Method for forming structures in a solar cell

• US 9,478,694 B2
• Filed: 12/19/2014
• Issued: 10/25/2016
• Est. Priority Date: 04/21/2009
• Status: Expired due to Fees

• Current Assignee: Tetrasun, Inc. (First Solar Incorporated)
• Original Assignee: Tetrasun, Inc. (First Solar Incorporated)
• Inventors: Turner, Adrian B.
• Primary Examiner(s): Landau, Matthew
• Assistant Examiner(s): RAMPERSAUD, PRIYA M
• Application Number:
  US14/576,293
• Publication Number:
  US 20150104900A1
• Time in Patent Office: 676 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 2103/172 wherein at least one of the layers is non-metallic
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 2103/56 semiconducting semiconducting devices B23K2101/40
• CPC Class Codes: B23K 26/066 by using masks
• CPC Class Codes: B23K 26/073 Shaping the laser spot
• CPC Class Codes: B23K 26/083 Devices involving movement of the workpiece in at least one axial direction
• CPC Class Codes: B23K 26/36 Removing material B23K26/55, B23K26/57 take precedence
• CPC Class Codes: B23K 26/402 involving non-metallic material, e.g. isolators
• CPC Class Codes: H01L 31/022425 for solar cells
• CPC Class Codes: H01L 31/022433 Particular geometry of the grid contacts
• 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

Abstract

A conductive contact pattern is formed on a surface of solar cell by forming a thin conductive layer over at least one lower layer of the solar cell, and ablating a majority of the thin conductive layer using a laser beam, thereby leaving behind the conductive contact pattern. The laser has a top-hat profile, enabling precision while scanning and ablating the thin layer across the surface. Heterocontact patterns are also similarly formed.

Claims

1. A method comprising:

forming a contact pattern on a surface of a solar cell, the solar cell comprising a textured semiconductor substrate, the forming comprising;

forming at least one film layer over a lower layer of the solar cell, the at least one film layer comprising a material having an ablation threshold;

irradiating a first portion of the at least one film layer with a laser, without irradiating a second portion of the at least one film layer, the laser having an at least partially homogenized beam profile, and the irradiating ablating the entire first portion of the at least one film layer, leaving the second portion of the at least one film layer as the contact pattern, the laser being operated at a fluence near or at the ablation threshold of the material of the at least one film layer; and

wherein during the irradiating, the textured semiconductor substrate further homogenizes the at least partially homogenized beam profile to facilitate operating the laser at the fluence near or at the ablation threshold of the material of the at least one film layer.

2. The method of claim 1, wherein the at least partially homogenized beam profile comprises a non-Gaussian beam profile.

3. The method of claim 2, wherein the non-Gaussian beam profile comprises a non-Gaussian top hat beam profile.

4. The method of claim 1, wherein the textured semiconductor substrate comprises a texture having a size scale comparable to one or more spatial inhomogeneities in the at least partially homogenized beam profile.

5. The method of claim 4, wherein the textured semiconductor substrate comprises a random pyramid-shaped texture.

6. The method of claim 1, further comprising forming self-aligned metallization on the contact pattern.

7. The method of claim 1, wherein the material of the at least one film layer comprises a conductive material, and the contact pattern is a conductive contact pattern.

8. The method of claim 7, wherein the at least one film layer comprises at least one film layer of a plurality of film layers, the plurality of film layers comprising two or more different conductive materials.

9. The method of claim 7, wherein the conductive contact pattern comprises a plurality of conductive fingers having a width of approximately 50 μ

m or less.

10. The method of claim 1, wherein the material of the at least one film layer comprises a semiconductor material, and the contact pattern comprises a hetero-contact pattern.

11. The method of claim 10, wherein the semiconductor material further comprises a conductive dopant.

12. The method of claim 10, wherein the at least one film layer comprises at least one film layer of a plurality of film layers, the plurality of film layers comprising two or more different semiconductor materials.

13. The method of claim 10, wherein the hetero-contact pattern comprises a plurality of at least partially conductive fingers having a width of approximately 50 μ

m or less.

14. The method of claim 1, wherein the irradiating comprises projecting the at least partially homogenized laser beam through a mask.

15. The method of claim 14, wherein the mask shapes the laser beam into a beam with a regular polygon cross-section.

16. The method of claim 14, wherein mask shapes the laser beam into a beam with a regular polygon cross-section with a thin obstructed line running across the regular polygon cross-section.

17. The method of claim 14, wherein the irradiating comprises projecting the at least partially homogenized laser beam through multiple masks or a dynamically changing mask.

18. The method of claim 1, wherein the first portion of the film layer ablated by the at least partially homogenized laser beam comprises more than 80% of the film layer.