Solar cell and method for manufacturing the same
A solar cell includes a semiconductor substrate having a first conductivity type, an emitter layer on a surface of the semiconductor substrate, the emitter layer having a second conductivity type different from the first conductivity type, and electrodes including a first electrode electrically connected to the emitter layer, and a second electrode electrically connected to the semiconductor substrate. The emitter layer includes a high-concentration doping portion adjacent to the first electrode, and a low-concentration doping portion in a region that does not include the high-concentration doping portion. The low-concentration doping portion has a higher resistance than the high-concentration doping portion. The high-concentration doping portion includes a first region having a first resistance, and a second region having a second resistance higher than the first resistance.
1. A method for manufacturing a solar cell, comprising:
forming an impurity layer at a semiconductor substrate,
wherein the forming the impurity layer comprises
forming a low-concentration doping portion including a first low-concentration doping portion and a second low-concentration doping portion by doping impurities into the semiconductor substrate; and
forming a high-concentration doping portion including a first high-concentration doping portion and a second high-concentration doping portion having a lower resistance than the low-concentration doping portion by selectively applying heat to a glass composition layer formed over the low-concentration doping portion,
wherein the first low-concentration doping portion is formed at front and back surface of the semiconductor substrate,
wherein the first high-concentration doping portion is formed at the first low-concentration doping portion of the front surface of the semiconductor substrate, and
wherein the second low-concentration doping portion is formed at the back surface of the semiconductor substrate after the first low-concentration doping portion of the back surface of the semiconductor substrate is removed,
wherein the second high-concentration doping portion is formed at the second low concentration doping portion of the black surface of the semiconductor substrate,
wherein the forming of the high-concentration doping portion comprises forming a first region having a first resistance, and a second region having a higher resistance than the first resistance,
each of depths of the first region, the second region and low-concentration doping portion is uniform,
the second region is located between the first region and low-concentration doping portion, and
low-concentration doping portion is located between adjacent the second regions.
2. The method according to claim 1 , wherein the forming the high-concentration doping portion comprises irradiating the glass composition layer with a laser beam.
3. The method according to claim 2 , wherein the laser beam, which irradiate the first region and the second region during the formation of the high-concentration doping portion, respectively, have different power level.
4. The method according to claim 2 , wherein the forming the high-concentration doping portion is performed such that the second region is formed at an outside of the first region after formation of the first region, or the first region is formed after formation of the second region.
5. The method according to claim 2 , wherein the second region comprises regions respectively arranged at opposite sides of the first region.
6. The method according to claim 1 , further comprising:
removing the glass composition layer after the formation of the high-concentration doping portion.
7. The method according to claim 1 , wherein the glass composition layer comprises phosphorous silicate glass (PSG) or boron silicate glass (BSG).
8. The method according to claim 6 , further comprising:
forming an insulating layer over the impurity layer after the removal of the glass composition layer;
coating an electrode composition layer over the insulating layer;
subjecting the electrode composition layer to a heat treatment; and
subjecting the heat-treated electrode composition layer to a fire-through process, thereby forming an electrode electrically connected to the impurity layer,
wherein at least a portion of the electrode contacts the first region.
9. The method according to claim 1 , wherein the impurity layer comprises an emitter layer having a conductivity type different from a conductivity type of the semiconductor substrate.
10. The method according to claim 1 , wherein the impurity layer comprises a back surface field layer having a same conductivity type as a conductivity type of the semiconductor substrate.