Solar cell
A solar cell includes a silicon substrate, an emitter area formed on a front surface of the silicon substrate, a tunneling oxide layer formed on a back surface of the silicon substrate, a back surface field area formed on the tunneling oxide layer and formed of a polycrystalline silicon layer, a back passivation film formed on the back surface field area and having an opening, and a back electrode connected to the back surface field area via the opening.
1. A solar cell comprising:
a monocrystalline silicon substrate;
an emitter area formed inside of a front surface of the monocrystalline silicon substrate;
a tunneling oxide layer formed directly on the monocrystalline silicon substrate;
a polycrystalline silicon back surface field area formed directly on the tunneling oxide layer;
a front passivation film on the emitter area;
a back passivation film formed of an insulating material and formed on the polycrystalline silicon back surface field area;
a front electrode directly connected to the emitter area by penetrating through the front passivation film; and
a back electrode directly connected to the polycrystalline silicon back surface field area through an opening of the back passivation film,
wherein a thickness of the polycrystalline silicon back surface field area is about 50 nm to 500 nm;
wherein the thickness of the polycrystalline silicon back surface field area being about 50 nm to 500 nm is provided when a crystalline structure of the polycrystalline silicon back surface field area being different from that of the monocrystalline silicon substrate and that of the emitter area.
2. The solar cell according to claim 1 , wherein the emitter area has a first conductive type dopant, and the monocrystalline silicon substrate has a second conductive type dopant opposite to a conductive type of the first conductive type dopant.
3. The solar cell according to claim 1 , wherein the polycrystalline silicon back surface field area has a p-type conductivity, and
wherein the back passivation film includes at least one of aluminum oxide, zirconium oxide, and hafnium oxide having a negative charge.
4. The solar cell according to claim 1 , wherein the polycrystalline silicon back surface field area has an n-type conductivity, and
wherein the back passivation film includes at least one of silicon oxide and silicon nitride having a positive charge.
5. The solar cell according to claim 1 , further comprising:
an additional film on the back passivation film.
6. The solar cell according to claim 5 , wherein the additional film includes at least one selected from the group consisting of silicon nitride, silicon nitride containing hydrogen, silicon oxide, silicon oxide nitride, aluminum oxide, MgF 2 , ZnS, TiO 2 and CeO 2 .
7. The solar cell according to claim 1 , wherein a thickness of the tunneling oxide layer is about 0.5 nm to 5 nm.
8. The solar cell according to claim 1 , further comprising:
an additional back surface field area at a portion of the monocrystalline silicon substrate facing the tunneling oxide layer.
9. The solar cell according to claim 8 , wherein the additional back surface field area has a dopant having a conductive type the same as a conductive type of a dopant of the polycrystalline silicon back surface field area.
10. The solar cell according to claim 8 , wherein the additional back surface field area has the same crystalline structure as the monocrystalline silicon substrate.
11. The solar cell according to claim 1 ,
wherein the back electrode comprises a plurality of finger electrodes being disposed in parallel to each other.
12. The solar cell according to claim 1 , wherein the emitter area includes a first region that is directly contacted with the front electrode and a second region having a dopant concentration lower than a dopant concentration of the first region.
13. The solar cell according to claim 1 , wherein the back electrode is not directly formed on the back passivation film.
14. The solar cell according to claim 8 , wherein the emitter area and the additional back surface field area have about the same thickness of 5 nm to 100 nm.
15. The solar cell according to claim 10 , wherein the tunneling oxide layer is between the additional back surface field area and the polycrystalline silicon back surface field area.
16. The solar cell according to claim 1 , wherein the tunneling oxide layer and the back passivation film are separated by a distance of about 50 nm to 500 nm entirely based on a thickness of the polycrystalline silicon back surface field area.
17. The solar cell according to claim 16 , wherein the thickness of the polycrystalline silicon back surface field area is the same through the entire polycrystalline silicon back surface field area.
18. The solar cell according to claim 11 , wherein the back electrode further comprises a plurality of bus bar electrodes crossing the plurality of finger electrodes.
19. The solar cell according to claim 1 , wherein the thickness of the polycrystalline silicon back surface field area is 10 to 1,000 times a thickness of the tunneling oxide layer.