Patent ID: 8372679

Claim:
A process of forming a grid electrode on the front-side of a silicon wafer having a p-type region, an n-type region, a p-n junction and an ARC layer on said front-side, comprising the steps: (1) printing and drying a metal paste A having fire-through capability on the ARC layer, wherein the metal paste A is printed as thin parallel finger lines forming a bottom set of finger lines; (2) printing and drying a metal paste B over the bottom set of finger lines forming a top set of finger lines superimposing the bottom set of finger lines; (3) printing and drying a metal paste C forming two or more parallel busbars intersecting the finger lines at right angle; and (4) firing the silicon wafer; wherein the metal paste A comprises an organic vehicle and an inorganic content comprising (a1) at least one electrically conductive metal powder selected from the group consisting of silver, copper and nickel, and (a2) 0.5 to 8 wt. % of glass frit, wherein the metal paste B comprises an organic vehicle and an inorganic content comprising (b1) at least one electrically conductive metal powder selected from the group consisting of silver, copper and nickel, and (b2) 0 to 3 wt. % of glass frit, wherein the metal paste C comprises an organic vehicle and an inorganic content comprising (c1) at least one electrically conductive metal powder selected from the group consisting of silver, copper and nickel, and (c2) 0.2 to 3 wt. % of glass frit, wherein the inorganic content of said metal paste B as well as that of said paste C contains less glass frit plus optionally present other inorganic additives than the inorganic content of said metal paste A, and wherein steps (1) to (3) are performed in any order, provided that said step (1) is performed before said step (2).