Array of titanium dioxide nanostructures for solar energy utilization

• US 8,920,767 B2
• Filed: 08/19/2011
• Issued: 12/30/2014
• Est. Priority Date: 08/19/2011
• Status: Expired due to Fees

• Current Assignee: UT-Battelle LLC
• Original Assignee: UT-Battelle LLC
• Inventors: Qiu, Xiaofeng, Parans Paranthaman, Mariappan, Chi, Miaofang, Ivanov, Ilia N., Zhang, Zhenyu
• Primary Examiner(s): Mayes, Melvin C
• Assistant Examiner(s): COHEN, STEFANIE J
• Application Number:
  US13/213,923
• Publication Number:
  US 20130045383A1
• Time in Patent Office: 1,229 Days
• Field of Search: None
• US Class Current: 423/610
• CPC Class Codes: H01B 1/08 oxides
• CPC Class Codes: H01L 31/035218 the quantum structure being quantum dots
• CPC Class Codes: H01L 31/035281 Shape of the body
• 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 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y10T 428/2913 Rod, strand, filament or fiber
• CPC Class Codes: Y10T 428/298 Physical dimension

Abstract

An array of titanium dioxide nanostructures for solar energy utilization includes a plurality of nanotubes, each nanotube including an outer layer coaxial with an inner layer, where the inner layer comprises p-type titanium dioxide and the outer layer comprises n-type titanium dioxide. An interface between the inner layer and the outer layer defines a p-n junction.

Claims

1. A titanium dioxide nanostructure for solar energy utilization, the nanostructure comprising:

a nanotube comprising an outer layer coaxial with an inner layer, the inner layer comprising p-type titanium dioxide and the outer layer comprising n-type titanium dioxide, an interface between the inner layer and the outer layer defining a p-n junction.

2. The nanostructure of claim 1, wherein the inner layer comprises a thickness of between about 5 nm and 40 nm.

3. The nanostructure of claim 1, wherein the inner layer comprises titanium dioxide doped with nitrogen.

4. The nanostructure of claim 3, wherein the nitrogen is present in an amount that varies along a radial direction.

5. The nanostructure of claim 4, wherein the amount of nitrogen decreases in the radial direction away from a center of the nanotube.

6. The nanostructure of claim 3, wherein the nitrogen is present in an amount that is substantially uniform along a radial direction.

7. The nanostructure of claim 3, wherein the nitrogen is present in both substitutional and interstitial sites of the titanium dioxide.

8. The nanostructure of claim 7, wherein a majority of the nitrogen is present in the substitutional sites.

9. The nanostructure of claim 1, wherein the outer layer comprises substantially undoped titanium dioxide.

10. The nanostructure of claim 9, wherein the outer layer comprises a thickness of between about 5 nm and 40 nm.

11. The nanostructure of claim 1, wherein the nanotube has an inner diameter of between about 10 nm and 80 nm.

12. An array of titanium dioxide nanostructures for solar energy utilization, the array comprising:

a plurality of nanotubes, each nanotube comprising an outer layer coaxial with an inner layer, the inner layer comprising p-type titanium dioxide and the outer layer comprising n-type titanium dioxide, an interface between the inner layer and the outer layer defining a p-n junction.

13. The array of claim 12, wherein the plurality of nanotube structures exhibit a light absorption of visible light by shifting from 400 nm to 625 nm.

14. A method of making an array of titanium dioxide nanostructures for solar energy utilization, the method comprising:

creating an array of nanotubes comprising titanium dioxide;

exposing the array of nanotubes to a gas comprising a dopant element; and

controllably doping each of the nanotubes to form an inner layer comprising p-type titanium dioxide and an outer layer coaxial with the inner layer that comprises n-type titanium dioxide, where an interface between the inner layer and the outer layer defines a p-n junction.

15. The method of claim 14, wherein creating the array of titanium dioxide nanotubes comprises anodizing a titanium foil.

16. The method of claim 15, wherein the anodizing is carried out at a voltage between 10 V and 100 V.

17. The method of claim 16, wherein the voltage is between about 40 V and 60 V.

18. The method of claim 14, wherein the anodizing is carried out at an anodizing temperature of between about −

20°

C. and about 20°

C.

19. The method of claim 14, wherein the dopant element is nitrogen.

20. The method of claim 14, wherein exposing the array to the gas comprises flowing the gas through the array at a flow rate of between about 2 milliliters/hour and 10 liters/hour.

21. The method of claim 14, further comprising heating the array at an annealing temperature of between about 100°

C. and 700°

C. during the exposure to the gas.

22. The method of claim 21, wherein the annealing temperature is at least about 500°

C.

23. The method of claim 14, wherein the gas is NH₃.