Optical measurements of morphology-to-functional parameters on electrical contacts of photovoltaic cells

Traceable parameters for determining the relationship between texture, form, sizes and resistance behaviour of functional surfaces' features, such as screen-printed electrodes with grids of different design either on c-Si photovoltaic cells and on a ceramic substrate, are studied in this work. Test samples with electrodes of various sizes, suitable to study surface features in a wide measurement range, have been characterized by optical-confocal profilometry and by resistance measurements with dense data sampling. Quantitative measurements of these printed lines in terms of descriptors like the cross-section area and its variations along the segment, and of the top-profile roughness, scaling of roughness and fractal dimension, are presented and discussed either for photovoltaic cells and test structures. A good agreement between the resistance calculated from optical-based 3D morphology measurements and local resistance measurements on these electrodes is demonstrated.