IEC TR 63279:2020

IEC TR 63279 ®
Edition 1.0 2020-08
TECHNICAL
REPORT
colour
inside
Derisking photovoltaic modules – Sequential and combined accelerated stress
testing
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IEC TR 63279 ®
Edition 1.0 2020-08
TECHNICAL
REPORT
colour
inside
Derisking photovoltaic modules – Sequential and combined accelerated stress

testing
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-8737-8

– 2 – IEC TR 63279:2020 © IEC:2020
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Framework for sequential and combined stress testing . 8
5 Sequential and cyclic sequential test methods . 9
5.1 Extended damp heat and addition of ultraviolet light . 9
5.2 Sequential/combined testing with damp-heat, thermal cycling and ultraviolet
light . 10
5.3 Consideration of interaction of UV radiation and damp heat . 12
5.4 Test-to-failure—A sequential test protocol . 13
5.5 Sequential test protocol optimized for differentiating backsheets . 16
5.6 Mechanical stress testing in combination with damp-heat, humidity-freeze,
and thermal-cycling tests for examining cell cracking and its effects . 20
6 Mechanism-specific multi-factor stress tests . 22
6.1 General . 22
6.2 Testing for delamination . 22
6.2.1 General . 22
6.2.2 Delamination – UV irradiation with high-temperature stress . 22
6.2.3 Delamination – UV irradiation with thermal-cycling stress and humidity
freeze . 23
6.2.4 Delamination – UV irradiation with cyclic dynamic mechanical loading,
thermal cycling stress, and humidity freeze . 24
6.2.5 Delamination – Temperature, humidity, and electric field associated with
system voltage . 25
6.3 Testing for potential-induced degradation . 28
6.3.1 General . 28
6.3.2 Testing for potential-induced degradation with humidity, voltage, bias,
and light . 28
6.3.3 Factor of salt mist . 29
6.4 Testing in damp heat with current injection and as a function of temperature . 30
6.5 Cell cracking and propagation in cyclic loading at various temperatures. 31
7 Combined-accelerated stress testing . 33
7.1 Combined-accelerated stress testing for tropical environments . 33
7.2 Combined-accelerated stress testing for multiple environments . 36
8 Future directions. 39
Annex A (informative) Overview of degradation modes and causal stress factors . 41
Annex B (informative) Failure modes plotted on a failure tree diagram for selected
clauses in this document . 43
Annex C (informative) Summary table of sequential and combined testing: Samples,
factors, combination, and stress-test results . 44
Bibliography . 49

Figure 1 – Framework for sequential and combined stress testing, showing three axes
of comprehensiveness – testing samples, the number of stress factors of the natural
environment, and their sequence or combination of application. . 9
Figure 2 – Fraction power loss of modules though stress testing . 10

Figure 3 – (a) Combined test sequence, and resulting (b) normalized power loss,
(c) short-circuit current (I ), and (d) fill factor (FF) [1] . 11
SC
Figure 4 – Power degradation of modules in 85 °C and 85 % relative humidity as a

function of extent of preconditioning under Xe light [9] . 13
Figure 5 – (a) Overview of the test-to-failure sequences, and (b) results showing
module power normalized to their post-light-soak values for seven module types. 14
Figure 6 – Examples of field-relevant degradation modes seen in modules tested in
the test-to-failure protocol . 15
Figure 7 – Module accelerated sequential tests (MAST) . 17
Figure 8 – Degradation modes from MAST and fielded modules . 19
Figure 9 – (a) Front-side mini-module exposure in a xenon weathering chamber with
water spray; (b) fielded module with six years of service in North America with 30 %
power loss [21] . 20
Figure 10 – (a) Test-stage description; (b) relative change in standard test condition
(STC) module parameters as a function of stage and maximum  power determined at

STC [23] . 21
Figure 11 – (a) Stress testing at 65 °C combined with UV radiation dose of 180 W/m
in the range of 300–400 nm, 900 h; (b) 75 °C without UV radiation, 1 000 h [28] . 23
Figure 12 – Delamination in sequential test . 25
Figure 13 – Delamination associated with system voltage . 27
Figure 14 – Degradation of three modules with and without UV-A light irradiance in
chamber at 60 °C, 85 % RH, and 1 000 V (positive or negative polarity depending on
the sample) . 29
Figure 15 – Sheet resistance measured on glass surfaces with various soil types, as a
function of relative humidity (RH %), at 60 °C [41] . 30
Figure 16 – Cyclic unidirectional 4-point bending with loading alternating between 0 N
and 500 N at different temperatures as shown, with duration of 4 s at each of the high-
and low-pressure dwells, 10 000 to 30 000 cycles with pressure (“Press”) from the
front-glass side or backsheet side [49] . 32
Figure 17 – Example of 24 h PV module combined accelerated stress-testing protocol
modified from ASTM D7869 . 34
Figure 18 – Shrinkage of polymer C backsheet leading to delamination and cracking . 35
Figure 19 – Multiple-environment C-AST sequence . 37
Figure 20 – Failure of two mini-modules with a polymer B outer-layer backsheet type
undergoing different multiple-environment C-AST sequences . 38

Table 1 – Extended damp heat and ultraviolet light . 10
Table 2 – Sequential/combined testing with damp-heat thermal cycling and ultraviolet
radiation . 12
Table 3 – Ultraviolet light and damp-heat interaction . 13
Table 4 – Test-to-failure – Sequential test protocol . 16
Table 5 – Module accelerated stress test 1 (MAST #1) . 18
Table 6 – Module accelerated stress test 2 (MAST #2) . 18
Table 7 – Module accelerated stress test 3 (MAST #3) . 18
Table 8 – SML-TC-HF sequential test . 21
Table 9 – UV irradiation under high-temperature conditions . 23
Table 10 – UV irradiation with TC stress . 24
Table 11 – UV irradiation with DML-TC-HF sequential test . 25

– 4 – IEC TR 63279:2020 © IEC:2020
Table 12 – DH – Negative system bias stress sequential test . 28
Table 13 – UV irradiation – negative system bias stress combined test . 29
Table 14 – Bending load test at various temperatures . 33
Table 15 – Partial list of observed degradation modes, attributed mechanisms, and
stress factors seen in the first application of the combined accelerated stress-testing

protocol based on ASTM D7869 . 35
Table 16 – Combined-accelerated stress test (Tropical 24 h ASTM D7869-based
sequence) . 36
Table 17 – Multiple-environment combined-accelerated stress test . 38
Table A.1 – Degradation modes and potential stress factors that can lead to their
manifestation . 42
Table C.1 – Table summarizing sequential and combined stress testing . 44

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