NOVEL ELECTRON COLLECTORS FOR SILICON PHOTOVOLTAIC CELLS

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

obtaining a base layer comprising crystalline Si (c-Si);

forming an electron collector on a first side of the base layer, wherein the electron collector includes a quantum-tunneling-barrier (QTB) layer situated adjacent to the base layer and a transparent conducting oxide (TCO) layer situated adjacent to the QTB layer, and wherein the TCO layer has a work function of less than 4.2 eV; and

forming a hole collector on a second side of the base layer, wherein the second side is opposite the first side.

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 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 );

aluminum nitride (AlN x );

silicon oxynitride (SiON);

hydrogenated SiON;

amorphous Si (a-Si);

hydrogenated a-Si;

carbon doped Si; and

SiC.

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

5 . The method of claim 1 , wherein the QTB layer comprises one of: SiO x and hydrogenated SiO x , and wherein the QTB layer is formed using at least one of the following techniques:

running hot deionized water over the base layer;

ozone oxygen oxidation;

atomic oxygen oxidation;

thermal oxidation;

wet or steam oxidation;

atomic layer deposition;

low-pressure radical oxidation; and

plasma-enhanced chemical-vapor deposition (PECVD).

6 . The method of claim 1 , wherein the TCO layer includes one or more of: tungsten doped indium oxide (IWO), Sn doped indium oxide (ITO), fluorine doped tin oxide (F:SnO 2 ), zinc doped indium oxide (IZO), zinc and tungsten doped indium oxide (IZWO), and aluminum doped zinc oxide (AZO).

7 . The method of claim 1 , wherein the TCO layer is formed using a low damage deposition technique comprising one of:

radio frequency (RF) sputtering;

thermal evaporation;

molecular beam epitaxy (MBE);

metalorganic chemical-vapor deposition (MOCVD);

atomic layer deposition (ALD); and

ion plating deposition (IPD).

8 . The method of claim 1 , wherein the electron collector is situated on a front surface of the solar cell, facing incident light, and wherein:

if the base layer is lightly doped with p-type dopants, then the electron collector acts as a front-side emitter; and

if the base layer is lightly doped with n-type dopants, then the electron collector acts as a front surface field (FSF) layer.

9 . The method of claim 8 , wherein the hole collector is situated on a back surface of the solar cell, facing away from the incident light, and wherein:

if the base layer is lightly doped with p-type dopants, then the hole collector acts as a back surface field (BSF) layer; and

if the base layer is lightly doped with n-type dopants, then the hole collector acts as a back-side emitter.

10 . The method of claim 8 , wherein the hole collector comprises one or more of:

a QTB layer;

amorphous-Si (a-Si);

hydrogenated a-Si; and

microcrystalline Si.

11 . The method of claim 8 , wherein the hole collector is graded doped and has a doping concentration ranging between 1×10 12 /cm 3 and 5×10 20 /cm 3 .

12 . The method of claim 1 , wherein the electron collector is situated on a back surface of the solar cell, facing away from incident light, and wherein:

if the base layer is lightly doped with p-type dopants, then the electron collector acts as a back-side emitter; and

if the base layer is lightly doped with n-type dopants, then the electron collector acts as a back surface field (BSF) layer.

13 . The method of claim 12 , wherein the hole collector is situated on a front surface of the solar cell, facing the incident light, and wherein:

if the base layer is lightly doped with p-type dopants, then the hole collector acts as a front surface field (FSF) layer; and

if the base layer is lightly doped with n-type dopants, then the hole collector acts as a front-side emitter.

14 . The method of claim 1 , wherein the base layer has an n-type or a p-type doping concentration ranging between 5×10 14 /cm 3 and 1×10 16 /cm 3 .

15 . The method of claim 1 , wherein obtaining the base layer further comprises shallow doping a surface of the base layer with n-type dopants, wherein the shallow doping has a peak doping concentration of at least 1×10 19 /cm 3 , and wherein the shallow doping has a junction depth of less than 100 nm.

16 . A solar cell, comprising:

a base layer comprising crystalline Si (c-Si);

an electron collector situated on a first side of the base layer, wherein the electron collector includes a quantum-tunneling-barrier (QTB) layer situated adjacent to the base layer and a transparent conducting oxide (TCO) layer situated adjacent to the QTB layer, and wherein the TCO layer has a work function of less than 4.2 eV; and

a hole collector situated on a second side of the base layer, wherein the second side is opposite the first side.

17 . The solar cell of claim 16 , wherein the base layer comprises at least one of:

a monocrystalline silicon wafer; and

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

18 . The solar cell of claim 16 , 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 );

aluminum nitride (AlN x );

silicon oxynitride (SiON);

hydrogenated SiON;

amorphous Si (a-Si);

hydrogenated a-Si;

carbon doped Si; and

SiC.

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

20 . The solar cell of claim 16 , wherein the QTB layer comprises one of: SiO x and hydrogenated SiO x , and wherein the QTB layer is formed using at least one of the following techniques:

running hot deionized water over the base layer;

ozone oxygen oxidation;

atomic oxygen oxidation;

thermal oxidation;

wet or steam oxidation;

atomic layer deposition;

low-pressure radical oxidation; and

plasma-enhanced chemical-vapor deposition (PECVD).

21 . The solar cell of claim 16 , wherein the TCO layer includes one or more of: tungsten doped indium oxide (IWO), Sn doped indium oxide (ITO), fluorine doped tin oxide (F:SnO 2 ), zinc doped indium oxide (IZO), zinc and tungsten doped indium oxide (IZWO), and aluminum doped zinc oxide (AZO).

22 . The solar cell of claim 16 , wherein the TCO layer is formed using a low damage deposition technique comprising one of:

radio frequency (RF) sputtering;

thermal evaporation;

molecular beam epitaxy (MBE);

metalorganic chemical-vapor deposition (MOCVD);

atomic layer deposition (ALD); and

ion plating deposition (IPD).

23 . The solar cell of claim 16 , wherein the electron collector is situated on a front surface of the solar cell, facing incident light, and wherein:

if the base layer is lightly doped with p-type dopants, then the electron collector acts as a front-side emitter; and

if the base layer is lightly doped with n-type dopants, then the electron collector acts as a front surface field (FSF) layer.

24 . The solar cell of claim 23 , wherein the hole collector is situated on a back surface of the solar cell, facing away from the incident light, and wherein:

if the base layer is lightly doped with p-type dopants, then the hole collector acts as a back surface field (BSF) layer; and

if the base layer is lightly doped with n-type dopants, then the hole collector acts as a back-side emitter.

25 . The solar cell of claim 23 , wherein the hole collector comprises one or more of:

a QTB layer;

amorphous-Si (a-Si);

hydrogenated a-Si; and

microcrystalline Si.

26 . The solar cell of claim 23 , wherein the hole collector is graded doped and has a doping concentration ranging between 1×10 12 /cm 3 and 5×10 20 /cm 3 .

27 . The solar cell of claim 16 , wherein the electron collector is situated on a back surface of the solar cell, facing away from incident light, and wherein:

if the base layer is lightly doped with p-type dopants, then the electron collector acts as a back-side emitter; and

if the base layer is lightly doped with n-type dopants, then the electron collector acts as a back surface field (BSF) layer.

28 . The solar cell of claim 27 , wherein the hole collector is situated on a front surface of the solar cell, facing the incident light, and wherein:

if the base layer is lightly doped with p-type dopants, then the hole collector acts as a front surface field (FSF) layer; and

if the base layer is lightly doped with n-type dopants, then the hole collector acts as a front-side emitter.

29 . The solar cell of claim 16 , wherein the base layer has an n-type or a p-type doping concentration ranging between 5×10 14 /cm 3 and 1×10 16 /cm 3 .

30 . The solar cell of claim 16 , wherein the base layer further comprises a shallow doping layer heavily doped with n-type dopants, wherein the shallow doping layer has a peak doping concentration of at least 1×10 19 /cm 3 , and wherein the shallow doping layer has a junction depth of less than 100 nm.