Accuracy of Simplifications for Spectral Responsivity Measurements of Solar Cells

Abstract

The determination of the spectral responsivity is an essential part of solar cell characterization. Since solar simulators only approximate the reference spectrum, a spectral mismatch correction has to be performed. This correction procedure requires spectral responsivity data. Apart from the complete differential spectral responsivity procedure, the IEC 60904-8 standard defines four simplifications. In this paper, we provide information on the variations in the spectral responsivity curves for these simplifications. We show that for nonlinear front junction cells, deviations predominantly occur at wavelengths above 700 nm and become largest around 1000 nm. While we found a maximum deviation of 30% for the simplification with lowest requirements in bias irradiance, all other simplifications yield deviations below 10%. For a nonlinear cell measured relative to a world photovoltaic scale reference cell using a class A solar simulator, this transfers to a deviation below 0.01% in the spectral mismatch factor. If one depends on the use of a simplification, we recommend using the multicolor approach. Even though the singlecolor approach might yield lower deviations, this approach requires knowledge about the maximum in the spectral responsivity, which is not generally known in advance of the measurement. Accepting a slightly higher deviation, the white bias approach is a recommendable alternative.