Thick film paste containing bismuth-tellurium-oxide and its use in the manufacture of semiconductor devices
View Patent ↗The present invention is directed to an electroconductive thick film paste composition comprising Ag and a Pb-free bismuth-tellurium-oxide both 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 present invention is also directed to the bismuth-tellurium oxide that is a component of thick film pastes.
1. A thick film paste composition comprising:
(a) 35-55 wt % Ag;
(b) 0.5-5 wt % Pb-free bismuth-tellurium-oxide consisting of 22-42 wt % Bi 2 O 3 , 58-78 wt % TeO 2 , 0.1-7 wt % Li 2 O and 0.1-4 wt % TiO 2 , wherein the wt % of Bi 2 O 3 , TeO 2 , Li 2 O and TiO 2 are based on the total weight of said bismuth-tellurium oxide; and
(c) an organic medium;
wherein said Ag, and said bismuth-tellurium-oxide are dispersed in said organic medium and wherein said wt % of said Ag and said bismuth-tellurium-oxide are based on the total weight of said paste composition.
2. The paste composition of claim 1 , said paste composition comprising 38-52 wt % Ag and 1-3.5 wt % bismuth-tellurium-oxide, wherein said wt % are based on the total weight of said paste composition.
3. The paste composition of claim 1 , said bismuth-tellurium-oxide consisting of 22-42 wt % Bi 2 O 3 , 58-78 wt % TeO 2 , 0.9-5 wt % Li 2 O and 0.3-2 wt % TiO 2 , based on the total weight of said bismuth-tellurium oxide.
4. The paste composition of claim 1 , said paste composition comprising less than 70 wt % of inorganic components.
5. The paste composition of claim 1 , further comprising 0.5-5 wt % of an inorganic additive selected from the group consisting of Bi 2 O 3 , TiO 2 , Al 2 O 3 , B 2 O 3 , SnO 2 , Sb 2 O 5 , Cr 2 O 3 , Fe 2 O 3 , ZnO, CuO, Cu 2 O, MnO 2 , Co 2 O 3 , NiO, RuO 2 , a metal that can generate a listed metal oxide during firing, a metal compound that can generate a listed metal oxide during firing, and mixtures thereof, wherein said wt % is based on the total weight of said paste composition.
6. The paste composition of claim 5 , said paste composition comprising less than 70 wt % of inorganic components comprising said Ag powder, said Bi—Te—O powder and any of said inorganic additives, wherein said wt % is based on the total weight of said paste composition.
7. A semiconductor device comprising an electrode formed from the paste composition of any of claims 1 , 2 , 3 , 4 , 5 or 6 , wherein said paste composition has been fired to remove the organic medium and form said electrode.
8. A solar cell comprising an electrode formed from the paste composition of any of claims 1 , 2 , 3 , 4 , 5 or 6 , wherein said paste composition has been fired to remove the organic medium and form said electrode.
9. The solar cell of claim 8 , wherein said electrode is a tabbing electrode on the back side of said solar cell.
10. A thick film paste composition comprising:
(a) 35-55 wt % Ag;
(b) 0.5-5 wt % Pb-free bismuth-tellurium-oxide consisting of 22-42 wt % Bi 2 O 3 , 58-78 wt % TeO 2 , 0.1-7 wt % Li 2 O, 0.01-4 wt % TiO 2 , 0.1-8 wt % B 2 O 3 , 0.1-3 wt % ZnO and 0.3-2 wt % P 2 O 5 , wherein the wt % of Bi 2 O 3 , TeO 2 , Li 2 O, TiO 2 , B 2 O 3 , ZnO and P 2 O 5 are based on the total weight of said bismuth-tellurium oxide; and
(c) an organic medium;
wherein said Ag and said bismuth-tellurium-oxide are dispersed in said organic medium and wherein said wt % of said Ag and said bismuth-tellurium-oxide are based on the total weight of said paste composition.
11. The paste composition of claim 5 , said bismuth-tellurium-oxide consisting of 22-42 wt % Bi 2 O 3 , 58-78 wt % TeO 2 , 0.9-5 wt % Li 2 O, 0.3-2 wt % TiO 2 , 0.9-6 wt % B 2 O 3 , 0.1-2 wt % ZnO and 0.3-1 wt % P 2 O 5 , based on the total weight of said bismuth-tellurium oxide.
12. The paste composition of claim 10 , further comprising 0.5-5 wt % of an inorganic additive selected from the group consisting of Bi 2 O 3 , TiO 2 , Al 2 O 3 , B 2 O 3 , SnO 2 , Sb 2 O 5 , Cr 2 O 3 , Fe 2 O 3 , ZnO, CuO, Cu 2 O, MnO 2 , Co 2 O 3 , NiO, RuO 2 , a metal that can generate a listed metal oxide during firing, a metal compound that can generate a listed metal oxide during firing, and mixtures thereof, wherein said wt % is based on the total weight of said paste composition.
13. The paste composition of claim 12 , said paste composition comprising less than 70 wt % of inorganic components comprising said Ag powder, said Bi—Te—O powder and any of said inorganic additives, wherein said wt % is based on the total weight of said paste composition.
14. A semiconductor device comprising an electrode formed from the paste composition of any of claims 10 , 11 , 12 or 13 , wherein said paste composition has been fired to remove the organic medium and form said electrode.
15. A solar cell comprising an electrode formed from the paste composition of any of claims 10 , 11 , 12 or 13 , wherein said paste composition has been fired to remove the organic medium and form said electrode.
16. The solar cell of claim 15 , wherein said electrode is a tabbing electrode on the back side of said solar cell.