Method of making solar cell contacts

Abstract

Formulations and methods of making solar cells are disclosed. In general, the invention presents a solar cell contact made from a mixture wherein the mixture comprises a solids portion and an organics portion, wherein the solids portion comprises from about 85 to about 99 wt % of silver, and from about 1 to about 15 wt % of a glass component wherein the glass component comprises from about 15 to about 75 mol % PbO, and from about 5 to about 50 mol % SiO 2 , and preferably with no B 2 O 3 .

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.