IEC 60904-7:2019

IEC 60904-7 ®
Edition 4.0 2019-08
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Photovoltaic devices –
Part 7: Computation of the spectral mismatch correction for measurements of
photovoltaic devices
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.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
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and withdrawn publications.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 since 2002. Some entries have been
IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and
If you wish to give us your feedback on this publication or CISPR.

need further assistance, please contact the Customer Service

Centre: sales@iec.ch.
IEC 60904-7 ®
Edition 4.0 2019-08
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Photovoltaic devices –
Part 7: Computation of the spectral mismatch correction for measurements of

photovoltaic devices
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-7329-6

– 2 – IEC 60904-7:2019 RLV © IEC 2019
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
Apparatus . 7
4 Description of method . 7
5 Determination of spectral response responsivity . 7
6 Determination of test spectrum . 9
7 Determination of the spectral mismatch factor . 9
7.1 General . 10
7.2 Simplified formula for a thermopile detector (pyranometer) . 12
8 Report . 9
Bibliography .

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC DEVICES –
Part 7: Computation of the spectral mismatch correction
for measurements of photovoltaic devices

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
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.
This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.

– 4 – IEC 60904-7:2019 RLV © IEC 2019
International Standard IEC 60904-7 has been prepared by IEC technical committee 82: Solar
photovoltaic energy systems.
This fourth edition cancels and replaces the third edition published in 2008. It constitutes a
technical revision.
The main technical changes with respect to the previous edition are as follows:
• For better compatibility and less redundancy, the clause “Determination of test spectrum”
refers to IEC 60904-9.
• The spectral mismatch factor is called SMM instead of MM to enable differentiation to the
angular mismatch factor AMM and spectral angular mismatch factor SAMM.
• Formulae for the derivation and application of the spectral mismatch factor SMM are
added.
• Links to new standards are given, e.g. concerning multi-junction devices.
• Corrected wording (responsivity instead of response and irradiance instead of intensity).
The text of this International Standard is based on the following documents:
FDIS Report on voting
82/1590/FDIS 82/1605/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of IEC 60904 series, published under the general title Photovoltaic devices,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
PHOTOVOLTAIC DEVICES –
Part 7: Computation of the spectral mismatch correction
for measurements of photovoltaic devices

1 Scope and object
This part of IEC 60904 describes the procedure for correcting the bias spectral mismatch
error introduced in the testing of a photovoltaic device, caused by the mismatch between the
test spectrum and the reference spectrum (e.g. AM1.5 spectrum) and by the mismatch
between the spectral responses responsivities (SR) of the reference cell device and of the
device under test specimen and therewith reduce the systematic uncertainty. The procedure
applies only to photovoltaic devices linear in SR as defined in IEC 60904-10. This procedure
is valid for single-junction devices but the principle may be extended to cover multi-junction
devices.
The purpose of this document is to give guidelines for the correction of measurement bias the
spectral mismatch error, should there be a spectral mismatch betweenthe test spectrum and
the reference spectrum as well as between the reference device SR and the device under test
specimen SR. The calculated spectral mismatch correction is only valid for the specific
combination of test and reference devices measured with a particular test spectrum.
Since a PV device has a wavelength-dependent response spectral responsivity, its
performance is significantly affected by the spectral distribution of the incident radiation,
which in natural sunlight varies with several factors such as location, weather, time of year,
time of day, orientation of the receiving surface, etc., and with a solar simulator varies with its
type and conditions. If the irradiance is measured with a thermopile-type radiometer (that is
not spectrally selective) or with a PV reference solar cell device (IEC 60904-2), the spectral
irradiance distribution of the incoming light must be known to make the necessary corrections
to obtain the performance of the PV device under the reference solar spectral irradiance
distribution defined in IEC 60904-3.
If a reference PV device or a thermopile type detector is used to measure the irradiance, then,
following the procedure given in this document, it is possible to calculate the spectral
mismatch correction necessary to obtain the short-circuit current of the test PV device under
test under the reference solar spectral irradiance distribution in IEC 60904-3 or any other
reference spectrum. If the reference PV device has the same relative spectral response
responsivity as the test PV device under test then the reference device automatically takes
into account deviations of the real light measured spectral irradiance distribution from the
standard reference spectral irradiance distribution, and no further correction of spectral bias
mismatch errors is necessary. In this case, location and weather conditions are not critical
when the reference device method is used for outdoor performance measurements provided
both reference cell and test PV device have the same relative spectral response under natural
sunlight. Also, for identical relative SRs, the spectral classification of the simulator is not
critical for indoor measurements with solar simulators.
If the performance of a PV device is measured using a known spectral irradiance distribution,
its short-circuit current at any other spectral irradiance distribution can be computed using the
spectral response responsivity of the PV test device under test.
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

– 6 – IEC 60904-7:2019 RLV © IEC 2019
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60891, Photovoltaic devices – Procedures for temperature and irradiance corrections to
measured I-V characteristics of crystalline silicon photovoltaic devices
IEC 60904-1, Photovoltaic devices – Part 1: Measurement of photovoltaic current-voltage
characteristics
IEC 60904-1-1, Photovoltaic devices – Part 1-1: Measurement of current-voltage
characteristics of multi-junction photovoltaic (PV) devices
IEC 60904-2, Photovoltaic devices – Part 2: Requirements for photovoltaic reference solar
devices
IEC 60904-3, Photovoltaic devices – Part 3: Measurement principles for terrestrial
photovoltaic (PV) solar devices with reference spectral irradiance data
IEC 60904-8, Photovoltaic devices – Part 8: Measurement of spectral response responsivity
of a photovoltaic (PV) device
IEC 60904-8-1, Photovoltaic devices – Part 8-1: Measurement of spectral responsivity of
multi-junction photovoltaic (PV) devices
IEC 60904-9, Photovoltaic devices – Part 9: Solar simulator performance requirements
IEC 60904-10, Photovoltaic devices – Part 10 Methods of linearity measurement
IEC 61215, Crystalline silicon terrestrial photovoltaic (PV) modules – Design qualification and
type approval
IEC 61646, Thin film terrestrial photovoltaic (PV) modules – Design qualification and type
approval
IEC TS 61836, Solar photovoltaic energy systems – Terms, definitions and symbols
ISO 9288:1989, Thermal insulation – Heat transfer by radiation – Physical quantities and
definitions
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TS 61836 and
ISO 9288 apply.
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
NOTE The index e for the energetic quantities is omitted, as in this document the quantities need not be
distinguished from photometric quantities. Thus, for the quantity irradiance the quantity symbol E instead of the
quantity symbol E is used.
e
The index λ that denotes that the irradiance is differentiated with respect to the wavelength λ and not to the
frequency ν to obtain the spectral irradiance E (λ) is mostly omitted for clarity. Therefore, the spectral irradiance is
λ
referred to herein as E(λ).
4 Description of method
For many PV devices, the shape of the I-V characteristic depends on the short-circuit current
and the device temperature, but not on the spectrum used to generate the short-circuit
current. For these devices, the correction of spectrum mismatch or spectral response
responsivity mismatch is possible using the following procedure. For other devices, a
measurement of the I-V characteristic shall be done using a light source with the appropriate
spectrum.
A correction is not necessary if either the test spectrum is identical to the reference spectrum
(see IEC 60904-3) or if the test specimen’s device under test’s relative spectral response
responsivity is identical to the reference cell device relative spectral response responsivity. In
this case, the reading as obtained from the reference cell device specifies which intensity
irradiance at the reference spectrum will generate the same short-circuit current in the test
device under test as the test spectrum.
If there is a mismatch between spectra (spectrum mismatch) as well as spectral responses
responsivities (spectral responsivity mismatch) then a mismatch correction should be
calculated. As the test spectrum and the spectral responsivities always have an assigned
measurement uncertainty, for the calculation of the total uncertainty the uncertainty of
spectral mismatch shall be always taken into account.
Due to the mismatch in spectra and spectral responses, the reading of the reference cell (see
IEC 60904-2) does not give the intensity of the reference spectrum that generates the short-
circuit current as measured for the test device. One must determine the effective irradiance of
the reference spectrum that generates the same short-circuit current in the test device as
generated by the test spectrum at the measured irradiance G .
meas
G = MM × G (1)
eff at ref spectrum meas
where G is the irradiance as measured by the reference device with its specific spectral
meas
response S (λ) and MM is the spectral mismatch factor as determined in Clause 7.
ref
For a measurement to be referred to the reference spectral irradiance, two correction methods
are possible:
a) If possible, adjust the simulator intensity so that the effective irradiance as determined by
equation (1) equals the reference irradiance G (e.g. 1 000 W/m for STC, as defined in
ref
IEC 61215 and IEC 61646). That is to say that the simulator intensity as measured by the
reference cell using its calibration value given for the reference spectrum has to be set to
G  = G /MM (2)
meas ref
Thus, the inverse mismatch factor 1/MM gives the degree by which the simulator intensity
has to be adjusted, if the device is linear (see IEC 60904-10). Now, the simulator
spectrum +++at this irradiance with its actual simulator spectrum generates the same
short-circuit current as the reference spectrum at the reference intensity. Proceed to
measure the I-V characteristic per IEC 60904-1.
b) Otherwise, measure the I-V characteristic using the given simulator intensity. Determine
the effective irradiance at the reference spectrum using equation (1). Then transfer the I-V
characteristic to the reference irradiance using IEC 60891 with the effective irradiance
determined from equation (1).
Method a) is preferred for simulated sunlight (see IEC 60904-9), as the actual measurement is
performed at the correct short-circuit current, minimising non-linearity errors. Method b) is
usually chosen for outdoor measurements, if the light intensity cannot be easily controlled.

– 8 – IEC 60904-7:2019 RLV © IEC 2019
When a mismatch in spectra and/or spectral responsivities exists, the reading of the reference
device (see IEC 60904-2) does not give the irradiance of the test spectrum that would
generate the same short-circuit current for the device under test as the reference spectrum.
Therefore, one shall determine the effective irradiance of the test spectrum, E that
eff
generates the same short-circuit current in the device under test as generated by the
reference spectrum.
E = SMM × E (1)
eff meas
where E is the irradiance as measured by the reference device with its specific spectral
meas
responsivity s (λ) before applying spectral mismatch corrections and SMM is the spectral
ref
mismatch factor as determined in Clause 7.
For a measurement to be referred to the reference spectral irradiance, two correction methods
are possible:
a) If possible, adjust the measured test spectrum irradiance so that the effective irradiance
as determined by formula (1) equals the reference irradiance E (e.g. 1 000 W/m2 for
ref
STC, as defined in IEC TS 61836). That is to say that the solar simulator’s irradiance as
measured by the reference device using its calibration value before applying spectral
mismatch correction given for the reference spectrum has to be set to
E = E / SMM (2)
meas ref
Thus, the inverse mismatch factor 1/SMM gives the degree by which the solar simulator’s
irradiance has to be adjusted. Now, the solar simulator spectrum at this irradiance with its
actual measured test spectrum generates the same short-circuit current for the device
under test as would be obtained under the reference spectrum. If the adjustment is done
without using the feedback of the reference device (e.g. using a control dial), the adjusted
value should be checked using a reference device. Thereafter, proceed to measure the I-V
characteristic as per IEC 60904-1.
b) Otherwise, measure the I-V characteristic using the measured spectral irradiance.
Determine the effective irradiance at the reference spectrum using formula (1). Then
translate the I-V characteristic to the reference irradiance using IEC 60891 with the
effective irradiance determined from formula (1).
Method a) is preferred for simulated sunlight, as the actual measurement is performed at the
correct reference irradiance, minimising non-linearity errors of the device under test and
errors arising from the I-V curve translation. Method b) is usually chosen for measurements
under natural sunlight, as the spectral irradiance of sunlight cannot be easily adjusted.
4 Apparatus
4.1 Spectral response measurement set up according to IEC 60904-8.
4.2 Apparatus for measurement of PV current voltage characteristics according to
IEC 60904-1.
4.3 Spectroradiometer capable of measuring the spectral irradiance in the test plane in a
spectral range exceeding that of the spectral responses of the reference and test devices.
NOTE 1 For example spectroradiometer measurements are described in CIE 63 (1984).
NOTE 2 The input head of the spectroradiometer and the test device should have a similar field of view
with a similar dependency of the solid angle.

5 Determination of spectral response responsivity
5.1 The relative spectral response of the test specimen shall be measured according to
IEC 60904-8. If not available, the relative spectral responsivity of the device under test and
the reference device shall be measured according to IEC 60904-8 for single-junction devices
and IEC 60904-8-1 for multi-junction devices under test.
5.2 If not available from the calibration documents, the relative spectral response of the
reference device shall be measured according to IEC 60904-8. Take care not to use the
differential spectral responsivity, but the spectral responsivity, that can be calculated using
differential spectral responsivities at different bias level (see IEC 60904-8).
6 Determination of test spectrum
6.1 Mount the input head of the spectroradiometer in the position where the test device will
subsequently be mounted, or as close as possible to that location. It shall be mounted
coplanar to the test specimen within ± 2°.
6.2 Record the spectrum of the light source. For simulator measurements, steps of 2 nm or
less with 2-5 nm bandwidths are recommended. For outdoor spectra, steps and bandwidth of
up to 10 nm are allowable. Verify that the total irradiance does not vary by more than ± 2 %
during this measurement. If necessary, apply a linear intensity correction to all measurement
points with respect to the actual total irradiance. Alternatively, several scans can be taken,
they shall agree within ± 2 %. Then determine the average relative spectrum.
6.3 If the acquisition time for a full spectrum is larger than the acquisition time for the I-V
characteristic, or if the light source is not spectrally stable over time (e.g. flash simulators or
natural sunlight), special care must be given to determine the correct test spectrum.
NOTE 1 A pulsed simulator may not be spectrally stable during the I-V measurement period. Also, at the rising
and falling edge of the pulse, the spectrum may be different from the spectrum during the designated measurement
time. Therefore, it may not be correct to measure the spectrum with an integration time including the rise and tail of
the pulse.
NOTE 2 Outdoor spectra may not be stable due to changes in the atmospheric conditions.
The relative spectral irradiance distribution of the radiation source shall be measured
according to IEC 60904-9. This shall be done for simulated as well as natural sunlight.
7 Determination of the spectral mismatch factor
Determine the spectral mismatch factor from
E (λ)S (λ) dλ E (λ) S (λ) dλ
ref ref meas sample
∫ ∫
MM =
(3)
E (λ )S (λ ) dλ E (λ) S (λ) dλ
meas ref ref sample
∫ ∫
where
E ( λ ) is the irradiance per unit bandwidth at a particular wavelength λ , of the reference
ref
spectral irradiance distribution, for example as given in IEC 60904-3;
λ λ
E ( ) is the irradiance per unit bandwidth at a particular wavelength , of the spectral
meas
irradiance distribution of the incoming light at the time of measurement;
S (λ) is the spectral response of the reference PV device;
ref
S (λ) is the spectral response of the test PV device.
sample
– 10 – IEC 60904-7:2019 RLV © IEC 2019
All integrals must be performed in the full spectral range where the reference device and the
sample are spectrally sensitive.
NOTE 1 The spectral irradiance distributions and the spectral responses can be given on an absolute or relative.
scale.
NOTE 2 Due to the irregular shape of the solar and simulator spectra, spectral responses should be interpolated
to the wavelength points of the spectral irradiance measurements, not vice versa.
NOTE 3 Equation 3 is valid for single junction devices, but may be used for multi-junction devices. For multi-
junction devices, the calculation must be performed for each junction in the device, using its spectral response
including the spectral filtering caused by the junctions above the junction under consideration. The test report
should specify the mismatch factors and the relative current generation of the individual junctions.
NOTE 4 The integral boundaries should be the boundary wavelengths of the SR.
In the case, that absolute spectra and absolute spectral responses are used for the analysis,
Equation 3 can be interpreted as
I I
sc,ref,E sc,sample,E
ref meas
MM =
(4)
I I
sc,ref,E sc,sample,E
meas ref
where
I is the short-circuit current of the test sample under the reference spectrum;
sc, sample, E
ref
I  is the short-circuit current of the reference device under the reference
sc, ref, E
ref
spectrum;
I is the short-circuit current of the test sample under the measured spectrum;

sc, sample, E
meas
I  is the short-circuit current of the reference device under the measured
sc, ref, E
meas
spectrum
( ) ( )
because I = E λ S λ dλ
sc
∫
7.1 General
Determine the spectral mismatch factor from :
E (λ)s (λ) dλ E (λ) s (λ) dλ
ref ref meas DUT
∫ ∫
SMM =
(3)
E (λ)s (λ) dλ E (λ) s (λ) dλ
meas ref ref DUT
∫ ∫
where
E (λ) λ
is the irradiance per unit bandwidth at a particular wavelength , of the reference
ref
spectral irradiance distribution (reference spectrum), for example as given in
IEC 60904-3;
E (λ)
is the irradiance per unit bandwidth at a particular wavelength λ , of the spectral
meas
irradiance distribution of the incoming light at the time of measurement (test
spectrum);
s (λ)
is the spectral responsivity of the reference PV device at reference conditions;
ref
s (λ)
is the spectral responsivity of the device under test at reference conditions.
DUT
All integrals shall be performed in the entire spectral range where the respective quantities
are not zero. The irradiance distribution shall be known over the entire combined spectral
range of sensitivity of the device under test and the reference PV device.
The spectral irradiance distributions and the spectral responsivities can be given on an
absolute or relative scale.
If the relative test spectrum would be identical to relative reference spectrum, then the
SMM is 1 and spectral mismatch corrections can be neglected, even if the spectral
responsivities of the devices differ. However, considering that the test spectrum as a physical
quantity has a measurement uncertainty assigned to it that is not zero, the SMM will still have
a measurement uncertainty contribution different to zero. Thus, the SMM factor cannot be
neglected when considering its measurement uncertainty contribution, though the value of the
factor is 1.
If the relative spectral responsivity of the device under test would be identical to the relative
spectral responsivity of the reference device, then the SMM is 1, even if the relative spectral
irradiance distributions differ (perfectly matched reference device). Considering that both
spectral responsivities have a measurement uncertainty that is not zero, the SMM will still
have a measurement uncertainty contribution different to zero. Thus, the SMM factor cannot
be neglected when considering its measurement uncertainty contribution, though the value of
the factor is 1.
Due to the irregular shape of the reference and measured spectra, spectral responsivities
should be interpolated to the wavelength points of the spectral irradiance measurements, not
vice versa.
Formula (3) is valid for single-junction devices, but may be used for multi-junction devices.
For multi-junction devices, the calculation shall be performed for each junction in the device,
using its spectral responsivity including the spectral filtering caused by the junctions above
the junction under consideration. The test report should specify the spectral mismatch factors
and the relative current generation of the individual junctions. For multi-junction devices, refer
to IEC 60904-1-1 (I-V) and IEC 60904-8-1 (SR).
The spectral responsivities used shall be valid at the level of target irradiance for which the
SMM factor applies because for non-linear devices they may vary with the level of irradiance.
Derivation of SMM
In the case that absolute spectral irradiances and absolute spectral responsivities are used
for the analysis, Formula (3) can be interpreted as:
I I
ref,E DUT,E
ref meas
(4)
SMM =
I I
ref,E DUT,E
meas ref
where
𝐼𝐼 is the short-circuit current of the device under test that would be obtained
DUT, 𝐸𝐸
ref
under the reference spectrum 𝐸𝐸 (𝜆𝜆);
ref
𝐼𝐼  is the short-circuit current of the reference device that would be obtained
ref, 𝐸𝐸
ref
under the reference spectrum 𝐸𝐸 (𝜆𝜆);
ref
𝐼𝐼 is the short-circuit current of the device under test under the measured test
DUT, 𝐸𝐸
meas
( )
spectrum 𝐸𝐸 𝜆𝜆 ;
meas
𝐼𝐼 is the short-circuit current of the reference device under the measured test

ref, 𝐸𝐸
meas
spectrum 𝐸𝐸 (𝜆𝜆)
meas
– 12 – IEC 60904-7:2019 RLV © IEC 2019
because 𝐼𝐼 ∝ 𝐸𝐸 (𝜆𝜆) 𝑠𝑠(𝜆𝜆) 𝑑𝑑𝜆𝜆.
∫
sc 𝜆𝜆
Using these quantities, one can write according to the definition of the responsivity:
𝐼𝐼 𝐼𝐼 𝐼𝐼 𝐼𝐼
DUT, 𝐸𝐸 DUT, 𝐸𝐸 DUT, 𝐸𝐸 𝐼𝐼 1 𝐼𝐼
ref, 𝐸𝐸 DUT, 𝐸𝐸 DUT, 𝐸𝐸
ref ref ref meas meas meas
𝑠𝑠 = =𝑠𝑠 ∙ =𝑠𝑠 ∙ ∙ =𝑠𝑠 ∙ ∙
DUT ref ref ref
𝐸𝐸 𝐼𝐼 𝐼𝐼 𝐼𝐼 𝐼𝐼 𝑆𝑆𝑆𝑆𝑆𝑆 𝐼𝐼
�����
ref ref, 𝐸𝐸 ref, 𝐸𝐸 �DUT��, �𝐸𝐸����re�f, �𝐸𝐸��� �r�e�f, �𝐸𝐸���
meas meas meas
ref ref
(5)
What you want
1 What you
to know measure
where
𝑠𝑠 is the (integral) responsivity of the device under test under reference

DUT
spectrum:
𝐼𝐼
DUT, 𝐸𝐸
ref
𝑠𝑠 =
DUT
𝐸𝐸
ref
𝑠𝑠 is the (integral) responsivity of the reference device under reference
ref
𝐼𝐼
ref, 𝐸𝐸
ref
spectrum: 𝑠𝑠 =
ref
𝐸𝐸
ref
2.
𝐸𝐸 is the reference irradiance, typically 1 000 W/m

ref
7.2 Simplified formula for a thermopile detector (pyranometer)
IEC 60904-1 also allows the use of a thermopile detector (pyranometer) as reference device
for the measurement of the test irradiance (under steady-state simulated or natural sunlight).
s (λ) =1
As their spectral responsivity is nearly spectrally independent, one can assume .
ref
In this case the formulae are modified as follows:
E (λ) dλ E (λ) s (λ) dλ
ref meas DUT
∫ ∫
SMM =
(6)
E (λ)dλ E (λ) s (λ) dλ
meas ref DUT
∫ ∫
E E (λ) s (λ) dλ
ref meas DUT
∫
SMM =
(7)
E E (λ) s (λ) dλ
meas ref DUT
∫
E I
ref DUT,E
meas
(8)
SMM =
E I
meas DUT,E
ref
where
2;
E is the reference irradiance, typically 1 000 W/m
ref
E is the irradiance measured by the thermopile detector.
meas
In Formula (6) the two integrals in the first fraction have to be taken over the entire
wavelength range of sensitivity of the thermopile detector. This in general poses a problem,
as the sensitivity range of such detectors is larger than the range readily measurable with
spectroradiometers.
Formula (7) offers a solution by just using the measured irradiance. However, in this case the
E (λ)
spectral irradiance of the test spectrum has to be on an absolute scale.
meas
8 Report
The following information should be given in the test report according to IEC 60904-1.
a) If the spectral mismatch is used for the irradiance correction of a measurement based on
IEC 60904-1 or another relevant standard, the calculated spectral mismatch factor, the
identification of the test device under test and the reference device as well as their
spectral responses responsivities according to their test report (IEC 60904-8 or
IEC 60904-8-1), the test spectrum and the reference spectrum or a reference to it should
all be included in the test report, along with the method used to calculate the integrals.
If the reference device and the device under test are of different dimensions (active area),
the dimensions should be specified in the test report.
b) If a perfectly matched reference device is used and no mismatch correction is applied, the
identification of the test device under test and the reference device, as well as the spectral
responses responsivities of reference and test devices device under tests according to
their test report (IEC 60904-8 or IEC 60904-8-1) should be included in the test report.
If the reference device and the device under test are of different dimensions (active area),
the dimensions should be specified in the test report.
If the spectral response responsivity of the device under test cannot be measured, the test
report should include the criteria used to define the equivalency of the spectral responses
responsivities.
c) Note that the spectral mismatch factor determined by applying this procedure is only valid
for correcting a measurement of the specific device under test considered with the
particular reference device and test spectrum used to calculate the SMM. When
measuring this device under test under different spectral irradiance (being it simulated or
natural sunlight) and/or with a different reference device, the spectral mismatch factor
shall be recalculated.
– 14 – IEC 60904-7:2019 RLV © IEC 2019
Bibliography
CIE 63:1984, The Spectroradiometric Measurement of Light Sources

___________
IEC 60904-7 ®
Edition 4.0 2019-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Photovoltaic devices –
Part 7: Computation of the spectral mismatch correction for measurements of
photovoltaic devices
Dispositifs photovoltaïques –
Partie 7: Calcul de la correction de désadaptation des réponses spectrales dans
les mesures de dispositifs photovoltaïques

– 2 – IEC 60904-7:2019 © IEC 2019
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Description of method . 6
5 Determination of spectral responsivity . 8
6 Determination of test spectrum . 8
7 Determination of the spectral mismatch factor . 8
7.1 General . 8
7.2 Simplified formula for a thermopile detector (pyranometer) . 10
8 Report . 10

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC DEVICES –
Part 7: Computation of the spectral mismatch correction
for measurements of photovoltaic devices

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
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 60904-7 has been prepared by IEC technical committee 82: Solar
photovoltaic energy systems.
This fourth edition cancels and replaces the third edition published in 2008. It constitutes a
technical revision.
The main technical changes with respect to the previous edition are as follows:
• For better compatibility and less redundancy, the clause “Determination of test spectrum”
refers to IEC 60904-9.
• The spectral mismatch factor is called SMM instead of MM to enable differentiation to the
angular mismatch factor AMM and spectral angular mismatch factor SAMM.
• Formulae for the derivation and application of the spectral mismatch factor SMM are
added.
• Links to new standards are given, e.g. concerning multi-junction devices.

– 4 – IEC 60904-7:2019 © IEC 2019
• Corrected wording (responsivity instead of response and irradiance instead of intensity).
The text of this International Standard is based on the following documents:
FDIS Report on voting
82/1590/FDIS 82/1605/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of IEC 60904 series, published under the general title Photovoltaic devices,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
...