Interdigitated Back Contact Silicon Solar Cells Fabrication Using Diffusion Barriers

• US 20110070676A1
• Filed: 11/24/2010
• Published: 03/24/2011
• Est. Priority Date: 09/09/2008
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Nakayashiki, Kenta, Xu, Baomin
• Granted Patent: US 9,054,237 B2
• Time in Patent Office: Days
• US Class Current: 438/57
• CPC Class Codes: H01L 31/022425 for solar cells
• CPC Class Codes: H01L 31/022441 Electrode arrangements specially adapted for back-contact solar cells
• CPC Class Codes: H01L 31/0682 back-junction, i.e. rearside emitter, solar cells, e.g. interdigitated base-emitter regions back-junction cells
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• 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

Interdigitated back contact (IBC) solar cells are produced by depositing spaced-apart parallel pads of a first dopant bearing material (e.g., boron) on a substrate, heating the substrate to both diffuse the first dopant into corresponding first (e.g., p+) diffusion regions and to form diffusion barriers (e.g., borosilicate glass) over the first diffusion regions, and then disposing the substrate in an atmosphere containing a second dopant (e.g., phosphorus) such that the second dopant diffuses through exposed surface areas of the substrate to form second (e.g., n+) diffusion regions between the first (p+) diffusion regions (the diffusion barriers prevent the second dopant from diffusion into the first (p+) diffusion regions). The substrate material along each interface between adjacent first (p+) and second (n+) diffusion regions is then removed (e.g., using laser ablation) such that elongated grooves, which extend deeper into the substrate than the diffused dopant, are formed between adjacent diffusion regions.

Claims

1. A method of fabricating an IBC solar cell, the method comprising:

diffusing a first dopant into a rear surface of a semiconductor substrate such that first and second spaced-apart diffusion regions of the substrate have a first doping concentration and extends a first depth into the substrate from the rear surface, and are separated by a third diffusion region having a second doping concentration and extending a second depth into the substrate from the rear surface; and

diffusing a second dopant into said third diffusion region such that said first dopant prevents diffusion of said second dopant into said first and second diffusion regions.

2. The method according to claim 1, wherein diffusing the first dopant comprises:

depositing spaced-apart pads of material containing boron onto the rear surface of substrate over said first and second diffusion regions; and

heating the substrate such that a first portion of the boron diffuses into said first and second diffusion regions through said rear surface, and a second portion of the boron forms borosilicate glass on said rear surface over said first and second diffusion regions.

3. The method according to claim 2, further comprising, after forming said borosilicate glass, disposing said substrate in a furnace containing POCl₃ at a temperature selected such that phosphorus is diffused into said third diffusion region and said borosilicate glass prevents diffusion of said n-type dopant into said first and second diffusion regions.

4. The method according to claim 1, further comprising forming a plurality of grooves into the rear surface of the substrate such that the first diffusion region is separated from the third diffusion region by a first groove, and the second diffusion region is separated from the third diffusion region by a second groove.

5. A method of fabricating an IBC solar cell, the method comprising:

depositing spaced-apart pads of a material containing a first dopant onto the rear surface of a semiconductor substrate over said first and second diffusion regions;

heating the substrate such that a first portion of the first dopant diffuses into said first and second diffusion regions through said rear surface, and a second portion of the first dopant is disposed in diffusion barrier structures that are form on said rear surface over said first and second diffusion regions during said heating, and

diffusing a second dopant into said third diffusion region,

wherein said diffusion barrier structures are formed prior to said second dopant diffusion such that said diffusion barrier structures prevent diffusion of said second dopant into said first and second diffusion regions during said second dopant diffusion.

6. The method according to claim 5,

wherein depositing said spaced-apart pads of said material comprises depositing material containing boron;

and

wherein heating the substrate comprises forming borosilicate glass on said rear surface over said first and second diffusion regions.

7. The method according to claim 6, further comprising, after forming said borosilicate glass, disposing said substrate in a furnace containing POCl₃ at a temperature selected such that phosphorus is diffused into said third diffusion region and said borosilicate glass prevents diffusion of said n-type dopant into said first and second diffusion regions.

8. The method according to claim 5, further comprising forming a plurality of grooves into the rear surface of the substrate such that the first diffusion region is separated from the third diffusion region by a first groove, and the second diffusion region is separated from the third diffusion region by a second groove.

9. A method of fabricating an IBC solar cell, the method comprising:

depositing spaced-apart pads of a material containing a first dopant onto the rear surface of a semiconductor substrate over said first and second diffusion regions;

heating the substrate such that a first portion of the first dopant diffuses into said first and second diffusion regions through said rear surface, and a second portion of the first dopant forms glass structures on said rear surface over said first and second diffusion regions, and

diffusing a second dopant into said third diffusion region such that said glass structures prevent diffusion of said second dopant into said first and second diffusion regions during said second dopant diffusion.

10. The method according to claim 9,

wherein depositing said spaced-apart pads of said material comprises depositing material containing boron;

and

wherein heating the substrate comprises forming borosilicate glass on said rear surface over said first and second diffusion regions.

11. The method according to claim 9, wherein diffusing said second dopant comprises disposing said substrate in a furnace containing POCl₃ at a temperature selected such that phosphorus is diffused into said third diffusion region and said glass structures prevent diffusion of Phosphorous from said POCl₃ into said first and second diffusion regions.

12. The method according to claim 9, further comprising forming a plurality of grooves into the rear surface of the substrate such that the first diffusion region is separated from the third diffusion region by a first groove, and the second diffusion region is separated from the third diffusion region by a second groove.