Atypical kesterite compositions

Abstract

This invention relates to processes for making kesterite compositions with atypical Cu:Zn:Sn:S ratios and/or kesterite compositions with unusually small coherent domain sizes. This invention also relates to these kesterite compositions and their use in preparing CZTS films.

1 - 4 . (canceled) 
     
     
         5 . A composition comprising a compound having a kesterite structure,
 wherein the coherent domain size of the kesterite is 2-30 nm.   
     
     
         6 . The composition of  claim 5 , further comprising one or more copper-, tin-, or zinc-containing compounds selected from the group consisting of binary copper chalcogenides, binary copper oxides, binary tin chalcogenides, binary tin oxides, binary zinc chalcogenides, ZnO, and CTS—Se. 
     
     
         7 . The composition of  claim 6 , wherein the molar ratio of copper to zinc to tin is about 2:1:1. 
     
     
         8 . The composition of  claim 6 , wherein the molar ratio of copper to (zinc plus tin) is less than one, and the molar ratio of zinc to tin is greater than one. 
     
     
         9 . The composition of  claim 5 , wherein the Cu/Zn ratio of the kesterite is greater than about 3.1. 
     
     
         10 . A process comprising: 
       a) preparing an ink comprising:
 i) a copper source selected from the group consisting of copper complexes of nitrogen-, oxygen-, sulfur-, and selenium-based organic ligands, and mixtures thereof; 
 ii) a tin source selected from the group consisting of tin complexes of nitrogen-, oxygen-, carbon-, sulfur-, and selenium-based organic ligands, tin hydrides, tin sulfides, tin selenides, and mixtures thereof; 
 iii) a zinc source selected from the group consisting of zinc complexes of nitrogen-, oxygen-, sulfur-, and selenium-based organic ligands, and mixtures thereof; 
 iv) an elemental chalcogen selected from the group consisting of: elemental S, elemental selenium, and mixtures thereof; 
 v) a solvent; 
 iv) optionally, a chalcogen compound selected from the group consisting of: R 1 S—Z, R 1 Se—Z and mixtures thereof, with each Z independently selected from the group consisting of: H and SiR 5   3 ; wherein each R 1  and R 5  is independently selected from the group consisting of: hydrocarbyl and O-, N-, S-, halogen- and tri(hydrocarbyl)silyl-substituted hydrocarbyl; 
 
       b) heating the ink to a temperature of 150-300° C.; 
       b) disposing the ink onto a substrate; and 
       c) heating the substrate and ink disposed thereon to a temperature of 80-350° C. to form a coated substrate comprising CZTS—Se kesterite. 
     
     
         11 . The process of  claim 10 , wherein the ratio of the total number of moles of the chalcogen compound, the sulfur- and selenium-based organic ligands, and the copper-, tin- and zinc-sulfides and selenides to the total number of moles of the copper, tin and zinc complexes is at least about 1. 
     
     
         12 . The process of  claim 11 , wherein the ink comprises a chalcogen compound. 
     
     
         13 . The process of  claim 10 , wherein the elemental chalcogen comprises sulfur and the molar ratio of elemental chalcogen is about 0.2 to about 5 relative to the tin source. 
     
     
         14 . The process of  claim 10 , wherein the nitrogen-, oxygen-, carbon-, sulfur- and selenium-based organic ligands are selected from the group consisting of:
 amidos; alkoxides; acetylacetonates; carboxylates; hydrocarbyls; O-, N-, S-, halogen-, and tri(hydrocarbyl)silyl-substituted hydrocarbyls; thio- and selenolates; thio-, seleno-, and dithiocarboxylates; dithio-, diseleno-, and thioselenocarbamates; and dithioxanthogenates.   
     
     
         15 . The process of  claim 10 , wherein the process is conducted at atmospheric pressure and the boiling point of the solvent is greater than about 150° C. at atmospheric pressure. 
     
     
         16 . The process of  claim 10 , wherein the solvent is selected from the group consisting of heteroaromatics, amines, and mixtures thereof.