Arrays of Ultrathin Silicon Solar Microcells

• US 20110277813A1
• Filed: 09/24/2009
• Published: 11/17/2011
• Est. Priority Date: 09/24/2008
• Status: Active Grant

• Current Assignee: Board of Trustees of The University of Illinois
• Original Assignee: Board of Trustees of The University of Illinois
• Inventors: Yoon, Jongseung, Baca, Alfred, Rockett, Angus A., Nuzzo, Ralph, Rogers, John A.
• Granted Patent: US 8,679,888 B2
• Time in Patent Office: Days
• US Class Current: 136/244
• CPC Class Codes: H01L 31/035281 Shape of the body
• CPC Class Codes: H01L 31/048 Encapsulation of modules
• CPC Class Codes: H01L 31/0508 the interconnection means having a particular shape
• 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: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/1896 for thin-film semiconductors
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

Provided are solar cells, photovoltaics and related methods for making solar cells, wherein the solar cell is made of ultrathin solar grade or low quality silicon. In an aspect, the invention is a method of making a solar cell by providing a solar cell substrate having a receiving surface and assembling a printable semiconductor element on the receiving surface of the substrate via contact printing. The semiconductor element has a thickness that is less than or equal to 100 μm and, for example, is made from low grade Si.

Claims

1. A method of making a solar cell, said method comprising the steps of:

providing a solar cell substrate having a receiving surface; and

assembling a printable semiconductor element on said receiving surface of said substrate via contact printing;

wherein said printable semiconductor element comprises a semiconductor structure having a thickness that is less than or equal 100 μ

m, and said semiconductor structure comprises low grade Si.

2. The method of claim 1, wherein said thickness is selected from the range of 10 μ

m and 75 μ

m.

3. The method of claim 1, wherein said thickness is selected from the range of 15 μ

m and 40 μ

m.

4. The method of claim 1, wherein said thickness is less than 50 μ

m.

5. The method of claim 1, wherein said thickness is less than 25 μ

m.

6. The method of claim 1, wherein said printable semiconductor element comprises an array of microbars.

7. The method of claim 6, wherein said microbars have a thickness selected from the range of 0.1 μ

m and 30 μ

m, a length selected from the range of 0.5 mm to 5 cm, and a width selected from the range of 5 μ

m and 1 mm.

8. The method of claim 1, wherein said solar cell has an optical transparency that is greater than or equal to 40% in at least a portion of the visible light spectrum.

9. The method of claim 1, wherein the solar cell is bendable or flexible.

10. The method of claim 1, wherein said printable semiconductor element is assembled on said receiving surface via dry transfer contact printing.

11. The method of claim 1 wherein said printable semiconductor element is assembled on said receiving surface using a conformable transfer device.

12. The method of claim 1 wherein said assembling step comprises:

providing a conformable transfer device having a contact surface;

establishing conformal contact between an external surface of said printable semiconductor element and said contact surface of said conformable transfer device, wherein said conformal contact bonds said printable semiconductor element to said contact surface;

contacting said printable semiconductor element bonded to said contact surface and said receiving surface of said solar cell substrate; and

separating said printable semiconductor element and said contact surface of said conformable transfer device, thereby assembling said printable semiconductor element on said receiving surface of said solar cell substrate.

13. The method of claim 12 further comprising the steps of:

providing an array of printable semiconductor elements on a single Si wafer; and

repeating said assembling steps of claim 12 in a step and repeat fashion to transfer said printable semiconductor elements from said single Si wafer to said receiving surface.

14. The method of claim 13, wherein said array of printable semiconductor elements on a single Si wafer has a donating surface density and said printed semiconductor elements on said receiving surface has a printed surface density, and said donating surface density is at least ten times greater than said printed surface density.

15. The method of claim 13, wherein said large area receiving surface has a surface area that is greater than 500 cm².

16. The method of claim 15, wherein said solar cell is flexible or bendable.

17. The method of claim 1, wherein the low-grade Si comprises Si having a defect density that is greater than or equal to 10¹⁶ per cm³.

18. The method of claim 1, wherein said semiconductor element on said receiving surface has a coverage density selected from the range of 5 elements/mm to 100 elements/mm.

19. The method of claim 1, wherein said semiconductor structure is patterned in a bulk Si wafer.

20. The method of claim 1, wherein said solar cell has an efficiency that is greater than or equal to 15%.

31. The method of claim 1, wherein said printable semiconductor element comprises monocrystalline Si.

32. The method of claim 1 further comprising:

electrically interconnecting a plurality of said solar cells to obtain a module of solar cells having a high voltage output, wherein said high voltage output is greater than or equal to 1 V.

33. The method of claim 32, wherein said module is flexible or bendable.

34. The method of claim 32, wherein said module comprises at least 30 solar cells electrically connected in series to provide a voltage output that is greater than or equal to 10 V.

35. The method of claim 34, wherein said module has a base area footprint that is less than or equal to 25 cm².

36. A silicon solar microcell made by the method of claim 1.

21. A method of making an ultra-thin microscale solar cell, said method comprising:

providing a solar cell substrate having a receiving surface;

providing a plurality of semiconductor elements on a donor substrate;

transferring at least a portion of said semiconductor elements from said donor substrate to said receiving surface;

wherein said transferred semiconductor elements have a thickness that is less than 100 μ

m and comprise low grade Si.

22. The method of claim 21, wherein said transferring step comprises:

providing a conformable transfer device having a contact surface;

establishing conformal contact between an external surface of said semiconductor element and said contact surface of said conformable transfer device, wherein said conformal contact bonds said printable semiconductor element to said contact surface;

contacting said semiconductor element bonded to said contact surface and said receiving surface of said device substrate; and

separating said semiconductor element and said contact surface of said conformable transfer device, thereby assembling said semiconductor element on said receiving surface of said solar cell substrate.

23. The method of claim 21, wherein said plurality of semiconductor elements on a donor substrate comprises a Si wafer having a patterned surface.

24. The method of claim 23, wherein said patterned surface comprises a plurality of Si microbar cells that are at least partially undercut.

25. The method of claim 23, wherein said Si wafer is reused after said semiconductor elements are transferred to said receiving surface.

26. The method of claim 21, wherein said semiconductor elements are bonded to said receiving substrate by an adhesive.

27. The method of claim 21, wherein said semiconductor elements have a thickness that is less than 20 μ

m.

28. The method of claim 21, wherein said receiving surface has a surface area that is greater than or equal to 1 m².

29. The method of claim 23, wherein greater than 60% by weight of said silicon wafer is transferred to said solar cell substrate.

30. The method of claim 29, wherein said solar cell is flexible or bendable.

37. An ultrathin silicon solar microcell comprising:

a solar cell substrate; and

a plurality of semiconductor elements supported by said substrate, wherein said semiconductor elements are made from low grade Si and have a thickness that is less than or equal to 100 μ

m.

38. A silicon solar module comprising a plurality of microcells of claim 37, wherein the microcells are electrically connected in series to provide a high voltage output.

39. The module of claim 38 comprising at least 30 microcells and having a voltage output that is greater than or equal to 10 V.

40. The module of claim 39 having a base area footprint that is less than or equal to 25 cm².