Disordered Nanowire Solar Cell

• US 20110083728A1
• Filed: 10/14/2009
• Published: 04/14/2011
• Est. Priority Date: 10/14/2009
• Status: Abandoned Application

• Current Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Wong, William S., Street, Robert A.
• Application Number:
  US12/579,379
• Publication Number:
  US 20110083728A1
• Time in Patent Office: Days
• US Class Current: 136/255
• CPC Class Codes: H01L 31/035227 the quantum structure being quantum wires, or nanorods carbon nanotubes H10K85/211
• CPC Class Codes: H01L 31/075 the potential barriers being only of the PIN type, e.g. amorphous silicon PIN solar cells
• CPC Class Codes: Y02E 10/548 Amorphous silicon PV cells

Abstract

A disordered nanowire solar cell includes doped silicon nanowires disposed in a disordered nanowire mat, a thin (e.g., 50 nm) p-i-n coating layer formed on the surface of the silicon nanowires, and a conformal conductive layer disposed on the upper (e.g., n-doped) layer of the p-i-n coating layer. The disordered nanowire mat is grown from a seed layer using VLS processing at a high temperature (e.g., 450° C.), whereby the crystalline silicon nanowires assume a random interwoven pattern that enhances light scattering. Light scattered by the nanowires is absorbed by p-i-n layer, causing, e.g., electrons to pass along the nanowires to the first electrode layer, and holes to pass through the conformal conductive layer to an optional upper electrode layer. Fabrication of the disordered nanowire solar cell is large-area compatible.

Claims

1. A disordered nanowire solar cell comprising:

a substantially planar first electrode layer;

a disordered nanowire mat including a plurality of nanowires extending from the first electrode in a random interwoven pattern, each nanowire having a fixed end connected to said first electrode layer, a free end disposed away from the first electrode layer, and a body extending between the fixed end and the free end;

a p-i-n coating layer conformally disposed on the free end and at least a portion of the body of each of the plurality of nanowires; and

a conformal conductive layer disposed on the p-i-n coating layer.

2. The solar cell according to claim 1, wherein each of said plurality of nanowires comprises a substantially cylindrical structure having a diameter in the range of 20 and 300 nm and a length in the range of 1 and 30 μ

m.

3. The solar cell according to claim 1, wherein each of said plurality of nanowires comprises doped silicon.

4. The solar cell according to claim 1, wherein the p-i-n coating layer has a nominal thickness in the range of 30 and 300 nm.

5. The solar cell according to claim 4, wherein each of said p-i-n coating layer comprises one of amorphous silicon (a-Si) and amorphous silicon germanium (a-SiGe).

6. The solar cell according to claim 5, wherein the p-i-n coating layer comprises a p-layer disposed in contact with said plurality of nanowires, and n-layer, and an intrinsic layer sandwiched between the p-layer and the p-layer.

7. The solar cell according to claim 6,

wherein each of the plurality of nanowires comprises crystalline silicon doped with boron,

wherein the p-layer comprises a-Si doped with boron, and

wherein the n-layer comprises a-Si doped with a dopant selected from the group of phosphorus and arsenic.

8. The solar cell according to claim 5, wherein the p-i-n coating layer comprises an n-layer disposed in contact with said plurality of nanowires, and p-layer, and an intrinsic layer sandwiched between the p-layer and the n-layer.

9. The solar cell according to claim 8,

wherein each of the plurality of nanowires comprises crystalline silicon doped with a dopant selected from the group of phosphorus and arsenic boron,

wherein the n-layer comprises a-Si doped with a dopant selected from the group of phosphorus and arsenic, and

wherein the p-layer comprises a-Si doped with boron.

10. The solar cell according to claim 1, wherein the conformal conductive layer comprises an effectively transparent conductive material contacting portions of said p-i-n coating layer that are disposed on the free ends and at least a portion of the body of each of said plurality of nanowires.

11. The solar cell according to claim 10,

wherein the substantially planar first electrode layer comprises a first conductive layer electrically connected to the p-i-n coating layer by way of the plurality of nanowires, and

wherein the solar cell further comprises a substantially planar second electrode layer electrically connected to the p-i-n coating layer by way of the conformal conductive layer.

12. The solar cell according to claim 11, wherein one of said first conductive layer and said second electrode layer comprises a reflective material, and the other of said first conductive layer and said second electrode layer comprises a transparent material.

13. The solar cell according to claim 12, wherein said reflective material comprises at least one selected from the group of aluminum and silver, and said transparent material comprises Indium-Tin Oxide (ITO).

14. The solar cell according to claim 13, wherein a height between said first conductive layer and said second electrode layer is in the range of 3 to 50 μ

m.

15. A method for generating a solar cell comprising:

forming a disordered nanowire mat on a seed layer, the disordered nanowire mat including a plurality of nanowires disposed in a random interwoven pattern, each nanowire having a fixed end connected to said seed layer, a free end disposed away from the seed layer, and a body extending between the fixed end and the free end; and

forming a p-i-n coating layer over the disordered nanowire mat such that the p-i-n layer conformally coats at least a portion of the body and free end of each of the plurality of nanowires.

16. The method according to claim 15, wherein forming the nanowire mat comprises:

forming a seed layer on a conductive layer; and

processing the seed layer at 450°

C. by chemical vapor deposition in flowing silane and hydrogen gas while controlling the disorder of the nanowire mat by controlling a partial pressure of the silane gas.

17. The method according to claim 16, wherein forming the seed layer comprises:

forming the conductive layer by sputtering Indium-Tin Oxide (ITO) onto a glass substrate;

forming a silicon layer by deposing silicon on the conductive layer using one of a sputtering process, an evaporation process, and a chemical vapor deposition process; and

forming a gold catalyst by depositing a nanoparticle solution on the silicon layer.

18. The method according to claim 15, wherein forming the p-i-n layer comprises depositing one of amorphous silicon (a-Si) and amorphous silicon-germanium (a-SiGe) using a plasma-enhanced chemical vapor deposition (PECVD) process.

19. The method according to claim 18, wherein forming the p-i-n layer further comprises:

including a p-type dopant during a first phase of the PECVD process to form a conformal p-layer of said p-i-n layer on a surface of the plurality of nanowires,

forming a conformal intrinsic layer on the p-layer during a second phase of the PECVD process, and

including an n-type dopant during a third phase of the PECVD process to form a conformal n-layer of said p-i-n layer on a surface of the intrinsic layer.

20. The method according to claim 15, further comprising depositing a conformal conductive layer onto the disordered nanowire mat.

21. The method according to claim 20, wherein depositing the conformal conductive layer comprises depositing a solution including one of (a) at least one of carbon nanotubes, organic conductors and granular inorganic conductor disposed in a suitable solute, and (b) a dispersion of tetraphenyldiamine (TPD) in a polycarbonate binder.

22. The method according to claim 20, further comprising forming a reflective conductive layer over the conformal conductive layer.