On the use of electroluminescence-based reciprocity relations for quantitative mapping of PV modules performance

In the present study, we develop a new characterization methodology allowing to directly convert standard electroluminescence (EL) images of a given PV module into absolute quantitative performance maps. The experiments and results were obtained based on both multi-crystalline Al-BSF and mono PERC bifacial silicon modules. After acquiring two EL images, we show that by applying the generalized reciprocity relations, it is possible to optically extract key performance indicator maps. We demonstrate the ability to extract an optical I-V characteristics whereby we optically map the current collection efficiency, the current density, the series resistance across the studied multi-crystalline silicon modules. In addition, we are able to provide a first luminescence-based experimental map of the bifaciality coefficient of the studied mono PERC silicon modules. The results were finally validated by comparing the mean central values extracted from the optically determined maps with the values extracted from electrical I(V) measurements. Such agreement opens the potential of using the presented work for a better control of module reliability, testing accuracies and optimization of manufacturing processes.