Solar cell and manufacturing method thereof

A method for manufacturing a solar cell, the method comprising:

• forming an emitter region of a second conductivity type on a front surface of a substrate having a first conductivity type that is opposite to the second conductivity type;
• forming an anti-reflection layer on the emitter region;
• forming a passivation layer on a rear surface of the substrate;
• forming via holes in the passivation layer so that portions of the rear surface of the substrate are exposed through the passivation layer, wherein the via holes are formed by irradiating a laser to the passivation layer;
• applying a connecting electrode in the via holes by using a first paste having aluminum;
• applying a bus bar on the passivation layer by using a second paste having silver, wherein the bus bar is spaced apart from the connecting electrode on the passivation layer;
• applying a front electrode on a front surface of the anti-reflection layer by using the second paste having silver;
• performing a first firing operation of firing the connecting electrode, the bus bar and the front electrode at a first temperature;
• forming a rear electrode layer by using a third paste having aluminum on an entire rear surface of the passivation layer except for an area where the bus bar is formed;
• and
• performing a second firing operation of firing the rear electrode layer at a second temperature lower than the first temperature,
• wherein the first firing operation simultaneously performs the following processes:
• (1) a back surface field region being formed at an interface between the rear surface of the substrate and the connecting electrode;
• (2) the bus bar penetrating into the passivation layer and being contacted to the rear surface of the substrate;
• and
• (3) the front electrode penetrating into the anti-reflection layer and being connected to the emitter region.