Fill factor analysis of solar cells' current-voltage curves
After completion of the solar cell manufacturing process the current-density versus voltage curves (J(U) curves) are measured to determine the solar cell's efficiency and the mechanisms limiting the efficiency. An accurate and robust analysis of the measured curves is essential. In this work it is shown that fitting the two-diode model is inappropriate to quantify recombination in the space charge region and ohmic losses due to series resistance. Three fill factors, namely the fill factor of the illuminated J(U) curve, the pseudo fill factor of the sunsVoc curve and the ideal fill factor of the single diode model, are the base of a quick loss analysis that is evaluated in the present paper. It is shown that for an accurate analysis the distributed character of the series resistance and the network character of the solar cell cannot be neglected. An advanced current-voltage curve analysis including fill factors and fit is presented.