ASTM E1125-16(2020)
(Test Method)Standard Test Method for Calibration of Primary Non-Concentrator Terrestrial Photovoltaic Reference Cells Using a Tabular Spectrum
Standard Test Method for Calibration of Primary Non-Concentrator Terrestrial Photovoltaic Reference Cells Using a Tabular Spectrum
SIGNIFICANCE AND USE
5.1 The electrical output of a photovoltaic device is dependent on the spectral content of the illumination source, its intensity, and the device temperature. To make standardized, accurate measurements of the performance of photovoltaic devices under a variety of light sources when the intensity is measured with a calibrated reference cell, it is necessary to account for the error in the short-circuit current that occurs if the relative quantum efficiency of the reference cell is not identical to the quantum efficiency of the device to be tested. A similar error occurs if the spectral irradiance distribution of the test light source is not identical to the desired reference spectral irradiance distribution. These errors are accounted for by the spectral mismatch parameter (described in Test Method E973), which is a quantitative measure of the error in the short-circuit current measurement. It is the intent of this test method to provide a recognized procedure for calibrating, characterizing, and reporting the calibration data for primary photovoltaic reference cells using a tabular reference spectrum.
5.2 The calibration of a reference cell is specific to a particular spectral irradiance distribution. It is the responsibility of the user to specify the applicable irradiance distribution, for example Tables G173. This test method allows calibration with respect to any tabular spectrum.
5.2.1 Tables G173 do not provide spectral irradiance data for wavelengths longer than 4 μm, yet pyrheliometers (see 6.1) typically have response in the 4–10 μm region. To mitigate this discrepancy, the Tables G173 spectra must be extended with the data provided in Annex A2.
5.3 A reference cell should be recalibrated at yearly intervals, or every six months if the cell is in continuous use outdoors.
5.4 Recommended physical characteristics of reference cells can be found in Specification E1040.
5.5 High-quality silicon primary reference cells are expected to be stable d...
SCOPE
1.1 This test method is intended for calibration and characterization of primary terrestrial photovoltaic reference cells to a desired reference spectral irradiance distribution, such as Tables G173. The recommended physical requirements for these reference cells are described in Specification E1040. Reference cells are principally used in the determination of the electrical performance of photovoltaic devices.
1.2 Primary photovoltaic reference cells are calibrated in natural sunlight using the relative quantum efficiency of the cell, the relative spectral distribution of the sunlight, and a tabulated reference spectral irradiance distribution. Selection of the reference spectral irradiance distribution is left to the user.
1.3 This test method requires the use of a pyrheliometer that is calibrated according to Test Method E816, which requires the use of a pyrheliometer that is traceable to the World Radiometric Reference (WRR). Therefore, reference cells calibrated according to this test method are traceable to the WRR.
1.4 This test method is used to calibrate primary reference cells; Test Method E1362 may be used to calibrate secondary and non-primary reference cells (these terms are defined in Terminology E772).
1.5 This test method applies only to the calibration of a photovoltaic cell that shows a linear dependence of its short-circuit current on irradiance over its intended range of use, as defined in Test Method E1143.
1.6 This test method applies only to the calibration of a reference cell fabricated with a single photovoltaic junction.
1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and...
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1125 − 16 (Reapproved 2020) An American National Standard
Standard Test Method for
Calibration of Primary Non-Concentrator Terrestrial
Photovoltaic Reference Cells Using a Tabular Spectrum
This standard is issued under the fixed designation E1125; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.8 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method is intended for calibration and charac-
responsibility of the user of this standard to establish appro-
terization of primary terrestrial photovoltaic reference cells to
priate safety, health, and environmental practices and deter-
a desired reference spectral irradiance distribution, such as
mine the applicability of regulatory limitations prior to use.
Tables G173. The recommended physical requirements for
1.9 This international standard was developed in accor-
these reference cells are described in Specification E1040.
dance with internationally recognized principles on standard-
Reference cells are principally used in the determination of the
ization established in the Decision on Principles for the
electrical performance of photovoltaic devices.
Development of International Standards, Guides and Recom-
1.2 Primary photovoltaic reference cells are calibrated in
mendations issued by the World Trade Organization Technical
natural sunlight using the relative quantum efficiency of the
Barriers to Trade (TBT) Committee.
cell, the relative spectral distribution of the sunlight, and a
tabulated reference spectral irradiance distribution. Selection
2. Referenced Documents
of the reference spectral irradiance distribution is left to the
user.
2.1 ASTM Standards:
E490Standard Solar Constant and Zero Air Mass Solar
1.3 Thistestmethodrequirestheuseofapyrheliometerthat
Spectral Irradiance Tables
is calibrated according to Test Method E816, which requires
E772Terminology of Solar Energy Conversion
the use of a pyrheliometer that is traceable to the World
E816Test Method for Calibration of Pyrheliometers by
Radiometric Reference (WRR). Therefore, reference cells
Comparison to Reference Pyrheliometers
calibrated according to this test method are traceable to the
E927Classification for Solar Simulators for Electrical Per-
WRR.
formance Testing of Photovoltaic Devices
1.4 This test method is used to calibrate primary reference
E948Test Method for Electrical Performance of Photovol-
cells; Test Method E1362 may be used to calibrate secondary
taic Cells Using Reference Cells Under Simulated Sun-
and non-primary reference cells (these terms are defined in
light
Terminology E772).
E973Test Method for Determination of the Spectral Mis-
1.5 This test method applies only to the calibration of a
match Parameter Between a Photovoltaic Device and a
photovoltaic cell that shows a linear dependence of its short-
Photovoltaic Reference Cell
circuit current on irradiance over its intended range of use, as
E1021TestMethodforSpectralResponsivityMeasurements
defined in Test Method E1143.
of Photovoltaic Devices
E1040Specification for Physical Characteristics of Noncon-
1.6 This test method applies only to the calibration of a
centrator Terrestrial Photovoltaic Reference Cells
reference cell fabricated with a single photovoltaic junction.
E1143Test Method for Determining the Linearity of a
1.7 The values stated in SI units are to be regarded as
Photovoltaic Device Parameter with Respect To a Test
standard. No other units of measurement are included in this
Parameter
standard.
E1362Test Methods for Calibration of Non-Concentrator
Photovoltaic Non-Primary Reference Cells
This test method is under the jurisdiction of ASTM Committee E44 on Solar,
GeothermalandOtherAlternativeEnergySourcesandisthedirectresponsibilityof
Subcommittee E44.09 on Photovoltaic Electric Power Conversion. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
CurrenteditionapprovedJune1,2020.PublishedJuly2020.Originallyapproved contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
in 1986. Last previous edition approved in 2016 as E1125–16. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
E1125-16R20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1125 − 16 (2020)
E2554Practice for Estimating and Monitoring the Uncer- 3.3.20 O (λ,T)—quantum efficiency, reference cell (%).
D
tainty of Test Results of a Test Method Using Control
3.3.21 r —collimator inner aperture radius (m).
x
Chart Techniques
3.3.22 R—collimator entrance aperture radius (m).
G138Test Method for Calibration of a Spectroradiometer
3.3.23 R —pyrheliometer to integrated spectral irradiance
Using a Standard Source of Irradiance
E
ratio (dimensionless).
G173TablesforReferenceSolarSpectralIrradiances:Direct
Normal and Hemispherical on 37° Tilted Surface
3.3.24 RNG—as a subscript, refers to the minimum-to-
G183Practice for Field Use of Pyranometers, Pyrheliom-
maximum range of an array of values.
eters and UV Radiometers
3.3.25 s—sample standard deviation, reference cell calibra-
2.2 WMO Document:
2 –1
tion value (Am W ).
WMO-No. 8 Guide to Meteorological Instruments and
3.3.26 T—temperature (°C).
Methods of Observation, Seventh ed., 2008.
3.3.27 T —calibration temperature, reference cell (25°C).
3. Terminology
3.3.28 Z (λ)—pyrheliometer spectral transmittance function
P
3.1 Definitions—Definitions of terms used in this test
(dimensionless).
method may be found in Terminology E772.
3.3.29 λ—wavelength (µm or nm).
3.2 The following symbols and units are used in this test
3.3.30 θ —collimator opening angle (°).
O
method:
3.3.31 θ —collimator slope angle (°).
S
3.3 Symbols:
3.3.32 Θ (λ)—partial derivative of quantum efficiency with
3.3.1 A —collimator aperture identifiers (non-numeric).
D
x
–1
2 –1 respect to temperature (%·°C ).
3.3.2 C—calibration value, reference cell (Am W ).
3.3.3 C—array of calibration values, reference cell
4. Summary of Test Method
2 –1
(Am W ).
4.1 The calibration of a primary photovoltaic reference cell
3.3.4 D—as a subscript, refers to the reference cell to be
consists of measuring the short-circuit current of the cell when
calibrated; as a variable, distance from collimator entrance
illuminated with natural sunlight, along with the direct solar
aperture to reference cell top surface, or to spectroradiometer
irradiance using a pyrheliometer (see Terminology E772). The
entrance optics (m).
ratio of the short-circuit current of the cell to the irradiance is
3.3.5 E—total irradiance, measured with pyrheliometer
called the responsivity, which, when divided by a spectral
–2
(Wm ).
correction factor similar to the spectral mismatch parameter
–2
3.3.6 E—array of measured total irradiance values (Wm ). defined in Test Method E973, is the calibration value for the
−2 −1 –2 –1
reference cell. The spectral correction factor also corrects the
3.3.7 E(λ)—spectral irradiance (Wm µm or Wm nm ).
calibration value to 25°C (see 4.2.2).
–2 –1
3.3.8 E (λ)—measured solar spectral irradiance (Wm µm
S
4.1.1 The relative spectral irradiance of the sunlight is
–2 –1
or WM nm ).
measured using a spectroradiometer as specified in Test
3.3.9 E (λ)—reference spectral irradiance distribution
Method G138 and Test Method E973.
–2 –1 –2 –1
(Wm µm or WM nm ).
4.1.2 A pyrheliometer measures direct solar irrradiance by
3.3.10 F—spectral correction factor (dimensionless).
restricting the field-of-view (FOV) to a narrow conical solid
angle,typically5°,thatincludesthe0.5°conesubtendedbythe
3.3.11 FOV—field-of-view (°).
sun. This calibration method requires that the same irradiance
3.3.12 I—short-circuit current, reference cell (A).
measured by the pyrheliometer also illuminate the primary
3.3.13 I—arrayofmeasuredshort-circuitcurrents,reference
reference cell to be calibrated and the spectroradiometer
cell (A).
simultaneously. Thus, both are required to have collimators
3.3.14 i—as a subscript, refers to the ith current and
(see 6.2).
irradiance data point (dimensionless).
4.1.3 Multiple calibration values determined from I, E, and
E(λ) measurements made on a minimum of three different
3.3.15 j—as a subscript, refers to the jth calibration value
days, are averaged to produce the final calibration result. Each
data point (dimensionless).
data point corresponds to a single E(λ) spectral irradiance.
3.3.16 L—collimator length (m).
4.2 The following is a list of measurements that are used to
3.3.17 n—number of current and irradiance data points
characterize reference cells and are reported with the calibra-
measured during calibration time period (dimensionless).
tion data:
3.3.18 m—number of calibration value data points (dimen-
4.2.1 The relative quantum efficiency of the cell is deter-
sionless).
mined in accordance with Test Methods E1021.
3.3.19 M—spectral mismatch parameter (dimensionless).
4.2.2 Temperature sensitivity of the cell’s short-circuit cur-
rent is determined experimentally by measuring the partial
derivative of quantum efficiency with respect to temperature,
Available fromWorld Meteorological Organization (WMO), 7bis, avenue de la
Paix,CasePostaleNo.2300,CH-1211Geneva2,Switzerland,http://www.wmo.int. as specified in Test Method E973.
E1125 − 16 (2020)
4.2.3 Linearity of short-circuit current versus irradiance is G183 provides guidance to the use of pyrheliometers for direct
determined in accordance with Test Method E1143. solar irradiance measurements.
4.2.4 Thefillfactorofthereferencecellisdeterminedusing
6.1.1 Because secondary reference pyrheliometers are cali-
TestMethodE948.Providingthefillfactorwiththecalibration
brated against an absolute cavity radiometer, the total uncer-
data allows the reference cell to be checked in the future for
tainty in the primary reference cell calibration value will be
electrical degradation or damage. reduced if an absolute cavity radiometer is used.
6.1.2 The spectral transmittance function of the pyrheliom-
5. Significance and Use
eter must be considered. For an absolute cavity radiometer
without a window, Z (λ) can be assumed to be one over a very
5.1 The electrical output of a photovoltaic device is depen- P
wide wavelength range. Secondary reference pyrheliometers
dent on the spectral content of the illumination source, its
typically have a window at the entrance aperture, so Z (λ) can
intensity, and the device temperature. To make standardized, P
be assumed to be the spectral transmittance of the window
accurate measurements of the performance of photovoltaic
material.
devices under a variety of light sources when the intensity is
6.1.2.1 Test Method E816 requires absolute cavity radiom-
measured with a calibrated reference cell, it is necessary to
eters to be “nonselective over the range from 0.3 to 10 µm”,
account for the error in the short-circuit current that occurs if
and secondary reference pyrheliometers to be “nonselective
the relative quantum efficiency of the reference cell is not
over the range from 0.3 to 4 µm.”
identicaltothequantumefficiencyofthedevicetobetested.A
similarerroroccursifthespectralirradiancedistributionofthe
6.1.2.2 Commercially available secondary pyrheliometers
testlightsourceisnotidenticaltothedesiredreferencespectral
use a variety of different window materials, and many do not
irradiance distribution. These errors are accounted for by the
meet the 0.3 to 4 µm requirement of Test Method E816. The
spectral mismatch parameter (described inTest Method E973),
transmittance of fused silica (SiO ), for example, has signifi-
which is a quantitative measure of the error in the short-circuit cantvariationsinthe2to4µmregionthatdependonthegrade
current measurement. It is the intent of this test method to
ofthematerial(ultravioletorinfraredgrade).Sapphire(Al O )
2 3
provide a recognized procedure for calibrating, characterizing, transmits beyond 4 µm, but its transmittance is not entirely flat
and reporting the calibration data for primary photovoltaic
over0.4to4µm.Crystallinequartz(SiO )isveryflatover0.25
reference cells using a tabular reference spectrum.
to 2.5 µm, but the transmittance falls to zero by 4 µm. The
pyrheliometer manufacturer should be consulted to obtain the
5.2 The calibration of a reference cell is specific to a
window transmittance data.
particular spectral irradiance distribution. It is the responsibil-
6.1.2.3 The calibration procedure in Test Method E816
ity of the user to specify the applicable irradiance distribution,
places restrictions on allowable atmospheric conditions and
for example Tables G173. This test method allows calibration
doesnotadjustcalibrationresultswithspectralinformation:all
with respect to any tabular spectrum.
pyrheliometers are calibrated with the same procedure regard-
5.2.1 Tables G173 do not provide spectral irradiance data
less of the window material.
for wavelengths longer than 4 µm, yet pyrheliometers (see 6.1)
typicallyhaveresponseinthe4–10µmregion.Tomitigatethis
6.2 Collimators—Tubes with internal baffles, intended for
discrepancy, the Tables G173 spectra must be extended with
pointing toward the sun, that restrict the FOV and are fitted to
the data provided in Annex A2.
the reference cell to be calibrated and the spectroradiometer
(see6.3);anacceptablecollimatordesignisprovidedinAnnex
5.3 A reference cell should be recalibrated at yearly
A1.The collimators must match the FOVof the pyrheliometer
intervals, or every six months if the cell is in continuous use
(see A1.4.1).
outdoors.
6.2.1 Eliminate or minimize any stray light entering the
5.4 Recommended physical characteristics of reference
collimators at the bottoms of the tubes.
cells can be found in Specification E1040.
6.2.2 The receiving aperture of the reference cell collimator
5.5 High-quality silicon primary reference cells are ex-
shallbesizedsuchthattheentireopticalsurfaceoftheprimary
pected to be stable devices by nature, and as such can be
reference cell to be calibrated is completely illuminated,
considered control samples. Thus, the calibration value data
including the window (see Specification E1040). Thus, for a
points(see9.3)canbemonitoredwithcontrolcharttechniques
reference cell with a 50 mm square window, the collimator
according to Practi
...
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