Method of making solar cell contacts

1 . A solar cell contact made from a mixture wherein the mixture comprises:

a. a solids portion and

b. an organics portion,

c. wherein the solids portion comprises

i. from about 85 to about 99 wt % of a silver component, and

ii. from about 1 to about 15 wt % of a glass component

iii. wherein the glass component comprises

a. from about 15 to about 75 mol % PbO,

b. from about 5 to about 50 mol % SiO 2 , and

c. no B 2 O 3 .

2 . The solar cell contact of claim 1 wherein the weight ratio of the solids portion to the organics portion is from about 20:1 to about 1:20.

3 . The solar cell contact of claim 1 wherein the glass component further comprises about 1 to about 30 mol % Bi 2 O 3 .

4 . The solar cell contact of claim 1 wherein the glass component further comprises about 0.1 to about 15 mol % Al 2 O 3 .

5 . The solar cell contact of claim 4 wherein the glass component further comprises about 0.1 to about 10 mol % Ta 2 O 5 .

6 . The solar cell contact of claim 5 wherein the glass component further comprises about 0.1 to about 10 mol % ZrO 2 .

7 . The solar cell contact of claim 6 wherein the glass component further comprises about 0.1 to about 8 mol % P 2 O 5 .

8 . The solar cell contact of claim 1 wherein the glass component further comprises about 0.1 to about 15 mol % HfO 2 +In 2 O 3 +Ga 2 O 3 .

9 . The solar cell contact of claim 1 wherein the glass component further comprises about 0.1 to about 10 mol % Y 2 O 3 +Yb 2 O 3 .

10 . The solar cell contact of claim 4 wherein the glass component further comprises about 0.1 to about 15 mol % HfO 2 .

11 . The solar cell contact of claim 4 wherein the glass component further comprises about 0.1 to about 10 mol % ZrO 2 .

12 . The solar cell contact of claim 11 wherein the glass component further comprises about 0.1 to about 8 mol % P 2 O 5 .

13 . The solar cell contact of claim 4 wherein the glass component further comprises about 0.1 to about 3 mol % B 2 O 3 .

14 . The solar cell contact of claim 13 wherein the glass component further comprises about 0.1 to about 10 mol % Sb 2 O 5 .

15 . The solar cell contact of claim 14 wherein the glass component further comprises about 0.1 to about 10 mol % ZrO 2 .

16 . The solar cell contact of claim 4 wherein the glass component comprises:

a. about 26 to about 34 mol % PbO,

b. about 27 to about 33 mol % SiO 2 ,

c. about 5 to about 11 mol % A1 2 O 3 ,

d. about 0.1 to about 2 mol % Ta 2 O 5 ,

e. and further comprises about 27 to about 33 mol % ZnO.

17 . The solar cell contact of claim 4 wherein the glass component further comprises about 0.1 to about 3 mol % MoO 3 .

18 . The solar cell contact of claim 1 wherein the solids portion further comprises a crystalline additive selected from the group consisting of Bi 2 O 3 , Sb 2 O 3 , In 2 O 3 , Ga 2 O 3 , SnO, ZnO, Pb 3 O 4 , PbO, SiO 2 , ZrO 2 , Al 2 O 3 , B 2 O 3 , Ta 2 O 5 , 4PbO.SiO 2 , 3PbO.SiO 2 , 2PbO.SiO 2 , 3PbO.2SiO 2 , PbO.SiO 2 , ZnO.SiO 2 , and ZrO 2 .SiO 2 , and reaction products thereof and combinations thereof.

19 . The solar cell contact of claim 1 wherein the solids portion comprises about 60 to about 95 wt % of flaked silver or powdered silver, and about 0.1 to about 20 wt % of colloidal silver.

20 . The solar cell contact of claim 1 wherein the silver component comprises silver selected from the group consisting of present as flakes, powder, or colloidal particles of silver, wherein the solids portion further comprises phosphorus, at least a portion of which is present as a coating on at least a portion of the silver flakes, powder or colloidal particles.

21 . The solar cell contact of claim 1 wherein the silver component contains a compound selected from the group consisting of an oxide of silver or a salt of silver, or combinations thereof.

22 . The solar cell contact of claim 1 wherein the solids portion further comprises about 0.5 to about 25 wt % of a first metal selected from the group consisting of Pb, Bi, Zn, In, Ga, and Sb and alloys thereof with at least one second metal.

23 . The solar cell contact of claim 22 wherein the at least one second metal is silver.

24 . The solar cell contact of claim 22 wherein the first metal is zinc.

25 . The solar cell contact of claim 24 wherein the at least one second metal is silver.

26 . The solar cell contact of claim 1 wherein the glass component comprises a first glass composition and a second glass composition, wherein

a. the first glass composition comprises:

i. about 26 to about 34 mol % PbO,

ii. about 27 to about 33 mol % SiO 2 ,

iii. about 20 to about 33 mol % ZnO, and

iv. about 5 to about 11 mol % Al 2 O 3 ,

b. the second glass composition comprises:

i. about 58 to about 70 mol % PbO and

ii. about 5 to about 50 mol % SiO 2 ,

c. wherein the weight ratio between the first and second glass compositions is from about 1:20 to about 20:1.

27 . The solar cell contact of claim 26 wherein the weight ratio between the first and second glass compositions is from about 1:3 to about 3:1.

28 . A process for making a solar cell contact comprising:

a. applying a silver-containing paste on an antireflective silicon wafer and

b. firing the paste to form a coating,

c. wherein the paste comprises a solids portion and an organics portion, the solids portion comprising:

i. about 85 to about 99 wt % silver, and

ii. about 1 to about 15 wt % of a glass component;

d. wherein the glass component comprises

i. about 15% to 75 mol % PbO,

ii. about 5% to about 50 mol % SiO 2 , and

iii. less than about 3 mol % B 2 O 3 .

29 . The process of claim 28 wherein the paste is fired at a furnace set temperature of about 650° C. to about 1000° C. for about 1 second to about 5 minutes.