Solar cell and method of manufacturing the same
A solar cell includes a semiconductor substrate, a first semiconductor region positioned at a front surface or a back surface of the semiconductor substrate and doped with impurities of a first conductive type, a first electrode on the first semiconductor region, a second electrode on the back surface of the semiconductor substrate, and a second semiconductor region positioned between the semiconductor substrate and the second electrode and doped with impurities of a second conductive type opposite the first conductive type, wherein the second electrode is formed of a metal foil, and an air gap is formed between the second electrode formed of the metal foil and the back surface of the semiconductor substrate.
1. A solar cell comprising:
a semiconductor substrate;
a first semiconductor region positioned at a front surface or a back surface of the semiconductor substrate and doped with impurities of a first conductive type;
a first electrode on the first semiconductor region;
a second electrode on the back surface of the semiconductor substrate; and
a second semiconductor region positioned between the semiconductor substrate and the second electrode and doped with impurities of a second conductive type opposite the first conductive type, the second semiconductor region having a plurality of concave-convex portions,
wherein the second electrode is formed of a metal foil, and an air gap is formed between the second electrode formed of the metal foil and a back surface of the second semiconductor region,
wherein the second electrode formed of the metal foil includes:
a contact portion on the back surface of the second semiconductor region; and
a non-contact portion that is spaced apart from the back surface of the second semiconductor region to form the air gap between the second electrode and the back surface of the second semiconductor region,
wherein the contact portion of the second electrode has a protrusion that projects toward a concave portion of the plurality of concave-convex portions of the second semiconductor region and is connected to the second semiconductor region, and
wherein the non-contact portion of the second electrode is spaced apart from the second semiconductor region by the air gap.
2. The solar cell of claim 1 , wherein the second semiconductor region contacts the contact portion of the second electrode, and
wherein an impurity doping concentration of a portion of the second semiconductor region contacting the contact portion of the second electrode is higher than an impurity doping concentration of a portion of the second semiconductor region not contacting the contact portion of the second electrode.
3. The solar cell of claim 1 , further comprising a metal electrode layer positioned between the second semiconductor region and the second electrode formed of the metal foil, and the metal electrode layer being entirely connected to the semiconductor substrate and having a plurality of concave-convex portions,
wherein the contact portion of the second electrode contacts the metal electrode layer, and the non-contact portion of the second electrode is spaced apart from the metal electrode layer by the air gap.
4. The solar cell of claim 1 , further comprising a back passivation layer positioned between the second semiconductor region and the second electrode formed of the metal foil, the back passivation layer being formed of a dielectric material and having a plurality of concave-convex portions,
wherein the contact portion of the second electrode passes through the back passivation layer and contacts the second semiconductor region, and
wherein the non-contact portion of the second electrode is spaced apart from the back passivation layer by the air gap.
5. The solar cell of claim 4 , further comprising a conductive contact electrode passing through the back passivation layer and further positioned between the contact portion of the second electrode and the second semiconductor region.
6. The solar cell of claim 1 , wherein the semiconductor substrate is formed of a crystalline silicon material,
wherein the second semiconductor region is formed of an amorphous silicon material,
wherein a transparent electrode layer is positioned at the back surface of the second semiconductor region formed of the amorphous silicon material and has a plurality of concave-convex portions,
wherein the contact portion of the second electrode contacts the transparent electrode layer, and
wherein the non-contact portion of the second electrode is spaced apart from the transparent electrode layer by the air gap.
7. The solar cell of claim 6 , further comprising a conductive contact electrode positioned between the contact portion of the second electrode and the transparent electrode layer.
8. The solar cell of claim 1 , wherein the metal foil of the second electrode directly includes a planar portion that corresponds to the plurality of concave-convex portions of the second semiconductor region.