Solar cell
A solar cell comprises a substrate configured to have a plurality of via holes and a first conductive type, an emitter layer placed in the substrate and configured to have a second conductive type opposite to the first conductive type, a plurality of first electrodes electrically coupled to the emitter layer, a plurality of current collectors electrically coupled to the first electrodes through the plurality of via holes, and a plurality of second electrodes electrically coupled to the substrate. The plurality of via holes comprises at least two via holes having different angles.
1. A solar cell, comprising:
a substrate configured to have a plurality of via holes and a first conductive type;
an emitter layer placed at a first surface of the substrate and configured to have a second conductive type opposite to the first conductive type;
a plurality of first electrodes on the emitter layer and coupled to the emitter layer;
a plurality of first current collectors placed at a second surface of the substrate and into the plurality of via holes, and coupled to the first electrodes through the plurality of via holes, the second surface being opposite to the first surface with respect to the substrate;
a back surface field unit placed at the second surface of the substrate; and
a plurality of second electrodes placed on the back surface field unit and coupled to the back surface field unit,
wherein the plurality of via holes comprise at least two via holes having different angles, and the at least two angles are determined by the position on the substrate where the at least two via holes are formed.
2. A solar cell as claimed in claim 1 , wherein the at least two via holes have different horizontal sectional shapes.
3. A solar cell as claimed in claim 2 , wherein as the angle of the via hole increases, the horizontal sectional shape of the via hole becomes closer to a circle.
4. A solar cell as claimed in claim 1 , wherein the at least two via holes have different sectional areas.
5. A solar cell as claimed in claim 4 , wherein a size of the sectional area increases as the angle of the via hole decreases.
6. A solar cell as claimed in claim 1 , wherein each of the different angles is about 45° to 90° with the substrate.
7. A solar cell as claimed in claim 1 , further comprising a plurality of second current collectors placed on the second surface of the substrate and coupled to the plurality of second electrodes.
8. A solar cell as claimed in claim 7 , wherein the emitter layer is further placed at portions of the second surface of the substrate where the plurality of second current collectors are placed.
9. A solar cell as claimed in claim 1 , wherein the first surface is an incident surface and the second surface is a non-incident surface.
10. A solar cell as claimed in claim 1 , further comprising an anti-reflective layer placed on the emitter layer.