Electroluminescence as Characterization Tool for Polymer Solar Cells and Modules

We show that laterally resolved luminescence detection is a highly versatile measurement technique for the characterization of polymer solar cells and modules. Besides lock-in thermography also luminescence imaging is highly suitable for quality control of processing steps, especially the control of homogeneous layer deposition and the proper lateral function of polymer solar cells and modules, by identification of local defects. Furthermore the application of luminescence imaging allows discrimination between active layer and organic/electrode-interface degradation in stability experiments. By correlation with photovoltaic parameters important conclusions can be drawn with respect to the specific degradation mechanism. For quantitative interpretation of such electroluminescence images, we propose an equivalent circuit model in which local solar cells are interconnected by resistors representing the sheet resistance of the transparent electrode. In combination with the laterally resolved measurement of electroluminescence, the application of this model allows calculation of local photovoltaic parameters and quantification of the lateral current and voltage distribution.