Determination of base doping concentration of silicon solar cells from light IV-curves

In this contribution we present a novel method to determine the base doping concentration of solar cells from current-voltage (IV) curves measured under illumination. Our method is based on counting the charge carriers which are stored during an IV-sweep inside the Si bulk of the solar cell. We derive this charge from a comparison of a single sweep IV-curve and a steady-state IV-curve. Besides a detailed explanation of our new method, we analyze its applicability and repeatability and present an independent confirmation based on state-of-the-art capacitance-voltage (CV) characterization. We perform this confirmation of our results on a number of cells with different cell architectures ranging from p-type PERC solar cells over n-PERT cells to TOPCon and HJT structures. The base doping concentration determined by our method match the results of the reference CV measurements adequately with an approximate measurement uncertainty of 20%. In contrast to time consuming laboratory methods that require offline sample characterization, our evaluation is performed without the need of additional measurement equipment or measurement time and is ready for inline usage in solar cell mass production.