Thick film silver paste and its use in the manufacture of semiconductor devices

Abstract

The present invention is directed to an electroconductive saver thick film paste composition comprising Ag, a glass frit and rhodium resinate, Cr 2 O 3 or a mixture thereof all dispersed in an organic medium. The present invention is further directed to an electrode formed from the paste composition and a semiconductor device and, in particular, a solar cell comprising such an electrode. The paste is particularly useful for forming a tabbing electrode.

What is claimed is: 
     
         1 . A thick film paste composition comprising:
 (a) 35-55 wt % Ag;   (b) 0.5-6 wt % glass frit, wherein said glass frit is a Pb-free bismuth-based oxide comprising 70-75-wt % Bi 2 O 3  11-15 wt % ZnO, 7-11 wt % B 2 O 3 , 0.3-3.5 wt % Al 2 O 3 , 2-7 wt % BaO and 0.5-3 wt % SiO 2 , wherein said oxide wt % are based on the total weight of said bismuth-based oxide;   (c) 0.08-0.4 wt % of a component selected from the group consisting of rhodium resinate, Cr 2 O 3  and mixtures thereof; and   (d) organic medium;   
       wherein said Ag, said glass frit and said component selected from the group consisting of rhodium resinate, Cr 2 O 3  and mixtures thereof are dispersed in said organic medium and wherein the wt % of said Ag, said glass frit and said component selected from the group consisting of rhodium resinate, Cr 2 O 3  and mixtures thereof are based on the total weight of said paste composition. 
     
     
         2 . A solar cell comprising an electrode formed from the paste composition of claim  9 , wherein said paste composition has been deposited on the back side of said solar cell and has been fired to remove the organic medium and form a tabbing electrode on the back side of said solar cell. 
     
     
         3 . A solar cell comprising an electrode formed from the paste composition comprising:
 (a) 35-55 wt % Ag;   (b) 0.5-6 wt % glass frit, wherein said glass frit is a Pb-free bismuth-based oxide consisting of 62-74 wt % Bi 2 O 3 , 6-15 wt % ZnO, 5-17 wt % B 2 O 3 , 0.1-8 wt % Al 2 O 3 , 1.5-12 wt % SiO 2  and 0-1.0 wt % CaO, wherein said oxide wt % are based on the total weight of said bismuth-based oxide;   (c) 0.08-0.4 wt % of a component selected from the group consisting of rhodium resinate, Cr 2 O 3  and mixtures thereof; and   (d) organic medium;   wherein said Ag, said glass frit and said component selected from the group consisting of rhodium resinate, Cr 2 O 3  and mixtures thereof are dispersed in said organic medium and wherein the wt % of said Ag, said glass frit and said component selected from the group consisting of rhodium resinate, Cr 2 O 3  and mixtures thereof are based on the total weight of said paste composition,   wherein said paste composition has been deposited on the back side of said solar cell and has been fired to remove the organic medium and form a tabbing electrode on the back side of said solar cell.