Design,realization and uncertainty analysis of a laser-based primary calibration facility for solar cells at PTB

A completely newly designed multi-functional facility for the primary calibration of reference solar cells and the spectral characterization of all solar cell types has been developed and built at PTB. The new facility is based on the successfully applied Differential Spectral Responsivity (DSR) method that allows the determination of the absolute spectral responsivity and nonlinearity of solar cells with the lowest uncertainties. By using a tunable laser system, the new setup avoids the main problem of monochromator-based systems: the low optical power level of the monochromatic beam. Thus it enables a significant reduction of the uncertainty for the short circuit current under standard test conditions I_STC of solar cells. It enables the calibration of World Photovoltaic Scale (WPVS) reference solar cells with an uncertainty of 0.4% (k = 2), the lowest value stated by any WPVS laboratory.