SOLAR CELL WITH OXIDE TUNNELING JUNCTIONS

• US 20110272012A1
• Filed: 11/12/2010
• Published: 11/10/2011
• Est. Priority Date: 05/04/2010
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Silevo, Inc. (Tesla Inc.)
• Inventors: Heng, Jiunn Benjamin, Xu, Zheng, Yu, Chentao, Fu, Jianming
• Granted Patent: US 8,686,283 B2
• Time in Patent Office: Days
• US Class Current: 136/255
• CPC Class Codes: H01L 31/0745 comprising a AIVBIV heterojunction, e.g. Si/Ge, SiGe/Si or Si/SiC solar cells
• CPC Class Codes: H01L 31/0747 comprising a heterojunction of crystalline and amorphous materials, e.g. heterojunction with intrinsic thin layer
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

One embodiment of the present invention provides a tunneling junction based solar cell. The solar cell includes a base layer; a quantum-tunneling-barrier (QTB) layer situated adjacent to the base layer; an emitter; a surface field layer; a front-side electrode; and a back-side electrode.

Claims

1. A method for fabricating a tunneling junction based solar cell, comprising:

obtaining a base layer for the solar cell;

forming a quantum-tunneling-barrier (QTB) layer adjacent to the base layer;

forming an emitter;

forming a surface field layer;

forming a front-side electrode; and

forming a back-side electrode.

2. The method of claim 1, wherein the base layer comprises at least one of:

a mono-crystalline silicon wafer; and

an epitaxially grown crystalline-Si (c-Si) thin film.

3. The method of claim 2, wherein the epitaxially grown c-Si thin film'"'"'s doping profile is modulated.

4. The method of claim 1, wherein the base layer comprises a thin layer of intrinsic Si situated substantially in the middle of the film, and wherein the intrinsic Si layer'"'"'s thickness is between 1 nm and 10 nm.

5. The method of claim 1, wherein the QTB layer comprises at least one of:

silicon oxide (SiO_x);

hydrogenated SiO_x;

silicon nitride (SiN_x);

hydrogenated SiN_x;

aluminum oxide (AlO_x);

silicon oxynitride (SiON); and

hydrogenated SiON.

6. The method of claim 1, wherein the QTB layer has a thickness between 1 and 50 angstroms.

7. The method of claim 1, wherein the QTB layer is formed using at least one of the following techniques:

thermal oxidation;

atomic layer deposition;

wet or steam oxidation;

low-pressure radical oxidation; and

plasma-enhanced chemical-vapor deposition (PECVD).

8. The method of claim 1, further comprising forming a transparent conductive oxide (TCO) layer on the emitter, the surface field layer, or both.

9. The method of claim 1, wherein the emitter and/or the surface field layer comprise amorphous-Si (a-Si).

10. The method of claim 9, wherein the emitter comprises carbon-doped a-Si.

11. The method of claim 9, wherein the emitter and/or the surface field layer comprise undoped a-Si.

12. The method of claim 9, wherein the emitter and/or the surface field layer comprise graded-doped amorphous-Si (a-Si).

13. The method of claim 11, wherein the graded-doped a-Si has a doping concentration ranging between 1×

10¹⁵/cm³ and 5×

10²⁰/cm³.

14. The method of claim 12, wherein an n-type dopant used for the graded-doped a-Si comprises phosphorus, and wherein a p-type dopant used for the graded-doped a-Si comprises boron.

15. The method of claim 1, wherein the base layer has a donor (n-type) or acceptor (p-type) doping concentration ranging between 1×

10¹⁴/cm³ and 1×

10¹⁸/cm³.

16. The method of claim 15, wherein the emitter has an opposite doping type as that of the base layer, and wherein the surface field layer has a same doping type as that of the base layer.

17. The method of claim 16, wherein the emitter is formed on a QTB layer formed on the front side of the base layer, facing incident light, and wherein the surface field layer is formed on a QTB layer formed on the back side of the base layer to act as a back surface field (BSF).

18. The method of claim 16, wherein the emitter is formed on a QTB layer formed on the back side of the base layer, facing away from incident light, and wherein the surface field layer is formed on a QTB layer formed on the front side of the base layer to act as a front surface field (FSF).

19. A tunneling junction based solar cell, comprising:

a base layer;

a quantum-tunneling-barrier (QTB) layer situated adjacent to the base layer;

an emitter;

a surface field layer;

a front-side electrode; and

a back-side electrode.

20. The solar cell of claim 19, wherein the base layer comprises at least one of:

a mono-crystalline silicon wafer; and

an epitaxially grown crystalline-Si (c-Si) thin film.

21. The solar cell of claim 20, wherein the epitaxially grown c-Si thin film'"'"'s doping profile is modulated.

22. The solar cell of claim 19, wherein the base layer comprises a thin layer of intrinsic Si situated substantially in the middle of the film, and wherein the intrinsic Si layer'"'"'s thickness is between 1 nm and 10 nm.

23. The solar cell of claim 19, wherein the QTB layer comprises at least one of:

silicon oxide (SiO_x);

hydrogenated SiO_x;

silicon nitride (SiN_x);

hydrogenated SiN_x;

aluminum oxide (AlO_x);

silicon oxynitride (SiON); and

hydrogenated SiON.

24. The solar cell of claim 19, wherein the QTB layer has a thickness between 1 and 50 angstroms.

25. The solar cell of claim 19, wherein the QTB layer is formed using at least one of the following techniques:

thermal oxidation;

atomic layer deposition;

wet or steam oxidation;

low-pressure radical oxidation; and

plasma-enhanced chemical-vapor deposition (PECVD).

26. The solar cell of claim 19, further comprising a transparent conductive oxide (TCO) layer situated on top of the emitter, the surface field layer, or both.

27. The solar cell of claim 19, wherein the emitter and/or the surface field layer comprise amorphous-Si (a-Si).

28. The solar cell of claim 27, wherein the emitter comprises carbon-doped a-Si.

29. The solar cell of claim 27, wherein the emitter and/or the surface field layer comprise undoped a-Si.

30. The solar cell of claim 27, wherein the emitter and/or the surface field layer comprise graded-doped amorphous-Si (a-Si).

31. The solar cell of claim 30, wherein the graded-doped a-Si has a doping concentration ranging between 1×

10¹⁵/cm³ and 5×

10²⁰/cm³.

32. The solar cell of claim 30, wherein an n-type dopant used for the graded-doped a-Si comprises phosphorus, and wherein a p-type dopant used for the graded-doped a-Si comprises boron.

33. The solar cell of claim 19, wherein the base layer has a donor (n-type) or acceptor (p-type) doping concentration ranging between 1×

10¹⁴/cm³ and 1×

10¹⁸/cm³.

34. The solar cell of claim 33, wherein the emitter has an opposite doping type as that of the base layer, and wherein the surface field layer has a same doping type as that of the base layer.

35. The solar cell of claim 34, wherein the emitter is situated above the base layer facing incident light, and wherein the surface field layer is situated beneath the base layer to act as a back surface field (BSF).

36. The solar cell of claim 34, wherein the emitter is situated beneath the base layer facing away from incident light, and wherein the surface field layer is situated above the base layer to act as a front surface field (FSF).