Solar cell and solar cell panel including the same

1. A solar cell panel comprising:

a plurality of solar cells; and a wire for interconnecting two neighboring solar cells among the solar cells, the wire having a circular core and a solder layer surrounding the circular core,

wherein each of the solar cells includes:

a semiconductor substrate;

a first electrode formed on a first surface of the semiconductor substrate;

a second electrode formed on a second surface of the semiconductor substrate;

a second pad electrode connected to the second electrode,

wherein the second electrode and the second pad electrode are spaced apart from each other in a first direction so as to form a gap portion therebetween such that the second electrode and the second pad electrode define the gap portion,

wherein the second electrode and the second pad electrode overlap each other in a second direction crossing the first direction,

wherein the wire includes a first portion disposed on the second pad electrode and a second portion disposed on the gap portion or the second electrode,

wherein a distance between the second portion of the wire disposed on the second electrode and the substrate is gradually reduced over the gap portion until the first portion of the wire comes in contact with the second pad electrode,

wherein a width of the first portion is greater than a width of the second portion by soldering the solder layer on the second pad electrode,

wherein the width of the first portion is smaller than a width of the second pad electrode, and the width of the second portion is smaller than a width of the gap portion in the second direction, and

wherein an overlap portion is formed on each of both sides of the second pad electrode in the second direction along both sides of the gap portion in a rectangular shape having a same length as the second pad electrode in the first direction, and each of the overlap portions that are formed on each of the both sides of the second pad electrode having a same width in the second direction; and

a passivation film directly disposed on the second surface of the semiconductor substrate,

wherein the passivation film is locally formed so as to correspond to only an area defined by the second pad electrode and the gap portion such that the passivation film is between the second surface of the semiconductor substrate and a surface defined by the second pad electrode and the gap portion and in direct contact with the surface defined by the second pad electrode and the gap portion, and

wherein a side surface of the passivation film is in direct contact with the second electrode.

2. The solar cell panel according to claim 1 , wherein the wire connects the second pad electrode and the second electrode to one another.

3. The solar cell panel according to claim 1 , wherein the wire has a width smaller than a length of the gap portion in the first direction.

4. The solar cell panel according to claim 3 , wherein a ratio of the width of the wire to the length of the gap portion in the first direction ranges from 1:10 to 1:15.

5. The solar cell panel according to claim 1 , wherein a rate of a portion of the second pad electrode attached to the wire is 95% or more.

6. The solar cell panel according to claim 1 , wherein six to thirty-three wires are provided on one surface of each solar cell, and

wherein the wire has the width ranging from 250 μm to 500 μm.

7. The solar cell panel according to claim 1 , wherein, the gap portion is located on either side of the second pad electrode in the first direction.

8. The solar cell panel according to claim 1 , wherein the overlap portion has the width in the second direction, and the width of the overlap portion in the second direction is smaller than a length of the gap portion in the first direction.

9. The solar cell panel according to claim 1 , wherein the second electrode includes an opening corresponding to the second pad electrode,

wherein the opening has a width smaller than the width of the second pad electrode so that the second electrode and the second pad electrode overlap each other in the second direction, and

wherein the opening has a length larger than a length of the second pad electrode so that the gap portion is located between the second electrode and the second pad electrode in the first direction.

10. The solar cell panel according to claim 1 , wherein the second pad electrode includes a plurality of second pad electrodes spaced apart from one another in the first direction so as to form a single row, and

wherein two second pad electrodes, located close to each other, among the second pad electrodes have a first distance therebetween, and the first distance is larger than a second distance between an edge of the semiconductor substrate and the second pad electrode located close to the edge.

11. The solar cell panel according to claim 1 , wherein the second pad electrode has a thickness smaller than a thickness of the second electrode.

12. The solar cell panel according to claim 1 , wherein the second electrode and the second pad electrode have a thickness difference smaller than a length of the gap portion in the first direction.

13. The solar cell panel according to claim 12 , wherein the thickness difference between the second electrode and the second pad electrode ranges from 5 μm to 30 μm, and

wherein the length of the gap portion in the first direction ranges from 0.5 mm to 3 mm.

14. The solar cell panel according to claim 13 , wherein a ratio of the thickness difference between the second electrode and the second pad electrode to the length of the gap portion ranges from 1:60 to 1:100.

15. The solar cell panel according to claim 1 , wherein the first electrode includes a plurality of finger electrodes arranged in parallel in the second direction, and a plurality of bus-bar lines or rows of first pad electrodes extending in the first direction, and

wherein a number of the plurality of bus-bar lines or the rows of the first pad electrodes is six to thirty-three.

16. The solar cell panel according to claim 1 , wherein the gap portion has an exposed region which is not covered by the wire, and

wherein the solder layer contacting the second pad electrode is spread on a surface of the second pad electrode.

17. The solar cell panel according to claim 1 , wherein the solar cell further comprises an emitter formed on the first surface of the semiconductor substrate and a back surface field formed on the second surface of the semiconductor substrate, and

wherein the first electrode is connected to the emitter and the second electrode is connected to the back surface field.

18. The solar cell panel according to claim 1 , wherein the gap portion includes a space that is located between the wire and the passivation layer in a thickness direction of the passivation layer, and

wherein the second pad electrode extends from the first portion to the second portion in the first direction.