Bifacial solar cell

1. A bifacial solar cell comprising:

a substrate;

an emitter portion disposed on a first surface of the substrate;

a plurality of first electrodes directly contacted with the emitter portion and extended in a first direction;

a plurality of first current collectors extended in a second direction crossing the first direction, wherein the plurality of first current collectors are electrically and physically connected to the plurality of first electrodes;

a back surface field disposed on a second surface of the substrate, and having an impurity concentration that is higher than an impurity concentration of the substrate;

a plurality of second electrodes directly contacted with the back surface field and extended in the first direction; and

a plurality of second current collectors extended in the second direction, the plurality of second current collectors being electrically and physically connected to the plurality of second electrodes,

wherein a number of the plurality of second electrodes is more than a number of the plurality of first electrodes, wherein each of the plurality of second electrodes is positioned on a different reference line from a reference line of each of the plurality of first electrodes, and the first electrodes and the second electrodes are not overlapped with each other and a portion where the first electrodes and the second electrodes are overlapped does not exist,

wherein two neighboring first electrodes of the plurality of first electrodes are spaced apart from each other by a first pitch P 1 , and two neighboring second electrodes of the plurality of second electrodes are spaced apart from each other by a second pitch P 2 , and

wherein a ratio n of the first pitch P 1 and the second pitch P 2 satisfies an equation: 0.1<n<1, where n=P 2 /P 1 .

2. The bifacial solar cell of claim 1 , wherein each of the plurality of first electrodes has a line width of less than 60 μm and a thickness of more than 10 μm.

3. The bifacial solar cell of claim 1 , wherein each of the plurality of second electrodes has a line width of less than 70 μm and a thickness of more than 10 μm.

4. The bifacial solar cell of claim 1 , wherein the substrate is of a first conductive type, and

wherein the emitter portion is of a second conductive type opposite the first conductive type.

5. The bifacial solar cell of claim 4 , further comprising a first insulating film provided on a surface of the emitter portion at portions where the plurality of first electrodes and the plurality of first current collectors are not provided.

6. The bifacial solar cell of claim 4 , further comprising a second insulating film provided on a surface of the back surface field at portions where the plurality of second electrodes and the plurality of second current collectors are not provided.

7. The bifacial solar cell of claim 1 , wherein two neighboring second electrodes of the plurality of second electrodes are disposed within each spacing of two neighboring first electrodes of the plurality of first electrodes.

8. The bifacial solar cell of claim 5 , wherein the plurality of first electrodes are directly contacted to the emitter portion through openings of the first insulating film.

9. The bifacial solar cell of claim 6 , wherein the plurality of second electrodes are directly contacted to the back surface field through openings of the second insulating film.