# Solar simulator method (SSM)

Ingo Kroeger

###### The solar simulator method (SSM)

The solar simulator method uses artificial light sources to emulate the AM1.5g spectral irradiance. The light engine is often made from Xenon lamps (or Xe- and halogen multi lamp systems) combined with optical filters and homogenizing optics to generate a uniform irradiance in the measurement plane. For this method a reference is needed with calibrated short circuit current under STC and spectral irradiance responsivity under STC. differential spectral irradiance responsivity. In the measurement plane there should be a monitor solar cell that can be measured simultaneously with the DUT or the reference. The DUT and the reference must be temperature controlled and kept at 25°C. The calibration procedure would be as follows:

1. Place the reference device in the centre (i.e. location of the best uniformity) of the light field, wait until the temperature reading is stable within 25°C ± 1°C and adjust the solar simulator lamp current or the distance between light source and measurement plane until the calibrated short circuit current at STC of the reference is measured. Also measure the current of the monitor.
2. Place the DUT in the exact same position as the reference, wait until the temperature reading is stable within 25°C ± 1°C and measure its short circuit current. Also measure the current of the monitor.
3. If there is a difference of the two monitor readings, the irradiance level has drifted. Correct the measured short circuit current of the DUT by the correction factor given by the ratio of $\displaystyle{ f=\frac{I_{Mon,\ DUT}}{I_{Mon,\ Ref}} }$
4. Apply the spectral mismatch correction factor on the measured current of the DUT, if the spectral responsivity of DUT and reference differ significantly. For this correction the relative spectral irradiance distribution must be measured in the exact position of the DUT with the identical settings of the solar simulator of the calibration using a calibrated spectroradiometer. Additionally, the relative spectral irradiance responsivity of the DUT must be known. This could be measured using a simplified DSR-method as described above.
5. If the DUT and the reference are of different size, a correction accounting for the non-uniformity of the irradiance in the measurement plane has to be applied

More detailed information on this method can be found in Ref. [24-28].

## References

[4] IEC 60904-4:2009, Photovoltaic devices - Part 4: Reference solar devices - Procedures for establishing calibration traceability

[24] R. Shimokawa, F. Nagamine, Y. Miyake, K. Fujisawa, Y. Hamakawa “Japanese indoor calibration method for the reference solar cell and comparison with outdoor calibration” Japanese J. Appl. Phys. 26(1) (1987) 86-91.

[25] R. Shimokawa, H. Ikeda, Y. Miyake, S. Igari "Development of wide field-of-view cavity radiometer for solar simulator use and intercomparison between irradiance measurements based on the world radiometer reference and electrotechnical laboratory scales" Japanese J. Appl. Phys. 41 (2002) 5088-5093.

[26] H. Müllejans, W. Zaaiman, F. Merli, E. D. Dunlop, H. A. Ossenbrink “Comparison of traceable calibration methods for primary photovoltaic reference cells” Progress in Photovoltaics 13 (2005) 661-671.

[27] CIE 53-1982 “Methods of Characterizing the Performance of radiometers and Photometers”, ISBN 92 9034 053 3.

[28] CIE 63-1984 “The Spectroradiometric Measurement of Light Sources”.