IEC TS 63342:2022

IEC TS 63342 ®
Edition 1.0 2022-07
TECHNICAL
SPECIFICATION
colour
inside
C-Si photovoltaic (PV) modules – Light and elevated temperature induced
degradation (LETID) test – Detection
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IEC TS 63342 ®
Edition 1.0 2022-07
TECHNICAL
SPECIFICATION
colour
inside
C-Si photovoltaic (PV) modules – Light and elevated temperature induced
degradation (LETID) test – Detection
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-3977-3
– 2 – IEC TS 63342:2022  IEC 2022
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and abbreviated terms . 6
3.1 Terms and definitions . 6
3.2 Abbreviated terms . 6
4 Samples . 6
5 Apparatus . 6
6 Testing . 6
6.1 General . 6
6.2 Visual inspection . 7
6.3 Electroluminescence images . 7
6.4 Performance at STC . 7
6.5 B-O LID preconditioning via current injection (CID) . 8
6.6 Light and elevated temperature induced degradation (LETID) . 8
7 Dark voltage analysis . 9
7.1 General . 9
7.2 Data filtering . 9
7.3 Temperature correction . 9
7.4 Data averaging . 10
7.5 Stop criterion . 10
8 Evaluation . 11
9 Report . 11
Bibliography . 13

Figure 1 – Test sequence for the detection of LETID in c-Si modules . 7
Figure 2 – Dark voltage diagram showing the evolution of the temperature corrected
dark voltage over time in arbitrary units during LETID degradation used to identify the
time of maximum degradation and the time to stop the LETID degradation sequence . 11

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
C-SI PHOTOVOLTAIC (PV) MODULES – LIGHT AND ELEVATED
TEMPERATURE INDUCED DEGRADATION (LETID) TEST – DETECTION

FOREWORD
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IEC TS 63342 has 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
82/2008/DTS 82/2044/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.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.

– 4 – IEC TS 63342:2022  IEC 2022
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• reconfirmed,
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• replaced by a revised edition, or
• amended.
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C-SI PHOTOVOLTAIC (PV) MODULES – LIGHT AND ELEVATED
TEMPERATURE INDUCED DEGRADATION (LETID) TEST – DETECTION

1 Scope
This document is designed to assess the effect of light induced degradation at elevated
temperatures (LETID) by application of electrical current at higher temperatures. LETID is
activated by excess carriers caused either through illumination or injection of electrical current
at temperatures above 50 °C. In fielded conditions, LETID develops over the course of several
months up to years as opposed to days for Boron Oxygen (B-O) degradation. The degradation
phase is followed by an even slower recovery phase that develops over a significantly longer
time scale. In this document, only the current injection approach for the detection of LETID is
addressed.
This document does not address the B-O and Iron Boron (Fe-B) related degradation phenomena,
which already occur at room temperatures under the presence of light and on much faster time
scales. B-O defects may influence the results, and this document attempts to separate them by
application of certain procedures. However, it is noted that the separation may not be perfect.
Fe-B effects are excluded by introduction of waiting times before power determination.
The proposed test procedure can reveal sample sensitivity to LETID degradation mechanisms,
but it does not provide an exact measure of field observable degradation. The magnitude and
time scale of degradation seen in the field depends on climate and the module technology.
In this document LETID testing is done via current injection as this is a simple method in terms
of the test equipment required. This allows for better control over conditions compared to
application of light and thus ensures comparability between different labs. Application of light
with equivalent conditions (i.e. same temperature and excess carrier density/ injection level)
will yield comparable results.
The stress conditions in this document differ in injection level from the test method for cells
described in IEC TS 63202-4. Whereas IEC TS 63202-4 aims at providing a quick quality check
for a known cell that can be used in outgoing or incoming inspection of a specific product, the
procedures in this document aim at providing a general product independent test method for
LETID detection in a module that can be applied without prior knowledge about the cells inside
a module and will yield reproducible results.
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, Photovoltaic devices – Part 13: Electroluminescence of photovoltaic modules
IEC 61215-1:2021, Terrestrial photovoltaic (PV) modules – Design qualification and type
approval – Part 1: Test requirements
IEC 61215-2:2021, Terrestrial photovoltaic (PV) modules – Design qualification and type
approval – Part 2: Test procedures
IEC TS 61836, Solar photovoltaic energy systems – Terms, definitions and symbols
...