KR20150074665A - Transparent Conductive thin film and manufacturing method thereof and solar cell using the same - Google Patents

Abstract

The present invention relate to a transparent conductive film, a method for producing the same, and a solar cell using the same. The transparent conductive film comprises: a first layer formed on a substrate in a first grain size; a second layer formed on the first layer in a second grain size larger than the first grain size; and a third layer formed on the second layer in a third grain size smaller than the second grain size.

Description

TECHNICAL FIELD The present invention relates to a transparent conductive thin film, a method of manufacturing the transparent conductive thin film, and a solar cell using the transparent conductive thin film,

The present invention relates to a transparent conductive thin film and a method of manufacturing the same, and more particularly, to a transparent conductive thin film capable of maintaining haze characteristics and improving surface roughness, and a method of manufacturing the same.

In general, a transparent conductive thin film, for example, a transparent conductive oxide (TCO) thin film has high electrical conductivity and high transparency in a visible light region and is used in many fields as an electrical and optical material. That is, a transparent conductive oxide thin film is used in the fields of solar cell, flat panel display (FPD), and liquid crystal display (LCD).

For example, a thin film solar cell has a structure in which a first electrode layer, a PIN structure semiconductor layer, and a second electrode layer are laminated on a substrate, and a transparent conductive oxide thin film is used for the first and second electrode layers. Here, the semiconductor layer having the PIN structure is composed of a P-type semiconductor layer, an intrinsic semiconductor layer, and an N-type semiconductor layer. An example of such a solar cell is disclosed in Korean Patent No. 10-1332667.

Zinc oxide (ZnO), which has good haze characteristics and good long-wavelength transmittance, is widely used as a transparent conductive thin film used as an electrode of a thin film solar cell. That is, the ZnO thin film formed by the MOCVD method has the advantage of transmitting more sunlight to the intrinsic semiconductor layer by reducing the reflection of the long wavelength and the wavelength by forming texturing in a pyramid shape having a large surface roughness.

However, the pyramid-shaped texturing of the ZnO thin film causes a crack in the p-type semiconductor layer formed thereon, thereby reducing the open-circuit voltage (Voc) and the fill factor. Accordingly, the efficiency of the solar cell is reduced, and the deterioration rate is increased, thereby lowering the stability of the solar cell.

The present invention provides a conductive thin film capable of improving the efficiency and stability of a solar cell and a method of manufacturing the same.

The present invention provides a conductive thin film capable of improving surface roughness and preventing cracks in a thin film formed thereon, a method of manufacturing the same, and a solar cell using the same.

The present invention provides a conductive thin film capable of maintaining a pyramid structure, improving surface roughness, improving the transmittance of a long wavelength and preventing a crack in a thin film formed thereon, a method of manufacturing the same, and a solar cell using the same.

One aspect of the transparent conductive thin film according to the present invention includes: a first layer formed on a substrate and formed of a first grain size; A second layer formed on the first layer and having a second grain size larger than the first grain size; And a third layer formed on the second layer and having a third grain size smaller than the second grain size.

The transparent conductive thin film is ITO (Indium Tin Oxide), ( Fluorine doped Tin Oxide) FTO, ZnO: B, ZnO: Al, SnO 2: F, ZnO: Ga 2 O 3, ZnO: Al 2 O 3, SnO 2: Sb ₂ O ₃ .

The first and third grain sizes are 10 nm to 50 nm, and the second grain size is 200 nm to 300 nm.

The first layer, the second layer, and the third layer adjust the grain size by adjusting the ratio of at least one source gas.

The second layer is formed by adjusting the ratio of at least one source gas to the first layer, and the third layer is formed by adjusting the ratio of at least two source gases to the second layer.

The thickness ratio of the first layer, the second layer and the third layer to the total thickness of the transparent conductive thin film is 5% to 15%, 70% to 90%, and 5% to 15%, respectively.

Another aspect of the transparent conductive thin film according to the present invention comprises a first layer formed on a substrate and formed of a first surface roughness; A second layer formed on the first layer and having a second surface roughness greater than the first surface roughness; And a third layer formed on the second layer and formed of a third surface roughness smaller than the second surface roughness.

The transparent conductive thin film is ITO (Indium Tin Oxide), ( Fluorine doped Tin Oxide) FTO, ZnO: B, ZnO: Al, SnO 2: F, ZnO: Ga 2 O 3, ZnO: Al 2 O 3, SnO 2: Sb ₂ O ₃ .

The first layer, the second layer, and the third layer adjust the surface roughness by controlling the ratio of at least one source gas.

The second layer is formed by adjusting the ratio of at least one source gas to the first layer, and the third layer is formed by adjusting the ratio of at least two source gases to the second layer.

The thickness ratio of the first layer, the second layer and the third layer to the total thickness of the transparent conductive thin film is 5% to 15%, 70% to 90%, and 5% to 15%, respectively.

Another aspect of the transparent conductive thin film according to the present invention is a transparent conductive thin film in which a first layer, a second layer and a third layer are stacked on a substrate using at least two sources, The content of the first source is smaller than that of the second layer, and the content of the second source is smaller and the content of the second source is smaller than that of the third layer.

Wherein the transparent conductive thin film is formed using at least an O source and a B source, the second layer has a smaller content of the B source than the first layer, the third layer has a smaller content of the O source And the content of the B source is large.

One aspect of the method for manufacturing a transparent conductive thin film according to the present invention includes: forming a first layer of a first grain size on a substrate; Forming a second layer of a second grain size larger than the first grain size on the first layer; And forming a third layer of a third grain size smaller than the second grain size on the second layer.

The transparent conductive thin film is ITO (Indium Tin Oxide), ( Fluorine doped Tin Oxide) FTO, ZnO: B, ZnO: Al, SnO 2: F, ZnO: Ga 2 O 3, ZnO: Al 2 O 3, SnO 2: Sb ₂ O ₃ .

The transparent conductive thin film is formed by using at least three or more source gases, and the grain size is adjusted by controlling the ratio of at least one source gas when each layer is formed.

The ratio of at least one source gas is adjusted in forming the second layer and the ratio of at least two source gases is adjusted in forming the third layer in the formation of the second layer.

The first and third grain sizes are 10 nm to 50 nm, and the second grain size is 200 nm to 300 nm.

The thickness ratio of the first layer, the second layer and the third layer with respect to the total thickness is formed to 5% to 15%, 70% to 90%, and 5% to 15%, respectively.

The ratio of the formation time of the first layer, the second layer and the third layer with respect to the formation time of the entire thickness is set to 5% to 10%, 75% to 85%, and 10% to 15%, respectively.

Another aspect of the method for manufacturing a transparent conductive thin film according to the present invention is to form a ZnO: B thin film in which a first layer, a second layer and a third layer are stacked using a Zn source, an O source and a B source, Layer is formed by reducing the ratio of the B-source to the B-source, and the third layer is formed by reducing the ratio of the O-source to the B-source and increasing the ratio of the B-source to the B-source.

One aspect of a solar cell according to the present invention includes: a first electrode layer formed on a substrate; A semiconductor layer formed on the first electrode layer; And a second electrode layer formed on the semiconductor layer, wherein the first electrode layer includes a first layer formed of a first grain size, a second layer formed on the first layer and having a second grain size larger than the first grain size, And a third layer formed on the second layer and formed of a third grain size smaller than the second grain size.

The first and third grain sizes are 10 nm to 50 nm, and the second grain size is 200 nm to 300 nm.

The first electrode layer is formed by using at least three or more source gases, and the ratio of at least one source gas is adjusted when each layer is formed to have different grain sizes.

The second layer is formed by controlling the ratio of at least one source gas to the first layer, and the third layer is formed by controlling the ratio of at least two source gases to the second layer.

The transparent conductive thin film according to the embodiments of the present invention includes a first layer of a first grain size, a second layer of a second grain size larger than the first grain size, and a second layer of a third grain size smaller than the second grain size, Three layers are laminated. In addition, the transparent conductive thin film may be formed of a plurality of layers having different grain sizes by controlling a supply rate or a supply amount of at least one source gas.

Therefore, the surface resistance of the transparent conductive thin film can be improved by the gently formed first layer, and the second layer is formed in a pyramid shape, so that the reflection of the long wavelength to the wavelength can be reduced. The roughness can be improved and cracks in the thin film formed thereon can be prevented.

In addition, when such a transparent conductive thin film is applied to a solar cell, the open-circuit voltage (Voc) and the fill factor of the solar cell can be increased as compared with the prior art, thereby improving the efficiency of the solar cell and decreasing the deterioration rate The stability of the solar cell can be improved.

1 is a cross-sectional view of a transparent conductive thin film according to an embodiment of the present invention.
2 is a cross-sectional view illustrating a method of manufacturing a transparent conductive thin film according to an embodiment of the present invention.
3 to 5 are photographs of a surface of a transparent conductive thin film fabricating step according to an embodiment of the present invention.
6 is a sectional view of a solar cell using a transparent conductive thin film according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of other various forms of implementation, and that these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know completely.

1 is a cross-sectional view of a transparent conductive thin film according to an embodiment of the present invention.

1, a transparent conductive thin film according to an exemplary embodiment of the present invention includes a first layer 210 formed on a substrate 100, a second layer 210 formed on a first layer 210, a second layer 220 formed on the second layer 220, and a third layer 230 formed on the second layer 220. Here, the transparent conductive thin film of the present invention may include a transparent conductive oxide (TCO) formed by using at least two or more source gases. For example, ITO (Indium Tin Oxide), (Fluorine doped Tin Oxide) FTO, ZnO: B, ZnO: Al, SnO 2: F, ZnO: Ga 2 O 3, ZnO: Al 2 O 3, SnO 2: Sb ₂ O ₃ , and the embodiments of the present invention will be described by taking ZnO: B doped with B impurity into ZnO as an example.

The first layer 210 is formed on the substrate 100 and may be formed to a thickness of 5% to 15% of the total thickness of the transparent conductive thin film. For example, when the total thickness of the transparent conductive thin film layered with the first layer 210, the second layer 220, and the third layer 230 is 900 nm to 1100 nm, the first layer 210 ) May be formed to a thickness of 70 nm to 100 nm. The first layer 210 may be formed by adjusting the supply amount of at least two sources. For example, when a ZnO: B thin film is formed using a Zn source, an O source, and a B source, the Zn source, the O source, and the B source are supplied at a ratio of 1: 1 to 1.2: 0.4 to 0.6, ) Can be formed. That is, the Zn source and the B source are supplied at a ratio of 1: 0.4 to 0.6, and the Zn source and the O source are supplied at a ratio of 1: 1 to 1.2. In addition, the first layer 210 can be formed at a time of about 5% to 10% of the total formation time of the transparent conductive thin film. For example, if the total formation time of the transparent conductive thin film is 300 seconds, the first layer 210 can be formed for 30 seconds. In order to form the first layer 210 in a thickness of 5% to 15% of the total thickness of the transparent conductive thin film and for 10% of the total growth time of the transparent conductive thin film, for example, Zn source, O source and B source 2000 sccm to 5000 sccm, 2000 sccm to 6000 sccm, and 1500 sccm to 2000 sccm for 30 seconds. Here, the Zn source may include diethyl zinc (Zn (C ₂ H ₅ ) ₂ Diethyl Zinc; DEZ), the oxygen source may include H ₂ O, and the B source may include B ₂ H ₆ can do. The first layer 210 thus formed is formed with a grain size of, for example, 50 nm or less, preferably 10 nm to 50 nm, and the surface shape is gently formed, thereby improving the surface resistance of the transparent conductive thin film. Also, as the formation time of the first layer 210 increases, the surface resistance of the transparent conductive thin film can be further reduced.

The second layer 220 may be formed on the first layer 210 and may have a grain size larger than that of the first layer 210 to be thicker than the first layer 210. That is, the second layer 220 may have a surface roughness larger than that of the first layer 210. For example, when the transparent conductive thin film is formed with a thickness of 900 nm to 1100 nm, the second layer 220 may be formed to a thickness of 70% to 90% of the total thickness of the transparent conductive thin film. ) May be formed to a thickness of 700 nm to 800 nm. The second layer 220 may be formed by adjusting a supply ratio of at least one source gas to that of the first layer 210. For example, by supplying the Zn source, the O source, and the B source at a ratio of 1: 1 to 1.2: 0.2 to 0.3. That is, the second layer 220 can be formed by reducing the ratio of the source B to the thickness of the first layer 210. In addition, the second layer 210 can be formed at a time of about 75% to 85% of the total formation time of the transparent conductive thin film. For example, if the total formation time of the transparent conductive thin film is 300 seconds, the second layer 210 can be formed for 220 seconds. In order to form the second layer 220 in a thickness of 70% to 90% of the total thickness of the transparent conductive thin film and for 75% of the total growth time of the transparent conductive thin film, for example, the Zn source, O source and B source 2500 sccm to 4500 sccm, 2500 sccm to 5500 sccm and 800 sccm to 900 sccm for 220 seconds. The second layer 220 may be formed to have a grain size larger than that of the first layer 210, for example, a grain size of 200 nm to 300 nm. Accordingly, the second layer 220 is textured in a pyramid shape, thereby reducing reflection of a long wavelength and a wavelength, thereby transferring more sunlight to the semiconductor layer of the solar cell.

The third layer 230 may be formed on the second layer 220 and may be formed to be thinner than the second layer 220 with a smaller grain size than the second layer 220. In other words, the third layer 230 may be formed with less surface roughness than the second layer 220. For example, the third layer 230 may be formed to have a thickness of 5% to 15% of the total thickness of the transparent conductive thin film. When the transparent conductive thin film is formed with a thickness of 900 nm to 1100 nm, ) May be formed to a thickness of 70 nm to 100 nm. The third layer 230 may be formed by adjusting the supply ratio of at least one source gas to the second layer 220. For example, the third layer 230 can be formed by supplying the Zn source, the O source, and the B source at a ratio of 1: 0.6-0.8: 0.5-0.7. That is, the third layer 230 can be formed by reducing the ratio between the source B and the source O, compared to the case of forming the second layer 220. In addition, the third layer 230 can be formed with a time of about 15% of the total formation time of the transparent conductive thin film. For example, if the total formation time of the transparent conductive thin film is 300 seconds, the third layer 230 can be formed for 50 seconds. In order to form the third layer 230 in a thickness of 5% to 15% of the total thickness of the transparent conductive thin film and for 10% to 15% of the total growth time of the transparent conductive thin film, for example, Zn source, O source and B The source may be supplied for 50 seconds each in an amount of 3500 sccm to 6000 sccm, 2000 sccm to 4800 sccm, and 2500 sccm to 3000 sccm, respectively. The third layer 230 may be formed to have a grain size smaller than that of the second layer 220. For example, the third layer 230 may have a grain size of 50 nm or less, preferably 10 nm to 50 nm. At this time, the grain size of the third layer 230 may be equal to or different from the grain size of the first layer 210. Therefore, the third layer 230 having a small grain size is formed on the second layer 220 having a large grain size, so that the surface roughness of the transparent conductive thin film can be reduced compared to the second layer 220, The semiconductor layer of the solar cell to be formed, for example, can be prevented from cracking.

As described above, the transparent conductive thin film according to an embodiment of the present invention includes a first layer 210 of a first grain size formed on a substrate 100, a second layer 210 of a first grain size on the first layer 210, A second layer 220 is formed with a large second grain size and a third layer 230 having a third grain size smaller than the second grain size is formed on the second layer 220. Accordingly, the surface resistance of the transparent conductive thin film can be improved by the gently formed first layer 210 and the reflection of the long wavelength and the wavelength can be reduced by forming the second layer 220 in a pyramid shape, (230) can improve the surface roughness of the second layer (220), thereby preventing a crack in the thin film formed on the second layer (220).

2 (a) to 2 (c) are sequentially sectional views illustrating a method of forming a transparent conductive thin film according to an embodiment of the present invention. 3 to 5 are plan views of the transparent conductive thin film according to an embodiment of the present invention.

Referring to FIG. 2 (a), the substrate 100 is loaded into a reaction chamber having a predetermined reaction space. The substrate 100 is seated and supported on the susceptor inside the reaction chamber. Then, the inside of the reaction chamber is adjusted to a predetermined temperature and pressure by using the temperature control device and the pressure control device, respectively. At this time, the temperature control device may be provided inside or outside the reaction chamber, for example, a heater provided inside the susceptor. Further, the pressure regulating device may be an exhaust device connected to an exhaust port provided in at least one region of the reaction chamber. Such a reaction chamber can maintain a temperature of, for example, 190 DEG C to 200 DEG C and a pressure of 0.5 Torr. Then, the process gas is supplied into the reaction chamber. The process gas is supplied through the process gas supply unit outside the reaction chamber and is injected into the reaction chamber 100 through the gas injection unit disposed opposite to the susceptor. Here, the process gas includes at least two source gases, for example, a Zn source, an O source, and a B source as an impurity in order to form a ZnO: B thin film. The Zn source may include diethyl zinc (Zn (C ₂ H ₅ ) ₂ Diethyl Zinc (DEZ), the oxygen source may include H ₂ O, and the B source may include B ₂ H ₆ have. At this time, plasma of the process gas can be generated in the reaction chamber. To this end, a predetermined power source may be applied to the electrode provided in the reaction chamber, an antenna may be provided outside the reaction chamber, and a predetermined power may be applied to the antenna. The first layer 210 is formed on the substrate 100 by supplying at least two or more source gases. The first layer 210 may be formed by supplying a Zn source, an O source, and a B source at a ratio of 1: 1 to 1.2: 0.4 to 0.6. In addition, the first layer 210 can be formed to a thickness of 5% to 15% of the total thickness of the transparent conductive thin film, and can be formed with a time of about 10% of the total formation time of the transparent conductive thin film. For example, when the total thickness of the transparent conductive thin film is formed to a thickness of 900 nm to 1100 nm, the first layer 210 can be formed to a thickness of 70 nm to 100 nm, and the total formation time of the transparent conductive thin film is 300 seconds, the first layer 210 may be formed for 30 seconds. For example, the first layer 210 may be formed by supplying the Zn source, the O source, and the B source in an amount of 2000 sccm to 5000 sccm, 2000 sccm to 6000 sccm, and 1500 sccm to 2000 sccm, respectively, for 30 seconds. The first layer 210 thus formed may be formed with a grain size of 50 nm or less, for example, and the surface shape may be gently formed as shown in FIG. In addition, since the first layer 210 is formed in a gentle surface shape, the surface resistance of the transparent conductive thin film can be improved, and the surface resistance of the transparent conductive thin film is further improved as the formation time of the first layer 210 is increased .

Referring to FIG. 2B, a second layer 220 is formed on the first layer 210 by changing at least one supply amount of the source gas. That is, the second layer 220 is formed by changing the supply amount of at least the B-source gas in comparison with the formation of the first layer 210. For example, the second layer 220 may be formed by supplying a Zn source, an O source, and a B source at a ratio of 1: 1 to 1.2: 0.2 to 0.3. Further, the second layer 220 can be formed to a thickness of 70% to 90% of the total thickness of the transparent conductive thin film, and can be formed at a time of about 75% of the total time of forming the transparent conductive thin film. For example, when the transparent conductive thin film is formed to a thickness of 900 nm to 1100 nm, the second layer 220 can be formed to a thickness of 700 nm to 800 nm, and when the total formation time of the transparent conductive thin film is 300 seconds The second layer 210 may be formed for 220 seconds. For this purpose, for example, the Zn source, the O source and the B source can be supplied for 220 seconds in an amount of 2500 sccm to 4500 sccm, 2500 sccm to 5500 sccm and 800 sccm to 900 sccm, respectively. The second layer 220 thus formed is formed with a grain size of 200 nm to 300 nm, for example, and texturing is formed in a pyramid shape as shown in FIG. The second layer 220 is formed in a pyramid shape to reduce reflection of a long wavelength and a wavelength.

Referring to FIG. 2 (c), a third layer 230 is formed on the second layer 220 by varying at least one supply amount of the source gas. That is, the third layer 230 is formed by varying the supply amount of at least the B-source gas in comparison with the formation of the second layer 220. For example, the third layer 230 may be formed by supplying a Zn source, an O source, and a B source at a ratio of 1: 0.6 to 0.8: 0.5 to 0.7. In addition, the third layer 230 can be formed to a thickness of 5% to 15% of the total thickness of the transparent conductive thin film, and can be formed with a time of about 15% of the total formation time of the transparent conductive thin film. For example, when the transparent conductive thin film is formed to a thickness of 900 nm to 1100 nm, the third layer 230 may be formed to a thickness of 70 nm to 100 nm, and when the total formation time of the transparent conductive thin film is 300 seconds The third layer 230 may be formed for 50 seconds. For this purpose, for example, the Zn source, O source and B source can be supplied for 50 seconds in amounts of 3500 sccm to 6000 sccm, 2000 sccm to 4800 sccm and 2500 sccm to 3000 sccm, respectively. The third layer 230 may be formed to have a grain size smaller than that of the second layer 220, for example, a grain size of 50 nm or less. Therefore, as shown in FIG. 5, the surface roughness of the transparent conductive thin film can be reduced.

[Table 1] compares the optical characteristics and the resistance characteristics according to the comparative example and the embodiments of the present invention. In the comparative example, B ₂ H ₆ was supplied as the source B in an amount of 1500 sccm for 305 seconds to form a ZnO: B thin film. In the embodiments of the present invention, the B source is supplied for the same time as the comparative example, ZnO: B thin films were formed in three steps. That is, in the first embodiment, H ₂ H ₆ is supplied in an amount of 2000 sccm for 40 seconds to form a first layer, and then in an amount of 700 sccm for 235 seconds to form a second layer, and then in an amount of 3000 sccm for 30 seconds To form a third layer. In the second embodiment, H ₂ H ₆ is supplied in an amount of 2000 sccm for 50 seconds to form a first layer, and then in an amount of 700 sccm for 225 seconds to form a second layer, which is then spun for 30 seconds in an amount of 3000 sccm To form a third layer. Then, in the third embodiment, H ₂ H ₆ is supplied in an amount of 2000 sccm for 60 seconds to form a first layer, and then in an amount of 700 sccm for 215 seconds to form a second layer, and in an amount of 3000 sccm for 30 seconds To form a third layer. On the other hand, the optical characteristics were compared with the transmittance and haze of the whole wavelength and the transmittance and haze of the wavelength of 600 nm.

Optical characteristic
Deposition thickness
(Nm)
Sheet resistance
(Ω / □)
resistance
(Ω / m) Transmittance (%) Haze (%) 600 nm
Transmittance (%) 600 nm
Haze (%) Comparative Example 78.0 20.4 79.6 12.59 1171 14.63 1.71E-03 Example 1 79.4 18.0 81.4 10.68 1097 14.49 1.59E-03 Example 2 78.7 20.3 80.9 12.22 1162 13.78 1.60E-03 Example 3 79.2 17.3 81.0 10.69 1124 13.12 1.47E-03

As shown in Table 1, the transparent conductive thin film according to the embodiments of the present invention has improved optical characteristics and resistance characteristics as compared with the transparent conductive thin film of the comparative example. That is, the transmittance of the whole wavelength is superior to the comparative example in the embodiments of the present invention, and the transmittance of the wavelength of 600 nm is also superior to the comparative example in the embodiments of the present invention. It can also be seen that the haze at the whole wavelength and the haze at the wavelength of 600 nm are similar to the embodiments of the present invention and the comparative example. Since the embodiments of the present invention can improve the transmittance as compared with the comparative example, when the solar cell is applied to the solar cell, the efficiency of the solar cell can be improved by about 1% to 2% as compared with the comparative example. Also, the deposition thickness according to the same deposition time is similar to the embodiments of the present invention and the comparative example. It is also understood that the sheet resistance and resistance are also lower in the embodiments of the present invention than in the comparative example. It can be seen that the third embodiment of the present invention has lower sheet resistance and resistance than the first and second embodiments. That is, as the supply time of the B-source for forming the first layer increases, the sheet resistance and resistance of the transparent conductive thin film become low.

The transparent conductive thin film according to one embodiment of the present invention can be used for a solar cell, a flat panel display, a liquid crystal display, and the like.

6 is a cross-sectional view of a solar cell using a transparent conductive thin film according to embodiments of the present invention.

Referring to FIG. 6, a solar cell according to an embodiment of the present invention includes a substrate 100, a first electrode layer 200 formed on the substrate 100, a semiconductor layer 200 formed on the first electrode layer 200, (300), and a second electrode layer (400) formed on the semiconductor layer (300).

The substrate 100 may be a glass substrate or a flexible plastic substrate. When the substrate 100 is a glass substrate, the solar cell mainly absorbs sunlight through the glass substrate. When the substrate 100 is a flexible plastic film, the solar cell is divided into a second electrode layer 400 to absorb sunlight. In the case of the glass substrate, the light transmittance is high and the solar light can be absorbed from the substrate 100 side. However, since the flexible plastic substrate is a translucent material or an opaque material, the light transmittance is low, It can not absorb. Of course, even in the case of the flexible plastic substrate, solar light can be partially absorbed from the substrate 100 side.

The first electrode layer 200 is formed on the upper surface of the substrate 100 and may be formed of a transparent conductive thin film according to embodiments of the present invention. That is, the first electrode layer 200 includes a first layer 210 having a first grain size, a second layer 220 having a second grain size larger than the first grain size and formed on the first layer 210, And a third layer 230 formed on the second layer 220 and having a third grain size smaller than the second grain size. The first electrode layer 200 may include a transparent conductive oxide formed using at least two types of source gases. For example, ITO (Indium Tin Oxide), FTO (Fluorine Doped Tin Oxide), ZnO: B, ZnO _{: Al, SnO 2: F,} ZnO: Ga 2 O 3, ZnO: Al 2 O 3, SnO 2: and the like Sb ₂ O _3. Since the first electrode layer 200 is formed by texturing the second layer 220 in a pyramid shape, incident solar light can be absorbed into the solar cell as much as possible. In other words, since the second layer 220 of the first electrode layer 200 is formed in a pyramid structure, the incident solar light can be reduced to the outside of the solar cell, and the incident solar light can scatter It is possible to increase the rate of absorption of solar light into the solar cell, thereby improving the efficiency of the solar cell.

The semiconductor layer 300 may include a first semiconductor layer 310, an intrinsic semiconductor layer 320, and a second semiconductor layer 330. Here, the first semiconductor layer 310 and the second semiconductor layer 330 may be semiconductor layers doped with impurities of different conductivity types, respectively, and the intrinsic semiconductor layer 320 may be a semiconductor layer that is not doped with impurities. For example, when a glass substrate is used as the substrate 100, the first semiconductor layer 310 is a p-type semiconductor layer doped with a p-type impurity, and the second semiconductor layer 330 is an n-type Semiconductor layer. That is, since the drift mobility of holes is lower than the mobility of electrons, when a glass substrate is used as the substrate 100 in order to maximize collection efficiency by incident light, a P-type semiconductor material is formed close to the light-incident surface . In addition, the semiconductor layer 300 may be a crystalline silicon (c-Si) -based material or an amorphous silicon (a-Si) -based material. The amorphous silicon (a-Si) based material may include, for example, amorphous silicon (a-Si) or amorphous silicon germanium (a- SiGe) (Microcrystalline silicone; μc-Si: H) or nanocrystalline silicone (nc-Si: H). On the other hand, since the semiconductor layer 300 is formed on the first electrode layer 200 having improved surface roughness according to the embodiments of the present invention, cracks are not generated. That is, a semiconductor layer 300 is formed on a pyramid-shaped electrode having a large surface roughness to cause a crack in the semiconductor layer 300, but a third layer 230 is formed on the second layer 220 Since the semiconductor layer 300 is formed on the first electrode layer 200 according to the present invention having a small surface roughness, cracks are not generated in the semiconductor layer 300.

The second electrode layer 400 is formed on the second semiconductor layer 330. The second electrode layer 400 may be formed of a transparent conductive oxide so that the solar light absorbed as the light-entering surface can reach the second semiconductor layer 330, the intrinsic semiconductor layer 320, and the first semiconductor layer 310 . Since the second electrode layer 400 is a surface on which sunlight is incident, it is important that the incident solar light can be absorbed into the solar cell as much as possible. To this end, the second electrode layer 400 is textured with a pyramid structure . The second electrode layer 400 may include a first layer 210 of a first grain size, a second layer of a second grain size larger than the first grain size formed on the first layer 210, And a third layer 230 having a third grain size smaller than the second grain size formed on the second layer 220. The second layer 220 may be formed on the second layer 220, Of course, since no additional thin film is formed on the second electrode layer 400, the second electrode layer 400 may be formed of only the second layer 220.

Although the technical idea of the present invention has been specifically described according to the above embodiments, it should be noted that the above embodiments are for explanation purposes only and not for the purpose of limitation. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention.

100: substrate 210: first layer
220: second layer 230: third layer
200: first electrode layer 300: semiconductor layer
310: first semiconductor layer 320: intrinsic semiconductor layer
330: second semiconductor layer 400: second electrode layer

Claims (22)

A first layer formed on the substrate and formed of a first grain size;
A second layer formed on the first layer and having a second grain size larger than the first grain size; And
And a third layer formed on the second layer and having a third grain size smaller than the second grain size.
The transparent conductive thin film according to claim 1, wherein the first and third grain sizes are 10 nm to 50 nm and the second grain size is 200 nm to 300 nm.
The transparent conductive thin film according to claim 2, wherein the first layer, the second layer, and the third layer adjust the grain size by adjusting a ratio of at least one source gas.
[4] The method of claim 3, wherein the second layer is formed by adjusting a ratio of at least one source gas to the first layer, and the third layer is formed by adjusting a ratio of at least two source gases Transparent conductive thin film.
The transparent conductive film of claim 1, wherein the thickness ratio of the first layer, the second layer and the third layer to the total thickness is 5% to 15%, 70% to 90%, and 5% to 15%, respectively.
A first layer formed on the substrate and formed with a first surface roughness;
A second layer formed on the first layer and having a second surface roughness greater than the first surface roughness; And
And a third layer formed on the second layer and formed with a third surface roughness smaller than the second surface roughness.
The transparent conductive thin film according to claim 6, wherein the first layer, the second layer, and the third layer adjust the surface roughness by adjusting a ratio of at least one source gas.
[7] The method of claim 7, wherein the second layer is formed by adjusting a ratio of at least one source gas to the first layer, and the third layer is formed by adjusting a ratio of at least two source gases Transparent conductive thin film.
7. The transparent conductive thin film according to claim 6, wherein the thickness ratio of the first layer, the second layer and the third layer to the total thickness is 5% to 15%, 70% to 90%, and 5% to 15%, respectively.
A transparent conductive thin film formed by laminating a first layer, a second layer and a third layer on a substrate using at least two sources,
Wherein the second layer has a smaller content of the first source than the first layer and the third layer has a larger content of the first source and a smaller content of the second source than the second layer.
The method according to claim 10, wherein at least an O source and a B source are used, the second layer has a smaller content of the B source than the first layer, the third layer has a smaller content of the O source And the content of the B-source is large.
Forming a first layer of a first grain size on a substrate;
Forming a second layer of a second grain size larger than the first grain size on the first layer; And
And forming a third layer of a third grain size smaller than the second grain size on the second layer.
The method according to claim 12, wherein at least three or more source gases are used, and the grain size is adjusted by adjusting the ratio of at least one source gas when each layer is formed.
14. The method according to claim 13, wherein the ratio of the at least one source gas is adjusted when the second layer is formed and the ratio of at least two source gases is set to be greater than that when the third layer is formed, Wherein the transparent conductive thin film has a thickness of 10 to 100 nm.
15. The method of manufacturing a transparent conductive thin film according to claim 14, wherein the first and third grain sizes are 10 nm to 50 nm and the second grain size is 200 nm to 300 nm.
The transparent conductive thin film according to claim 12, wherein the thickness ratio of the first layer, the second layer and the third layer to the total thickness is 5% to 15%, 70% to 90%, and 5% to 15% Gt;
The method according to claim 12, wherein the ratio of the formation time of the first layer, the second layer and the third layer to the formation time of the total thickness is formed to 5% to 10%, 75% to 85%, and 10% to 15% Of the transparent conductive thin film.
A ZnO: B thin film in which a first layer, a second layer and a third layer are stacked is formed using Zn source, O source and B source,
The second layer is formed by reducing the ratio of the B-source to the B-layer, and the third layer is formed by reducing the ratio of the O-source to the B- Of the transparent conductive thin film.
A first electrode layer formed on a substrate;
A semiconductor layer formed on the first electrode layer; And
And a second electrode layer formed on the semiconductor layer,
The first electrode layer may include a first layer formed on a first grain size, a second layer formed on the first layer and having a second grain size larger than the first grain size, and a second layer formed on the second layer And a third layer formed to have a third grain size smaller than the second grain size.
The solar cell according to claim 19, wherein the first and third grain sizes are 10 nm to 50 nm and the second grain size is 200 nm to 300 nm.
The solar cell according to claim 19 or 20, wherein the first electrode layer is formed using at least three or more source gases, and the ratio of at least one source gas is adjusted to form a different grain size when each layer is formed.
The method of claim 21, wherein the second layer is formed by controlling the ratio of at least one source gas to the first layer, and the third layer is formed by adjusting the ratio of at least two source gases to the second layer battery.

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