JP2002076403A - Organic solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic solar battery whose efficiency is higher than the conventional ones. SOLUTION: In this organic solar battery, a transparent electrode 3, a Hall conduction layer 4 composed of triphenylene derivative, a charge generating layer 5 composed of phthalocyanine derivative, an electron conduction layer 6 composed of perylene derivative, an electron conduction layer 7 composed of hexaazatriphenylene derivative, and a metal electrode 8 are laminated in order on a glass substrate 2, and an element is constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell used as a power source for a household power supply, a wristwatch or a small electronic computer, and more particularly to a solar cell for preventing conversion of electric charges and improving conversion efficiency, and furthermore, an organic light-emitting device using ultraviolet light. The present invention relates to an organic solar cell with improved photodegradation of a compound.

[0002]

2. Description of the Related Art As one of solutions to energy problems and environmental problems such as depletion of petroleum resources and global warming,
Solar cells are of interest.

However, silicon (Si) -based solar cells, which are currently the mainstay solar cells, have high manufacturing costs and consume large amounts of power during manufacturing.
Therefore, there is still a challenge to be a trump card that can truly solve energy and environmental problems.

Therefore, a technique using an organic compound which can be produced at low cost instead of Si has been proposed, and in recent years, much research and development has been carried out.

One of the solar cells using organic compounds is p-type.
Some use a Schottky barrier between a conductive organic compound and a metal having a small work function.

However, Schottky type organic solar cells have low energy conversion efficiency under white light, and have not yet reached a practical level.

On the other hand, a technique utilizing a pn junction between a p-type conductive organic compound and an n-type conductive organic compound has been proposed. As such a pn junction type organic solar cell, a cell using copper phthalocyanine which is a p-type conductive organic compound and a perylene derivative which is an n-type conductive compound is known, and simulated sunlight (75 mW / cm) is used. ² ) The lower energy conversion efficiency is 0.95%, which is higher than that of a Schottky type organic solar cell.

However, the energy conversion efficiency of a pn junction type organic solar cell is considerably lower than that of a polycrystalline type solar cell with an energy conversion efficiency of 15% or more and that of an amorphous type solar cell with an energy conversion efficiency of 10% or more. I can say.

Also, although different from a pure pn junction, a nanoporous sintering made of TiO _{2 having} a particle size of about 10 nm is used for performing charge separation using electronic excitation of a dye upon absorbing sunlight. 2. Description of the Related Art A wet solar cell has been proposed in which a body is formed, a dye is supported on the surface thereof, and an electrolyte solution in which an I ^-- I ^3- redox couple is dissolved is injected.

In such a wet type solar cell, the amount of the dye carried is increased by utilizing the large surface area of the nanoporous TiO ₂ sintered body, and the electron donor I ⁻ is converted into the dye by permeating the electrolyte. Good energy contact, energy conversion efficiency under simulated sunlight is 10%
Thus, a performance close to that of amorphous silicon is obtained, but on the other hand, there is a problem in long-term reliability because an electrolytic solution having high volatility is used.

Therefore, an organic solar cell in which nanoporous TiO ₂ and a dye supported on the surface thereof are used as they are and an electrolyte is replaced with a solid p-type conductive compound has been studied. For example, an organic solar cell using polypyrrole as a p-type conductive compound (K. Murakoshi,
R. Kogure, Y .; Wada, and S.W. Yan
agida, Chemistry Letters
1997, p. 471). In such an organic solar cell, since a volatile electrolyte is not used, long-term reliability can be improved.

[0012]

However, in an organic solar cell composed of nanoporous TiO ₂ / dye / p-type conductive polypyrrole as described above, the p-type is smaller than the electrolyte in which a redox _couple is dissolved. Since the conductive polypyrrole did not penetrate into the nanoporous TiO ₂ , the energy conversion efficiency was reduced to 0.1%.

The present invention has been devised in view of the above, and has as its object to provide an organic solar cell having improved energy conversion efficiency without using a nanoporous member in which it is difficult to join a solid-solid interface. The idea is to get a battery.

[0014]

According to the present invention, there is provided an organic solar cell comprising a transparent electrode, a hole conductive layer composed of a triphenylene derivative, a charge generation layer composed of a phthalocyanine derivative, and an electron conductive layer composed of a perylene derivative on a transparent substrate. When,
Another electron conductive layer made of a hexaazatriphenylene derivative and a metal electrode are sequentially laminated.

The triphenylene derivative is preferably a compound represented by the following general formula (1).

[0016]

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The phthalocyanine derivative is preferably a compound represented by the general formula [Chemical Formula 2].

[0018]

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Further, the perylene derivative is preferably a compound represented by the general formula [Formula 3].

[0020]

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Further, the hexaazatriphenylene derivative is preferably a compound represented by the general formula [4].

[0022]

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Moreover, in the organic solar cell of the present invention, it is preferable to form a TiO ₂ film on the other surface of the transparent substrate.

[0024]

According to the organic solar cell of the present invention, a transparent electrode, a hole conduction layer composed of a triphenylene derivative, a charge generation layer composed of a phthalocyanine derivative, an electron conduction layer composed of a perylene derivative, and a hexaaza By using an element in which another electron conductive layer made of a triphenylene derivative and a metal electrode are sequentially laminated, the triphenylene derivative does not diffuse excitene and has conductivity only for holes. Excitane generated in the phthalocyanine derivative, which is the charge generation layer like a solar cell, does not reach the transparent electrode and recombine, and the hexaazatriphenylene derivative does not diffuse the excitene and conducts only electrons. Because of its excitability, the excimer produced in perylene, like a conventional pn junction type organic solar cell, It is no longer down recombine reaches the metal electrode.

Furthermore, the triphenylene derivative, the phthalocyanine derivative, the perylene derivative, and the hexaazatriphenylene derivative all have a conjugated molecular structure with high similarity, so that the molecules can be well overlapped.

Further, since these derivatives are formed into a thin film in a planar shape by a vacuum deposition method, they have an interface structure with good contact, and therefore, a nanoporous TiO 2 carrying a dye.
_{(2) As in} an organic solar cell using a sintered body and polypyrrole, the interface for charge separation is not interrupted.

The organic solar cell of the present invention having the above-mentioned constitutions effectively separates electric charges from exciten generated by the absorption of sunlight by the phthalocyanine derivative, thereby improving the conversion efficiency. Enhance. For example,
An organic solar cell used for a household power supply, a power supply for a wristwatch, a small computer, or the like can be more efficient than a conventional product.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing an example of the organic solar cell of the present invention. In the figure, reference numeral 2 denotes a glass substrate as the transparent substrate, one surface of the glass substrate 2 is coated with a surface coat layer 1, and the other surface is a transparent electrode 3, a hole conductive layer 4,
The charge generation layer 5, the electron conduction layer 6, the other electron conduction layer 7, and the metal electrode 8 are sequentially laminated.

The surface coat layer 1 is arranged to absorb ultraviolet rays contained in sunlight and prevent the organic compounds constituting the device from absorbing the ultraviolet rays to cause light degradation.

Such a surface coat layer 1 is made of, for example, T
It is made of iO ₂ and is formed on the glass substrate 2 by a CVD method, a sputtering method, or the like. On the surface coat layer 1,
Further, an antireflection film may be formed.

The glass substrate 2 is disposed to shield the element from the outside air and to transmit visible light and infrared light to reach the charge generation layer 5. The material and manufacturing method are not particularly limited as long as they have high transmittance to visible light and infrared light. A transparent resin substrate may be used instead of glass.

The transparent electrode 3 is arranged to extract holes from the hole conductive layer 4 and to transmit visible light and infrared light to reach the charge generation layer 5. The transparent electrode 3 is made of indium tin oxide (ITO), antimony tin oxide (NESA), indium oxide, or the like, and is formed on the glass substrate 2 by a CVD method, a sputtering method, or the like.

The hole conduction layer 4 conducts only holes of the charges generated from the charge generation layer 5 to reach the transparent electrode 3 and further transmits visible light and infrared light to reach the charge generation layer 5. Placed to let.

Although the phthalocyanine derivative of the charge generation layer 5 described later also has hole conductivity, in the charge generation layer 5,
Excitons composed of electron-hole pairs are generated and diffuse in the layer. If the charge generation layer 5 and the transparent electrode 3 are in direct contact with each other, recombination occurs at the interface and energy conversion efficiency is reduced. Cause. Therefore, by providing the hole conductive layer 4 that blocks the diffusion of excitons and conducts only holes between the charge generation layer 5 and the transparent electrode 3, recombination at the interface with the transparent electrode 3 is prevented. Energy conversion efficiency can be improved.

The hole conductive layer 4 is made of a triphenylene derivative represented by the following general formula (Formula 1), and is formed on the transparent electrode 3 by a vapor deposition method.

[0036]

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The charge generating layer 5 absorbs visible light and infrared light to generate excitons composed of electrons and holes, and the excitons diffuse to form holes in the hole conductive layer 4 and electrons in the electron conductive layer 6. Is arranged to perform charge separation.

The charge generation layer 5 has the general formula (Formula 2)
Is formed on the hole conduction layer 4 by a vapor deposition method.

[0039]

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The electron conduction layer 6 is provided to preferentially conduct electrons of the charges generated from the charge generation layer 5 and to reach the electron conduction layer 7.

The electron conductive layer 6 has the general formula (7)
Is formed on the charge generation layer 5 by a vapor deposition method.

[0042]

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The electron conducting layer 7 is arranged to conduct only electrons out of the electric charges generated from the electron conducting layer 6 to reach the metal electrode 7.

The electron conductive layer 7 has the general formula (Chem. 4)
A hexaazatriphenylene derivative represented by the following formula is used, and is formed on the electron conductive layer 6 by a vapor deposition method.

[0045]

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As described above, the compounds used in each of the hole conductive layer 4, the charge generation layer 5, and the electron conductive layers 6 and 7 have similar molecular structures and molecular sizes, and therefore have good molecular packing. And as a result, π
It is considered that the overlap of the electron orbits is improved, which has a favorable effect on the charge conduction.

The metal electrode 8 is arranged to extract electrons from the electron conducting layer 7. The metal electrode 8 is made of Ag or the like, and is formed on the electron conductive layer 7 by an evaporation method.

The hole conduction layer 4, charge generation layer 5, electron conduction layers 6, 7, and metal electrode 8 are all 1 × 10 ^-6 T
It is preferable to perform vapor deposition continuously in a vacuum of orr or less, whereby an oxidation reaction of an organic compound or a metal can be suppressed by oxygen or moisture in the air, and as a result, characteristics of the element can be improved.

Thus, according to the organic solar cell of the present invention,
On a glass substrate 2, a transparent electrode 3, a hole conductive layer 4 made of a triphenylene derivative, a charge generation layer 5 made of a phthalocyanine derivative, an electron conductive layer 6 made of a perylene derivative, and an electron conductive layer made of a hexaazatriphenylene derivative 7 and a metal electrode 8 are sequentially stacked, so that the triphenylene derivative does not diffuse excitene and has conductivity only for holes, thereby providing a similar effect to a conventional pn junction type organic solar cell. Excitane generated in the phthalocyanine derivative, which is a charge generation layer, does not reach the transparent electrode and recombine, and the hexaazatriphenylene derivative does not diffuse excitene and has conductivity only for electrons. Excitons generated in perylene reach metal electrodes, as in conventional pn junction type organic solar cells. Prevents the recombination Te, further triphenylene derivative, a phthalocyanine derivative, also perylene derivatives, hexaazatriphenylene derivative either by having a high conjugated molecular structure similarity, better overlap between molecules.

In addition, since these derivatives are formed into a thin film in a planar shape by a vacuum evaporation method, they have an interface structure with good contact, and therefore, a nanoporous TiO 2 carrying a dye.
₍₂ ) Unlike an organic solar cell using a sintered body and polypyrrole, the interface for charge separation is not interrupted,
With such a configuration, charge separation from exciten generated by the phthalocyanine derivative absorbing sunlight is effectively performed, and the conversion efficiency is significantly increased.

[0051]

Next, specific examples of the organic solar cell of the present invention will be described.

Example 1 First, a TiO ₂ film (150 nm thick) as the surface coat layer 1 was formed on the back surface of the glass substrate 2, and an ITO film (thickness 1) as the transparent electrode 3 was formed on the other surface.
A film having a thickness of 50 nm and a resistance of 7 Ω / cm ² ) was coated with the hole conductive layer 4 by vapor deposition.

That is, keeping the substrate temperature at 150 ° C.
× 10^-71 nm / s deposition rate in Torr vacuum
The triphenylene derivative (R =
CH _Three) Was deposited to a thickness of 15 nm.

Next, a phthalocyanine derivative represented by Chemical Formula 2 is deposited to a thickness of 50 nm at a film forming rate of 1 nm / s in a vacuum of 8 × 10 ^-7 Torr to form a charge generating layer 5. Formed.

Then, a perylene derivative represented by Chemical Formula 3 is vapor-deposited in a vacuum of 8 × 10 ^-7 Torr at a film formation rate of 1 nm / s to a thickness of 15 nm to form an electron conductive layer 6.
Was formed.

Subsequently, a hexaazatriphenylene derivative (X = CON (C) represented by Chemical Formula 4 (Formula 8) at a deposition rate of 1 nm / s in a vacuum of 8 × 10 ^-7 Torr.
H ₃ ) ₂ ) was deposited to a thickness of 15 nm to form an electron conductive layer 7.

Finally, in a vacuum of 8 × 10 ⁻⁷ Torr, Ag was deposited to a thickness of 150 nm at a film formation rate of 0.1 nm / s to provide a metal electrode 8. Thus, an organic solar cell A having an effective area of 0.1 cm ² was obtained.

Each of the organic compounds was 99.9%
The reagent having the above purity was purified by vacuum evaporation immediately before use.

Each of the above film thicknesses was monitored by a crystal oscillation type film forming controller. [Comparative Example 1] In this example, in manufacturing the organic solar cell A, the hole conductive layer made of a triphenylene derivative and the electron conductive layer made of a hexaazatriphenylene derivative were not formed, and the other configurations were the same. Thus, an organic solar cell B was obtained. [Comparative Example 2] In this example, the organic solar cell A was manufactured in the same manner as in Example 1 except that the TiO ₂ film serving as the surface coat layer 1 was not formed. Battery C was obtained.

The characteristics of these organic solar cells were evaluated as follows. Irradiate white light (intensity 100 mW / cm ² ) from a halogen tungsten lamp,
Each characteristic was determined from a current-potential curve obtained by measuring a current value with an electrometer while applying a potential with a function generator. That is, according to the current-potential curve, the open photovoltage (V _OC ), the short-circuit photocurrent density (J _SC ),
When the fill factor (FF) and the photoelectric conversion efficiency (η) with respect to the incident light were determined, the results shown in Table 1 were obtained. Samples A, B, and C in the table are organic solar cells A, B, and C, respectively.

[0061]

[Table 1]

As is clear from this table, it is understood that the organic solar cell A of the present invention is the most excellent in both the energy conversion efficiency and the durability during continuous operation for 24 hours.

However, the energy conversion efficiency of the organic solar cell B is as low as about half that of the organic solar cell A,
In the organic solar cell C, the initial energy conversion efficiency is not inferior to that of the organic solar cell A, but the durability during continuous operation for 24 hours is significantly inferior. This is because the organic solar cell B did not form a hole conductive layer composed of a triphenylene derivative, and thus excite generated in the phthalocyanine derivative diffused to the interface with the transparent electrode and caused recombination. Think.

In the case of the organic solar cell C, since the TiO ₂ film for absorbing ultraviolet light is not formed on the back surface of the glass substrate, it is presumed that the cause is that the organic compound is photo-degraded by the ultraviolet light.

[0065]

As described above, according to the organic solar cell of the present invention, a transparent electrode, a hole conductive layer made of a triphenylene derivative, a charge generation layer made of a phthalocyanine derivative, and a perylene derivative are formed on a transparent substrate. Since the electron conductive layer, the other electron conductive layer made of a hexaazatriphenylene derivative, and an element in which a metal electrode is sequentially laminated, the triphenylene derivative does not diffuse excitene and has conductivity only for holes. , Conventional pn
Excites generated in the phthalocyanine derivative, which is the charge generation layer, as in the junction type organic solar cell, do not reach the transparent electrode and recombine, and the hexaazatriphenylene derivative does not diffuse the excitene, only electrons. Since it has conductivity, unlike conventional pn junction type organic solar cells, the excite generated in perylene does not reach the metal electrode and recombine, and further, a triphenylene derivative, a phthalocyanine derivative, a perylene derivative, Since all hexaazatriphenylene derivatives have a conjugated molecular structure with high similarity, the molecules are well overlapped with each other, and since these are formed into a thin film in a planar shape by a vacuum deposition method, an interface structure with good contact can be obtained. use has, therefore, a nanoporous TiO ₂ sintered body and polypyrrole carrying a dye As in the case of an organic solar cell, the interface for charge separation is not interrupted, and as a result, charge separation from excite generated by absorption of sunlight by the phthalocyanine derivative is effectively performed, for example, In addition, the organic solar cell used for a household power supply, a power supply for a wristwatch, a small computer, or the like can be made more efficient than a conventional product.

In the present invention, by providing a layer for absorbing ultraviolet light on the back surface of the transparent substrate, it was possible to prevent the organic compound from being decomposed by ultraviolet light.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an organic solar cell of the present invention.

[Explanation of symbols]

1: surface coating layer, 2: glass substrate, 3: transparent electrode,
4: hole conduction layer, 5: charge generation layer, 6, 7: electron conduction layer, 8: metal electrode

Claims (1)

[Claims] 1. A transparent electrode on a transparent substrate, a hole conductive layer composed of a triphenylene derivative, a charge generation layer composed of a phthalocyanine derivative, an electron conductive layer composed of a perylene derivative, and another electron conductive layer composed of a hexaazatriphenylene derivative. An organic solar cell, characterized in that a layer and a metal electrode are sequentially laminated.