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
Current Stage
PPUB - Publication issued
Completion Date
20-Jul-2022
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IEC TS 63342:2022 - 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
IEC TS 63342:2022-07(en)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
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

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 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

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IEC TS 63342:2022  IEC 2022 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
C-SI PHOTOVOLTAIC (PV) MODULES – LIGHT AND ELEVATED
TEMPERATURE INDUCED DEGRADATION (LETID) TEST – DETECTION
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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rights. IEC shall not be held responsible for identifying any or all such patent rights.

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.
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– 4 – IEC TS 63342:2022  IEC 2022

The committee has decided that the contents of this document will remain unchanged until the

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specific document. At this date, the document will be
• reconfirmed,
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IMPORTANT – The "colour inside" logo on the cover page of this document indicates that it

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---------------------- Page: 6 ----------------------
IEC TS 63342:2022  IEC 2022 – 5 –
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
---------------------- Page: 7 ----------------------
– 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
...

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