SOLAR CELL
Discussed is a solar cell including a semiconductor substrate comprising a base region, an emitter region having a conductive type opposite to that of the base region, and a back surface field region having the same conductive type as the base region and a higher doping concentration than the base region, and a first electrode and a second electrode respectively connected to the emitter region and the back surface field region, wherein the base region has a specific resistance of 0.3 Ωcm to 2.5 Ωcm.
1 . A solar cell comprising:
a semiconductor substrate having:
a base region;
an emitter region having a conductivity type opposite to that of the base region, the emitter region being disposed on a front surface of the semiconductor substrate; and
a plurality of back surface field regions having the same conductivity type as the base region and a doping concentration higher than the base region, the plurality of back surface field regions being locally disposed on a back surface of the semiconductor substrate and separated from each other so that the base region is located between the plurality of back surface field regions from the back surface of the semiconductor substrate;
a first passivation layer disposed on the emitter region;
a plurality of first electrodes connected to the emitter by penetrating through the first passivation layer,
a second passivation layer disposed on the back surface of the semiconductor substrate;
a capping film disposed on the second passivation layer; and
a plurality of second electrodes connected to the plurality of back surface field regions, respectively, by penetrating through the second passivation layer,
wherein the plurality of second electrodes includes a plurality of finger electrodes extending in a first direction and least one bus bar electrode extending in a second direction crossing the first direction and connecting the plurality of finger electrodes,
wherein the solar cell has a bi-facial structure that receives light to the back surface of the semiconductor substrate through the second passivation layer and receives light to the front surface of the semiconductor substrate through the first passivation layer,
wherein the capping film includes aluminium oxide, the capping film is an outermost film on the back surface of the semiconductor substrate, the capping film covers only a part of the back surface of the semiconductor substrate.
2 . The solar cell according to claim 1 , wherein the capping film is adapted to prevent a material for forming the plurality of second electrodes from diffusing into the second passivation layer in a process of forming the plurality of second electrodes.
3 . The solar cell according to claim 1 , wherein the base region has a specific resistance of 0.3 Ωcm to 2.5 Ωcm.
4 . The solar cell according to claim 3 , wherein the specific resistance of the base region is 0.76 Ωcm to 1.05 Ωcm.
5 . The solar cell according to claim 1 , wherein a ratio of a total area of the plurality of back surface field regions to a total area of the back surface of the semiconductor substrate is 1:10 to 1:2.
6 . The solar cell according to claim 1 , wherein the base region and the plurality of back surface field regions are n-type, and the emitter region is p-type.
7 . The solar cell according to claim 1 , wherein the plurality of back surface field regions has a doping concentration of 3×10 15 /cm 3 to 15×10 15 /cm 3 .
8 . The solar cell according to claim 1 , wherein the plurality of the back surface field regions has a sheet resistance of 5 Ω/sq to 90 Ω/sq.
9 . The solar cell according to claim 1 , wherein a width of at least one of the plurality of the back surface field regions is greater than a width of a corresponding second electrode.
10 . The solar cell according to claim 9 , wherein the width of the at least one of the plurality of the back surface field regions is 200 μm to 1,000 μm, and the width of the corresponding second electrode is 30 μm to 300 μm.
11 . The solar cell according to claim 1 , wherein a distance between two adjacent back surface field regions of the plurality of back surface field regions is greater than a width of at least one of the plurality of back surface field regions.
12 . The solar cell according to claim 1 , wherein the second passivation layer includes a silicon nitride film.
13 . The solar cell according to claim 12 , wherein the base region and the plurality of back surface field regions are n-type, the second passivation layer is in direct contact with the back surface of the semiconductor substrate, and the silicon nitride film has a fixed positive charge based on the plurality of back surface field regions having the n-type.