Finger Metallization Using Pattern Transfer Printing Technology for c-Si Solar Cell

Front metallization of crystalline silicon solar cells requires smaller finger lines in order to collect the generated current from the active area efficiently. Pattern transfer printing (PTP) technology enables finger widths down to 20 μm and aspect ratios above 0.6 using thick film silver paste. This work investigates the influence of PTP process parameters, i.e., laser power and trench geometry, on the finger geometry and the print quality. Silver fingers obtained from four different trench geometries were analyzed and the electrical parameters of corresponding printed solar cells were compared with standard screen-printed solar cells. We observed a strong dependence of the finger aspect ratio and the amount of debris on the laser power that was used during the transfer process. Each trench geometry requires a different laser power, which is related to the ratio between the circumference and the horizontal interface of the trench. Despite a modest FF loss due to higher series resistance, a significant gain in Jsc and a smaller gain in Voc increased the cell efficiency by 0.12%abs for the best group of PTP-printed cells compared with the reference screen-printed cells. Importantly, the amount of silver required was reduced by 54% compared with the screen-printed reference.