KR101368816B1 - Organic solar cell and preparing method of the same - Google Patents

Abstract

A transparent electrode and a metal electrode disposed to face each other; And a photoelectric conversion layer positioned between the transparent electrode and the metal electrode, wherein the photoelectric conversion layer includes metal nanoparticles dispersed in a blend of an electron donor and an electron acceptor. That is, an organic solar cell, and a method of manufacturing the same are disclosed.

Description

Organic solar cell and its manufacturing method {ORGANIC SOLAR CELL AND PREPARING METHOD OF THE SAME}

The present application relates to an organic solar cell and a method of manufacturing the same, and to an organic solar cell including a photoelectric conversion layer in which metal nanoparticles are dispersed, and a method of manufacturing the same.

A solar cell is a device based on the semiconductor principle, and has a characteristic of converting solar energy into electrical energy. Depending on the materials used, it can be classified into silicon solar cell and organic solar cell.Silicone solar cell is known as a big device industry because of its high manufacturing and process cost.Since silicon reserves are limited, it is limited to general application in the future. I am getting it. On the other hand, organic solar cells are not only significantly lower than silicon solar cells, but do not require expensive special vacuum equipment, so they are easy to fabricate, large area, and room temperature. It is possible to fabricate a device that can bend. Due to the above advantages and prospects, research is being actively conducted in numerous research institutes, schools, and corporations around the world.

In order to increase the efficiency of organic solar cells, researches have been made on the development of new conductive polymer materials capable of increasing the solar absorption region and the design of efficient device structures. In particular, electron donors forming the photoelectric conversion layer of organic solar cells Bulk heterojunction (BHJ) structure using an appropriate blend between the electron acceptor and the electron acceptor allows the interfacial contact to generate electron-hole charges in the photovoltaic layer of the solar cell. It is known as the best structure because of its large area. There is a bilayer structure consisting of only the electron donor (bottom) layer and the electron acceptor (top) layer, which has a disadvantage that the interfacial area between the two layers is smaller than that of the bulk heterojunction structure and the bonding interface is increased. In the electron-hole charge generation is lower than the bulk heterojunction structure has a disadvantage in that the efficiency of the solar cell is reduced.

The bulk heterojunction structure, which receives solar light, usually has electrons within this distance because the diffusion distance between the electrons formed in the electron donor in the photoconversion layer and the exciton, the hole pair, can travel only 10 nm in the photoconversion layer. If the interface between the donor and the electron acceptor is not reached, there is a problem of recombination and extinction. Therefore, in order to overcome this recombination phenomenon and to manufacture an efficient electron donor / electron acceptor structure, a study on the synthesis and increase of new materials that can increase the amount of light absorption in the photoelectric conversion layer, and between the electron donor / electron acceptor mixture Changes in composition, optimization of process conditions during spin coating, change of annealing environment, and optimization of solvent conditions are required.

After being separated into electrons and holes at the interface between the electron donor and the electron acceptor in the solar cell, the two charges move to the transparent electrode, which is the negative electrode, and the metal electrode, which is the positive electrode, respectively. In general, the electron donor / electron acceptor structure is usually divided into phases in the form of a sea and island. For the smooth operation of the solar cell, the electron donor has a co-continuous structure inside the photoelectric conversion layer. The negative electrode must be connected, and the electron acceptor must be in contact with the positive electrode.

For example, efficient charge transfer is possible by layer-by-layer deposition of metal nanorods having a size of 30 nm or less on a transparent electrode of a solar cell by thermally transformed methods. ) And a method of increasing the efficiency [J. H. Lee., Org. Electron. 10: 416-420, 2009. However, the conventional method has a difficulty in introducing the metal nanoparticles into the transparent electrode of the solar cell, the cost problem is serious because the high temperature deposition process is essential, the case of a small metal rod and one polymer material It is limited to

As such, there are many variables that determine the efficiency of the organic solar cell, but basically, in order to increase the efficiency of the organic solar cell, the amount of charge generated is increased by increasing the amount of light absorption in the photoelectric conversion layer from the beginning or the generated charge. It is important to efficiently move N to each electrode.

The present application, a transparent electrode and a metal electrode disposed opposite each other; And a photoelectric conversion layer positioned between the transparent electrode and the metal electrode, wherein the photoelectric conversion layer includes metal nanoparticles dispersed in a blend of an electron donor and an electron acceptor. That is, to provide an organic solar cell.

In addition, the present invention, forming a transparent electrode on a transparent substrate; Forming a photoelectric conversion layer on the transparent electrode; And forming a metal electrode on the photoelectric conversion layer, wherein the photoelectric conversion layer is prepared by mixing and dispersing metal nanoparticles in a solution including an electron donor and an electron acceptor. To provide a method.

However, the problem to be solved by the present application is not limited to the problem described above, another problem that is not described will be clearly understood by those skilled in the art from the following description.

The first aspect of the present application, a transparent electrode and a metal electrode disposed opposite each other; And a photoelectric conversion layer positioned between the transparent electrode and the metal electrode, wherein the photoelectric conversion layer includes metal nanoparticles dispersed in a blend of an electron donor and an electron acceptor. That is, to provide an organic solar cell, but is not limited thereto.

According to the exemplary embodiment of the present application, the electron donor includes a conductive organic polymer, and the electron acceptor includes a fullerene compound, a perylene compound, or semiconductor nanoparticles. The conductive organic polymer and the fullerene-based compound, the perylene-based compound, or the semiconducting nanoparticle may form a bulk heterojunction (BHJ), but are not limited thereto.

According to the exemplary embodiment of the present application, the conductive organic polymer may include an amorphous organic polymer, but is not limited thereto.

According to one embodiment of the present invention, the metal nanoparticles are gold (Au), silver (Ag), platinum (Pt), palladium (Pd), aluminum (Al), copper (Cu), nickel (Ni), zinc ( Zn), iron (Fe), and may include a metal selected from the group consisting of combinations thereof, but is not limited thereto.

According to one embodiment of the present application, the diameter of the metal nanoparticle may be about 30 nm to about 90 nm, but is not limited thereto.

According to one embodiment of the present application, the conductive organic polymer is poly-3-hexylthiophene (poly-3-hexylthiophene = P3HT), poly (N-9 "-hepta-decanyl-2,7-carbazole- Alt-5,5- (4 ', 7'-di-2-thienyl-2', 1 ', 3')-benzothiadiazole) {poly (N-9 "-hepta-decanyl-2, 7-carbazole-alt-5,5- (4 ', 7'-di-2-thienyl-2', 1 ', 3')-benzothiadiazole) = PCDTBT}, poly [(4,4'-bis (2 -Ethylhexyl) dithieno [3,2-b: 2 ', 3'-d] silol) -2,6-diyl-alt- (4,7-bis (2-thienyl) -2,1, 3-benzotaidiazole) -5,5'-diyl {poly [(4,4'-bis (2-ethylhexyl) dithieno [3,2-b: 2 ', 3'-d] silole) -2, 6-diyl-alt- (4,7-bis (2-thienyl) -2,1,3-benzothiadiazole) -5,5'-diyl = Si-PCPDTBT}, and combinations thereof It may include, but is not limited thereto.

According to one embodiment of the invention, the fullerene compound is (6,6) -phenyl -C ₆₁ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 61} -butyric acid methyl ester = PC 60 BM] , (6,6) -phenyl -C ₇₁ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 71} -butyric acid methyl ester = PC 70 BM], (6,6) - phenyl -C ₇₇ - Butyric acid methyl ester [(6,6) -phenyl-C ₇₇ -butyric acid methyl ester = PC ₇₆ BM], (6,6) -phenyl-C ₇₉ -butyric acid methyl ester [(6,6)- _{phenyl-C 79 -butyric acid methyl ester} = PC 78 BM], (6,6) - phenyl -C ₈₁ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 81} -butyric acid methyl ester = PC 80 BM], (6,6) - phenyl -C ₈₃ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 83} -butyric acid methyl ester = PC 82 BM], (6,6) - phenyl -C _85-butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 85} -butyric acid methyl ester = PC 84 BM], and, but could be to include those selected from the group consisting of the combinations thereof, whereby the It is not.

According to the exemplary embodiment of the present application, the metal nanoparticle may be 20 wt% or less with respect to the total weight of the photoelectric conversion layer, but is not limited thereto.

According to the exemplary embodiment of the present application, the metal nanoparticle may be 5 wt% or less with respect to the total weight of the photoelectric conversion layer, but is not limited thereto.

According to an embodiment of the present disclosure, the metal nanoparticles include octahedron gold (Au) nanoparticles or truncated octahedron gold (Au) nanoparticles. It may be, but is not limited thereto.

According to one embodiment of the present application, the metal nanoparticles may include silver (Ag) nanoparticles, but is not limited thereto.

According to one embodiment of the present application, a hole transport layer formed between the transparent electrode and the photoelectric conversion layer, and may further include an electron transport layer formed between the transparent electrode and the photoelectric conversion layer, but is not limited thereto.

According to one embodiment of the present application, the photoelectric conversion layer may be in the form of a thin film having a thickness of about 10 nm to about 200 nm, but is not limited thereto.

A second aspect of the present invention, forming a transparent electrode on a transparent substrate; Forming a photoelectric conversion layer on the transparent electrode; And forming a metal electrode on the photoelectric conversion layer, wherein the photoelectric conversion layer is prepared by mixing and dispersing metal nanoparticles in a solution including an electron donor and an electron acceptor. It provides a method of manufacturing an organic solar cell according to the side.

According to one embodiment of the present application, the solution including the electron donor and the electron acceptor is not particularly limited as long as it can dissolve both the electron donor and the electron acceptor as a solvent, for example, chlorobenzene, 1 1,2-dichlorobenzene, chloroform, acetone, acetonitrile, dimethylacetamide (DMAc), dimethyl formamide (DMF), dimethyl sulfoxide Dimethyl sulfoxise (DMSO), methyl ethyl ketone, methyl n-propyl ketone, N-methylpyrrolidone (NMP), propylene carbonate (propylene carbornate) It may include one or more selected from the group consisting of nitromethane, sulforane, ethylene glycol and hexamethylphophoramide (HMP). But is not limited thereto.

According to the exemplary embodiment of the present application, the electron donor includes a conductive organic polymer, and the electron acceptor includes a fullerene compound, a perylene compound, or semiconductor nanoparticles. In some embodiments, the conductive organic polymer and the fullerene-based compound, the perylene-based compound, or the semiconductor nanoparticle may form a bulk heterojunction (BHJ), but are not limited thereto.

According to the exemplary embodiment of the present application, the conductive organic polymer may include an amorphous organic polymer, but is not limited thereto.

According to one embodiment of the present invention, the metal nanoparticles are gold (Au), silver (Ag), platinum (Pt), palladium (Pd), aluminum (Al), copper (Cu), nickel (Ni), zinc (Zn) ), Iron (Fe), and combinations thereof may include metal selected from the group consisting of, but is not limited thereto.

According to one embodiment of the present application, the diameter of the metal nanoparticle may be about 30 to about 90 nm, but is not limited thereto.

According to one embodiment of the present application, the conductive organic polymer is poly-3-hexylthiophene (poly-3-hexylthiophene = P3HT), poly (N-9 "-hepta-decanyl-2,7-carbazole-alt -5,5- (4 ', 7'-di-2-thienyl-2', 1 ', 3')-benzothiadiazole) {poly (N-9 "-hepta-decanyl-2,7 -carbazole-alt-5,5- (4 ', 7'-di-2-thienyl-2', 1 ', 3')-benzothiadiazole) = PCDTBT}, poly [(4,4'-bis (2- Ethylhexyl) dithieno [3,2-b: 2 ', 3'-d] silol) -2,6-diyl-alt- (4,7-bis (2-thienyl) -2,1,3 -Benzotadiazole) -5,5'-diyl {poly [(4,4'-bis (2-ethylhexyl) dithieno [3,2-b: 2 ', 3'-d] silole) -2,6 -diyl-alt- (4,7-bis (2-thienyl) -2,1,3-benzothiadiazole) -5,5'-diyl = Si-PCPDTBT}, and combinations thereof It may be included, but is not limited thereto.

According to one embodiment of the invention, the fullerene compound is (6,6) -phenyl -C ₆₁ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 61} -butyric acid methyl ester = PC 60 BM] , (6,6) -phenyl-C ₇₁ -butyric acid methyl ester [(6,6) -phenyl-C71-butyric acid methyl ester = PC ₇₀ BM], (6,6) -phenyl-C ₇₇ -buty Ricacid methyl ester [(6,6) -phenyl-C ₇₇ -butyric acid methyl ester = PC ₇₆ BM], (6,6) -phenyl-C ₇₉ -butyric acid methyl ester [(6,6) -phenyl _{-C 79 -butyric acid methyl ester = PC} 78 BM], (6,6) - phenyl -C ₈₁ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 81} -butyric acid methyl ester = PC 80 BM ], (6,6) -phenyl -C ₈₃ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 83} -butyric acid methyl ester = PC 82 BM], (6,6) - ₈₅ phenyl -C -butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 85} -butyric acid methyl ester = PC 84 BM], and, but could be to include those selected from the group consisting of the combinations thereof, limited to It is not.

According to the exemplary embodiment of the present application, the metal nanoparticle may be about 20 wt% or less with respect to the total weight of the photoelectric conversion layer, but is not limited thereto.

According to the exemplary embodiment of the present application, the metal nanoparticle may be about 5 wt% or less with respect to the total weight of the photoelectric conversion layer, but is not limited thereto.

According to an embodiment of the present disclosure, the metal nanoparticles include octahedron gold (Au) nanoparticles or truncated octahedron gold (Au) nanoparticles. It may be, but is not limited thereto.

According to one embodiment of the present application, the metal nanoparticles may include silver (Ag) nanoparticles, but is not limited thereto.

According to one embodiment of the present application, a hole transport layer formed between the transparent electrode and the photoelectric conversion layer, and may further include an electron transport layer formed between the transparent electrode and the photoelectric conversion layer, but is not limited thereto.

According to one embodiment of the present application, the photoelectric conversion layer may be in the form of a thin film having a thickness of about 10 nm to about 200 nm, but is not limited thereto.

According to the present application, an organic solar cell including a photoelectric conversion layer containing metal nanoparticles may have the following effects by the metal nanoparticles.

Specifically, the metal nanoparticles reflect or scatter light in the photoelectric conversion layer, thereby increasing the light path, which causes an increase in ultraviolet and visible light absorption of the photoelectric conversion layer. In addition, the metal nanoparticles have a surface plasmon effect. In addition, when the metal nanoparticles are included in the photoelectric conversion layer, the electron and hole transport characteristics may be improved, and as a result, the electrical conductivity to both electrodes is increased. In addition, when the metal nanoparticles have a size of several tens of nm, which is about 30 nm to about 90 nm, the scattering effect is increased and the area of the interface between the photoelectric conversion layer and the metal particles is reduced, compared to 10 nm metal nanoparticles. Charge transfer characteristics may appear. In other words, the external quantum efficiency is increased. As a result, when the metal nanoparticles are contained in the photoelectric conversion layer, the efficiency of the organic solar cell increases.

In addition, the present application, the metal nanoparticles according to the present application to the crystalline P3HT organic polymer which is an electron donor used in the photoelectric conversion layer and the Si-PCPDTBT organic polymer having a low band gap and PCDTBT which is an amorphous organic polymer, respectively The efficiency of the organic solar cell can be improved by introducing. In addition, in comparison with the organic solar cell using the P3HT crystalline organic polymer that requires a high temperature post-heat treatment (post annealing), when using the PCDTBT which is the amorphous organic polymer, a high temperature post-heat treatment is not necessary, thereby manufacturing an organic solar cell. The process can be simplified, the consumption costs can be reduced, and the efficiency can be improved.

1 is a schematic diagram of an organic solar cell according to an embodiment of the present disclosure.
Figure 2 is a method of manufacturing an organic solar cell in one embodiment of the present application.
3 is a scanning electron micrograph of gold nanoparticles of the truncated octaheadron structure used as metal nanoparticles in one embodiment of the present application.
FIG. 4 is a graph of EDAX (Energy Dispersive Ananysis of X-ray) analysis of truncated octaheadron gold nanoparticles used as metal nanoparticles in one embodiment of the present application.
Figure 5 is a UV / Vis-absorption spectrum according to the synthesis time in the production of gold nanoparticles used as metal nanoparticles in one embodiment of the present application.
FIG. 6 shows (a) UV / Vis-absorption spectra of truncated octahedron gold nanoparticles used as metal nanoparticles in one embodiment of the present application and photographs of gold nanoparticles dispersed in solution, and (b) P3HT / PC ₇₀ BM and teureon K is suited octa head Ron gold nanoparticles containing 5% of P3HT / UV / Vis- of PC ₇₀ BM absorption spectrum wt.
7 is (a) a scanning electron micrograph of synthesized octahedron gold nanoparticles and a gold nanoparticle solution centrifuged, (b) a gold nanoparticle picture and UV / Vis-absorption spectrum.
8 is a scanning electron micrograph of a photoelectric conversion layer containing a 5 wt% content of truncated gold nanoparticles according to an embodiment of the present application and a polyhedral structure of the truncated gold nanoparticles.
9 shows the structure of PCDTBT, Si-PCPDTBT and P3HT as electron donors used in one embodiment of the present application, and PC ₇₀ BM (PCBM) used as electron acceptors.
FIG. 10 is an IPCE analysis of an organic solar cell containing 5 wt% of the truncated octaheadron gold nanoparticles and an organic solar cell not containing the gold nanoparticles according to an embodiment of the present disclosure, and an electron donor material ( a) P3HT, (b) PCDTBT, and (c) Si-PCPDTBT.
FIG. 11 is a graph showing the current density (J) -voltage (V) of an organic solar cell containing 5 wt% of the truncated octaheadron gold nanoparticles and an organic solar cell not containing the gold nanoparticles according to one embodiment of the present disclosure. ) And the electron donor material is (a) PCDTBT and (b) Si-PCPDTBT.
FIG. 12 contains 0 wt%, 1 wt%, 5 wt%, 10 wt%, and 20 wt% of truncated octahedron gold nanoparticles (T-Octa), respectively, in one embodiment of the present application, P3HT It is a current density (J) -voltage (V) graph of an organic solar cell manufactured using a photoelectric conversion layer including / PC ₇₀ BM.
FIG. 13 shows the current density (J) -voltage (V) of an organic solar cell containing 5 wt% of the truncated octaheadron gold nanoparticles and an organic solar cell not containing the gold nanoparticles according to one embodiment of the present disclosure. ) And the electron donor material is (a) P3HT, (b) PCDTBT, and (c) Si-PCPDTBT.
FIG. 14 is a diffuse reflectance-wavelength (λ) of an organic solar cell containing 5 wt% of the truncated octaheadron gold nanoparticles and an organic solar cell not containing the gold nanoparticles according to one embodiment of the present invention. ) Graph.
FIG. 15 is an energy band diagram of an organic solar cell including (a) gold nanoparticles having an average size of 10 nm or less in a photoelectric conversion layer including P3HT / PC ₇₀ BM, and (b) P3HT. Energy band diagram of an organic solar cell containing gold nanoparticles with an average size of 70 nm in a photoelectric conversion layer containing / PC ₇₀ BM, (c) UPS spectrum, and (d) energy band of each component.
FIG. 16 is an energy band diagram of an organic solar cell including ITO / PEDOT: PSS / electron donor / PC ₇₀ BM / TiOx / Al in an embodiment of the present disclosure.
FIG. 17 is a graph illustrating organic solar cell efficiency depending on thickness, gold nanoparticle content, and photoelectric conversion layer material according to an exemplary embodiment of the present disclosure.
FIG. 18 is a scanning electron micrograph of silver nanoparticles prepared by NaBH ₄ in a dispersion medium containing a polyol according to one embodiment of the present disclosure, wherein the polyol is (a) ethylene glycol (EG), (b) 1 , 2-propanediol (1,2-propanediol, PrD), (c) 1,4-butanediol (1,4-butanediol, BD), (d) 1,5-pentanediol (1,5-pentanediol, PtD ).
FIG. 19 illustrates a scanning electron micrograph and particle size distribution of silver nanoparticles prepared in a polyol-phosphorus dispersion medium according to one embodiment of the present application, wherein the polyol is (a) ethylene glycol (EG), (b) 1,2-propanediol (1,2-propanediol, PrD), (c) 1,4-butanediol (1,4-butanediol, BD), (d) 1,5-pentanediol (1,5-pentanediol, PtD).
FIG. 20 is a scanning electron micrograph of silver nanoparticles synthesized in various sizes by using the chemical structure of PCDTBT and PC ₇₀ BM, schematic diagram of organic solar cell, and polyol process in one embodiment of the present application.
FIG. 21 is a UV / Vis spectrum in one embodiment of the present application, and the subject of each graph is (a) 30 nm, 40 nm, and 60 nm diameter silver nanoparticles, and (b) 40 nm diameter silver nanoparticles. Corresponding to the photoelectric conversion layer containing PCDTBT / PC ₇₀ BM containing 1% or does not contain the silver nanoparticles.
22 is an AFM photograph of the surface of the photovoltaic layer for an organic solar cell manufactured according to an embodiment of the present application, the upper left side of the photoelectric conversion layer containing PCDTBT / PC ₇₀ BM, the upper right side of the 40 nm diameter A photoelectric conversion layer containing 1% by weight of silver nanoparticles, the lower left is a low-resolution photograph of the photoelectric conversion layer containing 1% by weight of silver nanoparticles having a 40 nm diameter, and the lower right side has 1 weight of silver nanoparticles having a 40 nm diameter It is a high resolution photograph of a photoelectric conversion layer containing%.
FIG. 23 shows (a) current density (J) -voltage of an organic solar cell containing 1 wt% of silver nanoparticles having a diameter of 40 nm and an organic solar cell not containing the silver nanoparticles according to one embodiment of the present application. (V) graph, (b) EQE enhancement and EQE spectrum for each wavelength of a photoelectric conversion layer containing 1 wt% of silver nanoparticles of 40 nm diameter, (c) UPS spectrum, and (d) energy diagram.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is " on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as "including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

The terms "about "," substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure. The word " step (or step) "or" step "used to the extent that it is used throughout the specification does not mean" step for.

Throughout this specification, the term " combination (s) thereof " included in the expression of the machine form means a mixture or combination of one or more elements selected from the group consisting of the constituents described in the expression of the form of a marker, Quot; means at least one selected from the group consisting of the above-mentioned elements.

As shown in FIG. 1, an organic solar cell according to an exemplary embodiment of the present disclosure includes a transparent electrode 110 and a metal electrode 150 disposed to face each other; And a photoelectric conversion layer 130 positioned between the transparent electrode 110 and the metal electrode 150, wherein the photoelectric conversion layer is a blend of an electron donor and an electron acceptor. It includes, but is not limited to, metal nanoparticles dispersed in).

In FIG. 1, the transparent electrode 110 may include a transparent conductive metal oxide formed on a glass or plastic transparent substrate, but is not limited thereto. The transparent conductive metal oxide may include a material having a low work function, for example, indium tin oxide (ITO), fluorine tin oxide (FTO), indium zinc oxide (indium zinc oxide) light may be incident by containing an oxide of a transparent conductive metal such as oxide, IZO), ZnO- (Ga ₂ O ₃ or Al ₂ O ₃ ). As the transparent electrode forming material, SnO ₂ having excellent conductivity, transparency and heat resistance, or ITO, which is inexpensive in terms of cost, may be used. For example, an ITO glass substrate or an FTO glass substrate may be used as the transparent electrode 110, but is not limited thereto.

As the plastic substrate, polyethersulfone (polyethersulfone = PES), polyethylene terephthalate (polyethyleneterephthalate = PET), polyethylenenaphthalate (polyethylenenaphthalate = PEN), polyimide (polyimide = PI), polyetheretherketone (PEEK), Polynorbonene (polynorbonene = PNR), polycarbonate (polycarbonate = PC), polyarylate (polyarylate = PAR), polyetherimide = PEI, polyamideimide = PAI, polyamide (polyamide = PA ), And polyphenylene sulfide (PPS) may be used, but is not limited thereto.

The photoelectric conversion layer 130 includes metal nanoparticles dispersed in a blend of the electron donor and the electron acceptor, and a bulk heterojunction is formed by randomly mixing the electron donor and the electron acceptor. , BHJ), but is not limited thereto.

The electron donor comprises a conductive organic polymer, for example poly-3-hexylthiophene (P3HT), poly (N-9 "-hepta-decanyl-2,7-carbazole -Alt-5,5- (4 ', 7'-di-2-thienyl-2', 1 ', 3')-benzothiadiazole) {poly (N-9 "-hepta-decanyl-2 , 7-carbazole-alt-5,5- (4 ', 7'-di-2-thienyl-2', 1 ', 3')-benzothiadiazole) = PCDTBT}, poly [(4,4'-bis ( 2-ethylhexyl) dithieno [3,2-b: 2 ', 3'-d] silol) -2,6-diyl-alt- (4,7-bis (2-thienyl) -2,1 , 3-benzotaidiazole) -5,5'-diyl {poly [(4, 4'-bis (2-ethylhexyl) dithieno [3,2-b: 2 ', 3'-d] silole) -2 , 6-diyl-alt- (4,7-bis (2-thienyl) -2,1,3-benzothiadiazole) -5,5'-diyl = Si-PCPDTBT}, and combinations thereof It includes, but is not limited to. In one embodiment, the conductive organic polymer may include an amorphous organic polymer, but is not limited thereto. For example, the amorphous conductive organic polymer may include PCDTBT or Si-PCPDTBT, but is not limited thereto.

The electron acceptor may include, but is not limited to, a fullerene-based compound, a perylene-based compound, or semiconducting nanoparticles. The fullerene-based compound (6,6) -phenyl -C ₆₁ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 61} -butyric acid methyl ester = PC 60 BM], (6,6) - phenyl -C ₇₁ -butyric acid methyl ester [(6,6) -phenyl-C ₇₁ -butyric acid methyl ester = PC ₇₀ BM], (6,6) -phenyl-C ₇₇ -butyric acid methyl ester [(6 _{, 6) -phenyl-C 77 -butyric} acid methyl ester = PC 76 BM], (6,6) - phenyl -C ₇₉ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 79} -butyric acid methyl _{ester = PC 78 BM], (} 6,6) - phenyl -C ₈₁ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 81} -butyric acid methyl ester = PC 80 BM], (6,6) -phenyl -C ₈₃ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 83} -butyric acid methyl ester = PC 82 BM], (6,6) - ₈₅ -C-phenyl-butyric rigs Acid methyl ester [ (6,6) -phenyl-C ₈₅ -butyric acid methyl ester = PC ₈₄ BM], and combinations thereof, but is not limited thereto. The semiconducting nanoparticles may include semiconducting nanoparticles such as CdTe and CdTe, but are not limited thereto.

The metal nanoparticles are, for example, gold (Au), silver (Ag), platinum (Pt), palladium (Pd), aluminum (Al), copper (Cu), nickel (Ni), zinc (Zn), Iron (Fe), and may be a metal selected from the group consisting of combinations thereof, but is not limited thereto. In one embodiment, the metal nanoparticles may include octahedron gold (Au) nanoparticles or truncated octahedron gold (Au) nanoparticles. However, the present invention is not limited thereto. In another embodiment, the metal nanoparticles may include silver (Ag) nanoparticles, but is not limited thereto.

The diameter of the metal nanoparticles is about 30 nm to about 90 nm, about 30 nm to about 80 nm, about 30 nm to about 70 nm, about 40 nm to about 90 nm, about 40 nm to about 80 nm, about 40 nm To 70 nm, about 50 nm to about 90 nm, about 50 nm to about 80 nm, or about 50 nm to 70 nm, but is not limited thereto. When the size of the metal nanoparticles is smaller than the above range, the scattering effect is less and the degree of improvement of the efficiency of the organic solar cell manufactured using the same is relatively low. When the size of the metal nanoparticles is about 30 nm to about 90 nm, the scattering effect in the active layer of the organic solar cell is superior to the case where the particles are small. And this is also because the contact surface area between the active layer and the nanoparticles is reduced when the size of the metal nanoparticles is about 30 nm to about 90 nm compared to the case of particle sizes of less than about 10 nm. For example, gold nanoparticles having the size range may have excellent hole conductor, and silver nanoparticles having the size range may have excellent electron conductor, such metal nanoparticles. In the case of the solar cell introduced into the active layer has an improved charge transporting property (charge transporting property) is increased the photoelectric conversion efficiency. This effect can be seen from the UPS measurement results and the analysis results of the decrease in the series resistance and the increase of the photocurrent value in the solar cell in the embodiments according to the present application described below.

In one embodiment of the present application, when the average diameter of the gold nanoparticles when the gold nanoparticles are added to the photoelectric conversion layer as the metal nanoparticles is about 70 nm, the efficiency improvement of the organic solar cell appears most remarkably However, the present invention is not limited thereto.

In another embodiment of the present application, when the silver nanoparticles are about 40 nm in diameter when the silver nanoparticles are added to the photoelectric conversion layer as the metal nanoparticles, the efficiency improvement of the organic solar cell is most remarkable. It is not limited to this.

The amount of the metal nanoparticle may be about 20 wt% or less, about 15 wt% or less, about 10 wt% or less, or 5 wt% or less based on the total weight of the electron donor and the electron acceptor, but is not limited thereto.

The organic solar cell includes a hole transport layer 120 formed between the transparent electrode 110 and the photoelectric conversion layer 130, and an electron transport layer 140 formed between the photoelectric conversion layer 130 and the metal electrode 150. ) May be additionally included, but is not limited thereto.

The hole transport layer 120 may be formed by spin coating, dip coating, Langmere-Bridget, screen printing, or inkjet printing using a polymer dispersion. As the material of the hole transport layer 120, materials known in the art may be used without particular limitation, for example, poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate) {poly (3, 4-ethylenedioxythiophene): poly (strene sulfonate) = PEDOT: may include a dispersion containing a polymer material, such as, but not limited to. The hole transport layer 120 may include molybdenum oxide, titanium oxide, tungsten oxide, or zinc oxide, but is not limited thereto.

The electron transport layer 140 may be formed by spin coating, dip coating, screen printing, ink jet printing, or spraying using a metal precursor sol (or solution). The hole transport layer 120 is titanium oxide (TiOx), tungsten oxide (WOx), zinc oxide (ZnOx), iron oxide (FeOx), copper oxide (CuOx), zirconium oxide (ZrOx), chromium oxide (CrOx), oxide It can be used including those selected from the group consisting of vanadium (VOx), manganese oxide (MnOx), cobalt oxide (CoOx), nickel oxide (NiOx), tin oxide (SnOx), iridium oxide (IrOx), and combinations thereof. However, it is not limited thereto.

The metal electrode 150 may be formed using thermal deposition, chemical vapor deposition, physical vapor deposition, or sputtering, but is not limited thereto. In addition, the metal electrode 150 is aluminum (Al), gold (Au), silver (Ag), platinum (Pt), palladium (Pd), copper (Cu), tungsten (W), iron (Fe), nickel It may be used including those selected from the group consisting of (Ni), zinc (Zn), and combinations thereof.

In the organic solar cell, when the transparent electrode 110 is positioned in the light source direction and the metal electrode 150 is disposed in the opposite direction of the light source, light from the light source may be converted into electricity. In this case, the metal nanoparticles included in the photoelectric conversion layer 130 scatters or reflects the light to increase the movement path of the light, increase the electrical conductivity of the photoelectric conversion layer 130, and generate the electrons. By increasing the movement of the holes, the photoelectric conversion efficiency can be increased.

The photoelectric conversion layer is about 10 nm to about 400 nm, about 10 nm to about 350 nm, about 10 nm to about 300 nm, about 10 nm to about 250 nm, about 10 nm to about 200 nm, about 10 nm to about 150 nm, about 10 nm to about 100 nm, about 30 nm to about 400 nm, about 30 nm to about 350 nm, about 30 nm to about 300 nm, about 30 nm to about 250 nm, about 30 nm to about 200 nm , About 30 nm to about 150 nm, about 30 nm to about 100 nm, about 50 nm to about 400 nm, about 50 nm to about 350 nm, about 50 nm to about 300 nm, about 50 nm to about 250 nm, about 50 nm to about 200 nm, about 50 nm to about 150 nm, about 50 nm to about 100 nm, about 80 nm to about 400 nm, about 80 nm to about 350 nm, about 80 nm to about 300 nm, about 80 nm To about 250 nm, about 80 nm to about 200 nm, about 80 nm to about 150 nm, about 100 nm to about 400 nm, about 100 nm to about 350 nm, about 100 nm to about 300 nm, about 100 nm to about 250 nm, about 100 nm to about 200 nm, about 100 nm to about 150 nm thick Be one having a film form, but is not limited to this. In exemplary embodiments of the present disclosure, the thickness of the photoelectric conversion layer may be about 50 nm to about 400 nm, about 50 nm to about 400 nm for P3HT / PCBM, and about 50 to about 400 nm for PCDTBT / PCBM. 300 nm, in the case of Si-PCPDTBT / PCBM may be about 50 nm to about 300 nm, but is not limited thereto.

In the organic solar cell according to the embodiment of the present application, due to the low mobility of the photoelectric conversion layer, due to the competition between the built-in potential (built-in potential) and the recombination of the photogenerated carrier (film), The thickness is limited. That is, the photoelectric conversion efficiency does not increase in proportion to the increase in the thickness of the photoelectric conversion layer. This is because a recombination phenomenon of a carrier including electrons or holes generated by being excited by light in the photoelectric conversion layer is increased, thereby restricting the movement of the carrier.

In one embodiment of the present application, the organic solar cell according to the present application may be prepared including the following steps:

Forming a transparent electrode on the transparent substrate (S1);

Forming a photoelectric conversion layer on the transparent electrode (S2); And

Forming a metal electrode on the photoelectric conversion layer (S3).

The photoelectric conversion layer is prepared by mixing and dispersing metal nanoparticles in a solution containing an electron donor and an electron acceptor, but is not limited thereto.

First, a transparent electrode is formed on a transparent substrate (S1). The transparent substrate is as described above. The transparent electrode may be formed on the transparent electrode by a conventional thin film forming method such as depositing or coating a transparent conductive metal oxide as described above, or by using an existing ITO or FTO transparent substrate having a transparent electrode formed on an organic substrate. Can be used.

Subsequently, a photoelectric conversion layer is formed on the transparent electrode (S2). The photoelectric conversion layer may be formed by applying a solution formed by adding metal nanoparticles to a solution including an electron donor and an electron acceptor on the transparent electrode and then drying it. The solution may further comprise a solvent. The electron donor, electron acceptor and metal nanoparticles are the same as described above.

The solution containing the electron donor and the electron acceptor is chlorobenzene, 1,2-dichlorobenzene, chloroform, acetone, acetonitrile as the solvent. , Dimethylacetamide (DMAc), dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), methyl ethyl ketone, methyl n-propyl ketone ), N-methylpyrrolidone (NMP), propylene carbonate (propylene carbornate), nitromethane (nitromethane), sulfolane (sulforane), ethylene glycol and hexamethylphosphoramide (hexamethylphophoramide; HMP), but not limited to one or more selected from the group consisting of.

The application process includes one or more selected from the group consisting of dip coating, spray coating, doctor blade coating, gravure coating, screen coating, and combinations thereof, depending on the viscosity of the composition and the components of the composition, It is not limited to this.

After the coating step, if necessary, an additional drying step or heat treatment step may be performed. The drying process or the heat treatment process may be carried out in a hot air oven or an electric furnace, the drying temperature may be about 60 ℃ to about 150 ℃, the heat treatment temperature may be about 80 ℃ to about 200 ℃, but is not limited thereto. no.

Subsequently, a metal electrode is formed on the photoelectric conversion layer (S3). The metal electrode may be formed using thermal deposition, chemical vapor deposition, physical vapor deposition, or sputtering, but is not limited thereto. In addition, the metal electrode may be aluminum (Al), gold (Au), silver (Ag), platinum (Pt), palladium (Pd), copper (Cu), tungsten (W), iron (Fe), nickel (Ni). , Zinc (Zn), and combinations thereof may be used, including those selected from the group.

In addition, the organic solar cell according to the present application may further include a hole transport layer formed between the transparent electrode and the photoelectric conversion layer, and an electron transport layer formed between the photoelectric conversion layer and the metal electrode.

Formation of the hole transport layer may be performed between the S1 and S2. The hole transport layer is the same as described above.

Formation of the electron transport layer may be performed between the S2 and S3. The electron transport layer is the same as described above.

The organic solar cell can be manufactured (S4) by the above production method.

All of the contents described for the organic solar cell according to the exemplary embodiment of the present application may be applied to the method of manufacturing the organic solar cell according to the exemplary embodiment of the present application.

Hereinafter, the present application will be described in more detail with reference to Examples. However, the present application is not limited to these examples.

[ Example ]

< Example  1> Preparation of Gold Nanoparticles

In this example, truncated octahedron gold nanoparticles were prepared as gold nanoparticles as follows. To a 50 ml vial, add 0.09 ml of 94.2 mM HAuCl ₄ · 3H ₂ O aqueous solution and 7.5 ml of dissolved PVP solution at 1.46 mM to DMF, add 2.61 ml of DMF and 1.8 ml of deionized water to add a mixture. Obtained. A magnetic stirring bar was added to the vial containing the mixed solution and sealed, and the vial was put in an oil bath and stirred at 100 ° C. for 2 hours, followed by heating. Subsequently, water and ethanol were added to the vial, redispersed and centrifuged at 12,000 rpm to precipitate the truncated octahedron gold nanoparticles and remove the remaining PVP at least five times.

Figure 3 is a scanning electron micrograph of the gold nanoparticles of the truncated octaheadron structure prepared in this embodiment. In FIG. 2, the average particle diameter of the gold nanoparticles is about 70 nm, and the polyhedron structure is a truncated octahedron.

Figure 4 is a graph of the EDAX (Energy Dispersive Ananysis of X-ray) analysis of the truncated octaheadron gold nanoparticles prepared in this example. When the truncated octaheadron gold nanoparticles were placed on a silicon substrate and subjected to EDAX analysis, it was found that the gold nanoparticles consisted of pure gold.

5 is a UV / Vis-absorption spectrum according to synthesis time when preparing gold nanoparticles prepared in the present example. The shape of the gold nanoparticles varies depending on the reaction time during the preparation of the gold nanoparticles, and the polyhedral structures shown in FIG. ), Rhombic dodecahedron, octahedron, cuboctahedron, and cuboctahedron. Depending on the shape and size of the gold nanoparticles, the wavelength spectrum of the absorbing light is different, and the absorption wavelength spectrum of the leftmost truncated octaheadron gold nanoparticles is represented by a blue line, It is believed to have strong light absorption ability.

FIG. 6 is a UV / Vis-absorption spectrum of (a) truncated octahedron gold nanoparticles prepared in this example and photographs of gold nanoparticles dispersed in solution, and (b) P3HT / PC ₇₀ BM; UV / Vis-absorption spectrum of P3HT / PC ₇₀ BM containing 5% by weight of truncated octahedron gold nanoparticles. In Figure 6 (a) is a vial photograph containing a dispersion containing the truncated octaheadron gold nanoparticles (T-Octa Au), the maximum absorption peak of the T-Octa Au is about 550 nm. Also, in the visible region, the light absorption spectrum of the P3HT / PC ₇₀ BM photoelectric conversion layer (red line) containing 5% by weight of T-Octa Au is not shown in the photoelectric conversion layer (black line) without T-Octa Au. It can be seen that it has a higher intensity (Y-axis) compared to the light absorption spectrum of).

FIG. 7 shows (a) a scanning electron micrograph of synthesized octahedron gold nanoparticles, a gold nanoparticle solution centrifuged, and (b) a gold nanoparticle photograph and UV / Vis- dispersed in a solution. Absorption spectrum. The maximum absorption peak of octahedron gold nanoparticles (Octa Au) is shown at about 603 nm.

< Example  2> Organic Solar Cells Containing Gold Nanoparticles

The glass substrate coated with indium tin oxide (ITO), which is a transparent electrode, is washed with an acetone and alcohol using an ultrasonic cleaner, and the surface of the substrate is hydrophilic by modifying the surface of the substrate with a hydroxyl group using a UV-treatment device. Modified. PEDOT: PSS (Bayer) was applied by spin coating, followed by drying at 140 ° C. for 10 minutes to completely remove the solvent to form a hole transport layer on the transparent electrode.

The following three electron donor / electron acceptor materials were used. In the case of PCDTBT / PC ₇₀ BM, 7 mg of PCDTBT, and 28 mg of PC ₇₀ BM were dissolved in 1 ml of 1,2-dichlorobenzene / chlorobenzene (3: 1) to prepare a mixed solution.

In the case of P3HT / PC ₇₀ BM, 25 mg of P3HT and 15 mg of PC ₇₀ BM were dissolved in 1 ml of chlorobenzene to prepare a mixed solution.

In the case of Si-PCPDTBT / PC ₇₀ BM, 7 mg of Si-PCPDTBT and 14 mg of PC ₇₀ BM were dissolved in 1 ml of 1,2-dichlorobenzene to prepare a mixed solution.

Three kinds of electron donor / electron acceptor materials (P3HT / PC ₇₀ BM, PCDTBT / PC ₇₀ BM, Si-PCPDTBT / PC ₇₀ BM) were added to the electron donor / electron acceptor material solution with about 70 nm of gold (Au) particles. The mixture was prepared by mixing and dispersing in 0 wt% (comparative), 1 wt%, 5 wt%, 10 wt%, and 20 wt%, respectively. The mixture was applied onto the hole transport layer by spin coating in a glove box filled with nitrogen, and then the solvent was completely evaporated to form a photoelectric conversion layer.

Subsequently, a titanium oxide (TiO _x ) layer, which is an electron transporting layer, is applied on the photoelectric conversion layer to less than 10 nm, and an aluminum thin film having a thickness of 100 nm is formed on the electron transporting layer using a thermal deposition method. An organic solar cell was prepared.

Apparatus and Measurement Methods for Experiments

Photo-current density (J-V) curves were measured using Keithley's 2400 model source measuring device and Air mass's solar simulator at 1.5 AM. The image of gold or silver nanoparticles was measured using a scanning electron microscope of Sirion XL 30 model of FEI, and the acceleration voltage was 10 kV to 20 kV. The IPCE of the organic solar cell was measured as a function of the excitation wavelength obtained from a monochromator of Newport's 300 W xenon lamp and Newport's Cornerstone 260 model.

In the measurement using an ultraviolet photoelectron spectroscopy device (UPS), the UPS measurement chamber was used with a hemispherical electron energy analyzer from Kratos Ultra Spectrometer and the pressure was maintained at 1 × 10 ⁻⁹ Torr. UPS measurement is HeI ( hv = 21.2 eV) source. During UPS measurements, the sample bias used for separation of the sample and secondary edges for the analyzer was -9 V.

 In the photovoltaic layer of an organic solar cell containing 5 wt% gold nanoparticles, the increased amount of light absorption increases the UV-absorption and light scattering effects, and the increased external quantum efficiency. Was confirmed. Separately, when the ratio of the metal nanoparticles in the photoelectric conversion layer was less than 1wt%, the results were similar to those of the comparative example, and in the case of 20wt% or more, the overall efficiency of the solar cell was reduced. It can be said that the ratio occupied by has a big influence on the performance increase. The photoelectric conversion layer containing 5wt% gold nanoparticles showed the results depending on the material and the thickness of the photoelectric conversion layer. Observing the image obtained by observing the surface of the photoelectric conversion layer containing gold nanoparticles as shown in Figure 8 using a scanning electron microscope, it was confirmed that the gold nanoparticles are evenly distributed in the region of the photoelectric conversion layer.

Particularly in the case of photoactive layers incorporating relatively large gold nanoparticles, the photoelectric conversion layer containing gold (Au) nanoparticles shows good hole transport properties, as can be seen in FIG. This is because the large metal nanoparticles may exhibit better charge transfer characteristics due to the reduced interface between the photovoltaic layer and the metal particles of the organic solar cell than the small metal nanoparticles.

< Comparative Example  1>

Fabrication of the organic solar cell of Comparative Example 1 is basically the same as that of Example 2, but in the components of the photoelectric conversion layer of the organic solar cell, gold having a size of less than 10 nm in the electron donor / electron acceptor (Au ) Nanoparticles are mixed and dispersed in three electron donor / electron acceptors (P3HT / PC ₇₀ BM, PCDTBT / PC ₇₀ BM, Si-PCPDTBT / PC ₇₀ BM) at the optimum ratio (5% by weight). .

< Comparative Example  2>

Fabrication of the organic solar cell of Comparative Example 2 was basically the same as that of Example 2, but in the constituent components of the photoelectric conversion layer of the organic solar cell, only the electron donor / electron acceptor was used without adding gold nanoparticles.

In Table 1 below, the energy conversion efficiency (%), short circuit current density (mA / cm ² ), open circuit voltage (V), and fill factor of the solar cells of Example 2, Comparative Example 1, and Comparative Example 2 are shown.

division Example 2
(70 nm Au NPs ) Comparative Example  One
(~ 10 nm Au NPs ) Comparative Example 2
( Ref . Cell ) Energy conversion efficiency (%) 6.5% 5.9% 5.8% Short circuit current density mA / cm ² ) 11.2 10.50 10.29 Open circuit voltage (V) 0.90 0.89 0.88 Fill factor 0.65 0.63 0.64

The characteristics of the organic solar cell to which gold nanoparticles are added to the photoelectric conversion layer will be described in more detail with reference to FIGS. 8 to 17.

FIG. 8 is a scanning electron micrograph of a photoelectric conversion layer (P3HT / PC ₇₀ BM) containing 5 wt% of the truncated gold nanoparticles used in the embodiment and a polyhedral structure of the truncated gold nanoparticles. It can be seen that the gold nanoparticles are dispersed very uniformly and densely in the photoelectric conversion layer.

9 shows the structure of PCDTBT, Si-PCPDTBT and P3HT as electron donors used in the above examples, and PC ₇₀ BM (PCBM) used as electron acceptors. PCDTBT appears to be deeply related to the HOMO energy of 5.5 eV coupled to the high open-circuit voltage. The P3HT and Si-PCPDTB have crystallinity, and the PCDTBT is amorphous. On the other hand, the Si-PCPDTBT is a material having a low band gap, and compared with the PCDTBT and P3HT, which absorbs a wavelength of about 300 nm to 800 nm, it can absorb a wavelength of about 1,100 nm region It is a substance.

FIG. 10 is an IPCE analysis of an organic solar cell containing 5 wt% of the truncated octaheadron gold nanoparticles used in the above example and an organic solar cell not containing the gold nanoparticles. ) P3HT, (b) PCDTBT, and (c) Si-PCPDTBT. In the incident photon-to-current efficient (IPCE) spectral results of the photovoltaic layer cell containing the truncated octahedron gold nanoparticles, individual efficient light scattering from the gold nanoparticles and There is an improved charge transfer enhancement.

11 is a graph of current density (J) -voltage (V) of an organic solar cell containing 5 wt% of the truncated octaheadron gold nanoparticles used in the above example and an organic solar cell containing no gold nanoparticles. Electron donor materials are (a) PCDTBT and (b) Si-PCPDTBT. For (a) the thickness of the layer containing PCDTBT and PC ₇₀ BM is about 120 nm, and for (b) the thickness of the layer containing Si-PCPDTBT and PC ₇₀ BM is about 150 nm.

FIG. 12 contains 0 wt%, 1 wt%, 5 wt%, 10 wt%, and 20 wt% of the truncated octahedron gold nanoparticles (T-Octa) used in the above examples, respectively. It is a current density (J) -voltage (V) graph of an organic solar cell manufactured using a photoelectric conversion layer including PC ₇₀ BM. In the case of the above 0% by weight, it is the same as the reference Ref (BHJ). As a result of the current density-voltage graph, it is determined that the photoelectric conversion performance of the photoelectric conversion layer containing 5 wt% to 10 wt% of T-Octa is the best.

FIG. 13 is a current density (J) -voltage (V) graph of an organic solar cell containing 5 wt% of the truncated octaheadron gold nanoparticles used in the above example or no containing gold nanoparticles, and FIG. Donor materials are (a) P3HT, (b) PCDTBT, and (c) Si-PCPDTBT. The increased J shows that much light has been harvested in the photoelectric conversion layer due to the large number of light scattering by the gold nanoparticles. In the organic solar cell according to the embodiment, the light absorption cannot be directly determined because the aluminum cathode is not transparent. Therefore, the prevailing reflection spectrum was measured and shown in FIG.

FIG. 14 is a diffraction reflectance-wavelength (λ) graph of an organic solar cell containing 5 wt% of the truncated octaheadron gold nanoparticles or no gold nanoparticles in the present embodiment. It showed widespread reflection spectra on P3HT / PC ₇₀ BM devices with or without gold nanoparticles. The lowest reflectivity of devices containing gold nanoparticles suggests strong absorption of incident light.

The gold nanoparticles used in this example were predicted to have a work function of 5.1 eV (close to 5.2 eV, the energy HOMO energy level of P3HT), and thus resulted in a small energy barrier for hole emission.

15 is an energy band diagram of an organic solar cell containing (a) gold nanoparticles having an average size of 10 nm or less in a photoelectric conversion layer including P3HT / PC ₇₀ BM in the above embodiment, (b) P3HT / PC An energy band diagram of an organic solar cell containing 70 nm gold nanoparticles having an average size of 70 nm in a photoelectric conversion layer containing ₇₀ BM, (c) UPS spectrum, and (d) energy band of each component.

As shown in FIGS. 15A and 15B, because the holes move along the interface, the interface of the system containing the large gold nanoparticles is smaller than that of the system containing the relatively small gold nanoparticles, thereby reducing the parallel resistance. You can.

Ultraviolet photoelectron spectroscopy (UPS) was used to measure the energy levels of layers mixed with gold nanoparticles.

FIG. 15C is a UPS spectrum in the above embodiment, which is a photoelectric conversion layer containing 1) ITO, 2) a photoelectric conversion layer containing P3HT / PC ₇₀ BM, and 3) gold nanoparticles with an average size of 70 nm. UPS results of ITO (black) used as a reference substrate, P3HT / PC ₇₀ BM (blue) as the photoelectric conversion layer material, and P3HT / PC ₇₀ BM (red) containing gold nanoparticles were shown.

Figure 15d is a diagram of energy _{and, P3HT / PC 70 BM, P3HT} / PC containing the gold nano-particles ₇₀ BM, and ITO in the above embodiment.

In FIGS. 15C and 15D, irradiation of the secondary electron blocking region allows extraction of a shift in the vacuum energy level E _VAC ; E _VAC shift was measured for the magnitude of the interfacial dipole. Deposition of the mixed layer was shifted towards high binding energy. The mixture HOMO energy level (E _HOMO ) was determined using a small binding energy region (0-3 eV). The hole injection barrier Φ _h is the energy difference between E _HOMO and zero binding energy (related to the work function of the ITO substrate). The hole injection barrier Φ _h of P3HT / PC ₇₀ BM was 0.45 eV. Therefore, the introduction of gold nanoparticles reduces Φ _h by 0.1 eV. This small Φ _h can apply cascade hole transfer from HOMO energy from P3HT to the ITO electrode; Efficient hole extraction can reduce the likelihood of electron / hole recombination, resulting in an increase in V _OC .

In FIGS. 15A-15D, enhanced FF and black IV characteristics were observed and verified. Since the current of the device containing black gold nanoparticles shows a significant increase in shunt resistance, the result at the short-circuit current is higher than that of the reference device. More huge Reduced leakage current is a key factor in improving device performance. In addition, the parallel resistance of the PCDTBT / PC ₇₀ BM device without the gold nanoparticles was 1.86 Ωcm ² , and when the gold was added, the parallel resistance was 1.49 Ωcm ² , and the parallel resistance of the Si-PCPDTBT / PC ₇₀ BM device was 2.54 Ωcm ² . When gold was added, it became 2.18 cm ² . To the reduced parallel resistance, PCDTBT / from a PC ₇₀ BM FF is at 0.64 0.65, Si-PCPDTBT / from the PC ₇₀ BM increased from 0.63 to 0.64.

FIG. 16 is an energy band diagram of an organic solar cell including ITO / PEDOT: PSS / electron donor / PC ₇₀ BM / TiOx / Al in the above embodiment. The case where the electron donors are P3HT, Si-PCPDTBT, and PCDTBT is shown in different colors. The organic solar cell having the electron donor P3HT has a band gap between 3.3 eV and 5.2 eV, the organic solar cell having Si-PCPDTBT has a band gap between 3.31 eV and 4.8 eV, and the organic solar cell having PCDTBT has 3.6 eV and It has a bandgap between 5.5 eV.

FIG. 17 is a graph showing organic solar cell efficiency depending on thickness, gold nanoparticle content, and photoelectric conversion layer material in the above embodiment. In FIG. 17, the maximum thickness of the organic solar cell having the black P3HT / PC ₇₀ BM photoelectric conversion layer was about 220 nm, and the efficiency at that time was about 3.7%. The addition increased to about 4.4%. The maximum thickness of the organic solar cell with the red PCDTBT / PC ₇₀ BM photoelectric conversion layer was about 90 nm, and the efficiency was about 6.1%. However, when the 5 wt% gold nanoparticles were added, the efficiency was It improved to about 6.6%. The maximum thickness of the organic solar cell having a blue Si-PCPDTBT / PC ₇₀ BM photoelectric conversion layer was about 120 nm, and the efficiency at that time was about 4.2%, but when 5 wt% gold nanoparticles were added, This improved to 4.7%.

In the organic solar cell according to the embodiment, a photoelectric conversion layer comprising a P3HT / PC ₇₀ BM, PCDTBT / PC ₇₀ BM, Si-PCPDTBT / PC ₇₀ BM of gold nanoparticles having a relatively large size (70 nm) The introduction of has had several positive effects. Gold nanoparticles with a truncated octahedron structure were synthesized by solution chemistry. The optimum concentration of gold nanoparticles was about 5% by weight, and when the truncated octaheadron gold nanoparticles were added to the photoelectric conversion layer, J, FF, and IPCE increased. These improvement results are due to the presence of gold nanoparticles in the photoelectric conversion layer, the light is scattered, thereby increasing the light absorption in the photoelectric conversion layer. However, the light concentration exerted by plasmons was not observed at certain wavelengths. In addition, the improved charge transfer results lowered the parallel resistance. In the organic solar cell including the photoelectric conversion layer according to the present application, gold nanoparticles are included in the photoelectric conversion layer to maximize the PCE value as follows. When the photoelectric conversion layer was P3HT / PC ₇₀ BM, it was 3.5% when no gold nanoparticles were included in the photoelectric conversion layer, but 4.4% was recorded when the gold nanoparticles were included. When the photoelectric conversion layer was PCDTBT / PC ₇₀ BM, it was 5.8% when no gold nanoparticles were included in the photoelectric conversion layer, but 6.5% was recorded when the gold nanoparticles were included. When the photoelectric conversion layer was Si-PCPDTBT / PC ₇₀ BM, it was 3.9% when no gold nanoparticles were included in the photoelectric conversion layer, but when the gold nanoparticles were included, 4.5% was recorded. The improvement of the PCD value depends on the size of the gold nanoparticles, and there seems to be an optimum content of the gold nanoparticles in the photoelectric conversion layer.

The plasmon resonance of the octahedron gold nanoparticles was 603 nm and the plasmon resonance of the truncated octahedron gold nanoparticles was 530 nm. Organic solar cells using 70 nm octahedral gold nanoparticles and organic solar cells using truncated octahedral gold nanoparticles showed similar trends in PCE enhancement and broad band response. From the plasmon response of narrow bands, local field enhancement is not a dominant mechanism. Multiple scattering led to a long light path in the photoelectric conversion layer, indicating an improvement in PCE.

< Example  3> Preparation of Silver Nanoparticles

3.0 ml of an aqueous solution of AgNO ₃ dissolved in 94 mM concentration, 3.0 ml of an aqueous solution of polyvinylpyrrolydone (PVP) dissolved in 147 mM concentration, and 6 ml of polyol were mixed in a vial, Heat of 140 ° C. was applied for 1 hour. AgNO ₃ was used as a precursor of silver nanoparticles and PVP was used as a surfactant. Controlling the size of the silver nanoparticles includes 1,2-propanediol (1,2-propanediol, PrD), 1,4-butanediol (1,4-butanediol, BD), and 1,5-pentanediol (1 Three kinds of polyols were used, 5-pentanediol and PtD). The smallest nanoparticles were synthesized in the most viscous medium. The viscosity of the polyols increased in order of PrD <BD <PtD as the hydrocarbon chain became longer. The size of the synthesized nanoparticles decreases in the order of PrD (60 nm)> BD (40 nm)> PtD (30 nm). The synthesized silver nanoparticles were obtained by adding water and ethanol to the synthesized solution and centrifuging.

FIG. 18 is a scanning electron micrograph of silver nanoparticles prepared by NaBH ₄ in a dispersion medium containing polyol in this embodiment, wherein the polyol is (a) ethylene glycol (EG), (b) 1,2 Propanediol (1,2-propanediol, PrD), (c) 1,4-butanediol (1,4-butanediol, BD), (d) 1,5-pentanediol (1,5-pentanediol, PtD) If it is. In the case of (a), (b), (c), and (d), the size of each particle was 20 ± 9 nm, 17 ± 5 nm, 12 ± 3 nm, 5 ± 1 nm.

FIG. 19 shows a scanning electron micrograph and particle size distribution of silver nanoparticles prepared in a dispersion medium of polyol in the present embodiment, wherein the polyol is (a) ethylene glycol (EG), (b) 1, 2-propanediol (1,2-propanediol, PrD), (c) 1,4-butanediol (1,4-butanediol, BD), (d) 1,5-pentanediol (1,5-pentanediol, PtD) If In the case of (a), (b), (c), and (d), the size of each particle was 144 ± 50 nm, 61 ± 20 nm, 42 ± 11 nm, 30 ± 5 nm.

< Example  4> Organic Solar Cells Containing Silver Nanoparticles

An organic solar cell based on mixing PCDTBT / PC ₇₀ BM and silver nanoparticles is shown in FIG. 28. ITO-based impurities were removed by the washing process. After exposing the ITO substrate to UV for 15 minutes to modify the surface, the hole transport layer PEDOT: PSS was spin-coated on the ITO substrate to a thickness of 35 nm and then heat-treated at 140 ° C. for 10 minutes. On the PEDOT: PSS, the liquid mixture is spin coated to form a photoelectric conversion layer having a thickness of 80 nm. The composition of the liquid mixture is PCDTBT / PC ₇₀ in a mixed solvent of 1,2-dichlorobenzene / chlorobenzene mixed at 3: 1. 0.2 wt%, 1 wt%, and 2 wt% of silver nanoparticles were added to the BM melted at a ratio of 1: 4. The substrate was then dried at 80 ° C. for 10 minutes in a glove box. On the PCDTBT / PC ₇₀ BM photoelectric conversion layer, TiOx, an electron transporting layer, was spin-coated at 5000 rpm for 40 seconds to have a thickness of 10 nm, and the aluminum electrode was thermally evaporated under a pressure of 4.0 Ⅹ 10 ^-6 Torr. Formed to a thickness of 100 nm.

Apparatus and Measurement Methods for Experiments

The photo-current density (JV) curve of the formed organic solar cell was measured at an intensity of 1000 W / m ² using a source measuring device of Keithley's 236 model and a solar simulator manufactured by Air Mass at 1.5 AM. In order to secure the accuracy of the organic solar cell area, an aperture of 9.84 mm ² was used on the top of the organic solar cell. Surface morphology was analyzed using AFM (Veeco, USA; D3100) and scanning electron microscope (Model Sirion XL 30 from FEI).

20 are scanning electron micrographs of silver nanoparticles synthesized in various sizes by using the chemical structure of PCDTBT and PC ₇₀ BM used in this example, a schematic diagram of an organic solar cell, and a polyol process. The organic solar cell includes an ITO transparent electrode, a PEDOT: PSS hole transport layer on the transparent electrode, a photoelectric conversion layer containing PCDTBT / PC ₇₀ BM and silver nanoparticles on the hole transport layer, a TiOx electron transport layer on the photoelectric conversion layer, and the It was formed in the order of the aluminum metal electrode on the electron transport layer. 20 shows scanning electron micrographs of silver nanoparticles having an average size of about 30 nm, about 40 nm, and about 50 nm from the top, respectively.

FIG. 21 shows the results of UV / Vis spectra analysis in this example, wherein the targets of the graphs are (a) silver nanoparticles having a diameter of 30 nm, 40 nm, and 60 nm, and (b) silver nanoparticles having a diameter of 40 nm. Corresponding to the photoelectric conversion layer containing PCDTBT / PC ₇₀ BM containing 1% or does not contain the silver nanoparticles. The UV / Vis spectrum of silver nanoparticles with a size of about 60 nm was found to occupy the largest area. It was shown that the photoelectric conversion layer containing silver nanoparticles having a size of about 40 nm has a higher light absorption intensity than the photoelectric conversion layer containing no silver nanoparticles. Also shown in FIG. 21B is a schematic diagram of silver nanoparticles contained in the photoelectric conversion layer forming clusters to scatter or reflect light.

22 is an AFM photograph of the surface of the photovoltaic layer for an organic solar cell manufactured according to an embodiment of the present application, the upper left side of the photoelectric conversion layer containing PCDTBT / PC ₇₀ BM, the upper right side of the 40 nm diameter A photoelectric conversion layer containing 1% by weight of silver nanoparticles, the lower left is a low-resolution photograph of the photoelectric conversion layer containing 1% by weight of silver nanoparticles having a 40 nm diameter, and the lower right side has 1 weight of silver nanoparticles having a 40 nm diameter It is a high resolution photograph of a photoelectric conversion layer containing%.

FIG. 23 illustrates an organic solar cell including 1 wt% of silver nanoparticles having a diameter of 30 nm, 40 nm, and 50 nm, and an organic solar cell not containing the silver nanoparticles, respectively, according to an embodiment of the present disclosure. ) Current density (J) -voltage (V) graph, (b) EQE enhancement and EQE spectrum for each wavelength of a photoelectric conversion layer containing 1 wt% of silver nanoparticles of 40 nm diameter, (c) UPS spectrum, (d) Energy diagram. In FIG. 23A, the object is a photoelectric conversion layer containing PCDTBT / PC ₇₀ BM, containing 30 nm diameter silver nanoparticles in the photoelectric conversion layer, and 40 nm diameter silver nanoparticles in the photoelectric conversion layer. And silver nanoparticles having a diameter of 60 nm in the photoelectric conversion layer. The largest current density in the negative direction was found to be a photoelectric conversion layer containing 40 nm diameter silver nanoparticles. FIG. 23B shows the EQE improvement of the silver nanoparticle clusters formed inside the photoelectric conversion layer. In FIG. 23C, the strength of the binding energy was greater in the sample containing silver nanoparticle clusters. In FIG. 23D, E _vac denotes a vacuum level, E _F denotes a Fermi level, Δ denotes an interfacial dipole, and Φ _h denotes a hole injection barrier. According to the energy band theory, electrons and holes excited by light in the photoelectric conversion layer may cross the energy band difference shown in FIG. 34 and finally generate a voltage difference between the ITO transparent electrode and the aluminum metal electrode, and photoelectric conversion The inclusion of silver nanoparticle clusters in the layer results in a higher LUMO, resulting in a change in the hole injection barrier.

In conclusion, PCDTBT / PC ₇₀ BM has several positive effects in the organic solar cell including the photoelectric conversion layer containing the nanoparticle cluster. Silver nanoparticles were synthesized by solution polyol chemistry processes in various sizes, which were carried out by controlling the reactants and reaction conditions. When spincasting the photoelectric conversion layer, silver nanoparticles aggregated to form clusters. Silver nanoparticle clusters improve the voltage (V), current (J), FF, and EQE of organic solar cells. These results result from improved light absorption. Improved charge transfer resulted in an increase in J value and a decrease in resistance. Finally, when the 1 nm by weight of the cluster consisting of 40 nm silver nanoparticles are included in the photoelectric conversion layer, the photoelectric conversion efficiency of the organic solar cell including the photoelectric conversion layer increased from 6.3% to 7.1%.

It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

110: transparent electrode
120: hole transport layer
130: photoelectric conversion layer
140: electron transport layer
150: metal electrode

Claims (15)

A transparent electrode and a metal electrode disposed to face each other; And
It includes a photoelectric conversion layer positioned between the transparent electrode and the metal electrode,
The photoelectric conversion layer includes metal nanoparticles dispersed in a blend of an electron donor and an electron acceptor,
The metal nanoparticles contain more than 2% by weight to 20% by weight with respect to the total weight of the photoelectric conversion layer, thereby increasing the amount of light generated by increasing the amount of light absorption and bringing improved charge transfer characteristics. To increase the efficiency of,
Organic solar cell.
The method of claim 1,
The electron donor comprises a conductive organic polymer,
The electron acceptor includes a fullerene compound, a perylene compound, or semiconducting nanoparticles,
The conductive organic polymer and the fullerene-based compound is to form a bulk heterojunction (bulk heterojunction = BHJ), an organic solar cell.
3. The method of claim 2,
The conductive organic polymer is an organic solar cell comprising an amorphous organic polymer.
The method of claim 1,
The metal nanoparticles are gold (Au), silver (Ag), platinum (Pt), palladium (Pd), aluminum (Al), copper (Cu), nickel (Ni), zinc (Zn), iron (Fe), And metals selected from the group consisting of combinations thereof.
The method of claim 1,
An organic solar cell having a diameter of the metal nanoparticles of 30 nm to 90 nm.
3. The method of claim 2,
The conductive organic polymer was poly-3-hexylthiophene (poly-3-hexylthiophene = P3HT), poly (N-9 "-hepta-decanyl-2,7-carbazole-al-5,5- (4 '). , 7'-di-2-thienyl-2 ', 1', 3 ')-benzothiadiazole) {poly (N-9 "-hepta-decanyl-2,7-carbazole-alt-5,5 -(4 ', 7'-di-2-thienyl-2', 1 ', 3')-benzothiadiazole) = PCDTBT}, poly [(4,4'-bis (2-ethylhexyl) dithieno [3 , 2-b: 2 ', 3'-d] silol) -2,6-diyl-alt- (4,7-bis (2-thienyl) -2,1,3-benzothiadiazole) -5 , 5'-diyl {poly [(4, 4'-bis (2-ethylhexyl) dithieno [3,2-b: 2 ', 3'-d] silole) -2,6-diyl-alt- (4, 7-bis (2-thienyl) -2,1,3-benzothiadiazole) -5,5'-diyl = Si-PCPDTBT}, and an organic solar cell comprising one selected from the group consisting of combinations thereof. .
3. The method of claim 2,
The fullerene-based compound (6,6) -phenyl -C ₆₁ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 61} -butyric acid methyl ester = PC 60 BM], (6,6) - phenyl -C ₇₁ -butyric acid methyl ester [(6,6) -phenyl-C ₇₁ -butyric acid methyl ester = PC ₇₀ BM], (6,6) -phenyl-C ₇₇ -butyric acid methyl ester [(6 _{, 6) -phenyl-C 77 -butyric} acid methyl ester = PC 76 BM], (6,6) - phenyl -C ₇₉ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 79} -butyric acid methyl _{ester = PC 78 BM], (} 6,6) - phenyl -C ₈₁ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 81} -butyric acid methyl ester = PC 80 BM], (6,6) -phenyl -C ₈₃ - butyric rigs Acid methyl ester _{[(6,6) -phenyl-C 83} -butyric acid methyl ester = PC 82 BM], (6,6) - ₈₅ -C-phenyl-butyric rigs Acid methyl ester [ (6,6) -phenyl-C ₈₅ -butyric acid methyl ester = PC ₈₄ BM], and combinations thereof.
delete delete The method of claim 1,
The metal nanoparticles include octahedron gold (Au) nanoparticles (nanoparticle) or truncated octahedron gold (Au) nanoparticles (nanoparticle), the organic solar cell.
The method of claim 1,
The metal nanoparticles will include silver (Ag) nanoparticles, organic solar cells.
The method of claim 1,
An organic solar cell further comprising a hole transport layer formed between the transparent electrode and the photoelectric conversion layer, and an electron transport layer formed between the photoelectric conversion layer and the metal electrode.
The method of claim 1,
The photovoltaic layer is an organic solar cell having a thin film form of 10 nm to 200 nm thickness.
Forming a transparent electrode on the transparent substrate;
Forming a photoelectric conversion layer on the transparent electrode; And
Forming a metal electrode on the photoelectric conversion layer;
The photoelectric conversion layer is prepared by mixing and dispersing metal nanoparticles in a solution containing an electron donor and an electron acceptor,
The metal nanoparticles are more than 2% to 20% by weight based on the total weight of the photoelectric conversion layer,
Due to the metal nanoparticles contained in the photoelectric conversion layer to increase the amount of light generated by increasing the amount of light absorption, and to bring improved charge transfer characteristics to increase the efficiency of the organic solar cell,
The method of manufacturing an organic solar cell according to any one of claims 1 to 7 and 10 to 13.
15. The method of claim 14,
The solution containing the electron donor and the electron acceptor is chlorobenzene, 1,2-dichlorobenzene, chloroform, acetone, acetonitrile, dimethyl as a solvent. Dimethylacetamide (DMAc), dimethyl formamide (DMF), dimethyl sulfoxise (DMSO), methyl ethyl ketone, methyl n-propyl ketone, N-methylpyrrolidone (NMP), propylene carbonate (propylene carbornate), nitromethane, sulfolane, sulforane, ethylene glycol and hexamethylphophoramide (HMP) Comprising one or more selected from the group consisting of, Organic solar cell manufacturing method.

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