Effect of series resistance on metal-wrap-through multi-crystalline silicon solar cells

Metal-wrap-through (MWT) is a promising technique to improve the solar cell performance cost effectively because it can be easily integrated into the current production line with only two additional processing steps. Metal filling through the via-holes is a key to obtain low series resistances and good FFs. In this study, several screen printing process conditions were examined to find out an optimal filling state of the metal contacts. Various shapes of the filled metals in the via-holes were formed with different printing conditions, and the shape of the filled metal results in different series resistance values. Optimization of the printing conditions dramatically reduced the series resistance of the MWT cells. The maximum and minimum series resistance values of the cells obtained are 8.56 and 0.114 Ω cm2, respectively. As a result, we achieved an efficiency of 16.3% using the optimal printing condition on 156 mm×156 mm solar-grade multi-crystalline silicon wafer, which was 0.8% absolute higher than the baseline cell efficiency.