Multi-element metal powders for silicon solar cells

• US 8,840,701 B2
• Filed: 08/12/2009
• Issued: 09/23/2014
• Est. Priority Date: 08/13/2008
• Status: Active Grant

• Current Assignee: Solar Paste LLC
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Borland, William J., Glicksman, Howard David
• Primary Examiner(s): Kopec, Mark
• Assistant Examiner(s): NGUYEN, HAIDUNG D
• Application Number:
  US12/539,677
• Publication Number:
  US 20100037951A1
• Time in Patent Office: 1,868 Days
• Field of Search: 753/51, 753/63, 753/67, 252/518.1
• US Class Current: 75/367
• CPC Class Codes: B22F 1/00 Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
• CPC Class Codes: B22F 1/065 Spherical particles
• CPC Class Codes: B22F 2201/01 Reducing atmosphere
• CPC Class Codes: B22F 2201/013 Hydrogen
• CPC Class Codes: B22F 2201/02 Nitrogen
• CPC Class Codes: B22F 2201/10 Inert gases
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 9/026 Spray drying of solutions or suspensions
• CPC Class Codes: B22F 9/24 starting from liquid metal compounds, e.g. solutions
• CPC Class Codes: B22F 9/28 starting from gaseous metal compounds
• CPC Class Codes: B22F 9/30 with decomposition of metal compounds, e.g. by pyrolysis
• CPC Class Codes: H01B 1/22 the conductive material comprising metals or alloys
• CPC Class Codes: H01L 31/022425 for 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 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y02E 10/52 PV systems with concentrators

Abstract

Disclosed are methods of making multi-element, finely divided, metal powders containing one or more reactive metals and one or more non-reactive metals. Reactive metals include metals or mixtures thereof from titanium (Ti), zirconium (Zr), hafnium (Hf), tantalum (Ta), niobium (Nb), vanadium (V), nickel (Ni), cobalt (Co), molybdenum (Mo), manganese (Mn), and iron (Fe). Non-reactive metals include metals or mixtures such as silver (Ag), tin (Sn), bismuth (Bi), lead (Pb), antimony (Sb), zinc (Zn), germanium (Ge), phosphorus (P), gold (Au), cadmium (Cd), berrylium (Be), tellurium (Te).

Claims

1. A method for the manufacture of a multi-element, finely divided, spherical, metal powder containing one or more reactive metal powders selected from a group consisting of titanium (Ti), zirconium (Zr), hafnium (Hf), tantalum (Ta), niobium (Nb), vanadium (V), nickel (Ni), cobalt (Co), molybdenum (Mo), manganese (Mn), and iron (Fe) and one or more non-reactive metals selected from a group consisting of tin (Sn), bismuth (Bi), lead (Pb), antimony (Sb), zinc (Zn), germanium (Ge), phosphorus (P), gold (Au), cadmium (Cd), berrylium (Be), and tellurium (Te) comprising the sequential steps:

a. forming a solution of a mixture of thermally decomposable reactive metal containing compounds and non-reactive metal containing compounds in a thermally volatilizable solvent;

b. forming an aerosol consisting essentially of finely divided droplets of the solution from step A dispersed in a carrier gas, the droplet concentration which is below the concentration where collisions and subsequent coalescence of the droplets results in a 10% reduction in droplet concentration;

c. heating the aerosol to an operating temperature above a decomposition temperature of the reactive metal containing compounds and non-reactive metal containing compounds but below a melting point of the resulting multi-metallic alloy by which (1) the solvent is volatilized, (2) the reactive metal containing compounds and the non reactive metal containing compounds are decomposed to form finely, divided particles, (3) the particles form an alloy and are densified; and

d. separating the multi-element, finely divided, spherical, metal powder containing at least one reactive metal powder and one non-reactive metal powder from the carrier gas, reaction by-products, and solvent volatilization products.

2. The method of claim 1 wherein the operating temperature is between 300°

C. and 1600°

C.

3. The method of claim 1 where the carrier gas is an inert gas that does not react with the metals included in the multi-metallic particles.

4. The method of claim 3 where the carrier gas is nitrogen.

5. The method of claim 3 where the carrier gas is a reducing gas.

6. The method of claim 3 where the carrier gas is nitrogen gas with 4% hydrogen gas.

7. The method of claim 1 where a co-solvent is added in step a. to act as a reducing agent.

8. The method of claim 7 where the co-solvent reducing agent is an organic compound having 1 to 5 carbons.

9. The method of claim 8 where the co-solvent reducing agent is an alcohol.

10. The method of claim 7 where the co-solvent present in an amount of about 1% to about 50% by volume of the solution.