Solution-based fabrication of photovoltaic cell

• US 20050183767A1
• Filed: 02/19/2004
• Published: 08/25/2005
• Est. Priority Date: 02/19/2004
• Status: Active Grant

• Current Assignee: Aeris Capital Sustainable IP, Ltd.
• Original Assignee: Nanosolar Incorporated
• Inventors: Yu, Dong, Roscheisen, Martin R., Sager, Brian M., Fidanza, Jacqueline
• Granted Patent: US 7,663,057 B2
• Time in Patent Office: Days
• US Class Current: 136/263
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 5/00 Nanobiotechnology or nanomedicine, e.g. protein engineering or drug delivery
• CPC Class Codes: C23C 18/1204 inorganic material, e.g. non-oxide and non-metallic such as sulfides, nitrides based compounds
• CPC Class Codes: C23C 18/1266 Particles formed in situ
• CPC Class Codes: C23C 18/1295 with after-treatment of the deposited inorganic material
• CPC Class Codes: H01L 31/0322 comprising only AIBIIICVI chalcopyrite compounds, e.g. Cu In Se2, Cu Ga Se2, Cu In Ga Se2
• CPC Class Codes: H01L 31/06 characterised by potential barriers
• CPC Class Codes: H01L 31/0749 including a AIBIIICVI compound, e.g. CdS/CulnSe2 [CIS] heterojunction solar cells
• CPC Class Codes: H01L 31/18 Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• CPC Class Codes: Y02E 10/541 CuInSe2 material PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

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 H₂Se 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.

Claims

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-xGa_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.

44. The method of claims 1, 13, or 40 further comprising the step of capping the nanoparticles with an organic material.

45. The method of claim 44 wherein the organic material is a small molecule with low boiling point.

46. The method of claim 44 wherein the organic material is selected from the group of trioctylphosphine oxide, trioctylphosphine, triphenylphosphine, pyridine, alcohols (methanol, ethanol, propanol, butanol), ethane thiol, tetrahydrofuran, ethers, ammonia, amines (methyl amine, ethylamine, ethylenediamine) and acetonitrile.

47. The method of claims 44 wherein the organic material is pyridine.

48. The method of claim 1, 13, or 40 wherein forming a mixture of non-oxide nanoparticles includes selecting particles in the desired particle size range.

49. The method of claim 48, wherein selecting nanoparticles in the desired size range includes adjusting one or more parameters of a reaction that forms the nanoparticles, size-selective precipitation, or ultrafiltration.

50. The method of claims 1, 13 or 40 further comprising adding a water-compatible dispersant to the liquid.

51. The method of claims 1, 13, or 40 wherein forming the non-oxide nanoparticles includes preparing particles in a non-oxygen atmosphere.

61. A method for fabricating a photovoltaic cell active layer containing a IB-IIIA-VIA alloy, comprising the steps of:

forming a liquid ink containing intermixed nanoparticles of elements from groups IB, IIIA and optionally VIA, using the method of claim 1, 13, 40 or 52;

spreading a film of the liquid onto a substrate;

annealing the film to form the active layer; and

exposing the film to Se-containing vapor.

62. The method of claim 61, wherein the IB-IIIA-VIA alloy is an alloy of copper (Cu) with indium (In) or Gallium (Ga) and selenium (Se) or sulfur (S) having a stoichiometric ratio of the Cu, In and Se or S of approximately CuIn_1-xGa_x(S or Se)₂, wherein x is between 0 and 1.

63. The method of claim 61 wherein the substrate is a polymer or metallized polymer.

64. The method of claim 61, wherein annealing the film includes heating the film to a temperature between about 200°

C. and about 600°

C.

65. The method of claim 61, wherein the film is spread onto the substrate and/or annealed in a roll-to-roll production system.

66. The method of claim 61, further comprising, winding the substrate into a coil and exposing the coiled substrate to selenium vapor.

67. The method of claim 61 wherein annealing the substrate includes winding the substrate into a coil and heating the coiled substrate.

68. The method of claim 61, further comprising winding the substrate into a coil and depositing a layer of material on one or more surfaces of the coiled substrate.

69. The method of claim 61 wherein the layer of material includes a transparent conductive oxide.

70. The method of claim 61 wherein forming the liquid, spreading the film of the liquid and annealing the film does not include the use of H₂Se to selenize the particles, film or active layer.

71. The method of claim 61 wherein forming the liquid, spreading the film of the liquid and annealing the film does not include reduction of the particles, film or active layer with H₂.

72. A photovoltaic cell, comprising:

a base electrode;

a top electrode; and

an active layer disposed between the base electrode and top electrode, the active layer containing a IB-IIIA-VIA alloy, wherein the active layer is formed from a liquid ink containing nanoparticles of elements from groups IB, IIIA and optionally VIA, using the method of claim 1, 13, 50 or 52.

73. The cell of claim 72 wherein at least one of the base electrode and top electrode is transparent.

74. The cell of claim 72 further comprising a layer of cadmium sulfide (CdS), zinc sulfide (ZnS), or zinc selenide (ZnS) or some combination of two or more of these disposed between the active layer and the top electrode.

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-xGa_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+InCl₃(+GaI₃)+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 CuCl₂)+InCl₃ (or InI₃ or GaI₃)+Na₂Se+ligand/capping agent→

Cu(Ga,In)Se₂.

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 (PPh₃)₂CuIn(SEt)₄ or (PPh₃)₂CuIn(SePh)₄.

21. The method of claim 13 wherein forming a mixture of non-oxide quantum nanoparticles includes spray co-precipitation of two or more reactants.

22. The method of claim 21 wherein one of the two or more reactants is selected from the group of metal halides, metal acetates, metal sulfates, metal nitrates, metal alcholates, metal carbonates, metal phenolates, metal hydroxides, and organometallics.

23. The method of claim 22 wherein the two or more reactants include one or more reactants of the type X/Hal, where X is Cu or In and Hal is chlorine (Cl) or iodine (I).

24. The method of claim 23 wherein the two or more reactants further include thiourea or selenourea.

25. The method of claim 13 wherein forming a mixture of non-oxide quantum nanoparticles includes performing a reaction of the type:

(IB)(Et₂CN(VIA)₂)₂+TOPO→

IB-VIA

26. The method of claim 25 wherein IB is Cu and VIA is Se or S.

27. The method of claim 13 wherein forming a mixture of non-oxide quantum nanoparticles includes performing a reaction of the type:

(IB)(Hal)+Na₂(VIA)+ligand/capping agent→

IB−

VIA+2Na(Hal)

28. The method of claim 27 wherein the ligand/capping agent is selected from the group of trioctylphosphine oxide, trioctylphosphine, triphenylphosphine, pyridine, alcohols (methanol, ethanol, propanol, butanol), ethane thiol, tetrahydrofuran, ethers, ammonia, amines (methyl amine, ethylamine, ethylenediamine) and acetonitrile.

29. The method of claim 27 wherein the reaction is of the type:

CuCl₂+Na₂Se+Pyridine→

CuSe+2NaI.

30. The method of claim 13 wherein forming a mixture of non-oxide quantum nanoparticles includes performing a reaction of the type:

(IB)(Hal)+(IIIA)(Hal)+Na₂(VIA)+Ligand/Capping Agent→

IB-IIIA-VIA

31. The method of claim 30 wherein the reaction is of the type:

2InI₃+3Na₂Se→

In₂Se₃+6NaI.

32. The method of claim 13 wherein forming a mixture of non-oxide quantum nanoparticles includes sonochemical synthesis of nanoparticles particles containing Se with Cu or In or Ga.

33. The method of claim 13 wherein forming non-oxide quantum nanoparticles includes preparing metal nanoparticles containing elements of groups IB, IIIA, VIA or a IB-IIIA-VIA alloy, by laser ablation, nucleation from vapor, exploding wires by electrical current surge, thermal decomposition of organometallic compounds, sonolysis, pulse radiolysis, electrochemical reduction or chemical reduction.

34. The method of claim 13 wherein the liquid is formed by mixture with water.

35. The method of claim 13 wherein the liquid is formed by mixture with organic solvent.

36. The method of claim 13, further comprising adding a capping agent to the non-oxide quantum nanoparticles.

37. The method of claim 13, further comprising adding a binder to the non-oxide quantum nanoparticles.

38. The method of claim 13, further comprising adding a fluxing agent to the non-oxide quantum nanoparticles.

39. The method of claim 13, further comprising adding one or more surfactants, polymers, dispersants, binders, modifiers, detergents or additives to the non-oxide quantum nanoparticles.

40. A method for fabricating a liquid containing intermixed elements of groups IB and IIIA and optionally VIA, comprising the steps of:

forming nanoparticles from group IB; and

intermixing the nanoparticles from group IB with elements from group IIIA, wherein the elements from group IIIA are in molten form, wherein the nanoparticles from group IB comprise particles in a desired particle size range of between about 0.1 nm and about 500 nm in diameter, wherein a majority of the mass of the 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 nanoparticles with the molten elements to form a liquid that serves as an ink.

41. The method of claim 40 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-xGa_x(S or Se)₂, where x is between 0 and 1.

42. The method of claim 41 wherein a majority of the group IB nanoparticles range in size from no more than about 40% above or below an average nanoparticle size, or, if the average nanoparticle size is less than about 5 nanometers, from no more than about 2 nanometers above or below the average nanoparticle size.

43. The method of claim 40, further comprising adjusting the temperature of the Cu—

In—

Ga mixture until a solid forms and then grinding the solid to form nanoparticles.

52. A method for fabricating a liquid containing elements of groups IB, IIIA and optionally VIA, comprising the steps of:

forming nanoparticles containing elements 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 a majority of the mass of the 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 nanoparticles to form a liquid that serves as an ink.

53. The method of claim 52 wherein the nanoparticles sizes are chosen to optimize their melting points with respect to each other.

54. The method of claim 52 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-xGa_x(S or Se)₂, where x is between 0 and 1.

55. The method of claim 52 wherein forming the metallic nanoparticles includes mixing one or more liquid organometallic precursors of IB, IIIA and VIA elements.

56. The method of claim 52, further comprising burning organic components out of the ink by heating.

57. The method of claim 52 wherein using one or more organic precursors includes forming a sol-gel from the organometallics.

58. The method of claim 57, further comprising burning organic components out of the sol gel by heating to produce a remnant mixture.

59. The method of claim 58, further comprising, after burning out the organic components, exposing the remnant mixture to H₂ gas.

60. The method of claim 52 wherein mixing the nanoparticles to form the liquid includes mixing a metal halide and a chelating agent.