WO2013100284A1

WO2013100284A1 - Method for manufacturing organic solar cell and the organic solar cell manufacturing by using the same

Info

Publication number: WO2013100284A1
Application number: PCT/KR2012/004550
Authority: WO
Inventors: Jung Seok Han; Chul Oh; Jin Ha Kal; Kwang Su Kim
Original assignee: Kolon Industries, Inc.
Priority date: 2011-12-28
Filing date: 2012-06-08
Publication date: 2013-07-04
Also published as: KR20130076392A

Abstract

Disclosed are a method for producing an organic solar cell, including a step of forming a thin film layer by immersing a base material film into a coating solution while conveying the base material by a roll-to-roll method; and an organic solar cell produced by the method. The method for producing an organic solar cell enables continuously applying thin film layers each having a thickness of 10 nm to 1,000 nm, so that the process cost can be reduced. The method of the present invention can also reduce the thickness deviation of the thin film layer thus produced, and can therefore enhance the efficiency of the organic solar cell.

Description

METHOD FOR MANUFACTURING ORGANIC SOLAR CELL AND THE ORGANIC SOLAR CELL MANUFACTURING BY USING THE SAME

The present invention relates to a method for producing an organic solar cell, and an organic solar cell produced by using the method, and more particularly, to a method for producing an organic solar cell, in which since thin film layers can be continuously applied, the process cost can be reduced, and the thickness deviation of the thin film layers thus produced can be reduced, and to an organic solar cell produced by the method.

An organic solar cell is a solar cell having a structure which utilizes organic semiconductor materials, including conjugated polymers such as poly(para-phenylene vinylene) (PPV) in which double bonds are alternately disposed, photosensitive low molecular weight compounds such as CuPc, perylene and pentacene, and (6,6)-phenyl-C₆₁-butyric acid methyl ester (PCBM). The organic semiconductor materials can be structurally designed and synthesized into a wide variety, so that organic solar cells have a potential for limitless development.

An organic solar cell such as described above basically has a thin-film type structure, and mainly uses indium tin oxide (ITO), which is a transparent electrode, as an anode and a metal electrode such as aluminum (Al) which has a low work function, as a cathode. The photoactive layer has a thickness of about 100 nm and has a bulk heterojunction structure in which a hole acceptor and an electron acceptor exist in mixture.

As the hole acceptor, a conjugated polymer having conductivity, such as PPV, is used, and a fullerene is used as the electron acceptor. At this time, in order to collect, without loss, electrons that have been produced by light at an aluminum electrode through the fullerene, the fullerene should be sufficiently mixed into the conjugated polymer. Therefore, a fullerene derivative such as PCBM can be used so that the fullerene may be thoroughly mixed with the conjugated polymer.

When the conjugated polymer absorbs light, the conjugated polymer produces electron-hole pairs (excitons), and the electrons and holes thus produced are collected respectively at the anode and the cathode via the fullerene and the conjugated polymer, respectively.

Organic solar cells such as described above can be produced in large quantities due to their easy processability and low cost, and can be manufactured into thin films by a roll-to-roll process. Therefore, the organic solar cells described above have an advantage that flexible, large-sized electronic elements can be produced.

However, despite the technical and economical advantages mentioned above, there are still difficulties in putting organic solar cells into practical use because of their low efficiency. Therefore, studies to improve efficiency are being actively carried out in the field of organic solar cells. Studies concerning the efficiency of organic solar cells that have been conducted hitherto are focused on the selection of raw materials or the manufacturing processes for the photoactive layer, the electron transport layer and the hole transport layer so as to effectively utilize absorbed light, as well as the morphology, structure and increased crystallinity of the organic thin films for overcoming low charge mobility.

[CITATION LIST]

[Patent Documents]

Patent Document 1: Korean Patent No. 1023021 (registered on March 10, 2011)

Patent Document 2: Korean Patent No. 1023020 (registered on March 10, 2011)

Patent Document 3: Korean Patent No. 1066019 (registered on September 14, 2011)

An object of the present invention is to provide a method for producing an organic solar cell, in which since thin film layers each having a thickness of 10 nm to 1000 nm can be continuously applied, the process cost can be reduced, and the thickness deviation of the thin film layers thus produced can be reduced, so that the efficiency of organic solar cells can be enhanced.

Another object of the present invention is to provide an organic solar cell produced by the method for producing an organic solar cell described above.

The method for producing an organic solar cell according to an exemplary embodiment of the present invention includes a step of immersing a base material film in a coating solution while conveying the base material film by a roll-to-roll method, and thereby forming a thin film layer.

The angle formed by the thin film layer-formed surface of the base material film and the surface of the coating solution when the base material film is submerged into the coating solution, may be 0° to 180°, and the angle formed by the thin film layer-formed surface of the base material film and the surface of the coating solution when the base material film is removed from the coating solution, may be 0° to 180°.

The time taken to immerse the base material film in the coating solution may be 1 minute to 20 minutes.

The base material film may be conveyed by a roll-to-roll method at a speed of 0.01 m/min to 20 m/min.

The concentration of the coating solution may be 0.01 mg/ml to 1,000 mg/ml.

The thickness of the thin film layer may be 10 nm to 1,000 nm.

The method for producing an organic solar cell may further include a step of drying the thin film thus formed at 50℃ to 400℃ for 1 minute to 30 minutes.

The step of forming a thin film layer may be a step of forming a transparent conductive thin film layer by immersing the base material film in a coating solution containing a transparent conductive substance and a solvent, while conveying the base material film by a roll-to-roll method.

The solvent may be any one selected from the group consisting of water, ethanol, methanol, propanol, isopropanol, butanol, acetone, pentane, toluene, benzene, diethyl ether, methyl butyl ether, N-methylpyrrolidone (NMP), tetrahydrofuran (THF), dimethylformamide (DMF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), carbon tetrachloride, dichloromethane, dichloroethane, trichloroethylene, chloroform, chlorobenzene, dichlorobenzene, trichlorobenzene, cyclohexane, cyclopentanone, cyclohexanone, dioxane, terpineol, methyl ethyl ketone, and combinations thereof.

The transparent conductive substance may be any one selected from the group consisting of tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), ZnO-Ga₂O₃, ZnO-Al₂O₃, SnO₂-Sb₂O₃, conductive polymers, graphene, graphene oxide, carbon nanotubes, and combinations thereof.

The step of forming a thin film layer may be a step of forming a metal oxide thin film layer by immersing the base material film into a coating solution containing a metal oxide precursor and a solvent while conveying the base material film by a roll-to-roll method.

The average particle size of the metal oxide may be 10 nm or less.

The metal oxide precursor may be any one selected from the group consisting of a metal chloride, a metal acetate, a metal citrate, a metal (meth)acrylate, a metal bromide, a metal cyanide, a metal phosphate, a metal sulfate, a metal sulfide, and combinations thereof.

In the metal oxide precursor, the metal may be any one selected from the group consisting of Ti, Zn, Si, Mn, Sr, In, Ba, K, Nb, Fe, Ta, W, Sa, Bi, Ni, Cu, Mo, Ce, Pt, Ag, Rh, and combinations thereof.

The step of forming a thin film layer may be a step of forming a photoactive layer by immersing the base material film into a coating solution containing a hole acceptor, an electron acceptor, and a solvent, while conveying the base material film by a roll-to-roll method.

The hole acceptor may be any one selected from the group consisting of poly-3-hexylthiophene [P3HT], poly-3-octylthiophene [P3OT], poly(p-phenylene vinylene) [PPV], poly(9,9'-dioctylfluorene), poly(2-methoxy-5-(2-ethylehexyloxy)-1,4-phenylenevinylene) [MEH-PPV], poly(2-methyl-5-(3',7'-dimethyloctyloxy))-1,4-phenylenevinylene [MDMOPPV], precursors thereof, and combinations thereof.

The electron acceptor may be any one selected from the group consisting of (6,6)-phenyl-C₆₁-butyric acid methyl ester [PCBM], (6,6)-phenyl-C₇₁-butyric acid methyl ester [C70-PCBM], (6,6)-thienyl-C₆₁-butyric acid methyl ester [ThCBM], carbon nanotubes, precursors thereof, and combinations thereof.

The step of forming a thin film layer may be a step of forming a hole transport layer by immersing the base material film into a coating solution containing a hole transporting substance and a solvent, while conveying the base material film by a roll-to-roll method.

The hole transporting substance may be any one selected from the group consisting of poly(3,4-ethylenedioxythiophene) (PEDOT), poly(styrene sulfonate) (PSS), polyaniline, phthalocyanine, pentacene, polydiphenylacetylene, poly(t-butyl)diphenylacetylene, poly(trifluoromethyl)diphenylacetylene, copper phthalocyanine (Cu-PC), poly(bistrifluoromethyl)acetylene, polybis(t-butyldiphenyl)acetylene, poly(trimethylsilyl)diphenylacetylene, poly(carbazole)diphenylacetylene, polydiacetylene, polyphenylacetylene, polypyridineacetylene, polymethoxyphenylacetylene, polymethylphenylacetylene, poly(t-butyl)phenylacetylene, polynitrophenylacetylene, poly(trifluoromethyl)phenylacetylene, poly(trimethylsilyl)phenylacetylene, precursors thereof, and combinations thereof.

The step of forming a thin film layer may be a step of forming an electrode by immersing the base material film into a coating solution containing metal particles and a solvent, while conveying the base material film by a roll-to-roll method.

The metal particles may be any one selected from the group consisting of silver (Ag), copper (Cu), gold (Au), platinum (Pt), titanium (Ti), aluminum (Al), nickel (Ni), zirconium (Zr), iron (Fe), manganese (Mn), precursors thereof, and combinations thereof.

The solvent may be any one selected from the group consisting of ethanol, methanol, propanol, isopropanol, butanol, acetone, pentane, toluene, benzene, diethyl ether, methyl butyl ether, N-methylpyrrolidone (NMP), tetrahydrofuran (THF), dimethylformamide (DMF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), carbon tetrachloride, dichloromethane, dichloroethane, trichloroethylene, chloroform, chlorobenzene, dichlorobenzene, trichlorobenzene, cyclohexane, cyclopentanone, cyclohexanone, dioxane, terpineol, methyl ethyl ketone, and combinations thereof.

The organic solar cell according to another exemplary embodiment of the present invention is produced by the method for producing an organic solar cell.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings, so that those having ordinary skill in the art to which the present invention is pertained can easily carry out the invention. However, the present invention can be realized in various different forms, and is not limited to the Examples described herein.

FIG. 1 is a perspective view diagram illustrating the organic solar cell according to an exemplary embodiment of the present invention. The organic solar cell may be an inverted organic solar cell which includes a metal oxide thin film layer formed between an anode and a photoactive layer.

In FIG. 1, the organic solar cell (100) includes a cathode (160) and an anode (120) that are disposed to face each other, a photoactive layer (140) that is disposed between the cathode (160) and the anode (120) and contains a hole acceptor and an electron acceptor in mixture, and a metal oxide thin film layer (170) that is formed between the anode (120) and the photoactive layer (140).

The base material film (110) is not particularly limited as long as it has transparency, and a transparent inorganic base material film of quartz or glass, or any one transparent plastic base material film selected from the group consisting of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polystyrene (PS), polypropylene (PP), polyimide (PI), polyethylene sulfonate (PES), polyoxymethylene (POM), polyether ether ketone (PEEK), polyether sulfone (PES), and polyether imide (PEI) can be used. Particularly, as the transparent plastic base material film, a film which is flexible and has high chemical stability, mechanical strength and transparency can be preferably used.

The base material film (110) desirably has a transmittance of at least 70% or higher, and preferably 80% or higher, at a visible light wavelength of about 400 nm to 750 nm.

Since the anode (120) serves as a pathway through which the light that has passed through the base material film (110) is guided to reach the photoactive layer (140), it is preferable to use a substance having high transparency. Specific examples of anode-forming substances that form the anode (120) include transparent oxides selected from the group consisting of tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), ZnO-Ga₂O₃, ZnO-Al₂O₃, SnO₂-Sb₂O₃, and combinations thereof; organic transparent electrodes such as conductive polymers, a graphene thin film, a graphene oxide thin film, and a carbon nanotube thin film; and organic-inorganic coupled transparent electrodes such as a carbon nanotube thin film coupled with a metal.

The cathode (160) may contain any one selected from the group consisting of, specifically, silver (Ag), copper (Cu), gold (Au), platinum (Pt), titanium (Ti), aluminum (Al), nickel (Ni), zirconium (Zr), iron (Fe), manganese (Mn) and combinations thereof.

The photoactive layer (140) has a bulk heterojunction structure in which a hole acceptor and an electron acceptor are mixed. The hole acceptor is an organic semiconductor such as an electrically conductive polymer or an organic low molecular weight semiconductor substance. The electrically conductive polymer may be any one selected from the group consisting of polythiophene, polyphenylene vinylene, polyfluorene, polypyrrole, copolymers thereof, and combinations thereof, and the organic low molecular weight semiconductor substance may be any one selected from the group consisting of pentacene, anthracene, tetracene, perylene, oligothiophene, derivatives thereof, and combinations thereof.

Furthermore, the hole acceptor may be preferably any one selected from the group consisting of poly-3-hexylthiophene [P3HT], poly-3-octylthiophene [P3OT], poly(p-phenylene vinylene) [PPV], poly(9,9'-dioctylfluorene)], poly(2-methoxy,5-(2-ethyle-hexyloxy)-1,4-phenylenevinylene) [MEH-PPV], poly(2-methyl,5-(3',7'-dimethyloctyloxy))-1,4-phenylenevinylene [MDMOPPV], and combinations thereof.

The electron acceptor may be nanoparticles of any one kind selected from the group selected from the group consisting of fullerene (C₆₀), fullerene derivatives, CdS, CdSe, CdTe, ZnSe, and combinations thereof. The electron acceptor is preferably any one selected from the group consisting of (6,6)-phenyl-C₆₁-butyric acid methyl ester [PCBM], (6,6)-phenyl-C₇₁-butyric acid methyl ester [C70-PCBM], (6,6)-thienyl-C₆₁-butyric acid methyl ester [ThCBM], carbon nanotubes, and combinations thereof.

The photoactive layer (140) is preferably formed from a mixture of P3HT as the hole acceptor and PCBM as the electron acceptor, and at this time, the mixing weight ratio of P3HT and PCBM may be 1:0.1 to 1:2.

The organic solar cell (100) may further include a hole transport layer (150) between the cathode (160) and the photoactive layer (140). The hole transport layer (150) is a layer which helps the holes generated at the photoactive layer (140) to move to the cathode (160). The hole transport layer (150) may contain any one hole transporting substance selected from the group consisting of poly(3,4-ethylenedioxythiophene) (PEDOT), poly(styrene sulfonate) (PSS), polyaniline, phthalocyanine, pentacene, polydiphenylacetylene, poly(t-butyl)diphenylacetylene, poly(trifluoromethyl)diphenylacetylene, copper phthalocyanine (Cu-PC), poly(bistrifluoromethyl)acetylene, polybis(t-butyldiphenyl)acetylene, poly(trimethylsilyl)diphenylacetylene, poly(carbazole)diphenylacetylene, polydiacetylene, polyphenylacetylene, polypyridineacetylene, polymethoxyphenylacetylene, polymethylphenylacetylene, poly(t-butyl)phenylacetylene, polynitrophenylacetylene, poly(trifluoromethyl)phenylacetylene, poly(trimethylsilyl)phenylacetylene, derivatives thereof, and combinations thereof, and preferably, a mixture of PEDOT and PSS can be used.

On the other hand, the organic solar cell (100) includes a metal oxide thin film (170) between the anode (120) and the photoactive layer (140). The metal oxide thin film layer (170) functions as an auxiliary electrode and increases the speed of movement of electrons, thereby enabling the operation of the organic solar cell (100). The metal oxide thin film layer also blocks oxygen and moisture penetrating from the outside, and prevents the polymer contained in the photoactive layer (140) from deteriorating under the action of oxygen and moisture, thereby enhancing the service life of the organic solar cell (100).

The metal oxide thin film layer (170) may have a thickness of 10 nm to 500 nm, preferably 20 nm to 300 nm, and more preferably 20 nm to 200 nm. When the thickness of the metal oxide thin film layer (170) is in the range described above, the speed of movement of electrons can be enhanced, and oxygen and moisture can be effectively prevented from penetrating from the outside and affecting the photoactive layer and the hole transport layer.

The metal oxide of the metal oxide thin film layer (170) has an average particle size of 10 nm or less, preferably 1 nm to 8 nm, and more preferably 3 nm to 7 nm.

The metal oxide may be the oxide of any one metal selected from the group consisting of Ti, Zn, Si, Mn, Sr, In, Ba, K, Nb, Fe, Ta, W, Sa, Bi, Ni, Cu, Mo, Ce, Pt, Ag, Rh, and combinations thereof, and the metal oxide is preferably ZnO. ZnO has a wide band gap and has semiconductive properties, so that when used together with the anode (120), ZnO can further enhance the movement of electrons.

FIG. 2 is a diagram schematically illustrating the method for producing an organic solar cell according to another exemplary embodiment of the present invention. Hereinafter, the method for producing an organic solar cell will be described with reference to FIG. 2.

In FIG. 2, the method for producing the organic solar cell (100) includes a step of forming a thin film layer by immersing a base material film (110) while conveying the base material film by a roll-to-roll method. The thin film layer may be any one selected from the group consisting of a transparent conductive thin film layer, a metal oxide thin film layer, a photoactive layer, a hole transport layer, an electrode, and combinations thereof.

When the base material film (110) is submerged into the coating solution, the angle formed by the thin film layer-formed surface of the base material film (110) and the surface of the coating solution may be 0° to 180°, and preferably 30° to 150°. Furthermore, when the base material film (110) is removed from the coating solution, the angle formed by the thin film layer-formed surface of the base material film (110) and the surface of the coating solution may be 0° to 180°, and preferably 30° to 150°. The angle formed by the thin film layer-formed surface of the base material film (110) and the surface of the coating solution may be optimized in accordance with the type and surface characteristics of the base material film, and the configuration of the roll-to-roll apparatus.

The time for immersing the base material film (110) in the coating solution may be 1 minute to 20 minutes, and preferably 1 minute to 10 minutes. The immersion time can be optimized in accordance with the printing speed of the roll-to-roll apparatus, and the size of the solution bath containing the coating solution.

The speed by which the base material film (110) is conveyed by the roll-to-roll method may be 0.01 m/min to 20 m/min, and preferably 0.1 m/min to 5 m/min. The conveying speed can be optimized in accordance with the coating and drying speed of the thin film layer using the roll-to-roll apparatus.

The concentration of the coating solution may be 0.01 mg/ml to 1000 mg/ml, and preferably 10 mg/ml to 300 mg/ml. If the concentration of the coating solution is less than 0.01 mg/ml, the thin film layer may not be formed by the method of immersing the base material film while conveying the base material film by a roll-to-roll method. If the concentration is greater than 1,000 mg/ml, the thin film layer is formed, but it may be difficult to control the uniformity and thickness of the thin film.

The thin film layer may have a thickness of 10 nm to 1000 nm, preferably 20 nm to 500 nm, and more preferably 20 nm to 300 nm. When the thickness of the thin film layer is in the range described above, the efficiency of the organic solar cell thus produced is most excellent.

The step of forming a thin film layer may be a step of forming a transparent conductive thin film layer (121) by immersing the base material film (110) in a coating solution containing a transparent conductive substance and a solvent, while conveying the base material film by a roll-to-roll method.

The transparent conductive substance may be a transparent oxide selected from the group consisting of tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), ZnO-Ga₂O₃, ZnO-Al₂O₃, SnO₂-Sb₂O₃, and combinations thereof; an organic transparent electrode such as a conductive polymer, a graphene thin film, a graphene oxide thin film, or a carbon nanotube thin film; or an organic-inorganic coupled transparent electrode such as a carbon nanotube thin film coupled with a metal, but the present invention is not intended to be limited thereto.

The coating solution can be produced by dispersing the transparent conductive substance in the solvent described above, or by adding and mixing a precursor of the transparent conductive substance in the solvent.

Any solvent can be used as long as it can dissolve the transparent conductive substance, and preferably, any one selected from the group consisting of an aqueous solution such as water; alcohols such as ethanol, methanol, propanol, isopropanol, and butanol; organic solvents such as acetone, pentane, toluene, benzene, diethyl ether, methyl butyl ether, N-methylpyrrolidone, tetrahydrofuran (THF), dimethylformamide (DMF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), carbon tetrachloride, dichloromethane, dichloroethane, trichloroethylene, chloroform, chlorobenzene, dichlorobenzene, trichlorobenzene, cyclohexane, cyclopentanone, cyclohexanone, dioxane, terpineol, and methyl ether ketone; and combinations thereof, can be used.

However, the transparent conductive thin film layer (121) can be produced not only by the method described above, but can also be produced by screen printing an etch resist while conveying the base material (110) by a roll-to-roll method, UV-curing the resist, forming a pattern by etching and stripping, washing the pattern with demineralized water, and drying the pattern (STEP 1). The etching solution used for etching may be an aqueous solution of copper chloride, and sodium hydroxide may be used for stripping.

The step of forming a thin film layer may be a step of immersing the base material film (110) in a coating solution (171) containing a metal oxide precursor and a solvent, while conveying the base material film by a roll-to-roll method, and thereby forming a metal oxide thin film layer (STEP 2). That is, while the base material film (110) on which the transparent conductive thin film layer (121) has been formed is conveyed by a roll-to-roll method, the base material film is immersed in a coating solution (171) containing a metal oxide precursor and a solvent, and thereby the metal oxide thin film layer (170) is formed.

The coating solution (171) can be prepared by dispersing metal oxide nanoparticles that have been produced by using the metal oxide precursor in the solvent, or by adding and mixing the metal oxide precursor in the solvent.

Any solvent can be used as long as it can dissolve the metal oxide precursor, and preferably, any one selected from the group consisting of alcohols such as ethanol, methanol, propanol, isopropanol, and butanol; organic solvents such as acetone, pentane, toluene, benzene, diethyl ether, methyl butyl ether, N-methylpyrrolidone (NMP), tetrahydrofuran (THF), dimethylformamide (DMF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), carbon tetrachloride, dichloromethane, dichloroethane, trichloroethylene, chloroform, chlorobenzene, dichlorobenzene, trichlorobenzene, cyclohexane, cyclopentanone, cyclohexanone, dioxane, terpineol, and methyl ethyl ketone; and combinations thereof, can be used.

The metal oxide precursor may be any one selected from the group consisting of a metal chloride, a metal acetate, a metal citrate, a metal (meth)acrylate, a metal bromide, a metal cyanide, a metal phosphate, a metal sulfate, a metal sulfide, and combinations thereof, and the metal may be any one selected from the group consisting of Ti, Zn, Si, Mn, Sr, In, Ba, K, Nb, Fe, Ta, W, Sa, Bi, Ni, Cu, Mo, Ce, Pt, Ag, Rh, and combinations thereof. The metal oxide precursor and the metal can be appropriately selected depending on what substance will be used to form the metal oxide thin film in the organic solar cell (100), and preferably, zinc chloride or zinc acetate can be used.

The concentration of the coating solution (171) may be 0.01 mg/ml to 1,000 mg/ml, and preferably 10 mg/ml to 300 mg/ml. If the concentration of the coating solution is less than 0.01 mg/ml, a nano thin film of the metal oxide may not be formed, and if the concentration is greater than 1,000 mg/ml, a nano thin film of the metal oxide is formed, but it may be difficult to control the uniformity and thickness of the thin film.

The metal oxide thin film layer (170) may have a thickness of 10 nm to 500 nm, preferably 20 nm to 300 nm, and more preferably 20 nm to 200 nm. When the thickness of the metal oxide thin film layer (170) is in the range described above, oxygen and moisture can be effectively prevented from penetrating from the outside, while the speed of movement of electrons is enhanced.

After the metal oxide dispersed in the solvent is applied on the anode (120), the metal oxide thin film layer (170) can be selectively dried. The drying may be carried out at a temperature of 50℃ to 400℃, and preferably 70℃ to 200℃, for 1 minute to 300 minutes, through hot air drying, NIR drying, or UV drying. When the drying conditions described above are used, the metal oxide nano thin film layer (170) can secure a performance sufficient to be applied to the organic solar cell (100).

Next, while the base material film (110) on which the metal oxide thin film layer (170) has been formed is moved by a roll-to-roll method, the photoactive layer (140) is formed on the metal oxide thin film layer (170) (STEP 3). The photoactive layer (140) can be prepared by applying a mixture prepared by dissolving the electron acceptor and the hole acceptor in a solvent, by a slot-die coating method, a spraying method, a spin coating method, a dipping method, a printing method, a doctor blade method or a sputtering method.

Preferably, the photoactive layer (140) can be produced by immersing a transparent conductive film (121) on which the metal oxide thin film layer (170), in a coating solution (172) containing a hole acceptor, an electron acceptor and a solvent, while conveying the transparent conductive film by a roll-to-roll method. At this time, the metal oxide thin film layer (170) can be applied by a slot-die coating method, a spraying method, a spin coating method, a dipping method, a printing method, a doctor blade method, or a sputtering method.

The hole acceptor and the electron acceptor are the same as those described above for the organic solar cell (100), and specific explanations will not be repeated. Furthermore, the coating solution (171) can be prepared by adding the hole acceptor and the electron acceptor, or precursors thereof, in the solvent described above, and stirring the mixture.

The step of producing the photoactive layer (140) may further include a post-treatment step of performing drying and a heat treatment at 25℃ to 150℃ for 5 minutes to 145 minutes. By appropriately controlling the drying process and the heat treatment process, an appropriate phase separation between the electron acceptor and the hole acceptor can be induced, and orientation of the electron acceptor can be induced. In the case of the heat treatment step, if the temperature is lower than 25℃, the mobility of the electron acceptor and the hole acceptor is low, and the heat treatment effect may be negligible. If the heat treatment temperature is higher than 150℃, the performance may be decreased due to deterioration of the electron acceptor. Furthermore, the heat treatment time is less than 5 minutes, the mobility of the electron acceptor and the hole acceptor is low, and thus the heat treatment effect may be negligible. If the heat treatment time is longer than 145 minutes, the performance may be decreased due to deterioration of the electron acceptor.

Alternatively, a hole transport layer (150) can be formed on the photoactive layer (140), while conveying the transparent conductive film (121) on which the photoactive layer (140) has been formed by a roll-to-roll method (STEP 4). The hole transport layer (150) can be prepared by applying the hole transporting substance by a slot-die coating method, a spraying method, a spin coating method, a dipping method, a printing method, a doctor blade method, or a sputtering method.

Preferably, the hole transport layer (150) can be produced by immersing the base material film (110) on which the photoactive layer (140) has been formed in a coating solution (173) containing a hole transporting substance and a solvent, while conveying the base material film by a roll-to-roll method. At this time, the photoactive layer (140) can be applied by a slot-die coating method, a spraying method, a spin coating method, a dipping method, a printing method, a doctor blade method, or a sputtering method.

Since the hole transporting substance is the same as the hole transporting substance described in connection with the organic solar cell (100), specific descriptions will not be repeated. Furthermore, since the solvent is the same as the solvent described in connection with the step of forming the metal oxide thin film layer (170), specific descriptions will not be repeated. The coating solution (173) can be prepared by adding the hole transporting substance or a precursor thereof to the solvent, and then stirring the mixture.

Finally, the cathode (160) can be formed on the hole transport layer (150) by applying the cathode-forming substance through screen printing, Gravure printing, Gravure-offset printing, thermal vapor deposition, electron beam deposition, RF or magnetron sputtering, chemical deposition, or a similar method (STEP 5).

On the other hand, the cathode (160) can be produced by immersing a transparent conductive film (121) on which the photoactive layer (140) in a coating solution (173) containing metal particles and a solvent, while conveying the transparent conductive film by a roll-to-roll method. At this time, the metal oxide thin film layer (170) and the photoactive layer (140) can be applied by a slot-die coating method, a spraying method, a spin coating method, a dipping method, a printing method, a doctor blade method, or a sputtering method.

Since the coating solution (173) contains metal particles and a solvent, the coating solution can be prepared by dispersing any one selected from the group consisting of metal particles, metal precursor particles, metal ions, and combinations thereof, in a solvent. Since the solvent is the same as the solvent described in connection with the step of forming the metal oxide thin film layer (170), specific descriptions will not be repeated.

The metal particles may be metal nanoparticles. Furthermore, the particle size of the metal particles may be 1 nm to 50 nm, or 3 nm to 20 nm, or 6 nm to 14 nm.

Furthermore, the metal particles may be particles of any one selected from the group consisting of silver (Ag), copper (Cu), gold (Au), platinum (Pt), titanium (Ti), aluminum (Al), nickel (Ni), zirconium (Zr), iron (Fe), manganese (Mn), and combinations thereof, and preferably may be particles of any one selected from the group consisting of Ag, Cu, Au, Pt, Al and combinations thereof. The metal particles may be more preferably particles of any one selected from the group consisting of Ag, Cu, Au and combinations thereof, even more preferably any one selected from the group consisting of Ag, Cu, and combinations thereof, and most preferably Ag.

The metal precursor particles may be particles of any one selected from the group consisting of silver nitrate (AgNO₃), Cu(hexafluoroacetylacetonate)₂ (Cu(HAFC)₂), Cu(HAFC)(1,5-Cyclooctanediene), Cu(HAFC)(1,5-Dimethylcyclooctanediene), Cu(HAFC)(4-Methyl-1-pentene), Cu(HAFC)(Vinylcyclohexane), Cu(HAFC)(DMB), Cu(tetramethylheptanedionate)₂ (Cu(TMHD)₂), dimethylaluminum hydride (DMAH), tetramethylethylenediamine (TMEDA), dimethylethylamine alane (DMEAA), TMA (trimethylaluminum), TEA (triethylaluminum), TBA (triisobutylaluminum), TDMAT (tetra(dimethylamino)titanium), TDEAT (tetra(dimethylamino)titanium), and combinations thereof, and preferably silver nitrate.

The method for producing an organic solar cell of the present invention enables continuously applying thin film layers each having a thickness of 10 nm to 1,000 nm, so that the process cost can be reduced. The method of the present invention can reduce the thickness deviation of the thin film layer thus produced, and can therefore enhance the efficiency of the organic solar cell.

FIG. 1 is a perspective view diagram illustrating the organic solar cell according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram schematically illustrating the method for producing an organic solar cell according to another exemplary embodiment of the present invention.

FIG. 3 to FIG. 6 are FE-SEM photographs of the metal oxide thin film layers produced in Examples 1, 2 and 4, and Reference Example 1.

Hereinafter, embodiments of the present invention will be described in detail so that those having ordinary skill in the art to which the present invention is pertained can easily carry out the invention. However, the present invention can be realized in various different forms, and is not intended to be limited to the embodiments described herein.

[Preparation Example: Production of organic solar cell]

(Example 1)

While a PET base material film was conveyed by a roll-to-roll method, an etch resist was screen printed, and the etch resist was UV-cured. Subsequently, the resist was etched with an aqueous solution of copper chloride and was stripped with sodium hydroxide, and thereby, a pattern was formed. The pattern was washed with deionized water and dried, and thus a transparent conductive film was produced.

On the other hand, 36 g of zinc acetate and 36 g of a potassium hydroxide basic additive were added to 3 L of an alcohol solvent, and the mixture was encapsulated, sealed, and then stirred. Thus, a mixed solution was prepared. The mixed solution thus prepared was subjected to a low temperature reaction for 6 hours at 60℃, and thus 24 g of a precipitate of ZnO was produced. The ZnO thus produced was collected and redispersed in 240 ml of chlorobenzene to prepare a coating solution.

While the transparent conductive film produced as described above was conveyed by a roll-to-roll method at a speed of 0.1 m/min, the transparent conductive film was immersed into the coating solution for 5 minutes such that the angle formed by the thin film layer-formed surface of the transparent conductive film and the surface of the coating solution when the transparent conductive film was submerged into the coating solution and the angle formed when the transparent conductive film was removed from the coating solution, were respectively set to 150°. Thus, a metal oxide thin film layer having a thickness of 25 nm was formed.

After the metal oxide thin film layer was formed, the thin film layer was heated for 5 minutes in a hot air dryer at 130℃, and thereby, the solvent remaining in the thin film layer was completely removed.

While the transparent conductive film on which the metal oxide thin film layer was formed was conveyed by a roll-to-roll method, the transparent conductive film was immersed in a P3HT:PCBM blend solution, and thus a photoactive layer was formed on the metal oxide thin film layer. Furthermore, while the transparent conductive film on which the photoactive layer was formed was conveyed by a roll-to-roll method, the transparent conductive film was immersed in a PEDOT:PSS blend solution, and a hole transport layer was formed on the photoactive layer. At this time, the conveying speed was 0.1 m/min, and the transparent conductive film was immersed into the coating solution for 5 minutes such that the angle formed by the thin film layer-formed surface of the transparent conductive film and the surface of the coating solution when the transparent conductive film was submerged into the P3HT:PCBM blend solution and the PEDOT:PSS blend solution, and the angle formed when the transparent conductive film was removed from the blend solutions, were respectively set to 150°.

The P3HT:PCBM blend solution was prepared by mixing P3HT and PCBM into dichlorobenzene solvent at proportions of 25 g/L and 20 g/L, relative to the total weight of the blend solution, and then treating the mixture for one hour or longer at normal temperature by using an ultrasonic cleaner and a vortexer.

Subsequently, an Ag electrode was printed using a screen printer, and thus an organic solar cell was produced.

(Example 2)

An organic solar cell was produced in the same manner as in Example 1, except that the angle formed by the thin film layer-formed surface of the transparent conductive film and the surface of the coating solution when the transparent conductive film was removed from the coating solution in Example 1, was changed to 140°.

(Example 3)

An organic solar cell was produced in the same manner as in Example 1, except that the angle formed by the thin film layer-formed surface of the transparent conductive film and the surface of the coating solution when the transparent conductive film was submerged into the coating solution in Example 1 was changed to 60°, and the angle formed by the thin film layer-formed surface of the transparent conductive film and the surface of the coating solution when the transparent conductive film was removed from the coating solution in Example 1, was changed to 150°.

(Example 4)

An organic solar cell was produced in the same manner as in Example 1, except that the angle formed by the thin film layer-formed surface of the transparent conductive film and the surface of the coating solution when the transparent conductive film was submerged into the coating solution in Example 1 was changed to 20°, and the angle formed by the thin film layer-formed surface of the transparent conductive film and the surface of the coating solution when the transparent conductive film was removed from the coating solution in Example 1, was changed to 150°.

(Example 5)

An organic solar cell was produced in the same manner as in Example 1, except that the angle formed by the thin film layer-formed surface of the transparent conductive film and the surface of the coating solution when the transparent conductive film was submerged into the coating solution in Example 1 was changed to 160°, and the angle formed by the thin film layer-formed surface of the transparent conductive film and the surface of the coating solution when the transparent conductive film was removed from the coating solution in Example 1, was changed to 150°.

(Example 7)

An organic solar cell was produced in the same manner as in Example 1, except that the conveying speed of the transparent conductive film in Example 1 was adjusted to 0.4 m/min.

(Example 8)

An organic solar cell was produced in the same manner as in Example 1, except that the conveying speed of the transparent conductive film in Example 1 was adjusted to 1.0 m/min.

(Example 9)

An organic solar cell was produced in the same manner as in Example 1, except that the conveying speed of the transparent conductive film in Example 1 was adjusted to 5.0 m/min.

(Example 10)

An organic solar cell was produced in the same manner as in Example 1, except that the conveying speed of the transparent conductive film in Example 1 was adjusted to 5.5 m/min.

(Reference Example 1)

An ITO base material film on which a transparent electrode was patterned was washed with an ultrasonic cleaner, and was dried using a hot air dryer. Subsequently, the ITO base material film was surface-treated using a UV/O₃ cleaner.

On the other hand, 3 g of zinc acetate and 3 g of a potassium hydroxide basic additive were added to 250 ml of an alcohol solvent, and the mixture was encapsulated, sealed, and then stirred to prepare a coating solution. The mixing solution thus prepared was subjected to a low temperature reaction for 6 hours at 60℃, and thus 3 g of a precipitate of ZnO was produced. The ZnO precipitate thus produced was collected and redispersed in 30 ml of chlorobenzene, and thus a coating solution was prepared. The coating solution was applied on the ITO base material film by dip coating at an angle of 90°, and thus a metal oxide thin film layer having a thickness of 120 nm was formed. After the metal oxide thin film layer was formed, the solvent remaining in the thin film layer was completely removed by heating the base material film for 2 minutes on a hot plate at 220℃.

On the base material film on which the metal oxide thin film layer was formed, a P3HT:PCBM blend solution was applied by spin coating for 30 seconds at 800 rpm. PEDOT:PSS [poly(3,4-ethylenedioxythiophene/poly(styrene sulfonate)) was applied on the P3HT:PCBM photoactive layer by spin coating for 30 seconds at a speed of 4,000 rpm.

The solvent remaining in the thin film was removed, and in order to form a crystal structure of the active layer polymer, drying for one hour or longer and a heat treatment for about 20 minutes were carried out in a nitrogen atmosphere at normal temperature. After the heat treatment was completed, an Ag electrode was formed by bar coating, and thus an organic solar cell was produced.

[Experiment Example: Analysis of performance of organic solar cell produced]

The thicknesses of the metal oxide thin film layers produced in the Examples and Reference Example were measured using FE-SEM. The results for Examples 1, 2 and 7 and Reference Example 1 are presented in FIG. 3 to FIG. 6. According to FIG. 3 to FIG. 6, the metal oxide thin film layers produced in Examples 1, 2 and 7 had thicknesses of 25 nm, 33nm, and 75 nm, respectively, and the metal oxide thin film layer produced in Reference Example 1 had a thickness of 120 nm.

Furthermore, for the organic solar cells produced in the Examples and Reference Example, the current-voltage characteristics were measured by using a solar simulator, Newport Corp., 66984), and the results of Examples 1 to 10 and Reference Example are presented in the following Table 1.

The solar simulator used a 300-W xenon lamp (Newport Corp., 6258) and an AM1.5G filter (Newport Corp., 81088A), and the intensity of light was set to 100 mW/cm².

Table 1

	Energy conversion efficiency (%)	Short-circuit current density (mA/cm²)	Open circuit voltage (V)	Fill Factor (%)
Example 1	1.58	5.943	0.503	52.98
Example 2	1.45	5.742	0.492	51.21
Example 3	1.38	5.332	0.501	49.68
Example 4	1.36	5.63	0.497	48.69
Example 5	1.46	5.813	0.501	50.26
Example 6	1.27	5.413	0.493	47.93
Example 7	1.21	5.8	0.47	44.09
Example 8	1.46	5.825	0.498	50.23
Example 9	1.46	5.674	0.505	51.12
Example 10	1.35	5.31	0.489	52.11
Reference Example 1	1.21	5.6	0.48	45.40

According to Table 1, it can be seen that the performance of the organic solar cells produced in Examples 1 to 10 is superior to the performance of the organic solar cell produced in Reference Example 1.

In the organic solar cells produced in the Examples, the thickness difference of the metal oxide thin film layer can be reduced by forming a metal oxide thin film layer by immersing a transparent conductive film in a coating solution containing a metal oxide precursor and an organic solvent, while the transparent conductive film by a roll-to-roll method, and the efficiency of the organic solar cell is enhanced.

While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the scope of the present invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

A method for producing an organic solar cell, the method comprising forming a thin film layer by immersing a base material film in a coating solution, while conveying the base material film by a roll-to-roll method.
The method for producing an organic solar cell according to claim 1, wherein the angle formed by the thin film layer-formed surface and the surface of the coating solution when the base material film is submerged into the coating solution is 0° to 180°, and

the angle formed by the thin film layer-formed surface and the surface of the coating solution when the base material film is removed from the coating solution is 0° to 180°.
The method for producing an organic solar cell according to claim 1, wherein the time for immersing the base material film into the coating solution is 1 minute to 20 minutes.
The method for producing an organic solar cell according to claim 1, wherein the base material film is conveyed by a roll-to-roll method at a speed of 0.01 m/min to 20 m/min.
The method for producing an organic solar cell according to claim 1, wherein the concentration of the coating solution is 0.01 mg/ml to 1,000 mg/ml.
The method for producing an organic solar cell according to claim 1, wherein the thickness of the thin film layer is 10 nm to 1,000 nm.
The method for producing an organic solar cell according to claim 1, further comprising drying the thin film layer at 50℃ to 400℃ for 1 minute to 30 minutes after the thin film layer is formed.
The method for producing an organic solar cell according to claim 1, wherein the step of forming a thin film layer is a step of forming a transparent conductive thin film layer by immersing the base material film into a coating solution containing a transparent conductive substance and a solvent, while conveying the base material film by a roll-to-roll method.
The method for producing an organic solar cell according to claim 8, wherein the transparent conductive substance is any one selected from the group consisting of tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), ZnO-Ga₂O₃, ZnO-Al₂O₃, SnO₂-Sb₂O₃, conductive polymers, graphene, graphene oxide, carbon nanotubes, and combinations thereof.
The method for producing an organic solar cell according to claim 8, wherein the solvent is any one selected from the group consisting of water, ethanol, methanol, propanol, isopropanol, butanol, acetone, pentane, toluene, benzene, diethyl ether, methyl butyl ether, N-methylpyrrolidone (NMP), tetrahydrofuran (THF), dimethylformamide (DMF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), carbon tetrachloride, dichloromethane, dichloroethane, trichloroethylene, chloroform, chlorobenzene, dichlorobenzene, trichlorobenzene, cyclohexane, cyclopentanone, cyclohexanone, dioxane, terpineol, methyl ethyl ketone, and combinations thereof.
The method for producing an organic solar cell according to claim 1, wherein the step of forming a thin film layer is a step of forming a metal oxide thin film layer by immersing the base material film into a coating solution containing a metal oxide precursor and a solvent, while conveying the base material film by a roll-to-roll method.
The method for producing an organic solar cell according to claim 11, wherein the average particle size of the metal oxide is 10 nm or less.
The method for producing an organic solar cell according to claim 11, wherein the metal oxide precursor is any one selected from the group consisting of a metal chloride, a metal acetate, a metal citrate, a metal (meth)acrylate, a metal bromide, a metal cyanide, a metal phosphate, a metal sulfate, a metal sulfide, and combinations thereof.
The method for producing an organic solar cell according to claim 11, wherein the metal in the metal oxide precursor is any one selected from the group consisting of Ti, Zn, Si, Mn, Sr, In, Ba, K, Nb, Fe, Ta, W, Sa, Bi, Ni, Cu, Mo, Ce, Pt, Ag, Rh, and combinations thereof.
The method for producing an organic solar cell according to claim 1, wherein the step of forming a thin film layer is a step of forming a photoactive layer by immersing the base material film into a coating solution containing a hole acceptor, an electron acceptor, and a solvent, while conveying the base material film by a roll-to-roll method.
The method for producing an organic solar cell according to claim 15, wherein the hole acceptor is any one selected from the group consisting of poly-3-hexylthiophene [P3HT], poly-3-octylthiophene [P3OT], poly(p-phenylene vinylene) [PPV], poly(9,9'-dioctylfluorene), poly(2-methoxy-5-(2-ethylehexyloxy)-1,4-phenylenevinylene) [MEH-PPV], poly(2-methyl-5-(3',7'-dimethyloctyloxy))-1,4-phenylenevinylene [MDMOPPV], precursors thereof, and combinations thereof.
The method for producing an organic solar cell according to claim 15, the electron acceptor is any one selected from the group consisting of (6,6)-phenyl-C₆₁-butyric acid methyl ester [PCBM], (6,6)-phenyl-C₇₁-butyric acid methyl ester [C70-PCBM], (6,6)-thienyl-C₆₁-butyric acid methyl ester [ThCBM], carbon nanotubes, precursors thereof, and combinations thereof.
The method for producing an organic solar cell according to claim 1, wherein the step of forming a thin film layer is a step of forming a hole transport layer by immersing the base material film into a coating solution containing a hole transporting substance and a solvent, while conveying the base material film by a roll-to-roll method.
The method for producing an organic solar cell according to claim 18, wherein the hole transporting substance is any one selected from the group consisting of poly(3,4-ethylenedioxythiophene) (PEDOT), poly(styrene sulfonate) (PSS), polyaniline, phthalocyanine, pentacene, polydiphenylacetylene, poly(t-butyl)diphenylacetylene, poly(trifluoromethyl)diphenylacetylene, copper phthalocyanine (Cu-PC), poly(bistrifluoromethyl)acetylene, polybis(t-butyldiphenyl)acetylene, poly(trimethylsilyl)diphenylacetylene, poly(carbazole)diphenylacetylene, polydiacetylene, polyphenylacetylene, polypyridineacetylene, polymethoxyphenylacetylene, polymethylphenylacetylene, poly(t-butyl)phenylacetylene, polynitrophenylacetylene, poly(trifluoromethyl)phenylacetylene, poly(trimethylsilyl)phenylacetylene, precursors thereof, and combinations thereof.
The method for producing an organic solar cell according to claim 1, wherein the step of forming a thin film layer is a step of forming an electrode by immersing the base material film into a coating solution containing metal particles and a solvent, while conveying the base material film by a roll-to-roll method.
The method for producing an organic solar cell according to claim 20, wherein the metal particles are particles of any one selected from the group consisting of silver (Ag), copper (Cu), gold (Au), platinum (Pt), titanium (Ti), aluminum (Al), nickel (Ni), zirconium (Zr), iron (Fe), manganese (Mn), precursors thereof, and combinations thereof.
The method for producing an organic solar cell according to any one of claims 11, 15, 18 and 20, wherein the solvent is any one selected from the group consisting of ethanol, methanol, propanol, isopropanol, butanol, acetone, pentane, toluene, benzene, diethyl ether, methyl butyl ether, N-methylpyrrolidone (NMP), tetrahydrofuran (THF), dimethylformamide (DMF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), carbon tetrachloride, dichloromethane, dichloroethane, trichloroethylene, chloroform, chlorobenzene, dichlorobenzene, trichlorobenzene, cyclohexane, cyclopentanone, cyclohexanone, dioxane, terpineol, methyl ethyl ketone, and combinations thereof.
An organic solar cell produced by the method for producing an organic solar cell according to claim 1.