SOLAR CELL FABRICATED BY SILICON LIQUID-PHASE DEPOSITION

1 . A solar cell comprising:

a substrate;

a polycrystalline Si (poly-Si) thin-film layer which includes a p + layer situated above the substrate, wherein the polycrystalline thin-film Si layer is hydrogenated;

a contact under-layer situated between the substrate and the polycrystalline thin-film Si layer;

a metal layer situated below the contact layer, wherein part of the metal layer reaches the p | layer through the contact under-layer;

an n-type doped amorphous Si (a-Si) thin-film layer situated above the polycrystalline thin-film Si layer forming a heterojunction;

an optional intrinsic layer situated between the poly-Si thin-film layer and the n-type doped a-Si thin-film layer;

a transparent conductive layer situated above the n-type doped a-Si thin-film layer; and

a front-side electrode situated above the transparent conductive layer.

2 . The solar cell of claim 1 , wherein the substrate comprises at least one of the following:

glass;

steel;

graphite;

ceramic material; and

metallurgic Si.

3 . The solar cell of claim 1 , wherein the poly-Si thin-film layer is deposited using a liquid-phase deposition (LPD) process at a substrate temperature between 600° C. and 700° C.

4 . The solar cell of claim 1 , wherein the contact under-layer comprises SiO 2 and/or boron-doped silica glass (BSG).

5 . The solar cell of claim 4 , wherein the contact under-layer comprises a plurality of vias; and

wherein part of the metal layer is extruded through the vias to be in contact with the p − layer.

6 . The solar cell of claim 5 , further comprising a layer of boron material in the contact under layer.

7 . The solar cell of claim 1 , wherein the metal layer comprises at least one of the following:

Al;

Al/Ag alloy; and

Al/Ni/Cu alloy.

8 . The solar cell of claim 1 , further comprising a barrier layer situated between the substrate and the metal layer, wherein the barrier layer comprises silicon nitride and/or TiO 2 .

9 . A method for fabricating a solar cell, the method comprising:

depositing a metal layer on top of a substrate;

depositing a contact under-layer on top of the metal layer;

depositing a polycrystalline Si (poly-Si) thin-film layer on top of the contact under-layer using an LPD process at a sufficiently high temperature, thereby allowing part of the metal layer to reaches the poly-Si thin-film layer through the contact under layer;

depositing an n-type doped amorphous Si (a-Si) thin-film layer on top of the poly-Si thin-film layer;

depositing a transparent conductive layer on top of the n-type doped a-Si thin-film layer; and

depositing a front-side electrode on top of the transparent conductive layer.

10 . The method of claim 9 , wherein the substrate comprises at least one of the following:

glass;

steel;

graphite;

metallurgic silicon; and

ceramic material.

11 . The method of claim 9 , wherein the depositing of the poly-Si thin-film layer comprises using an LPD process at a substrate temperature between 600° C. and 700° C.; and

wherein the LPD process is performed in an H 2 atmosphere which comprises a mixture of H 2 and a number of inert carrier gases, thereby facilitating in-situ hydrogenation of the poly-Si thin-film layer during the LPD process.

12 . The method of claim 11 , further comprising patterning and etching the contact under-layer to form a plurality of vias in the contact under-layer to allow the metal layer to be extruded through the vias during the LPD process.

13 . The method of claim 12 , further comprising depositing a layer of boron material on top of the contact under-layer, thereby allowing boron ions inside the boron material to diffuse into the poly-Si thin-film layer to form a p + layer during the LPD process.

14 . The method of claim 12 , wherein the metal layer comprises Al which acts as a p-type dopant during the LPD process to form a localized p + region to form contact to the poly-Si thin-film layer.

15 . The method of claim 9 , further comprising using a laser-fired-contact (LFC) process to fire the metal layer through the contact under-layer.

16 . The method of claim 15 , wherein the metal layer comprises at least one of the following: Al, Al/Ag alloy, and Ai/Ni/Cu alloy; and

wherein Al ions are fired through the contact under-layer to act as a p-type dopant to generate a localized p + region to form contacts to the poly-Si thin-film layer.

17 . The method of claim 9 , wherein the contact under-layer comprises SiO 2 and/or boron-doped silica glass (BSG).

18 . The method of claim 9 , wherein the a-Si thin film is deposited using a plasma-enhanced chemical-vapor-deposition (PECVD) process; and

wherein the poly-Si thin-film layer is pretreated with NH 3 or H 2 plasma inside the PECVD chamber.

19 . The method of claim 9 , further comprising depositing a barrier layer situated on top of the substrate, wherein the barrier layer comprises silicon nitride and/or TiO 2 .

20 . A method for fabricating a solar cell, the method comprising:

forming a plurality of holes in a substrate;

depositing a contact under-layer on top of the;

depositing a polycrystalline Si (poly-Si) thin-film layer on top of the contact under-layer;

depositing an Al layer on the back-side of the substrate at an elevated temperature, wherein part of the Al fills in the holes and is in contact with the poly-Si thin-film layer to form p+ contacts with the poly-Si thin-film layer after an annealing process;

depositing an n-type doped amorphous Si (a-Si) thin-film layer on top of the poly-Si thin-film layer;

depositing a transparent conductive layer on top of the n-type doped a-Si thin-film layer; and

depositing a front-side electrode on top of the transparent conductive layer.

21 . The method of claim 20 , wherein the substrate comprises at least one of the following:

glass;

steel;

graphite;

ceramic material; and

metallurgic silicon.

22 . The method of claim 20 , wherein the poly-Si thin-film layer is formed using an LPD process at a substrate temperature between 600° C. and 700° C.; and

wherein the LPD process is performed in an atmosphere comprising a mixture of H 2 and a number of inert carrier gases, thereby facilitating in-situ hydrogenation of the poly-Si thin film

23 . The method of claim 22 , wherein the contact under-layer comprises boron-doped silica glass (BSG); and

wherein during the LPD process, boron ions diffuse into the poly-Si thin-film layer forming a p + region.

24 . The method of claim 20 , wherein depositing the Al electrode comprises using a physical-vapor-deposition (PVD) technique and/or an electrochemical-plating (ECP) technique and/or a screen printing technique.

25 . The method of claim 20 , wherein the n-type doped a-Si thin-film layer is deposited using a plasma-enhanced chemical-vapor-deposition (PECVD) process; and

wherein the poly-Si thin-film layer is pretreated with NH 3 or H 2 plasma inside the PECVD chamber.