesion
    journal, January 1988


    Peel adhesion. I. Some phenomenological aspects of the test
    journal, March 1963


    Effective bending stiffness for plates with microcracks
    journal, September 2003

    • Simkins Jr, D. C.; Li, S.
    • Archive of Applied Mechanics (Ingenieur Archiv), Vol. 73, Issue 3-4
    • DOI: 10.1007/s00419-003-0292-7

    A Comparison of Fracture Toughness of Matrix Controlled Failure Modes: Delamination and Transverse Cracking
    journal, March 1986


    Environmental mechanisms of debonding in photovoltaic backsheets
    journal, January 2014

    • Novoa, Fernando D.; Miller, David C.; Dauskardt, Reinhold H.
    • Solar Energy Materials and Solar Cells, Vol. 120
    • DOI: 10.1016/j.solmat.2013.08.020

    The interlaminar fracture of organic-matrix, woven reinforcement composites
    journal, January 1980


    Long Term Reliability of Photovoltaic Modules
    conference, May 2006

    • Wohlgemuth, John; Cunningham, Daniel; Monus, Paul
    • 2006 IEEE 4th World Conference on Photovoltaic Energy Conference
    • DOI: 10.1109/wcpec.2006.279905

    Moisture transport, adhesion, and corrosion protection of PV module packaging materials
    journal, October 2006


    On the use of planar shear-lag methods for stress-transfer analysis of multilayered composites
    journal, June 2001


    Testing of packaging materials for improved PV module reliability
    conference, January 2005

    • Jorgensen, G. J.; Terwilliger, K. M.; Kempe, M. D.
    • Conference Record of the Thirty-first IEEE Photovoltaic Specialists Conference, 2005.
    • DOI: 10.1109/pvsc.2005.1488179

    Interlaminar Fracture Behavior and Fiber Bridging of Glass-Epoxy Composite Under Mode I Static and Cyclic Loadings
    journal, April 1989


    Adhesion and debonding kinetics of photovoltaic encapsulation in moist environments: Adhesion and debonding kinetics of photovoltaic encapsulation
    journal, July 2015

    • Novoa, Fernando D.; Miller, David C.; Dauskardt, Reinhold H.
    • Progress in Photovoltaics: Research and Applications, Vol. 24, Issue 2
    • DOI: 10.1002/pip.2657

    Analytical Solution for Bending of Laminated Composites with Matrix Cracks
    journal, January 2016


    Theory of stress transfer in a 0°—90°—0° cross-ply laminate containing a parallel array of transverse cracks
    journal, January 1992


    Elastic solids with many cracks: A simple method of analysis
    journal, January 1987


    The peeling of flexible laminates
    journal, March 1994

    • Kinloch, A. J.; Lau, C. C.; Williams, J. G.
    • International Journal of Fracture, Vol. 66, Issue 1
    • DOI: 10.1007/bf00012635

    Effect of matrix cracking in cross-ply ceramic matrix composite beams on their mechanical properties and natural frequencies
    journal, March 2003


    A parametric study of the peel test
    journal, June 2008


    Elastoplastic analysis of the peel test
    journal, January 1988


    Increased reliability of modified polyolefin backsheet over commonly used polyester backsheets for crystalline PV modules
    journal, January 2020

    • Omazic, Antonia; Oreski, Gernot; Edler, Michael
    • Journal of Applied Polymer Science, Vol. 137, Issue 30
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    A novel test method for quantifying cracking propensity of photovoltaic backsheets after ultraviolet exposure
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    • Lin, Chiao-Chi; Lyu, Yadong; Jacobs, Deborah S.
    • Progress in Photovoltaics: Research and Applications, Vol. 27, Issue 1
    • DOI: 10.1002/pip.3038

    Evaluating and predicting molecular mechanisms of adhesive degradation during field and accelerated aging of photovoltaic modules
    journal, July 2018

    • Tracy, Jared; D'hooge, Dagmar R.; Bosco, Nick
    • Progress in Photovoltaics: Research and Applications, Vol. 26, Issue 12
    • DOI: 10.1002/pip.3045

    Fluorescence imaging analysis of depth‐dependent degradation in photovoltaic laminates: insights to the failure
    journal, December 2019

    • Lyu, Yadong; Fairbrother, Andrew; Kim, Jae Hyun
    • Progress in Photovoltaics: Research and Applications, Vol. 28, Issue 2
    • DOI: 10.1002/pip.3212

    Design and understanding of encapsulated perovskite solar cells to withstand temperature cycling
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    • Cheacharoen, Rongrong; Rolston, Nicholas; Harwood, Duncan
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