Closely Spaced, High-Aspect Extruded Gridlines

• US 20080102558A1
• Filed: 11/01/2006
• Published: 05/01/2008
• Est. Priority Date: 11/01/2006
• Status: Active Grant

• Current Assignee: SolarWorld Industries GmbH
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Fork, David K., Zimmermann, Thomas S.
• Granted Patent: US 8,322,025 B2
• Time in Patent Office: Days
• US Class Current: 438/98
• CPC Class Codes: B29C 48/0016 using a plurality of extrusion dies
• CPC Class Codes: B29C 48/05 Filamentary, e.g. strands
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/09 Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
• CPC Class Codes: B29C 48/12 Articles with an irregular circumference when viewed in cross-section, e.g. window profiles
• CPC Class Codes: B29C 48/19 the layers being joined at their edges
• CPC Class Codes: B29C 48/21 the layers being joined at their surfaces
• CPC Class Codes: B29C 48/307 specially adapted for bringing together components, e.g. melts within the die
• CPC Class Codes: H01L 31/022425 for solar cells
• CPC Class Codes: H01M 14/005 Photoelectrochemical storage cells light sensitive devices H01G9/20, semiconductors sensitive to light H01L31/00
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y10T 29/5313 Means to assemble electrical device
• CPC Class Codes: Y10T 29/532 Conductor

Abstract

Closely spaced, high aspect-ratio gridline structures are formed on the surface of a substrate using two or more co-extrusion heads that co-extrude gridline material and sacrificial material such that the deposited gridline material is compressed between opposing portions of the sacrificial material. The co-extrusion heads include three-channel cavity structures that converge to a relatively small outlet orifice that dispenses the gridline material with relatively fine features and a relatively high aspect ratio. The outlet orifices of the co-extrusion heads are disposed in a staggered arrangement such that gridlines extruded from the first co-extrusion head are disposed between two gridlines extruded from the second co-extrusion head. Photovoltaic cells are produced with metal gridlines formed in this manner.

Claims

1. A method for forming a plurality of closely spaced high-aspect ratio gridline structures on a substrate, the method comprising:

disposing first and second co-extrusion heads adjacent to a surface of the substrate such that first outlet orifices of the first co-extrusion head define a first line extending in a first direction, and second outlet orifices of the second co-extrusion head define a second line that is separated from and parallel to the first line;

moving the first and second co-extrusion heads relative to the substrate in a second direction while extruding gridline material and a sacrificial material through each of the first and second outlet orifices such that said gridline material extruded from each of the first and second outlet orifices forms an associated high-aspect ratio gridline structure, and said sacrificial material extruded from each of the first and second outlet orifices forms associated first and second sacrificial material portions respectively disposed on opposing sides of said associated high-aspect ratio gridline structure,

wherein the first said outlet orifices and the second said outlet orifices are disposed in a staggered arrangement such that a first said high-aspect ratio gridline structure extruded from the first co-extrusion head is disposed between second and third said high-aspect ratio gridline structures extruded from the second co-extrusion head.

2. The method of claim 1, wherein disposing the first and second co-extrusion heads comprises fixedly mounting the first and second co-extrusion heads on an extrusion device coupled to a source of the sacrificial material and a source of the gridline material.

3. The method of claim 2, wherein moving the first and second co-extrusion heads relative to the substrate comprises fixedly mounting the substrate and moving the extrusion device over the surface of the substrate.

4. The method of claim 2, wherein moving the first and second co-extrusion heads relative to the substrate comprises fixedly mounting the extrusion device and moving the substrate under the extrusion device.

5. The method of claim 1, further comprising at least one of heating the gridline and sacrificial materials prior to extrusion, cooling the substrate during extrusion of the gridline and sacrificial materials, and curing the extruded gridline and sacrificial materials.

6. The method of claim 1, wherein extruding the gridline material and the sacrificial material through each of the first and second outlet orifices comprises injecting the gridline material into a central channel of a three-channel cavity defined in one of said first and second co-extrusion heads while injecting the sacrificial material into opposing first and second side channels of the three-channel cavity, wherein the central channel and first and second side channels communicate with an associated outlet orifice.

7. The method of claim 6,

wherein the three-channel cavity is defined between a first plate portion having a first inlet port disposed over the central channel of the three-channel cavity, and a second plate portion having second and third inlet ports respectively disposed over the first and second side channels of the three-channel cavity, and

wherein extruding the gridline material and the sacrificial material comprises forcing the gridline material through the first inlet port into the central channel while forcing the sacrificial material through the second and third inlet ports into the first and second side channels, respectively.

8. An apparatus for forming a plurality of high-aspect ratio gridline structures on a substrate, the apparatus comprising:

first and second co-extrusion heads positioned over a surface of the substrate such that first outlet orifices of the first co-extrusion head define a first line extending is a first direction, and second outlet orifices of the second co-extrusion head define a second line that is parallel to the first line;

means for moving the first and second co-extrusion heads relative to the substrate in a second direction while causing the first and second co-extrusion heads to extrude gridline material and a sacrificial material through each of the first and second outlet orifices such that said gridline material extruded from each of the first and second outlet orifices forms an associated gridline structure of said plurality of high-aspect ratio gridline structures, and said sacrificial material extruded from each of the first and second outlet orifices forms associated first and second sacrificial material portions respectively disposed on opposing sides of said associated gridline structure,

wherein the first and second co-extrusion heads are positioned such that the first said outlet orifices and the second said outlet orifices are disposed in a staggered arrangement such that a first said gridline structure extruded from the first co-extrusion head is disposed between second and third said gridline structures extruded from the second co-extrusion head.

9. The apparatus of claim 8, further comprising an extrusion device coupled to a source of the sacrificial material and a source of the gridline material, wherein the first and second co-extrusion heads are fixedly mounted on the extrusion device.

10. The apparatus of claim 9, wherein said means for moving comprises means for fixedly securing the substrate, and means for moving the extrusion device over the surface of the substrate.

11. The apparatus of claim 9, wherein said means for moving comprises means for fixedly securing the extrusion device, and means for moving the substrate under the extrusion device.

12. The apparatus of claim 8, further comprising at least one of means for heating the gridline and sacrificial materials before extrusion, means for cooling the substrate during extrusion of the gridline and sacrificial materials, and means for curing the extruded gridline and sacrificial materials.

13. The apparatus of claim 8,

wherein each of the first and second co-extrusion heads comprises a plurality of three-channel cavities, each of the three-channel cavities including a central channel and opposing first and second side channels, wherein the central channel and first and second side channels communicate with an associated outlet orifice,

and wherein the means for causing the first and second co-extrusion heads to extrude gridline material and a sacrificial material includes means for injecting the gridline material into the central channel of each three-channel cavity while injecting the sacrificial material into the first and second side channels of said three-channel cavity.

14. The apparatus of claim 13,

wherein the three-channel cavity is defined between a first plate portion having a first inlet port disposed over the central channel of the three-channel cavity, and a second plate portion having second and third inlet ports respectively disposed over the first and second side channels of the three-channel cavity, and

wherein said means for injecting the gridline material and the sacrificial material comprises means for forcing the gridline material through the first inlet port into the central channel while forcing the sacrificial material through the second and third inlet ports into the first and second side channels, respectively.

15. A method for manufacturing a photovoltaic device, the method including:

forming a semiconductor substrate including a p-type region defining a first surface, and an n-type region defining a second surface; and

forming a plurality of closely spaced high-aspect ratio metal gridlines on a selected one of the first and second surfaces of the semiconductor substrate, wherein forming the metal gridlines comprises;

disposing first and second co-extrusion heads adjacent to the selected surface of the substrate such that first outlet orifices of the first co-extrusion head define a first line extending in a first direction, and second outlet orifices of the second co-extrusion head define a second line that is separated from and parallel to the first line; and

moving the first and second co-extrusion heads relative to the semiconductor substrate in a second direction while extruding metal material and a sacrificial material through each of the first and second outlet orifices such that said metal material extruded from each of the first and second outlet orifices forms an associated high-aspect ratio metal gridline, and said sacrificial material extruded from each of the first and second outlet orifices forms associated first and second sacrificial material portions respectively disposed on opposing sides of said associated high-aspect ratio metal gridline,

wherein the first said outlet orifices and the second said outlet orifices are disposed in a staggered arrangement such that a first said high-aspect ratio metal gridline extruded from the first co-extrusion head is disposed between second and third said high-aspect ratio metal gridlines extruded from the second co-extrusion head.

16. The method of claim 15, wherein disposing the first and second co-extrusion heads comprises fixedly mounting the first and second co-extrusion heads on an extrusion device coupled to a source of the sacrificial material and a source of the metal material.

17. The method of claim 15, further comprising at least one of cooling the substrate during extrusion of the materials, and curing the extruded materials.

18. The method of claim 15, wherein extruding the metal material and the sacrificial material through each of the first and second outlet orifices comprises injecting the metal material into a central channel of a three-channel cavity defined in one of said first and second co-extrusion heads while injecting the sacrificial material into opposing first and second side channels of the three-channel cavity, wherein the central channel and first and second side channels communicate with an associated outlet orifice.

19. The method of claim 18,

wherein the three-channel cavity is defined between a first plate portion having a first inlet port disposed over the central channel of the three-channel cavity, and a second plate portion having second and third inlet ports respectively disposed over the first and second side channels of the three-channel cavity, and

wherein extruding the metal material and the sacrificial material comprises forcing the metal material through the first inlet port into the central channel while forcing the sacrificial material through the second and third inlet ports into the first and second side channels, respectively.

20. The method of claim 15, further comprising:

forming a conductive contact layer on the first surface of the semiconductor substrate; and

connecting a first electrode to the metal gridlines, and a second electrode to the conductive contact layer.