Embedded junction in hetero-structured back-surface field for photovoltaic devices

1. A photovoltaic device, comprising:

a crystalline substrate;

an emitter contact portion formed in contact with the substrate; and

a back-surface-field junction including:

a homogeneous junction layer in contact with the crystalline substrate having a same conductivity type and a higher active doping density than that of the substrate, wherein the homogeneous junction layer includes a thickness less than a diffusion length of minority carriers in the homogeneous junction layer, wherein the thickness of the homogeneous junction layer ranges from 1 nm to 100 nm, and the diffusion length of the minority carriers ranges from 50 nm to 2 microns;

wherein the homogeneous junction layer includes hydrogenated single-crystalline material; and

a passivation layer formed in contact with the homogeneous junction layer opposite the substrate, which is either doped or undoped.

2. The photovoltaic device of claim 1 , wherein the hydrogenated single-crystalline material includes Si having between 5 and 40 atomic percent hydrogen.

3. The photovoltaic device of claim 1 , wherein the passivation layer includes hydrogenated amorphous, nano-crystalline or micro-crystalline material including a same element as the homogeneous junction layer.

4. The photovoltaic device of claim 3 , wherein the same element includes Si.

5. The photovoltaic device of claim 1 , wherein the homogeneous junction layer has an active doping density in a range of between about 10 18 and about 3×10 20 cm −3 .

6. The photovoltaic device of claim 1 , wherein the homogeneous junction layer includes a thickness in the range of between about 1 to about 25 nm.

7. The photovoltaic device of claim 1 , wherein the passivation layer has a thickness in a range of between about 2 and about 20 nm.

8. The photovoltaic device of claim 1 , wherein the substrate, the homogeneous junction layer, and the passivation layer include a same conductivity type.

9. The photovoltaic device of claim 1 , wherein the crystalline substrate includes a mono-crystalline or multi-crystalline substrate.

10. The photovoltaic device of claim 1 , wherein the emitter contact portion and the back-surface-field junction are configured to form a bifacial device.

11. The photovoltaic device of claim 1 , wherein the emitter contact portion and the back-surface-field junction are formed on a same side of the substrate in an interdigitated arrangement.

12. A photovoltaic device, comprising:

a substrate comprised of mono-crystalline or multi-crystalline material;

an emitter contact portion formed in contact with the substrate; and

a back-surface-field junction including:

a planar and continuous homogeneous junction layer in contact with an entirety of the substrate, the homogeneous junction layer including a hydrogenated single-crystalline material having a same conductivity type and a higher active doping density than that of the substrate, wherein the homogeneous junction layer includes a thickness less than a diffusion length of minority carriers in the homogeneous junction layer, wherein the thickness of the homogeneous junction layer ranges from 1 nm to 100 nm, and the diffusion length of the minority carriers ranges from 50 nm to 2 microns;

a passivation layer formed in contact with the homogeneous junction layer opposite the substrate, which is either doped or undoped; and

a conductive contact portion.

13. The photovoltaic device of claim 12 , wherein the homogeneous junction layer includes between 5 and 40 atomic percent hydrogen.

14. The photovoltaic device of claim 12 , wherein the hydrogenated single-crystalline material includes Si.

15. The photovoltaic device of claim 12 , wherein the passivation layer includes hydrogenated non-crystalline material including a same element as the homogeneous junction layer.

16. The photovoltaic device of claim 15 , wherein the hydrogenated non-crystalline material includes hydrogenated amorphous Si.

17. The photovoltaic device of claim 12 , wherein the homogeneous Junction layer has an active doping density in a range of between about 10 18 and about 3×10 20 cm −3 .

18. The photovoltaic device of claim 12 , wherein the homogeneous junction layer includes a thickness in the range of between about 1 to about 25 nm.

19. The photovoltaic device of claim 12 , wherein the passivation layer has a thickness in a range of between about 2 and about 20 nm.

20. The photovoltaic device of claim 12 , wherein the substrate, the homogeneous junction layer, and the passivation layer include a same conductivity type.

21. The photovoltaic device of claim 12 , wherein the emitter contact portion and the back-surface-field junction are configured to form a bifacial device.

22. The photovoltaic device of claim 12 , wherein the emitter contact portion and the back-surface-field junction are formed on a same side of the substrate in an interdigitated arrangement.

23. A photovoltaic device, comprising:

an emitter;

a doped mono-crystalline or multi-crystalline Si substrate coupled to the emitter;

a planar and continuous doped crystalline layer formed directly on an entirety of the substrate opposite the emitter and having hydrogenated single-crystalline Si material that includes an active doping density in the range of about 10 18 to about 3×10 20 cm −3 and a thickness between about 1 and 25 nm, wherein the diffusion length of the minority carriers in the doped crystalline layer ranges from 50 nm to 2 microns; and

a doped hydrogenated non-crystalline material formed on the doped crystalline layer including a thickness in the range of about 2 to about 20 nm, wherein the substrate, crystalline layer and non-crystalline material include a same dopant conductivity.

24. The photovoltaic device of claim 23 , wherein the doped crystalline layer and the substrate form an embedded homogeneous junction.