Evaluation of industrially relevant parameters for contact firing of screen printed front side silver contacts
To evaluate the impact of industrially relevant contact firing parameters on the contact resistance of screen printed front side silver contacts to the n-type emitter of crystalline silicon solar cells, contact firing is performed using design of experiments. Therefore, H-pattern aluminum back surface field solar cells processed on boron-doped Czochralski silicon are contact fired by rapid thermal firing in an industrial conveyor belt furnace as well as in a single wafer reactor. Current-voltage data as well as contact resistance values of 36 parameter sets are analyzed and evaluated regarding the significance of several contact firing parameters. Further aspects of the current transport mechanisms and performance of front side silver contacts in correlation with their microstructure are revealed. Comprehensive macroscopical characterization as well as microstructural analysis is done. An efficiency gain of > 0.1%abs only due to optimization of contact firing parameters is shown.