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A solar simulator reproduces sunlight — its spectrum, intensity, and uniformity — so photovoltaic cells and materials can be tested under controlled, repeatable conditions. An LED solar simulator does this by combining many LED wavelengths into a tunable array that approximates the standard AM1.5G reference spectrum across roughly 300–1200 nm (and out to the SWIR for full spectral-match grading). Compared to the xenon arc lamps that simulators traditionally used, LEDs offer per-channel spectral control, far longer life, instant stable output, and no lamp warm-up — which is why they now dominate new PV-test equipment. Performance is graded against IEC 60904-9 on three axes (spectral match, spatial uniformity, temporal stability), yielding the familiar Class A/B/C — and "AAA" for the best on all three.
| Spectral band | Role in the simulator | Tech-led LEDs |
|---|---|---|
| UV (350–400 nm) | Short-wavelength end of AM1.5; UV-durability testing | UV LEDs (365/405 nm) |
| Visible (400–700 nm) | Bulk of solar irradiance; silicon PV response | Visible LEDs |
| NIR (700–1100 nm) | Silicon cell response tail; key for spectral match | IR/NIR LEDs |
| SWIR (1100–1700 nm) | Extends match for tandem/thin-film cells | SWIR LEDs |
How an LED solar simulator works
The AM1.5G spectrum is the standard terrestrial reference: the sunlight reaching the ground at a defined air mass, normalized to 1000 W/m² ("one sun"). It is not flat — it rises through the visible, peaks in the green-red, and tails off through the near-infrared with characteristic atmospheric absorption dips.
An LED simulator reproduces that shape by combining many narrow-band LED channels — each contributing power in its band — and balancing their drive currents until the summed output matches the reference spectrum band by band. Because each channel is independently controllable, the spectrum can be tuned, dimmed, and even modulated to simulate different conditions (cloud, time of day, AM0 space spectra). The array is arranged and diffused for spatial uniformity across the test plane and driven by stable constant-current electronics for temporal stability — the other two grading criteria.
Applications
Photovoltaic cell and module testing
The primary use. Simulators measure a cell or module's efficiency, I-V curve, fill factor, and temperature coefficients under standardized one-sun illumination. Accurate spectral match matters because a cell's response is wavelength-dependent — a simulator that is too blue or too red biases the efficiency reading. Multi-junction and tandem cells make this stricter, since each sub-cell responds to a different band, which is where wide-spectrum LED arrays (UV through SWIR) earn their place.
Materials durability and weathering
Coatings, textiles, polymers, and plastics are exposed to simulated sunlight to assess UV resistance, colorfastness, and thermal/light aging. The UV and NIR portions of the spectrum drive most of this degradation testing.
Solar system and component validation
Full systems — panels, inverters, batteries — are stress-tested under dynamic, high-intensity illumination to validate response across conditions before field deployment.
Standards and spectral-match classes
LED solar simulators are graded under IEC 60904-9 (and the related ASTM E927 and JIS C 8912) on three independent criteria:
- Spectral match — how closely the output matches AM1.5G across defined wavelength bins.
- Spatial non-uniformity — how even the irradiance is across the test plane.
- Temporal instability — how stable the output is over time.
Each criterion is rated A, B, or C, so a top simulator is "AAA" (Class A on all three). LEDs make Class A spectral match more achievable than fixed-spectrum xenon because individual channels can be trimmed to fill or flatten bins, and they hold temporal stability easily with constant-current drive.
Why LEDs replaced xenon arc lamps
| Factor | LED simulator | Xenon arc lamp |
|---|---|---|
| Spectral control | Per-channel, tunable | Fixed spectrum with strong xenon peaks (needs filtering) |
| Lifetime | 20,000–50,000+ h | ~1,000–2,000 h (lamp) |
| Warm-up / stability | Instant on, stable | Warm-up required; drifts as lamp ages |
| Modulation | Fast, per-channel dimming | Limited |
| Spectral peaks | Smooth, buildable | Sharp NIR xenon lines distort match |
Tech-led supplies the UV, visible, IR/NIR, and SWIR LED emitters used to build multi-wavelength simulator arrays. For component selection, datasheets, and samples, contact Tech-led engineering.
Frequently asked questions
What is a solar simulator?
A solar simulator is a device that reproduces sunlight — its spectrum, intensity, and uniformity — so photovoltaic cells and materials can be tested under controlled, repeatable conditions instead of variable real sunlight. It targets the standard AM1.5G reference spectrum at one-sun intensity (1000 W/m²).
How do LED solar simulators replicate sunlight?
They combine many narrow-band LED channels spanning UV through near-infrared (and SWIR for full grading) and balance each channel's output until the summed spectrum matches the AM1.5G reference band by band. Independent channel control allows tuning, dimming, and dynamic-condition simulation.
What is the AM1.5 spectrum?
AM1.5G ("air mass 1.5, global") is the standard terrestrial solar reference spectrum — the sunlight reaching the ground through 1.5 atmospheres, normalized to 1000 W/m². It's the spectrum PV cells are rated against, so a simulator's job is to match it.
What are solar simulator Class A, B, and C ratings?
Under IEC 60904-9, a simulator is graded on three criteria — spectral match, spatial non-uniformity, and temporal instability — each rated A, B, or C. A simulator rated Class A on all three is called "AAA," the highest grade. LED simulators reach Class A spectral match more easily because individual channels can be trimmed.
Why use LEDs instead of xenon lamps in solar simulators?
LEDs offer per-channel spectral control (so you build the AM1.5 shape rather than filter a fixed one), 20,000–50,000+ hour life versus ~1,000–2,000 for xenon, instant stable output with no warm-up, and fast modulation. Xenon lamps have sharp NIR peaks that distort spectral match and drift as they age.
What wavelengths does an LED solar simulator need?
It needs coverage across the solar spectrum: UV (~350–400 nm), the full visible (400–700 nm), and near-infrared (700–1100 nm) for silicon-cell response, extending into the SWIR (1100–1700 nm) for full IEC spectral-match grading and for tandem/thin-film cells that respond beyond silicon's range.
Can LED solar simulators test multi-junction cells?
Yes — and it's a key advantage. Multi-junction and tandem cells have sub-cells that each respond to a different band, so matching the spectrum across the whole range matters. A wide-spectrum LED array (UV through SWIR) with per-channel control can balance the bands each sub-cell needs.
Related guides
- Industrial UV LED Guide — the UV portion of the spectrum
- SWIR LED Lighting Guide — extending spectral match beyond silicon
- LED Wavelength Guide: From UV to Infrared — the full spectrum map
- Machine Vision Lighting — related multi-wavelength illumination
Building an LED solar simulator array? Contact Tech-led engineering for UV, visible, NIR, and SWIR LED recommendations, datasheets, and samples.
