Solar cell and methods for manufacturing the same
A method for manufacturing a solar cell according to an embodiment of the invention includes forming an emitter layer having an emitter dopant of a second conductive type opposite to a first conductive type on a first surface on a semiconductor substrate; forming a passivation layer including a first dopant of the first conductive type on a second surface of the semiconductor substrate; forming a back surface field layer including a first portion on the second surface by locally heating a portion of the passivation layer using a laser; and forming an electrode electrically connected to the first portion of the back surface field layer through an opening of the passivation layer after the first portion of the back surface field layer is formed on the second surface, wherein the back surface field layer is locally formed between the electrode and the second surface.
1. A method for manufacturing a solar cell, the method comprising:
preparing a semiconductor substrate having a base dopant of a first conductive type;
forming an emitter layer having a first dopant of a second conductive type opposite to the first conductive type and a first doping concentration, and on a first surface on the semiconductor substrate;
forming an aluminum oxide passivation layer on the emitter layer;
forming an anti-reflection layer on the aluminum oxide passivation layer;
selectively irradiating a laser to the anti-reflection layer to diffuse an aluminum of the aluminum oxide passivation layer into a portion of the emitter layer, thereby forming a high doping portion of the emitter layer having a second doping concentration higher than the first doping concentration of the emitter layer, wherein the high doping portion includes the first dopant and the aluminum diffused from the aluminum oxide passivation layer, and the high doping portion has a thickness thicker than the emitter layer;
forming a first electrode having a plurality of metal layers stacked to each other on the high doping portion through an opening of the aluminum oxide passivation layer and the anti-reflection layer;
forming a back surface field layer having a third doping concentration on a second surface on the semiconductor substrate; and
forming a second electrode on the back surface field layer,
wherein the emitter layer is formed before the aluminum oxide passivation layer is formed,
wherein the opening is formed at the same time as the high doping portion is formed, and after the emitter layer and the aluminum oxide passivation layer are formed,
wherein the first dopant is a different element from aluminum, and
wherein, in the forming of the high doping portion of the emitter layer, a portion of the aluminum oxide passivation layer corresponding to the high doping portion of the emitter layer is heated to a temperature of about 1200 to 1600° C.
2. The method according to claim 1 , wherein the opening is formed by the laser at the portion of aluminum oxide passivation layer corresponding to the high doping portion of the emitter layer in the forming of the emitter layer.
3. The method according to claim 1 , wherein the aluminum oxide passivation layer has a thickness of 5 to 20 nm.
4. The method according to claim 1 , wherein the high doping portion comprises a plurality of high doping portions locally formed and spaced from each other,
wherein a portion of the aluminum oxide passivation layer heated by the laser comprises a plurality of portions of the aluminum oxide passivation layer spaced from each other, and
wherein the plurality of high doping portions correspond to the plurality of portions of the aluminum oxide passivation layer, respectively.
5. The method according to claim 1 , further comprising:
forming another passivation layer including a first conductive type dopant at the second surface of the semiconductor substrate,
wherein the back surface field layer comprises another high doping portion comprising the first conductive type dopant and in contact with the second electrode,
wherein, in the forming of the back surface field layer, a portion of the another passivation layer corresponding to the another high doping portion of the back surface field layer being heated and the first conductive type dopant being diffused into the semiconductor substrate results in the another high doping portion having a fourth doping concentration greater than the third doping concentration, and
wherein the first conductive type dopant comprises bismuth.
6. The method according to claim 1 , wherein the aluminum from the aluminum oxide passivation layer is included only in the high doping portion of the emitter layer.
7. The method according to claim 1 , wherein the high doping portion of the emitter layer includes aluminum and the first dopant, and another portion of the emitter layer only includes the first dopant.
8. The method according to claim 1 , wherein the first electrode having the plurality of metal layers stacked to each other is formed by a plating method.
9. The method according to claim 1 , wherein a width of the hole is approximately the same as a width of the high doping portion.
10. The method according to claim 1 , wherein only the portion of the aluminum oxide passivation layer corresponding to the high doping portion of the emitter layer is heated to the temperature of about 1200 to 1600° C. in the forming of the high doping portion of the emitter layer.