Solution-based fabrication of photovoltaic cell
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 liquid ink comprising:
forming non-oxide metal nanoparticles containing elements from group IB;
forming non-oxide metal nanoparticles from group IIIA; and
adding one or more liquid metals containing one or more elements of group IIIA;
intermixing the non-oxide nanoparticles from groups IB and IIIA and one or more liquid metals from group IIIA, 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 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 forming the non-oxide metal nanoparticles comprises using one or more methods selected from the group consisting of: laser ablation, mechanical milling, grinding, nucleation from vapor, exploding wires by electrical current surge, thermal decomposition of organometallic compounds, sonolysis, pulse radiolysis, electrochemical reduction, and chemical reduction.
3. The method of claim 1 further comprising adding group VIA material to the liquid ink.
4. The method of claim 1 , wherein a Group VIA element is introduced into the liquid ink by adding particles containing one or more Group VIA element.
5. The method of claim 1 , wherein a Group VIA element is introduced by heating the ink in a Group VIA vapor.
6. The method of claim 1 , wherein the particles containing the containing one or more elements of group IB are alloy particles.
7. The method of claim 1 further comprising mixing the particles with an organic solvent to form the liquid ink.
8. The method of claim 1 further comprising mixing the particles with an inorganic solvent to form the liquid ink.
9. The method of claim 1 wherein the particles are mixed with water to form the liquid ink.
10. The method of claim 1 further comprising adding a dispersant to the liquid ink.
11. The method of claim 1 , further comprising adding one or more surfactants, polymers, dispersants, binders, modifiers, detergents or additives to the liquid ink.
12. The method of claim 1 further comprising adding a binder to the nanoparticles.
13. The method of claim 1 further comprising adding a fluxing agent to the nanoparticles.
14. The method of claim 13 wherein forming a suspension of non-oxide quantum nanoparticles includes sonochemical synthesis of nanoparticles particles containing Se with Cu or In or Ga.
15. The method of claim 1 further comprising adding a water-compatible dispersant to the liquid.
16. The method of claim 1 wherein forming the non-oxide nanoparticles includes preparing particles in a non-oxygen atmosphere.
17. The method of claim 1 wherein forming comprises combining the non-oxide nanoparticles in a solvent to form a suspension.
18. The method of claim 1 wherein forming comprises combining the non-oxide nanoparticles in a solvent to form a colloidal suspension.