Solar cell and method for manufacturing the same
A solar cell includes a substrate formed of n-type single crystal silicon, an emitter region of a p-type which is positioned at a first surface of the substrate and includes a first emitter region having a first sheet resistance and a second emitter region having a second sheet resistance less than the first sheet resistance, a plurality of surface field regions of the n-type locally positioned at a second surface opposite the first surface of the substrate, a plurality of first electrodes which are positioned only on the second emitter region to be separated from one another and are connected to the second emitter region, and a plurality of second electrodes which are positioned on the plurality of surface field regions to be separated from one another and are connected to the plurality of surface field regions.
1. A solar cell comprising:
a substrate having a first conductive type impurity;
an emitter region positioned at a first surface of the substrate, the emitter region forming a p-n junction along with the substrate;
a surface field region positioned at a second surface opposite the first surface of the substrate, the surface field region having the first conductive type impurity more heavily doped than that of the substrate;
a plurality of first electrodes positioned on the emitter region to be separated from one another and connected to the emitter region;
a plurality of second electrodes positioned on the surface field region to be separated from one another and connected to the surface field region;
a first anti-reflection layer positioned on the first surface of the substrate, the second surface of the substrate, and a third surface of the substrate other than the first and second surfaces of the substrate, the first anti-reflection layer which is formed of aluminum oxide and has negative fixed charges;
a second anti-reflection layer positioned on the first anti-reflection layer at the first surface and the third surface of the substrate, the second anti-reflection layer which is formed of silicon nitride and has positive fixed charges; and
a passivation layer positioned between the second surface of the substrate and the first anti-reflection layer,
wherein the first anti-reflection layer is positioned directly between the third surface of the substrate and the second anti-reflection layer,
wherein each of the first anti-reflection layer and the passivation layer has a plurality of first openings where the plurality of second electrodes penetrate therethrough on the second surface of the substrate, and
wherein the first anti-reflection layer continuously wraps around from the first surface to the third surface, and continuously wraps around from the third surface to the second surface.
2. The solar cell of claim 1 , wherein the surface field region comprises a plurality of surface field regions selectively or locally positioned at the second surface of the substrate.
3. The solar cell of claim 1 , wherein light is incident to the first surface or the first surface is a front surface.
4. The solar cell of claim 1 , wherein the passivation layer is formed of silicon nitride.
5. The solar cell of claim 1 , wherein a material of the passivation layer is the same as a material of the second anti-reflection layer.
6. The solar cell of claim 1 , wherein the passivation layer is formed of hydrogenated silicon nitride, and
wherein the second anti-reflection layer is formed of hydrogenated silicon nitride.
7. The solar cell of claim 1 , wherein the passivation layer has a refractive index of 2.0 to 2.2, and
wherein the second anti-reflection layer has a refractive index of 2.0 to 2.2.
8. The solar cell of claim 1 , wherein a refractive index of the passivation layer is the same as a refractive index of the second anti-reflection layer.
9. The solar cell of claim 1 , wherein a thickness of the first anti-reflection layer is less than a thickness of the second anti-reflection layer.
10. The solar cell of claim 1 , wherein the passivation layer has a thickness of 70 nm to 80 nm, and
wherein the second anti-reflection layer has a thickness of 70 nm to 80 nm.
11. The solar cell of claim 1 , wherein a thickness of the passivation layer is the same as a thickness of the second anti-reflection layer.
12. The solar cell of claim 1 , wherein portions of the first anti-reflection layer on the first surface, the second surface, and the third surface of the substrate have the same material, the same thickness, the same refractive index, or the same composition.
13. The solar cell of claim 1 , wherein portions of the first anti-reflection layer on the first surface, the second surface, and the third surface of the substrate are connected to each other.
14. The solar cell of claim 1 , wherein the first anti-reflection layer is positioned on an entire portion of the first surface, the second surface, and the third surface of the substrate except for a plurality of second openings where the plurality of first electrodes penetrate and the plurality of first openings where the plurality of second electrodes penetrate.
15. The solar cell of claim 1 , wherein the solar cell is a bifacial solar cell.
16. The solar cell of claim 1 , wherein the first anti-reflection layer is positioned directly on the first surface of the substrate, and directly on the third surface of the substrate.