Solar cell and method for manufacturing the same
A solar cell can include a silicon semiconductor substrate; an oxide layer on a first surface of the silicon semiconductor substrate; a polysilicon layer on the oxide layer; a diffusion region at a second surface of the silicon semiconductor substrate; a dielectric film on the polysilicon layer; a first electrode connected to the polysilicon layer through the dielectric film; a passivation film on the diffusion region; and a second electrode connected to the diffusion region through the passivation film.
1. A solar cell, comprising:
a single-crystal silicon semiconductor substrate;
a polysilicon back surface field layer formed on a first surface of the single-crystal silicon semiconductor substrate;
an oxide layer disposed between the single-crystal silicon semiconductor substrate and the polysilicon back surface field layer;
an emitter region formed at a second surface of the single-crystal silicon semiconductor substrate;
a dielectric film covering the polysilicon back surface field layer;
a first electrode connected to the polysilicon back surface field layer through the dielectric film;
a passivation film on the emitter region; and
a second electrode connected to the emitter region through the passivation film,
wherein a contact area in which the first electrode is connected to the polysilicon back surface field layer, includes a plurality of metal crystals extracted from the first electrode,
wherein a height difference between a first interface, which is an interface between the first electrode and the polysilicon back surface field layer, and a second interface, which is an interface between the polysilicon back surface field layer and the dielectric film, is 1 nm-20 nm,
wherein the plurality of metal crystals are mostly formed at the polysilicon back surface field layer and are not extended to the oxide layer and the single-crystal silicon semiconductor substrate in order to prevent damage of the oxide layer or the single-crystal silicon semiconductor substrate,
wherein the first electrode includes a plurality of first finger electrodes extending in a first direction and a first bus bar extending in a second direction crossing the first direction, and
wherein an amount of glass frit per unit volume in the plurality of first finger electrodes is less than an amount of glass frit per unit volume in the first bus bar.
2. The solar cell of claim 1 ,
wherein the second electrode comprises a plurality of second finger electrodes spaced apart from each other and extended in parallel in the first direction.
3. The solar cell of claim 2 ,
wherein the second electrode further comprises a second bus bar connected to the plurality of second finger electrodes.
4. The solar cell of claim 1 , further comprising an isolation portion for preventing a contact between the polysilicon back surface field layer and the emitter region,
wherein the isolation portion is formed on at least one of the first surface of the single-crystal silicon semiconductor substrate, a side surface of the single-crystal silicon semiconductor substrate, or the second surface of the single-crystal silicon semiconductor substrate.
5. The solar cell of claim 4 , wherein the isolation portion excludes the oxide layer and the polysilicon back surface field layer, and is in an edge portion of the first surface of the single-crystal silicon semiconductor substrate, and
wherein the dielectric film covers the first surface of the single-crystal silicon semiconductor substrate and the isolation portion together.
6. The solar cell of claim 4 , wherein a width of the isolation portion is 1 nm to 1 mm.
7. The solar cell of claim 4 , wherein a thickness of an edge region in the polysilicon back surface field layer progressively decreases toward the isolation portion.
8. The solar cell of claim 1 , wherein the dielectric film comprises a side portion extending up a side surface of the single-crystal silicon semiconductor substrate.
9. The solar cell of claim 8 , wherein the passivation film comprises a side portion formed on the side surface of the single-crystal silicon semiconductor substrate, and
wherein the side portion of the dielectric film on the side surface of the single-crystal silicon semiconductor substrate is on the side portion of the passivation film.
10. The solar cell of claim 1 , wherein the second surface of the single-crystal silicon semiconductor substrate is a light incident surface, the first surface of the single-crystal silicon semiconductor substrate is a back surface of the single-crystal silicon semiconductor substrate.
11. The solar cell of claim 3 , wherein all of the plurality of first finger electrodes and the first bus bar are connected to the polysilicon back surface field layer through the dielectric film.
12. The solar cell of claim 11 , wherein all of the plurality of first finger electrodes and the first bus bar have a single layer structure or a double layer structure.
13. The solar cell of claim 11 , wherein the plurality of first finger electrodes have a single layer structure, and
wherein the first bus bar has a double layer structure.
14. The solar cell of claim 1 , wherein the dielectric film and the passivation film are formed of a plurality of layers.
15. The solar cell of claim 1 , wherein a thickness of the polysilicon back surface field layer is greater than a thickness of the dielectric film.
16. The solar cell of claim 1 , wherein the plurality of metal crystals include first metal crystals which directly contact with the first electrode, and second crystals which are spaced apart from the first electrode and formed in the polysilicon back surface field layer.