SOLAR CELL
Discussed is a solar cell including 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 front passivation film on the emitter area, a front electrode connected to the emitter area by penetrating through the front passivation film, 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 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 front passivation film on the emitter area;
a front electrode connected to the emitter area by penetrating through the front passivation film;
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.
2 . The solar cell according to claim 1 , wherein the emitter area is formed by diffusing a first conductive type dopant into the silicon substrate.
3 . The solar cell according to claim 2 , wherein the silicon substrate has a second conductive type dopant having a conductive type opposite to a conductive type of the first conductive type dopant.
4 . The solar cell according to claim 1 , wherein the back surface field area has a dopant having a conductive type the same as a conductive type of the silicon substrate.
5 . The solar cell according to claim 1 , wherein the back electrode is directly contacted with the back surface field area.
6 . The solar cell according to claim 1 , wherein the 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.
7 . The solar cell according to claim 1 , wherein the 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.
8 . The solar cell according to claim 1 , further comprising:
an additional film on the back passivation film.
9 . The solar cell according to claim 8 , 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 .
10 . The solar cell according to claim 1 , wherein the tunneling oxide layer has a thickness of about 0.5 nm to 5 nm.
11 . The solar cell according to claim 1 , further comprising:
an additional back surface field area at a portion of the silicon substrate facing the tunneling oxide layer.
12 . The solar cell according to claim 11 , 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 back surface field area.
13 . The solar cell according to claim 11 , wherein the additional back surface field area has the same crystalline structure as the silicon substrate.
14 . The solar cell according to claim 1 , wherein the silicon substrate is formed of a monocrystalline silicon substrate.
15 . The solar cell according to claim 1 , further comprising:
an additional film on the back passivation film,
wherein the back electrode comprises a plurality of finger electrodes disposed in parallel to each other with a regular pitch, and
wherein a portion of the additional film exposed between the plurality of finger electrodes acts as an anti-reflection film for preventing reflection of light incident through the back surface of the silicon substrate.
16 . 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.
17 . The solar cell according to claim 1 , wherein a crystalline structure of the emitter area is the same with a crystalline structure of the silicon substrate and different from a crystalline structure of the back surface field area.
18 . The solar cell according to claim 1 , wherein the back electrode is not directly formed on the back passivation film.
19 . The solar cell according to claim 1 , wherein a thickness of the back surface field area is about 50 nm to 500 nm.
20 . The solar cell according to claim 1 , wherein a thickness of the 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 is different from that of the monocrystalline silicon substrate and that of the emitter area.