Accurate series resistance measurement of solar cells

The series resistance (Rs) of a solar cell is commonly represented as a constant resistance value. However, because of the distributed nature of series resistance, the effective lumped Rs vary with current density and illumination intensity. Treating Rs as a constant is usually insufficient for an accurate analysis of its JV curve. This work first presents a review of the distributed nature of series resistance and commonly applied methods to measure Rs. Particular attention is given to the multi-light method (MLM) and it is discussed in detail, where Rs in both the light and dark can be measured as a function of current by extracting Rs from a set of currentvoltage (JV) curves attained at different illumination intensities. The principle behind this method is discussed, and the results are then compared with those of other known methods of Rs measurement. The accurate measurement of Rs(J) attained with the MLM permits the extraction of an Rs-corrected JV curve, which is theoretically more accurate than that attained by alternative methods because of negligible error from injection dependence and spectral mismatch. With the solar cell equation modified to include Rs(J), we attain a much better fit to experimental data, finding a significant reduction in error compared with using a constant Rs. Copyright (c) 2011 John Wiley & Sons, Ltd.