Fabrication of Electrically Active Films Based on Multiple Layers

• US 20080257201A1
• Filed: 04/17/2008
• Published: 10/23/2008
• Est. Priority Date: 04/18/2007
• Status: Active Grant

• Current Assignee: Nanoco Technologies Limited (Nanoco Group Plc)
• Original Assignee: Nanoco Technologies Limited (Nanoco Group Plc)
• Inventors: Pickett, Nigel, Harris, James
• Granted Patent: US 8,563,348 B2
• Time in Patent Office: Days
• US Class Current: 106/1.18
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: C01G 15/006 Compounds containing, besides gallium, indium, or thallium, two or more other elements, with the exception of oxygen or hydrogen
• CPC Class Codes: C23C 24/08 by application of heat or pressure and heat C23C24/04 takes precedence
• CPC Class Codes: C23C 26/00 Coating not provided for in groups C23C2/00 - C23C24/00
• CPC Class Codes: H01L 21/02568 Chalcogenide semiconducting materials not being oxides, e.g. ternary compounds
• CPC Class Codes: H01L 21/02601 Nanoparticles fullerenes H10K85/211
• CPC Class Codes: H01L 21/02628 using solutions
• 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: Y02E 10/541 CuInSe2 material PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A continuous film of desired electrical characteristics is obtained by successively printing and annealing two or more dispersions of prefabricated nanoparticles.

Claims

1. A method of fabricating a film, the method comprising the steps of:

a. providing a substrate and a plurality of flowable printing compositions each comprising a different dispersion of prefabricated nanoparticles of specific elemental composition and having an average size no greater than 100 nm;

b. printing a layer of one of the printing compositions onto the substrate;

c. annealing the printed layer to form a continuous film; and

d. repeating steps (b) and (c) with another or the same printing composition to form the film.

2. The method of claim 1, wherein at least some of the printed layers have a thickness smaller than 1 μ

m.

3. The method of claim 1 further comprising repeating step (b) at least once before step (c).

4. The method of claim 1 further comprising the step of performing an etch after printing and before annealing.

5. The method of claim 1 wherein the printing compositions are suspensions.

6. The method of claim 1 wherein the printing compositions are solutions.

7. The method of claim 1 wherein the printing step is performed by a printing technique selected from the group consisting of inkjet printing, pneumatic spraying, screen printing, pad printing, laser printing, dot matrix printing, thermal printing, lithography, or 3D printing.

8. The method of claim 1 wherein at least some of the printing compositions contain the same types of nanoparticles in different proportions, the layers being applied to create a concentration gradient of at least one material through the film.

9. The method of claim 1 wherein the nanoparticles of each composition comprise the same elements in different proportions, the layers being applied to create a concentration gradient of at least one material through the film.

10. The method of claim 9 wherein a first set of nanoparticles comprises or consists essentially of CuIn_1-xGa_xSe₂, with x varying through the printing compositions.

11. The method of claim 1 wherein each printing composition comprises different types of nanoparticles.

12. The method of claim 1 wherein the nanoparticles have a size no greater than 20 nm and a low size dispersity.

13. The method of claim 1 wherein the thin film comprises a semiconductor and interacts electrically with the substrate.

14. The method of claim 13 further comprising adding an electrically conductive superstrate and external contacts to produce a semiconductor device.

15. The method of claim 14, wherein the semiconductor device is a solar cell.

16. A flowable printing composition comprising a carrier and a dispersion of nanoparticles therein, the nanoparticles comprising first and second components, the first component comprising at least one of Cu or Ag, and the second component comprising at least one of Se, Te, or S, the composition having a viscosity substantially independent of flow rate.

17. The printing composition of claim 16, wherein the first component comprises Cu or Ag, but not both.

18. The printing composition of claim 16, wherein the second component comprises exactly one of the elements Se, Te, or S.

19. A flowable printing composition comprising a carrier and a dispersion of nanoparticles therein, the nanoparticles each comprising first, second, and third components, the first component comprising at least one of Cu or Ag, the second component comprising at least one of Se, Te, or S, and the third component comprising at least one of In, Ga, or Al, the composition having a viscosity substantially independent of flow rate.

20. The printing composition of claim 19, wherein the first component comprises Cu or Ag, but not both.

21. The printing composition of claim 19, wherein the second component comprises exactly one of the elements Se, Te, or S.