Laser beam shaping for foil-based metallization of solar cells
Approaches for foil-based metallization of solar cells and the resulting solar cells are described. For example, a method of fabricating a solar cell involves locating a metal foil above a plurality of alternating N-type and P-type semiconductor regions disposed in or above a substrate. The method also involves laser welding the metal foil to the alternating N-type and P-type semiconductor regions. The method also involves patterning the metal foil by laser ablating through at least a portion of the metal foil at regions in alignment with locations between the alternating N-type and P-type semiconductor regions. The laser welding and the patterning are performed at the same time.
1. A method of fabricating a solar cell, the method comprising:
forming a metal layer above a plurality of N-type and P-type semiconductor regions disposed above a substrate;
locating a metal foil above the metal layer;
laser welding a first portion of the metal foil to the metal layer, wherein the laser welding forms weld regions bonding the first portion of the metal foil to the metal layer; and
peeling off a second portion of the metal foil.
2. The method of claim 1 , wherein forming the metal layer above a plurality of N-type and P-type semiconductor regions comprises forming a metal seed layer above a plurality of N-type and P-type semiconductor regions.
3. The method of claim 1 , wherein peeling off the second portion of the metal foil comprises peeling off an unwelded portion of the metal foil.
4. The method of claim 1 , wherein peeling off the second portion is performed by gripping and peeling off the second portion of the metal foil.
5. The method of claim 1 , wherein laser welding the first portion of the metal foil to the metal layer comprises using a laser having a pulse duration greater than 100 μs to weld the first portion of the metal foil to the metal layer.
6. The method of claim 1 , wherein the laser welding comprises using a laser beam including an inner region and an outer region of a beam profile, the outer region used to form the weld regions bonding the first portion of the metal foil to the metal layer.
7. The method of claim 1 , further comprising:
patterning the metal foil, wherein the laser welding and the patterning are performed at approximately the same time.
8. The method of claim 7 , wherein the patterning comprises laser ablating through an entire thickness of the metal foil.
9. The method of claim 7 , wherein the patterning comprises laser ablating through at least a portion of the metal foil at regions in alignment with locations between the N-type and P-type semiconductor regions.
10. The method of claim 9 , wherein laser ablating through at least a portion of the metal foil comprises using a laser having a pulse duration less than 1 μs to ablate the portion of the metal foil.
11. The method of claim 10 , wherein laser ablating through at least a portion of the metal foil comprises laser ablating through a portion having a thickness approximately in the range of 80-99% of an entire thickness of the metal foil.
12. The method of claim 10 , wherein laser ablating through at least a portion of the metal foil comprises forming a groove adjacent to the weld regions.
13. The method of claim 10 , further comprising:
subsequent to laser ablating through at least a portion of the metal foil, etching remaining portions of the metal foil to isolate regions of the metal foil in alignment with the N-type and P-type semiconductor regions.