PROJECT TITLE :

Contacting Interdigitated Back-Contact Solar Cells With Four Busbars for Precise Current–Voltage Measurements Under Standard Testing Conditions

ABSTRACT:

Increasing the area of interdigitated back-contact (IBC) solar cells featuring a busbar contact geometry requires the use of longer fingers. The finger resistance can, so, be increased if the thickness of the metallization is kept constant. In order to keep up a skinny metallization, it is helpful to extend the number of busbars per contact. But, using more than one busbar for every polarity implies an uneven contact geometry. As a consequence, under operation, the busbars of the identical polarity carry different currents. Because of voltage drops over unavoidable electrical resistances, this might result in important potential variations between these busbars. Since current–voltage characteristics are usually measured using separate sense contacts for the voltage measurement, the position and range of these contacts may considerably affect the form of the ensuing current–voltage characteristic and, so, the fill issue. By means of simulations with the circuit simulator LTSpice, we show that a permanent contacting with soldered tabs permits for an accurate determination of the fill factor. A chuck used for temporary contacting ought to feature a minimum of one sense contact per busbar and pin contacting resistances below thirty mΩ in order to keep the fill factor error below 0.5% absolute.