KR101074577B1 - Organic-inorganic hybrid solar cell and preparation method thereof - Google Patents

Abstract

A lower plate comprising a first substrate, a first electrode formed on the first substrate, and a semiconductor layer formed on the first electrode and adsorbed with metal carbonate, a second substrate, a second electrode formed on the second substrate, and An upper plate formed on the second electrode and including a counter electrode facing the semiconductor layer, a sealing member for sealing the lower plate and the upper plate, and an electrolyte layer injected between the lower plate and the upper plate sealed by the sealing member. Disclosed is a solar cell. The method may further include forming a lower plate including a first substrate, a first electrode formed on the first substrate, and a semiconductor layer formed on the first electrode, and depositing the lower plate in a solution containing metal carbonate. Disclosed is a method of manufacturing a solar cell comprising the step of adsorbing the metal carbonate.

Description

Organic-inorganic hybrid solar cell and its manufacturing method {ORGANIC-INORGANIC HYBRID SOLAR CELL AND PREPARATION METHOD THEREOF}

The present invention relates to a solar cell and a method for manufacturing the solar cell, and to a method for manufacturing a solar cell having improved photoelectric conversion efficiency.

There is a need for clean, unlimited energy that differs from the existing ones, such as the risk of depletion of fossil fuels such as oil, coal and natural gas, the entry into force of the Kyoto Protocol's climate change agreement, and the explosive energy demands of emerging economies (BRICs). At the national level, new and renewable energy technologies are under development. Among the new and renewable energy sources, solar cells (Solar Cells or Photovoltaic Cells) are the core elements of photovoltaic power generation that convert sunlight directly into electricity, and are widely used for power supply from space to home. In the early days when solar cells were first made, they were mainly used for space use, but after two oil surges in the 1970s, they were attracting attention for their potential as ground power sources. It started to use for dragon. Recently, it is used in aviation, meteorology, and communication fields, and solar cars and solar air conditioners are also attracting attention. These solar cells mainly use silicon, but because they are manufactured by a semiconductor device manufacturing process, the manufacturing cost is high, and there is a difficulty in supplying silicon raw materials. Under these circumstances, organic-inorganic hybrid solar cells, which do not use any silicon materials, have begun to be studied in earnest, and low cost process is possible by printing method, and flexible solar cells regardless of shape It is possible to manufacture and is currently receiving a lot of attention.

Unlike silicon solar cells, organic-inorganic hybrid solar cells are composed of photosensitive dye molecules capable of absorbing visible light to generate electron-hole pairs, and transition metal oxides for transferring generated electrons. Is a photoelectrochemical solar cell. A representative example of the organic-inorganic hybrid solar cells known so far was published by Gratzel, Switzerland, in 1991. The solar cell by Gratzel et al. Is composed of a transparent electrode, a semiconductor layer made of nano-sized titanium dioxide coated with dye molecules, a counter electrode (platinum electrode) and an electrolyte filled therebetween. The battery has been attracting attention because it has a lower manufacturing cost per power than a conventional silicon battery, and thus can replace the existing solar cell.

In order to commercialize organic-inorganic hybrid solar cells, improvement of photoelectric conversion efficiency must be preceded, and various methods for improving the same have been attempted. There is a method of improving the photoelectric conversion efficiency by coating a metal hydrate or metal oxide-based material on the surface of the semiconductor compound constituting the semiconductor layer (Korean Patent No. 10-0643054), the process of coating the metal oxide particles on the surface of the semiconductor compound Has the problem of requiring extra equipment and time.

Provided are a solar cell having high photoelectric conversion efficiency and a method of manufacturing the same.

The solar cell according to an aspect of the present invention includes a first substrate, a first electrode formed on the first substrate, and a lower plate including a semiconductor layer formed on the first electrode and adsorbed metal carbonate, the second substrate, the A top plate comprising a second electrode formed on a second substrate and a counter electrode formed on the second electrode and opposing the semiconductor layer, a sealing member for sealing the bottom plate and the top plate, and sealed by the sealing member. It includes an electrolyte layer injected between the lower plate and the upper plate.

According to another aspect of the present invention, there is provided a method of manufacturing a solar cell, including forming a lower plate including a first substrate, a first electrode formed on the first substrate, and a semiconductor layer formed on the first electrode, and forming a metal on the lower plate. And depositing the metal carbonate in the semiconductor layer by depositing the solution including carbonate.

Hereinafter, with reference to the accompanying drawings will be described in detail a solar cell and its manufacturing method according to an embodiment of the present invention. Like reference numerals refer to like elements throughout.

In the present specification, when a component is described as being formed on another component, the case where there is another component between the one component and the other component is not excluded. That is, some of the components may be formed in direct contact with other components, or another component may be interposed between the certain components and the other components.

1 is a cross-sectional view showing the structure of a solar cell 100 according to an embodiment of the present invention.

Referring to FIG. 1, the solar cell 100 includes a lower substrate 180 including a first substrate 112, a first electrode 122, a recombination blocking layer 132, a semiconductor layer 134, and a scattering layer 136. ), An upper plate 190 including an opposing electrode 142, a second electrode 124, and a second substrate 114, an electrolyte layer 162, and a sealing member 152.

The semiconductor layer 134 includes a nano-sized semiconductor compound in which dye molecules are adsorbed. The dye molecules of the semiconductor layer 134 absorb visible light to generate electron-hole pairs, and the semiconductor compound transfers the generated electrons. do. That is, the operating principle of the solar cell is as follows. The dyes excited by solar light inject electrons into the conduction band of the semiconductor compound. The injected electrons pass through the semiconductor compound to reach the first electrode 122 and are transferred to the external circuit. According to a contact state between the nano-sized semiconductor compound constituting the semiconductor layer 134 and the first electrode 122, electrons that cannot be transferred to an external circuit are generated. Some of the electrons transferred from the semiconductor compound to the vicinity of the first electrode 122 disappear back into the electrolyte through a portion where the first electrode 122 and the semiconductor compound are not in contact with each other and are exposed to the electrolyte solution. This phenomenon is called recombination, which causes a decrease in photoelectric conversion efficiency. In order to minimize the recombination phenomenon, as shown in FIG. 1, the recombination blocking layer 132 may be formed. External sunlight reaches the semiconductor layer 134 through the first substrate 112, the first electrode 122, and the recombination blocking layer 132, and the sunlight is emitted by the dye present in the semiconductor layer 134. Is absorbed. In the solar light received from the outside, light that passes through the semiconductor layer 134 without being completely absorbed by the semiconductor layer 134 is present, which causes a decrease in photoelectric conversion efficiency. As such, in order to block light passing through the semiconductor layer 134, the scattering layer 136 is formed to induce light scattering, and the scattered light is absorbed by the semiconductor layer 134 again. The dye that absorbs sunlight forms electron-hole pairs, and electrons are transferred to the first electrode 122 through the semiconductor compound. On the other hand, the hole is transferred to the counter electrode 142 through the redox reaction of the electrolyte, and is transferred to the external circuit through the second electrode 124.

Method for manufacturing a solar cell 100 according to an embodiment of the present invention, the first substrate 112, the first electrode 122 formed on the first substrate 112 and the first electrode 122 on the. Forming a lower plate 180 including a semiconductor layer 134 and a scattering layer 136 formed thereon, and depositing the lower plate 180 in a solution containing metal carbonate to the metal layer 134. Adsorbing carbonates.

Glass, plastic, metal foil, or the like may be used as the first substrate 112. The first electrode 122 is formed on the first substrate 112. As the first electrode 122, F-doped tin oxide (FTO), indium tin oxide (ITO), indium zinc oxide (IZO), ZnO-Ga ₂ O ₃ , ZnO-Al ₂ O ₃ , SnO ₂ -Sb ₂ Transparent electrodes such as O ₃ can be used. The first substrate 112 on which the first electrode 122 is formed is dipped in acetone, ethanol, distilled water, or a mixed solution thereof, and then ultrasonic cleaning is performed.

After the cleaned first substrate 112 is deposited in a precursor solution (eg TiCl ₄ ), the recombination blocking layer 132 may be formed by heat treatment (50 to 80 ° C.) for at least 30 minutes in air or in an oxygen atmosphere. . The temperature of the precursor solution may be about 70 ° C., and the deposition is performed for about 30 minutes. The recombination blocking layer 132 is a recombination in which some of the electrons transferred to the first electrode 122 are disappeared back into the electrolyte through a portion where the first electrode 122 is not in contact with the semiconductor compound and is exposed to the electrolyte solution. The layer is selectively formed to minimize the phenomenon.

After the recombination blocking layer 132 is formed, a paste containing a small particle semiconductor compound having an average particle diameter of 20 nm is coated on the recombination blocking layer 132 to form a semiconductor layer 134.

On the semiconductor layer 134, a paste containing an allele semiconductor compound having an average particle diameter of about 300 to 400 nm is coated, and the scattering layer is formed by heat treatment (450 to 550 ° C.) for about 30 to 60 minutes in an air or oxygen atmosphere. 136 is formed. The scattering layer 136 may be formed to a thickness of about 5 ㎛.

The semiconductor compound is a material that can safely transfer electrons transferred from the dye to the first electrode 122, and may use metal oxides such as TiO ₂ , SnO ₂ , ZnO, WO ₃ , Nb ₂ O ₅ , TiSrO _3, and the like. have. The semiconductor compound may be configured through doctor blade coating, screen printing, flexography, gravure printing, or the like. As a result, a lower plate 180 including the first substrate 112, the first electrode 122, the recombination blocking layer 132, the semiconductor layer 134, and the scattering layer 136 is formed. Among these, since the recombination blocking layer 132 and the scattering layer 136 are formed for the purpose of improving the photoelectric conversion efficiency of the solar cell, one or two layers of the recombination blocking layer 132 or the scattering layer 136. Without all, there is no problem with the operation of the solar cell.

The lower plate 180 on which the semiconductor layer 134 is formed is deposited in a solution containing metal carbonate. Metal carbonates include CaCO ₃ , BaCO ₃ , Na ₂ CO ₃ And K ₂ CO ₃ can be used. The solution containing the metal carbonate is a solution in which the metal carbonate is dissolved in a solvent, and water, an alcohol solvent, or a mixture thereof can be used as the solvent. Ethanol, isopropyl alcohol, etc. can be used as alcohol solvent. Deposition is carried out for 1 to 20 minutes. After immersion, it is washed with distilled water and alcohol solvent and dried for 10 to 20 minutes at 60 to 70 ° C., so that the metal carbonate is adsorbed on the surface of the semiconductor compound included in the semiconductor layer 134 and the scattering layer 136. .

2 is an enlarged view of the semiconductor layer 134 and the scattering layer 136 of the solar cell 100 according to an embodiment of the present invention.

Referring to FIG. 2, the metal carbonate 200 is adsorbed to the semiconductor compound included in the semiconductor layer 134 and the scattering layer 136.

A dye is introduced into the semiconductor layer 134 on which the metal carbonate is adsorbed. The sunlight is absorbed by the dye included in the semiconductor layer 134, and as the sunlight is absorbed, the dye electrons transfer from the ground state to the excited state to form an electron-hole pair. Electrons in the excited state are injected into the conduction band of the semiconductor compound and then move to the electrodes to generate electromotive force. Any dye can be used without limitation as long as it is generally used in the field of solar cells. Ruthenium complex [N719 dye; bis (tetrabutylammonium) -cis- (dithiocyanato) -N, N'-bis (4-carboxylato-4'-carboxylic acid-2,2'-bipyridine) ruthenium (II), N3 dye; cis-bis (4,4-dicarboxy-2,2-bipyridine) dithiocyanato ruthenium (II), Black dye; triisothiocyanato- (2,2 ': 6,6 "-terpyridyl-4,4', 4" -tricarboxylato) ruthenium (II) tris (tetra-butylammonium)] is preferred. However, it is not particularly limited as long as it has a charge separation function and exhibits an insensitive action. Basic dyes such as nosapranin, carbiblue, thiosine, methylene blue, porphyrin compounds such as chlorophyll, zinc porphyrin, magnesium porphyrin, other azo dyes, phthalocyanine compounds, complexes such as Ru trisbipyridyl, and anthraquinones A dye, a polycyclic quinone dye, an organic dye, etc. can be used, These can be used individually or in mixture of 2 or more types.

After dissolving the dye in a solvent, the lower plate 180 on which the semiconductor layer 134 is formed is dipped in a dye solution for 1 to 72 hours. As the solvent, tert-butyl alcohol, acetonitrile or a mixture thereof may be used. The dye is introduced into the semiconductor compound by dipping the lower plate 180 in the dye solution. In this case, a dye may be introduced to the surface of the semiconductor compound included in the scattering layer 136. Since dye is difficult to penetrate into the semiconductor compound included in the recombination blocking layer 132, only a very small amount of dye is introduced or hardly occurs. After the introduction of the dye is completed, it is washed with a solvent of alcohols and dried.

The upper plate 190 includes a second substrate 114, a second electrode 124, and a counter electrode 142. Glass, plastic, metal foil, or the like may be used as the second substrate 114, and F-doped tin oxide (FTO), indium tin oxide (ITO), or indium zinc oxide (IZO) may be used as the second electrode 124. , ZnO-Ga ₂ O ₃ , ZnO-Al ₂ O ₃ , SnO ₂ -Sb ₂ O _3, etc. may be used. As the counter electrode 142, a conductive material may be used. Specifically, platinum, gold, carbon, or the like may be used. The second electrode 124 is formed on the second substrate 114, and the counter electrode 142 is formed on the second electrode 124. The counter electrode 142 may be formed by vacuum deposition using a spurt or the like, or may be formed by coating and firing a conductive electrode precursor in a paste state on the second electrode 124 formed on the second substrate 114. The counter electrode 142 of the upper plate 190 faces the semiconductor layer 134 of the lower plate 180.

The upper plate 190 and the lower plate 180 are sealed with a sealing member 152 such as a partition wall, and an electrolyte is injected between the upper plate 190 and the lower plate 180 sealed by the sealing member 152. 162 is formed. In the case of sealing using a partition wall, a partition wall having a thickness of about 40 μm is formed, and the lower plate and the upper plate are brought into close contact with each other at about 1 to 3 atmospheres on a heating plate of 100 to 140 ° C. As the partition wall, a polymer material (eg, a sealing material, manufactured by Solaronix), a sulfin (Surlyn, manufactured by Dupont), an epoxy resin, or an ultraviolet (UV) curing agent may be used.

After sealing, an electrolyte solution is filled in the space between the upper plate 190 and the lower plate 180 through a fine hole formed on the surface of the counter electrode and the hole is sealed to manufacture a solar cell. As an electrolyte, 0.8M 1,2-dimethyl-3-octyl-imidazolium iodide (1,2-dimethyl-3-octyl-imimdazolium iodide), 40 mM I ₂ (iodine) 3-methoxy propionitrile (3-methoxypropionitile) was dissolved in I ^{3 -} / I ^- If and the like, a hole conduction function of the organic semiconductor materials (conductive polymers), which can be used without any restriction would.

In the solar cell 100 according to an embodiment of the present invention, a first substrate 112, a first electrode 122 formed on the first substrate 112, and a metal formed on the first electrode 122 are formed. The lower plate 180 including the semiconductor layer 134 and the scattering layer 136 to which the carbonate is adsorbed, the second substrate 114, the second electrode 124 formed on the second substrate 114, and the second An upper plate 190 formed on an electrode 124 and including a counter electrode 142 facing the semiconductor layer 134, a sealing member 152 for sealing the lower plate 180 and the upper plate 190; The electrolyte layer 162 is injected between the lower plate 180 and the upper plate 190 sealed by the sealing member 152.

2 is an enlarged view of the semiconductor layer 134 and the scattering layer 136 of the solar cell 100 according to an embodiment of the present invention.

Referring back to FIG. 2, the metal carbonate 200 is adsorbed to the semiconductor compound included in the semiconductor layer 134 and the scattering layer 136. In addition, a coating of a metal oxide or a metal hydrate may be formed on the surface of the semiconductor compound.

Hereinafter, the present invention will be described in more detail with reference to the following Examples, but the present invention is not limited to the following Examples.

Comparative example  One

After washing the FTO substrate, it was immersed in 40 mM TiCl ₄ aqueous solution (70 ° C.) for 30 minutes to form a recombination prevention layer. TiO ₂ Paste (Solaronix, TiO ₂ Particle diameter: 20 nm) was coated by a doctor blade method to form a semiconductor layer, and then a scattering layer was formed using a paste containing TiO ₂ having an average particle diameter of 400 nm. The FTO board | substrate which passed the above process was baked for 60 minutes at 500 *. The calcined substrate was immersed in a dye solution (solution dissolved in a mixed solution of acetonitrile and t-butyl alcohol at a concentration of 0.5 mM in Solaronix) for 24 hours to allow sufficient dye penetration into the semiconductor layer. Platinum paste (Pt paste) was coated on the cleaned FTO substrate and then fired at 400 ° C. for 30 minutes to form a counter electrode, thereby preparing a top plate. Two holes were predrilled for electrolyte injection prior to coating the platinum paste. The lower plate and the upper plate to which the dye was introduced were disposed to face each other, and a sealing material (Sealing material, manufactured by Solaronix, approximately 60 μm in thickness) was installed therebetween. The upper plate and the lower plate were brought into close contact with each other by applying pressure from the upper side in the state of raising them on a heating plate at 120 ° C. By the heat and the pressure, the partition material is strongly attached to the surface of the upper plate and the lower plate. Subsequently, an electrolyte was filled between the upper and lower plates through holes previously formed in the upper plate. It was used as the redox couple (redox couple, Solaronix Co., Ltd.) ^- in this case the electrolyte is I ^- / I _3. After filling the electrolyte solution, a hole formed in the upper plate was sealed to manufacture a solar cell. The photoelectric conversion efficiency of the manufactured solar cell was measured using a solar simulator and IV measurement equipment. After irradiating the solar cell with AM 1.5 light (100 mW / cm ² ), an IV curve was obtained and the measurement results are shown in FIG. 3.

3 is a graph showing the current-voltage characteristics of the solar cell according to Comparative Example 1. FIG.

Referring to Figure 3, V _OC (Open circuit voltage) is 0.58V, J _SC (short circuit current density) was 20.76 mA / cm ^2, fill factor (Fill Factor) is 0.57, the photoelectric conversion efficiency was 6.8% .

Example  One

The solar cell of Comparative Example 1 was prepared in the same manner as in Comparative Example 1 except that the lower plate was immersed in 0.05 M calcium carbonate (CaCO ₃ ) deposit for 10 minutes before firing and depositing the dye on the lower plate. The battery was prepared.

100 mL of distilled water was put into a glass beaker, and calcium carbonate (CaCO ₃ ) was dissolved therein to prepare a 0.05 M calcium carbonate solution as a deposition liquid. Photoelectric conversion efficiency was measured in the same manner as in Comparative Example 1. V _OC was 0.69 V , J _SC was 19.23 mA / cm ² , Fill Factor was 0.66, and photoelectric conversion efficiency was 8.7%.

Example  2

A solar cell was manufactured in the same manner as in Example 1, except that BaCO ₃ was used instead of CaCO ₃ as the metal carbonate. As a result of measuring the photoelectric conversion efficiency in the same manner as in Comparative Example 1, V _OC was 0.68V, J _SC was 19.33 mA / cm ² , Fill Factor was 0.66, and photoelectric conversion efficiency was 8.6%.

Example  3

A solar cell was manufactured in the same manner as in Example 1, except that Na ₂ CO ₃ was used instead of CaCO ₃ as the metal carbonate. As a result of measuring photoelectric conversion efficiency in the same manner as in Comparative Example 1, V _OC was 0.63V, J _SC was 23.31 mA / cm ² , Fill Factor was 0.56, and photoelectric conversion efficiency was 8.3%.

Example  4

A solar cell was manufactured in the same manner as in Example 1, except that K ₂ CO ₃ was used instead of CaCO ₃ as the metal carbonate. Photoelectric conversion efficiency was measured in the same manner as in Comparative Example 1, and the measurement results are shown in FIG. 4.

4 is a graph showing the current-voltage characteristics of the solar cell according to Example 4. FIG. Referring to FIG. 4, V _OC was 0.77 V , J _SC was 17.92 mA / cm ² , Fill Factor was 0.61, and photoelectric conversion efficiency was 8.4%.

From the above embodiment, it can be seen that the photovoltaic conversion efficiency of the solar cell including the semiconductor layer on which the metal carbonate is adsorbed is excellent.

1 is a cross-sectional view showing the structure of a solar cell according to an embodiment of the present invention.

2 is an enlarged view of a semiconductor layer and a scattering layer of a solar cell according to an embodiment of the present invention.

3 is a graph showing the current-voltage characteristics of the solar cell according to Comparative Example 1. FIG.

4 is a graph showing the current-voltage characteristics of the solar cell according to Example 4. FIG.

Claims (11)

A lower plate including a first substrate, a first electrode formed on the first substrate, and a semiconductor layer formed on the first electrode and adsorbed with metal carbonate; A top plate including a second substrate, a second electrode formed on the second substrate, and a counter electrode formed on the second electrode and opposing the semiconductor layer; A sealing member for sealing the lower plate and the upper plate; And A solar cell comprising an electrolyte layer injected between the lower plate and the upper plate sealed by the sealing member. The method of claim 1, The solar cell further comprises a recombination blocking layer on the lower plate. The method according to claim 1 or 2, The solar cell further comprises a scattering layer on the lower plate. The method of claim 1, The metal carbonate is a solar cell comprising at least one selected from the group consisting of CaCO ₃ , BaCO ₃ , Na ₂ CO ₃ and K ₂ CO ₃ . The method of claim 1, The semiconductor layer comprises at least one semiconductor compound selected from the group consisting of TiO ₂ , SnO ₂ , ZnO, WO ₃ , Nb ₂ O ₅ and TiSrO ₃ . The method of claim 1, The semiconductor layer is a solar cell comprising a semiconductor compound coated with a metal oxide or metal hydrate. The method of claim 1, The metal carbonate is adsorbed by a semiconductor compound contained in the semiconductor layer. Forming a lower plate including a first substrate, a first electrode formed on the first substrate, and a semiconductor layer formed on the first electrode; And And depositing the lower plate in a solution containing metal carbonate to adsorb the metal carbonate to the semiconductor layer. The method of claim 8, The method of manufacturing a solar cell further comprises the step of introducing a dye into the metal carbonate adsorbed semiconductor layer. The method of claim 8, The solution containing the metal carbonate is a solution in which the metal carbonate is dissolved in a solvent, wherein the solvent is water, an alcohol solvent or a mixture thereof. The method of claim 8, The lower plate is immersed in a solution containing a metal carbonate for 1 to 20 minutes manufacturing method of a solar cell.

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