Electrolyte composition

Abstract

The electrolyte composition is used in a method of depositing metals, in particular, onto substrates, especially solar cells. The electrolyte composition is particularly suitable for the deposition of metals, in particular silver, onto solar cells. The electrolyte composition is preferably free of cyanides and contains at least one metal, preferably silver, and an iminodisuccinate derivative, preferably a sodium or postassium iminodisuccinate.

1 . An electrolyte composition for deposition of metals onto a substrate, said electrolyte composition comprising:
 at least one metal ion, and   an iminodisuccinate derivative.   
     
     
         2 . The electrolyte composition according to  claim 1 , wherein the iminodisuccinate derivative comprises a species of the formula (I): 
       
         
           
           
               
               
           
         
         wherein R1, R2, R5 and R6 each represent, independently of each other, O, S or NH, and 
         wherein R3, R4, R7 and R8 each represent, independently of each other, OH, NH 2 , SH, O −  or S −   
       
     
     
         3 . The electrolyte composition according to  claim 1 , wherein the iminodisuccinate derivative is a salt. 
     
     
         4 . The electrolyte composition according to  claim 3 , wherein the salt is a sodium salt or a potassium salt. 
     
     
         5 . The electrolyte composition according to  claim 1 , wherein said at least one metal ion is selected from the group consisting of silver, calcium, magnesium, iron, chromium, cobalt, nickel, copper and aluminium ions. 
     
     
         6 . The electrolyte composition according to  claim 1 , wherein said at least one metal ion is a silver ion. 
     
     
         7 . The electrolyte composition according to  claim 1 , containing from 10 g/L to 60 g/L of said at least one metal ion. 
     
     
         8 . The electrolyte composition according to  claim 1 , wherein the iminodisuccinate derivative is an alkali metal iminodisuccinate. 
     
     
         9 . The electrolyte composition according to  claim 1 , wherein the iminodisuccinate derivative is a main complexing agent therein and is present in a concentration of 50 g/L to 250 g/L. 
     
     
         10 . The electrolyte composition according to  claim 9 , wherein the concentration of the iminodisuccinate derivative is from 150 g/L to 225 g/L. 
     
     
         11 . The electrolyte composition according to  claim 1 , containing another complexing agent besides the iminodisuccinate derivative and wherein the iminosuccinate derivative is contained therein in a concentration of 2 g/L to 40 g/L. 
     
     
         12 . The electrolyte composition according to  claim 11 , wherein the concentration of the iminodisuccinate derivative is from 5 g/L to 20 g/L. 
     
     
         13 . The electrolyte composition according to  claim 1 , further comprising a hydantoin in addition to the iminodisuccinate derivative, and wherein said hydantoin is contained therein in a concentration of 50 g/L to 250 g/L. 
     
     
         14 . The electrolyte composition according to  claim 13 , wherein said concentration of said hydantoin is from 100 g/L to 175 g/L. 
     
     
         15 . The electrolyte composition according to  claim 1 , further comprising a hydantoin in addition to the iminodisuccinate derivative, and wherein said hydantoin is 5,5-dimethyl hydantoin. 
     
     
         16 . The electrolyte composition according to  claim 1 , which is free of cyanides. 
     
     
         17 . The electrolyte composition according to  claim 1 , further comprising a citrate. 
     
     
         18 . The electrolyte according to  claim 17 , wherein said citrate is present in a concentration of 20 g/L to 75 g/L. 
     
     
         19 . The electrolyte according to  claim 17 , wherein said citrate is present in a concentration of 30 g/L to 50 g/L. 
     
     
         20 . The electrolyte composition according  claim 1 , having a pH of between 8 and 12. 
     
     
         21 . The electrolyte composition according to  claim 20 , wherein said pH is 9.5 to 11. 
     
     
         22 . A method of depositing metals on a substrate, said method comprising galvanically depositing said at least one metal from the said electrolyte composition as defined in  claim 1  onto the substrate. 
     
     
         23 . The method as defined in  claim 22 , wherein the substrate is a solar cell. 
     
     
         24 . A method of silvering a substrate, said method comprising the steps of:
 a) placing the substrate in an electrolyte composition according to  claim 1 ; and   b) applying a voltage between an anode and a cathode in electrical contact with the electrolyte composition, wherein the cathode is the substrate.