This demonstrates that according to the new IEC standard, SS-X achieves superior spectral classification across all wavelength bands. Under the new IEC standard, it maintains better spectral grades in each band. The maximum spectral mismatch in each band is less than 9% (A+ class requirement is <12.5%). In comparison, while other brands meet Class A requirements (25% mismatch), they show up to 21% mismatch in the 772nm-919nm band. This IR band covers the absorption band edge of many next-generation solar cells, such as perovskite and organic solar cells, affecting IV and conversion efficiency results. Therefore, spectral matching is crucial for accurate solar cell characterization.

Validation with Real Solar Cell Devices

A stable device with absorption band edges and EQE curves similar to organic and perovskite solar cells was selected. The EQE curve shown in Figure 2 was measured using Enlitech’s QE-R EQE system. The QE-R system is currently the world’s leading EQE testing system, adopted by numerous international solar cell research laboratories. Over the past five years, QE-R has been specifically cited in over 1000 SCI journal publications, with its Jsc(EQE) test results widely recognized by experts and scholars worldwide.

Figure 2. External Quantum Efficiency (EQE) spectrum of the Device Under Test (DUT), showing EQE response similar to perovskite and organic solar cells.

How to Verify IV Measurement Accuracy Across Different Simulators?

The most common and crucial method we use when submitting to scientific journals is the comparison between Jsc(SS) and Jsc(EQE). Jsc(SS) represents the short-circuit current density measured under the solar simulator, while Jsc(EQE) is the integrated short-circuit current density from the EQE curve with the AM1.5G spectrum. The Jsc(EQE) methodology is detailed in the IEC 60904-7 standard. The difference between Jsc(SS) and Jsc(EQE) is considered a reliability criterion by solar cell societies and journal reviewers. Generally, results are considered accurate and reliable if the difference between Jsc(SS) and Jsc(EQE) is within 5%. We will use this method to validate the differences between A+ and A class solar simulator spectra. The experimental procedure is as follows:

1. Reference Cell Calibration:A WPVS-type reference solar cell with absorption band edge at 850nm, calibrated by NREL, is used to calibrate solar simulator light intensity.
2. IV Measurement System:IVS-KA6000 IV software controls the SMU Keysight B2901 to read current-voltage curves of the device under test.
3. Temperature Monitoring:Platinum temperature sensors monitor device temperature variations to minimize temperature-induced errors.

IV curves and solar cell performance parameters are shown in Figure 3. The short-circuit current densities under Enlitech’s SS-X50 and other brand solar simulators are 22.388 mA/cm² and 21.482 mA/cm² respectively. While the Jsc(SS) values under both solar simulators are relatively close, which one is more accurate? We can compare with Jsc(EQE) to determine this. As shown in Figure 2, Jsc(EQE), integrated from the EQE curve with the AM1.5G spectrum, equals 22.44 mA/cm².

Figure 3. IV curves and solar cell performance parameters.

Table 4. Comparison of Jsc(SS) and Jsc(EQE).

The comparison table shows Jsc(SS) and Jsc(EQE) values in Table 4. We can observe that the Jsc(SS) under the SS-X50 solar simulator is very close to Jsc(EQE). The difference is 0.11%, significantly smaller than the 2.18% difference observed with other brand solar simulators. This is because the SS-X50 has A+ spectral classification, providing better spectral matching with AM1.5G spectrum. Consequently, it can provide more accurate solar cell test results without requiring spectral mismatch correction. Other brand solar simulators are Class A rated. However, their spectra show over 20% negative deviation from AM1.5G in the 712nm-919nm band, which is the primary reason for the larger (2.18%) difference between Jsc(SS) and Jsc(EQE).

From these results, while both A+ and A class solar simulators can provide less than 5% difference between Jsc(SS) and Jsc(EQE) when testing procedures are properly conducted, the increasing competition in modern high-efficiency solar cell development makes even a 0.3% PCE difference significant, potentially leading to new world records. Therefore, choosing an A+ spectral class solar simulator is both necessary and valuable.