Granted Patent B2

US 7,553,691 · App. 11/114,454 · Granted Jun 30, 2009

Abstract

Claims (45)

1. A method for manufacturing a triple-junction solar cell comprising:

providing a germanium substrate; forming a bottom cell in the substrate;

forming a heterojunction middle cell over the bottom cell; and

forming a homojunction top cell over the heterojunction middle cell.

2. The method of claim 1 , further comprising:

forming a first tunnel junction layer over the bottom cell;

depositing an indium gallium arsenide (InGaAs) base layer over the first tunnel junction layer; and

depositing a first indium gallium phosphide (InGaP) emitter layer over the InGaAs base layer.

3. The method of claim 2 , wherein the step of forming a first tunnel junction layer comprises:

depositing a gallium arsenide (GaAs) layer on the bottom cell; and

depositing an aluminum gallium arsenide (AlGaAs) layer over the GaAs layer.

4. The method of claim 2 , wherein the step of forming a heterojunction middle cell comprises:

depositing an aluminum gallium arsenide (AlGaAs) back surface field (BSF) layer on the first tunnel junction layer;

depositing an indium gallium arsenide (InGaAs) set back (SB) layer over the InGaAs base layer; and

depositing a first indium aluminum phosphide (InAlP) window layer over the InGaP emitter layer.

5. The method of claim 2 , wherein the step of forming a homojunction top cell over the heterojunction middle cell comprises:

forming a second tunnel junction layer over the middle cell;

depositing an indium gallium phosphide (InGaP) base layer over the second tunnel junction layer; and

depositing a second indium gallium phosphide (InGaP) emitter layer over the InGaP base layer.

6. The method of claim 5 , wherein the step of forming a second tunnel junction layer further comprises:

depositing an indium phosphide (InGaP) layer on the middle cell; and

depositing an aluminum gallium arsenide (AlGaAs) layer over the InGaP layer.

7. The method of claim 5 , wherein the step of forming a homojunction top cell over the heterojunction middle cell comprises:

depositing an indium gallium aluminum phosphide (InGaAlP) back surface field (BSF) layer on the second tunnel junction layer; and

depositing an indium gallium phosphide (InGaP) set back (SB) layer between the InGaP base layer and the InGaP emitter layer.

8. The method of claim 7 , wherein the step of forming a homojunction top cell further comprises:

depositing a second indium aluminum phosphide (InAlP) window layer on the InGaP emitter layer; and

depositing a gallium arsenide (GaAs) contact layer on the second InAlP window layer.

9. A method for forming a multijunction solar cell comprising:

forming a first cell including a germanium (Ge) substrate;

forming a second cell disposed over the first cell having a heterojunction solar cell structure including a first emitter layer and a first base layer; and

forming a homojunction third cell disposed over the second cell.

10. The method of claim 9 , further comprising:

forming a first tunnel junction layer disposed between the first and second cells;

forming a second tunnel junction layer disposed between the second and third cells; and

forming a contact layer including gallium arsenide (GaAs) disposed over the third cell.

11. The method of claim 9 , wherein the first cell is the bottom cell of the multijunction solar cell and further comprising a nucleation layer disposed over the Ge substrate.

12. The method of claim 9 , further comprising:

forming a buffer layer that includes GaAs deposited over the Ge substrate.

13. The method of claim 9 , wherein the second cell is a middle cell that includes a window layer that includes indium aluminum phosphide (InAlP) disposed over the first emitter layer.

14. The method of claim 9 , wherein the first base layer includes indium gallium arsenide (InGaAs) and the first emitter layer includes indium gallium phosphide (InGaP).

15. The method of claim 9 , wherein the third cell is a top cell having a second emitter layer and a second base layer, and further comprising a window layer that includes indium aluminum phosphide (InAlP) disposed over the second emitter layer.

16. The method of claim 15 , wherein the second base layer includes indium gallium arsenide (InGaAs).

17. The method of claim 15 , wherein the second emitter layer includes InGaAs.

18. The method of claim 9 , wherein the third cell has a homojunction structure including second base and emitter layers that have substantially the same material composition.

Assignments (11)