Semiconductor with silver patterns having pattern segments
View Patent ↗A photovoltaic cell and method of forming the cell includes providing an electroformed metallic article having a plurality of electroformed elements that form a free-standing, unitary piece. The metallic article has gridlines that are spaced apart at a pitch P M . A semiconductor substrate has a top surface with a plurality of silver, where at least one of the silver patterns comprises pattern segments spaced apart at a pitch P S . The pattern segments have a length L S defined by the equation L S =P M −k*P S /2, k being a value from 1.0 to 1.4. The metallic article is coupled to the semiconductor substrate, in which a first electroformed element in the plurality of electroformed elements is coupled to a first silver pattern in the plurality of silver patterns.
1. A method of forming a photovoltaic cell, the method comprising:
providing an electroformed metallic article having a plurality of electroformed elements that form a free-standing, unitary piece comprising gridlines that are spaced apart at a pitch P M ;
providing a semiconductor substrate having a top surface with a plurality of silver patterns comprising silver, wherein at least one of the silver patterns comprises pattern segments, the pattern segments being spaced apart at a pitch P S and having a length L S defined by an equation L S =P M −k*P S /2, k being a value from 1.0 to 1.4; and
coupling the metallic article to the semiconductor substrate, the coupling comprising coupling a first electroformed element in the plurality of electroformed elements to a first silver pattern in the plurality of silver patterns.
2. The method of claim 1 wherein the length L S is along a path intersected by one of the gridlines.
3. The method of claim 1 , wherein the pattern segments are configured in a discontinuous linear arrangement.
4. The method of claim 3 wherein the discontinuous linear arrangement comprises the pattern segments having ends separated by a gap that is less than or equal to 1.5 mm.
5. The method of claim 1 wherein k is based on a junction sheet resistivity of the semiconductor substrate.
6. The method of claim 5 wherein the junction sheet resistivity is approximately 75 ohms/square, and k is 1.2.
7. The method of claim 1 wherein the gridlines comprise:
bus bars spaced at the pitch P M ; and
a support member intersecting the bus bars, wherein the bus bars electrically couple the support member to a cell interconnect.
8. The method of claim 7 wherein the cell interconnect is an electroformed element in the plurality of electroformed elements.
9. The method of claim 7 wherein the gridlines comprise at least ten bus bars.
10. The method of claim 7 wherein each bus bar has an electroformed cross-sectional area and each of the pattern segments has a segment cross-sectional area;
wherein the electroformed cross-sectional area plus the segment cross-sectional area equals a total conduit cross-sectional area; and
wherein the electroformed cross-sectional area comprises a majority of the total conduit cross-sectional area.
11. The method of claim 10 wherein the segment cross-sectional area is less than or equal to 800 μm 2 .
12. The method of claim 10 wherein the segment cross-sectional area comprises a height less than or equal to 15 μm and a width less than or equal to 60 μm.
13. The method of claim 10 wherein the electroformed cross-sectional area is configured for distributed current collection and the segment cross-sectional area is configured for localized current collection.
14. The method of claim 1 wherein the first silver pattern provides a first bond area for the coupling, and wherein the first silver pattern is coupled to a perimeter of the metallic article.
15. The method of claim 14 wherein the first bond area has a first bond length, the first bond length being at least 200 μm greater than a width of the first electroformed element.
16. The method of claim 14 further comprising coupling a second electroformed element in the plurality of electroformed elements to a second silver pattern in the plurality of silver patterns, the second silver pattern providing a second bond area for the coupling, wherein the second silver pattern is away from the perimeter of the metallic article; and
wherein the first bond area is greater than the second bond area.
17. The method of claim 16 wherein the second bond area has a second bond length, the second bond length being at least 200 μm greater than a width of the second electroformed element.
18. The method of claim 16 further comprising a plurality of auxiliary lines coupling the second silver pattern to a plurality of the pattern segments, wherein the auxiliary lines comprise silver.
19. A photovoltaic cell comprising:
an electroformed metallic article having a plurality of electroformed elements that form a free-standing, unitary piece comprising gridlines that are spaced apart at a pitch P M ; and
a semiconductor substrate coupled to the metallic article, the semiconductor substrate having a top surface with a plurality of silver patterns comprising silver, wherein a first electroformed element in the plurality of electroformed elements is coupled to a first silver pattern in the plurality of silver patterns;
wherein at least one of the silver patterns comprises pattern segments, the pattern segments being spaced apart at a pitch P S and having a length L S defined by an equation L S =P M −k*P S /2, k being a value from 1.0 to 1.4.
20. The photovoltaic cell of claim 19 , wherein the pattern segments are configured in a discontinuous linear arrangement.
21. The photovoltaic cell of claim 20 wherein the discontinuous linear arrangement comprises the pattern segments having ends separated by a gap that is less than or equal to 1.5 mm.
22. The photovoltaic cell of claim 19 wherein k is based on a junction sheet resistivity of the semiconductor substrate, wherein the junction sheet resistivity is approximately 75 ohms/square, and k is 1.2.
23. The photovoltaic cell of claim 19 wherein the gridlines comprise:
bus bars spaced at the pitch P M ; and
a support member intersecting the bus bars, wherein the bus bars electrically couple the support member to a cell interconnect;
wherein each bus bar has an electroformed cross-sectional area, and each of the pattern segments has a segment cross-sectional area; wherein the electroformed cross-sectional area plus the segment cross-sectional area equals a total conduit cross-sectional area; and
wherein the electroformed cross-sectional area comprises a majority of the total conduit cross-sectional area.
24. The photovoltaic cell of claim 23 wherein the segment cross-sectional area comprises a height less than 15 μm and a width less than 60 μm.
25. The photovoltaic cell of claim 19 wherein the first silver pattern provides a first bond area for the coupling, and wherein the first silver pattern is coupled to a perimeter of the metallic article.
26. The photovoltaic cell of claim 25 wherein the first bond area has a first bond length, the first bond length being at least 200 μm greater than a width of the first electroformed element.
27. The photovoltaic cell of claim 25 further comprising coupling a second electroformed element in the plurality of electroformed elements to a second silver pattern in the plurality of silver patterns, the second silver pattern providing a second bond area for the coupling, wherein the second silver pattern is away from the perimeter of the metallic article; and
wherein the first bond area is greater than the second bond area.
28. The photovoltaic cell of claim 27 further comprising a plurality of auxiliary lines coupling the second silver pattern to a plurality of the pattern segments, wherein the auxiliary lines comprise silver.