KR20120137837A - Middle band type organic solar cell by using metal oxide quantum dot and method of producing the same - Google Patents

Abstract

PURPOSE: A middle band organic solar cell using a metal oxide quantum dot and a manufacturing method thereof are provided to improve photoelectric conversion efficiency by controlling the size of a quantum dot or materials. CONSTITUTION: A p-type polycrystal ZnO(zinc oxide) layer(200) is formed on a substrate. A polyimide layer is formed on the p-type polycrystal ZnO layer. An n-type polycrystal ZnO layer(600) is formed on the polyimide layer. An electrode(700) is formed on the n-type polycrystal ZnO layer. The polyimide layer comprises a metal oxide quantum dot.

Description

Middle band type organic solar cell by using metal oxide quantum dots and method for producing the same

The present invention relates to an intermediate band organic solar cell, and more particularly to an intermediate band organic solar cell using a metal oxide quantum dot and a method of manufacturing the same.

Solar cells have been attracting attention for replacing fossil fuels over the last few decades by producing electricity from solar energy, an infinite source of energy.

Single-crystal silicon solar cells achieve high efficiencies of more than 25%, but their production costs and energy consumption during manufacturing are very high. This is because single-bandgap solar cells with photoelectric conversion efficiencies up to 31% are lost to heat due to electron-phonon scattering in the semiconductor bandgap. Therefore, interest in the development of high efficiency solar cells has increased.

Recently, the middle band solar cell using quantum dots has been actively researched as a third generation high efficiency solar cell. The intermediate band (IB) is formed by injecting quantum dots or impurities into a host material having a wide band gap. The position of the energy level at which the intermediate band system is formed is determined by the injected quantum dots or impurities, and the photoelectric conversion efficiency is determined by the position of the intermediate band system formed. In other words, the use of smaller sized quantum dots absorbs shorter wavelength bands, while the larger sized quantum dots absorb longer wavelengths. Therefore, by combining quantum dots of different sizes in one solar cell, more light is absorbed and thus higher photoelectric conversion efficiency can be obtained than in general bulk compound semiconductors.

However, in the case of the conventional quantum dot solar cell, there is no obvious improvement in efficiency. In addition, when the quantum dot injection density is high, the electrical properties of the host material tend to be lowered. Therefore, an attempt to form an intermediate band system by impurity implantation of a smaller size is required.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide an intermediate band organic solar cell using a polyimide layer including a polycrystalline ZnO layer and a metal oxide quantum dot to improve photoelectric conversion efficiency.

One aspect of the present invention to achieve the above technical problem is a substrate; A p-type polycrystalline ZnO layer formed on the substrate; A polyimide layer formed on the p-type polycrystalline ZnO layer; An n-type polycrystalline ZnO layer formed on the polyimide layer; And an electrode formed on the n-type polycrystalline ZnO layer, and the polyimide layer provides an intermediate band organic solar cell including metal oxide quantum dots.

The substrate may be a single crystal Si substrate, a polycrystalline Si substrate, an ITO substrate, a sapphire substrate or a glass substrate.

The p-type polycrystalline ZnO layer or the n-type polycrystalline ZnO layer may include a nanorod structure.

The p-type polycrystalline ZnO layer may have a thickness of 50 nm to 300 nm.

The polyimide layer may include BPDA-PDA, PMDA-PDA, ODPA-PDA, 6FDA-PDA, BTDA-ODA, DMAc, BDSDA-ODA, DSDA, BPDA-Bz, TMA-PPD or ODA-PI.

The metal oxide quantum dots include In ₂ O ₃ , CuO, Cu ₂ O ₃ , PbO, Bi ₁₂ SiO ₂₀ , ZnO ₂ , SnO ₂ , GaO, MgO, GeO, BaO, SrO, Bi ₁₂ GeO ₂₀ , Bi ₁₂ SiO ₂₀ , It may include at least one selected from Cd ₂ SnO ₄ , CdSnO ₃ and Li ₃ CuO ₃ .

The metal oxide quantum dot may have a diameter of about 1 nm to about 100 nm.

The metal oxide quantum dots may be formed in a multilayer of two or more layers.

The metal oxide quantum dot may be a tandem structure in which heterogeneous materials are stacked.

The electrode may be an ITO electrode.

Another aspect of the present invention to achieve the technical problem is preparing a substrate; Forming a p-type polycrystalline ZnO layer on the substrate; Forming a metal thin film on the p-type polycrystalline ZnO layer; Forming a polyimide layer on the metal thin film; Drying the polyimide layer formed on the metal thin film to melt the metal thin film and generate metal ions; Heat treating the polyimide layer and forming metal oxide quantum dots in the polyimide layer through chemical reaction with the generated metal ions; Forming an n-type polycrystalline ZnO layer on the polyimide layer including the metal oxide quantum dots; And it provides a method for manufacturing an intermediate band-based organic solar cell comprising the step of forming an electrode on the n-type polycrystalline ZnO layer.

Before forming the n-type polycrystalline ZnO layer, the step of forming a polyimide layer containing the metal oxide quantum dots from the step of forming a metal thin film on the p-type polycrystalline ZnO layer is repeated two or more times. You can do

The metal thin film may be Zn, In, or Cu.

Another aspect of the present invention to achieve the technical problem is preparing a substrate; Forming a p-type polycrystalline ZnO layer on the substrate; Patterning an upper portion of the p-type polycrystalline ZnO layer to form a p-type polycrystalline ZnO layer patterned thereon; Forming a metal thin film on the upper patterned p-type polycrystalline ZnO layer; Forming a polyimide layer on the metal thin film; Drying the polyimide layer formed on the metal thin film to melt the metal thin film and generate metal ions; Heat treating the polyimide layer and forming metal oxide quantum dots in the polyimide layer through chemical reaction with the generated metal ions; Forming an n-type polycrystalline ZnO thin film on the polyimide layer including the metal oxide quantum dots; And it provides a method for manufacturing an intermediate band-based organic solar cell comprising the step of forming an electrode on the n-type polycrystalline ZnO thin film.

As described above, according to the present invention, a photoelectric conversion efficiency may be improved by using an intermediate band organic material solar cell using a quantum well structure having a multilayer structure using a polycrystalline ZnO thin film and a metal oxide quantum dot.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1A to 1F are perspective views illustrating a method of manufacturing an intermediate band organic solar cell using a metal oxide quantum dot according to an embodiment of the present invention according to a process step.
2 is a perspective view of an intermediate band organic solar cell using metal oxide quantum dots formed on a patterned p-type polycrystalline ZnO layer according to an embodiment of the present invention.
3 is a cross-sectional image of a polyimide layer including In ₂ O ₃ nanoparticles on a ZnO polycrystalline thin film.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Like numbers refer to like elements throughout. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Example  One

1A to 1F are perspective views illustrating a method of manufacturing an intermediate band organic solar cell including a metal oxide quantum dot according to an embodiment of the present invention, according to process steps.

 Referring to FIG. 1A, a substrate 100 is prepared. The substrate 100 may be a single crystal Si substrate, a polycrystalline Si substrate, an Induim Tin Oxide (ITO) substrate, a sapphire substrate, or a glass substrate. However, the present invention is not limited thereto.

A p-type polycrystalline ZnO layer 200 is formed on the substrate 100.

The p-type polycrystalline ZnO layer 200 may have a thickness of 50 nm to 300 nm. However, the present invention is not limited thereto. If the thickness of the p-type polycrystalline ZnO layer is less than 50 nm, a problem arises in that excitons are not sufficiently formed due to the thin film quality. In addition, when the thickness of the p-type polycrystalline ZnO layer is more than 300 nm, the formed excitons are not sufficiently transferred to the electrode, and a problem arises of recombination within the bulk of the crystal structure.

For example, N ₂ , NO, N ₂ O, NH ₃ or Zn ₃ N ₄ on an ITO transparent electrode substrate. The p-type ZnO polycrystalline thin film may be formed to a thickness of about 200 nm through a sputtering method or a pulsed laser deposition (PLD) method in a gas atmosphere.

In conventional silicon and compound semiconductor solar cells, ZnO with an energy bandgap of 3.4 eV served only as a window. However, the present invention serves to increase the efficiency of the quantum dot mid band solar cell rather than the window role. That is, the ZnO thin film is used to absorb sunlight in the ultraviolet region to form excitons to generate electromotive force. In addition, the ZnO thin film in the present invention is characterized by having a polycrystalline structure instead of a single crystal structure.

The single crystal p-type ZnO thin film requires a high temperature heat treatment process of 500 ° C. or higher, but the polycrystalline p-type ZnO thin film has a substrate temperature of 100 ° C. to 500 ° C.

In order to prevent the substrate temperature from rising, the substrate may be rotated at 7 times / minute to 12 times / minute to maintain the substrate temperature at 100 ° C to 500 ° C. If the number of revolutions of the substrate is less than 7 times / min, there is a fear that the polycrystalline ZnO thin film of the vertical structure is not formed, and if more than 12 times / min can be produced in the form of a nanorod bend the ZnO polycrystalline thin film. When the substrate is rotated more than 12 times / minute, a large amount of voids or pinholes are formed in the polycrystalline thin film, and thus leakage current may be generated to reduce the photoelectric conversion efficiency.

N ₂ , NO, N ₂ O, NH ₃ , or Zn ₃ N ₄ injected The gas may be between 2 sccm and 10 sccm. If the gas is less than 2 sccm, there is a concern that doping may not be sufficient in the polycrystalline ZnO thin film due to insufficient ionization when using an active plasma using sputtering. In addition, when the gas is 10sccm or more, the doping concentration is increased to 1x10 ¹⁸ cm ^-3 or more, which is because the excessive holes are formed, pn junction characteristics are not suitable as a solar cell. The same applies to the case where a p-type ZnO polycrystalline thin film is formed using PLD.

Referring to FIG. 1B, a metal thin film 300 is formed on the p-type polycrystalline ZnO layer 200.

The metal thin film 300 may be Zn, In, or Cu. However, the present invention is not limited thereto. The thickness of the metal thin film 300 may be 5 nm to 10 nm.

If the thickness of the metal thin film 300 is greater than 10 nm, some of the metal thin film 300 may remain as a metal thin film without being dissolved in the chemical reaction with the polyimide layer described later.

Referring to FIG. 1C, a polyimide layer 400 is formed on the metal thin film 300.

The polyimide layer is BPDA-PDA (poly (p-phenylene biphenylene carboximide)), PMDA-PDA (poly (p-phenylene pyromellitimide)), ODPA-PDA (poly (p-phenylene 3,3 ', 4,4' -oxydiphthalimide)), 6FDA-PDA (poly (p-phenylene 4,4'-hexafluoro isopropylidene diphthalimide)), BTDA-ODA (3,3 ', 4,4'-Benzophenonetetracarboxylic dianhydride-4,4'-oxydianiline), Dimethylacetamide (DMAc), BDSDA-ODA (4,4'-bis (3,4-dicarboxyphenoxy) diphenylsulfide-oxydianhydride), DSDA (3,3 ', 4,4'-diphenylsulfone tetracarboxylic acid dianhydride), BPDA-Bz (poly (4,4'-biphenylene biphenyltetracarboximide), trimellitic anhydride-p-phenylene diamine (TMA-PPD) or ODA-PI (4,4'-oxydianiline-polyimide).

The polyimide layer 400 may have a thickness of 50 nm to 100 nm. However, the present invention is not limited thereto.

For example, the polyimide layer may be formed by spin coating BPDA-PDA on the Cu metal thin film.

Referring to FIG. 1D, metal oxide nanoparticles are manufactured in a polyimide layer through a curing process of a polymer to form a metal oxide quantum dot 510.

Quantum dots are nanoscale, zero-dimensional ultrafine structures. In this nanoscale structure, quantum effects such as quantum confinement effects and quantum transport effects that have not been observed in classical physics appear.

The metal oxide quantum dots 510 may be formed of In ₂ O ₃ , CuO, Cu ₂ O ₃ , PbO, Bi ₁₂ SiO ₂₀ , ZnO ₂ , SnO ₂ , GaO, MgO, GeO, BaO, SrO, Bi ₁₂ GeO ₂₀ , Bi ₁₂ SiO ₂ , Cd ₂ SnO ₄ , CdSnO ₃ and Li ₃ CuO ₃ . However, the present invention is not limited thereto.

The diameter of the metal oxide quantum dot 510 may be 1 nm to 100 nm. If the diameter of the metal oxide quantum dots is less than 1 nm, formation of the quantum dots becomes substantially difficult, and adjustment of the particle size of the quantum dots becomes difficult. In addition, when the diameter of the metal oxide quantum dots exceeds 100 nm, it is difficult to expect the inherent effect of the exciton formation according to the quantum dots.

For example, the polyimide layer including the metal oxide quantum dots is formed by a chemical reaction method of a metal thin film and polyamic acid (PAA).

The metal oxide quantum dots 510 may be formed in a multilayer of two or more layers.

Prior to forming the n-type polycrystalline ZnO layer 600 to be described later, the polyimide layer 500 including the metal oxide quantum dots from the step of forming the metal thin film 300 on the p-type polycrystalline ZnO layer 200 ) May be repeated two or more times to form a metal oxide quantum dot 510 having a multilayer structure of two or more layers.

The metal oxide quantum dot 510 may have a tandem structure in which heterogeneous materials are stacked.

For example, a metal thin film is deposited to a thickness of 5 nm to 10 nm, followed by spin coating a polyimide layer to a thickness of 10 nm or less, soft baking, and forming a metal oxide quantum dot using a curing process of a polymer. When repeatedly performed, a multi-layer metal oxide quantum dot structure may be formed. In addition, when the above process is repeated using metal thin films of different materials, a tandem metal oxide quantum dot may be formed.

Referring to FIG. 1E, a polycrystalline n-type ZnO layer 600 is formed on the polyimide layer 500 including the metal oxide quantum dots.

The n-type polycrystalline ZnO layer 600 separates excitons formed by metal oxide quantum dots absorbing sunlight, so that carriers of electrons and holes can be easily transferred to the electrodes.

The n-type polycrystalline ZnO layer 600 may have a thickness of 50 nm to 300 nm. However, the present invention is not limited thereto.

The p-type polycrystalline ZnO layer or the n-type polycrystalline ZnO layer may include a nanorod structure. However, the present invention is not limited thereto.

For example, about 34 nm of an n-type polycrystalline ZnO layer is deposited on the BPDA-PDA polymer layer including the metal oxide quantum dots by physical vapor deposition.

Referring to FIG. 1F, an electrode 700 is formed on the n-type polycrystalline ZnO layer 600.

The electrode 700 may be an ITO electrode. However, the present invention is not limited thereto.

For example, indium tin oxide (ITO) is deposited on the n-type polycrystalline ZnO layer to a thickness of about 140 nm. The diameter of the gate electrode of the ITO is about 200 mu m.

In the case of the metal oxide nanoparticles, a quantum well structure having a uniform size is formed in the polyimide. The states of electrons and holes formed by light irradiation in regularly arranged quantum wells having the same width can be described by the wave function. Excitons formed in the quantum well structure having the same width formed in multiple layers are recombined and are not lost, and electrons having wave functions having the same phase are moved to the n-type ZnO layer by direct tunneling.

In addition, the hole separated in the exciton moves to the electrode through the p-type ZnO layer. At this time, the energy level with the highest probability of the phase-matched wave function in the quantum well structure formed inside the polyimide layer is determined by the time-dependent Schrodinger equation of quantum mechanics. Induction is possible.

In other words, considering the energy and state of electrons and holes emitted through tunneling, electrons and holes coinciding with exciton formation and their wave functions coincide with quantum wells formed in polyimide using WKB (Wentzel-Kramers-Brillouin) approximation. do.

Thus, direct tunneling forms a continuous energy level that is released without exciton recombination into the n-type ZnO layer and the p-type ZnO layer. This may be defined as an intermediate band, which may form an impurity level by adding impurities to a semiconductor thin film as well as a quantum dot to form an intermediate band.

In the present invention, the ultraviolet region (3.4eV) is absorbed by the polycrystalline ZnO layer, and in order to absorb the wavelength of 400nm to 700nm other than the visible region, the intermediate of the metal oxide quantum dot by changing the kind of material or adjusting the size of the quantum dot The position of the band can be adjusted arbitrarily.

Therefore, it is possible to fabricate tandem solar cells having different absorption bands of solar wavelengths.

Example  2

2 is a perspective view of an intermediate band organic solar cell using metal oxide quantum dots formed on a patterned p-type polycrystalline ZnO layer according to an embodiment of the present invention.

Referring to FIG. 2, the p-type polycrystalline ZnO layer 200 is patterned to maximize the efficiency of the solar cell. In the manufacturing process of FIGS. 1A to 1F, before the forming of the metal thin film 300 on the p-type polycrystalline ZnO layer 200, the step of patterning the p-type polycrystalline ZnO layer 200 is further performed. An intermediate band organic solar cell using a metal oxide quantum dot formed on the p-type polycrystalline ZnO layer 210 may be manufactured.

By patterning the upper portion of the p-type polycrystalline ZnO layer 200 to increase the cross-sectional area of the ZnO layer to meet the polyimide layer to increase the density of holes separated from the exciton formed in the quantum dot flows to the electrode through the p-type polycrystalline ZnO thin film Play a role of

The shape of the pattern may be a rectangle having a length of 100 μm or less or a circle having a diameter of 100 μm or less. If the length or diameter of one side is 100 µm or more, there is a fear that the effect of improving the photoelectric conversion efficiency of the solar cell is reduced.

The depth of the pattern may be arbitrarily adjusted in consideration of the thickness of the polyimide and the diameter and density of the quantum dots formed in a multilayer.

For example, a patterned polycrystalline ZnO layer grown like a nanorod on an ITO transparent electrode is formed by sputtering, a physical vapor deposition method. The patterned polycrystalline ZnO layer has the effect of increasing efficiency as well as the conventional polycrystalline Si substrate, and at the same time, the excitons formed from the metal oxide quantum dots are separated and move quickly to the electrode.

3 is a cross-sectional image of a polyimide layer including In ₂ O ₃ nanoparticles on a ZnO polycrystalline thin film.

Referring to FIG. 3, a ZnO polycrystalline thin film is deposited to a thickness of about 120 nm using a sputtering method on an ITO thin film.

In is deposited to a thickness of about 5 nm on the ZnO polycrystalline thin film by thermal deposition. Thereafter, a polyamic acid (PAA) having a thickness of about 50 nm is deposited on the In metal thin film by spin coating. In this experiment, PAA solution was made by mixing BPDA-PDA with N-methyl-2-pyrrolidone (3wt.%).

PAA and metals are dissolved in a vacuum dryer for about 24 hours at room temperature. In this process, PAA melts the In metal thin film and generates In metal ions.

Then, after heating for 30 minutes at 135 ℃, it is heated for 1 hour to 400 ℃ in a nitrogen atmosphere using a rapid heat treatment method.

During the heating process, metal oxide nanoparticles are formed in the polymer layer by chemical reaction of PAA exposed to metal ions and oxygen to form metal oxide quantum dots. The diameter of the In ₂ O ₃ nanoparticles is about 15nm.

As shown in FIG. 3, the nanoparticles act as quantum dots, and the formed nanoparticles may be loaded into the polyimide layer.

As described above, a polyimide layer is formed on the ZnO polycrystalline thin film, and a quantum dot is formed inside the polyimide layer. Therefore, by adjusting the size or the material of the quantum dot can absorb the light of various wavelengths included in the visible light, it can be seen that it increases the photoelectric conversion efficiency.

In the above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications and changes by those skilled in the art within the spirit and scope of the present invention. You can change it.

100: substrate 200: p-type polycrystalline ZnO layer
210: patterned p-type polycrystalline ZnO layer 300: metal thin film
400: polyimide layer
500: polyimide layer containing a metal oxide quantum dot
510: metal oxide quantum dot 600: n-type polycrystalline ZnO layer
700: electrode

Claims (14)

Board;
A p-type polycrystalline ZnO layer formed on the substrate;
A polyimide layer formed on the p-type polycrystalline ZnO layer;
An n-type polycrystalline ZnO layer formed on the polyimide layer; And
An electrode formed on the n-type polycrystalline ZnO layer,
The polyimide layer is an intermediate band organic material solar cell including a metal oxide quantum dot. The method of claim 1,
The substrate is a mid band organic solar cell of a single crystal Si substrate, a polycrystalline Si substrate, an ITO substrate, a sapphire substrate or a glass substrate. The method of claim 1,
The p-type polycrystalline ZnO layer or n-type polycrystalline ZnO layer is an intermediate band organic solar cell comprising a nano-rod structure. The method of claim 1,
The p-type polycrystalline ZnO layer has a thickness of 50nm to 300nm intermediate band-based organic solar cell. The method of claim 1,
The polyimide layer is an intermediate band system including BPDA-PDA, PMDA-PDA, ODPA-PDA, 6FDA-PDA, BTDA-ODA, DMAc, BDSDA-ODA, DSDA, BPDA-Bz, TMA-PPD or ODA-PI. Organic solar cell. The method of claim 1,
The metal oxide quantum dots include In ₂ O ₃ , CuO, Cu ₂ O ₃ , PbO, Bi ₁₂ SiO ₂₀ , ZnO ₂ , SnO ₂ , GaO, MgO, GeO, BaO, SrO, Bi ₁₂ GeO ₂₀ , Bi ₁₂ SiO ₂₀ , Intermediate band-based organic solar cell comprising at least one selected from Cd ₂ SnO ₄ , CdSnO ₃ and Li ₃ CuO ₃ . The method of claim 1,
The metal oxide quantum dot has a diameter of 1nm to 100nm intermediate band-based organic solar cell. The method of claim 1,
The metal oxide quantum dot is an intermediate band organic solar cell formed of two or more layers. 9. The method of claim 8,
The metal oxide quantum dot is an intermediate band organic solar cell having a tandem structure in which heterogeneous materials are stacked. The method of claim 1,
The electrode is an intermediate band organic solar cell of the ITO electrode. Preparing a substrate;
Forming a p-type polycrystalline ZnO layer on the substrate;
Forming a metal thin film on the p-type polycrystalline ZnO layer;
Forming a polyimide layer on the metal thin film;
Drying the polyimide layer formed on the metal thin film to melt the metal thin film and generate metal ions;
Heat treating the polyimide layer and forming metal oxide quantum dots in the polyimide layer through chemical reaction with the generated metal ions;
Forming an n-type polycrystalline ZnO layer on the polyimide layer including the metal oxide quantum dots; And
Method of manufacturing an intermediate band-based organic solar cell comprising the step of forming an electrode on the n-type polycrystalline ZnO layer. The method of claim 11,
Prior to forming the n-type polycrystalline ZnO layer,
And forming a polyimide layer including the metal oxide quantum dots two or more times from forming a metal thin film on the p-type polycrystalline ZnO layer. The method of claim 11,
The metal thin film is Zn, In or Cu method of manufacturing an intermediate band organic solar cell. Preparing a substrate;
Forming a p-type polycrystalline ZnO layer on the substrate;
Patterning an upper portion of the p-type polycrystalline ZnO layer to form a p-type polycrystalline ZnO layer patterned thereon;
Forming a metal thin film on the upper patterned p-type polycrystalline ZnO layer;
Forming a polyimide layer on the metal thin film;
Drying the polyimide layer formed on the metal thin film to melt the metal thin film and generate metal ions;
Heat treating the polyimide layer and forming metal oxide quantum dots in the polyimide layer through chemical reaction with the generated metal ions;
Forming an n-type polycrystalline ZnO thin film on the polyimide layer including the metal oxide quantum dots; And
Method of manufacturing an intermediate band-based organic solar cell comprising the step of forming an electrode on the n-type polycrystalline ZnO thin film.

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