A solar cell includes a substrate of a first conductive type having at least one via hole; an emitter layer of a second conductive type opposite to the first conductive type; and at least one first electrode positioned from a first surface of the substrate to the at least one via hole, and at least one first electrode current collector positioned from the at least one via hole to a second surface of the substrate, wherein the at least one via hole has a radius of about 10 μm to about 40 μm, and at least one of a portion of the at least one first electrode and a portion of the at least one electrode current collector, in the at least one via hole, includes at least one cavity.
1. A solar cell, comprising:
a substrate of a first conductive type having a plurality of via holes, the plurality of via holes penetrating the substrate;
an emitter layer of a second conductive type opposite to the first conductive type; and
a plurality of first electrodes positioned from a first surface of the substrate to the plurality of via holes and being in contact with the emitter layer; and
a plurality of first electrode current collectors positioned from the plurality of via holes to a second surface of the substrate opposite the first surface,
wherein the plurality of via holes are positioned on a portion of the substrate on which the plurality of first electrodes and the plurality of first electrode current collectors cross and at least one of the plurality of first electrodes and at least one of the plurality of first electrode current collectors are positioned in at least one via hole of the plurality of via holes, and
wherein two cavities that are depressed into the plurality of via holes are positioned at crossed portions of the plurality of first electrodes and the plurality of via holes or at crossed portions of the plurality of first electrode current collectors and the plurality of via holes, and the two cavities have different diameters from each other.
2. The solar cell of claim 1 , wherein the at least one of the at least one first electrode and the at least one electrode current collector in the at least one via hole has a sectional area of about 300 μm 2 or more.
3. The solar cell of claim 2 , wherein the at least one first electrode and the at least one first electrode current collector are electrically connected to each other in the at least one via hole.
4. The solar cell of claim 1 , wherein the two cavities are exposed to at least one of the first surface and the second surface of the substrate.
5. The solar cell of claim 1 , wherein the at least one first electrode and the at least one first electrode current collector comprises the two cavities at the crossed portions of the plurality of first electrodes and the plurality of via holes and at the crossed portions of the plurality of first electrode current collectors, respectively, and one of the two cavities of included in the at least one first electrode has a different diameter from one of the two cavities included in the at least one first electrode current collector.
6. The solar cell of claim 1 , wherein the first surface of the substrate is an incident surface and the second surface of the substrate is positioned on a side opposite to the first surface.
7. The solar cell of claim 1 , further comprising:
a second electrode positioned on the second surface and electrically connected to the substrate.
8. The solar cell of claim 1 , wherein each of the plurality of via holes has a radius of about 10 μm to about 40 μm.
9. The solar cell of claim 7 , further comprising at least one second electrode current collector positioned on the second surface to be connected to the second electrode, and separated from the at least one first electrode current collector.