Transparent electrical conductors prepared from sorted carbon nanotubes and methods of preparing same

• US 20090061194A1
• Filed: 08/25/2008
• Published: 03/05/2009
• Est. Priority Date: 08/29/2007
• Status: Active Grant

• Current Assignee: Northwestern University
• Original Assignee: Northwestern University
• Inventors: Hersam, Mark C., Green, Alexander A.
• Granted Patent: US 8,323,784 B2
• Time in Patent Office: Days
• US Class Current: 428/220
• 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 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C08K 3/041 Carbon nanotubes
• CPC Class Codes: C09D 5/24 Electrically-conducting paints conductive materials H01B1/00
• CPC Class Codes: C09D 7/61 inorganic
• CPC Class Codes: C09D 7/70 characterised by shape, e.g. fibres, flakes or microspheres
• CPC Class Codes: H01B 1/24 the conductive material comprising carbon-silicon compounds, carbon or silicon
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

Various methods related to the preparation of transparent electrical conductors based on carbon nanotubes having enhanced optical and electrical properties are disclosed. In some embodiments, the methods involve employing carbon nanotubes that have been presorted according to electronic type and/or optical absorbance for use in transparent electrical conductors. Other embodiments involve use of carbon nanotube bundles that have been pre-sorted according to bundle density.

Claims

1. A colored transparent conductive film comprising:

an average transmittance of greater than about 75% in the visible spectrum;

a sheet resistance of less than about 1.0×

10³ Ω

/square; and

a visible color;

wherein the film comprises single-walled carbon nanotubes.

2. The colored transparent conductive film of claim 1, wherein the film consists essentially of metallic single-walled carbon nanotubes.

3. The colored transparent conductive film of claim 2, wherein the metallic single-walled carbon nanotubes absorb wavelengths within the visible spectrum differentially to provide the visible color of the colored transparent conductive film.

4. The colored transparent conductive film of claim 1, wherein the single-walled carbon nanotubes have a diameter variance of less than or about ±

0.1 nm.

5. The colored transparent conductive film of claim 1, wherein the single-walled carbon nanotubes have a mean diameter selected from about 0.9 nm, about 1.0 nm, about 1.1 nm, about 1.3 nm, about 1.4 nm, and about 1.6 nm.

6. The colored transparent conductive film of claim 1, wherein the visible color is selected from cyan, magenta, yellow, violet, and green.

7. The colored transparent conductive film of claim 1, wherein the single-walled carbon nanotubes are produced by laser ablation, arc-discharge, or high-pressure carbon monoxide conversion.

8. The colored transparent conductive film of claim 1, wherein the film has a sheet resistance of less than about 600 Ω

/square.

9. The colored transparent conductive film of claim 1, wherein the film has a transmittance of greater than about 80% at 550 nm.

10. The colored transparent conductive film of claim 1, wherein the film has a thickness less than about 100 nm.

11. A method of preparing the colored transparent conductive film of claim 1, the method comprising:

isolating a separation fraction from a mixture of semiconducting single-walled carbon nanotubes and metallic single-walled carbon nanotubes, wherein the separation fraction comprises separated single-walled carbon nanotubes and greater than about 50% of the separated single-walled carbon nanotubes in the separation fraction are metallic, and wherein the separated single-walled carbon nanotubes have a diameter variance of less than or about ±

1.0 nm; and

processing the separation fraction into a transparent conductive film having a preselected visible color.

12. The method of claim 11, comprising processing one or more separation fractions comprising a preselected volume, wherein the one or more separation fractions together comprise a preselected amount of separated single-walled carbon nanotubes.

13. The method of claim 12, comprising concentrating the one or more separation fractions to provide a concentrated separation fraction.

14. The method of claim 11, wherein the separation fraction or the concentrated separation fraction is processed into a transparent conductive film by vacuum filtration.

15. The method of claim 11, wherein the single-walled carbon nanotubes in the mixture have diameter dimensions ranging from about 1.0 nm to about 1.2 nm.

16. The method of claim 11, wherein the single-walled carbon nanotubes in the mixture have diameter dimensions ranging from about 1.2 nm to about 1.7 nm.

17. The method of claim 11, wherein greater than about 80% of the separated single-walled carbon nanotubes in the separation fraction are metallic.

18. The method of claim 15, wherein the transparent conductive film has an average transmittance of greater than about 80% in the visible spectrum and a sheet resistance of less than about 1.0×

10³ Ω

/square.

19. The method of claim 15, wherein the transparent conductive film has an average transmittance of greater than about 90% in the near-infrared spectrum and a sheet resistance of less than about 1.0×

10³ Ω

/square.

20. The method of claim 16, wherein the transparent conductive film has an average transmittance of greater than about 80% at a wavelength of 550 nm and a sheet resistance of less than about 600 Ω

/square.

21-36. -36. (canceled)