KR20130102902A - Solar cell and method of fabricating the same - Google Patents

Abstract

PURPOSE: A solar cell and a method for fabricating the same are provided to obtain a large-sized substrate by maintaining a plasmon formation distance. CONSTITUTION: A first conductive electrode includes a concave-convex part. Nanoparticles are in contact with the first conductive electrode. A photoactive layer (140) covers the nanoparticles. An anti-reflective coating (150) is formed on the photoactive layer. A second conductive electrode (160) is formed on the anti-reflective coating.

Description

Solar cell and method of manufacturing the same {Solar cell and method of fabricating the same}

The present invention relates to a solar cell and a method for manufacturing the same, and more particularly, to a solar cell and a method for manufacturing the same comprising nanoparticles.

Recently, renewable energy has attracted much attention due to high oil prices and environmental problems, and research and mass production of solar cells are the most active. Solar cells are devices that convert light energy into electrical energy using the properties of semiconductors. This is because solar cells have the advantage of being able to use the energy source anywhere regardless of other renewable energy sources. In addition, solar cells are being reassessed from the standpoint of preservation of the global environment due to their no pollution, and research as a next-generation clean energy source is being actively conducted. Solar cells can be classified into bulk solar cells and thin film solar cells according to the shape of the structure. In particular, researches are being conducted to apply nanoparticles to overcome the limitations of efficiency of thin film solar cells.

Conventional solar cells using nanoparticles have many subsequent processes and maintain plasmon formation distances because many nanoparticles are formed and aligned by attaching nanohole films on substrates or spray coating and spin coating processes to improve efficiency. The problem is that it becomes very difficult to produce. In addition, this increases the manufacturing cost of the cell is accompanied by a problem that the efficiency is lowered.

The present invention has been made to solve various problems including the above problems, and provides a solar cell and a method of manufacturing the same, which have improved power conversion efficiency and are cost competitive. This problem of the present invention has been presented by way of example, and therefore, the present invention is not limited to this problem.

According to one aspect of the present invention, a solar cell is provided. The solar cell is disposed on a glass substrate, the glass substrate, and a surface opposite to the glass substrate is textured to form a first conductive electrode having irregularities, a plurality of nanoparticles in contact with the first conductive electrode, and the first conductivity. A photoactive layer disposed on an electrode and covering the plurality of nanoparticles, an antireflection layer on the photoactive layer, and a second conductive electrode on the antireflection layer.

In the solar cell, the plurality of nanoparticles may include metal nanoparticles formed by sputtering. Furthermore, the metal nanoparticles may include gold or silver.

In the solar cell, the first conductive electrode may be a transparent conductive electrode, and may include an aluminum thin film or indium tin oxide (ITO).

In the solar cell, the photoactive layer may include a PIN structure in which p layers, i layers, and n layers are sequentially stacked. Furthermore, the plurality of nanoparticles may be embedded in the p layer.

According to another aspect of the present invention, a method of manufacturing a solar cell is provided. The method of manufacturing the solar cell may include providing a glass substrate, forming a first conductive electrode on the glass substrate, and texturing the first conductive electrode to form irregularities on a surface opposite to the glass substrate; Forming a plurality of nanoparticles on the first conductive electrode by sputtering, forming a photoactive layer to cover the plurality of nanoparticles on the first conductive electrode, and forming an anti-reflection layer on the photoactive layer And forming a second conductive electrode on the anti-reflection layer.

In the method of manufacturing the solar cell, the forming of the plurality of nanoparticles may include controlling the size and separation distance of each of the plurality of nanoparticles to allow selective wavelength absorption of light.

In the method of manufacturing the solar cell, the step of controlling the size and separation distance of each of the plurality of nanoparticles may include adjusting a sputtering condition.

In the method of manufacturing the solar cell, adjusting the sputtering conditions may include adjusting the sputtering deposition time.

In the method of manufacturing the solar cell, adjusting the sputtering conditions may include adjusting the sputtering power, the sputtering bias voltage or the flow rate of the carrier gas.

According to one embodiment of the present invention made as described above, the subsequent process can be simplified, the plasmon formation distance can be kept constant, the large area of the substrate can be implemented, the power conversion efficiency is improved solar cell and its manufacturing method Can be implemented. Of course, such effects are exemplarily described, and thus the scope of the present invention is not limited thereto.

1 is a cross-sectional view illustrating a solar cell according to an embodiment of the present invention.
2 is a flowchart illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.
3 to 9 are cross-sectional views sequentially illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.
FIG. 10 is a photograph showing a plurality of nanoparticles formed by contacting a transparent conductive electrode having a concave-convex texture formed by texturing in a solar cell 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 may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, Is provided to fully inform the user. Also, for convenience of explanation, the components may be exaggerated or reduced in size.

Also, relative terms such as "top" or "above" and "bottom" or "bottom" may be used to describe the relationship of certain elements to other elements as illustrated in the figures. Relative terms may be understood to include other directions of the structure in addition to the directions depicted in the figures. For example, if the top and bottom of the structure in the figures are upside down, the elements depicted as being on the face of the top of the other elements are oriented on the face of the bottom of the other elements. Thus, the example "top" may include both "bottom" and "top" directions depending on the particular direction of the figure.

First, it looks at the solar cell according to an embodiment of the present invention.

1 is a cross-sectional view illustrating a solar cell according to an embodiment of the present invention. Referring to FIG. 1, the solar cell 100 includes a glass substrate 110. In the case of forming a semiconductor material having a high light absorption coefficient on the glass substrate 110, since the solar cell 100 requires a relatively small amount of the semiconductor material, the material cost is low and the manufacturing process can be processed in a batch, so the manufacturing cost is high. Is advantageous in

The first conductive electrode 120 is disposed on the glass substrate 110. The first conductive electrode 120 is a transparent conducting electrode, and may include, for example, an aluminum thin film or indium tin oxide (ITO), sputtering or a low pressure chemical vapor phase. It may be deposited using a low pressure chemical vapor deposition (LPCVD) method. The aluminum thin film may have a thickness of several tens to several tens of nanometers, for example, about 10 nm. The first conductive electrode 120 may be formed after cleaning the glass substrate 110 to remove a material interposed between the glass substrate 110 and the first conductive electrode 120. Since the material interposed between the glass substrate 110 and the first conductive electrode 120 does not exist, the first conductive electrode 120 may have an effect of improving adhesion on the glass substrate 110.

In order to increase light absorption, a surface texturing process may be performed on the first conductive electrode 120 to form irregularities on the surface thereof. The surface texturing process may include a process of wet etching the surface using an acid or alkaline solution or a process of dry etching the surface using plasma. The reflectivity, conversion efficiency, and quantum efficiency of light may be influenced by the shape of the surface irregularities of the first conductive electrode 120.

The surface opposite to the glass substrate 110 is textured to form a plurality of nanoparticles 130 in contact with the first conductive electrode 120 on the unevenly formed first conductive electrode 120. The plurality of nanoparticles 130 may be deposited by nano cluster sputtering, and may include, for example, gold (Au) or silver (Ag). However, the material constituting the plurality of nanoparticles 130 is not limited thereto, and may include, for example, titanium, platinum, palladium, aluminum, cobalt, iron, copper, tin, nickel, or zinc. Nano cluster sputtering is a kind of sputtering, in which nanoparticles in the form of nanoclusters are formed at the beginning of deposition, and as the deposition time increases, the nanocluster forms of the nanoclusters are formed into a nano thin film. Therefore, the nanoparticles constituting the solar cell according to the embodiment of the present invention may include nanoclustered particles before forming the nano thin film by using nanocluster sputtering.

The plurality of nanoparticles 130 may be adjusted in size and distance of each of the plurality of nanoparticles 130 to allow selective wavelength absorption of light. For this purpose, the sputtering process conditions can be controlled, for example, the sputtering deposition time, the sputtering power, the sputtering bias voltage or the flow rate of the carrier gas.

By controlling the sputtering process conditions to control the size and separation distance of each of the plurality of nanoparticles 130, the absorption of light in the full-wavelength region (300nm to 1000nm) from near infrared to visible light is increased to increase the absorption and quantum efficiency of the solar cell. An improved effect can be expected. For example, absorption of short wavelengths increases at grain sizes of 50 nm or less, and scattering of long wavelengths increases at grain sizes of 100 nm.

That is, by precisely controlling the size of the nanoparticles 130, for example, from 10 nm to 100 nm by adjusting the sputtering process conditions, it is possible to amplify the light of the selective wavelength and also to adjust the scattering angle according to the incident angle of the light. You can expect the effect. The optimal size of the nanoparticles 130 can be set by observing the surface plasmon resonance effect, which will be briefly described.

The solar cell uses the principle of absorbing light and generating electrons, so the more the solar light is absorbed, the better the condition of the cell can be. In order to absorb a lot of sunlight, it is also possible to maximize the light absorption capacity as well as the method of widening the light absorption region to a long wavelength. One method of maximizing light absorption is to use surface plasmon resonance. Free electrons exist on the surface of the metal nanoparticles. Free electrons on this surface interact with external electromagnetic waves and move on metal surfaces. The movement of these free electrons changes the polarity of the material around the metal nanoparticles, thereby changing the polarization rate of the material around the metal nanoparticles. The change in polarization rate results in an increase in the absorbance of the material surrounding the metal nanoparticles.

As a result, from the outside, the absorbance of any material, including gold or silver nanoparticles, will increase. By utilizing the surface plasmon resonance phenomenon, it is possible to maximize the utilization of sunlight by increasing the light absorption capacity (absorbance) of the material, so that the optimum size of the metal nanoparticles to observe the surface plasmon resonance phenomenon to improve the light absorption capacity Can be determined.

Subsequently, referring to FIG. 1, a photoactive layer 140 covering the plurality of nanoparticles 130 is disposed on the first conductive electrode 120. The photoactive layer 140 is made of a photoactive material capable of receiving light to generate electrons. The electrons generated by the light move to the second conductive electrode 160 having a low work function, and the holes move to the first conductive electrode 120 having a high work function. The photoactive layer 140 may include, for example, a PIN structure in which p layers 142, i layers 144, and n layers 146 are sequentially stacked. The plurality of nanoparticles 130 may be embedded in the p layer 142. That is, the plurality of nanoparticles 130 may be embedded only in the p layer 142 without being embedded in the i layer 144 or the n layer 146.

Here, p layer 142 means one or more p-doped layers, and i layer 144 means one or more undoped layers (in electrical terms) or a slightly doped layer in comparison, which is one The above photons are absorbed and contribute to the generation of current, and n layer 146 means one or more n-doped layers. The PIN structure 140 that absorbs light to form excitons may be formed by successive stacking, for example, having a thickness of 500 nm or less.

The antireflection layer 150 is disposed on the photoactive layer 140. The anti-reflection layer 150 is introduced to suppress a phenomenon in which efficiency is reduced due to the reflection of light, and may be formed, for example, at a thickness of 100 nm or less. The second conductive electrode 160 is disposed on the antireflection layer 150. The second conductive electrode 160 constitutes an upper electrode for external signal transmission. When the photoactive layer 140 receives light, electrons and holes are generated, and electrons may move to the second conductive electrode 160 having a relatively low work function. The solar cell 100 includes a trench T formed by performing an edge process to suppress crosstalk between devices.

Next, look at the manufacturing method of the solar cell according to an embodiment of the present invention.

2 is a flowchart illustrating a method of manufacturing a solar cell according to an embodiment of the present invention. Referring to FIG. 2, in the method of manufacturing a solar cell according to an embodiment of the present invention, providing a glass substrate 110 (S10) and forming a first conductive electrode 120 on the glass substrate 110. In operation S20, texturing the first conductive electrode 120 to form irregularities on a surface opposite to the glass substrate 110 on the first conductive electrode 120 (S30) and the first conductive electrode 120. Forming a plurality of nanoparticles 130 by sputtering on (S40), forming a photoactive layer 140 on the first conductive electrode 120 to cover the plurality of nanoparticles (130) (S50) ), Forming the anti-reflection layer 150 on the photoactive layer 140 (S60), forming the second conductive electrode 160 on the anti-reflection layer 150 (S70) and performing an edge process (S80). Hereinafter, the steps will be described with reference to FIGS. 3 to 9 sequentially. However, contents overlapping with the parts already described in FIG. 1 will be omitted for convenience.

3 and 4, the first conductive electrode 120 is formed on the glass substrate 110. A surface texturing process may be performed on the first conductive electrode 120 to form irregularities on the surface thereof. That is, after the glass substrate 110 is cleaned and the first conductive layer 120a is formed, a process of wet etching the surface of the first conductive layer 120a using an acid or an alkaline solution or a first conductivity using a plasma is performed. A process of dry etching the surface of the layer 120a may be performed.

Referring to FIG. 5, a plurality of nanoparticles 130 are formed by sputtering on the first conductive electrode 120. According to an embodiment of the present invention, a sputtering process has been proposed as a method for forming the metal nanoparticles 130. Hereinafter, the effects expected by the metal nanoparticles 130 formed by the sputtering will be described.

First, a uniform array of metal nanoparticles 130 may be formed. Uniformity of the array is one of the important conditions in the field of nanoparticle array manufacturing because the uniformity of the arrangement of the metal nanoparticles improves the properties. For example, in order to observe the plasmon resonance characteristic, the absorbance should be measured. As the size of the metal nanoparticles 130 causing the characteristic is uniform, the wavelength range of the absorbed light is limited and the degree thereof is increased. It is easy to apply to the field. In addition, uniformity of the size of the nanoparticles 130 is essential for reproducibility of the characteristics. If the size is non-uniform, the properties are all different depending on the time the process is performed, which is not suitable for practical use. When using the metal thin film dewetting by coprecipitation or heat, which is most commonly used in the industry or the laboratory, the uniformity of nanoparticles becomes a problem, but according to an embodiment of the present application, a uniform array of metal nanoparticles 130 may be manufactured. Do.

Next, it is possible to manufacture an array of metal nanoparticles 130 that can control the size and spacing of the particles. At the same time as manufacturing a uniform array of metal nanoparticles 130 should also be able to control the size of the particles constituting the array itself. Control of properties in the field of application of the metal nanoparticle 130 array may be implemented through particle size control. Furthermore, it is desirable that the range of size adjustment is also wide. There are many known methods for producing uniform metal particles by chemical synthesis, but the range of size control is very small, ranging from several nm to several tens of nm. The process of widening the adjustable range to 100 nm is accompanied by a significant decrease in uniformity. Therefore, a process for controlling the size under a wide range while maintaining the uniformity of the particles is essential. According to the exemplary embodiment of the present application, the size of the metal nanoparticles 130 may be adjusted to a thickness of a thin film that may be deposited, and the spacing between particles may be controlled by using a plasma sputtering effect. For example, the plasma sputtering effect may be controlled by applying a bias on the substrate and then adjusting the voltage to adjust the size and / or spacing between the particles.

Next, low temperature process technology becomes possible. Low process temperatures are required in practical applications of various arrays of metal nanoparticles 130. For example, in order to form the metal nanoparticles 130 on the flexible substrate material, the process must be performed at a low temperature where no denaturation occurs. Processes for manufacturing metal nanoparticle arrays by laser or heat thin film dewetting, or processes in which the metal nanoparticles are manufactured by chemical synthesis and then bonded to the substrate by heat treatment are not suitable for low temperature processes. Do. Low temperature process is one of the advantages of the inductively coupled plasma that can be used in one embodiment of the present application. Therefore, according to the exemplary embodiment of the present application, the array of metal nanoparticles 130 may be easily implemented by a low temperature process.

Next, an array of metal nanoparticles 130 having high adhesion to the substrate may be formed. When an array of metal nanoparticles 130 is used in a product, low adhesion to the substrate causes a vulnerability to external impact and a reduction in product life. Therefore, high adhesion between the substrate and the array of metal nanoparticles 130 is essential. In the process of preparing the metal nanoparticles 130 and spraying them onto the substrate to form an array, an additional operation such as depositing an intermediate layer or performing heat treatment is performed to improve adhesion. However, according to the exemplary embodiment of the present application, since the process of depositing the target metal thin film using sputtering and the process of generating and placing the metal nanoparticle 130 on the substrate are simultaneously performed at low temperature, the adhesive force is maintained high without further processing. Has an advantage.

Next, it may have the advantage of a short process time. Short process time is essential for the productivity of the metal nanoparticle 130 array. In most chemical synthesis processes, when metal nanoparticles are placed on a substrate, heat treatment is performed at high temperature to increase the uniformity and adhesion. Productivity is low because the time it takes is several hours. According to one embodiment of the present application, for example, using an inductively coupled plasma treatment, when manufacturing the metal nanoparticles (130) array can be expected to improve the productivity by reducing the process time is possible because the process time is less than 30 minutes have.

Next, it can have the advantage that mass production is possible. In order to increase productivity, it is essential to manufacture a large amount of the metal nanoparticle array 130 in one process. In the case of a laser process, the processable area is very narrow at one time, and thus it is difficult to be used industrially despite the advantages of uniformity and wide size range. In addition, the aerosol method can produce particles showing good uniformity, but it is a process that has a disadvantage in mass production. However, according to one embodiment of the present application, for example, in the case of using an inductively coupled plasma, it is possible to generate the metal nanoparticles 130 in a large area, because the process is widely used in mass production in the industry at present, It has the advantage of being available for production.

Next, it is possible to secure a variety of types of metal nanoparticles (130) array. In order to have an advantage in the method of manufacturing the metal nanoparticle 130 array, the target metal to be produced should be various. According to the exemplary embodiment of the present application, since the metal thin film is deposited and then post-processed to make the nanoparticle 130 array, the target material may vary. For example, the technical concept of the present disclosure may be applied to titanium, platinum, palladium, aluminum, cobalt, iron, copper, tin, nickel, zinc, gold, or silver, which are commonly used as metal particles.

6, the photoactive layer 140 is formed on the first conductive electrode 120 to cover the plurality of nanoparticles 130. As shown in FIG. 1, the photoactive layer 140 may include a PIN structure in which p layers 142, i layers 144, and n layers 146 are sequentially stacked. The plurality of nanoparticles 130 may be embedded in the p layer 142. That is, the plurality of nanoparticles 130 may be embedded only in the p layer 142 without being embedded in the i layer 144 or the n layer 146. The PIN structure 140 that absorbs light to form excitons may be formed by successive stacking, for example, having a thickness of 500 nm or less.

7 to 9, after forming the anti-reflection layer 150 on the photoactive layer 140 and forming the second conductive electrode 160 on the anti-reflection layer 150, an edge process may be performed. have. The trench T formed by performing the edge process separates the devices A and B and further suppresses crosstalk between the devices.

As described above, according to the method of manufacturing a solar cell according to an embodiment of the present invention, the plurality of nanoparticles 130 have a size and a separation distance of each of the plurality of nanoparticles 130 to allow selective wavelength absorption of light. Can be adjusted. For this purpose, the sputtering process conditions can be controlled, for example, the sputtering deposition time, the sputtering power, the sputtering bias voltage or the flow rate of the carrier gas.

FIG. 10 is a photograph showing a plurality of nanoparticles formed by contacting a transparent conductive electrode having a concave-convex texture formed by texturing in a solar cell according to an embodiment of the present invention.

Referring to FIG. 10, as described above, the surface of the first conductive electrode 120 in the form of a transparent conductive electrode is textured to form irregularities. Since the irregularities are formed, the valleys appear in the form of dark borders in the photograph. It can be seen that the plurality of nanoparticles 130 are disposed on the first conductive electrode 120 in the form of nano clusters.

The foregoing description of specific embodiments of the invention has been presented for purposes of illustration and description. 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 as defined by the appended claims. Do. For example, the solar cell according to an embodiment of the present invention may be applied to a silicon (crystalline, thin film) solar cell or a compound solar cell.

100: Solar cell
110: glass substrate
120: first conductive electrode
130: nanoparticles
140: photoactive layer
150: antireflection layer
160: second conductive electrode

Claims (11)

A glass substrate;
A first conductive electrode disposed on the glass substrate and having an uneven surface formed by texturing the surface opposite to the glass substrate;
A plurality of nanoparticles in contact with the first conductive electrode;
A photoactive layer disposed on the first conductive electrode and covering the plurality of nanoparticles;
An antireflection layer on the photoactive layer; And
And a second conductive electrode on the anti-reflection layer. The method of claim 1,
The plurality of nanoparticles comprises metal nanoparticles formed by sputtering. The method of claim 2,
The metal nanoparticles comprise gold or silver, solar cell. The method of claim 1,
The first conductive electrode is a transparent conductive electrode, comprising a thin aluminum film or indium tin oxide (ITO), solar cell. The method of claim 1,
The photoactive layer includes a PIN structure in which p-layers, i-layers, and n-layers are successively stacked. The method of claim 5,
The plurality of nanoparticles are embedded in the p layer, solar cell. Providing a glass substrate;
Forming a first conductive electrode on the glass substrate;
Texturing the first conductive electrode to form irregularities on a surface opposite to the glass substrate;
Forming a plurality of nanoparticles on the first conductive electrode by sputtering;
Forming a photoactive layer on the first conductive electrode to cover the plurality of nanoparticles;
Forming an anti-reflection layer on the photoactive layer; And
And forming a second conductive electrode on the anti-reflection layer. The method of claim 7, wherein
Forming the plurality of nanoparticles includes controlling the size and separation distance of each of the plurality of nanoparticles to allow selective wavelength absorption of light, the manufacturing method of a solar cell. 9. The method of claim 8,
Controlling the size and separation distance of each of the plurality of nanoparticles comprises the step of adjusting the sputtering conditions, solar cell manufacturing method. 10. The method of claim 9,
Adjusting the sputtering conditions includes the step of adjusting the sputtering deposition time, solar cell manufacturing method. 10. The method of claim 9,
Adjusting the sputtering conditions includes the step of adjusting the flow rate of the sputtering power, sputtering bias voltage or carrier gas, solar cell manufacturing method.

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