A solar simulator provides controlled light for solar-cell and optical testing. An Air Mass filter shapes the source toward a chosen solar spectrum; the required design depends on the source and the complete optical path.
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AM0: outside the atmosphere
AM0 describes sunlight before passage through Earth’s atmosphere. It is a reference used for space-oriented photovoltaic evaluation. The “0” describes atmospheric path, not a filter’s transmission percentage.
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AM1.5G: a terrestrial reference
Air mass 1.5 describes a relative atmospheric path. The G denotes global irradiance, including direct and diffuse contributions on the reference tilted surface. This reference supports consistent terrestrial photovoltaic evaluation; it is not a description of every outdoor location or weather condition.
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Standards and performance targets
Reference-spectrum documents and simulator classification standards serve different purposes. Read our Air Mass product guide for IEC, ASTM and Japanese JIS context, the three AAA criteria, and how a band-integrated ±5% matching requirement is defined.
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What the filter contributes
The source spectrum and filter transmission work together to determine the resulting light. A passive filter can attenuate excess spectral components; it cannot supply energy at wavelengths absent from the source. Other optics and source stability contribute to the final output.
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For the simulator developer
Specify the target reference, working wavelength interval, source output, angle distribution, beam size and thermal load. Evaluate the spectrum at the intended test plane. Spectral match, spatial uniformity and temporal stability are separate system characteristics: a filter curve by itself does not establish the simulator’s classification.
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From one junction to several
Tandem photovoltaic devices use different junctions to harvest different portions of the spectrum. Their evaluation therefore benefits from checking the spectral balance seen by each junction, rather than treating total irradiance as the only relevant quantity.
Editorial review: 17 September 2026 · Educational principles support product selection; model-specific performance is established by the product data and agreed specification.