JPH09246580A - Photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photoelectric conversion element whose area can be made large and whose photoelectric conversion efficiency is enhanced more than that of an inorganic semiconductor/π conjugated system polymer solar cell by a method wherein a photoelectropolymerization π conjugate polymer layer is formed on a semiconductor layer containing a fullerene. SOLUTION: A π conjugate polymer layer 12 is formed on a fullerene thin- film layer 11. A fullerene is a substance in which carbon atoms are combined in a higher order manner, and fullerene C70 fullerene C76 , fullerene C82 , fullerene C84 , fullerene C90 and the like are enumerated in addition to fullerene C60 in which 60 carbon atoms are combined. The fullerene is formed as an amorphous fullerene thin film by a vapor deposition method or the like. A π conjugate polymer which forms the π conjugate polymer layer is the homopolymer of an unsaturated monomer such as, e.g. acetylene, pyrrole, thiophene, furan or the lilqe. When the π conjugate olymer layer is formed on a layer containing the fullerene, a photoelectropolymerization method is used. That is to say, the unsaturated mmonomer is electropolymerized on the layer containing the fullerene while light is irradiated, and the conjugate polymer layer which is composed of the homopolymer is formed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a photoelectric conversion element.

[0002]

2. Description of the Related Art A solar cell, which is an example of a photoelectric conversion element,
n-Si, amorphous Si (a-Si) or GaA
It is classified into a Schottky junction type composed of a semiconductor represented by s and a metal, and a pn junction type composed of a semiconductor and a semiconductor.

Generally, Schottky junction type solar cells are
A junction is formed by vapor-depositing a metal on a semiconductor layer such as n-Si, and a p-n junction solar cell sequentially forms p-type and n-type semiconductor layers by implanting ions into an intrinsic semiconductor.
Forming a bond. A solar cell using a-Si has a p-type semiconductor layer, an insulator layer, and an n-type semiconductor layer formed by a high-frequency glow discharge method, a vacuum deposition method, and a sputtering method.
A p-i-n junction is formed.

In recent years, research examples using π-conjugated polymers in semiconductor layers have been reported (for example, Journal of
Electrochemical Society Volume 129, 173
7 (1982), Applied Physical Letter, Vol. 62, 585, (1993), etc.).

[0005]

When the above π-conjugated polymer is used as a semiconductor layer, a thin film can be easily formed by a low temperature process, and thus it is possible to cope with large area and large scale integration. It has advantages such as flexibility. However, there is a problem that the photoelectric conversion efficiency of this element is lower than that of the element using an inorganic semiconductor.

An object of the present invention is to increase the area,
Provided is a flexible photoelectric conversion element which uses a π-conjugated polymer and can improve its photoelectric conversion efficiency when used in a solar cell as compared with that of an inorganic semiconductor / π-conjugated polymer solar cell. Especially.

[0007]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention formed a π-conjugated polymer layer on a semiconductor layer composed of a layer containing fullerene, thereby forming an interface between the two layers. The present invention has been completed by finding that an element having such a strong bond and thus configured can achieve the object of the present invention.

That is, the present invention relates to a semiconductor layer containing fullerene, and a photoelectrolytic polymerization π formed on the semiconductor layer.
A gist is a photoelectric conversion element comprising a conjugated polymer layer.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described with reference to FIGS.

FIG. 1 is a sectional view of an example of the photoelectric conversion element of the present invention. In FIG. 1, the π-conjugated polymer layer 12 is formed on the fullerene thin film layer 11.

Fullerenes are substances in which carbon atoms are bonded in a higher order, and those in which 60 carbon atoms are bonded (hereinafter, C ₆₀
Is displayed. ), C ₇₀ , C ₇₆ , C ₈₂ , C ₈₄ , C ₉₀ ,
C _{96 and the} like and higher ones are known. In the present invention,
Either of them can be used. These fullerenes are
A crystalline or amorphous fullerene thin film is formed by a vapor deposition method, a molecular beam epitaxy (MBE) method, a sputtering method, a spray coating method or a cast method. Among the above, a thin film produced by a vapor deposition method is preferable.

The form of fullerene used is preferably amorphous fullerene rather than crystalline fullerene.
This control can be easily realized by controlling the substrate temperature in the vapor deposition method, for example.

In the present invention, in addition to the fullerene alone,
A thin film obtained by dispersing fullerene in a binder made of a synthetic resin such as polycarbonate, polystyrene, or polyolefin can also be used.

In the present invention, the π-conjugated polymer forming the π-conjugated polymer layer is, for example, acetylene, pyrrole, thiophene, furan, selenophene, azulene, pyrene,
It is a homopolymer of unsaturated monomers such as benzothiophene, indole, carbazole, isonaphthene, diacetylene, phenylene vinylene and thienylene vinylene.
Derivatives of those homopolymers can also be used.

In the present invention, the method of forming the π-conjugated polymer layer on the fullerene-containing layer is important, and the photoelectrolytic polymerization method is used. The method is a method of electrolytically polymerizing the above-mentioned unsaturated monomer on a layer containing fullerene under irradiation of light to form a π-conjugated polymer layer composed of a homopolymer thereof. FIG. 2 shows a process for producing a fullerene / π-conjugated polymer laminated film.

As the electrolytic solution 21, a solution composed of the unsaturated monomer, the supporting electrolyte and the solvent of the supporting electrolyte is used. The supporting electrolyte is not particularly limited as long as it dissolves in a solvent and dissociates. Typical supporting electrolytes include chlorides of alkali metals such as sodium chloride and potassium chloride, alkylammonium salts such as tetrabutylammonium tetrafluoroborate, and the like.

Examples of the solvent include water, alcohols, ethers, ketones, nitriles, amines, amides, sulfur compounds or nitromethane, nitrobenzene, dichloromethane, 1,2-dichloroethane, propylene carbonate and ethylene carbonate. Can be mentioned.

In the above electrolytic solution, a fullerene-containing thin film as a working electrode 22, a conductor such as platinum or carbon as a counter electrode 23, a calomel electrode as a reference electrode 24, Ag /
The AgCl electrode or the Ag electrode is dipped, a constant current connected to a galvanostat (constant current electrolysis power source) 25 is passed, and the fullerene thin film is irradiated with light using a light source 26 such as a halogen lamp. Since the fullerene has photoconductivity, the fullerene thin film behaves as a conductive substrate only while being irradiated with light. That is, by irradiating the fullerene thin film with light, a π-conjugated polymer layer is formed at the interface. It becomes possible to form a dense film by reducing the constant current, and the current density may be in the range of 0.001 to 10 mA / cm ² .

In the above, the fullerene-containing thin film 22 may be a thin film previously formed on a substrate. As the substrate, an ion crystal plate of potassium bromide, sodium chloride or the like, a transparent conductive film on a glass plate, such as IT
Examples thereof include those formed with O, metal foils such as gold foil, aluminum foil, and those obtained by forming the above metal foil on a glass plate.

Fullerene is a compound characterized by having a very high π electron density on its surface, and π-conjugated polymer is also a substance having a high π electron density. That is, the junction portion of the π-conjugated polymer layer polymerized and formed on the fullerene-containing thin film as described above can form a strong and ideal junction due to the interaction of π-π electrons.

The thickness of the layer containing fullerene is 0.0
It is desirable to be 1 to 50 μm. Further, the film thickness of the π-conjugated polymer layer formed thereon is preferably 0.1 to 10 μm.

As described above, since the photoelectric conversion element of the present invention uses fullerene in the semiconductor layer, it is possible to produce a photoelectric conversion element having a higher efficiency than in the case of using an inorganic semiconductor such as n-Si. it can. In addition, in comparison with a conventional device in which a layer containing a fullerene is provided on a π-conjugated polymer layer, π-
A strong junction interface can be formed by the interaction of π electrons. Further, the photoelectric conversion element of the present invention configured as described above is rich in flexibility and excellent in stability in the atmosphere.

Further, in the photoelectric conversion device of the present invention, if a part of the layer containing fullerene is selectively doped with a metal to develop a conductive layer, the conductive layer acts as an electrode, so that the device structure is You can make it between flights. Examples of the metal include potassium, lithium, sodium, rubidium, cesium and the like. Furthermore, a conductive layer can be provided on the fullerene-containing layer and / or the π-conjugated polymer layer of the photoelectric conversion device of the present invention. As the conductive layer,
Examples thereof include metals such as aluminum, gold, silicon and platinum, and metal oxides such as indium oxide and tin oxide.

The photoelectric conversion element of the present invention can be used in solar cells and the like.

[0025]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 In this example, a photoelectric conversion element was manufactured by the process shown in FIG.

A thin plate was prepared by forming a C ₇₀ thin film 32 having a thickness of about 0.5 μm on a KBr plate as a substrate 31 by a vacuum evaporation method. Then 10 mmol / l of pyrrole,
Acetonitrile solution 33 containing 0.1 mol / l tetrabutylammonium tetrafluoroborate 33
Then, the thin plate was immersed in the above to make a working electrode, and a counter electrode 34 made of platinum was connected to a three-electrode type constant current electrolysis device 36 using a calomel electrode 35 as a reference electrode.

From the KBr direction of the working electrode, the halogen lamp 3
7 to irradiate light, during which the current density is 0.2 mA / cm
² constant current electrolysis was performed. As a result, it was possible to quickly obtain the photoelectrolytic polymerized film 38 of pyrrole on the C ₇₀ thin film 32. The film thickness of the polymer film 38 was about 0.5 μm.

Then, the composite film obtained above is immersed in pure water to dissolve the KBr layer to form a composite film of the C ₇₀ thin film 32 and the polypyrrole thin film 38, which is vacuum dried at 100 ° C. for a whole day and night. The photoelectric conversion element of the invention was produced.

The photoelectric conversion device produced above, 1 mW / c
Irradiation was carried out with an argon ion laser having an intensity of m ² . The current-voltage characteristic curve obtained at that time is shown in FIG. Here, the release voltage (V oc) was 0.89 V and the short-circuit current was 6.18 μA / cm ² . The fill factor (FF) is 0.60, and the output conversion efficiency is 0.
It was 06%.

Example 2 In the same manner as in Example 1, C ₇₀
A photoelectric conversion element of the present invention comprising a composite film of a thin film 51 and a polypyrrole thin film 52 was prepared, and as shown in FIG. 5, a polypyrrole thin film 52 side was masked and a C ₇₀ thin film 51 side was an aluminum layer (Al layer). 53 was vapor deposited. The film thickness of the Al layer 53 was about 0.1 μm.

Next, C of the above-mentioned aluminum vapor deposition device is used.
Argon ion laser irradiation was performed from the ₇₀ thin film 51 side in the same manner as in Example 1. The current-voltage characteristic curve obtained at that time is shown in FIG. Here, V oc was 0.95 V and the short-circuit current was 7.01 μA / cm ² . or,
The FF was 0.62 and the output conversion efficiency was 0.07%.

Example 3 In the same manner as in Example 1, C ₇₀
A photoelectric conversion element of the present invention comprising a composite film of a thin film and a polypyrrole thin film was prepared, and as shown in FIG. 7, after masking the polypyrrole thin film 72 side, potassium was doped from the C ₇₀ thin film 71 side to form K ₃ C _{70 A} thin film 73 was produced. ESCA, which is one of the electron spectroscopy methods using X-rays, gives K ₃ C.
_{When the} film thickness of the ₇₀ thin film 73 was measured, it was about 0.1 μm.

Then, an argon ion laser was irradiated from the C ₇₀ thin film 71 side of the above potassium-doped element in the same manner as in Example 1. The current-voltage characteristic curve obtained at that time showed the same characteristic as in FIG.

(Embodiment 4) In the same manner as in Embodiment 1, C ₇₀
A photoelectric conversion element of the present invention composed of a composite film of a thin film 81 and a polypyrrole thin film 82 was prepared, a polypyrrole thin film 82 side was masked, and then aluminum (Al) was vapor-deposited on the C ₇₀ thin film 81 side as shown in FIG. did. The film thickness of the Al layer 83 was about 0.1 μm. Next, the Al layer 83 was masked, and gold (Au) was vapor-deposited on the polypyrrole thin film 82 side.
The film thickness of the Au layer 84 was about 0.1 μm.

Next, an argon ion laser was irradiated from the C ₇₀ thin film 81 side of the above element in the same manner as in Example 1. The current-voltage characteristic curve obtained at that time is shown in FIG. Here, V oc was 0.90 V and the short-circuit current was 8.30 μA / cm ² . The FF was 0.65 and the output conversion efficiency was 0.07%.

(Comparative Example 1) A transparent conductive glass (glass / ITO) was immersed in an acetonitrile solution containing 10 mmol / liter of pyrrole and 0.1 mol / liter of tetrabutylammonium tetrafluoroborate to form a working electrode, and platinum was used. Was connected to a counter electrode and a three-electrode type constant current electrolysis device using a calomel electrode as a reference electrode. Constant current electrolysis was performed at a current density of 0.2 mA / cm ² to obtain a polypyrrole electropolymerized film. The thickness of polypyrrole thin film is about 0.5
μm.

This thin film was dried in a vacuum dryer at 100 ° C. for 24 hours, and then C was deposited on this thin film by vacuum deposition.
₇₀ was vapor-deposited by about 0.5 μm. Then, on the C ₇₀ thin film, A
A photoelectric conversion element was produced by vapor-depositing 1 of about 0.1 μm into an electrode. The above steps are shown in FIG.

Next, the C ₇₀ thin film 10 of the photoelectric conversion element described above is used.
Irradiation with an argon ion laser was performed from the 4 side in the same manner as in Example 1. The current-voltage characteristic curve obtained at that time is shown in FIG. Here, V oc is 0.70V,
The short-circuit current was 5.20 μA / cm ² . The FF was 0.25 and the output conversion efficiency was 0.02%.

[0040]

EFFECTS OF THE INVENTION The photoelectric conversion device of the present invention has a structure in which the fullerene-containing layer and the π-conjugated polymer layer formed on the layer by the photoelectrolytic polymerization method are used so that the interface between both layers is They are firmly and ideally bonded, and as a result, the conversion efficiency is remarkably excellent as compared with the conventional photoelectric conversion element composed of a semiconductor / π-conjugated polymer layer.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example of a photoelectric conversion element of the present invention.

FIG. 2 is a schematic view of a photoelectrolytic polymerization apparatus for producing the photoelectric conversion element of the present invention.

FIG. 3 is a cross-sectional view showing the manufacturing process of the photoelectric conversion element according to the first embodiment of the present invention.

FIG. 4 is a current-voltage curve of the photoelectric conversion element obtained in Example 1 of the present invention during light irradiation.

FIG. 5 is a cross-sectional view showing the manufacturing process of the photoelectric conversion element according to the second embodiment of the present invention.

FIG. 6 is a current-voltage curve at the time of light irradiation of the photoelectric conversion element obtained in Example 2 of the present invention.

FIG. 7 is a cross-sectional view showing the manufacturing process of the photoelectric conversion element according to the third embodiment of the present invention.

FIG. 8 is a cross-sectional view showing the manufacturing process of the photoelectric conversion element according to the fourth embodiment of the present invention.

FIG. 9 is a current-voltage curve of the photoelectric conversion element obtained in Example 4 of the present invention during light irradiation.

FIG. 10 is a cross-sectional view showing the manufacturing process of the photoelectric conversion element in Comparative Example 1 of the present invention.

FIG. 11 is a current-voltage curve of the photoelectric conversion element obtained in Comparative Example 1 of the present invention during light irradiation.

[Explanation of symbols]

11 Fullerene layer 12 π-conjugated polymer layer 32, 51, _71, 81, 104 C ₇₀ thin film 38, 52, 72, 82, 103 Polypyrrole thin film 21, 33 Electrolyte 22 Working electrode 23, 34 Counter electrode 24, 35 Reference electrode 25 , 36 constant current power source 26, 37 light source 31 KBr 53, 83, 105 Al layer 84 Au layer 101 glass 102 ITO

Claims (1)

[Claims] 1. A photoelectric conversion device comprising a semiconductor layer containing fullerene, and a photoelectrolytic polymerization π-conjugated polymer layer formed on the semiconductor layer.