Averaging the unaverageable: Defining a meaningful local series resistance for large-area silicon solar cells

摘要

From its definition based on lateral voltage drops, the local series resistance isn't an arithmetically averageable quantity because voltage isn't extensive; however, only such quantities can be averaged. Still, empirically it was found that averaging series images arithmetically provides rather reasonable results. Since the emitter of a large-area silicon solar cell is nearly an equipotential layer, one can linearize the description of the lateral voltage distribution (with respect to the forward-bias current and the emitter resistivity), from which we obtain an averageable local series resistance for the H-type grid geometry; its averageability stems from averaging the parallel paths of vertical current flow. By construction, the average obtained from this linear response theory is identical to the lumped value coming from the illumination intensity variation method, and it also shows the experimentally observed dependency on the forward-bias diode current.