Solar cell tester and module tester

The calibration of solar cell tester and module tester is the one of the important factors. The solar cell calibration from standard lab or certifying agency defines the range (up to +/-0.3%)for the efficiency/power measurement of the calibration solar cell. The mismatch can vary if calibration is done on either side of the range defined or the spectrum of light source used in the testers are different. The spectral response of the calibration solar cell and the calibration module has to be matched to minimize the CTM loss caused by measurement mismatch.

In my views followings factors influence the CTM loss:
1. Calibration/measurement mismatch between solar cell and module
2. Spectrum response mismatch of calibration solar cell and calibration module
3. Method of electrical sorting of solar cell (on the basis of efficiency/load current......)
4. Efficiency range for a particular Bin (+/-0.1%, +/-0.05%, 0/+0.2%...)
5. Module materials (glass reflectivity-textured glass/ARC glass, EVA-spectrum response of EVA, soldering ribbon resistance, junction box resistance etc)
6. Module process (soldering process-contact resistance, string resistance etc)
7. Module calibration
8. LID mainly for Mono
9. Solar cell manufacturing technology (Standard vs Selective Emitter). Higher power loss is observed with SE solar cells due to cut off frequency limitation of EVA.

Typically CTM loss is between 1-2% for +/- efficiency sorting of solar cell which can be Zero also if solar cells are sorted for +ve sorting or downgraded to lower Bin. Normally, the FF difference between solar cell and module is the prime reason for loss and the new technology is moving to fill up the gaps.