High-throughput printing of semiconductor precursor layer from inter-metallic microflake articles

• US 20070163642A1
• Filed: 03/30/2006
• Published: 07/19/2007
• Est. Priority Date: 02/19/2004
• Status: Abandoned Application

• Current Assignee: Aeris Capital Sustainable IP, Ltd.
• Original Assignee: Nanosolar Incorporated
• Inventors: Sager, Brian, Van Duren, Jeroen, Robinson, Matthew
• Application Number:
  US11/395,426
• Publication Number:
  US 20070163642A1
• Time in Patent Office: Days
• US Class Current: 136/262
• CPC Class Codes: C23C 18/1229 Composition of the substrate
• CPC Class Codes: C23C 18/127 Preformed particles
• CPC Class Codes: C23C 18/1275 performed under inert atmosphere
• CPC Class Codes: C23C 18/1283 Control of temperature, e.g. gradual temperature increase, modulation of temperature
• CPC Class Codes: C23C 18/143 Radiation by light, e.g. photolysis or pyrolysis
• CPC Class Codes: C23C 18/145 Radiation by charged particles, e.g. electron beams or ion irradiation
• 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

Methods and devices are provided for high-throughput printing of semiconductor precursor layer from microflake particles. In one embodiment, the method comprises of transforming non-planar or planar precursor materials in an appropriate vehicle under the appropriate conditions to create dispersions of planar particles with stoichiometric ratios of elements equal to that of the feedstock or precursor materials, even after settling. In particular, planar particles disperse more easily, form much denser coatings (or form coatings with more interparticle contact area), and anneal into fused, dense films at a lower temperature and/or time than their counterparts made from spherical nanoparticles. These planar particles may be microflakes that have a high aspect ratio. The resulting dense film formed from microflakes are particularly useful in forming photovoltaic devices. In one embodiment, at least one set of the particles in the ink may be inter-metallic flake particles (microflake or nanoflake) containing at least one group IB-IIIA inter-metallic alloy phase.

Claims

1. A method comprising:

formulating an ink of particles wherein about 50% or more of all the particles are microflakes each containing at least one element from group IB, IIIA and/or VIA and having a non-spherical, planar shape, wherein overall amounts of elements from group IB, IIIA and/or VIA contained in the ink are such that the ink has a desired stoichiometric ratio of the elements;

coating a substrate with the ink to form a precursor layer; and

processing the precursor layer in a suitable atmosphere to form a dense film;

wherein at least one set of the particles in the ink are inter-metallic microflake particles containing at least one group IB-IIIA inter-metallic alloy phase.

2. The method of claim 1 wherein the dense film is used in the formation of a semiconductor absorber for a photovoltaic device.

3. The method of claim 1 wherein substantially all of the particles have a non-spherical, planar shape.

4. The method of claim 1 wherein the particles comprise of microflakes and nanoflakes.

5. The method of claim 1 wherein at least about 75% or more of a total weight of all the particles are microflakes.

6. The method of claim 2 wherein the planar shape of the microflakes results in grain sizes of at least about 2.0 μ

m in at least one dimension in the semiconductor absorber of a photovoltaic device.

7. The method of claim 2 wherein the planar shape of the microflakes results in grain sizes of at least about 1.0 μ

m in at least one dimension in the semiconductor absorber of a photovoltaic device.

8. The method of claim 2 wherein the planar shape of the microflakes results in grain sizes of at least about 0.5 μ

m in at least one dimension in the semiconductor absorber of a photovoltaic device.

9. The method of claim 1 wherein the microflakes are of random planar shape and/or a random size distribution.

10. The method of claim 1 wherein the microflakes are of a non-random planar shape and/or a non-random size distribution.

11. The method of claim 1 wherein the microflakes each have a length less than about 5 microns and greater than about 0.5 microns.

12. The method of claim 1 wherein the microflakes each have a length between about 3 microns and 0.5 microns.

13. The method of claim 1 wherein the microflakes each have a thickness less than about 10 nm.

14. The method of claim 1 wherein the microflakes each have a thickness less than about 20 nm.

15. The method of claim 1 wherein the microflakes have length of less than about 2 microns and a thickness of less than 100 nm.

16. The method of claim 1 wherein the microflakes have length of less than about 1 microns and a thickness of less than 50 nm.

17. The method of claim 1 wherein the microflakes have an aspect ratio of at least about 10 or more.

18. The method of claim 1 wherein the microflakes have an aspect ratio of at least about 15 or more.

19. The method of claim 1 wherein the microflakes are substantially oxygen-free.

20. The method of claim 1 wherein the coating step occurs at room temperature.

21. The method of claim 1 wherein the coating step occurs at atmospheric pressure.

22. The method of claim 1 further comprising forming a film of selenium on the precursor layer.

23. The method of claim 1 wherein the processing step is accelerated via thermal processing techniques using at least one of the following:

pulsed thermal processing, laser beams, or heating via IR lamps.

24. The method of claim 1 wherein the suitable atmosphere comprises of a non-oxygen atmosphere containing chalcogen vapor at a partial pressure of the chalcogen greater than or equal to a vapor pressure of the chalcogen at the processing temperature and processing pressure to minimize loss of chalcogen from the precursor layer, wherein the processing pressure is a non-vacuum pressure and wherein the particles are one or more types of binary chalcogenides.

25. The method of claim 1 wherein, prior to the step of formulating the ink, there is included the step of creating microflakes comprising:

providing feedstock particles containing at least one element of groups IB, IIIA, and/or VIA, wherein substantially each of the feedstock particles have a composition of sufficient malleability to form a planar shape from a non-planar or planar starting shape; and

milling the feedstock particles to reduce at least the thickness of each particle to less than 250 nm.

26. The method of claim 52 wherein the milling step occurs in an oxygen-free atmosphere to create oxygen-free microflakes.

27. The method of claim 1 wherein the microflakes are microflakes having lengths of greater than 500 nm.

28. The method of claim 1 wherein the microflakes are microflakes having lengths of greater than 750 nm.

29. The method of claim 1 wherein the microflakes are microflakes having thicknesses of at least 75 nm.

30. The method of claim 1 wherein the substrate is a rigid substrate.

31. The method of claim 1 wherein the substrate is a flexible substrate.

32. The method of claim 1 wherein the substrate comprises of a material selected from the group consisting of glass, soda-lime glass, steel stainless steel, aluminum, polymer, and ceramic.

33. The method of claim 1 wherein the film is formed from the precursor layer of the microflakes and a layer of a sodium containing material in contact with the precursor layer.

34. The method of claim 1 wherein the film is formed from the precursor layer of the microflakes and a layer of a sodium containing material in contact with the precursor layer.

35. The process of claim 1 wherein the film includes a group IB-IIIA-VIA compound.

36. The process of claim 1 wherein reacting comprises heating the layer in the suitable atmosphere.

37. The process of claim 1 wherein at least one set of the particles in the dispersion is in the form of nanoglobules.

38. The process of claim 1 wherein at least one set of the particles in the dispersion are in the form of nanoglobules and contain at least one group IIIA element.

39. The process of claim 1 wherein at least one set of the particles in the dispersion is in the form of nanoglobules comprising of a group IIIA element in elemental form.

40. The process of claim 1 wherein the inter-metallic phase is not a terminal solid solution phase.

41. The process of claim 1 wherein the inter-metallic phase is not a solid solution phase.

42. The process of claim 1 wherein inter-metallic particles contribute less than about 50 molar percent of group IB elements found in all of the particles.

43. The process of claim 1 wherein inter-metallic particles contribute less than about 50 molar percent of group IIIA elements found in all of the particles.

44. The process of claim 1 wherein inter-metallic particles contribute less than about 50 molar percent of the group IB elements and less than about 50 molar percent of the group IIIA elements in the dispersion deposited on the substrate.

45. The process of claim 1 wherein inter-metallic particles contribute less than about 50 molar percent of the group IB elements and more than about 50 molar percent of the group IIIA elements in the dispersion deposited on the substrate.

46. The process of claim 1 wherein inter-metallic particles contribute more than about 50 molar percent of the group IB elements and less than about 50 molar percent of the group IIIA elements in the dispersion deposited on the substrate.

47. The process of claim 10 wherein the molar percent is based on a total molar mass of the elements in all particles present in the dispersion.

48. The process of claim 1 wherein at least some of the particles have a platelet shape.

49. The process of claim 1 wherein a majority of the particles have a platelet shape.

50. The process of claim 1 wherein all of the particles have a platelet shape.

51. The process of claim 1 wherein the depositing step comprises coating the substrate with the dispersion.

52. The process of claim 1 wherein the dispersion comprises an emulsion.

53. The process of claim 1 wherein the inter-metallic material is a binary material.

54. The process of claim 1 wherein the inter-metallic material is a ternary material.

55. The process of claim 1 wherein the inter-metallic material comprises Cu₁In₂.

56. The process of claim 1 wherein the inter-metallic material comprises a composition in a δ

phase of Cu₁In₂.

57. The process of claim 1 wherein the inter-metallic material comprises a composition in between a δ

phase of Cu₁In₂ and a phase defined by Cu₁₆In₉.

58. The process of claim 1 wherein the inter-metallic material comprises Cu₁Ga₂.

59. The process of claim 1 wherein the inter-metallic material comprises an intermediate solid-solution of Cu₁Ga₂.

60. The process of claim 1 wherein the inter-metallic material comprises Cu₆₈Ga₃₈.

61. The process of claim 1 wherein the inter-metallic material comprises Cu₇₀Ga₃₀.

62. The process of claim 1 wherein the inter-metallic material comprises Cu₇₅Ga₂₅.

63. The process of claim 1 wherein the inter-metallic material comprises a composition of Cu—

Ga of a phase in between the terminal solid-solution and an intermediate solid-solution next to it.

64. The process of claim 1 wherein the inter-metallic comprises a composition of Cu—

Ga in a γ

₁ phase (about 31.8 to about 39.8 wt % Ga).

65. The process of claim 1 wherein the inter-metallic comprises a composition of Cu—

Ga in a γ

₂ phase (about 36.0 to about 39.9 wt % Ga).

66. The process of claim 1 wherein the inter-metallic comprises a composition of Cu—

Ga in a γ

₃ phase (about 39.7 to about −

44.9 wt % Ga).

67. The process of claim 1 wherein the inter-metallic comprises a composition of Cu—

Ga in a θ

phase (about 66.7 to about 68.7 wt % Ga).

68. The process of claim 1 wherein the inter-metallic comprises a composition of Cu—

Ga in a phase between γ

₂ and γ

₃.

69. The process of claim 1 wherein the inter-metallic comprises a composition of Cu—

Ga in a phase between the terminal solid solution and γ

₁.

70. The process of claim 1 wherein the inter-metallic material comprises Cu-rich Cu—

Ga.

71. The process of claim 1 wherein gallium is incorporated as a group IIIA element in the form of a suspension of nanoglobules.

72. The process of claim 71 wherein nanoglobules of gallium are formed by creating an emulsion of liquid gallium in a solution.

73. The process of claim 71 wherein gallium is quenched below room temperature.

74. The process of claim 71 further comprising maintaining or enhancing a dispersion of liquid gallium in solution by stirring, mechanical means, electromagnetic means, ultrasonic means, and/or the addition of dispersants and/or emulsifiers.

75. The process of claim 1 further comprising adding a mixture of one or more elemental particles selected from:

aluminum, tellurium, or sulfur.

76. The process of claim 1 wherein the suitable atmosphere contains at least one of the following:

selenium, sulfur, tellurium, H₂, CO, H₂Se, H₂S, Ar, N₂ or combinations or mixture thereof.

77. The process of claim 1 wherein the suitable atmosphere contains at least one of the following:

H₂, CO, Ar, and N₂.

78. The process of claim 1 wherein one or more classes of the particles are doped with one or more inorganic materials.

79. The process of claim 1, wherein one or more classes of the particles are doped with one or more inorganic materials chosen from the group of aluminum (Al), sulfur (S), sodium (Na), potassium (K), or lithium (Li).

80. The process of claim 1 wherein the particles are nanoparticles.

81. The process of claim 1 further comprising forming the particles from a feedstock having an inter-metallic phase.

82. The process of claim 1 wherein the inter-metallic material comprises Cu-rich Cu—

Ga.

83. A method comprising:

formulating an ink of particles wherein a majority of the particles are microflakes each containing at least one element from group IB, IIIA and/or VIA and having a non-spherical, planar shape, wherein the overall amounts of the elements from group IB, IIIA and/or VIA contained in the ink are such that the ink has a desired stoichiometric ratio of the elements;

coating a substrate with the ink to form a precursor layer; and

processing the precursor layer to form a dense film for growth of a semiconductor absorber of a photovoltaic device;

wherein at least one set of the particles in the ink are inter-metallic microflake particles containing at least one group IB-IIIA inter-metallic alloy phase.

84. The method of claim 83 wherein at least 80% of the particles are microflakes.

85. The method of claim 83 wherein at least 90% of the particles are microflakes.

86. A composition comprising:

a plurality of particles comprising group IB and/or IIIA elements, and, optionally, at least one group VIA element;

wherein at least one set of the particles are microflakes containing at least one group IB-IIIA inter-metallic alloy phase.