Conductive silver paste for a metal-wrap-through silicon solar cell
View Patent ↗A conductive silver via paste comprising particulate conductive silver, a vanadium-phosphorus-oxide and an organic vehicle is particularly useful in providing the metallization of the holes in the silicon wafers of MWT solar cells. The result is a metallic electrically conductive via between the collector lines on the front side and the emitter electrode on the back-side of the solar cell. The paste can also be used to form the collector lines on the front-side of the solar cell and the emitter electrode on the back-side of the solar cell. Also disclosed are metal-wrap-through silicon solar cells comprising the fired conductive silver paste.
1. A conductive silver paste comprising:
(a) 85-95 wt % silver;
(b) 0.2-5.5 wt % vanadium-phosphorus-oxide consisting of 80-94 wt % and 6-20 wt % P 2 O 5 , wherein the wt % of the V 2 O 5 and P 2 O 5 are based on the total weight of said vanadium-phosphorus-oxide; and
(c) 5-20 wt % organic vehicle, wherein said silver and said vanadium-phosphorus-oxide are dispersed in said organic vehicle and wherein the wt % of the silver, the vanadium-phosphorus-oxide and the organic vehicle are based on the total weight of the conductive silver paste.
2. The conductive silver paste of claim 1 , wherein said silver is in the form of spherical silver particles.
3. The conductive silver paste of claim 2 , said spherical silver particles having a d 50 of from 1.7 to 1.9 μm and a d 10 ≧1 μm and a d 90 ≦3.8 μm.
4. The conductive silver paste of claim 1 , wherein said silver is in the form of irregular particles having a d 50 of from 5.4 to 11.0 μm and a d 90 of from 9.6 to 21.7 μm.
5. The conductive silver paste of claim 1 , said vanadium-phosphorus-oxide consisting of 82-88 wt % V 2 O 5 and 12-18 wt % P 2 O 5 , wherein the wt % are based on the total weight of said vanadium-phosphorus-oxide.
6. A metal-wrap-through silicon solar cell with an n-type or a p-type silicon base comprising the fired conductive silver paste of claim 5 .
7. The conductive silver paste of claim 1 , said vanadium-phosphorus-oxide consisting of 90-94 wt % V 2 O 5 and 6-10 wt % P 2 O 5 , wherein the wt % are based on the total weight of said vanadium-phosphorus-oxide.
8. A metal-wrap-through silicon solar cell with an n-type or a p-type silicon base comprising the fired conductive silver paste of claim 7 .
9. The conductive silver paste of claim 1 , said conductive silver paste comprising 85-92 wt % silver and 0.5 to 2 wt % vanadium-phosphorus-oxide, based on the total weight of said conductive silver paste.
10. A metal-wrap-through silicon solar cell with an n-type or a p-type silicon base comprising the fired conductive silver paste of claim 9 .
11. The conductive silver paste of claim 1 , said conductive silver paste comprising 88-92 wt % silver and 4 to 5 wt % vanadium-phosphorus-oxide, based on the total weight of said conductive silver paste.
12. A metal-wrap-through silicon solar cell with an n-type or a p-type silicon base comprising the fired conductive silver paste of claim 11 .
13. The conductive silver paste of claim 1 , said conductive silver paste further comprising a sintering inhibitant.
14. The conductive silver paste of claim 1 , said conductive silver paste comprising:
0.1 to 1 wt % sintering inhibitant titanium resinate, based on the total weight of the conductive silver paste.
15. The conductive silver paste of claim 1 , said conductive silver paste comprising 0.1 to 1 wt % sintering inhibitant titanium dioxide, based on the total weight of the conductive silver paste.
16. A metal-wrap-through silicon solar cell with an n-type or a p-type silicon base comprising the fired conductive silver paste of claim 1 .
17. A conductive silver paste further comprising:
(a) 85-95 wt % silver;
(b) 0.2-5.5 wt % vanadium-phosphorus-oxide consisting of 80-94 wt % V 2 O 5 6-20 wt % P 2 O 5 , and 0.1-1 wt % TiO 2 , wherein the wt % of the V 2 O 5 , P 2 O 5 and TiO 2 are based on the total weight of said vanadium-phosphorus-oxide; and
(c) 5-20 wt % organic vehicle, wherein said silver and said vanadium-phosphorus-oxide are dispersed in said organic vehicle and wherein the wt % of the silver, the vanadium-phosphorus-oxide and the organic vehicle are based on the total weight of the conductive silver paste.
18. A metal-wrap-through silicon solar cell with an n-type or a p-type silicon base comprising the fired conductive silver paste of claim 17 .
19. The conductive silver paste of claim 17 , said conductive silver paste further comprising a sintering inhibitant.