Quantitative evaluation of electroluminescence images of solar cells

Abstract

A fast converging iterative procedure is proposed to calculate series resistance (Rs) and saturation current (j0) images from two electroluminescence (EL) images taken at two biases. It is not necessary here that for one bias the influence of the series resistance is negligible. Moreover, voltage series of EL images have been evaluated for calculating images of Rs, j0, and the parallel conductance Gp separately. However, it has been found that Rs variations cannot uniquely be separated from Gp variations. The reason for this is discussed. Thus, for quantitatively detecting weak ohmic shunts, EL imaging cannot replace lock-in thermography. For strong ohmic shunts a formula for converting EL images into shunt images is given. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.