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J. Eur. Opt. Society-Rapid Publ. 22, 52( 2026)
( a)( b)( c)
Fig. 1.( a) Measurement setup with a triggered fast spectrometer next to the DUT;( b) 1-sun setup, with radiation from one lamp illuminating the DUT through an aperture / lens fixture;( c) schematic of the setup shown in( b), displaying the trigger photodiode and the spectrometer slit both next to the DUT, under the light from the Fresnel lens. I-V sweeps( either voltage or current controlled) during the constant region of the flash extinction.
So far, most of literature [ 10, 11 ] lacks fast spectral characterization of pulsed solar simulators, and those who employed fast spectrometer setups [ 12, 13 ] reported important effects that could not be measured with steady-state spectrometers, such as the illumination spectra shifting from blue rich to red rich during the flash extinction.
This work focused on the spectral characterization of a pulsed solar simulator, which makes use of xenon lamps discharge to produce fast( few milliseconds) flashes with good spectral and intensity uniformity over the illuminated area of the DUT. Solar simulator’ s pulsed flashes were extensively characterized in time and wavelength, to evaluate the impact of lamp’ s supply voltage on the flash extinction, and therefore on the measured I – V curves of three DUTs: a top single junction( SJ), a bottom SJ, and a silicon photodiode. The measurement setup can be of low impact, as it can be placed next to the DUT without any relevant shadowing, to allow the in-situ characterization of the exact light hitting the device during that specific measurement.
2 Material and methods
In-situ fast spectral characterization was carried out through the setup displayed in Figure 1. We employed a Technoexan Ltd( an innovation company of the Ioffe Institute in St. Petersburg, Russia) CLASS A( in 400 – 1200 nm) pulsed solar simulator, designed to work with either semicollimated 1-sun radiation, with the aperture / lens fixture visible in Figure 1b, or in concentration, up to 5000 suns.
The simulator is designed to ensure a 5 % spatial light uniformity across a 2 cm 2 cm area, a 2 % flash-to-flash stability, and can emit a pulse of light once every 15 s.
Current – voltage sweeps are carried out through fast voltage discharges over the 800 ls constant region of the flash extinction, to record light I – V characteristics in the range �5 V /+ 10 V and up to 10 A.
The solar simulator is equipped with four xenon arc lamps, allegedly identical, each mounted with an absorption filter to include atmospheric absorption and emulate the standard ASTM G173-03 AM1.5 1000 W / m 2 irradiance spectrum. The measured curves should be independent of lamp, from manufacturer’ s specifications.
To characterize the flash occurring during the I – V sweep, which lasts around 800 ls, a microprocessor-based custom-made circuit was built and set to trigger a measurement once input from a photodiode exceeded a set threshold. Spectra were recorded by the commercially available Ocean Optics FX-XR1-ES CCD spectrometer, used without further modification, in free-space, coupled directly with the semi-collimated light of the simulator. This spectrometer was chosen for its speed, since it’ s capable to perform one measurement every 221 ls with an integration time of 10 ls, and for its measurement range: 200 – 1025 nm, with a 0.4 nm resolution( typical). To characterize the whole flash extinction, therefore, 27 consecutive measurements were performed over a 6 ms duration, each containing 2136 points between 200 and 1025 nm. However, only the 350 – 950 nm range is reported, as it’ s the most relevant.
As visible in Figure 1, spectrometerslitandtriggerphotodiode were put directly in the simulator’ s chamber, next to the DUT.
Together with fast spectral characterization of flashes, I – V curves were recorded by the instrument itself, through its custom source-meter unit that performs voltage – current sweeps during the 800 μs measurement window. Three different photovoltaic devices were measured for this purpose: a top SJ manufactured by Fraunhofer and sensitive in the 300 – 700 nm range(“ SJ top”), a bottom SJ manufactured by Fraunhofer and sensitive in the 850 – 1800 nm(“ SJ bot”), and a silicon photodiode manufactured by THOR- LABS( p / n FDS1010) and sensitive in the 350 – 1100 nm range(“ Si PD”).