Method of manufacturing a large-grain crystallized metal chalcogenide film, and a crystallized metal chalcogenide film prepared using the method

Abstract

The present invention also relates to a method for manufacturing a film of large-grain crystallized semi-conducting metal chalcogenide film notably of CZTS obtained from an aqueous or hydro-alcoholic colloidal solution according to the invention, said film being useful as an absorption layer deposited on a substrate applied in a solid photovoltaic device.

What is claimed is: 
     
         1 . A method for manufacturing a film of polycrystalline metal chalcogenide(s) with large crystalline grains of sizes at least equal to half the thickness of said film, by means of a colloidal solution consisting of: primary amorphous nanoparticles of metal chalcogenides of formula M-C dispersed in a hydro-alcoholic solvent,
 wherein:
 M represents one or several first metals, either identical or different, selected from the group consisting of Cu, Zn, and Sn, and 
 C represents one or several chalcogenide elements, either identical or different, selected from S and Se, 
 wherein said primary amorphous nanoparticles have a size of less than 30 nm, wherein the alcohol is a non-toxic alcohol having a boiling temperature below the boiling temperature of water, and wherein the hydro-alcoholic solution does not contain organic ligands, said film being deposited on one or more layered material(s) forming a substrate, said metal chalcogenide being of formula M-C wherein: 
 M represents Cu, Zn, and Sn, and 
 C represents one or more chalcogenide elements, either identical or different, selected from S and Se, wherein the following successive steps are carried out: 
 1) a layer of amorphous nanoparticles of metal chalcogenide(s) is deposited on said substrate from said aqueous, or hydro-alcoholic colloidal solution, and 
 2) heat treatment of said layer of metal chalcogenide(s) is carried out at a temperature of at least 300° C. in order to obtain densification of said layer of metal chalcogenide(s) and crystallization of the nanoparticles, over a thickness from 0.2 to 5 μm. 
   
     
     
         2 . The method according to  claim 1 , wherein, in step 1), said aqueous or hydro-alcoholic colloidal solution is sprayed with a carrier gas consisting of an oxygen-free gas, at atmospheric pressure and at a substrate temperature brought to at least 100° C., in order to form on said substrate, a layer of said colloidal solution with a thickness from 0.5 to 15 μm, and, wherein steps 1) and 2) are carried out in a vacuum chamber or filled with an oxygen-free gas. 
     
     
         3 . The method according to  claim 1 , wherein said substrate is a substrate intended to be covered with a type p semi-conductor absorption layer in a solid photovoltaic device, wherein said substrate consists of a glass or steel layer covered with a rear contact layer, consisting of a molybdenum layer, useful in a solid photovoltaic device of the substrate type. 
     
     
         4 . The method according to  claim 1 , wherein a film of crystallized metal chalcogenide(s) of Cu, Zn, and Sn with large crystalline grains with a size of at least half the thickness of the thickness of said film, continuously deposited on said substrate is obtained, said film having surface roughness with an arithmetic mean height of the peaks of Sa, according to the ISO 25178 standard, of less than half of the thickness e of the film, for a surface area of at least 20×20 μm 2 . 
     
     
         5 . A film of crystallized metal chalcogenide(s) manufactured according to the method of  claim 1 . 
     
     
         6 . The film according to  claim 5 , with large crystalline grains with a size of at least half the thickness of the thickness of said film, wherein said film has a surface roughness with an arithmetic mean height of the peaks of Sa, according to the ISO 25178 standard, of less than half of the thickness of the film, for a surface area of at least 20×20 μm 2 . 
     
     
         7 . The film according to  claim 5 , wherein the crystallized metal chalcogenide(s) consist of Cu 2 ZnSnS 4  in a Kesterite crystalline form, with a thickness of from 0.2 to 5 μm. 
     
     
         8 . A photovoltaic device comprising an absorption layer consisting of the film according to  claim 5  deposited on a substrate. 
     
     
         9 . The device according to  claim 8 , comprising successively stacked layers of:
 said substrate, wherein said substrate is made of sodium-lime glass, covered with a thin conductive layer of molybdenum being used as a rear electric contact layer,   said film of an absorbing material,   a buffer layer made of a layer made on the basis of an n-type semi-conductor, and   a conductive transparent layer consisting of a first layer of a not doped intrinsic ZnO layer, covered with a transparent conductive layer made of indium oxide doped with tin (ITO) or zinc oxide doped with aluminium (AZO), and a metal grid of a front face electric contact deposited on said transparent layer.   
     
     
         10 . The device according to  claim 9 , wherein said absorbing material comprises Cu 2 ZnSnS 4 . 
     
     
         11 . The device according to  claim 9 , wherein the n-type semi-conductor is selected from the group consisting of cadmium sulfide CdS, indium sulfide In 2 S 3 , and an oxysulfide alloy. 
     
     
         12 . The device according to  claim 11 , wherein the oxysulfide alloy is Zn(S, O, OH).