MULTISTAGE THICK FILM THERMOELECTRIC DEVICES

• US 20080178606A1
• Filed: 01/30/2007
• Published: 07/31/2008
• Est. Priority Date: 01/30/2007
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Chen, Gang, Yang, Ronggui, Chen, Xiaoyuan
• Granted Patent: US 9,391,255 B2
• Time in Patent Office: Days
• US Class Current: 62/3.7
• CPC Class Codes: H10N 19/101 Multiple thermocouples connected in a cascade arrangement

Abstract

The present invention generally provides multistage thermoelectric coolers and methods for their fabrication. For example, in one aspect, a multistage thermoelectric cooler is disclosed that includes at least two cooling stages, each of which comprises a p-type leg portion and an n-type leg portion coupled to form a p-n junction. The p-n junctions of the two stages are thermally and electrically coupled such that at least a portion of a current flowing, during operation of the device, through one stage is coupled to the other. Further, at least one of the p- or n-type leg portions of one stage forms a unitary structure with a corresponding p- or n-type leg portion of the other stage.

Claims

1. A multistage thermoelectric cooler, comprising

a plurality of thermoelectric cooling stages comprising at least one p-type leg and an n-type leg coupled to form a p-n junction such that at least a portion of a current flowing, during operation of the cooler, through one stage is coupled into a subsequent stage,

wherein at least one of said p or n-type legs forms a unitary structure spanning a plurality of cooling stages.

2. The multistage cooler of claim 1, wherein at least two of said stages exhibit a difference in heat dissipation.

3. The multistage cooler of claim 2, wherein a leg portion associated with a cooling stage is characterized by a length (L) and a cross-sectional area (A), wherein ratios of length to cross-sectional area (L/A) associated with p-type or n-type leg portions of at least two of said stages are different.

4. The multistage cooler of claim 1, wherein at least two leg portions corresponding to a cooling stage exhibit different ratios of length to cross-sectional areas.

5. The multistage cooler of claim 3, wherein the L/A ration associated with at least a p-type or n-type leg portion of the one of said at least two stages that dissipates more heat is less than a corresponding ratio of the other stage.

6. The multistage cooler of claim 1, further comprising an electrode electrically coupled to one of said stages to apply a current thereto.

7. The multistage cooler of claim 1, wherein said p-type and n-type legs of at least two of said stages are disposed in a common plane.

8. The multistage cooler of claim 1, wherein said p-type leg is disposed on one plane and said n-type leg is disposed in a substantially parallel plane.

9. A multistage thermoelectric cooler, comprising:

at least first and second thermoelectric cooling stages comprising at least one p-type thermoelectric leg and one n-type thermoelectric leg coupled to one another so as to form a p-n junction, each leg spanning both stages such that a first portion of each leg extending from one end thereof to said p-n junction belongs to one stage and another portion of that leg extending from said p-n junction to another end thereof belongs to the other stage.

10. The multistage cooler of claim 9, wherein a first temperature gradient develops across said first portion of said legs and a second temperature gradient develops across said second portions of said legs during operation of the thermoelectric cooler.

11. A thermoelectric cooler, comprising

at least two thermoelectric stages, each of said stages comprising a p-type segment and an n-type segment forming a p-n junction, wherein the p-n junctions of the two stages are thermally and electrically coupled,

wherein said p-type and n-type segments of the two stages are disposed in substantially a common plane.

12. The thermoelectric cooler of claim 11, wherein the p-type segment of one stage forms a unitary structure with the p-type segment of the other stage.

13. The thermoelectric cooler of claim 11, wherein the n-type segment of one stage forms a unitary structure with the n-type segment of the other stage.

14. A thermoelectric cooler, comprising

at least two cooling stages, each of said stages comprising a p-type segment and an n-type segment forming a p-n junction, wherein the p-n junctions of the two stages are thermally and electrically coupled,

wherein at least two of said segments are disposed in separate and substantially parallel planes.

15. The thermoelectric cooler of claim 14, wherein the p and n-type segments of one stage are disposed in one plane and the p and n-type segments of the other stage are disposed in a separate and substantially parallel plane.

16. The thermoelectric cooler of claim 14, wherein the p-type segment of one stage and the n-type segment of the other stage are disposed in a substantially common plane.

17. A thermoelectric cooling device, comprising

a plurality of multistage thermoelectric coolers coupled between a cold platform and a hot stage so as to pump heat, in parallel, from the platform to the stage,

said thermoelectric coolers being angularly distributed around said platform,

wherein each thermoelectric cooler comprises at least first and second cooling stages that are thermally and electrically coupled to one another.

18. The thermoelectric cooling device of claim 17, wherein one or more of said thermoelectric coolers exhibit a planar configuration.

19. The thermoelectric cooling device of claim 17, wherein said platform is substantially transparent to electromagnetic radiation having wavelengths in a selected range.

20. A multistage thermoelectric cooler, comprising

at least two legs one of which is formed of a p-type and the other of an n-type thermoelectric material,

each of said legs having a first portion across which a first temperature gradient is generated and a second portion across which a second temperature gradient is generated, said portions forming a contiguous thermoelectric structure,

wherein said legs are bonded so as to form an electrically and thermally conductive contact junction.

21. The thermoelectric cooler of claim 20, wherein each of said p-type and n-type legs has a thickness in a range of about 1 micron to about 1 mm.

22. The thermoelectric cooler of claim 20, wherein said first portion of each of the legs has a length different than that of the second portion of that leg.

23. The thermoelectric cooler of claim 20, wherein said p-type and n-type legs are disposed in two separate substantially parallel planes.

24. The thermoelectric cooler of claim 20, wherein each of said legs has a length in a range of about 20 microns to about 1 mm.

25. The thermoelectric cooler of claim 20, further comprising a platform thermally coupled to said contact junction to be maintained at a lower temperature of said second temperature gradient.

26. The thermoelectric cooler of claim 25, wherein said platform is substantially transparent to electromagnetic radiation having one or more selected wavelength components.

27. The thermoelectric cooler of claim 20, further comprising a support substrate adapted for mechanically coupling to at least one of said legs.

28. The thermoelectric cooler of claim 27, wherein said support substrate comprises a peripheral portion surrounding a hollow central portion.

29. The thermoelectric cooler of claim 28, wherein the first portions of the legs at ends thereof maintained at a higher temperature of said first temperature gradient are mechanically coupled to said peripheral portion of the support substrate.

30. The thermoelectric cooler of claim 29, further comprising an electrical lead disposed on said peripheral portion and electrically coupled to said legs so as to apply an electrical current to said thermoelectric cooler.

31. A multistage thermoelectric cooler, comprising:

a plurality of legs formed of a p-type thermoelectric material and a plurality of legs formed of an n-type thermoelectric material,

said p-type and n-type legs being thermally and electrically linked in a cross-bar configuration to provide a plurality of cascading cooling stages,

wherein said p-type and n-type legs are disposed in a common plane.

32. The multistage cooler of claim 31, wherein each of said legs comprises a continuous thermoelectric structure formed of a first portion extending between first and second locations and a second portion extending between said second location and a third location.

33. The multistage cooler of claim 31, wherein said cross-bar configuration is characterized by at least one of the n-type legs forming contact junctions at the first, second and third locations thereof with the first, second and third locations, respectively, of three different ones of said p-type legs.

34. The multistage cooler of claim 33, wherein said cross-bar configuration is further characterized by at least one of the p-type legs forming contact junctions at the first, second and third locations thereof with the first, second and third locations, respectively, of three different ones of said n-type legs.

35. The multistage thermoelectric cooler of claim 31, wherein said p and n-type thermoelectric materials comprise, respectively, p and n-type Bi₂Te₃-based alloys.

36. A method of fabricating a multistage thermoelectric cooler, comprising

forming two templates each having a plurality of channels therein,

filling the channels of one of the templates with a p-type thermoelectric material and those of the other with an n-type thermoelectric material so as to form p and n-type legs having shapes of those channels, and

bonding the templates together so as to form contacts between said p-type and n-type legs in a cross-bar configuration pattern.

37. The method of claim 36, wherein said filling step comprises pressing said thermoelectric materials in a softened state into said channels.

38. The method of claim 36, further comprising polishing a top surface of said p-type and n-type legs.

39. The method of claim 36, further comprising forming Ohmic contacts on a portion of any of said p-type or n-type legs prior to said bonding step.

40. The method of claim 39, wherein said Ohmic contacts are formed by any of electrodeposition or sputtering.

41. The method of claim 36, further comprising removing said templates subsequent to said bonding step so as to release said bonded p and n-type legs as a multistage cooler.

42. The method of claim 36, further comprising attaching said multistage cooler to a support substrate.

43. The method of claim 36, further comprising forming said channels so as to have a length in a range of about 20 microns to about 1 millimeter, a width in a range of about 20 microns to about 1 millimeter, and a depth in a range of about 1 micron to about 1 millimeter.

44. The method of claim 36, wherein the templates comprise silicon substrates in which the channels are formed by reactive ion etching.

45. A method of fabricating a multistage thermoelectric cooler, comprising

depositing a layer of a thermoelectric material on a substrate,

forming a patterned mask on said thermoelectric layer to provide exposed and unexposed portions of said layer,

introducing dopant ions of a p- or n-type into said exposed portions to generate p-type or n-type thermoelectric legs of said multistage cooler.

46. The method of claim 45, wherein the step of introducing dopant ions comprises implanting or diffusing the ions into the exposed portions.

47. The method of claim 45, further comprising replacing said patterned mask with another to cover portions in which said legs are formed and expose selected other portions of said layer.

48. The method of claim 47, further comprising introducing dopant ions of a different type into said exposed portions to form legs of a different dopant type in said layer.

49. The method of claim 48, further comprising removing said mask and etching away undoped portions of said thermoelectric layer.

50. The method of claim 49, further comprising etching away the substrate so as to generate said thermoelectric cooler.

51. A cooling device, comprising

a thermoelectric cooler providing one cooling stage,

a multistage thermoelectric cooler thermally coupled to said thermoelectric cooler to provide additional cooling stages,

said multistage thermoelectric cooler comprising a plurality of legs formed of a p-type thermoelectric material and a plurality of legs formed of an n-type thermoelectric material, said p-type and n-type legs being thermally and electrically linked in a cross-bar configuration to provide a plurality of cascading cooling stages,

wherein said p-type and n-type legs are disposed in a common plane.