IEC TS 63342:2022

C-Si photovoltaic (PV) modules - Light and elevated temperature induced degradation (LETID) test - Detection

IEC TS 63342:2022 is designed to assess the effect of light induced degradation at elevated temperatures (LETID) by application of electrical current at higher temperatures. 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. The proposed test procedure can reveal sample sensitivity to LETID degradation mechanisms, but it does not provide an exact measure of field observable degradation.

General Information

• Status: Published
• Publication Date: 19-Jul-2022
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Drafting Committee: WG 2 - TC 82/WG 2
• Current Stage: PPUB - Publication issued
• Start Date: 20-Jul-2022
• Completion Date: 17-Aug-2022

Overview

IEC TS 63342:2022 - "C‑Si photovoltaic (PV) modules - Light and elevated temperature induced degradation (LETID) test - Detection" specifies a reproducible laboratory procedure to detect sensitivity of crystalline‑silicon (C‑Si) PV modules to LETID using a current injection approach. The Technical Specification defines sample preparation, apparatus, measurement accuracy and a test sequence that reveals LETID‑related performance loss at elevated temperatures (>50 °C). It emphasizes detection (sensitivity) rather than providing an exact prediction of field degradation.

Key topics and requirements

• Test focus: Detection of LETID activated by excess carriers at elevated temperature via electrical current injection (not light‑only stress).
• Scope limits: B‑O (Boron‑Oxygen) and Fe‑B (Iron‑Boron) degradation phenomena are excluded from the test objective; procedures attempt to separate their effects but separation may be imperfect. The method does not quantify field‑observable degradation magnitude or timing.
• Samples: Three modules - one control and two test samples - stored in the dark (≤35 °C) and produced under normal manufacturing controls.
• Apparatus essentials:
  • Climatic chamber capable up to (75 ± 3) °C with air circulation and condensation control.
  • Temperature sensors and instruments (accuracy ±2.0 °C, repeatability ±0.5 °C).
  • Current source able to apply the specified continuous injection current (accuracy 1 % or better).
  • Voltage/current monitoring with resolution ≥5 min and accuracy ±0.2 %.
• Measurements and sequence: visual inspection, electroluminescence (EL) imaging (forward bias at ISC and optionally 0.1·ISC), initial performance at STC, B‑O preconditioning via current injection (CID), LETID stress sequence, dark voltage monitoring, and defined stop criteria based on temperature‑corrected dark voltage evolution.
• Data handling: temperature correction, filtering, averaging and explicit stop criteria for the LETID sequence are specified to ensure reproducibility.

Applications and users

• Who benefits: PV module manufacturers, test laboratories, R&D teams, quality assurance engineers and reliability specialists concerned with PV module degradation mechanisms.
• Practical uses:
  • Screening module designs and production lots for LETID sensitivity.
  • Comparative lab evaluation of cell/module processes and materials.
  • Supporting root‑cause analysis using EL and dark‑voltage diagnostics.
• Limitations: Use for detection and comparison; not a direct replacement for long‑term field monitoring or full quantification of site‑specific degradation.

Related standards

• IEC 61215‑1 / IEC 61215‑2 (PV module qualification tests)
• IEC TS 60904‑13 (Electroluminescence of PV modules)
• IEC TS 63202‑4 (cell LETID test methods - differing injection levels)

Keywords: IEC TS 63342:2022, LETID detection, C‑Si PV modules, current injection, EL imaging, dark voltage, B‑O, Fe‑B, climatic chamber, STC performance.

Standards Content (Sample)

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
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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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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

– 6 – IEC TS 63342:2022  IEC 2022
ISO/IEC Guide 98-3:2008, Uncertainty of measurement – Part 3: Guide to the expression of
uncertainty in measurement (GUM:1995)
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TS 61836,
IEC 61215-1, IEC 61215-2 apply, as well as the following.
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
3.2 Abbreviated terms
LETID Light and Elevated Temperature Induced Degradation
4 Samples
Three samples are required, one is used as a control and the other two are for testing. The
purpose of the control module is to track a possible
...