IEC TS 63209-2:2022

IEC TS 63209-2 ®
Edition 1.0 2022-08
TECHNICAL
SPECIFICATION
colour
inside
Photovoltaic modules – Extended-stress testing –
Part 2: Polymeric component materials
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IEC TS 63209-2 ®
Edition 1.0 2022-08
TECHNICAL
SPECIFICATION
colour
inside
Photovoltaic modules – Extended-stress testing –

Part 2: Polymeric component materials

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-5293-2

– 2 – IEC TS 63209-2:2022 © IEC 2022
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Failure modes and component interactions . 8
5 Selection of tests . 9
6 Single component testing . 9
6.1 Extended test procedures . 9
6.2 Reporting of single component durability properties . 10
6.2.1 Product identification . 10
6.2.2 Reliability test data . 10
7 BOM specific testing . 11
7.1 Test procedures – test coupons . 11
7.2 Test procedure – mini-modules . 13
7.2.1 Mini-module design. 13
7.2.2 Mini-module testing . 14
7.3 Reporting of BOM specific tests . 15
7.3.1 Product identification . 15
7.3.2 Reliability test data . 15
8 Uniform Characterization Form . 16
8.1 General . 16
8.2 Material test results and reporting requirements . 17
Bibliography . 20

Figure 1 – Mini-module design parameters, 1-cell and 4-cell . 14

Table 1 – Encapsulant and backsheet failure modes . 9
Table 2 – Single component testing . 10
Table 3 – BOM specific tests for Glass/Backsheet cSi modules . 12
Table 4 – BOM specific tests for Glass/Glass cSi modules . 13
Table 5 – Mini-module design parameters . 15
Table 6 – Uniform Characterization Form – Part 1 . 18
Table 7 – Uniform Characterization Form – Part 2 . 19

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC MODULES – EXTENDED-STRESS TESTING –

Part 2: Polymeric component materials

FOREWORD
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IEC TS 63209-2 been prepared by IEC technical committee 82: Solar photovoltaic energy
systems. It is a Technical Specification.
The text of this Technical Specification: is based on the following documents:
Draft Report on voting
82/2015/DTS 82/2058A/RVDTS
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this Technical Specification is English.
A list of all parts in the IEC 63209 series, published under the general title Photovoltaic modules
– Extended-stress testing, can be found on the IEC website.

– 4 – IEC TS 63209-2:2022 © IEC 2022
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INTRODUCTION
This document is intended as a guide for component suppliers, module manufacturers and
downstream durability assessments, and focuses on polymeric materials in crystalline silicon
module laminates.
IEC TS 63209 series describes environmental stress tests which provide data for evaluation of
the long-term reliability of PV modules, probing areas not addressed in the IEC 61215 and
IEC 61730 series. IEC TS 63209-1 provides a menu of extended environmental stress tests for
PV modules, and this document, IEC TS 63209-2, describes complementary component level
testing which probes degradation modes which are not easily understood or addressed by
module level testing. This document additionally describes an overlapping suite of component
level tests useful for screening individual components and component combinations for a
specific bill of materials (BOM).
The testing in this document is intended for reliability evaluation only, with no pass/fail
requirements.
This document does not describe any new test or stress exposures, but takes the single
component testing described in the IEC 62788 series as a base line for stress exposures which
are then extended. As degradation of one component can be influenced by other components
(e.g. some backsheets tested with one encapsulant may perform differently than with another,
and vice versa), a slate of BOM-specific tests and related stress exposures are included which
are described in IEC 62788 component standards, but are not typically part of component data
sheets.
This document details component level stress sequences, sample construction and evaluation
test methods which can assist in a durability analysis. A particular focus is given to UV stress
alone and in combination with other stressors. UV exposures, in particular, are difficult to
perform accurately at the module level due to time and space constraints. Polymeric
components are known to have UV-induced degradation modes which progress relatively
slowly. Testing at a component level allows for smaller sample sizes, longer stress exposures,
and test coupons designed to target relevant properties after applied stress.

– 6 – IEC TS 63209-2:2022 © IEC 2022
PHOTOVOLTAIC MODULES – EXTENDED-STRESS TESTING –

Part 2: Polymeric component materials

1 Scope
This part of IEC TS 63209 includes a menu of tests to use for evaluation of the long-term
reliability of materials used as backsheets and encapsulants in PV modules. It is intended to
provide information to supplement the baseline testing defined in IEC 61215 and IEC 61730,
which are qualification tests with pass-fail criteria. It may be used by PV stakeholders in
conjunction with IEC TS 63209-1, to provide more extended stress testing of the component
materials than can practically be accomplished with PV modules. The data set resulting from
testing is used for reliability analysis and is not intended to be used as a pass-fail test
procedure. This document addresses polymeric materials in the crystalline silicon module
laminates, specifically backsheets and encapsulants in Glass/Glass or Glass/Backsheet
modules. Although not specifically addressed, it is expected to also have applicability to thin
film technologies.
The included environmental stress tests are intended to cause degradation that is most relevant
to field experience, but these may not capture all failure modes which may be observed in
various locations.
The individual component standards provide a starting point for testing, and baseline data for
reference in this document may be available from a characterization sheet developed in
accordance with the Uniform Characterization Forms (UCF) of IEC TS 62788-2 and
IEC 62788-1-1. Extended tests using the same methods allows for trend analysis.
Additional testing is included to address interactions with other polymeric packaging material,
as individual components can perform differently depending on adjacent materials. These tests
are designed with BOM-specific coupons and mini-modules, intended to complement the
specific module bill of materials used in the IEC TS 63209-1 module tests.
As both test specimen form factor and I-V characteristics can play a role in degradation, some
multicomponent tests are designed to use a polymeric stack, while others use mini-modules.
The included stress tests are not designed to test to failure, but to be representative of stress
levels of the long-term application.
These tests are not intended to provide service life estimates, or to be indicative of fitness for
use in specific climate/mounting configurations. For example, the same module deployed in two
different locations or with different mounting methods may degrade in different ways, so a single
test protocol cannot be expected to exactly match the performance in both environments;
correlation to field will depend upon where and how the product is deployed.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC TS 60904-13:2018, Photovoltaic devices – Part 13: Electroluminescence of photovoltaic
modules
IEC 61215-1-1:2021, Terrestrial photovoltaic (PV) modules – Design qualification and type
approval -Part 1-1: Special requirements for testing of crystalline silicon photovoltaic (PV)
modules
IEC 61215-2:2021, Terrestrial photovoltaic (PV) modules – Design qualification and type
approval – Part 2: Test procedures
IEC 61730-2, Photovoltaic (PV) module safety qualification – Part 2: Requirements for testing
IEC TS 61836, Solar photovoltaic energy systems – Terms, definitions and symbols
IEC 62788-1-1, Measurement procedures for materials used in photovoltaic modules – Part 1-1:
Encapsulants – Polymeric materials used for encapsulants
IEC 62788-1-6, Measurement procedures for materials used in photovoltaic modules – Part 1-6:
Encapsulants – Test methods for determining the degree of cure in ethylene-vinyl acetate
IEC 62788-1-7:2020, Measurement procedures for materials used in photovoltaic modules –
Part 1-7: Encapsulants – Test procedure of optical durability
IEC TS 62788-2, Measurement procedures for materials used in photovoltaic modules – Part 2:
Polymeric materials – Frontsheets and backsheets
IEC TS 62788-6-3, Measurement procedures for materials used in photovoltaic modules – Part
6-3: Adhesion testing of interfaces within PV modules
IEC TS 62788-7-2:2017, Measurement procedures for materials used in photovoltaic modules
– Part 7-2: Environmental exposures – Accelerated weathering tests of polymeric materials
IEC TS 62804-1, Photovoltaic (PV) modules – Test methods for the detection of potential-
induced degradation – Part 1: Crystalline silicon
IEC TS 63209-1:2021, Photovoltaic modules – Extended-stress testing – Part 1: Modules
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TS 62788-2,
IEC 62788-1-1, IEC 62788-1-7, IEC TS 63209-1, IEC TS 61836 along with the following apply:
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
Bill of Materials
BOM
list of the specific materials used to build a specific PV module, excluding equal alternates
3.2
Uniform Characterization Form
UCF
list of properties to be evaluated according to the tests in this document

– 8 – IEC TS 63209-2:2022 © IEC 2022
3.3
Single Cantilever Beam
SCB
adhesion test using a single cantilever beam as described in IEC TS 62788-6-3
4 Failure modes and component interactions
Degradation of polymeric materials can occur both by chemical changes to a specific material,
such as thermo-oxidative degradation, hydrolysis, photolysis, and by morphological changes,
such as reordering of type or degree of crystallinity, which can significantly alter key properties.
Subsequent mechanical, thermo-mechanical, or hydromechanical stresses such as obtained
with thermal cycling, coefficient of thermal expansion (CTE) differentials, or from volume
changes associated with moisture ingress/egress, can then induce physical degradation, such
as delamination and cracking. Observed failure modes for backsheets and encapsulants are
shown in Table 1.
Degradation of single components is evaluated by monitoring changes to key characteristics
after single stresses (exposure to damp heat (DH), thermal, and ultraviolet (UV) as specified in
the IEC 62788 series, using the Xe exposures defined in IEC TS 62788-7-2. In this document,
the UV stress is extended and includes multiple data points to observe changes and allow for
extrapolation to longer UV exposures. Specifics are detailed in the individual single component
sections.
Observed failure modes of backsheets and encapsulants include: frontside (through glass)
cracking, backside cracking, interlayer delamination, and discoloration as well as delamination
and increased optical absorption of the encapsulant.
Failure modes can be influenced by other module components (see Bibliography for references
providing pictures and more details). These interactions can result in both positive and negative
effects as shown in Table 1. BOM specific testing is used to evaluate these effects, and
adhesion.
Table 1 – Encapsulant and backsheet failure modes
Component Degradation mode Interactions with other components
cell side yellowing
encapsulant
cell side cracking
plus: UV filter
minus: chemical interactions with base polymer,
backsheet / encapsulant delamination
additives or impurities
loss of transmission (clear)
interlayer delamination n/a
air side yellowing n/a
encapsulant, connectors, cells
Backsheet
• connectors provide localized stress points which

can induce cracks
• thickness and compliance of encapsulant can
mitigate the stress from cell edges/connectors
encapsulant, con
...