Solution processing of kesterite semiconductors

Abstract

Methods for depositing a kesterite film comprising a compound of the formula: Cu 2−x Zn 1+y Sn(S 1−z Se z ) 4+q , wherein 0≦x≦1; 0≦y≦1; 0≦z≦1; −1≦q≦1, generally include contacting a hydrazine-based solvent, a source of Cu, a source of Sn, a source of Zn carboxylate, a source of at least one of S and Se, under conditions sufficient to form a solution substantially free of solid particles; applying the solution onto a substrate to form a thin layer; and annealing the thin layer at a temperature, pressure, and length of time sufficient to form the kesterite film. Also disclosed are hydrazine-based precursor solutions for forming a kesterite film and a photovoltaic device including the kesterite film formed by the above method.

What is claimed is: 
     
         1 . A photovoltaic device, comprising:
 a top electrode having transparent conductive material;   an n-type semiconducting layer;   a kesterite film comprising a compound of the formula: Cu 2−x Zn 1+y Sn(S 1−z Se z ) 4+q , wherein 0≦x≦1; 0≦y≦1; 0≦z≦1; −1≦q≦1, and formed by contacting a hydrazine-based solvent, a source of Cu, a source of Sn, a source of Zn carboxylate, a source of at least one of S and Se, under conditions sufficient to form a solution free of solid particles, wherein the conditions consist of dispersing the source of the zinc carboxylate in a portion of the hydrazine-based solvent to form a first slurry of zinc carboxylate particles, and dispersing the source of Sn in a portion of the hydrazine-based solvent to form an initial Sn solution, and mixing the first slurry and the initial Sn solution to dissolve the zinc carboxylate particles and form the solution free of solid particles, wherein the source of Cu, and the source of at least one of S and Se are added to the initial Sn solution or to the solution free of solid particles; applying the solution free of solid particles onto a substrate to form a thin layer having a thickness of about 0.2 microns to about 5 microns; and annealing the thin layer at a temperature, pressure, and length of time sufficient to form the kesterite film; and   the substrate having an electrically conductive surface.   
     
     
         2 . The photovoltaic device of  claim 1 , wherein:
 said substrate is coated with a molybdenum layer and is selected from the group consisting of glass, plastic, polymer, ceramic, and aluminum foil;   said n-type semiconducting layer has at least one of: ZnS, CdS, InS, oxides thereof, and selenides thereof;   said transparent conductive material is selected from the group consisting of: doped ZnO, Indium-tin oxide, doped tin oxide, and carbon nanotubes.   
     
     
         3 . The photovoltaic device of  claim 1 , comprising:
 a plurality of electrically interconnected photovoltaic devices forming a photovoltaic module.