New printing pattern design and processing of MWT solar cells for pilot-line

We present a feasible process for metal-wrap-through (MWT) solar cell with two-stage sintering. The main advantage of MWT solar cell is its larger illuminated area compare to those of conventional cells. Base on this, we design a new front side printing pattern which can optimize the current through each hole to achieve low series resistance and high fill factor. Besides, n layer is only located on the front surface owing to thin silicon nitride coating on the rear and via sidewall; so we don´t need to make isolation on edge and rear bus bar which would decrease fill factor and short-circuit current density. After the front Ag finger and rear Al metallization, we fill via holes and rear bus bar with the finger Ag paste. The deviation of cell efficiency is very large due to unstable non-firing via holes and bus bar resistivity but it can be improved dramatically from 1.2% to 0.1% after burning organic out by a controlling 400°C IR furnaces. The best cell efficiency is 16.6% on 270μm thick multi-crystalline silicon of 125×125 mm² and the average efficiency is 16.5%.