IEC 62788-1-4:2016

Measurement procedures for materials used in photovoltaic modules - Part 1-4: Encapsulants - Measurement of optical transmittance and calculation of the solar-weighted photon transmittance, yellowness index, and UV cut-off wavelength

IEC 62788-1-4:2016 provides a method for measurement of the optical transmittance of encapsulation materials used in photovoltaic (PV) modules. The standardized measurements in this procedure quantify the expected transmittance of the encapsulation to the PV cell. Subsequent calculation of solar-weighted transmittance allows for comparison between different materials. The results for unweathered material may be used in an encapsulation manufacturer's datasheets, in manufacturer's material or process development, in manufacturing quality control (material acceptance), or applied in the analysis of module performance. This measurement method can also be used to monitor the performance of encapsulation materials after weathering, to help assess their durability.

Procédures de mesure des matériaux utilisés dans les modules photovoltaïques - Partie 1-4: Encapsulants - Mesurage du facteur de transmission optique et calcul du facteur de transmission photonique à pondération solaire, de l'indice de jaunissement et de la fréquence de coupure des UV

L'IEC 62788-1-4:2016 fournit une méthode de mesure du facteur de transmission optique des matériaux d'encapsulation utilisés dans les modules photovoltaïques (PV). Les mesurages normalisés de cette procédure permettent de quantifier le facteur de transmission prévu de l'encapsulation vers la cellule PV. Le calcul ultérieur du facteur de transmission à pondération solaire permet de comparer les différents matériaux. Les résultats concernant les matériaux non exposés aux intempéries peuvent être utilisés dans les fiches techniques d'un fabricant d'encapsulation, dans le développement des matériaux ou du procédé du fabricant, dans le contrôle de la qualité de fabrication (acceptation du matériau) ou être appliqués dans l'analyse des performances du module. Cette méthode de mesure peut également être utilisée pour contrôler les performances des matériaux d'encapsulation après exposition aux intempéries, afin d'évaluer leur durabilité.

General Information

• Status: Published
• Publication Date: 14-Oct-2020
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• 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: 15-Nov-2016
• Completion Date: 27-Sep-2016

Relations

• Amended By: IEC 62788-1-4:2016/AMD1:2020 - Amendment 1 - Measurement procedures for materials used in photovoltaic modules - Part 1-4: Encapsulants - Measurement of optical transmittance and calculation of the solar-weighted photon transmittance, yellowness index, and UV cut-off wavelength
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 62788-1-4 ®
Edition 1.0 2016-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Measurement procedures for materials used in photovoltaic modules –
Part 1-4: Encapsulants – Measurement of optical transmittance and calculation
of the solar-weighted photon transmittance, yellowness index, and UV cut-off
wavelength
Procédures de mesure des matériaux utilisés dans les modules
photovoltaïques –
Partie 1-4: Encapsulants – Mesurage du facteur de transmission optique
et calcul du facteur de transmission photonique à pondération solaire,
de l'indice de jaunissement et de la fréquence de coupure des UV

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IEC 62788-1-4 ®
Edition 1.0 2016-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Measurement procedures for materials used in photovoltaic modules –

Part 1-4: Encapsulants – Measurement of optical transmittance and calculation

of the solar-weighted photon transmittance, yellowness index, and UV cut-off

wavelength
Procédures de mesure des matériaux utilisés dans les modules

photovoltaïques –
Partie 1-4: Encapsulants – Mesurage du facteur de transmission optique

et calcul du facteur de transmission photonique à pondération solaire,

de l'indice de jaunissement et de la fréquence de coupure des UV

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.160 ISBN 978-2-8322-3634-5

– 2 – IEC 62788-1-4:2016  IEC 2016
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references. 5
3 Terms and definitions . 6
4 Principle . 7
5 Apparatus . 7
6 Test specimens . 7
6.1 Nominal (and unweathered) transmittance to the cell . 7
6.2 Weathering studies . 8
6.3 Glass for superstrates/substrates . 9
6.4 Number of specimens . 9
6.5 Preconditioning of specimens . 9
7 Measurement procedure . 9
7.1 General . 9
7.2 Specimen preparation . 9
7.3 Instrument calibration (baseline measurements) . 9
7.4 Specimen measurements . 10
7.5 Witness measurements . 10
8 Calculation and expression of results . 10
8.1 Post-processing of data . 10
8.2 Calculation of weighted transmittance . 10
8.3 Calculation of the Yellowness Index (YI) . 11
8.4 Calculation of the UV cut-off wavelength . 11
9 Uncertainty of measurements . 11
10 Test report. 12
Annex A (informative) Advanced analysis of transmittance (absorption coefficients) . 14
Annex B (informative) Applying the quantum efficiency of a specific cell technology . 16
Bibliography . 18

Table 1 – Details of the solar weight transmittance parameters . 11

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASUREMENT PROCEDURES FOR MATERIALS
USED IN PHOTOVOLTAIC MODULES –

Part 1-4: Encapsulants – Measurement of optical transmittance and
calculation of the solar-weighted photon transmittance,
yellowness index, and UV cut-off wavelength

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62788-1-4 has been prepared by IEC technical committee 82:
Solar photovoltaic energy systems.
The text of this standard is based on the following documents:
FDIS Report on voting
82/1148/FDIS 82/1165/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
...

IEC 62788-1-4 ®
Edition 1.1 2020-10
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Measurement procedures for materials used in photovoltaic modules –
Part 1-4: Encapsulants – Measurement of optical transmittance and calculation
of the solar-weighted photon transmittance, yellowness index, and UV cut-off
wavelength
Procédures de mesure des matériaux utilisés dans les modules
photovoltaïques –
Partie 1-4: Encapsulants – Mesurage du facteur de transmission optique
et calcul du facteur de transmission photonique à pondération solaire,
de l'indice de jaunissement et de la fréquence de coupure des UV
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and
once a month by email. French extracted from the Terms and definitions clause of
IEC publications issued between 2002 and 2015. Some
IEC Customer Service Centre - webstore.iec.ch/csc entries have been collected from earlier publications of IEC
If you wish to give us your feedback on this publication or TC 37, 77, 86 and CISPR.

need further assistance, please contact the Customer Service

Centre: [e-mail].
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

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La recherche avancée permet de trouver des publications IEC monde, avec plus de 22 000 articles terminologiques en
en utilisant différents critères (numéro de référence, texte, anglais et en français, ainsi que les termes équivalents dans
comité d’études,…). Elle donne aussi des informations sur les 16 langues additionnelles. Egalement appelé Vocabulaire
projets et les publications remplacées ou retirées. Electrotechnique International (IEV) en ligne.

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Service Clients - webstore.iec.ch/csc 86 et CISPR de l'IEC.

Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
[e-mail].
IEC 62788-1-4 ®
Edition 1.1 2020-10
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Measurement procedures for materials used in photovoltaic modules –

Part 1-4: Encapsulants – Measurement of optical transmittance and calculation

of the solar-weighted photon transmittance, yellowness index, and UV cut-off

wavelength
Procédures de mesure des matériaux utilisés dans les modules

photovoltaïques –
Partie 1-4: Encapsulants – Mesurage du facteur de transmission optique

et calcul du facteur de transmission photonique à pondération solaire,

de l'indice de jaunissement et de la fréquence de coupure des UV

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.160 ISBN 978-2-8322-8968-6

IEC 62788-1-4 ®
Edition 1.1 2020-10
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
Measurement procedures for materials used in photovoltaic modules –
Part 1-4: Encapsulants – Measurement of optical transmittance and calculation
of the solar-weighted photon transmittance, yellowness index, and UV cut-off
wavelength
Procédures de mesure des matériaux utilisés dans les modules
photovoltaïques –
Partie 1-4: Encapsulants – Mesurage du facteur de transmission optique
et calcul du facteur de transmission photonique à pondération solaire,
de l'indice de jaunissement et de la fréquence de coupure des UV
– 2 – IEC 62788-1-4:2016+AMD1:2020 CSV
 IEC 2020
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Principle . 7
5 Apparatus . 7
6 Test specimens . 7
6.1 Nominal (and unweathered) transmittance to the cell . 7
6.2 Weathering studies . 8
6.3 Glass for superstrates/substrates . 9
6.4 Number of specimens . 9
6.5 Preconditioning Conditioning of specimens . 9
7 Measurement procedure . 9
7.1 General . 9
7.2 Specimen preparation . 10
7.3 Instrument calibration (baseline measurements) . 10
7.4 Specimen measurements . 10
7.5 Witness measurements . 10
7.5.1 Witness specimen(s) . 11
7.5.2 Procedure for the witness specimen prior to the test specimen(s) . 11
7.5.3 Measurement of the test specimen(s) . 11
7.5.4 Procedure for the witness specimen after the test specimen(s) . 11
8 Calculation and expression of results . 11
8.1 Post-processing of data . 11
8.2 Calculation of weighted transmittance . 12
8.3 Calculation of the Yellowness Index (YI) . 12
8.4 Calculation of the UV cut-off wavelength . 12
9 Uncertainty of measurements . 13
10 Test report . 13
Annex A (informative) Advanced analysis of transmittance (absorption coefficients) . 15
Annex B (informative) Applying the quantum efficiency of a specific cell technology . 17
Bibliography . 19

Table 1 – Details of the solar weight transmittance parameters . 12

 IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASUREMENT PROCEDURES FOR MATERIALS
USED IN PHOTOVOLTAIC MODULES –
Part 1-4: Encapsulants – Measurement of optical transmittance and
calculation of the solar-weighted photon transmittance,
yellowness index, and UV cut-off wavelength
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indi
...