ASTM E973 Spectral Mismatch Testing for Photovoltaic Devices
ASTM E973 is a widely used method to determine the spectral mismatch parameter, which is essential in evaluating the performance of photovoltaic devices. All SI unit values are considered standard in this test.
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- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
Overview
ASTM E 973 spectral mismatch parameter testing is a standardized test procedure for determining the spectral mismatch correction factor between a photovoltaic device being tested and a photovoltaic reference cell, i.e., the amount of error in the measurement of a photovoltaic device’s electrical performance caused by differences in the spectral content of the solar simulator’s irradiance and the AM1.5 spectrum in the spectral response ranges of the photovoltaic device and the reference cell. ASTM E 973 specifies procedures for measuring spectral irradiance and the data requirements for spectral response and mismatch correction factor calculations needed to make accurate spectral mismatch corrections to the electrical performance measurements of a photovoltaic device.
Scope, Applications, and Benefits
Scope
It is the objective of the ASTM E 973 standard to define the spectral mismatch correction factor by determining the solar simulator’s spectral irradiance distribution, the spectral response of both the PV under test and the reference cell, and the mismatch parameter from the overlap integrals of the solar irradiance spectrum and the response spectrum within the defined range of wavelengths.
ASTM E 973 spectral mismatch testing evaluates:
- Spectral mismatch correction factor between PV devices and reference cells under solar simulators
- Solar simulator spectral irradiance distribution relative to AM1.5 reference spectrum
- Spectral response mismatch between the PV device under test and the reference cell technologies
- Measurement uncertainty contribution from spectral mismatch in PV performance testing
- Compliance with spectral mismatch correction requirements for PV measurement standards
Applications
- Silicon, thin film, and multi-junction PV cell and module electrical performance measurement
- Solar simulator spectral mismatch assessment for PV testing laboratory accuracy programs
- PV reference cell selection and mismatch optimization for defined PV device technologies
- Concentrating photovoltaic and space solar cell spectral mismatch characterization programs
- PV test laboratories requiring ASTM E 973 spectral mismatch correction factor data
Benefits
- Provides reliable spectral mismatch correction data for accurate PV device performance measurement
- Supports PV measurement standard compliance and test laboratory accuracy assurance programs
- Identifies significant spectral mismatch errors before PV device performance reporting
- Delivers traceable spectral mismatch correction records for engineering and research submissions
- Reduces PV measurement uncertainty by applying spectral mismatch corrections early in test programs
Test Process
Spectral Irradiance Measurement
Solar simulator spectral irradiance measured using calibrated spectroradiometer per ASTM E 973.
1Spectral Response Data Collection
Spectral response data obtained for PV device under test and reference cell per ASTM E 973.
2Mismatch Factor Calculation
Spectral mismatch correction factor calculated from overlap integrals of irradiance and response data.
3Data Analysis & Reporting
Mismatch factor assessed against correction requirements and applied for test compliance result.
4Technical Specifications
| Parameter | Details |
|---|---|
| Applicable Devices | Silicon, thin film, multi-junction, and concentrating PV cells and modules |
| Spectral Range | 300 nm to 1200 nm wavelength range per ASTM E 973 spectral integration requirements |
| Reference Spectrum | AM1.5 global solar spectrum per ASTM E 490 for mismatch factor calculation |
| Mismatch Parameter | Spectral mismatch correction factor M calculated from four spectral overlap integrals per ASTM E 973 |
| Measured Outputs | Spectral irradiance data, spectral response curves, mismatch factor M, and test compliance result |
Instrumentation Used for Testing
- Calibrated spectroradiometer for solar simulator spectral irradiance distribution measurement
- Solar simulator with defined spectral class rating for PV device illumination
- Spectral response measurement system for PV device and reference cell characterization
- Reference photovoltaic cell with traceable calibration for irradiance setting verification
- Specialist spectral mismatch calculation software for overlap integral computation
- Data reporting and spectral irradiance visualization system
Results and Deliverables
- Solar simulator spectral irradiance distribution data across the 300 nm to 1200 nm wavelength range
- Spectral response curves for the PV device under test and the reference cell per ASTM E 973
- Calculated spectral mismatch correction factor M with associated measurement uncertainty
- Test compliance result assessed against PV measurement standard spectral mismatch requirements.
- ASTM E 973 spectral mismatch test report for PV performance measurement, research, and laboratory assessment submissions
Why Choose Infinita Lab for ASTM E972?
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Frequently Asked Questions
ASTM E972 measures solar photometric transmittance using natural sunlight, including incident irradiance approximately 1000 W/m², transmitted light intensity, angle of incidence, and sample orientation to evaluate optical performance of sheet materials.
ASTM E972 requires clear sky conditions, stable sunlight, consistent solar angle, controlled sample alignment, and simultaneous measurement of incident and transmitted radiation to ensure accurate photometric transmittance evaluation.
ASTM E972 is commonly applied to glass, plastic sheets, films, glazing materials, and transparent panels used in architectural, automotive, and solar energy applications where light transmission performance is critical.
ASTM E972 uses calibrated photometers or radiometers, mounting fixtures for specimen positioning, and measurement systems to record incident and transmitted light intensity under natural sunlight exposure conditions.
ASTM E972 depends on natural sunlight, and results may vary due to atmospheric conditions, cloud cover, solar angle changes, and environmental variations, affecting repeatability and comparability of photometric transmittance measurements.
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