Optimization of lead- and cadmium-free front contact silver paste formulation to achieve high fill factors for industrial screen-printed Si solar cells

Screen-printed n(+)-p-p(+) solar cells were fabricated on Cz single crystalline Si material, with a 45 Omega/sq emitter and PECVD SiNx antireflective coating with a thickness of 700 angstrom, using different Ag pastes and commercial leaded reference paste (CN33-462. Ferro Corp.). Ag and Al contacts were co-fired using a mass-production line equipped with mesh belt conveyer furnace systems (Centrotherm thermal solution GmbH & Co. KG). The average results for single crystalline Si solar cells (156 cm(2)) are: I-sc = 5.043 A, V-oc = 0.621 V, R-s = 0.0087 Omega, R-sh = 15.3 Omega, FF = 0.773, and E-ff = 16.45%. R-sh and fill factor values of fabricated cells were slightly higher when compared with the commercial leaded Ag paste, although cells were fabricated by metallizing the lead-free silver pastes. For the lead-free Ag paste used in this study, the line pattern continuity is retained with improved edge definition in sharp contrast to that of reference Ag paste. Average value of R-s was also equivalent approximately to that of the leaded Ag paste. (C) 2009 Published by Elsevier B.V.