BACK JUNCTION SOLAR CELL WITH TUNNEL OXIDE

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

obtaining a base layer for the solar cell;

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 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 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/or 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/or 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 front-side QTB layer to act as a front surface field (FSF).

18 . 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.

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

a base layer;

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.

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 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.

23 . The solar cell of claim 19 , wherein the QTB layers have a thickness between 1 and 50 angstroms.

24 . The solar cell of claim 19 , 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).

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

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

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

28 . The solar cell of claim 26 , wherein the emitter and/or the surface field layer comprise undoped a-Si.

29 . The solar cell of claim 26 , wherein the emitter and/or the surface field layer comprise graded-doped amorphous-Si (a-Si).

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

31 . The solar cell of claim 29 , 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.

32 . The solar cell of claim 19 , 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 .

33 . The solar cell of claim 32 , 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.

34 . The solar cell of claim 33 , 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).

35 . The solar cell of claim 33 , 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).

36 . The solar cell of claim 19 , 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;

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.