ASTM E2236-10(2015)
(Test Method)Standard Test Methods for Measurement of Electrical Performance and Spectral Response of Nonconcentrator Multijunction Photovoltaic Cells and Modules
Standard Test Methods for Measurement of Electrical Performance and Spectral Response of Nonconcentrator Multijunction Photovoltaic Cells and Modules
SIGNIFICANCE AND USE
4.1 In a series-connected multijunction PV device, the incident total and spectral irradiance determines which component cell will generate the smallest photocurrent and thus limit the current through the entire series-connected device. This current-limiting behavior also affects the fill factor of the device. Because of this, special techniques are needed to measure the correct I-V characteristics of multijunction devices under the desired reporting conditions (see Test Methods E1036).
4.2 These test methods use a numerical parameter called the current balance which is a measure of how well the test conditions replicate the desired reporting conditions. When the current balance deviates from unity by more than 0.03, the uncertainty of the measurement may be increased.
4.3 The effects of current limiting in individual component cells can cause problems for I-V curve translations to different temperature and irradiance conditions, such as the translations recommended in Test Methods E1036. For example, if a different component cell becomes the limiting cell as the irradiance is varied, a discontinuity in the current versus irradiance characteristic may be observed. For this reason, it is recommended that I-V characteristics of multijunction devices be measured at temperature and irradiance conditions close to the desired reporting conditions.
4.4 Some multijunction devices have more than two terminals which allow electrical connections to each component cell. In these cases, the special techniques for spectral response measurements are not needed because the component cells can be measured individually. However, these I-V techniques are still needed if the device is intended to be operated as a two-terminal device.
4.5 Using these test methods, the spectral response is typically measured while the individual component cell under test is illuminated at levels that are less than Eo. Nonlinearity of the spectral response may cause the measured results to dif...
SCOPE
1.1 These test methods provide special techniques needed to determine the electrical performance and spectral response of two-terminal, multijunction photovoltaic (PV) devices, both cell and modules.
1.2 These test methods are modifications and extensions of the procedures for single-junction devices defined by Test Methods E948, E1021, and E1036.
1.3 These test methods do not include temperature and irradiance corrections for spectral response and current-voltage (I-V) measurements. Procedures for such corrections are available in Test Methods E948, E1021, and E1036.
1.4 These test methods may be applied to cells and modules intended for concentrator applications.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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.
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Designation: E2236 − 10 (Reapproved 2015) An American National Standard
Standard Test Methods for
Measurement of Electrical Performance and Spectral
Response of Nonconcentrator Multijunction Photovoltaic
Cells and Modules
This standard is issued under the fixed designation E2236; 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 2. Referenced Documents
1.1 Thesetestmethodsprovidespecialtechniquesneededto 2.1 ASTM Standards:
determine the electrical performance and spectral response of E772Terminology of Solar Energy Conversion
two-terminal, multijunction photovoltaic (PV) devices, both E927Specification for Solar Simulation for Photovoltaic
cell and modules. Testing
E948Test Method for Electrical Performance of Photovol-
1.2 These test methods are modifications and extensions of
taic Cells Using Reference Cells Under Simulated Sun-
the procedures for single-junction devices defined by Test
light
Methods E948, E1021, and E1036.
E973Test Method for Determination of the Spectral Mis-
1.3 These test methods do not include temperature and
match Parameter Between a Photovoltaic Device and a
irradiancecorrectionsforspectralresponseandcurrent-voltage
Photovoltaic Reference Cell
(I-V)measurements.Proceduresforsuchcorrectionsareavail-
E1021TestMethodforSpectralResponsivityMeasurements
able in Test Methods E948, E1021, and E1036.
of Photovoltaic Devices
E1036Test Methods for Electrical Performance of Noncon-
1.4 Thesetestmethodsmaybeappliedtocellsandmodules
intended for concentrator applications. centrator Terrestrial Photovoltaic Modules and Arrays
Using Reference Cells
1.5 The values stated in SI units are to be regarded as
E1040Specification for Physical Characteristics of Noncon-
standard. No other units of measurement are included in this
centrator Terrestrial Photovoltaic Reference Cells
standard.
E1125 Test Method for Calibration of Primary Non-
1.6 This standard does not purport to address all of the
Concentrator Terrestrial Photovoltaic Reference Cells Us-
safety concerns, if any, associated with its use. It is the
ing a Tabular Spectrum
responsibility of the user of this standard to establish appro-
E1328Terminology Relating to Photovoltaic Solar Energy
priate safety, health, and environmental practices and deter- 3
Conversion (Withdrawn 2012)
mine the applicability of regulatory limitations prior to use.
E1362Test Methods for Calibration of Non-Concentrator
1.7 This international standard was developed in accor-
Photovoltaic Non-Primary Reference Cells
dance with internationally recognized principles on standard-
G138Test Method for Calibration of a Spectroradiometer
ization established in the Decision on Principles for the
Using a Standard Source of Irradiance
Development of International Standards, Guides and Recom-
G173TablesforReferenceSolarSpectralIrradiances:Direct
mendations issued by the World Trade Organization Technical
Normal and Hemispherical on 37° Tilted Surface
Barriers to Trade (TBT) Committee.
1 2
These test methods are under the jurisdiction of ASTM Committee E44 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Solar, Geothermal and Other Alternative Energy Sources and is the direct respon- contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
sibility of SubcommitteeE44.09 on Photovoltaic Electric Power Conversion. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved March 1, 2015. Published April 2015. Originally the ASTM website.
approved in 2002. Last previous edition approved in 2010 as E2236–10. DOI: The last approved version of this historical standard is referenced on
10.1520/E2236-10R15. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2236 − 10 (2015)
3. Terminology temperature and irradiance conditions, such as the translations
recommended in Test Methods E1036. For example, if a
3.1 Definitions—definitions of terms used in this standard
different component cell becomes the limiting cell as the
may be found in Terminology E772 and in Terminology
irradiance is varied, a discontinuity in the current versus
E1328.
irradiance characteristic may be observed. For this reason, it is
3.2 Definitions of Terms Specific to This Standard:
recommended that I-V characteristics of multijunction devices
3.2.1 multijunction device, n—a photovoltaic device com-
be measured at temperature and irradiance conditions close to
posedofmorethanonephotovoltaicjunctionstackedontopof
the desired reporting conditions.
each other and electrically connected in series.
4.4 Some multijunction devices have more than two termi-
3.2.2 component cells, n—the individual photovoltaic junc-
nals which allow electrical connections to each component
tions of a multijunction device.
cell.Inthesecases,thespecialtechniquesforspectralresponse
3.3 Symbols:
measurements are not needed because the component cells can
be measured individually. However, these I-V techniques are
C = reference cell calibration constant under the refer-
still needed if the device is intended to be operated as a
2 −1
ence spectrum, A·m ·W
two-terminal device.
−2
E = total irradiance of reporting conditions, W·m
o
−2 −1
4.5 Using these test methods, the spectral response is
E (λ) = source spectral irradiance, W·m ·nm or
S
−2 −1
typically measured while the individual component cell under
W·m ·µm
−2 −1
E (λ) = reference spectral irradiance, W·m ·nm or test is illuminated at levels that are less than E . Nonlinearity
R
o
−2 −1
W·m ·µm of the spectral response may cause the measured results to
FF = fill factor, dimensionless
differ from the spectral response at the illumination levels of
i = subscript index associated with an individual com-
actual use conditions.
ponent cell
I = current of test device under the reference spectrum,
5. Summary of Test Methods
o
A
5.1 Spectralresponsemeasurementsofthedeviceundertest
I = current of test device under the source spectrum,A
are accomplished using light- and voltage-biasing techniques
I = short-circuit current, A
sc
of each component cell, followed by determination of the
I = short-circuit current of reference cell under the
R
spectral response according to Test Methods E1021.
source spectrum, A
M = spectral mismatch parameter, dimensionless
5.2 Ifaspectrallyadjustablesolarsimulatorisavailable(see
n = number of component cells in the multijunction
6.1.1)theelectricalperformancemeasurementsuseaniterative
device
process of adjusting the incident spectral irradiance until the
P = maximum power, W
max operating conditions are close to the desired reporting condi-
Q(λ) = quantum efficiency, dimensionless
tionsisused.Thisadjustmentmodifiesaquantityknownasthe
−1
R(λ) = spectral response, A·W
current balance. The I-V characteristics are then measured
−1
R (λ) = test device spectral response, A·W
T
according to Test Methods E948 or E1036. Appendix X1
−1
R (λ) = reference cell spectral response, A·W
R
contains a derivation and discussion of current balance.
T = temperature, °C
5.3 For the case of light sources where the spectral irradi-
V = open-circuit voltage, V
oc
V = voltage applied by dc bias source, V ance cannot be changed, such as outdoors or if a spectrally
b
Z = current balance, dimensionless adjustable solar simulator is not available, the I-V characteris-
λ = wavelength, nm or µm
tics are measured according to Test Methods E948 or E1036.
However,thecurrentbalanceineachcomponentcellmustalso
4. Significance and Use
be determined and reported.
4.1 In a series-connected multijunction PV device, the
incident total and spectral irradiance determines which com-
6. Apparatus
ponent cell will generate the smallest photocurrent and thus
6.1 In addition to the apparatus required for Test Methods
limit the current through the entire series-connected device.
E948,E973,E1021,E1036,andG138,thesetestmethodsrefer
This current-limiting behavior also affects the fill factor of the
to the following apparatus.
device. Because of this, special techniques are needed to
6.1.1 spectrally adjustable Solar Simulator—A solar simu-
measurethecorrectI-Vcharacteristicsofmultijunctiondevices
lator that meets the requirements of Specification E927 and
under the desired reporting conditions (see Test Methods
which has the additional capability of allowing different
E1036).
wavelength regions of its spectral irradiance to be indepen-
4.2 Thesetestmethodsuseanumericalparametercalledthe
dently adjusted. This may be accomplished by several
current balance which is a measure of how well the test
methods, such as a multisource simulator with independent
conditions replicate the desired reporting conditions.When the
sources for different regions, or a multiple filter simulator.
current balance deviates from unity by more than 0.03, the
6.1.1.1 Ideally, the adjustable wavelength ranges of the
uncertainty of the measurement may be increased.
spectrally adjustable solar simulator should correspond to the
4.3 The effects of current limiting in individual component spectral response ranges of each component cell in the multi-
cells can cause problems for I-V curve translations to different junction device to be tested.
E2236 − 10 (2015)
6.1.2 Reference Cells—Photovoltaic reference cells (see 7.1.7 Connect the test device to the ac measurement instru-
Specification E1040), calibrated according to Test Methods mentation.
E1125 or E1362, are used to measure source irradiance in the
7.1.8 Maximizetheacsignalfromthecomponentcellunder
wavelength regions that correspond to each component cell in test using a wavelength at which it is expected to respond:
the multijunction device to be tested. For best results, the
7.1.8.1 Set the monochromatic light source to a wavelength
spectralresponsesofthereferencecellsshouldbesimilartothe
in the expected spectral response region of the component cell
spectral responses of the corresponding component cells.
to be measured.
6.1.3 Bias Light Source—AdcbiaslightasspecifiedbyTest
7.1.8.2 Adjust the bias light intensity to saturate or maxi-
Methods E1021, that is equipped with appropriate spectral mize the test device signal.
filters to block wavelength regions corresponding to the
7.1.9 Minimize the test device signal at wavelengths where
expected spectral response range of the individual component
the component cells not being measured are expected to
cell being tested.
respond:
6.1.3.1 Acceptable alternatives to filtered light sources are
7.1.9.1 Setthemonochromaticlightsourceforawavelength
continuouslasersthatemitatsinglewavelengthsinthespectral
in the expected spectral response region of the component cell
response ranges of each component cell. Ideally, the selected
not being measured.
laser wavelengths should not illuminate regions where the
7.1.9.2 Minimize or zero the test device signal by adjusting
spectral responses of any two component cells overlap.
the bias light intensity.
6.1.4 Bias Voltage Source—A variable dc power supply
7.1.9.3 Repeat 7.1.9.1 and 7.1.9.2 for additional component
capableofprovidingavoltageequaltotheopen-circuitvoltage
cells not being measured, if any.
of the multijunction device to be tested, and compatible with
7.1.10 As in 7.1.8 and 7.1.9, adjust V to further maximize
b
the synchronous detection instrumentation of Test Methods
the signal in 7.1.8 and further minimize the signal in 7.1.9.
E1021.
7.1.11 Select light bias and voltage bias levels that both
maximize the signal in 7.1.8 and minimize the signal in 7.1.9.
7. Procedure
The signal in 7.1.9 should correspond to a quantum efficiency,
Q(λ), that is less than 0.01 in wavelength regions where the
7.1 Spectral Response:
component cell being measured is known to have no response.
7.1.1 Placethedeviceundertestinthespectralresponsetest
7.1.12 It may be necessary to adjust the bias light source in
fixture.
7.1.3 to obtain a light bias condition that satisfies 7.1.11.
7.1.2 Select the component cell to be measured.
7.1.13 Measure the relative spectral response of the compo-
7.1.3 Apply light bias to component cells not being mea-
nent cell being tested according to Test Methods E1021.
sured using the bias light source:
7.1.14 Repeat 7.1.2 – 7.1.13 for each component cell of the
7.1.3.1 Choose spectral filters whose spectral transmittance,
multijunction device under test.
when combined, corresponds to the spectral response of the
componentcellorcellsnotbeingmeasured.Installthespectral
7.2 Electrical Performance, spectrally adjustable Solar
filters in front of the bias light source.
Simulator:
7.1.3.2 If lasers are used, turn on the lasers that emit
7.2.1 Adjust the total irradiance of the spectrally adjustable
wavelengths corresponding to the component cell or cells not
solar simulator to a level close to the desired reporting
being measured.
conditions using a reference cell or previous experience (this
7.1.3.3 Ideally,theilluminationonthecomponentcellbeing initial irradiance level is not critical).
measured should be at E and the component cells not being
7.2.2 Measure the spectral irradiance of the spectrally ad-
o
measured should be illuminated at higher levels. Practically,
justable solar simulator with a spectroradiometer calibrated
the component cell to be measured should have some
according to Test Method G138.
illumination,asdevicespectralresponsivitiescanbeafunction
7.2.3 Calculate the spectral mismatch parameter, M, for
i
of the illumination level.
each component cell in the multijunction device under test
7.1.3.4 Turn on the bias light source and illuminate, as a
using the spectral responses obtained in 7.1, the reference cell
minimum, the region where the monochromatic beam illumi-
spectral responses, the spectral irradiance measured in 7.2.2,
nates the test device.
and the desired reference spectral irradiance (such as Tables
7.1.4 Measure the V of the test device.
G173).
oc
7.1.5 Calculate the bias voltage to use during the test: 7.2.4 Measure the I of each reference cell under the
sc
7.1.5.1 For devices with component cells that contribute spectrally adjustable solar simulator, I , in the same test plane
Ri
similar voltages, calculate the bias voltage according to Eq 1. as the multijunction device under test.
7.2.5 Calculate the current balance, Z, for each component
i
n 2 1
V 5 V . (1)
b oc cell in the multijunction device under test using the following
n
equation:
7.1.5.2 For devices with component cells contributing sub-
1 E C
O i
stantia
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E2236 − 10 E2236 − 10 (Reapproved 2015)
Standard Test Methods for
Measurement of Electrical Performance and Spectral
Response of Nonconcentrator Multijunction Photovoltaic
Cells and Modules
This standard is issued under the fixed designation E2236; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 These test methods provide special techniques needed to determine the electrical performance and spectral response of
two-terminal, multijunction photovoltaic (PV) devices, both cell and modules.
1.2 These test methods are modifications and extensions of the procedures for single-junction devices defined by Test Methods
E948, E1021, and E1036.
1.3 These test methods do not include temperature and irradiance corrections for spectral response and current-voltage (I-V)
measurements. Procedures for such corrections are available in Test Methods E948, E1021, and E1036.
1.4 These test methods may be applied to cells and modules intended for concentrator applications.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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.
2. Referenced Documents
2.1 ASTM Standards:
E772 Terminology of Solar Energy Conversion
E927 Specification for Solar Simulation for Photovoltaic Testing
E948 Test Method for Electrical Performance of Photovoltaic Cells Using Reference Cells Under Simulated Sunlight
E973 Test Method for Determination of the Spectral Mismatch Parameter Between a Photovoltaic Device and a Photovoltaic
Reference Cell
E1021 Test Method for Spectral Responsivity Measurements of Photovoltaic Devices
E1036 Test Methods for Electrical Performance of Nonconcentrator Terrestrial Photovoltaic Modules and Arrays Using
Reference Cells
E1040 Specification for Physical Characteristics of Nonconcentrator Terrestrial Photovoltaic Reference Cells
E1125 Test Method for Calibration of Primary Non-Concentrator Terrestrial Photovoltaic Reference Cells Using a Tabular
Spectrum
E1328 Terminology Relating to Photovoltaic Solar Energy Conversion (Withdrawn 2012)
E1362 Test Method for Calibration of Non-Concentrator Photovoltaic Secondary Reference Cells
G138 Test Method for Calibration of a Spectroradiometer Using a Standard Source of Irradiance
G173 Tables for Reference Solar Spectral Irradiances: Direct Normal and Hemispherical on 37° Tilted Surface
3. Terminology
3.1 Definitions—definitions of terms used in this standard may be found in Terminology E772 and in Terminology E1328.
3.2 Definitions of Terms Specific to This Standard:
These test methods are under the jurisdiction of ASTM Committee E44 on Solar, Geothermal and Other Alternative Energy Sources and is the direct responsibility of
SubcommitteeE44.09 on Photovoltaic Electric Power Conversion.
Current edition approved June 1, 2010March 1, 2015. Published July 2010April 2015. Originally approved in 2002. Last previous edition approved in 20052010 as
E2236–05a.–10. DOI: 10.1520/E2236-10.10.1520/E2236-10R15.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2236 − 10 (2015)
3.2.1 multijunction device, n—a photovoltaic device composed of more than one photovoltaic junction stacked on top of each
other and electrically connected in series.
3.2.2 component cells, n—the individual photovoltaic junctions of a multijunction device.
3.3 Symbols:
2 −1
C = reference cell calibration constant under the reference spectrum, A·m ·W
−2
E = total irradiance of reporting conditions, W·m
o
−2 −1 −2 −1
E (λ) = source spectral irradiance, W·m ·nm or W·m ·μm
S
−2 −1 −2 −1
E (λ) = reference spectral irradiance, W·m ·nm or W·m ·μm
R
FF = fill factor, dimensionless
i = subscript index associated with an individual component cell
I = current of test device under the reference spectrum, A
o
I = current of test device under the source spectrum, A
I = short-circuit current, A
sc
I = short-circuit current of reference cell under the source spectrum, A
R
M = spectral mismatch parameter, dimensionless
n = number of component cells in the multijunction device
P = maximum power, W
max
Q(λ) = quantum efficiency, dimensionless
−1
R(λ) = spectral response, A·W
−1
R (λ) = test device spectral response, A·W
T
−1
R (λ) = reference cell spectral response, A·W
R
T = temperature, °C
V = open-circuit voltage, V
oc
V = voltage applied by dc bias source, V
b
Z = current balance, dimensionless
λ = wavelength, nm or μm
4. Significance and Use
4.1 In a series-connected multijunction PV device, the incident total and spectral irradiance determines which component cell
will generate the smallest photocurrent and thus limit the current through the entire series-connected device. This current-limiting
behavior also affects the fill factor of the device. Because of this, special techniques are needed to measure the correct I-V
characteristics of multijunction devices under the desired reporting conditions (see Test Methods E1036).
4.2 These test methods use a numerical parameter called the current balance which is a measure of how well the test conditions
replicate the desired reporting conditions. When the current balance deviates from unity by more than 0.03, the uncertainty of the
measurement may be increased.
4.3 The effects of current limiting in individual component cells can cause problems for I-V curve translations to different
temperature and irradiance conditions, such as the translations recommended in Test Methods E1036. For example, if a different
component cell becomes the limiting cell as the irradiance is varied, a discontinuity in the current versus irradiance characteristic
may be observed. For this reason, it is recommended that I-V characteristics of multijunction devices be measured at temperature
and irradiance conditions close to the desired reporting conditions.
4.4 Some multijunction devices have more than two terminals which allow electrical connections to each component cell. In
these cases, the special techniques for spectral response measurements are not needed because the component cells can be
measured individually. However, these I-V techniques are still needed if the device is intended to be operated as a two-terminal
device.
4.5 Using these test methods, the spectral response is typically measured while the individual component cell under test is
illuminated at levels that are less than E . Nonlinearity of the spectral response may cause the measured results to differ from the
o
spectral response at the illumination levels of actual use conditions.
5. Summary of Test Methods
5.1 Spectral response measurements of the device under test are accomplished using light- and voltage-biasing techniques of
each component cell, followed by determination of the spectral response according to Test Methods E1021.
5.2 If a spectrally adjustable solar simulator is available (see 6.1.1) the electrical performance measurements use an iterative
process of adjusting the incident spectral irradiance until the operating conditions are close to the desired reporting conditions is
used. This adjustment modifies a quantity known as the current balance. The I-V characteristics are then measured according to
Test Methods E948 or E1036. Appendix X1 contains a derivation and discussion of current balance.
E2236 − 10 (2015)
5.3 For the case of light sources where the spectral irradiance cannot be changed, such as outdoors or if a spectrally adjustable
solar simulator is not available, the I-V characteristics are measured according to Test Methods E948 or E1036. However, the
current balance in each component cell must also be determined and reported.
6. Apparatus
6.1 In addition to the apparatus required for Test Methods E948, E973, E1021, E1036, and G138, these test methods refer to
the following apparatus.
6.1.1 spectrally adjustable Solar Simulator—A solar simulator that meets the requirements of Specification E927 and which has
the additional capability of allowing different wavelength regions of its spectral irradiance to be independently adjusted. This may
be accomplished by several methods, such as a multisource simulator with independent sources for different regions, or a multiple
filter simulator.
6.1.1.1 Ideally, the adjustable wavelength ranges of the spectrally adjustable solar simulator should correspond to the spectral
response ranges of each component cell in the multijunction device to be tested.
6.1.2 Reference Cells—Photovoltaic reference cells (see Specification E1040), calibrated according to Test Methods E1125 or
E1362, are used to measure source irradiance in the wavelength regions that correspond to each component cell in the multijunction
device to be tested. For best results, the spectral responses of the reference cells should be similar to the spectral responses of the
corresponding component cells.
6.1.3 Bias Light Source—A dc bias light as specified by Test Methods E1021, that is equipped with appropriate spectral filters
to block wavelength regions corresponding to the expected spectral response range of the individual component cell being tested.
6.1.3.1 Acceptable alternatives to filtered light sources are continuous lasers that emit at single wavelengths in the spectral
response ranges of each component cell. Ideally, the selected laser wavelengths should not illuminate regions where the spectral
responses of any two component cells overlap.
6.1.4 Bias Voltage Source—A variable dc power supply capable of providing a voltage equal to the open-circuit voltage of the
multijunction device to be tested, and compatible with the synchronous detection instrumentation of Test Methods E1021.
7. Procedure
7.1 Spectral Response:
7.1.1 Place the device under test in the spectral response test fixture.
7.1.2 Select the component cell to be measured.
7.1.3 Apply light bias to component cells not being measured using the bias light source:
7.1.3.1 Choose spectral filters whose spectral transmittance, when combined, corresponds to the spectral response of the
component cell or cells not being measured. Install the spectral filters in front of the bias light source.
7.1.3.2 If lasers are used, turn on the lasers that emit wavelengths corresponding to the component cell or cells not being
measured.
7.1.3.3 Ideally, the illumination on the component cell being measured should be at E and the component cells not being
o
measured should be illuminated at higher levels. Practically, the component cell to be measured should have some illumination,
as device spectral responsivities can be a function of the illumination level.
7.1.3.4 Turn on the bias light source and illuminate, as a minimum, the region where the monochromatic beam illuminates the
test device.
7.1.4 Measure the V of the test device.
oc
7.1.5 Calculate the bias voltage to use during the test:
7.1.5.1 For devices with component cells that contribute similar voltages, calculate the bias voltage according to Eq 1.
n 2 1
V 5 V . (1)
b oc
n
7.1.5.2 For devices with component cells contributing substantially different voltages, calculate the bias voltage as the sum of
the expected voltage contributions from the component cells not being measured.
7.1.6 Set the V on the bias voltage source.
b
7.1.7 Connect the test device to the ac measurement instrumentation.
7.1.8 Maximize the ac signal from the component cell under test using a wavelength at which it is expected to respond:
7.1.8.1 Set the monochromatic light source to a wavelength in the expected spectral response region of the component cell to
be measured.
7.1.8.2 Adjust the bias light intensity to saturate or maximize the test device signal.
7.1.9 Minimize the test device signal at wavelengths where the component cells not being measured are expected to respond:
7.1.9.1 Set the monochromatic light source for a wavelength in the expected spectral response region of the component cell not
being measured.
7.1.9.2 Minimize or zero the test device signal by adjusting the bias light intensity.
7.1.9.3 Repeat 7.1.9.1 and 7.1.9.2 for additional component cells not being measured, if any.
7.1.10 As in 7.1.8 and 7.1.9, adjust V to further maximize the signal in 7.1.8 and further minimize the signal in 7.1.9.
b
E2236 − 10 (2015)
7.1.11 Select light bias and voltage bias levels that both maximize the signal in 7.1.8 and minimize the signal in 7.1.9. The signal
in 7.1.9 should correspond to a quantum efficiency, Q(λ), that is less than 0.01 in wavelength regions where the component cell
being measured is known to have no response.
7.1.12 It may be necessary to adjust the bias light source in 7.1.3 to obtain a light bias condition that satisfies 7.1.11.
7.1.13 Measure the relative spectral response of the component cell being tested according to Test Methods E1021.
7.1.14 Repeat 7.1.2 – 7.1.13 for each component cell of the multijunction device under test.
7.2 Electrical Performance, spectrally adjustable Solar Simulator:
7.2.1 Adjust the total irradiance of the spectrally adjustable solar simulator to a level close to the desired reporting conditions
using a reference cell or previous experience (this initial irradiance level is not critical).
7.2.2 Measure the spectral irradiance of the spectrally adjustable solar simulator with a spectroradiometer calibrated according
to Test Method G138.
7.2.3 Calculate the spectral mismatch parameter, M , for each component cell in the multijunction device under test using the
i
spectral responses obtained in 7.1, the reference cell spectral responses, the spectral irradiance measu
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