Solution-based fabrication of photovoltaic cell

Abstract

An ink for forming CIGS photovoltaic cell active layers is disclosed along with methods for making the ink, methods for making the active layers and a solar cell made with the active layer. The ink contains a mixture of nanoparticles of elements of groups IB, IIIA and (optionally) VIA. The particles are in a desired particle size range of between about 1 nm and about 500 nm in diameter, where a majority of the mass of the particles comprises particles ranging in size from no more than about 40% above or below an average particle size or, if the average particle size is less than about 5 nanometers, from no more than about 2 nanometers above or below the average particle size. The use of such ink avoids the need to expose the material to an H 2 Se gas during the construction of a photovoltaic cell and allows more uniform melting during film annealing, more uniform intermixing of nanoparticles, and allows higher quality absorber films to be formed.

1 . A method for fabricating a liquid containing intermixed nanoparticulate elements of groups IB and IIIA and optionally VIA, comprising the steps of:
 forming elemental non-oxide metal nanoparticles containing elements from group IB; and   forming elemental non-oxide metal nanoparticles from group IIIA; and   optionally forming elemental non-oxide nanoparticles from group VIA;   intermixing the elemental non-oxide nanoparticles from groups IB and IIIA; and   optionally VIA, wherein the particles are in a desired particle size range of between about 0.1 nm and about 500 nm in diameter, wherein, for each element metal, a majority of the mass of the elemental metal nanoparticles range in size from no more than about 40% above or below an average particle size, or, if the average particle size is less than about 5 nanometers, from no more than about 2 nanometers above or below the average particle size; and   mixing the particles to form a liquid that serves as an ink.   
     
     
         2 . The method of  claim 1  wherein the group IB element is copper (Cu), the group IIIA element is indium and optionally includes gallium) and the group VIA element is selenium (Se) or sulfur (S) and a stoichiometric ratio of the Cu, In and Se or S in the liquid is approximately CuIn 1-x Ga x (S or Se) 2 , where x is between 0 and 1. 
     
     
         3 . The method of  claim 1  further comprising coating the elemental non-oxide metal nanoparticles with a surfactant or polymer. 
     
     
         4 . The method of  claim 1  wherein forming the elemental non-oxide metal nanoparticles includes condensing a metal vapor. 
     
     
         5 . The method of  claim 4  wherein the metal vapor includes Cu and/or In, and optionally Se. 
     
     
         6 . The method of  claim 3  wherein forming the elemental non-oxide metal nanoparticles includes laser ablation, mechanical milling, grinding, nucleation from vapor, exploding wires by electrical current surge, thermal decomposition of organometallic compounds, sonolysis, pulse radiolysis, electrochemical reduction or chemical reduction. 
     
     
         7 . The method of  claim 1  wherein the liquid is formed by mixture with water. 
     
     
         8 . The method of  claim 1  wherein the liquid is formed by mixture with organic solvent. 
     
     
         9 . The method of  claim 1 , further comprising adding a capping agent to the elemental nanoparticles, wherein the capping agent selected from the group of phosphines, amines, alcohols, thiols, ethers, water and glycols, trioctylphosphine oxide, trioctylphosphine, triphenylphosphine, pyridine, methanol, ethanol, propanol, butanol, ethane thiol, tetrahydrofuran, ethers, ammonia, methyl amine, ethylamine, ethylenediamine, and acetonitrile. 
     
     
         10 . The method of  claim 1 , further comprising adding a binder to the elemental nanoparticles. 
     
     
         11 . The method of  claim 1 , further comprising adding a fluxing agent to the elemental nanoparticles. 
     
     
         12 . The method of  claim 1 , further comprising adding one or more surfactants, polymers, dispersants, binders, modifiers, detergents or additives to the elemental nanoparticles. 
     
     
         13 . A method for fabricating a liquid containing intermixed elements of groups IB and IIIA, and optionally VIA, comprising the steps of:
 forming non-oxide quantum nanoparticles containing elements from group IB; and   forming non-oxide quantum nanoparticles containing elements from group IIIA; and   optionally forming non-oxide quantum nanoparticles containing elements from group VIA;   intermixing the non-oxide quantum nanoparticles from groups IB and IIIA and optionally VIA wherein the non-oxide quantum nanoparticles are in a desired particle size range of between about 0.1 nm and about 10 nm in diameter, wherein, for each element, a majority of the mass of the non-oxide quantum nanoparticles range in size from no more than about 40% above or below an average particle size, or, if the average particle size is less than about 5 nanometers, from no more than about 2 nanometers above or below the average particle size; and   mixing the non-oxide nanoparticles to form a liquid that serves as an ink.   
     
     
         14 . The method of  claim 13  wherein the non-oxide quantum nanoparticles are quantum dots, quantum wires, quantum wells, or quantum rods. 
     
     
         15 . The method of  claim 13  wherein the group IB element is copper (Cu), the group IIIA element is indium and optionally includes gallium) and the group VIA element is selenium (Se) or sulfur (S) and a stoichiometric ratio of the Cu, In and Se or S in the liquid is approximately CuIn 1-x Ga x (S or Se) 2 , where x is between 0 and 1. 
     
     
         16 . The method of  claim 13  wherein forming non-oxide quantum nanoparticles includes a reaction of the type:
   CuCl+InCl 3 (+GaI 3 )+TOPSe(S)+TOPO→Cu(Ga, In)Se(S) 2 .   
     
     
         17 . The method of  claim 13  wherein forming a mixture of non-oxide quantum nanoparticles includes performing a reaction of the type:
   CuCl (or CuI or CuCl 2 )+InCl 3  (or InI 3  or GaI 3 )+Na 2 Se+ligand/capping agent→Cu(Ga,In)Se 2 .   
     
     
         18 . The method of  claim 13  wherein the ligand/capping agent is selected from the group of phosphines, amines, alcohols, thiols, ethers, water and glycols, trioctylphosphine oxide, trioctylphosphine, triphenylphosphine, pyridine, methanol, ethanol, propanol, butanol, ethane thiol, tetrahydrofuran, ethers, ammonia, methyl amine, ethylamine, ethylenediamine, and acetonitrile. 
     
     
         19 . The method of  claim 13  wherein forming a mixture of non-oxide quantum nanoparticles includes reacting a single-source precursor to form particles of IB-IIIA-VIA material. 
     
     
         20 . The method of  claim 19  wherein the single-source precursor is (PPh 3 ) 2 CuIn(SEt) 4  or (PPh 3 ) 2 CuIn(SePh) 4 . 
     
     
         21 - 74 . (canceled)