Wire-based metallization and stringing for solar cells
Wire-based metallization and stringing techniques for solar cells, and the resulting solar cells, modules, and equipment, are described. In an example, a string of solar cells includes a plurality of back-contact solar cells, wherein each of the plurality of back-contact solar cells includes P-type and N-type doped diffusion regions. A plurality of conductive wires is disposed over a back surface of each of the plurality of solar cells, wherein each of the plurality of conductive wires is substantially parallel to the P-type and N-type doped diffusion regions of each of the plurality of solar cells. One or more of the plurality of conductive wires adjoins a pair of adjacent solar cells of the plurality of solar cells and has a relief feature between the pair of adjacent solar cells.
1 . A method of fabricating a solar cell string, the method comprising:
positioning at least two solar cells adjacent to one another, wherein emitter regions of a first solar cell are in alignment with emitter regions of a second solar cell;
positioning an intervening structure between the first and second solar cells in a location outside of a footprint of the first and second solar cells;
positioning a plurality of wires in alignment with the emitter regions of the first and second solar cells;
performing a thermocompression process to bond the plurality of wires to the emitter regions of the first and second solar cells, the thermocompression bonding performed in the presence of the intervening structure, wherein one or more of the plurality of wires has a bottom surface with a flat region, rounded side surfaces, and a top surface with a flat region between the first and second solar cells in the location outside of a footprint of the first and second solar cells;
removing the intervening structure from between the first and second solar cells subsequent to performing the thermocompression process;
positioning an interconnect material in contact with the plurality of wires, wherein the interconnect material is positioned between the first and second solar cells; and
performing a welding and cutting process on the interconnect material and the plurality of wires.
2 . A method of fabricating a solar cell string, the method comprising:
positioning at least two solar cells adjacent to one another, wherein the positioning comprising positioning a second solar cell in an orientation 180 degrees rotated to a first solar cell;
positioning an intervening structure between the first and second solar cells in a location outside of a footprint of the first and second solar cells;
positioning a plurality of wires in alignment with emitter regions of the first and second solar cells;
performing a thermocompression process to bond the plurality of wires to the emitter regions of the first and second solar cells, the thermocompression bonding performed in the presence of the intervening structure, wherein one or more of the plurality of wires has a bottom surface with a flat region, rounded side surfaces, and a top surface with a flat region between the first and second solar cells in a location outside of the footprint of the first and second solar cells;
removing the intervening structure from between the first and second solar cells subsequent to performing the thermocompression process;
bending the plurality of wires at locations in between the first and second solar cell; and
performing a cutting process on the plurality of wires.
3 . A method of fabricating a string of solar cells, the method comprising:
providing a plurality of solar cells, wherein each of the plurality of solar cells includes P-type and N-type doped diffusion regions;
positioning an intervening structure between adjacent ones of the plurality of solar cells in a location outside of a footprint of the plurality of solar cells;
disposing a plurality of conductive wires over a back surface of each of the plurality of solar cells, wherein each of the plurality of conductive wires is substantially parallel to the P-type and N-type doped diffusion regions of each of the plurality of solar cells;
performing a thermocompression process to bond the plurality of conductive wires to the P-type and N-type doped diffusion regions of the plurality of solar cells, the thermocompression bonding performed in the presence of the intervening structure, wherein one of the plurality of conductive wires adjoins a pair of adjacent solar cells of the plurality of solar cells and has a bottom surface with a flat region, rounded side surfaces, and a top surface with a flat region between the pair of adjacent solar cells in a location outside of a footprint of the pair of adjacent solar cells; and
removing the intervening structure from between the adjacent ones of the plurality of solar cells subsequent to performing the thermocompression process.
4 . The method of claim 3 , wherein the further comprising:
forming a relief feature that comprises an additional material connecting the plurality of conductive wires adjoining the pair of adjacent solar cells.
5 . The method of claim 4 , wherein the additional material comprises a material selected from the group consisting of a ribbon, wire and foil.
6 . The method of claim 4 , wherein the relief feature comprises a region selected from the group consisting of a solder region, weld region and a cut region.
7 . The method of claim 4 , wherein the relief feature comprises an approximately 90 degree angle to the plurality of conductive wires.
8 . The method of claim 4 , wherein the relief feature comprises an angle greater than or less than approximately 90 degrees to the plurality of conductive wires.
9 . The method of claim 4 , wherein the relief feature comprises a first bend relief feature having a bend orientation, the bend orientation of the first bend relief feature in plane to the plurality of conductive wires.
10 . The method of claim 9 , further comprising a second bend relief feature having a bend orientation, the bend orientation of the second bend relief feature in plane to the plurality of conductive wires.
11 . The method of claim 10 , wherein the bend orientation of the second bend relief feature is in the same direction as the bend orientation of the first bend relief feature.
12 . The method of claim 10 , wherein the bend orientation of the second bend relief feature is in an opposite direction as the bend orientation of the first bend relief feature.
13 . The method of claim 10 , wherein the relief feature comprises a third bend relief feature having a bend orientation, the bend orientation of the third bend relief feature in plane to the plurality of conductive wires.
14 . The string of solar cells of claim 13 , wherein the bend orientation of the first, second and third bend relief feature are in an alternating direction.
15 . The method of claim 3 , wherein one side edge of the plurality of solar cells are connected by at least one conductive wire and another, opposite, side edge of the plurality of solar cells is open.
16 . The method of claim 3 , wherein the intervening structure is
a shim, the shim on one side of the one of the plurality of conductive wires adjacent to the plurality of solar cells.
17 . The method of claim 16 , wherein the shim comprises a material selected from the group consisting of a silicon shim, a high temperature ceramic and a cloaking material.
18 . The method of claim 3 , wherein the P-type doped diffusion regions of a first solar cell of the plurality of solar cells is directly in alignment with the P-type doped diffusion regions a second solar cell of the plurality of solar cells.
19 . The method of claim 3 , wherein the P-type doped diffusion regions of a first solar cell of the plurality of solar cells is directly in alignment with the N-type doped diffusion regions a second solar cell of the plurality of solar cells.
20 . The method of claim 3 , wherein the plurality of solar cells comprise a plurality of back-contact solar cells.