Method to form a photovoltaic cell comprising a thin lamina
View Patent ↗A very thin photovoltaic cell is formed by implanting gas ions below the surface of a donor body such as a semiconductor wafer. Ion implantation defines a cleave plane, and a subsequent step exfoliates a thin lamina from the wafer at the cleave plane. A photovoltaic cell, or all or a portion of the base or emitter of a photovoltaic cell, is formed within the lamina. In preferred embodiments, the wafer is affixed to a receiver before the cleaving step. Electrical contact can be formed to both surfaces of the lamina, or to one surface only.
1. A method for forming a device, the method comprising:
permanently adhering a first surface of a semiconductor body to a receiver, wherein the receiver is metal; and
cleaving a lamina from the semiconductor body, wherein the lamina comprises the first surface, the first surface remains adhered to the receiver, and the lamina is between 1 and 80 microns thick.
2. The method of claim 1 wherein the lamina is between 1 and 20 microns thick.
3. The method of claim 1 wherein the semiconductor body is a silicon wafer.
4. The method of claim 1 wherein the lamina comprises a second surface opposite the first, wherein a metal or transparent conductive oxide makes electrical contact to the second surface.
5. The method of claim 4 further comprising, before the adhering step, doping the first surface to a first conductivity type.
6. The method of claim 4 further comprising doping the second surface to a second conductivity type opposite the first conductivity type.
7. The method of claim 4 wherein a transparent conductive oxide makes electrical contact to the second surface, and wherein the transparent conductive oxide is zinc oxide.
8. The method of claim 1 further comprising, before the adhering step, implanting one or more species of gas ions through the first surface, wherein a depth of maximum concentration of the implanted gas ions defines a cleave plane for the cleaving step.
9. The method of claim 8 wherein the one or more species of gas ions comprise hydrogen ions and helium ions.
10. The method of claim 1 wherein the lamina is between about 1 and about 5 microns thick.
11. The method of claim 1 wherein the lamina is between about 1 and about 2 microns thick.
12. The method of claim 1 wherein the semiconductor body is a monocrystalline silicon wafer.
13. The method of claim 1 wherein the semiconductor body comprises polycrystalline or multicrystalline semiconductor material.
14. The method of claim 1 further comprising, after the cleaving step, fabricating a photovoltaic cell, wherein the photovoltaic cell comprises the lamina.
15. The method of claim 1 wherein the receiver is aluminum.