Photovoltaic device including flexible or inflexibel substrate and method for manufacturing the same

1. A photovoltaic device comprising:

a first electrode and a second electrode;

a first unit cell and a second unit cell which are placed between the first electrode and the second electrode, wherein each of the first unit cell and the second unit cell comprises a first conductive semiconductor layer, an intrinsic semiconductor layer and a second conductive semiconductor layer; and

an intermediate reflector which is placed between the first unit cell and the second unit cell, and comprises an n-type hydrogenated amorphous carbon layer containing only hydrogen, carbon and n-type impurity;

wherein the intermediate reflector further comprises an n-type nanocrystalline silicon layer contacting with a unit cell which is farther from a light incident side between the first unit cell and the second unit cell, and

wherein a refractive index in the n-type hydrogenated amorphous carbon layer is profiled such that the farther it is from the light incident side, the larger the refractive index in the n-type hydrogenated amorphous carbon layer is.

2. The photovoltaic device of claim 1 , wherein an optical band gap of the n-type hydrogenated amorphous carbon layer is larger than optical band gaps of the first conductive semiconductor layer and the second conductive semiconductor layer of a unit cell which is closer to the light incident side between the first unit cell and the second unit cell.

3. The photovoltaic device of claim 1 , wherein a thickness of the n-type hydrogenated amorphous carbon layer is equal to or more than 1 nm and equal to or less than 20 nm.

4. The photovoltaic device of claim 1 , wherein the second conductive semiconductor layer of a unit cell which is closer to the light incident side between the first unit cell and the second unit cell is an n-type nanocrystalline silicon layer.

5. The photovoltaic device of claim 1 , wherein a thickness of the n-type nanocrystalline silicon layer is equal to or more than 5 nm and equal to or less than 30 nm.

6. The photovoltaic device of claim 1 , wherein the intermediate reflector comprises at least two pairs of the n-type hydrogenated amorphous carbon layer and the n-type nanocrystalline silicon layer, wherein the n-type hydrogenated amorphous carbon layer and the n-type nanocrystalline silicon layer are alternately stacked in the intermediate reflector.

7. The photovoltaic device of claim 6 , wherein a thickness of the n-type hydrogenated amorphous carbon layer is equal to or more than 1 nm and equal to or less than 20 nm.

8. The photovoltaic device of claim 1 , wherein an optical band gap of the n-type hydrogenated amorphous carbon layer is equal to or more than 2.2 eV and equal to or less than 3.0 eV.

9. The photovoltaic device of claim 1 , wherein, when the n-type hydrogenated amorphous carbon layer is measured by Raman spectroscopy, there is a peak corresponding to at least one of G-band and D-band at between 1200 cm −1 and 1400 cm −1 .

10. The photovoltaic device of claim 1 , wherein the refractive index of the n-type hydrogenated amorphous carbon layer is equal to or more than 1.5 and equal to or less than 2.2 at a wavelength of 600 nm.

11. The photovoltaic device of claim 1 , wherein an average hydrogen content of the n-type hydrogenated amorphous carbon layer is equal to or more than 5 atomic % and equal to or less than 40 atomic %.

12. A photovoltaic device comprising:

a first electrode and a second electrode;

a first unit cell and a second unit cell which are placed between the first electrode and the second electrode, wherein each of the first unit cell and the second unit cell comprising a p-type conductive semiconductor layer, an intrinsic semiconductor layer, and an n-type conductive semiconductor layer; and

an intermediate reflector which is placed between the first unit cell and the second unit cell, wherein the intermediate reflector comprising two layers including an n-type hydrogenated amorphous carbon layer and an n-type nanocrystalline silicon layer, the n-type hydrogenated amorphous carbon layer contains only hydrogen, carbon and n-type impurity;

wherein the n-type nanocrystalline silicon layer of the intermediate layer directly contacts the p-type conductive semiconductor layer of one of the first and second unit cells, and the n-type hydrogenated amorphous carbon layer of the intermediate layer directly contacts the n-type conductive semiconductor of the other of the first and second unit cell, and

wherein a refractive index in the n-type hydrogenated amorphous carbon layer of the intermediate reflector is profiled such that the farther it is from a light incident side, the larger the refractive index is in the n-type hydrogenated amorphous carbon layer.

13. The photovoltaic device of claim 12 , wherein the intrinsic semiconductor layer of the first unit cell is made of a material having a larger optical band gap for absorbing light of a short wavelength and the intrinsic semiconductor layer of the second unit cell is made of a material having a small optical band gap for absorbing light of a long wavelength.

14. The photovoltaic device of claim 13 , wherein the intrinsic semiconductor layer of the first unit cell is made of hydrogenated amorphous silicon based material and the intrinsic semiconductor layer of the second unit cell is made of silicon germanium or microcrystalline silicon based material.

15. The photovoltaic device of claim 12 , wherein when light is first incident on the first unit cell, the n-type conductive semiconductor layer of the first unit cell is made of an n-type nanocrystalline silicon layer to compensate for low dark conductivity of the n-type hydrogenated amorphous carbon layer of the intermediate layer.

16. The photovoltaic device of claim 15 , wherein the low dark conductivity is equal to or more than 10 −12 S/cm and equal to or less than 10 −6 S/cm.

17. A photovoltaic device comprising:

a substrate defining a light incident side of the photovoltaic device;

a first electrode formed on the substrate;

a first unit cell comprising a first p-type conductive semiconductor layer formed on the first electrode, a first intrinsic semiconductor layer formed on the first p-type semiconductor layer, and a first n-type conductive semiconductor layer formed on the first intrinsic semiconductor layer;

an intermediate reflector comprising an n-type hydrogenated amorphous carbon layer formed directly on the first n-type conductive semiconductor layer of the first unit cell and an n-type nanocrystalline silicon layer formed directly on the n-type hydrogenated amorphous carbon layer, wherein the n-type hydrogenated amorphous carbon layer contains only hydrogen, carbon and n-type impurity;

a second unit cell comprising a second p-type conductive semiconductor layer formed directly on the n-type nanocrystalline silicon layer of the intermediate reflector, a second intrinsic semiconductor layer formed on the second p-type semiconductor layer, and a second n-type conductive semiconductor layer formed on the second intrinsic semiconductor layer; and

a second electrode formed on the second n-type conductive semiconductor layer of the second unit cell;

wherein a refractive index of the n-type hydrogenated amorphous carbon layer of the intermediate reflector is profiled such that the farther it is from the light incident side, the larger the refractive index is in the n-type hydrogenated amorphous carbon layer.

18. The photovoltaic device of claim 17 , wherein the first intrinsic semiconductor layer of the first unit cell is made of hydrogenated amorphous silicon based material and the second intrinsic semiconductor layer of the second unit cell is made of silicon germanium or microcrystalline silicon based material.