INTEGRATION OF EPITAXIAL LIFT-OFF SOLAR CELLS WITH MINI-PARABOLIC CONCENTRATOR ARRAYS VIA PRINTING METHOD

• US 20160329457A1
• Filed: 01/15/2015
• Published: 11/10/2016
• Est. Priority Date: 01/15/2014
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Fan, Dejiu, Forrest, Stephen R., Lee, Kyusang, Zimmerman, Jeramy
• Granted Patent: US 10,069,033 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01L 31/03046 including ternary or quaternary compounds, e.g. GaAlAs, InGaAs, InGaAsP
• CPC Class Codes: H01L 31/035281 Shape of the body
• CPC Class Codes: H01L 31/0547 comprising light concentrating means of the reflecting type, e.g. parabolic mirrors, concentrators using total internal reflection
• CPC Class Codes: H01L 31/0687 Multiple junction or tandem solar cells
• CPC Class Codes: H01L 31/0693 the devices including, apart from doping material or other impurities, only AIIIBV compounds, e.g. GaAs or InP solar cells
• CPC Class Codes: H01L 31/1892 methods involving the use of temporary, removable substrates
• CPC Class Codes: H01L 31/1896 for thin-film semiconductors
• CPC Class Codes: Y02E 10/52 PV systems with concentrators
• CPC Class Codes: Y02E 10/544 Solar cells from Group III-V materials
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

There is disclosed a method of preparing a photovoltaic device. In particular, the method comprises integrating epitaxial lift-off solar cells with mini-parabolic concentrator arrays via a printing method. Thus, there is disclosed a method comprising providing a growth substrate; depositing at least one protection layer on the growth substrate; depositing at least one sacrificial layer on the protection layer; depositing at least one photoactive cell on the sacrificial layer; etching a pattern of at least two parallel trenches that extend from the at least one photoactive cell to the sacrificial layer; depositing a metal on the at least one photoactive cell; bonding said metal to a host substrate; and removing the sacrificial layer with one or more etch steps. The host substrate can be a siloxane, which when rolled, can form a stamp used to integrate solar cells into concentrator arrays. There are also disclosed a method of making a growth substrate and the growth substrate made therefrom.

Claims

1. A non-destructive method for performing an epitaxial lift-off, comprising:

providing a growth substrate;

depositing at least one protection layer on the growth substrate;

depositing at least one sacrificial layer on the protection layer;

depositing a photoactive cell on the sacrificial layer;

depositing a metal mask on the at least one photoactive cell;

performing a first etch step through said metal mask to form a pattern in the photoactive cell, wherein said pattern extends to the sacrificial layer; and

removing the sacrificial layer with one or more second etch steps.

2. The method of claim 1, wherein the growth substrate comprises GaAs or InP.

3. The method of claim 1, wherein the at least one protection layer is lattice matched with the growth substrate.

4. The method of claim 3, wherein the at least one protection layer is selected from GaAs, InP, InGaAs, AlInP, GaInP, InAs, InSb, GaP, AlP, GaSb, AlSb, and combinations thereof.

5. The method of claim 4, wherein the at least one protection layer comprises at least three alternating layers of GaAs and InGaP.

6. The method of claim 1, wherein the at least one protection layer is deposited by at least one process chosen from gas source molecular beam epitaxy (GSMBE), metallo-organic chemical vapor deposition (MOCVD), hydride vapor phase epitaxy (HVPE), solid source molecular beam epitaxy (SSMBE), and chemical beam epitaxy

7. The method of claim 1, wherein the at least one protection layer comprises a buffer layer, an etch-stop layer, or combinations thereof.

8. The method of claim 1, wherein the one or more second etch steps comprise contacting the sacrificial layer with a wet etchant, a dry etchant, or combinations thereof.

9. The method of claim 8, wherein said wet etchant comprises HF, H₃PO₄, HCl, H₂SO₄, H₂O₂, HNO₃, C₆H₈O₇, and combinations thereof, including combinations with H₂O.

10. The method of claim 8, wherein said dry etchant comprises reactive ion etching (RIE) with a plasma.

11. The method of claim 1, wherein said first etch step comprises reactive ion etching (RIE) with a plasma.

12. The method of claim 8, wherein the sacrificial layer comprises AlAs, and the one or more second etch steps comprise contacting said AlAs with HF.

13. The method of claim 1, wherein the etched pattern comprises two or more parallel trenches that have been etched in the at least one photoactive cell.

14. The method of claim 1, wherein the substrate comprises GaAs and wherein the protective layer scheme comprises GaAs Substrate /InAlP/InGaP/GaAs/InAlP/AlAs.

15. The method of claim 1, wherein the at least one photoactive cell comprises a single junction or multi-junction cell.

16. A growth structure for epitaxial lift-off, comprising:

a growth substrate;

at least one protection layer on the growth substrate;

at least one sacrificial layer on the protection layer;

at least one photoactive cell on the sacrificial layer; and

at least one pattern that has been etched from photoactive cell to the sacrificial layer, wherein the etched pattern comprises two or more parallel trenches.

17. The growth structure of claim 16, wherein the growth substrate comprises GaAs and the at least one protective layer is selected from InP, InGaAs, AlInP, GaInP, InAs, InSb, GaP, AlP, GaSb, AlSb and combinations thereof.

18. The growth structure of claim 17, wherein the at least one protection layer comprises at least three alternating layers of GaAs and InGaP.

19. The growth structure of claim 16, wherein the sacrificial layer comprises AlAs.

20. The growth structure of claim 16, wherein the photoactive cell comprises active semiconductor layers for forming a photovoltaic device.

21. The growth structure of claim 16, wherein the at least one photoactive cell comprises a single junction or multi-junction cell.

22. The growth structure of claim 16, wherein the at least one protection layer comprises a buffer layer, an etch-stop layer, or combinations thereof.

23. The growth structure of claim 16, wherein the substrate comprises GaAs and wherein the protective layer scheme comprises GaAs Substrate /InAlP/InGaP/GaAs/InAlP/AlAs.

24. A method of preparing a photovoltaic device structure comprising:

providing a growth substrate;

depositing at least one protection layer on the growth substrate;

depositing at least one sacrificial layer on the protection layer;

depositing at least one photoactive cell on the sacrificial layer;

etching a pattern of at least two parallel trenches that extend from the at least one photoactive cell to the sacrificial layer, wherein said etching causes the surface of the structure to form alternating trenches that extend to the sacrificial layer and plateaus that comprise said photoactive cells.

25. The method of claim 24, further comprising depositing at least one metal on the at least one photoactive cell and bonding said photoactive cells located on the plateaus to a host substrate.

26. The method of claim 24, wherein said bonding comprises a direct attachment method selected from cold-welding, thermally assisted cold-welding, or thermo-compression bonding.

27. The method of claim 25, wherein said host substrate comprises an elastomeric material that has been metalized with at least one metal chosen from Au, Ag, Pt, Pd, Ni, and Cu.

28. The method of claim 27, wherein said elastomeric material comprises polydimethylsiloxane.

29. The method of claim 27, wherein said elastomeric material is rolled into a circular stamp to expose said plateaus comprising parallel raised stripes of photoactive cells, which have been etched down to the sacrificial layer.

30. The method of claim 27, wherein said elastomeric material is stretched to up to twice its size prior to being rolled into a circular stamp.

31. The method of claim 30, further comprising etching away said sacrificial layer to form a thin-film solar cell stripe array on said circular stamp.

32. The method of claim 31, wherein said etching comprises contacting the sacrificial layer with a wet etchant, a dry etchant, or combinations thereof.

33. The method of claim 32, wherein said wet etchant comprises HF, H₃PO₄, HCl, H₂SO₄, H₂O₂, HNO₃, C₆H₈O₇, and combinations thereof, including combinations with H₂O.

34. The method of claim 32, wherein said dry etchant comprises reactive ion etching (RIE) with a plasma.

35. The method of claim 31, further comprising additional processing steps performed on the surface of the photoactive cell chosen from patterning, metalizing, and combinations.

36. The method of claim 31, further comprising mounting at least one cylindrical paraboloid mini-concentrator array to a linear transfer stage.

37. The method of claim 36, wherein the mini-concentrator array and solar cells each comprise contact pads for the cathode and anode on both the concentrator array and solar cells, wherein said contact pads are aligned and attached to each other under control of rotating speed of the elastomeric stamp and transferring speed of concentrator array.

38. The method of claim 36, wherein said cylindrical paraboloid mini-concentrator arrays comprise a plastic material or flexible metal having a thickness ranging from 25 to 100 μ

m.

39. The method of claim 38, wherein said plastic material comprises an amide that is molded under vacuum and heat to form cylindrical paraboloids mini-concentrator arrays, wherein said amide is metalized with at least one metal selected from Au, Ag, Pt, Pd, Ni, and Cu.

40. The method of claim 36, further comprising bonding the at least one photoactive cell located on the circular stamp to the cylindrical paraboloids mini-concentrator array to form an integrated, solar cell array.

41. The method of claim 40, wherein the cylindrical paraboloids mini-concentrator array has a parabolic trough design.

42. The method of claim 41, wherein the parabolic trough comprises a linear parabolic reflector that concentrates light onto the photoactive cell positioned along the focal line of the reflector.

43. The method of claim 40, wherein the photoactive cell and the linear parabolic reflector have the same radius of curvature.

44. The method of claim 24, further comprising depositing a metal mask on said photoactive cell prior to etching a pattern, wherein said etching a pattern comprises reactive ion etching (RIE) with a plasma through said metal mask.

45. The method of claim 24, wherein the sacrificial layer comprises AlAs.

46. The method of claim 24, further comprising cleaving said substrate into a plurality of rectangular and/or square segments prior to depositing said at least one protection layer.

47. The method of claim 46, wherein said substrate comprises a wafer.