Current and illumination dependent series resistance of solar cells

Precise knowledge of the series resistance is essential for failure and loss analysis as well as yield prediction of solar cell devices. In this work, a method which determines the current and photogeneration dependence of the series resistance without assuming any specific current-voltage characteristic for the internal diodes is presented. This approach is of particular interest for solar cells which cannot be described by the one- or two-diode model such as organic solar cells. Furthermore, it clarifies the difference in the series resistance values that are obtained from current-voltage curves in the dark and under illumination as well as short-circuit-current and open-circuit-voltage characteristics. Additionally, it is shown how other cell parameters, such as the shunt resistance or the current-voltage characteristic of the internal diode are determined in a consistent way. Finally, it is demonstrated that our approach can be easily implemented in a new generation of solar simulators that are based on light-emitting diodes instead of conventional light sources.