METAL-FOIL-ASSISTED FABRICATION OF THIN-SILICON SOLAR CELL
One embodiment relates to a method of fabricating a solar cell. A silicon lamina is cleaved from the silicon substrate. The backside of the silicon lamina includes the P-type and N-type doped regions. A metal foil is attached to the backside of the silicon lamina. The metal foil may be used advantageously as a built-in carrier for handling the silicon lamina during processing of a frontside of the silicon lamina. Another embodiment relates to a solar cell that includes a silicon lamina having P-type and N-type doped regions on the backside. A metal foil is adhered to the backside of the lamina, and there are contacts formed between the metal foil and the doped regions. Other embodiments, aspects and features are also disclosed.
1 . A solar cell comprising:
a substrate having a front side that is configured to face the sun during normal operation and a backside opposite the front side;
an encapsulant on the front side of the substrate;
a transparent layer on the encapsulant;
a P-type emitter and an N-type emitter on the backside of the substrate;
a first dielectric on the P-type emitter and the N-type emitter;
a metal foil having a first contact that is electrically connected to the P-type emitter through the first dielectric and a second contact that is electrically connected to the N-type emitter through the first dielectric; and
an adhesive layer that the adheres the metal foil to the first dielectric.
2 . The solar cell of claim 1 , wherein the adhesive layer comprises epoxy.
3 . The solar cell of claim 1 , wherein the transparent layer comprises glass.
4 . The solar cell of claim 1 , further comprising:
a second dielectric between the backside of the substrate and the P-type and N-type emitters.
5 . The solar cell of claim 1 , wherein the front side of the substrate is textured.
6 . The solar cell of claim 1 , wherein the substrate comprises silicon.
7 . The solar cell of claim 1 , wherein the metal foil extends beyond a perimeter of the substrate.
8 . The solar cell of claim 1 , wherein the metal foil comprises aluminum.
9 . A solar cell comprising:
a silicon lamina;
P-type and N-type doped regions on a backside of the silicon lamina;
a metal foil adhered to the backside of the silicon lamina;
a first set of contacts between the metal foil and the P-type doped regions; and
a second set of contacts between the metal foil and the N-type doped regions.
10 . The solar cell of claim 9 , wherein the silicon lamina has a thickness in a range between ten and one-hundred microns.
11 . The solar cell of claim 9 , further comprising:
an adhesive layer between the metal foil and the P-type and N-type doped regions on the backside of the silicon lamina, wherein said contacts go through openings in the adhesive layer.
12 . The solar cell of claim 9 , further comprising:
contact spots between the metal foil and the P-type and N-type doped regions on the backside of the silicon lamina.
13 . The solar cell of claim 9 , further comprising:
a textured and passivated surface at a frontside of the silicon lamina;
a glass layer over the frontside of the silicon lamina; and
encapsulant material between the frontside of the silicon lamina and the glass layer.
14 . The solar cell of claim 9 , wherein the metal foil comprises aluminum.
15 . The solar cell of claim 14 , wherein the metal foil comprises Al-x% Si, where x% is in a range from zero percent to three percent.
16 . The solar cell of claim 9 , wherein the metal foil extends beyond a perimeter of the silicon lamina.
17 . A solar cell comprising:
a primary substrate having a front side that faces the sun during normal operation and a backside opposite the front side;
a P-type emitter and an N-type emitter on the backside of the primary substrate;
a first dielectric layer on the P-type and N-type emitters;
a metal foil on the dielectric layer, the metal foil having a first contact finger that is electrically connected to the P-type emitter through the dielectric layer and a second contact finger that is electrically connected to the N-type emitter through the dielectric layer; and
a secondary substrate on the metal foil,
wherein the metal foil includes a finger separation area between the first dielectric layer and the secondary substrate.
18 . The solar cell of claim 17 , wherein the metal foil includes an extended area that extends beyond a perimeter of the primary substrate.
19 . The solar cell of claim 17 , further comprising a second dielectric layer between the primary substrate and the P-type and N-type emitters.
20 . The solar cell of claim 17 , wherein the primary substrate is a silicon lamina.