Persulfate bath and method for chemically depositing a layer

Abstract

A chemical bath for depositing a layer made from at least metal and sulphur is described. A method for depositing such a layer is also presented. The bath comprises, in solution: a metal salt comprising a metal chosen from at least one of the elements from groups BIB and MA of the periodic table; and a sulphur precursor. The bath further comprises a persulfate compound.

1 . A chemical bath for depositing a layer based on at least metal and sulfur, the chemical bath comprising, in solution:
 a metal salt comprising a metal selected from among at least one of the elements of groups IIB and IIIA of the periodic table; and   a sulfur precursor;   wherein the chemical bath further comprises a persulfate compound.   
     
     
         2 . The chemical bath according to  claim 1 , wherein the persulfate compound is from a group consisting of ammonium persulfate of chemical formula (NH 4 ) 2 S 2 O 8 , sodium persulfate of chemical formula Na 2 S 2 O 8 , and potassium persulfate of chemical formula K 2 S 2 O 8 . 
     
     
         3 . The chemical bath according to  claim 1 , wherein a concentration between 10 −5  mol/L and 10 mol/L of persulfate is provided in the chemical bath, for a concentration between 0.05 mol/L and 1 mol/L of sulfur precursor. 
     
     
         4 . The chemical bath according to  claim 3 , wherein the metal salt is in a solution selected from among: zinc sulfate, zinc acetate, and zinc chloride, at a concentration between 0.01 mol/L and 1 mol/L. 
     
     
         5 . The chemical bath according to  claim 3 , further comprising an ammonia solution at a concentration between 0.1 mol/L and 10 mol/L. 
     
     
         6 . The chemical bath according to  claim 1 , wherein the sulfur precursor is in a solution of thiourea CS(NH 2 ) 2 . 
     
     
         7 . The chemical bath according to  claim 1 , wherein the metal is an element from column IIB. 
     
     
         8 . The chemical bath according to  claim 7 , wherein the metal is zinc. 
     
     
         9 . A method for chemically depositing a layer based on at least metal and sulfur, the method comprising:
 depositing, in a solution in a chemical bath, a metal salt comprising a metal selected from among at least one of the elements of groups IIB and IIIA of the periodic table; and   depositing, in the solution in the chemical bath, a sulfur precursor;   wherein a persulfate compound is further provided in said chemical bath.   
     
     
         10 . The method of  claim 9 , wherein the layer is based on a metal sulfide. 
     
     
         11 . The method of  claim 9 , wherein the layer is based on a metal oxysulfide. 
     
     
         12 . The method of  claim 9 , wherein the temperature of the chemical bath during deposition is between 40° C. and 100° C. 
     
     
         13 . The method of  claim 9 , wherein the layer based on metal and sulfur is deposited on a layer having photovoltaic properties, said layer having photovoltaic properties forming an absorber of a thin-film solar cell. 
     
     
         14 . The method of  claim 13 , wherein the absorber is based on a chalcopyrite compound among Cu(In,Ga)(S,Se) 2 , Cu 2 (Zn, Sn)(S, Se) 4 , and their derivatives.