Solar cell and method for manufacturing the same
Discussed is a solar cell including a semiconductor substrate including a base area and a doping area, a doping layer formed on the semiconductor substrate, the doping layer having a conductive type different from the doping area, a tunneling layer interposed between the doping layer and the semiconductor substrate, a first electrode connected to the doping area, and a second electrode connected to the doping layer.
1. A solar cell comprising:
a semiconductor substrate having a front surface and a rear surface; the semiconductor substrate having a monocrystalline structure and a first conductive type; a doping area formed in the rear surface of the semiconductor substrate by diffusing a first dopant having the first conductive type; the doping area having a higher dopant concentration than a dopant concentration of the semiconductor substrate; the doping area having a same crystalline structure as the semiconductor substrate;
a doping layer formed on the rear surface of the semiconductor substrate and having a micro-crystalline or polycrystalline structure, the doping layer having a second dopant having a second conductive type different from the first conductive type;
a tunneling layer interposed between the doping layer and the rear surface of the semiconductor substrate;
an insulating layer contacted to a rear surface of the doping area and to the doping layer and having a first opening on the doping area and a second opening on the doping layer;
wherein the insulating layer is a continuous layer except at the first and second openings;
a barrier layer positioned on the doping layer between the doping layer and the insulating layer;
a first electrode connected to the doping area through the first opening; and
a second electrode directly contacting the doping layer through the second opening through the barrier layer and the insulating layer;
wherein the semiconductor substrate further includes an interval region formed of a base area of the semiconductor substrate, the interval region having a lower dopant concentration than that of the doping area and positioned between the doping area and the doping layer to separate the doping area and the doping layer;
a third opening, comprising the first opening, and corresponding to the doping area and the interval region, wherein each of the barrier layer, the doping layer, and the tunneling layer are continuous layers except at the third opening;
wherein the doping layer and the tunneling layer each contact the insulating layer at a plane which corresponds to an end of the interval region, the plane being perpendicular to a plane which is parallel to the rear surface of the semiconductor substrate;
wherein the interval region is covered by the insulating layer, and not the barrier layer, in a direction perpendicular to the plane which is parallel to the rear surface of the semiconductor substrate.
2. The solar cell according to claim 1 , wherein the tunneling layer has a thickness of 0.5 nm to 5 nm.
3. The solar cell according to claim 1 , wherein the tunneling layer comprises at least one of oxides, nitrides and conductive polymers.
4. The solar cell according to claim 1 , wherein the first conductive type is n-type, and the second conductive type is p-type.
5. The solar cell according to claim 1 , wherein a total area of the doping layer is larger than a total area of the doping area.
6. The solar cell according to claim 5 , wherein a ratio of the total area of the doping area to the total area of the semiconductor substrate is 0.5% to 30%.
7. The solar cell according to claim 6 , wherein the ratio of the total area of the doping area to the total area of the semiconductor substrate is 0.5% to 5%.
8. The solar cell according to claim 1 , wherein a thickness of the doping layer is greater than a thickness of the tunneling layer.
9. The solar cell according to claim 8 , wherein the thickness of the tunneling layer is 0.5 nm to 5.0 nm and the thickness of the doping layer is 50 nm to 250 nm.
10. The solar cell according to claim 1 , wherein the doping area comprises a plurality of first regions connected to the first electrode.
11. The solar cell according to claim 1 , wherein the doping area comprises a plurality of first regions connected to the first electrode, and a second region having a smaller width than a width of each of the first regions of the plurality of first regions, the second region connected to the plurality of first regions;
or the doping area comprises a plurality of branch portions parallel to each other to have a stripe pattern.
12. The solar cell according to claim 1 , wherein the tunneling layer has a shape corresponding to the doping layer.
13. The solar cell according to claim 1 , wherein the second electrode comprises a metal layer.
14. The solar cell according to claim 1 , wherein the doping layer and the rear surface of the semiconductor substrate form a tunnel junction at the tunneling layer.