IEC TS 63202-3:2023

Photovoltaic cells - Part 3: Measurement of current-voltage characteristics of bifacial photovoltaic cells

IEC TS 63202-3:2023 describes procedures for the measurement of current-voltage (I-V) characteristics of crystalline silicon bifacial photovoltaic (PV) cells for both laboratory and mass production applications.
This document is intended to be used for measurement of individual unencapsulated bifacial PV cells, in addition to the requirements described in IEC 60904-1 and differentiating from IEC TS 60904-1-2 which is more applicable to encapsulated PV device. Specific requirements on bifacial reference cells and calibration of solar simulators are also defined to provide useful guidance for the proposed methods.

General Information

• Status: Published
• Publication Date: 06-Feb-2023
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Drafting Committee: WG 8 - TC 82/WG 8
• Current Stage: PPUB - Publication issued
• Start Date: 02-Mar-2023
• Completion Date: 07-Feb-2023

Standards Content (Sample)

IEC TS 63202-3
®

Edition 1.0 2023-02
TECHNICAL
SPECIFICATION

colour
inside


Photovoltaic cells –
Part 3: Measurement of current-voltage characteristics of bifacial photovoltaic
cells

IEC TS 63202-3:2023-02(en)

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IEC TS 63202-3

®


Edition 1.0 2023-02




TECHNICAL



SPECIFICATION








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inside










Photovoltaic cells –

Part 3: Measurement of current-voltage characteristics of bifacial photovoltaic

cells

























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ICS 27.160 ISBN 978-2-8322-6415-7




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– 2 – IEC TS 63202-3:2023 © IEC 2023
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Methods . 7
4.1 General . 7
4.2 Double-side simultaneous irradiation . 8
4.3 Equivalent irradiation . 8
4.4 Sequential irradiation . 10
5 Apparatus . 11
5.1 General . 11
5.2 Double-side simultaneous irradiation . 11
5.3 Equivalent irradiation . 11
5.4 Sequential irradiation . 12
6 Procedures . 12
6.1 General . 12
6.2 Double-side simultaneous irradiation . 12
6.2.1 Requirements for calibration . 12
6.2.2 Procedures . 13
6.3 Equivalent irradiation . 13
6.3.1 Requirements for calibration . 13
6.3.2 Procedures . 13
6.4 Sequential irradiation . 14
6.4.1 Requirements for calibration . 14
6.4.2 Procedures . 14
7 Report . 15
Annex A (normative) Determination of bifacial I-V characteristics . 16
A.1 General . 16
A.2 Shift approximation . 16
A.3 Linear interpolation . 17

Figure 1 – Schematic procedure of double-side simultaneous irradiation method with
integrated flash conditions . 8
Figure 2 – Schematic procedure of equivalent irradiation method with sequential flash
conditions . 9
Figure 3 – Schematic procedure of equivalent irradiation method with integrated flash
conditions . 10
Figure 4 – Schematic procedure of sequential irradiation method with integrated flash
conditions . 10
Figure 5 – Separate solar simulator on both front and rear side for double-side
simultaneous irradiation . 11
Figure 6 – Setup for equivalent irradiation with adjustable intensity . 12
Figure 7 – Schematic configuration with two consecutive solar simulators . 12

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IEC TS 63202-3:2023 © IEC 2023 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

PHOTOVOLTAIC CELLS –

Part 3: Measurement of current-voltage
characteristics of bifacial photovoltaic cells

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
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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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 63202-3 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
82/2070/DTS 82/2094/RVDTS
82/2094A/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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– 4 – IEC TS 63202-3:2023 © IEC 2023
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 https://www.iec.ch/members_experts/refdocs. The main document types developed by IEC
are described in greater detail at https://www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 63202 series, published under the general title Photovoltaic cells,
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 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 document 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.

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IEC TS 63202-3:2023 © IEC 2023 – 5 –
PHOTOVOLTAIC CELLS –

Part 3: Measurement of current-voltage
characteristics of bifacial photovoltaic cells



1 Scope
This part of IEC 63202 describes procedures for the measurement of current-voltage (I-V)
characteristics of crystalline silicon bifacial photovoltaic (PV) cells for both laboratory and mass
production applications.
This document is intended to be used for measurement of individual unencapsulated bifacial
PV cells, in addition to the requirements described in IEC 60904-1 and differentiating from
IEC TS 60904-1-2 which is more applicable to encapsulated PV device. Specific requirements
on bifacial reference cells and calibration of solar simulators are also defined to provide useful
guidance for the proposed methods.
The bifacial I-V characteristics contain front standard test condition (STC), rear STC and bifacial
STC results for the bifacial PV cells under test. Thus, bifaciality as well as the power generation
capability under single-side or bifacial irradiation are evaluated.
NOTE This document does not apply to tandem or multi-junction bifacial PV cells.
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 60891, Photovoltaic devices – Procedures for temperature and irradiance corrections to
measured I-V characteristics
IEC 60904-1, Photovoltaic devices – Part 1: Measurement of photovoltaic current-voltage
characteristics
IEC TS 60904-1-2, Photovoltaic devices – Part 1-2: Measurement of current-voltage
characteristics of bifacial photovoltaic (PV) devices
IEC 60904-2, Photovoltaic devices – Part 2: Requirements for photovoltaic reference devices
IEC 60904-4, Photovoltaic devices – Part 4: Photovoltaic reference devices – Procedures for
establishing calibration traceability
IEC 60904-7, Photovoltaic devices – Part 7: Computation of the spectral mismatch correction
for measurements of photovoltaic devices
IEC 60904-9, Photovoltaic devices – Part 9: Classification of solar simulator characteristics
IEC 61215-1:2021, Terrestrial photovoltaic (PV) modules – Design qualification and type
approval – Part 1: Test requirements
IEC TS 61836, Solar photovoltaic energy systems – Terms, definitions and symbols

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– 6 – IEC TS 63202-3:2023 © IEC 2023
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TS 61836 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
bifacial standard test condition
BSTC
testing conditions that simultaneously meet the following requirements: spectral irradiance
distribution according to AM1.5 on both sides, cell temperature of 25 °C, front irradiation
−2 −2
intensity of 1 000 W∙ m , and rear irradiation intensity of 135 W∙ m
3.2
low reflection background
testing environment using anti-reflective materials and/or design to reduce the influence of
ambient light or light reflected from the testing environment on the intentional irradiance applied
to the bifacial PV cells under test
Note 1 to entry: The background is considered to be low reflection, if the difference in short-circuit current is less
than 0,3 % when the bifacial PV cell is irradiated single-sided under STC condition, and the non-irradiated side is
covered or non-covered.
3.3
bifaciality
ratio between rear and front I-V characteristics of bifacial PV cells
Note 1 to entry: By default, rear STC and front STC I-V characteristics are used to determine bifaciality.
Note 2 to entry: Main bifaciality coefficients include short-circuit current bifaciality 𝜑𝜑 , open-circuit voltage
𝐼𝐼𝐼𝐼𝐼𝐼
bifaciality 𝜑𝜑 and maximum power bifaciality 𝜑𝜑 .
𝑉𝑉𝑉𝑉𝐼𝐼 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
Note 3 to entry: The definition of bifaciality is consistent with IEC TS 60904-1-2.
Note 4 to entry: The subscripts “𝑓𝑓” and “r” stand for values derived from front- and rear-side measurements,
respectively.
3.4
bifacial reference cell
reference cell with bifacial structure similar to the bifacial PV cells under test
Note 1 to entry: The I-V characteristics of the bifacial reference cell, typically calibrated by certified calibration
laboratories, are used to calibrate the irradiance of solar simulators. Detailed requirements of bifacial reference cell
depend on the method to measure the bifacial PV cells under test.
3.5
bifacial I-V characteristics
I-V characteristics of bifacial PV cells under bifacial standard testing condition (BSTC) with
contributions from both front-side and rear-side irradiation
Note 1 to entry: Main bifacial I-V characteristics include bifacial short-circuit current 𝐼𝐼𝐼𝐼𝐼𝐼 , bifacial open-circuit
𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵
voltage 𝑉𝑉𝑉𝑉𝐼𝐼 and bifacial maximum power 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 .
𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵 𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵
Note 2 to entry: Bifacial I-V characteristics are obtained from direct measurement or equivalent calculation and can
be used to evaluate the power generation capability of bifacial PV cells under double-side irradiation.

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IEC TS 63202-3:2023 © IEC 2023 – 7 –
3.6
bifacial power gain coefficient
𝑩𝑩𝑩𝑩𝑩𝑩𝑩𝑩
𝒓𝒓𝒓𝒓𝒓𝒓
𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵
gain of 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 with respect to 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 as 𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵 =� − 1� × 100 %
𝐵𝐵𝐵𝐵𝐵𝐵𝐵𝐵 𝑓𝑓 𝑟𝑟𝑟𝑟𝑟𝑟
𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
𝑓𝑓
4 Methods
4.1 General
In most cases, bifacial PV modules are operated under double-side irradiance in the outdoor
environment. The additional energy yield gain of bifacial PV modules compared to monofacial
PV modules comes from the irradiance on the rear-side of the bifacial PV modules.
To evaluate the power generation capability of bifacial PV cells, the I-V characteristics shall be
reported at bifacial nameplate irradiance (BNPI), as defined in 3.11 of IEC 61215-1:2021. It
−2
corresponds to a front-side irradiance, 𝐺𝐺 = 1 000 𝑊𝑊∙𝑃𝑃 , and a rear-side irradiance, 𝐺𝐺 =
𝑓𝑓 𝑟𝑟
−2
135 𝑊𝑊∙𝑃𝑃 , on the device under test. Deviation of the measurement test conditions from the
reporting standard test conditions are allowed (temperature and irradiance), in which case
correction according to IEC 60891 shall be applied and taken into account in the uncertainty
calculations.
One out of the following three methods shall be used for measuring bifacial PV cells, depending
on the apparatus available. The three methods yield equivalent results following the procedures
and requirements described in this document.
a) Double-side simultaneous irradiation.
b) Equivalent irradiation.
c) Sequential irradiation.
The double-side simultaneous irradiation method requires a specific apparatus to provide
irradiance to both sides of the bifacial PV cells under test. The monofacial and bifacial I-V
characteristics of each cell under test can be measured at the same position and with a single
contacting unit and cycle.
Alternatively, the equivalent irradiation method can be used with conventional apparatus for
measuring monofacial PV cells. The equivalent irradiation intensity, 𝐺𝐺 , is determined in
𝐸𝐸
formula (1) using the bifaciality, 𝜑𝜑 , as follows:
𝐼𝐼𝐼𝐼𝐼𝐼
−2
𝐺𝐺 = 1 000 +𝜑𝜑 × 135 𝑊𝑊∙𝑃𝑃 (1)
𝐸𝐸 𝐼𝐼𝐼𝐼𝐼𝐼

When measurement time allows (typically for laboratory applications), 𝜑𝜑 is determined by
𝐼𝐼𝐼𝐼𝐼𝐼
measuring front STC and rear STC I-V characteristics of each cell under test. When
measurement time is limited (typically for mass production applications), 𝜑𝜑 can be inferred
𝐼𝐼𝐼𝐼𝐼𝐼
from a bifacial reference cell and reported as repres
...