KR20110027903A - Solar cell and method of fabricating the same - Google Patents

Abstract

PURPOSE: A solar cell and a method for manufacturing the same are provided to expand an incident light route in a solar light absorbing layer, thereby increasing a light absorbing rate over the entire area of an ultraviolet ray, a visible ray, and an infrared ray. CONSTITUTION: A transparent electrode(600) is arranged on a substrate(100). An active layer(700) is arranged on the transparent electrode. A facing electrode(800) is arranged on the active layer. The transparent electrode comprises a buffer layer(200), the first bar(300), the second bar(400), and a coating layer(500). The buffer layer, the first bar, and the second bar are formed of the same material.

Description

SOLAR CELL AND METHOD OF FABRICATING THE SAME

An embodiment relates to a solar cell and a manufacturing method thereof.

Recently, as the demand for energy increases, development of solar cells for converting solar energy into electrical energy is in progress. Such solar cells include CIGS solar cells, silicon solar cells, dye-sensitized solar cells, and semiconductor solar cells.

In general, a solar cell has a pair of electrons and holes generated inside the semiconductor of the solar cell by light from outside, and electrons move to an n-type semiconductor by an electric field generated at a pn junction in the pair of electrons and holes. Moving to p-type semiconductors produces power.

In the case of a transparent electrode applied to a solar cell, the efficiency of converting sunlight into electricity is the most important, and in view of the characteristics of the application, it is essential for the conductive material to have a low specific resistance with high light transmittance.

In the related art, thin film crystalline silicon solar cells have been studied with thin films such as textured ITO and ZnO: Al in order to increase light absorption. Existing front transparent conductive films, such as textured ZnO: Al, require very sophisticated and complex processes, such as deposition and doping through sputtering and texturing through chemical etching, which can be expensive and time consuming. In addition, cost increases due to the high equipment investment costs associated with the application of vacuum technology.

In addition, due to the low light absorption rate of the light absorption layer, artificial design of the front transparent conductive film and the rear reflective electrode is required. In addition, doping is necessary because of the low conductivity of the electrode's main material, transparent conducting oxid (TCO), as well as artificial electrode designs such as texturing. Currently, the thinning process through the vacuum technology has a limit in reducing the investment cost according to the vacuum equipment requirements.

Therefore, studies are being conducted to increase light absorption and photoelectric conversion efficiency using materials with improved conductivity.

Embodiments provide a solar cell having an improved light absorption rate and photoelectric conversion efficiency and a method of manufacturing the same.

In one embodiment, the solar cell comprises a substrate, a transparent electrode disposed on the substrate, an active layer disposed on the transparent electrode and a counter electrode disposed on the active layer, the transparent electrode on the buffer layer, the buffer layer A first rod disposed and a second rod disposed on the first rod.

In another embodiment, a method of manufacturing a solar cell is provided, wherein the method of manufacturing a solar cell includes forming a transparent electrode on a substrate, forming an active layer on the transparent electrode, and forming an opposite electrode on the active layer. And forming the transparent electrode, forming a buffer layer on the substrate, forming a first rod on the buffer layer, and forming a second rod on the first rod. Steps.

The solar cell according to an embodiment includes a transparent electrode having a stacked structure of rods. The transparent electrode is composed of a first bar and a second bar. The first rods change the refractive characteristics of the incident light, thereby allowing the light path to be controlled, thereby extending the incident light path in the solar absorption layer. Therefore, the light absorption rate over the entire area of ultraviolet ray, visible ray and infrared ray is increased. The contact area between the active layer and the active layer is improved by the second rod, thereby increasing the photoelectric conversion efficiency due to the decrease in contact resistance between the electrode and the active layer.

In the description of the embodiments, where each substrate, film, electrode, or layer is described as being formed "on" or "under" of each substrate, electrode, film, or layer, "On" and "under" include both being formed "directly" or "indirectly" through other components. In addition, the criteria for the top or bottom of each component will be described with reference to the drawings. The size of each component in the drawings may be exaggerated for the sake of explanation and does not mean the size actually applied.

1 is a cross-sectional view of a solar cell according to an embodiment.

Referring to FIG. 1, a solar cell according to an embodiment includes a substrate 100, a transparent electrode 600, an active layer 700, and a counter electrode 800, and the transparent electrode 600 includes a buffer layer 200. And a first rod 300, a second rod 400, and a coating layer 500.

The substrate 100 is transparent and insulator. The substrate 100 may be, for example, a glass substrate, a quartz substrate, or a plastic substrate.

The buffer layer 200 may have a continuous thin film form in order to efficiently send holes obtained from absorbed light to the storage battery. In addition, since the buffer layer 200 acts as a lattice (lattice) for the first rod 300, and it is energetically stable that crystals grow vertically, the buffer layer 200 grows crystals vertically. Let's do it.

In one embodiment, examples of the material forming the buffer layer 200 may be zinc oxide (ZnO), tin oxide (SnO), or indium tin oxide (ITO). In addition, the zinc oxide may be doped with gallium (Ga), aluminum (Al) or boron (B), and the tin oxide may be doped with fluorine (F).

The first rod 300 may be formed of a plurality of (310, 320, 330 ...) at regular intervals. The first rod 300 is formed in a rod shape in a direction perpendicular to the buffer layer 200. The first rod 300 may have a pillar shape, a polygonal pillar shape, and among them, a hexagonal pillar shape.

The diameter of the first rod 300 is 1 μm to 20 μm. In addition, the height of the first rod 300 is 0.01 μm to 10 μm. The diameter and height of the first rod 300 may vary depending on the temperature, concentration, pressure, and external energy (eg, ultrasonic wave, microwave, etc.) for growing the first rod 300.

The first rod 300 absorbs incident light and scatters light. Light incident on the first bar 300 is changed in refractive index by the refractive index, the optical band gap, the diameter, and the length of the first bar 300. The first rod 300 refracts incident light to control the light path, thereby increasing the light density incident on the absorbing layer. Therefore, since the light path can be controlled using the characteristics of the first bar 300, the incident light path can be extended in the solar absorption layer.

In one embodiment, the material forming the first rod 300 is zinc oxide. In addition, the zinc oxide is zinc oxide doped with gallium, aluminum or boron.

The second rod 400 may be formed in plurality 410, 420, 430... At regular intervals on the first rod 300. The second rod 300 is formed in the same direction as the first rod 300 and is formed in the vertical direction with respect to the buffer layer 200. The shape of the second rod 400 may be a pillar shape, a polygonal pillar shape, and among them, a hexagonal pillar shape.

The diameter of the second rod 400 is 10 nm to 500 nm. In addition, the height of the second rod 400 is 10 nm to 10,000 nm. That is, the diameter of the second rod 400 is smaller than the diameter of the first rod 300. The diameter of the second rod 400 may vary depending on the temperature, concentration, pressure, and external energy (eg, ultrasonic wave, microwave, etc.) for growing the second rod 300.

The second rod 400 extends upwardly (upward) with respect to the first rod 300. That is, it is formed to increase the contact area with the active layer 700. In general, resistance is related to the resistivity and area of a material, which is proportional to the resistivity and inversely related to the area. Therefore, when the area is increased, the resistance is generally reduced. Therefore, since the second rod 400 is formed to increase the contact area with the active layer 700, the second rod 400 reduces the contact resistance between the transparent electrode 600 and the active layer 700 to increase the photoelectric conversion efficiency.

In one embodiment, the material forming the second rod 400 is zinc oxide. In addition, the zinc oxide is zinc oxide doped with gallium, aluminum or boron.

In one embodiment, the solar cell further includes a coating layer 500 formed by coating a conductive material on the buffer layer 200, the first rod 300, and the second rod 400. The coating layer 500 is for improving the conductivity of the transparent electrode.

In one embodiment, the conductive material may be a poly (3,4-ethylenedioxythiophene) (PEDOT) -based conductive polymer. In particular, including the coating layer coated with the PEDOT-based conductive polymer is effective in the polymer solar cell.

As described above, in one embodiment, the buffer layer 200, the first rod 300 and the second rod 400 may be made of the same material. The same material may be zinc oxide. In addition, the zinc oxide may be zinc oxide doped with gallium, aluminum or boron. Therefore, when the buffer layer 200, the first rod 300, and the second rod 400 are made of the same material, light absorption of the ultraviolet, visible, and infrared rays may be increased. have.

Sunlight is incident on the solar cell according to the embodiment through the substrate 100. The incident sunlight is absorbed into the active layer 700 via the transparent electrode 600. The active layer 700 generates electrons and holes using incident light. The generated electrons are moved to the counter electrode 800, and holes are moved to the transparent electrode 600.

The solar cell according to the embodiment generates a potential difference, that is, electrical energy in the above manner.

Therefore, the solar cell according to the embodiment has a transparent electrode 600, the transparent electrode 600 has a structure in which the rod including the first rod 300 and the second rod 400 is stacked The solar cell according to the embodiment efficiently injects sunlight into the active layer 700 from the transparent electrode 600. In addition, the contact resistance between the transparent electrode 600 and the active layer 700 is reduced to increase the photoelectric conversion efficiency. In addition, the reflection of sunlight at the interface between the transparent electrode 600 and the active layer 700 is reduced.

Thus, the solar cell according to the embodiment has improved power generation efficiency.

2 is a cross-sectional view and a perspective view of a rod-shaped forming a transparent electrode of the solar cell according to the embodiment.

As shown in FIG. 2, the rods forming the transparent electrodes of the solar cell may be formed in plural at regular intervals. For example, a zinc oxide (ZnO) thin film is generally grown while maintaining the vertical axis preferential orientation because the most energy-stable surface is vertical. In addition, the crystal structure of zinc oxide is a hexagonal wurzite structure in which O ions are located at hexagonal sites and Zn ions are located at positions between tetrahedral crystal lattice. A surface composed only of Zn atoms is relatively positively charged, and a surface composed only of O atoms is relatively negatively charged. Therefore, if the material forming the rod is zinc oxide, the shape of the rod may be a hexagonal pillar.

3 illustrates a first bar and a second bar forming a transparent electrode of the solar cell according to the embodiment.

As shown in FIG. 3, the second rod is formed in the same direction on the first rod. That is, the second rod is formed on the first rod in a stacked structure. The first rod and the second rod may be formed in plural. In addition, as described above, if the material forming the rod is zinc oxide, the shape of the rod may be a hexagonal pillar.

Hereinafter, a method of manufacturing a solar cell according to an embodiment will be described.

4 to 8 are views illustrating a method of manufacturing a solar cell according to the embodiment.

Referring to FIG. 4, a buffer layer 200 is formed on a substrate 100. The buffer layer 200 may be formed by a physical vapor deposition (PVD) process including a chemical vapor deposition (CVD) process or a sputtering process. The buffer layer 200 may be formed in addition to other processes for depositing a thin film.

The buffer layer 200 may be formed at about 50 ℃ to 400 ℃. More specifically, the buffer layer 200 may be formed at about 150 ℃ to 250 ℃.

The refractive index of the buffer layer 200 may be about 1.4 to 3.0.

The buffer layer 200 may have a thickness of about 5,000 kPa to 10,000 kPa.

Referring to FIG. 5, a first rod 300 is formed on the buffer layer 200. In order to form the first rod 300, a solution including a material (eg, zinc nitrate) for forming the first rod 300 is prepared. The concentration of the solution may be 0.001 M to 0.9 M. The substrate 100 and the buffer layer 200 are immersed in a solution containing a material for forming the first rod 300 and maintained at about 70 ° C to 150 ° C.

The diameter of the first rod 300 formed thereby is 1 μm to 20 μm. In addition, the height of the first rod 300 is 0.01 μm to 10 μm. The refractive index of the first rod 300 is about 1.4 to 3.0.

Referring to FIG. 6, a second rod 400 is formed on the first rod 300. In order to form the second rod 400, a solution including a material (eg, zinc nitrate) for forming the second rod 400 is prepared. The concentration of the solution may be 0.01 M to 0.9 M. The substrate 100, the buffer layer 200, and the first rod 300 are immersed in a solution containing a material for forming the second rod 400 and maintained at about 70 ° C. to 150 ° C. .

The diameter of the second rod 400 formed thereby is between 10 nm and 500 nm. In addition, the height of the second rod 400 is 10 nm to 10,000 nm. The refractive index of the second rod 400 may be about 1.4 to 3.0.

As described above, in addition to the method of manufacturing the first rod and the second rod, a substrate patterned with a seed material may be applied to manufacture the first rod and the second rod. . In addition, the diameters of the first rods and the second rods may be controlled by growth conditions (eg, temperature, concentration, pressure, external energy, etc.) in hydrothermal synthesis.

Referring to FIG. 7, a coating layer 500 is formed on the buffer layer 200, the first rod 300, and the second rod 400.

The coating layer 500 is for improving conductivity of the transparent electrode 600. The coating layer 500 may be formed by a physical vapor deposition (PVD) process including a chemical vapor deposition (CVD) process or a sputtering process.

Referring to FIG. 8, an active layer 600 is formed on the coating layer 500. The active layer 600 may be formed by a chemical vapor deposition process and a physical vapor deposition process. The active layer 700 generates electrons and holes using incident light. The generated electrons are moved to the counter electrode 800, and holes are moved to the transparent electrode 600.

In addition, after the active layer 600 is formed, the counter electrode 700 is formed on the active layer 600. The counter electrode 700 may be formed by a sputtering process using a silver (Ag) or aluminum (Al) target.

Alternatively, in order to form the counter electrode 700, an electrode paste may be applied and subjected to a sintering process.

Therefore, the solar cell according to the embodiment has an improved power generation efficiency, the manufacturing method of the solar cell can provide a solar cell having an improved light absorption and photoelectric conversion efficiency.

The solar cell described in the present embodiment may be applied to various solar cells such as CIGS-based solar cells, silicon-based solar cells, dye-sensitized solar cells, II-VI compound semiconductor solar cells, or III-V compound semiconductor solar cells.

Although described above with reference to the embodiment, this is only an example and not to limit the invention, those of ordinary skill in the art that the present invention is not illustrated in the above range without departing from the essential characteristics of the embodiment. It will be appreciated that many variations and applications are possible. For example, each component specifically shown in the embodiment can be modified. And differences related to such modifications and applications should be construed as being included in the scope of the invention defined in the appended claims.

1 is a cross-sectional view of a solar cell according to an embodiment.

2 is a cross-sectional view and a perspective view of a rod-shaped forming a transparent electrode of a solar cell according to an embodiment.

3 illustrates a first bar and a second bar forming a transparent electrode of a solar cell according to an embodiment.

4 to 8 are cross-sectional views of a method of manufacturing a solar cell according to one embodiment.

Claims (10)

Board; A transparent electrode disposed on the substrate; An active layer disposed on the transparent electrode; And A counter electrode disposed on the active layer, The transparent electrode is a buffer layer; A first rod disposed on the buffer layer; And a second rod disposed on the first rod. The method of claim 1, The transparent electrode further comprises a coating layer formed by coating a conductive material on the buffer layer, the first rod and the second rod. The method of claim 2, The conductive material is a PEDOT-based polymer solar cell. The method according to claim 1 or 2, The buffer layer, the first rod and the second rod is formed of the same material solar cell. The method of claim 4, wherein The same material is a zinc oxide solar cell. The method of claim 5, The zinc oxide is a solar cell doped with gallium, aluminum or boron. Forming a transparent electrode on the substrate; Forming an active layer on the transparent electrode; And Forming a counter electrode on the active layer; The forming of the transparent electrode may include forming a buffer layer on the substrate; Forming a first rod on the buffer layer; And forming a second rod on the first rod. The method of claim 7, wherein The forming of the transparent electrode may include immersing the substrate and the buffer layer in a solution containing a material for forming the first rod. The method of claim 7, wherein The forming of the transparent electrode may further include forming a coating layer by coating a conductive material on the buffer layer, the first rod, and the second rod. The method of claim 7, wherein Forming the buffer layer, the first rod and the second rod is a method of manufacturing a solar cell simultaneously formed in a continuous process.

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