Solar cell with oxide tunneling junctions

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

obtaining a base layer for the solar cell, wherein the base layer comprises a top portion, a bottom portion, and a thin layer of intrinsic Si sandwiched between the top portion and a bottom portion, and wherein the intrinsic Si layer's thickness is between 1 nm and 10 nm;

simultaneously forming a front-side quantum-tunneling-barrier (QTB) layer on a front surface of the base layer and a back-side QTB layer on a back surface of the base layer;

forming an emitter;

forming a surface field layer;

forming a front-side electrode; and

forming aback-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 QTB layers comprise 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.

5. The method of claim 1 , wherein the QTB layers have a thickness between 1 and 50 angstroms.

6. The method of claim 1 , wherein forming the QTB layers involves 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).

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

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

9. The method of claim 8 , wherein the emitter comprises carbon-doped a-Si.

10. The method of claim 8 , wherein the emitter and the surface field layer comprise undoped a-Si.

11. The method of claim 8 , wherein the emitter and the surface field layer comprise graded-doped amorphous-Si (a-Si).

12. The method of claim 11 , wherein the graded-doped a-Si has a doping concentration ranging between 1×10 15 /cm 3 and 5×10 20 /cm 3 .

13. The method of claim 11 , wherein when an n-type dopant is used for the graded-doped a-Si the n-type dopant comprises phosphorus, and wherein when a p-type dopant is used for the graded-doped a-Si the p-type dopant comprises boron.

14. The method of claim 1 , wherein the base layer has a donor (n-type) or acceptor (p-type) doping concentration ranging between 1×10 14 /cm 3 and 1×10 18 /cm 3 .

15. The method of claim 14 , 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.

16. The method of claim 15 , wherein the emitter is formed on the front-side QTB layer, facing incident light, and wherein the surface field layer is formed on the back-side QTB layer to act as a back surface field (BSF).

17. The method of claim 15 , wherein the emitter is formed on the back-side QTB layer, facing away from incident light, and wherein the surface field layer is formed on the fornt-side QTB layer to act as a front surface field (FSF).

18. A tunneling-junction based solar cell, comprising:

a base layer, wherein the base layer comprises a top portion, a bottom portion, and a thin layer of intrinsic Si sandwiched between the top portion and the bottom portion, and wherein the intrinsic Si layer's thickness is between 1 nm and 10 nm;

a front quantum-tunneling-barrier (QTB) layer situated on a front surface of the base layer;

a back QTB layer situated on a back surface of the base layer;

an emitter;

a surface field layer;

a front-side electrode; and

a back-side electrode.

19. The solar cell of claim 18 wherein the base layer comprises at least one of:

a mono-crystalline silicon wafer; and

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

20. The solar cell of claim 19 , wherein the epitaxially grown c-Si thin film's doping profile is modulated.

21. The solar cell of claim 18 , wherein the QTB layers comprise 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.

22. The solar cell of claim 18 , wherein the QTB layers have a thickness between 1 and 50 angstroms.

23. The solar cell of claim 18 , wherein the QTB layers are 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).

24. The solar cell of claim 18 , further comprising a transparent conductive oxide (TCO) layer situated on top of the emitter, the surface field layer, or both.

25. The solar cell of claim 18 , wherein the emitter and the surface field layer comprise amorphous-Si (a-Si).

26. The solar cell of claim 25 , wherein the emitter comprises carbon-doped a-Si.

27. The solar cell of claim 25 , wherein the emitter and the surface field layer comprise undoped a-Si.

28. The solar cell of claim 25 , wherein the emitter and the surface field layer comprise graded-doped amorphous-Si (a-Si).

29. The solar cell of claim 28 , wherein the graded-doped a-Si has a doping concentration ranging between 1×10 15 /cm 3 and 5×10 20 /cm 3 .

30. The solar cell of claim 28 , wherein when an n-type dopant is used for the graded-doped a-Si the n-type dopant comprises phosphorus, and wherein when a p-type dopant is used for the graded-doped a-Si the p-type dopant comprises boron.

31. The solar cell of claim 18 , wherein the base layer has a donor (n-type) or acceptor (p-type) doping concentration ranging between 1×10 14 /cm 3 and 1×10 18 /cm 3 .

32. The solar cell of claim 31 , 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.

33. The solar cell of claim 32 , 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).

34. The solar cell of claim 32 , 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).

35. The method of claim 1 , wherein forming the QTB layers involves using a wet oxidation technique to form a SiO x , layer with x less than 2.

36. The solar cell of claim 18 , wherein the QTB layers comprise a SiO x , layer with x less than 2, wherein the SiO x , layer is formed using a wet oxidation technique.

37. A solar cell, comprising:

a base layer, wherein the base layer comprises a top portion, a bottom portion, and a thin layer of intrinsic Si sandwiched between the top portion and the bottom portion, and wherein the intrinsic Si layer's thickness is between 1 nm and 10 nm;

a quantum-tunneling-barrier (QTB) layer situated adjacent to the base layer, wherein the QTB layer comprises SiO x , with x less than two;

an emitter;

a surface field layer;

a front-side electrode; and

a back-side electrode.