JPH04337674A - Organic solar cell - Google Patents

Abstract

PURPOSE:To enable an energy conversion efficiency to be improved and obtain a high voltage by allowing a unit cell to be a compound layer where a first layer consisting of perylene coloring matter film and a second layer consisting of phthalocyanine coloring matter film are laminated in sequence from the transparent electrode side toward the opposing electrode side. CONSTITUTION:A unit cell is a compound layer where a first layer consisting of perylen coloring matter and a second layer consisting of phthalocyanine coloring matter are laminated in sequence from the transparent electrode side toward the opposing electrode side. The #1 coloring matter includes perylene tetracarbon acid bisbenzoimidazole N, N' and dimethyl perylene tetracarbon acid diimide. The phthalocaylanine coloring matter includes a non-metal phthalocyanine and metal phthalocyanine. These first and second layers are formed by the vacuum deposition method for subliming each coloring matter with resistance heating within a vacuum container. These compound layers enable an energy conversion efficiency of the unit cell to be improved.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to organic solar cells.

0002

[Prior Art] Organic solar cells that use organic compounds as solar cell materials are superior to solar cells that use inorganic semiconductors in terms of cost, large area, and ease of manufacturing process. Organic solar cells of various configurations using organic compounds as solar cell materials have been proposed.

For example, an organic solar cell using a laminated film of copper phthalocyanine and perylene dye has been proposed.
It is reported that the energy conversion efficiency of this organic solar cell is about 1% (C.W. Tang, Applie
d Physics Letters, Vol. 48,
p. 183). However, in the solar cell described above, in order to obtain high energy conversion efficiency, the thickness of the dye layer, which is a semiconductor layer, must be made thin. As a result, pinholes are likely to form in the film, resulting in short circuits between the electrodes.

[0004] In addition, a Schottky type solar cell using a quinacridone dye is known from CHEMISTRY.
LETTERS (1984) P. 1305, Proceedings of the Society of Polymer Science, Vol. 34 (1985), p. 2001, JP-A-6
It is described in Japanese Patent No. 1-59784. In these solar cells, a method is used to form a Schottky junction by laminating metals with low work functions such as indium and aluminum on the dye layer, and these metal films are formed by methods such as vapor deposition and sputtering. However, it has the drawback that oxygen in the air tends to form an oxide film on the bonding interface, deteriorating the bond and reducing performance. Furthermore, since light must be incident from the side of a metal electrode such as indium or aluminum, there is a drawback that the low light transmittance of the metal leads to a decrease in energy conversion efficiency.

[0005]

OBJECTS OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and its purpose is to provide a high energy conversion efficiency and less short-circuiting of electrodes.
Our goal is to provide organic solar cells with stable performance.

[0006]

[Means for Solving the Problems] The transparent electrode used in the present invention is formed using a known electrode material that can transmit visible light, and is usually formed by vacuum evaporation, sputtering, or ion plating on the surface of a transparent substrate. established by etc.

The above-mentioned electrode material is not particularly limited as long as it has low absorption of visible light, and examples thereof include tin-doped indium oxide (hereinafter referred to as ITO), tin oxide, indium oxide, etc. Among them, ITO is particularly preferred.

Examples of the transparent substrate include glass and polymers such as acrylic, vinyl, polyolefin, polyester, polyamide, and polycarbonate.

The counter electrode used in the present invention is formed using a known electrode material by vacuum evaporation, sputtering, ion plating, or the like. Examples of the electrode material include metals with a large work function such as gold, silver, and platinum.

The organic solar cell of the present invention has one unit cell between the transparent electrode and the counter electrode, and a conductive film is provided between the unit cell and the transparent electrode. The conductive film is an organic polymer/metal composite made of a mixture of a conjugated polymer formed by plasma polymerization and a metal formed by sputtering, and the plasma polymerization and sputtering are performed simultaneously in the same container. be exposed.

[0011] The above conjugated polymer is a conjugated organic monomer.
The conjugated organic monomer is not particularly limited as long as it has a conjugated double bond, such as naphthalene, pyrene, perylene, and derivatives thereof ( For example, fused aromatic compounds such as naphthalenetetracarboxylic dianhydride, naphthalenetetracarboxylic diimide and derivatives thereof, perylenetetracarboxylic dianhydride, perylenetetracarboxylic diimide and derivatives thereof,
and phenyl compounds represented by the following general formula.

0012

[Chemical formula 1]

(In the formula, R1 and R2 represent hydrogen, halogen, hydroxyl group, alkyl group, alkoxy group, sulfone group, nitrile group, vinyl group, etc., and n is an integer of 1 or more.) Examples of the above phenyl compound include: biphenyl, 4,4
Biphenyl compounds such as '-biphenyldiol, terphenyl compounds such as p-terphenyl, p-quarter-phenyl, 4-hydroxy-p-quarter-phenyl, 4
, 4'-dihydroxy-p-quarter-phenyl, and derivatives thereof.

The plasma polymerization of the conjugated organic monomer is carried out in a container whose pressure is adjusted to a constant level with a carrier gas by supplying electric power between electrodes. For example, when the monomer is a liquid, the monomer can be supplied by vaporizing the monomer outside the container and then introducing the vapor into the container. In this case, the monomer may be evaporated or sublimated by resistance heating in a container. The temperature at which the monomer is evaporated or sublimated by resistance heating is determined as appropriate depending on the type of monomer, and is, for example, 50 to 400 m
°C is preferred.

[0015] As the carrier gas, for example, N2
, Ar, and the like are preferably used, and the pressure at that time is preferably 10-1 to 10-4 Torr, more preferably 10-2 to 10-3 Torr.

[0016] The type of power to be supplied is not particularly limited, and for example, the frequency is 10kHz to
35 kHz or 10 MHz to 50 MHz, direct current, etc. can be suitably used, and the output thereof is preferably 50 W to 1 kW, more preferably 50 to 300 W.

The metal to be sputtered is not particularly limited, and includes, for example, gold, silver, copper, iron,
Single metals such as tin, chromium, nickel, cobalt, and titanium, and their alloys (stainless steel, nickel alloy cast iron,
bronze, etc.).

[0018] The above metal sputtering is carried out by using a metal as an anode electrode material and supplying electric power between the electrodes to ionize and accelerate the carrier gas in a container adjusted to a constant pressure with a carrier gas. This is done by sputtering the metal electrode.

Since the sputtering described above is carried out simultaneously with the plasma polymerization of the organic monomer in the same container, the conditions are the same as those for the plasma polymerization described above. The thickness of the conductive film formed by the above method is not particularly limited, but as it becomes thinner, pinholes are more likely to occur, and as it becomes thicker, the light transmittance decreases and the electrical resistance of the film increases. Since the energy conversion efficiency decreases in
0 to 1000 Å is preferable.

The above unit cell is a composite layer in which a first layer made of a perylene dye and a second layer made of a phthalocyanine dye are sequentially laminated from the transparent electrode side to the counter electrode side.

Examples of perylene dyes used in the first layer include perylenetetracarboxylic acid bisbenzimidazole, N,N'-dimethylperylenetetracarboxylic acid diimide, and N,N'-diphenylperylenetetracarboxylic acid. Examples include acid diimide, and these may be used alone or in combination of two or more.

[0022] As a method for forming the first layer, for example,
An example is a vacuum evaporation method in which a perylene dye is sublimated by resistance heating in a vacuum container. The thickness of the first layer is not particularly limited, but the thinner the pinhole
The thickness is preferably from 100 to 1000 Å, since the thickness tends to cause pores and the energy conversion efficiency decreases due to a decrease in light transmittance and an increase in the electrical resistance of the film.

Examples of the phthalocyanine dye used in the second layer include metal-free phthalocyanine, metal phthalocyanine, and derivatives thereof. As the metal phthalocyanine, for example, the central atom is
Examples include metal phthalocyanine compounds formed from metals such as copper, magnesium, zinc, aluminum, tin, chromium, manganese, iron, cobalt, rhodium, palladium, platinum, and halides of metals with a valence of 3 or more. It will be done.

Examples of the above derivatives include derivatives in which the hydrogen atom in the phthalocyanine molecule is substituted with a sulfone group, nitro group, cyano group, carboxyl group, halogen atom, etc.

[0025] As a method for forming the second layer, for example, the vacuum evaporation method can be cited as in the case of the first layer. The thickness of the second layer is not particularly limited, but as it becomes thinner, pinholes are more likely to occur, and as it becomes thicker, the energy conversion efficiency decreases due to a decrease in light transmittance and an increase in the electrical resistance of the film. 200 to 1000 Å is preferable.

Next, the organic solar cell of the second invention will be explained. In the organic solar cell of the second aspect of the present invention, the conductive film is arranged between the transparent electrode formed on the electrode and the counter electrode, from the transparent electrode side to the counter electrode side, a first layer made of a perylene dye, a phthalocyanine A unit cell is provided as a composite layer in which a second layer made of a quinacridone dye and a third layer made of a quinacridone dye are sequentially laminated.

As the perylene dye used in the first layer of the unit cell, the above perylene dye can be used. The film thickness of the first layer of the unit cell on the counter electrode side is not particularly limited, but if it becomes thin, pinholes are likely to occur, and if it becomes thick, the light transmittance will decrease and the electrical resistance of the film will increase. Therefore, the energy conversion efficiency decreases,
100-1000 Å is preferable.

The phthalocyanine dyes mentioned above can be used as the phthalocyanine dyes used in the second layer of the unit cell. The above-mentioned second layer can generate sufficient electromotive force even if it is a very thin film, and the same effect can be achieved even if the film has pinholes or is discontinuous. demonstrate. The film thickness is not particularly limited, but if it becomes thin, sufficient electromotive force cannot be generated, and if it becomes thick, the energy conversion efficiency decreases due to a decrease in light transmittance and an increase in the electrical resistance of the membrane. So,
20-300 Å is preferable.

Examples of the quinacridone dye used in the third layer of the unit cell include unsubstituted quinacridone,
2,9-dimethylquinacridone, 2,9-dichloroquinacridone, 3,10-dimethylquinacridone, 3,10
-dichloroquinacridone, 4,11-dimethylquinacridone, etc., and these may be used alone or in combination of two or more.

[0030] As a method for forming the third layer, for example,
As with the first layer, a vacuum evaporation method can be used. 3rd above
The thickness of the layer is not particularly limited, but as it becomes thinner, pinholes are more likely to occur, and as it becomes thicker, the energy conversion efficiency decreases due to a decrease in light transmittance and an increase in the electrical resistance of the film. , 300 to 1000 Å is preferable.

[0031]

[Examples] The present invention will be explained below with reference to Examples.

Example 1 A glass substrate on which ITO was vapor-deposited was placed on the lower electrode (cathode) in a reaction vessel in which a parallel plate electrode (anode) made of stainless steel plate (SUS-304) was installed, and a glass substrate was placed separately in the reaction vessel. 4,4'-dihydroxy-p-quarter phenyl was supplied to the tungsten board, and the inside of the container was
After reducing the pressure to 0-5 Torr, Ar gas was supplied so that the total pressure inside the container was 1 x 10-2 Torr.

Next, a current was passed through the tungsten board to heat the 4,4'-dihydroxy-p-quarter phenyl to 300°C, and a low frequency of 13kHz was applied between the electrodes at an output of 100W. , 500 Å on the ITO film
A conductive film with a thickness of .

Elemental analysis of the formed conductive film was performed by X-ray photoelectron spectroscopy, and the ratio of the number of atoms of the main element was found to be C.
:48%, O:35%, Fe:8%, and Cr:3%. The glass substrate on which the conductive film was formed was placed in a vacuum container of a vacuum evaporation device, the pressure was reduced to 1 x 10-5 Torr, N,N'-dimethylperylenetetracarboxylic acid diimide was resistance heated, and the conductive film was deposited on the conductive film. The film was deposited to a thickness of 600 Å.

Next, on this film, metal-free phthalocyanine was vacuum-deposited to a thickness of 600 Å in the same manner as N,N'-dimethylperylenetetracarboxylic acid diimide to form a unit cell.

[0036] On the unit cell, 1×10-5 Torr is applied.
Gold was vacuum deposited under reduced pressure of
An organic solar cell was obtained by forming a counter electrode with a thickness of 0 Å. Air mass (AM2) light (70 mW/cm2) was irradiated from the ITO transparent electrode side of the obtained organic solar cell, and the current-voltage characteristics were measured to determine the photoelectric conversion characteristics [open circuit voltage (VOC)]
, short circuit current density (JSC), fill factor (ff)
and energy conversion efficiency (η)], and the results are shown in Table 1.
It was shown to.

Example 2 In Example 1, 3,4,9,
An organic solar cell was obtained in the same manner as in Example 1 except that 10-perylenetetracarboxylic anhydride was used.

Example 1 Using the obtained organic solar cell
The photoelectric conversion characteristics were evaluated in the same manner as above, and the results are shown in Table 1.

Example 3 In the same manner as in Example 1, a conductive film was formed on a glass substrate on which ITO was deposited. The glass substrate on which the conductive film was formed was placed in a vacuum container of a vacuum evaporation device, and
Under reduced pressure to
It was deposited to a thickness of 0 Å.

Next, on this film, metal-free phthalocyanine and 2,9-dimethylquinacridone were sequentially vacuum-deposited to thicknesses of 200 Å and 400 Å in the same manner as N,N'-dimethylperylenetetracarboxylic acid diimide. and formed a unit cell.

[0041] On the unit cell, 1×10-5 Torr
Gold was vacuum deposited under reduced pressure of
An organic solar cell was obtained by forming a counter electrode with a thickness of 0 Å. Using the obtained organic solar cell, the photoelectric conversion characteristics were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 In Example 3, 3,4,9,
An organic solar cell was obtained in the same manner as in Example 1 except that 10-perylenetetracarboxylic anhydride was used.

Example 1 Using the obtained organic solar cell
The photoelectric conversion characteristics were evaluated in the same manner as above, and the results are shown in Table 1.

Comparative Example 1 An organic solar cell was obtained in the same manner as in Example 1 except that the conductive film was removed. When the photoelectric conversion characteristics of the obtained organic solar cell were evaluated in the same manner as in Example 1, the electrodes were short-circuited and no photoelectric conversion ability was exhibited.

Comparative Example 2 Same as Example 1 except that the conductive film was removed and the film thicknesses of N,N'-dimethylperylenetetracarboxylic acid diimide and metal-free phthalocyanine were changed to 900 Å and 900 Å, respectively. Then, an organic solar cell was obtained.

Example 1 Using the obtained organic solar cell
The photoelectric conversion characteristics were evaluated in the same manner as above, and the results are shown in Table 1.

Comparative Example 3 In Example 3, except that the conductive film was removed and the film thickness of 2,9-dimethylquinacridoneridone was changed to 600 Å,
An organic solar cell was obtained in the same manner as in Example 1.

Example 1 Using the obtained organic solar cell
When the photoelectric conversion characteristics were evaluated in the same manner as above, the electrodes were short-circuited and no photoelectric conversion ability was exhibited.

Comparative Example 4 Same as Example 1 except that in Example 3, the conductive film was removed and the film thicknesses of N,N'-dimethylperylenetetracarboxylic acid diimide and metal-free phthalocyanine were set to 900 Å and 900 Å, respectively. Then, an organic solar cell was obtained.

Example 1 Using the obtained organic solar cell
The photoelectric conversion characteristics were evaluated in the same manner as above, and the results are shown in Table 1.

[0051]

[Table 1]

[0052]

Effects of the Invention In the organic solar cell of the present invention, one unit cell is provided between a transparent electrode on which a conductive film is formed and a counter electrode, and the unit cell is located on the side of the transparent electrode. Since it is a composite layer in which a first layer consisting of a perylene dye film and a second layer consisting of a phthalocyanine dye film are sequentially laminated from the top to the counter electrode side, it has excellent energy conversion efficiency and high energy conversion efficiency. voltage can be obtained. In addition, pinholes are less likely to occur, resulting in an organic solar cell with stable performance and no short circuit between electrodes.

In the organic solar cell of the second aspect of the invention, one unit cell is provided between the transparent electrode on which the conductive film is formed and the counter electrode, and the unit cell is separated from the transparent electrode side. It is a composite layer in which a first layer made of a perylene dye film, a very thin second layer made of a thin phthalocyanine dye film, and a third layer made of a quinacridone dye film are sequentially laminated toward the counter electrode side. Therefore, the energy conversion efficiency is excellent and high voltage can be obtained. In addition, pinholes are less likely to occur, resulting in an organic solar cell with stable performance and no short circuit between electrodes.

Claims (2)

[Claims] 1. An organic solar cell comprising one unit cell between a transparent electrode and a counter electrode, and a conductive film provided between the unit cell and the transparent electrode, wherein the conductive film is , is a film made of an organic polymer/metal composite formed by simultaneously performing plasma polymerization of a conjugated organic monomer and sputtering of a metal. An organic solar cell characterized in that it is a composite layer in which a first layer made of a phthalocyanine-based dye and a second layer made of a phthalocyanine-based dye are sequentially laminated. 2. An organic solar cell comprising one unit cell between a transparent electrode and a counter electrode, and a conductive film provided between the unit cell and the transparent electrode, wherein the conductive film is , is a film made of an organic polymer/metal composite formed by simultaneously performing plasma polymerization of a conjugated organic monomer and sputtering of a metal. An organic solar cell characterized in that it is a composite layer in which a first layer made of a phthalocyanine dye, a second layer made of a phthalocyanine dye, and a third layer made of a quinacridone dye are sequentially laminated.