BACK JUNCTION SOLAR CELL WITH TUNNEL OXIDE

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

obtaining a base layer for the solar cell;

forming a quantum-tunneling-barrier (QTB) layer at a backside of the base layer facing away from incident light;

forming an emitter layer underneath the QTB layer, wherein a doping type of the emitter layer is opposite to a doping type of the base layer;

forming a front surface field (FSF) layer above the base layer;

forming a front-side electrode above the FSF layer; and

forming a back-side electrode underneath the emitter layer.

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 layer comprises at least one of:

silicon oxide (SiO x );

hydrogenerated SiO x ;

silicon nitride (SiN x );

hydrogenerated SiN x ;

aluminum oxide (AlO x );

silicon oxynitride (SiON); and

hydrogenerated SiON.

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

6 . 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).

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

8 . The method of claim 7 , wherein the TCO layer comprises at least one of:

indium-tin-oxide (ITO);

indium oxide (InO);

indium-zinc-oxide (IZO);

tungsten-doped indium-oxide (IWO);

tin-oxide (SnO x );

aluminum doped zinc-oxide (ZnO:Al or AZO); and

gallium doped zinc-oxide (ZnO:Ga).

9 . The method of claim 1 , wherein the emitter layer and/or the FSF layer comprise at least one of:

amorphous-Si (a-Si);

polycrystalline Si; and

one or more wide bandgap semiconductor materials.

10 . The method of claim 9 , wherein the emitter layer and/or the FSF layer comprise a graded-doped amorphous-Si (a-Si) layer with a doping concentration ranging between 1×10 15 /cm 3 and 5×10 20 /cm 3 .

11 . The method of claim 1 , further comprising forming a front QTB layer at a frontside of the base layer facing the incident sunlight.

12 . A back junction solar cell, comprising:

a base layer;

a quantum-tunneling-barrier (QTB) layer situated below the base layer facing away from incident light;

an emitter layer situated below the QTB layer;

a front surface field (FSF) layer situated above the base layer;

a front-side electrode situated above the FSF layer; and

a back-side electrode situated below the emitter layer.

13 . The solar cell of claim 12 , wherein the base layer comprises at least one of:

a mono-crystalline silicon wafer; and

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

14 . The solar cell of claim 13 , wherein the epitaxially grown c-Si thin film's doping profile is modulated.

15 . The solar cell of claim 12 , wherein the QTB layer comprises at least one of:

silicon oxide (SiO x );

hydrogenerated SiO x ;

silicon nitride (SiNO x );

hydrogenerated SiN x ;

aluminum oxide (AlO x );

silicon oxynitride (SiON); and

hydrogenerated SiON.

16 . The solar cell of claim 12 , wherein the QTB layer has a thickness between 1 and 50 angstroms.

17 . The solar cell of claim 12 , 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).

18 . The solar cell of claim 12 , further comprising at least one of:

a first transparent conductive oxide (TCO) layer situated below the emitter layer; and

a second TCO layer situated above the FSF layer.

19 . The solar cell of claim 18 , wherein the first and second TCO layers comprises at least one of:

indium-tin-oxide (ITO);

indium oxide (InO);

indium-zinc-oxide (IZO);

tungsten-doped indium-oxide (IWO);

tin-oxide (SnOx);

aluminum doped zinc-oxide (ZnO:Al or AZO); and

gallium doped zinc-oxide (ZnO:Ga).

20 . The solar cell of claim 12 , wherein the emitter layer and/or the FSF layer comprise at least one of:

amorphous-Si (a-Si);

polycrystalline Si; and

one or more wide bandgap semiconductor materials.

21 . The solar cell of claim 20 , wherein the emitter and/or the surface field layer comprise a graded-doped amorphous-Si (a-Si) layer with a doping concentration ranging between 1×10 15 /cm 3 and 5×10 20 /cm 3 .

22 . The solar cell of claim 12 , further comprising a front QTB layer situated between the FSF layer and the base layer.