ASTM E1021-95(2001)

Standard Test Methods for Measuring Spectral Response of Photovoltaic Cells

SCOPE
1.1 These test methods cover the determination of either the absolute or relative spectral response of a single, linear photovoltaic cell. These test methods require the use of a bias light.  
1.2 These test methods are not intended for use with interconnected photovoltaic devices.  
1.3 There is no similar or equivalent ISO standard.  
1.4  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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-Oct-1995
• ICS: 77.040.10 - Mechanical testing of metals
• Technical Committee: E44 - Solar, Geothermal and Other Alternative Energy Sources
• Drafting Committee: E44.09 - Photovoltaic Electric Power Conversion

Relations

• Replaces: ASTM E1021-95 - Standard Test Methods for Measuring Spectral Response of Photovoltaic Cells
• Effective Date: 10-Oct-1995
• Replaced By: ASTM E1021-06 - Standard Test Method for Spectral Responsivity Measurements of Photovoltaic Devices
• Effective Date: 01-Nov-2006
• Referred By: ASTM E1125-16(2020) - Standard Test Method for Calibration of Primary Non-Concentrator Terrestrial Photovoltaic Reference Cells Using a Tabular Spectrum
• Effective Date: 10-Oct-1995
• Referred By: ASTM E1036-15(2019) - Standard Test Methods for Electrical Performance of Nonconcentrator Terrestrial Photovoltaic Modules and Arrays Using Reference Cells
• Effective Date: 10-Oct-1995
• Referred By: ASTM E772-15(2021) - Standard Terminology of Solar Energy Conversion
• Effective Date: 10-Oct-1995
• Referred By: ASTM E1362-15(2019) - Standard Test Methods for Calibration of Non-Concentrator Photovoltaic Non-Primary Reference Cells
• Effective Date: 10-Oct-1995
• Referred By: ASTM E973-16(2020) - Standard Test Method for Determination of the Spectral Mismatch Parameter Between a Photovoltaic Device and a Photovoltaic Reference Cell
• Effective Date: 10-Oct-1995
• Referred By: ASTM E2236-10(2019) - Standard Test Methods for Measurement of Electrical Performance and Spectral Response of Nonconcentrator Multijunction Photovoltaic Cells and Modules
• Effective Date: 10-Oct-1995

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E1021–95 (Reapproved 2001)
Standard Test Methods for
Measuring Spectral Response of Photovoltaic Cells
This standard is issued under the fixed designation E1021; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope a—illuminated cell area, m ,
A—irradiance normalization constant,
1.1 Thesetestmethodscoverthedeterminationofeitherthe
−1
c—speed of light in vacuum, ms ,
absolute or relative spectral response of a single, linear
−2
E—monochromatic source irradiance, Wm ,
photovoltaic cell. These test methods require the use of a bias
−2
E — reference spectral irradiance, Wm ,
o
light.
−1
h—Planck’s constant, JHz ,
1.2 These test methods are not intended for use with
I—current, A,
interconnected photovoltaic devices.
I —solar cell short-circuit current, A,
1.3 There is no similar or equivalent ISO standard. sc
K—relative-to-absolute spectral response conversion con-
1.4 This standard does not purport to address all of the
stant,
safety concerns, if any, associated with its use. It is the
M—spectral mismatch parameter,
responsibility of the user of this standard to establish appro-
q—elementary charge, C,
priate safety and health practices and determine the applica-
Q—external quantum efficiency,
bility of regulatory limitations prior to use.
−1
R —absolute spectral response, AW ,
a
2. Referenced Documents
R —relative spectral response, and
r
l—wavelength, nm or µm.
2.1 ASTM Standards:
3.2.2 Symbolic quantities that are functions of wavelength
E691 Practice for Conducting an Interlaboratory Study to
appear as X (l).
Determine the Precision of a Test Method
E772 Terminology Relating to Solar Energy Conversion
4. Summary of Test Methods
E892 Tables for Terrestrial Solar Spectral Irradiance atAir
4.1 The spectral response of the photovoltaic cell is deter-
Mass 1.5 for a 37° Tilted Surface
mined by the following procedure:
E927 Specification for Solar Simulation for Terrestrial
4.1.1 A monochromatic, chopped beam of light is directed
Photovoltaic Testing
atnormalincidenceontothecell.Simultaneously,acontinuous
E973 Test Method for Determination of the Spectral Mis-
white light beam (bias light) is used to illuminate the entire
match Parameter Between a Photovoltaic Device and a
3 device at an irradiance approximately equal to normal end use
Photovoltaic Reference Cell
operating conditions intended for the cell.
E1328 Terminology Relating to Photovoltaic Solar Energy
3 4.1.2 The spectral dependence of the ac (chopped) compo-
Conversion
nentoftheshort-circuitcurrentismonitoredasthewavelength
3. Terminology oftheincidentlightisvariedovertheresponsebandofthecell.
The total energy in the beam of chopped light as a function of
3.1 Definitions—Definitions of terms used in these test
wavelength is determined with an appropriate detector.
methods may be found in Terminology E772 and in Termi-
4.2 The absolute spectral response of a cell requires the
nology E1328.
knowledge of the absolute energy in the chopped beam. The
3.2 Symbols:
detector must, therefore, be traceable to a National Institute of
3.2.1 Thefollowingsymbolsandunitsareusedinthesetest
Standards and Technology (NIST) Detector Response Pack-
methods.
age, orotherstandardsforblackbodydetectorsasappropriate.
These test methods are under the jurisdiction of ASTM Committee E44 on
Solar, Geothermal, and Other Alternative Energy Sources and are the direct
responsibility of Subcommittee E44.09 on Photovoltaic Electric Power Conversion.
Current edition approved Oct. 10, 1995. Published January 1996. Zalewski, E. F., et al., 88The NBS Detector Response Transfer and Intercom-
Annual Book of ASTM Standards, Vol 14.02. parison Package: Its Characteristics and Use,” National Bureau of Standards,
Annual Book of ASTM Standards, Vol 12.02. Radiometric Physics Division, Washington, D.C., 1980.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1021
Theabsolutespectralresponseofthecellcanthenbecomputed 6.3 Monochromatic Light Chopper:
using the measured cell response and the irradiance of the
6.3.1 A rotating mechanical light chopper or other device
chopped source.
used to modulate the monochromatic light source.
6.3.2 The chopper blades should be non-reflective or black
5. Significance and Use
to minimize modulation of stray light.
5.1 The spectral response of a photovoltaic cell is required
6.4 Bias Light Source:
to interpret laboratory measurements on devices and is useful
6.4.1 In order to measure the spectral response under
for theoretical calculations. The reference cell method of
conditions approximating those obtained under standard oper-
photovoltaic device performance measurement, for example,
ating conditions, a bias light shall be used.The light should be
requires spectral response measurements for computing the
ofsufficientintensitytoensurethecelltobetestedisoperating
spectral mismatch parameter (see Test Method E973).
in its linear response region, preferably within 30% of its
5.2 The methods described herein are appropriate for use in
normaloperatingshort-circuitcurrent,whenboththebiaslight
either research and development applications or in product
and the monochromatic source are on.
quality control by manufacturers.
6.4.2 The spectral distribution of the bias light should meet
6. Apparatus
the criteria for a Class C simulator as given in Table 2 of
6.1 Spectral Detector: Specification E927. Generally, a spatial uniformity of 610%
is adequate.
6.1.1 The following detectors are acceptable for use in the
calibration of the monochromatic light source:
6.4.3 Thebiassourceshouldcontainnosignificantharmon-
6.1.1.1 Pyroelectric radiometer, and
ics of the chopper frequency used with the monochromatic
6.1.1.2 Calibrated photodetector.
source.Thiscanbedonemosteasilybyusingawellregulated,
6.2 Monochromatic Light Source:
dc power supply for the bias light. Care should be taken to
6.2.1 A variety of different laboratory apparatus are avail-
prevent reflections of the bias light from the chopper blade
able for the generation of a monochromatic beam of light.
from striking the sample. Mechanical vibrations, either from
Prism or grating monochromators using tungsten or other light
the chopper or other sources, shall not be allowed to modulate
sources are most commonly used. Discrete and tunable
the bias light.
continuous-wavelasersofferanothersourceofmonochromatic
6.5 Synchronous Detection Instrumentation:
light. The wide range of wavelengths available coupled with
6.5.1 A pre-amplifier followed by a lock-in amplifier, ac
the high optical quality of laser beams renders them attractive.
voltmeter, or true-root-mean-square (RMS) voltmeter is used
Another source is narrow-bandpass optical filters in conjunc-
to detect the low-level, chopped signals from the photovoltaic
tion with a broad spectrum light source such as tungsten.
device and thus measure the cell short-circuit current. Choice
6.2.2 The monochromatic light source shall be capable of
of pre-amplifier shall include consideration of the requirement
providing wavelengths that extend beyond the response region
that the photovoltaic cell must be operated in the short-circuit
of the device to be tested.
current mode and that both a low-level ac, as well as a
6.2.3 A minimum of 12 wavelengths within the spectral
high-level dc signal will be present. Under these conditions a
response range of the cell to be measured is required.
pre-amplifier with a transformer coupled input circuit may
6.2.4 Spectralbandwidthofthemonochromaticlightsource
saturateandresultininaccuratereadings.Ifthepre-amplifieris
shall not exceed 50 nm for a relative spectral response
not a low input-impedance, short-circuit current type and the
measurement and 20 nm for an absolute spectral response
photovoltaic device is loaded in the short-circuit mode with a
measurement.
four-terminal resistor instead, one must ensure that the drop
6.2.5 Thelightsourceshallbecapableofprovidingaspatial
across the load resistor is less than 20 mV. The dynamic range
uniformity of 62.5% over the area of the test plane, and a
required of the instrument will depend on the chopped beam
temporal stability of 61% during the measurement period.
source used. For example, a tungsten source with a monochro-
6.2.6 Care must be taken to ensure that scattered light or
matorwillusuallyrequireadynamicrangeoffourtosixorders
higher order light effects are negligible. The chopper (see 6.5)
of magnitude, because of the wide range of intensity variation
entranceandexitopticsshouldbeenclosedinablackcavityto
over the required spectral test range.
minimize the modulation of stray light by the chopper blades.
6.5.2 For relative spectral response measurements, it is not
6.2.7 It is recommended that the monochromatic light
necessary for the synchronous detection instrumentation to
source be able to illuminate the entire area of the cell to be
outputtheshort-circuitcurrentinamperes.Alock-inamplifier,
tested. If not, multiple measurements of the spectral response
for example, might give the short-circuit current in microvolts
in different areas of the cell are required (see 8.2.5.1).
which does not then need to be converted to the actual current
6.2.8 If a pyroelectric detector is used (see 6.1.1), the
in amperes.
monochromatic source must illuminate the entire detector. If a
6.5.3 True-RMS voltmeters respond to both the ac and the
calibrated photodetector is used, it is not necessary to illumi-
dc components of the short-circuit current which then must be
nate the entire detector if detector response uniformity and
separated to determine the ac component. An acceptable
linearity has been proven.
method uses the square root of the difference of the square of
6.2.9 An optical shutter may be used to interrupt the
the signal and the background (or noise) signal.
monochromatic beam and, therefore, eliminate time delays
involved with source and supply warm-up times. 6.6 Test Plane:
E1021
6.6.1 The test plane shall consist of means to mount the 8.2 Method A:
photovoltaiccelltobetestedinapositiontoallowillumination 8.2.1 Mount the spectral detector in the test plane and
by both the monochromatic and bias light sources. illuminate the entire area of the detector with the dc bias light.
6.6.2 The test plane also shall allow the spectral detector 8.2.2 Measure the noise level at the output of the detector
(see 6.4) to be illuminated by both the monochromatic and the while the monochromatic light source is turned off. The noise
bias light sources in the same plane as the photovoltaic cell. level must be less than 1% of the smallest signal value
6.6.3 The
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