Solar cell and method for making thereof
A solar cell includes a doped layer disposed on a first surface of a semiconductor substrate, a doped polysilicon layer disposed in a first region of a second surface of the semiconductor substrate, a doped area disposed in a second region of the second surface, and an insulating layer covering the doped polysilicon layer and the doped area. The insulating layer has openings exposing portions of the doped polysilicon layer and the doped layer, and the doped polysilicon layer and doped layer are respectively connected to a first electrode and a second electrode through the openings. The semiconductor substrate and the doped layer have a first doping type. One of the doped polysilicon layer and the doping area has a second doping type, and the other one of the doped polysilicon layer and the doping area has the first doping type which is opposite to the second doping type.
1. A method for making a solar cell, comprising:
providing a semiconductor substrate, having a first surface and a second surface, wherein the second surface has a first region and a second region and the semiconductor substrate has a first doping type;
forming a doped polysilicon layer in the first region on the second surface of the semiconductor substrate, exposing the second region of the second surface of the semiconductor substrate;
forming at least one doped area in the exposed second region of the second surface of the semiconductor substrate, wherein one of the doped polysilicon layer and the doped area has a second doping type, the other one of the doped polysilicon layer and the doped area has the first doping type, and the second doping type is opposite to the first doping type;
forming an insulating layer to cover and being disposed on the doped polysilicon layer and the doped area, the insulating layer having at least one first opening exposing a portion of the doped polysilicon layer and at least one second opening exposing a portion of the doped area;
forming a metal layer on the insulating layer with the first and second openings, the metal layer including:
at least one first electrode, connected to the doped polysilicon layer through the first opening; and
at least one second electrode, connected to the doped area through the second opening; and
forming a doped layer to cover and being disposed on the first surface of the semiconductor substrate to cover the first surface, wherein the doped layer has the first doping type.
2. The method for making the solar cell of claim 1 , further comprising forming an oxide layer disposed between the second region of the second surface of the semiconductor substrate and the doped polysilicon layer before forming the doped polysilicon layer.
3. The method for making the solar cell of claim 1 , wherein the step of forming the insulating layer with the first opening exposing the portion of the doped polysilicon layer and the second opening exposing the portion of the doped area and covering the surfaces of the doped polysilicon layer and the doped area includes:
forming a first insulating layer disposed on the surface of the doped polysilicon layer, the first insulating layer having a first sub-opening that exposes the portion of the doped polysilicon layer and a second sub-opening that exposes at least one portion of the doped area; and
forming a second insulating layer, covering and disposed on the first insulating layer and the doped area and having a third sub-opening corresponding to the first sub-opening, exposing the portion of the doped polysilicon layer, and a fourth sub-opening corresponding to the second sub-opening, exposing the portion of the doped area;
wherein the first insulating layer and the second insulating layer are composed of different materials, the first sub-opening and the third sub-opening compose the first opening, and the second sub-opening and the fourth sub-opening compose the second opening.
4. The method for making the solar cell of claim 3 , wherein a polarity of a fixed oxide charge (FOC) of the first insulating layer is opposite to a polarity of the FOC of the second insulating layer.
5. The method for making the solar cell of claim 4 , wherein the polarity of the FOC of the first insulating layer is opposite to the second doping type and the polarity of the FOC of the second insulating layer is opposite to the first doping type when the doped area has the first doping type and the doped polysilicon layer has the second doping type.
6. The method for making the solar cell of claim 4 , wherein the polarity of the FOC of the first insulating layer is opposite to the first doping type and the polarity of the FOC of the second insulating layer is opposite to the second doping type when the doped polysilicon layer has the first doping type and the doped area has the second doping type.
7. The method for making the solar cell of claim 3 , further comprising forming an amorphous silicon layer before forming the doped area, the amorphous silicon layer being disposed between the first insulating layer and the second insulating layer, between a side of the doped polysilicon layer and the second insulating layer, and between the doped area and the semiconductor substrate.
8. The method for making the solar cell of claim 1 , further comprising forming a trench in the second region of the second surface of the semiconductor substrate, wherein the doped area is formed in the trench.
9. The method for making the solar cell of claim 8 , further comprising forming an amorphous silicon layer before forming the doped area, the amorphous silicon layer being disposed between the doped polysilicon layer and the insulating layer and between the doped area and the semiconductor substrate.
10. The method for making the solar cell of claim 1 , wherein the doped area is a doped amorphous silicon layer.
11. The method for making the solar cell of claim 1 , further comprising forming an ARC layer on the first surface of the semiconductor substrateto cover the doped layer.