Nanomanufacturing - Key control characteristics - Part 7-2: Nano-enabled photovoltaics - Device evaluation method for indoor light

IEC TS 62607-7-2:2023 specifies the efficiency testing of photovoltaic cells (excluding multi-junction cells) under indoor light. Although it is primarily intended for nano-enabled photovoltaic cells (organic thin-film, dye-sensitized solar cells (DSC), and Perovskite solar cells), it can also be applied to other types of photovoltaic cells, such as Si, CIGS, GaAs cells, and so on.

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IEC TS 62607-7-2:2023 - Nanomanufacturing - Key control characteristics - Part 7-2: Nano-enabled photovoltaics - Device evaluation method for indoor light Released:7/27/2023
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IEC TS 62607-7-2

Edition 1.0 2023-07

Nanomanufacturing – Key control characteristics –
Part 7-2: Nano-enabled photovoltaics – Device evaluation method for indoor

IEC TS 62607-7-2:2023-07(en)

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IEC TS 62607-7-2


Edition 1.0 2023-07



Nanomanufacturing – Key control characteristics –

Part 7-2: Nano-enabled photovoltaics – Device evaluation method for indoor





ICS 07.120; 07.030; 27.160 ISBN 978-2-8322-7255-8

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

® Registered trademark of the International Electrotechnical Commission

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– 2 – IEC TS 62607-7-2:2023 © IEC 2023
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Abbreviated terms . 9
5 Methods for measuring current-voltage characterization . 10
5.1 General . 10
5.2 Requirements . 10
5.2.1 Device under test (DUT) . 10
5.2.2 Illumination adjustment . 10
5.2.3 Measurement procedure . 11
5.3 Important additional information . 13
6 Indoor reference photovoltaic cells . 14
6.1 Requirements . 14
6.1.1 Selecting indoor reference photovoltaic cells . 14
6.1.2 Calibrating indoor reference photovoltaic cells . 14
6.2 Important notes . 15
7 Standard indoor light – Requirements . 16
7.1 Standard indoor illuminance . 16
7.2 Standard indoor light . 16
7.3 Spectral irradiance of standard indoor light . 16
8 Traceability . 19
8.1 Description – General . 19
8.2 Calibration chain example . 19
9 Temperature correction . 20
9.1 Requirements . 20
9.2 Temperature of the DUT . 20
10 Spectral-mismatch correction . 20
10.1 Requirements . 20
10.1.1 Indoor reference photovoltaic-cell method . 20
10.1.2 Recording results. 21
10.2 Important additional information . 21
11 Spectral responsivity . 21
11.1 Requirements . 21
11.1.1 Spectral responsivity, S(λ) . 21
11.1.2 Measurement methods . 21
11.2 Important notes . 21
12 Illumination sources . 22
12.1 Requirements . 22
12.1.1 Indoor spectral coincidence . 22
12.1.2 Illuminance non-uniformity . 22
12.1.3 Temporal stability . 23
12.1.4 Light source classification . 23
12.1.5 Indoor standard relative spectral responsivity . 23

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IEC TS 62607-7-2:2023 © IEC 2023 – 3 –
12.2 Illuminance non-uniformity . 35
13 Nonlinearity . 35
13.1 Requirements . 35
13.2 Important notes . 35
Annex A (informative) Explanations of the provisions, descriptions, and other content
in the standard main body of this document. . 36
A.1 Purpose of this document . 36
A.2 Target of this document . 36
A.3 Issues discussed during deliberation . 36
A.3.1 Adjusting light intensity with an illuminometer . 36
A.3.2 Indoor spectral coincidence . 36
A.3.3 Stability of a DUT (5.2.2) . 37
A.3.4 Maximum power (P ). 37
A.4 Supplemental remarks on requirements . 38
A.4.1 Requirements for the DUTs (5.2.1) . 38
A.4.2 Standard indoor light (Clause 7) . 38
A.4.3 Methods for adjusting illuminance (5.2.2) . 39
A.4.4 Quasi-reference photovoltaic cell . 42
A.4.5 Standard indoor light (7.1, 7.2) . 42
A.4.6 Spectral responsivity (11.1.2) . 42
A.4.7 Illumination source and indoor spectral coincidence (12.1.1) . 43
A.4.8 Illumination sources and non-uniformity of brightness (12.1.2) . 44
A.4.9 Temporal stability (12.1.3) . 44
A.4.10 Classification of illumination sources (12.1.5) . 44
A.4.11 Nonlinearity (13.1) . 45
A.5 Correspondence between this document and the IEC 60904 series . 45
Bibliography . 47

Figure 1 – Spectral irradiance of standard indoor light at 1 000 lx . 19
Figure 2 – Calibration chain example . 20
Figure 3 – Standard relative spectral responsivity . 34
Figure A.1 – Configurations of illuminance adjusting methods described in a) A.4.3.2,
b) A.4.3.3 and c) A.4.3.4 . 39
Figure A.2 – PRISM or spectroradiometer method . 40
Figure A.3 – Measurement laboratories. 41
Figure A.4 – Temporal fluctuation of illuminance of a fluorescent lamp . 44

Table 1 – Standard indoor illuminance . 12
Table 2 – Result record . 13
Table 3 – Calibration record . 15
Table 4 – Spectral irradiance (mW/m /nm) of standard indoor light at 1 000 lx . 16
Table 5 – Light source classification . 23
Table 6 – Indoor standard relative spectral responsivity (%) . 24
Table A.1 – Spectral coincidence of F to reference spectrum CIE FL10 . 42
Table A.2 – Spectral coincidence of L to reference spectrum CIE LED-B4 . 42
Table A.3 – Correspondence between clauses of this document and IEC 60904 . 46
Table A.4 – New concepts in this document derived from IEC 60904 . 46

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Part 7-2: Nano-enabled photovoltaics –
Device evaluation method for indoor light

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
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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.
IEC TS 62607-7-2 has been prepared by IEC technical committee 113: Nanotechnology for
electrotechnical products and systems. It is a Technical Specification.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
113/710/DTS 113/737/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.

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IEC TS 62607-7-2:2023 © IEC 2023 – 5 –
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 The main document types developed by IEC are
described in greater detail at
A list of all parts of the IEC TS 62607 series, published under the general title
Nanomanufacturing – Key control characteristics, 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 in the data related to the
specific document. At this date, the document will be
• transformed into an International Standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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– 6 – IEC TS 62607-7-2:2023 © IEC 2023
Commercialization of nano-enabled solar cells, such as organic solar cells, is being promoted
by utilizing their advantages over conventional solar cells, such as light weight, flexibility, colour,
transparency, and coating processability. Energy harvesting applications that generate power
using indoor light have been recognized as important applications for nano solar cells in
conjunction with recent advances in the Internet of Things. In general, nano solar cells have a
large band gap and are suitable for power generation under indoor lighting whose spectra are
localized in the visible light region. In addition, since the low illuminance characteristics can be
improved by devising the configuration, it is expected to be suitable for energy harvesting using
indoor light.
The IEC 60904 series specifies evaluation methods for sunlight. In IEC 60904, the most
important factors in evaluating a solar cell are the selection of a light source and the method of
adjusting its irradiance for measurement. By changing the light source from sunlight to indoor
light, an evaluation method under indoor light can be obtained. The clause structure of this
document corresponds to that of IEC 60904. While light sources are limited to sunlight in the
outdoor environment, various light sources are used indoors, such as fluorescent lamps and
LED lamps in addition to sunlight. The indoor brightness is expressed by illuminance in lux (lx),
which takes into account the sensitivity of the human eye. Strictly speaking, since the spectral
characteristics of the eyes are different from those of solar cells, there is not always a
correlation between the illuminance and the power generation of solar cells. For example, a
crystalline Si solar cell could generate power using only near-infrared light which is invisible to
human eyes, i.e. zero lux. However, high-efficiency lighting other than incandescent lamps has
a spectrum concentrated in the visible light region, thus expressing the efficiency of an indoor
solar cell based on the spectrum of sunlight is not appropriate.
In this document, such uncertainties due to the use of illuminance instead or irradiance are
eliminated by setting a reference spectrum for indoor light sources. The reference indoor light
spectra are representatives of the spectrum of light sources used for indoor lighting, are defined
only between 380 nm and 780 nm, and have no component outside of this wavelength range.
Therefore, this document provides a method to evaluate solar cells with illuminance. Since the
illuminance is obtained by the overlap integral of the spectral irradiance of the light source and
the luminosity, there could be an infinite number of spectral irradiances that give the same
illuminance. A large error could arise due to light in the wavelength region with low luminosity.
In an extreme case, invisible light has a finite output even at zero illuminance. In this document,
however, the output by zero lux illuminance is supposed to be zero, that is, the output is not
The target of this document is to define the output of a solar cell in a bright (finite illuminance)
indoor environment. The output with light other than the reference spectrum is out of this target.
If it is necessary to include such cases, they will be treated as individual cases. In that case,
one would extend the reference spectrum and build an evaluation technique that uses irradiance
instead of illuminance. Special illumination conditions can be used by using a user-defined
reference spectrum. In this case, however, illuminance can be meaningless if the illumination
contains a significant amount of invisible light.
Illumination includes not only the light that the eyes of humans are sensitive to, but also the
infrared energy contained in incandescent lighting and sunlight that enters from outdoors. But
because incandescent lighting is used less and less due to its poor energy efficiency, this
document defines measurement methods with two standard indoor light sources specified by
CIE: FL10 and LED-B4, corresponding to the fluorescent lamp and the white LED lamp,
respectively, the correlated colour temperatures (CCT) of which are approximately 5 000 K.
Other light sources such as sunlight or incandescent lamps are not appropriate because they
contain much invisible infrared light and illuminance is not a good measure for performance
evaluation of photovoltaic devices, because they contain a significant amount of invisible light.
This document, along with FL10 and LED-B4, establishes methods for evaluating photovoltaic
cells under indoor conditions. This document assumes that an arbitrary photovoltaic cell will be
measured under indoor lighting. For requirements not listed in this document, refer to the
relevant normative references.

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IEC TS 62607-7-2:2023 © IEC 2023 – 7 –

Part 7-2: Nano-enabled photovoltaics –
Device evaluation method for indoor light

1 Scope
This Technical Specification specifies the efficiency testing of photovoltaic cells (excluding
multi-junction cells) under indoor light. Although it is primarily intended for nano-enabled
photovoltaic cells (organic thin-film, dye-sensitized solar cells (DSC), and Perovskite solar
cells), it can also be applied to other types of photovoltaic cells, such as Si, CIGS, GaAs cells,
and so on.
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.
JIS C 1609-1, Illuminance meters – Part 1: General measuring instruments
DIN 5032-7, Photometry – Part 7: Classification of illuminance meters and luminance meters
ISO/CIE 19476, Characterization of the performance of illuminance meters and luminance
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
• IEC Electropedia: available at
• ISO Online browsing platform: available at
response time
time required for current to respond after a change is made to the applied voltage
  
Note 1 to entry: Response time is represented by τ in the formula  for expressing
It() I(0)+∆I 1− exp−
  
  τ
change in current over time.
indoor primary reference photovoltaic cell
photovoltaic cell calibrated from a radiometer, standard detector, or standard indoor light that
is traceable to SI units

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– 8 – IEC TS 62607-7-2:2023 © IEC 2023
indoor standard relative spectral responsivity
measure to define indoor spectral coincidence without relying on the device under test itself
indoor reference photovoltaic cell
photovoltaic cell used to adjust the intensity of the indoor light source
indoor spectral coincidence
measure of spectral matching between standard indoor light and the illumination source used
for a measurement
Note 1 to entry: It is expressed as a ratio of short-circuit currents calculated from the spectral responsivity of the
photovoltaic cell.
indoor secondary reference photovoltaic cell
photovoltaic cell calibrated from the indoor primary reference photovoltaic cell
indoor working reference photovoltaic cell
photovoltaic cell calibrated from the indoor secondary reference photovoltaic cell
standard indoor light
light source with a defined spectral distribution that is used when evaluating photovoltaic cells
under indoor light
Note 1 to entry: It covers a variety of indoor light sources, and two types of standard indoor light are adopted in this
standard indoor illuminance
illuminance values used when evaluating photovoltaic cells under indoor light
Note 1 to entry: The standard indoor illuminance values are 50 lx, 200 lx and 1 000 lx.
fluorescent lamp
light source that operates by electrically exciting mercury vapour and then converting the
luminescence generated into visible light using a phosphor
dye-sensitized solar cell
photovoltaic cell created by coating metal-oxide particles (such as titanium oxide or zinc oxide)
with a molecular dye then immersing them in an ionically conductive electrolyte
intensity of a light that illuminates a surface, as perceived by the human eye
Note 1 to entry: Illuminance is expressed in units of lux (lx).
correlated colour temperature
temperature of the black-body radiator whose CIE (u, v), or (u′, 2/3 v′), colour coordinate is
closest to that of a light source
Note 1 to entry: See Ohno, Y., "Practical Use and Calculation of CCT and Duv", Leukos, 10:1, 47-55. (2013).

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IEC TS 62607-7-2:2023 © IEC 2023 – 9 –
measurement delay time
interval of time between the changing of the applied voltage and the start of the current
measurement when measuring an I-V curve by varying an externally applied voltage
white LED lamp
light source that produces white light by using a fluorescent substance to convert the
wavelength of light generated by violet or ultraviolet LEDs
luminosity function
numerical representation of the relative sensitivity of the human eye to the different wavelengths
of visible light
perovskite solar cell
photovoltaic cell containing a semiconductor with a perovskite structure composed of
monovalent cations, divalent metal ions, and halogen ions
organic photovoltaic cell
photovoltaic cell containing an organic semiconductor or dye in the layers where light absorption
and charge separation take place
maximum power point tracking
technique for finding the operating point (I-V or load characteristic) at which a device generates
the maximum amount of electric energy under given photo-irradiation conditions
Note 1 to entry: It is typically used for adjusting a photovoltaic cell's optimal operating point under changing
conditions such as weather and solar altitude angle, but it can also be utilized to determine the conversion efficiency
of a cell when assessing its I-V curve is not feasible.
programmable reference cell system for irradiance adjustment by spectral
method for adjusting the intensity of

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