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Title: Use of Indentation to Study the Degradation of Photovoltaic Backsheets

Abstract

The ability of electrical insulating materials within a module to act as insulators is a key safety requirement for photovoltaic (PV) technology. Presently, however, the durability of backsheets may not be readily assessed. For example, the mechanical tensile test continues to be developed, and its use has not been validated such that a technically based pass/fail criteria may be established. This study examines the use of simple indentation methods, including durometer hardness and instrumented indentation, as a means to quantitively assess the degradation of PV backsheets. Characteristics including: hardness, modulus, load/displacement profile, creep hold response, and residual impression are explored in an empirical study. Glass/encapsulant/backsheet mini-modules constructed using backsheets including: polyamide (PA), poly(ethylene terephthalate) (PET), polyvinyl fluoride (PVF) laminate ('TPE'), and polyvinylidene fluoride (PVDF) were examined. An M-type durometer as well as Berkovich and cube-corner tips were used in the indentation experiments. Additional characterizations were performed to interpret the indentation measurements including: surface roughness measurements using atomic force microscopy (AFM), a chemical integrity study using Fourier-transform infrared spectroscopy (FTIR), and phase-transition measurements using differential scanning calorimetry (DSC). The results are analyzed in the context of the combined accelerated stress test (C-AST) also explored in this study. Instrumented indentation (i.e., usingmore » a Berkovich tip) was able to distinguish between backsheets and quantify the effects of accelerated testing (including up to 60%, 25%, and 20% change in hardness, modulus, and creep displacement, respectively). The embrittlement of the backsheets was not readily assessable using cube-corner indentation. Cracking of the known-bad polyamide backsheet was observed from the C-AST, which was not observed to result from steady state UV weathering.« less

Authors:
 [1];  [1];  [1]
  1. National Renewable Energy Laboratory (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), Solar Energy Technologies Office (EE-4S), Durable Modules Consortium (DuraMAT)
OSTI Identifier:
1548262
Report Number(s):
NREL/JA-5K00-73040
DOE Contract Number:  
AC36-08GO28308
Resource Type:
Journal Article
Journal Name:
Solar Energy Materials and Solar Cells
Additional Journal Information:
Journal Volume: 201
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; backsheet; durability; instrumented indentation; nanoindentation; reliability

Citation Formats

Miller, David C, Owen-Bellini, Michael, and Hacke, Peter L. Use of Indentation to Study the Degradation of Photovoltaic Backsheets. United States: N. p., 2019. Web. doi:10.1016/j.solmat.2019.110082.
Miller, David C, Owen-Bellini, Michael, & Hacke, Peter L. Use of Indentation to Study the Degradation of Photovoltaic Backsheets. United States. doi:10.1016/j.solmat.2019.110082.
Miller, David C, Owen-Bellini, Michael, and Hacke, Peter L. Thu . "Use of Indentation to Study the Degradation of Photovoltaic Backsheets". United States. doi:10.1016/j.solmat.2019.110082.
@article{osti_1548262,
title = {Use of Indentation to Study the Degradation of Photovoltaic Backsheets},
author = {Miller, David C and Owen-Bellini, Michael and Hacke, Peter L},
abstractNote = {The ability of electrical insulating materials within a module to act as insulators is a key safety requirement for photovoltaic (PV) technology. Presently, however, the durability of backsheets may not be readily assessed. For example, the mechanical tensile test continues to be developed, and its use has not been validated such that a technically based pass/fail criteria may be established. This study examines the use of simple indentation methods, including durometer hardness and instrumented indentation, as a means to quantitively assess the degradation of PV backsheets. Characteristics including: hardness, modulus, load/displacement profile, creep hold response, and residual impression are explored in an empirical study. Glass/encapsulant/backsheet mini-modules constructed using backsheets including: polyamide (PA), poly(ethylene terephthalate) (PET), polyvinyl fluoride (PVF) laminate ('TPE'), and polyvinylidene fluoride (PVDF) were examined. An M-type durometer as well as Berkovich and cube-corner tips were used in the indentation experiments. Additional characterizations were performed to interpret the indentation measurements including: surface roughness measurements using atomic force microscopy (AFM), a chemical integrity study using Fourier-transform infrared spectroscopy (FTIR), and phase-transition measurements using differential scanning calorimetry (DSC). The results are analyzed in the context of the combined accelerated stress test (C-AST) also explored in this study. Instrumented indentation (i.e., using a Berkovich tip) was able to distinguish between backsheets and quantify the effects of accelerated testing (including up to 60%, 25%, and 20% change in hardness, modulus, and creep displacement, respectively). The embrittlement of the backsheets was not readily assessable using cube-corner indentation. Cracking of the known-bad polyamide backsheet was observed from the C-AST, which was not observed to result from steady state UV weathering.},
doi = {10.1016/j.solmat.2019.110082},
journal = {Solar Energy Materials and Solar Cells},
number = ,
volume = 201,
place = {United States},
year = {2019},
month = {8}
}