KR101441377B1 - Solar Cell And Fabricating Method Thereof - Google Patents

Abstract

The present invention relates to a solar cell capable of improving the efficiency of an electromotive force and reducing a cost, and a manufacturing method thereof.

The solar cell according to the present invention has a first organic layer having an irregular top surface and a first organic layer having a p-type semiconductor property, and a bottom surface having a concavo-convex pattern formed on the first organic layer and an inverted- A second organic material layer having a second organic material layer; And an inorganic semiconductor layer interposed between the upper surface of the first organic material layer and the lower surface of the second organic material layer and having a nano-sized thickness, wherein the first organic material layer comprises a soft mold having grooves and protrusions And the second organic material layer and the first organic material layer are formed to be in mesh with each other with the inorganic semiconductor layer interposed therebetween.

Description

[0001] Solar Cell and Fabricating Method Thereof [0002]

1 is a view showing the principle of a solar cell;

2 is a cross-sectional view showing the structure of a conventional conventional solar cell.

3 is a cross-sectional view illustrating a solar cell according to a first embodiment of the present invention;

4A to 4E are cross-sectional views showing steps of the method for manufacturing the solar cell of FIG. 3;

5 is a sectional view showing a solar cell according to a second embodiment of the present invention.

6A to 6C are cross-sectional views showing steps of the method for manufacturing the solar cell of FIG.

7 is a photograph showing the surface of an inorganic material in a state where the inorganic material is heat-treated and then cooled in contact with the organic material.

    Description of the Related Art

4,26: n-type semiconductor 6,24: p-type semiconductor

10: bulb 20,120,220: first substrate

30, 130, 230: second substrate 22, 122, 222:

28, 128, 228: second electrode 123, 223: first organic layer

125, 225: second organic layer 124, 224: first organic layer

28, 128, 228: second electrode 140: soft mold

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell, and more particularly, to a solar cell capable of improving the efficiency of an electromotive force and reducing a cost, and a manufacturing method thereof.

A solar cell is a photovoltaic device that converts light energy into electrical energy using semiconductors.

The principle of converting solar light into electrical energy in solar cells uses the p-n junction principle of semiconductors.

Semiconductors such as silicon (Si), germanium (Ge), and arsenic (As) have a conduction band and a valence band. In the region where electrons can not exist between the valence band and the conduction band, (forbidden band). Here, the width of the forbidden band is referred to as an energy gap. When energy corresponding to an energy gap (for example, light) is supplied to such a semiconductor, a photon is absorbed in the semiconductor, and the absorbed photon absorbs electrons in a stable state in the semiconductor as a pair It can be changed into free electrons and holes. The generated electrons and holes are stable during a certain time, so electrons having a negative charge and holes having a positive charge are separated from each other within a certain period of time, and then connected to an external circuit through an electrode terminal to function as a solar cell .

Hereinafter, the principle of the solar cell will be described in more detail with reference to FIG.

First, a p-type semiconductor 4 and an n-type semiconductor 6 are formed in one crystal by doping a p-type impurity into one portion of the semiconductor crystal and doping the remaining portion with an n-type impurity. Here, the metallographic interface between the p-type semiconductor 4 and the n-type semiconductor 6 is referred to as a p-n junction. The p-type semiconductor 4 is doped with a trivalent acceptor atom, so that a large amount of holes are generated. Since the n-type semiconductor 6 is doped with donor atoms having five valences, many electrons are formed. Therefore, as the hole concentration and the electron concentration of the p-type and n-type semiconductors differ from each other, the holes diffuse toward the n-type semiconductor and the electrons diffuse toward the p-type semiconductor in the pn junction, Only the ion remains, and only the (+) charged donor ion remains on the n-type semiconductor. As a result, since the electric field is formed at the p-n junction, the diffusion of holes and electrons is suppressed, resulting in a thermal equilibrium state. When a light energy source is externally applied to the pn junction reaching this thermal equilibrium state, a positive (+) voltage is shown for the p-type semiconductor and a negative (-) voltage for the n- . Thus, a device capable of generating current (I) using light energy is called a solar cell, and such a solar cell can supply electricity to the bulb 10 as a means of supplying electromotive force.

2 is a cross-sectional view showing a structure of a conventional solar cell capable of generating an electromotive force by the principle described in FIG.

A first electrode 22 (or an "anode electrode"), a p-type semiconductor 24, an n-type semiconductor 26, a second electrode 28 Quot;) are stacked, and the second substrate 30 is placed on the second electrode 28. A p-n junction is formed between the p-type semiconductor 24 and the n-type semiconductor 26. The first and second substrates 20 and 30 are formed of tempered glass to protect the p-type semiconductor 24 and the n-type semiconductor 26 from external impacts.

Such a material constituting the solar cell in Conventional 1 is all formed of an inorganic material, and as a result, it is broken easily because of no flexibility or flexibility.

Accordingly, an organic solar cell using a substrate having flexibility and flexibility instead of tempered glass while using organic materials or conductive polymers having semiconductor properties has been proposed. Organic solar cells can be manufactured in the form of thin films because of their flexible nature, and they are expected to be free from space limitations and to be used in various applications.

However, the organic solar cell has a disadvantage in that the conversion efficiency of light energy into electric energy is significantly lowered to about 10% as compared with a solar cell using an inorganic semiconductor.

Accordingly, an object of the present invention is to provide a solar cell having improved electromotive force generation efficiency and flexibility, and a method of manufacturing the same.

Further, it is a further object of the present invention to provide a solar cell and a manufacturing method thereof that can reduce cost and make it large.

In order to achieve the above object, a solar cell according to the present invention includes: a first organic material layer and a second organic material layer having semiconductor characteristics; And an inorganic semiconductor layer interposed between the first organic material layer and the second organic material layer, wherein the inorganic semiconductor layer is formed to have a nano-sized thickness, and has a structure of either a concavo-convex pattern or a wave pattern .

And the inorganic semiconductor layer is titanium dioxide (TiO ₂ ).

The first organic compound layer has a p-type semiconductor property, the second organic compound layer has an n-type semiconductor property, and the inorganic semiconductor layer is a p-n junction region.

The first organic material layer and the second organic material layer are formed so as to mesh with each other with the inorganic semiconductor layer of the irregular pattern shape therebetween.

The second organic material layer is formed in the inorganic semiconductor layer so as to have a wave pattern in contact with the surface of the wave pattern structure and invertedly transferred to the wave pattern.

Wherein the first organic layer comprises at least one of PEDOT: PSS and polyaniline and the second organic layer comprises MEH-PPV (poly 2-methoxy-5-2'-ethyl-hexyloxy-14-phenylene (2'-ethyl-hexyloxy) -14-phenylenevinylene}] and polyfluorene.

A second electrode located above the second organic layer; A first substrate positioned below the first electrode; And a second substrate located above the second electrode.

A method of manufacturing a solar cell according to the present invention includes: forming a first electrode on a first substrate; Forming a first organic layer having p-type semiconductor characteristics on the first electrode; Forming an inorganic semiconductor layer having a nano-sized thickness and having a structure of a concavo-convex pattern or a wave pattern; And forming a second organic material layer having n-type semiconductor characteristics on the inorganic semiconductor layer.

The forming of the first organic material layer may include forming an organic material having p-type semiconductor characteristics on the first electrode; And pressing and heat-treating the organic material using a soft mold having grooves and protrusions to form the first organic layer having a concavo-convex pattern in the form of being reversely transferred to the grooves and the protrusions.

The pressurization and the heat treatment are carried out at a pressure of about 1.01 to 20 atm for about 1 to 60 minutes in an environment of about 150 to 230 deg.

Wherein the second organic compound layer is formed to have a concavo-convex pattern formed on the first organic compound layer and a concavo-convex pattern formed by inverted transfer, and the second organic compound layer and the first organic compound layer are formed so as to be in mesh with each other with the concavo- do.

The step of forming the inorganic semiconductor layer having the wave pattern structure may include forming an inorganic semiconductor material on the first organic material layer; Treating the substrate in an environment of about 150 to 230 DEG C for 1 to 60 minutes and then cooling the substrate.

Forming a second electrode overlying the second organic layer; And forming a second substrate on the second electrode.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the accompanying drawings.

Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. 3 to 7. FIG.

3 is a cross-sectional view illustrating a solar cell according to a first embodiment of the present invention.

The solar cell shown in FIG. 3 includes a first electrode 122 (or an "anode electrode") sequentially stacked on a first substrate 120, a first organic layer 123 serving as a p-type semiconductor, a pn- (Or "cathode electrode") and a second electrode 128, which serves as an n-type semiconductor, are laminated on the first electrode 128 and the second electrode 128 The second substrate 130 is located.

First, the first and second substrates 120 and 130 may be a conventional glass substrate, or a flexible and flexible film may be used.

The first electrode 122 is formed of a transparent conductive material such as ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), ITZO (Indium Tin Zinc Oxide), or the like and is formed of gold (Au), platinum (Pt) And the like.

As the second electrode 128, aluminum (Al) or an aluminum alloy is used.

The first organic material layer 123 is formed on the first electrode 122 and has a concavo-convex shape on its surface that is not in contact with the first electrode 122. The second organic layer 125 is formed between the second electrode 128 and the first organic layer 123 and the surface of the second organic layer 125 that is not in contact with the second electrode 128 is inverted and transferred to the first organic layer 123 . That is, the second organic layer 125 is also formed in a concavo-convex shape, the protruding region of the first organic layer 123 corresponds to the groove of the second organic layer 125, the groove of the first organic layer 123 corresponds to the groove of the second organic layer 125, As shown in Fig.

Here, the first organic material layer 123 has a function of transporting holes as a polymer having conductivity. For example, the hole transport layer material PEDOT: PSS (PEDOT: PSS) in the organic electroluminescence display OLED is made from a conductive poly (3,4-ethylenedioxythiophene) doped with poly (4-styrenesulfonate) Material), polyaniline, and the like are used. The second organic material layer 125 may also be a polymer having conductivity, such as MEH-PPV (poly (2-methoxy-5- (2'-ethyl-hexyloxy) -14-phenylenevinylene} Polyfluorene or the like is used.

The inorganic semiconductor layer 124 is made of titanium dioxide (TiO ₂ ) and is positioned between the first organic layer 123 and the second organic layer 125 and has a nano-sized thickness. The inorganic semiconductor layer 124 is also formed in a concavo-convex form between the first organic layer 123 and the second organic layer 125, and the uneven surface of the first organic layer 123 and the uneven surface of the second organic layer 125 Respectively. Here, titanium dioxide (TiO ₂ ) is one of the inorganic semiconductor compounds having the band gap energy of the valence band of the valence band and the conduction band. Accordingly, titanium dioxide (TiO ₂ ) can serve as a pn junction region in the solar cell of the present invention. At this time, the titanium dioxide (TiO ₂ ) is formed to have a nano-sized thickness and the concavo-convex shape, so that the contact area of the neighboring conductive polymer, that is, the first and second organic layers 123 and 125, increases. When the pn junction in the solar cell is widened, the amount of acceptor ion charged with (-) and donor ion charged with (+) increases in proportion to the widened pn junction. As a result, the amount of the acceptor ion charged with (-) and the donor ion charged with (+), which is suppressed by the electric field and reaches the thermal equilibrium state, becomes large and the current (I) .

As a result, as the p-n junction region is widened, the efficiency of converting the light energy generated into electric energy is improved, and the magnitude of the photovoltaic power is improved.

As described above, the solar cell according to the first embodiment of the present invention forms the inorganic semiconductor layer 124 having the p-n junction function between the first and second organic material layers formed to be in mesh with each other. As a result, the area of the p-n junction region is widened, thereby increasing the magnitude of the photovoltaic power. In addition, it is possible to convert light energy into electrical energy by using an organic conductive polymer material instead of an n-type semiconductor and a p-type semiconductor, which are conventionally inorganic materials, so that a solar cell having flexibility and flexibility can be formed.

4A to 4E show a manufacturing process of a solar cell according to the first embodiment of the present invention.

First, referring to FIG. 4A, a first electrode 122 is formed on a first substrate 120 formed of a film or glass by a deposition method such as sputtering, and a coating method such as spin coating or spinless coating is performed The first organic material 123a is applied. The first electrode 122 may be formed of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), or indium tin zinc oxide (ITZO) (Cu) or the like may be included. The first organic material 123a may be an organic material or a conductive polymer having a semiconducting property. For example, materials such as PEDOT: PSS, polyaniline and the like are used.

Referring to FIG. 4B, a first organic layer 123 is formed by an in-plane printing (IPP) method using a soft mold 140.

More specifically, the soft mold is aligned on the first organic material 123a. The soft mold 140 is made of polydimethylsiloxane (PDMS), polyurethane, cross-linked novolac resin or the like, and the surface corresponding to the first organic material 123a And has a concavo-convex structure composed of a groove and a protruding portion.

The soft mold 140 is pressed against the first organic material 123a and heat-treated. Thus, the concave and convex structure of the inverted transfer form of the groove and protrusion of the soft mold 140 is formed in the first organic material 123a. Thus, the first organic material layer 123 having the concavo-convex shape is formed. Here, the pressure applied to the first organic material 123a by the soft mold 140 is about 1.01 to 20 atm, and the heat treatment is performed at a temperature of about 150 to 230 ° C for 1 to 60 minutes.

Thereafter, the soft mold 140 is separated from the first organic layer 123.

Referring to FIG. 4C, an inorganic semiconductor layer 124, for example, a titanium dioxide (TiO ₂ ) layer is formed on the first organic layer 123 by a deposition method such as sputtering. Since the inorganic semiconductor layer 124 is formed to have a nano-sized thickness, the concavo-convex shape formed in the first organic layer 123 is maintained.

On the other hand, as a method for forming a nano-sized titanium dioxide (TiO ₂ ) layer, there has been proposed a technique of forming a nanorod by crystal growth of titanium dioxide (TiO ₂ ). However, the process of growing titanium dioxide (TiO ₂ ) crystals has disadvantages such as high cost due to expensive equipment, difficulty in processing, lowering of uniformity and lowering of reliability.

However, in the present invention, since the first organic layer 123 can be formed by the IPP method using the soft mold 140, a titanium dioxide (TiO ₂ ) layer having a relatively simple process and a much better uniformity at a low cost can be obtained .

Referring to FIG. 4D, a second organic material layer 125 is formed on the inorganic semiconductor layer 124 having a nano-sized thickness using a coating method such as spin coating or spinless coating. The second organic layer 125 can be formed in the concavo-convex shape as the second organic layer 125 is inserted into the groove region of the concavo-convex structure formed by the first organic layer 123. [ The second organic material layer 125 may be a polymer having conductivity, such as poly {2-methoxy-5- (2'-ethyl-hexyloxy) -14-phenylenevinylene}, a light emitting material capable of transporting electrons, Polyfluorene or the like is used.

Referring to FIG. 4E, a second electrode 128 is formed by depositing a conductive metal such as aluminum (Al) through a deposition method such as sputtering, and a second substrate 130 is formed on the second electrode 128 do.

As described above, the solar cell according to the first embodiment of the present invention and the manufacturing method thereof form the inorganic semiconductor layer 124 having the p-n junction function between the first and second organic material layers formed so as to mesh with each other. As a result, the area of the p-n junction region is widened, thereby increasing the magnitude of the photovoltaic power. Furthermore, by using an organic material or a conductive polymer having a semiconducting property, flexibility and flexibility, which are advantages of an organic solar cell, are obtained, and it is advantageous in manufacturing a large area solar cell by being formed by an imprinting method.

5 is a cross-sectional view illustrating a solar cell and a method of manufacturing the same according to a second embodiment of the present invention.

The solar cell in FIG. 5 proposes a method of widening the area of the titanium dioxide (TiO ₂ ) layer functioning as a pn junction by using the difference in thermal expansion coefficient, not the imprinting method proposed in the first embodiment of the present invention .

The first electrode 222 (or the "anode electrode") sequentially stacked on the first substrate 220, the first organic layer 223 serving as a p-type semiconductor, the pn junction region (Or "cathode electrode") and a second electrode 228 (or " cathode electrode ") are stacked on the second electrode 228. The second electrode 228 2 substrate 230 is positioned.

Unlike the first embodiment of the present invention, the first organic material layer 223 has no concavo-convex structure. Accordingly, the surface of the inorganic semiconductor layer 224 made of titanium dioxide (TiO ₂ ) that is in contact with the first organic layer 223 also has no concavo-convex shape. However, the surface of the inorganic semiconductor layer 224 in contact with the second organic layer 235 is formed to have a wave shape. As a result, the second organic layer 235 in contact with the inorganic semiconductor layer 224 is also formed to have a wave shape.

Accordingly, the solar cell according to the second embodiment of the present invention also has an increased area of the titanium dioxide (TiO ₂ ) layer having the pn junction function, thereby improving the magnitude of the photovoltaic power. Further, by using an organic material or a conductive polymer having a semiconducting property, flexibility and flexibility, which are advantages of an organic solar cell, are obtained, and it is advantageous in manufacturing a large area solar cell by being formed by imprinting.

The solar cell according to the second embodiment of the present invention has the same configuration and characteristics as the solar cell according to the first embodiment of the present invention except for the structure of the inorganic semiconductor layer 224 and the first and second organic layers 223 and 225 . Therefore, redundant description will be omitted.

6A to 6C are sectional views showing a manufacturing method of the solar cell shown in FIG.

First, referring to FIG. 6A, a first electrode 222 is formed on a first substrate 220 formed of a film or glass by a deposition method such as sputtering, and a coating method such as spin coating or spinless coating is used The first organic material layer 223 is formed. The first electrode 122 may be formed of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), or indium tin zinc oxide (ITZO) (Cu) or the like may be included. The first organic material layer 223 may be an organic material or a conductive polymer having a semiconducting property. For example, materials such as PEDOT: PSS, polyaniline and the like are used.

An inorganic semiconductor layer 224 having a semiconductor property, for example, a titanium dioxide (TiO ₂ ) layer is formed on the first organic layer 223 by a vapor deposition method such as sputtering. The inorganic semiconductor layer 124 is formed to have a nano-sized thickness.

After that, heat treatment is performed at a temperature of about 150 to 230 ° C. for 1 to 60 minutes (min), followed by cooling.

6B, the surface of the inorganic semiconductor layer 224 which is not in contact with the first organic layer 223 is not restored due to the difference in thermal expansion coefficient between the first organic material 223 and the inorganic semiconductor layer 224 Wave shape.

This will be described in more detail as follows.

Organic matter has a much higher coefficient of thermal expansion than that of inorganic materials, and its ability to recover after heat treatment is also superior to inorganic materials. Accordingly, when heat is applied to the inorganic semiconductor layer 224 and the first organic material layer 223 which are in contact with each other at the same time, the first organic material layer 223 expands much more than the inorganic semiconductor layer 224. At this time, the surface of the inorganic semiconductor layer 224 which is in contact with the first organic material layer 223 is expanded to a certain extent by the expansion of the first organic material layer 223. Accordingly, deformation of the internal structure occurs due to generation of internal stress and grain boundaries in the inorganic semiconductor layer 224.

Thereafter, when the heat supply is stopped and cooled, the first organic layer 223 is restored, but the inorganic semiconductor layer 224 in which the internal structure is deformed has a wave shape as shown in FIG. 6B.

The inventor of the present invention obtained the results shown in FIG. 7 by thermally expanding PEDOT: PSS in a state where AlO ₂ is laminated on the PSS, cooling it, and observing its surface. That is, when the organic material and the inorganic material are brought into contact with each other and then cooled after the heat treatment, the surface as shown in FIG. 7 becomes convex.

Referring to FIG. 6C, a second organic material layer 225 is formed on the inorganic semiconductor layer 224 using a coating method such as spin coating or spinless coating. The surface of the second organic compound layer 225 which is in contact with the inorganic semiconductor layer 224 has a wave pattern of a form inverted and transferred by the wave pattern of the inorganic semiconductor layer 224. [

Thereafter, a second electrode 228 is formed by depositing a conductive metal such as aluminum (Al) through a deposition method such as sputtering, and the second substrate 230 is formed on the second electrode 228. Accordingly, The solar cell shown in Fig.

As described above, the solar cell and the manufacturing method thereof according to the present invention form an inorganic semiconductor layer having a p-n junction function between the first and second organic material layers having semiconductor characteristics and having a concavo-convex shape or a wave pattern. As a result, the area of the p-n junction region is widened, thereby increasing the magnitude of the photovoltaic power. Further, by using an organic material or a conductive polymer having a semiconducting property, flexibility and flexibility that are advantages of the organic solar cell are obtained. Furthermore, the inorganic semiconductor layer forming process having a pn junction function and having a concave-convex shape or a wave pattern can be formed through heat treatment using imprinting method or thermal expansion coefficient difference, . ≪ / RTI >

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 or scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

Claims (14)

A first organic material layer having an irregular top surface, a first organic material layer having a p-type semiconductor property, and a second organic material layer having an irregular pattern formed on the first organic material layer and a reverse irregular pattern on the bottom surface, And And an inorganic semiconductor layer interposed between the upper surface of the first organic material layer and the lower surface of the second organic material layer and having a nano-sized thickness, The first organic material layer is formed by pressing and heating the organic material using a soft mold having grooves and protrusions, Wherein the second organic material layer and the first organic material layer are formed so as to mesh with each other with the inorganic semiconductor layer interposed therebetween. The method according to claim 1, Wherein the inorganic semiconductor layer is titanium dioxide (TiO ₂ ). The method according to claim 1, Wherein the first organic material layer has a P-type semiconductor property, The second organic material layer has an n-type semiconductor characteristic, Wherein the inorganic semiconductor layer is a p-n junction region. delete delete The method according to claim 1, Wherein the first organic layer includes at least one of PEDOT: PSS and polyaniline, The second organic layer may be a poly (2-methoxy-5- (2'-ethyl-hexyloxy) - poly (2-methoxy- 14-phenylenevinylene}], and polyfluorene. The method according to claim 1, A first electrode positioned below the first organic layer; A second electrode located above the second organic layer; A first substrate positioned below the first electrode; And a second substrate located above the second electrode. Forming a first electrode on a first substrate; Forming an organic material having a p-type semiconductor property on the first electrode, pressing and heat-treating the organic material using a soft mold having a groove and a protrusion to form a recessed pattern having an inverted pattern transferred to the groove and the protrusion, 1 organic material layer; Forming an inorganic semiconductor layer having a nano-sized thickness on the first organic material layer and along the concavo-convex pattern of the first organic material layer; And forming a second organic compound layer having n-type semiconductor characteristics on the inorganic semiconductor layer so as to mesh with each other with the inorganic semiconductor layer sandwiched therebetween and having a concavo-convex pattern of the first organic compound layer and an inverted- Wherein the photovoltaic cell is a solar cell. delete 9. The method of claim 8, Wherein the pressing and the heat treatment are performed for 1 to 60 minutes in an environment of about 150 to 230 DEG C under a pressure of about 1.01 to 20 atm. delete delete 9. The method of claim 8, Wherein the inorganic semiconductor layer is titanium dioxide (TiO ₂ ). 9. The method of claim 8, Forming a second electrode overlying the second organic layer; And forming a second substrate on the second electrode.

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