Short-Circuit Current Density Imaging Via PL Image Evaluation Based on Implied Voltage Distribution

Abstract

Luminescence imaging has found wide application for the characterization of silicon solar cells and wafers over the past decade. One special application is based on a combination of electroluminescence and photoluminescence imaging. Images of a single solar cell at different operating conditions are taken. With suitable methods, it is possible to evaluate the image series and extract spatially resolved solar cell parameters. In the past, methods have been introduced focusing on the extraction of local dark saturation current density and local series resistance. Past methods usually assumed a laterally homogeneous short-circuit current density corresponding to laterally homogeneous external quantum efficiency. In this study, we give a step-by-step description of a newly developed method, which does not rely on the assumption of homogeneous short-circuit current density. The evaluation method instead additionally yields an image of the local short-circuit current density or of the external quantum efficiency. We apply the method to different solar cell types, and we give a detailed comparison to its predecessor the “coupled determination of dark saturation current density and series resistance” method. We compare the short-circuit current density images with images obtained from the “light beam-induced current” technique.