Spectral Mismatch Uncertainty Estimation in Solar Cell Calibration Using Monte Carlo Simulation

A solar cell is characterized using a solar simulator and a reference cell in accordance with standard testing conditions. Deviations between the spectral responsivities of the reference cell and the cell being studied, and deviations of the spectral irradiance of the light source used from the specified air mass 1.5 introduce systematic errors in the calibration of solar cells. These errors are corrected with the so-called spectral mismatch (SMM) correction factor. We demonstrate a Monte Carlo simulation-based analysis of the uncertainties present in an SMM correction factor taking into account the possible spectral correlations of the input parameters, such as the spectral irradiance and the spectral responsivities of the reference cell and the solar cell under test. We also perform a detailed uncertainty analysis of the subcomponents of the SMM factor mainly arising from the spectral irradiance incident on the solar cell. In order to test our estimates, we present a comparison of the uncertainties by six other independent calculations carried out by other institutes. We obtain the worst-case, average, and best-case scenario uncertainties of the SMM correction factor by assuming components to be severely correlated, partially correlated, and not correlated, respectively. The corresponding expanded uncertainties (k= 2) are 1.26%, 0.44%, and 0.06%. The worst- and best-case uncertainties lie at the maximum and minimum extremes of the uncertainties estimated by the participants, while the uncertainty estimate obtained assuming partial correlations is close to the median and mean of all results.