Tandem thin-film silicon solar cell and method for manufacturing the same
A tandem thin-film silicon solar cell comprises a transparent substrate, a first unit cell positioned on the transparent substrate, the first unit cell comprising a p-type window layer, an i-type absorber layer and an n-type layer, an intermediate reflection layer positioned on the first unit cell, the intermediate reflection layer including a hydrogenated n-type microcrystalline silicon oxide of which the oxygen concentration is profiled to be gradually increased and a second unit cell positioned on the intermediate reflection layer, the second unit cell comprising a p-type window layer, an i-type absorber layer and an n-type layer.
1. A method for manufacturing a tandem thin-film silicon solar cell, comprising:
coating a first electrode layer on a substrate;
removing a portion of the first electrode layer to form a first separation trench using a first patterning process, thereby forming a plurality of first electrodes;
forming a first unit cell layer on the plurality of first electrodes and in the first separation trench, the first unit cell layer comprising a p-type window layer, an i-type absorber layer and an n-type layer;
forming an intermediate reflection layer comprising a hydrogenated n-type microcrystalline silicon oxide of which an oxygen concentration is profiled to be gradually increased from the light incident side;
forming a second unit cell layer on the intermediate reflection layer;
removing portions of the first and second unit cell layers to form a second separation trench using a second patterning process;
stacking a second electrode layer on the second unit cell layer and in the second separation trench formed using the second patterning process; and
removing a portion of the second electrode layer to form a third separation trench using a third patterning process.
2. The method according to claim 1 , wherein the intermediate reflection layer is formed by oxidizing the n-type layer of the first unit cell layer, and an oxygen source gas for forming the intermediate reflection layer comprises carbon dioxide or oxygen.
3. The method according to claim 1 , wherein the intermediate reflection layer has a refractive index of around 2.0.
4. The method according to claim 1 , wherein the intermediate reflection layer has a thickness of 10 to 100 nm.
5. The method according to claim 1 , wherein the intermediate reflection layer has a specific resistivity of 10 2 to 10 5 Ωcm.
6. The method according to claim 1 , wherein two or three unit cell layers are formed.
7. The method according to claim 1 , wherein the intermediate reflection layer is formed on the first unit cell layer, and the n-type layer of the first unit cell layer has a thickness of 30 to 50 nm and comprises hydrogenated n-type microcrystalline silicon.
8. The method according to claim 1 , wherein the intermediate reflection layer is formed by oxidizing the n-type layer of the first unit cell layer, and the n-type layer of the first unit cell layer has a thickness of 40 to 150 nm and comprises hydrogenated n-type microcrystalline silicon.
9. The method according to claim 1 , wherein the intermediate reflection layer is formed on the n-type layer of the first unit cell layer, and the deposition temperature and deposition pressure for stacking the n-type layer of the first unit cell layer are maintained.
10. The method according to claim 9 , wherein the n-type layer of the first unit cell layer and the intermediate reflection layer are formed in the same reaction chamber.
11. The method according to claim 1 , wherein the intermediate reflection layer is formed on the first unit cell layer, and the pressure fraction of the oxygen source gas for forming the intermediate reflection layer is increased and then maintained constant, or the flow of the oxygen source gas is increased through multiple steps.
12. The method according to claim 1 , wherein the intermediate reflection layer is formed by oxidizing the n-type layer of the first unit cell layer, and plasma for forming the n-type layer of the first unit cell layer is turned off, the oxygen source layer for forming the intermediate reflection layer is introduced, and the plasma is then turned on.
13. A method for manufacturing a tandem thin-film silicon solar cell, comprising:
coating a first electrode layer on a substrate;
removing a portion of the first electrode layer to form a first separation trench using a first patterning process, thereby forming a plurality of first electrodes;
forming a first unit cell layer on the plurality of first electrodes and in the first separation trench;
forming an intermediate reflection layer comprising a hydrogenated n-type microcrystalline silicon oxide of which an oxygen concentration is profiled to be gradually increased from the light incident side;
forming a second unit cell layer on the intermediate reflection layer;
removing portions of the first and second unit cell layers to form a second separation trench using a second patterning process;
stacking a second electrode layer on the second unit cell layer and in the second separation trench formed using the second patterning process; and
removing a portion of the second electrode layer to form a third separation trench using a third patterning process.
14. The method according to claim 13 , wherein the first unit cell layer comprises a p-type window layer, an i-type absorber layer and an n-type layer.