Method for forming flexible solar cells
The invention provides for a semiconductor wafer with a metal support element suitable for the formation of a flexible or sag tolerant photovoltaic cell. A method for forming a photovoltaic cell may comprise providing a semiconductor wafer have a thickness greater than 150 μm, the wafer having a first surface and a second surface opposite the first and etching the semiconductor wafer a first time so that the first etching reduces the thickness of the semiconductor wafer to less than 150 μm. After the wafer has been etched a first time, a metal support element may be constructed on or over the first surface; and a photovoltaic cell may be fabricated, wherein the semiconductor wafer comprises the base of the photovoltaic cell.
1. A method for forming a photovoltaic cell, the method comprising:
a. providing a semiconductor wafer have a thickness greater than 150 μm, the wafer having a first surface and a second surface opposite the first;
b. performing a first etching of the semiconductor wafer, wherein the first etching reduces the thickness of the semiconductor wafer to less than 40 μm;
c. constructing a metal support element on or over the first surface; and
d. fabricating a photovoltaic cell having a base, wherein the semiconductor wafer comprises the base of the photovoltaic cell,
wherein a temporary carrier is applied to the second surface of the semiconductor wafer prior to the first etching.
2. The method of claim 1 wherein the metal support comprises nickel.
3. The method of claim 1 wherein the metal support has a coefficient of thermal expansion that is substantially the same as the semiconductor wafer.
4. The method of claim 1 wherein the metal support element on the first surface comprises a first layer comprising nickel on or above the first surface and a second layer comprising a nickel alloy on or above the first layer.
5. The method of claim 1 wherein the metal support element comprises electroplated nickel on or above the first surface.
6. The method of claim 4 wherein the nickel alloy comprises iron, cobalt or any combination thereof.
7. The method of claim 4 wherein the second layer comprising the nickel alloy is less than 25 μm thick.
8. The method of clam 4 wherein the first layer comprising nickel is less than 2 μm thick.
9. The method of claim 4 wherein the metal support element further comprises a third layer comprising nickel on the second layer.
10. The method of claim 1 wherein the photovoltaic cell is capable of adopting a radius of curvature that is less than about 1 meter.
11. The method of claim 1 wherein the semiconductor wafer is monocrystalline silicon.
12. The method of claim 1 further comprising the step of applying a first layer of amorphous silicon to the first surface of the semiconductor wafer, wherein the first layer of amorphous silicon is disposed between the wafer and the metal support.
13. The method of claim 1 wherein the step of fabricating a photovoltaic cell comprises applying a second layer of amorphous silicon to the second surface of the semiconductor wafer, and wherein the amorphous silicon comprises an emitter of the photovoltaic cell.
14. The method of claim 1 wherein the step of constructing a metal support element comprises constructing a continuous layer of metal on or over the first surface, wherein the continuous layer of metal covers the entire surface of wafer.
15. The method of claim 1 further comprising the step of applying a layer of amorphous silicon to the first surface of the semiconductor wafer prior to constructing the metal support element, and wherein the amorphous silicon layer comprises a contact to the base of the photovoltaic cell.