JPH05206489A - Photoelectric conversion device - Google Patents

Abstract

PURPOSE:To provide an optical sensor which incorporates an effective information processing function in terms of visual information processing. CONSTITUTION:The surface of a conductive electrode is coated with a photo-sensitive pigment layer capable of carrying out optical isomerization reaction by way of an insulating thin film whose thickness is virtually uniform on the surface of a conductive electrode, thereby forming an optical conversion device which includes an optical conductive conversion element constituted by an ion conductive electrolyte bonded with the pigment layer. Therefore, this device is provided with a feature which responds electrically to the intensity of light in a differential manner and capable of using is effectively as a light receiving pixel which constitutes an image sensor having a visual information processing power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel structure of a photoelectric conversion type optical sensor using an organic dye material in a photosensitive layer. INDUSTRIAL APPLICABILITY The photoelectric conversion element of the present invention has a characteristic of differentially electrically responding to the intensity of light, and can be effectively used as a light receiving pixel that constitutes an image sensor having visual information processing capability.

[0002]

2. Description of the Related Art As a photoelectric conversion type device using a photosensitive organic dye material, a sandwich type optical voltaic cell formed by joining a thin film of an organic dye between two kinds of conductive electrodes is most suitable. It is common. Although various types of dye materials have been tried as the dye materials used in such photoelectric conversion elements, a typical one is DL Morel eta.
l., Appl. Phys. Lett., 32, p495 (1978) and K. Sakai e.
t al., Jap. J. Appl. Phy., p865 (1985), a merocyanine dye, AK Ghosh et al., J. Appl. Phy
s., 45, p230 (1974) and ZD Popovic and JH Sharp,
Phthalocyanine derivative described in J. Chem. Phys., 66, p5076 (1977), JP Dodelet et al., Photochem. Photob
Materials having photoconductivity such as chlorophyll described in iol., 29, p1135 (1979) are known.

Further, as a general photoelectric conversion cell other than the above, there is a dye-sensitized photoelectrochemical cell in which a dye-coated electrode is used in an electrolytic aqueous solution, for example, N. Minam.
i et al., Ber. Bunsenges. Phys. Chem., 83, p476 (19
79) Example using metal phthalocyanine, T. Kawai et a
l., Chem. Phys. Lett., 56, p541 (1978) using porphyrin, T. Miyasaka et al., Photochem. P.
hotobiol., 32, p217 (1980) using chlorophyll, W. Arden and P. Fromherz, J. Electrochem. So
c., 127, p370 (1980) shows an example using a cyanine dye. In the above various photoelectric conversion systems, the light in the visible wavelength range absorbed by the dye is the electromotive force (voltaic cell).
Or it is converted into electrical energy such as electric current.

In the conventional photoelectric conversion method as described above, there are differences in sensitivity and whether the output is electromotive force or current, but
A steady quantity of electricity that reflects the intensity of the input light is finally output. That is, the device gives a stationary output depending on the light intensity under the incidence of stationary light. This point is similar to the existing solid-state photosensor including a photodiode.

However, in visual information processing, which has become more and more important in recent years, for the purpose of constructing an optical sensor having a built-in information processing function effective for this, a sensor that is differentially sensitive to the input light intensity is used. Realization of will become important. Such a differential response type optical sensor can be obtained by combining an existing photodiode with a differentiating circuit (CR circuit), but in order to minimize the load on the circuit, it does not depend on the circuit technology, It is important that the photosensitive element itself has a differential response, and the above-mentioned existing organic photoelectric conversion element cannot achieve this purpose.

[0006]

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a photoelectric conversion device which differentially electrically responds to the intensity of light.

[0007]

Differential type electrical response is a phenomenon that is often seen in the pattern of capacitive current during charging and discharging of a capacitor. Such a capacitive current pattern can be successfully realized by using a specific organic molecule that causes vector-like charge transfer or dipole change in the photoreaction process. A specific organic molecule is an organic molecule in which charge transfer is effectively stored as a change in capacity without being amortized by redox of the organic molecule or electron transfer with an external material.

Although such organic molecules are extremely limited, bacteriorhodopsin disclosed in JP-A-3-205520 is a typical example. In bacteriorhodopsin, the retinal molecule that triggers the transfer of charge is surrounded by the walls of the protein, so that the chemical redox decomposition of retinal is almost completely suppressed. Therefore, in order to obtain the same effect as that of bacteriorhodopsin by using a more versatile general photosensitive organic dye, at least the photosensitive dye is isolated from the electrode material that electrochemically contributes to redox. The need arises.

The above problem is that the surface of the conductive electrode is coated with a layer of a photosensitive dye capable of performing a photoisomerization reaction through an insulating thin film having a substantially uniform thickness, and the dye layer is coated with the photosensitive dye layer. This can be achieved by a photoelectric conversion element characterized by including a photoelectric conversion element configured by bonding an ion conductive electrolyte.

The photoelectric conversion element of the present invention is characterized in that the layer structure is in the following order. Conductive electrode substrate / insulating thin film / photosensitive dye layer / ion conductive electrolyte / counter electrode

As materials for the conductive electrode substrate and the counter electrode, various corrosion-resistant oxide and noble metal electrodes which are commonly used in electrochemical cells can be applied. Tin oxide and indium oxide are particularly preferable as the oxide electrode, and gold, platinum and silver are particularly preferable as the noble metal electrode. What is preferable as a conductive electrode in terms of corrosion resistance and optical transparency is an electrode made of tin oxide and indium oxide. However, one of the conductive electrode and the counter electrode on which the photosensitive dye layer is carried needs to be transparent in the wavelength region of the light absorbed by the photosensitive dye layer.

In the above layer structure, a reference electrode can be added to the ion conductive electrolyte layer as a third electrode, if necessary. Preferred as the reference electrode are silver / silver chloride electrodes, mercury-based electrodes such as saturated calomel, and silver / silver chloride electrodes are particularly preferred.

The insulating thin film serves as a blocking layer that blocks electron exchange between the dye and the electrode in the present invention. For that purpose, the thin film should have a uniform thickness, and its average thickness should be large enough to make the probability of local tunneling of electrons small enough.
It is desired that the thickness is at least 5 nm or more. On the other hand, the insulating film needs to be not too thick in order that the movement of charges generated in the dye layer can be transmitted to the electrode as an electrostatic effect with sufficient sensitivity, and is preferably 500 nm or less. As the insulating material, inorganic substances such as Si, S
iO _2, inorganic oxides and lipids such as Al ₂ O _3, an organic polymer compound represented by the polymer such as polyimide can be used.

When lipids having a hydrophobic alkyl chain are used as an insulating film as a Langmuir-Blodgett (LB) film, it is desirable that the number of layers of the LB film is at least 5 or more.

As the ion conductive electrolyte, an electrolytic aqueous solution containing a supporting salt and a polymer solid electrolyte using a polymer organic material as a medium are effective. The concentration of the supporting electrolyte is preferably in the range of 0.1 to 5 mol / L. As the medium for the polymer electrolyte, for example, gelatin, agar, chitin and chitosan derivatives, polyacrylamide, polyvinyl alcohol and other water-soluble polymers can be used.
These media are preferably dissolved in water together with the supporting salt and used in a gel state.

If necessary, an appropriate dye or pigment for preventing halation or a weathering agent for preventing oxidation of the photosensitive dye may be added to the ion conductive electrolyte. Further, it is desirable that the ion conductive electrolyte be used after being deoxidized by introducing an inert gas such as nitrogen or argon.

Next, the photosensitive dye material used in the present invention will be described. As the photosensitive dye used in the present invention, those which cause a large change in the distribution of charges on the molecule or the dipole moment of the molecule under photoexcitation can be widely applied. Typical of such dyes are azobenzene derivatives, retinal derivatives, spirooxazine derivatives,
Photoisomerization dyes such as spiropyran derivatives and fulgide derivatives.

Discharge of charge generated under photoexcitation
nt) is electrostatically transmitted to the underlying conductive electrode through the insulating film, where an induced current is generated. Since the dye is fixed at the interface between the insulating film and the electrolyte, it is preferably insoluble in water. The water-insoluble dye can be coated on the insulating film by a spin coating method, a vacuum vapor deposition method, a Langmuir-Blodgett (LB) method, or another commonly used thin film forming method. When the dye is not insoluble in water, it can be used by a method in which the dye is once dispersed in a suitable water-insoluble binder material (polymer compound or resin) and coated on the insulating film together with the binder material.

Examples of useful polymeric materials for binders include, for example, cellulose resins, polystyrene, polyvinyl chloride, polymethylmethacrylate, polyacrylamides, polyesters, polycarbonates, polyimides, and general water-insoluble polymers. Can be used. A hardener can also be added to the binder.

Examples of the photosensitive dye material that can be effectively used in the present invention are given below.

[0021]

[Chemical 1]

[0022]

[Chemical 2]

[0023]

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[0024]

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[0025]

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[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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[0032]

[Chemical 12]

[0033]

[Chemical 13]

[0034]

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[0035]

[Chemical 15]

Examples of the present invention will be shown below, but the preferred embodiments of the present invention are not limited to these.

[0037]

Example 1 A thin film of tin oxide (thickness: 45
The surface of a tin oxide electrode substrate coated with 00 angstrom and an electric resistance of 10 Ω / cm ² ) was coated with M. Suzuki et al Ch
L according to the method described in em. Lett., p395 (1986).
By the method B, a polyimide monomolecular film (thickness 40 Å) was laminated and covered under a surface pressure of 10 mN / cm to a thickness of 5 to 6 layers, and a polyimide insulating film was provided on the substrate.

On this insulating film, similarly by the LB method,
About 10 layers of the following azobenzene derivative films were laminated by a horizontal adhesion coating method in the same direction (hydrophobic substrate side is the substrate surface) under a surface pressure of 20 mN / cm, and an insulating film was inserted as a blocking layer on the substrate. A thin film of photosensitive dye (about 250 Å thick) was provided.

[0039]

[Chemical 16]

An electrode substrate carrying a photosensitive dye was immersed in a neutral electrolytic aqueous solution containing 0.5 mol / L of potassium chloride together with a platinum electrode as a counter electrode to prepare a photoelectric conversion cell. -0.4V DC for the dye side electrode with respect to the platinum electrode
A bias voltage was applied from the outside. Next, when the band electrode having a peak at 360 nm was irradiated from the 150 W xenon lamp to the dye electrode, a differential photocurrent response as shown in FIG. 1 was observed with respect to the light input. This is considered to be a displacement current associated with photoisomerization of the azobenzene derivative from the trans form to the cis form.

Next, when the peak of band light was changed to 450 nm and light irradiation was performed in the same manner, a differential type photocurrent response in the opposite direction to the response shown in FIG. 1 was detected. This is considered to be a displacement current that reflects the photoisomerization from cis form to trans form.

[0042]

Example 2 An electrode substrate having a vapor-deposited gold film (thickness of 1000 Å) supported on glass was used as an alkylthiol in ethanol containing 1% of HS- (CH ₂ ) ₂₁ -CH ₃ (deoxidation treatment) for 5 hours. It was immersed at room temperature to form a monomolecular film of alkylthiol on the gold surface. A monolayer of arachidic acid was coated on the surface of the substrate, which was made hydrophobic by the monolayer, by the horizontal deposition method under the surface pressure of 30 mN / m from the water surface by the LB method. By this operation, about 50 angstroms (5
(nm) uniform insulating layer was formed.

A photosensitive dye of the following structure, spirooxazine, was spun on the insulating film by a spin coater at a rotation speed of 1000.
Spin coating was performed from a 1% solution of chloroform at rpm to obtain a water-insoluble thin film having a thickness of about 900 Å and colored in blue.

[0044]

[Chemical 17]

The dye electrode thus obtained was used as 200
Indium tin oxide (ITO) electrode substrate (ITO on glass) through counter electrode via μm Teflon ring spacer
(A film thickness of 500 angstroms), insert a thin film of a gel of 2% agar solution containing 2M potassium chloride as a polyelectrolyte into the gap formed by the spacer, sandwich the gel with two electrodes and form a thin layer type The photoelectric conversion cell of was produced.

For the dye layer of spirooxazine, 15
As a result of irradiating white light as an ON / OFF rectangular wave from a 0W tungsten / halogen lamp through an ITO electrode, 2
A differential-type photocurrent response similar to that of FIG. 1 occurred in response to the pattern of light input between the electrodes. This photocurrent response reflects the dipole change caused by the structural change between the spirooxazine and its structural isomer, the merocyanine body, which is one of the displacement currents.
Considered to be a seed.

[Brief description of drawings]

FIG. 1 is a diagram showing a pattern of photoresponse when a photoelectric conversion element of the present invention is irradiated with light.

Claims (4)

[Claims] 1. A surface of a conductive electrode is coated with a layer of a photosensitive dye capable of performing a photoisomerization reaction through an insulating thin film having a substantially uniform thickness, and the dye layer has ion conductivity. A photoelectric conversion element comprising a photoelectric conversion element configured by joining an electrolyte. 2. The photoelectric conversion element according to claim 1, wherein the photosensitive dye is a photosensitive dye selected from an azobenzene derivative, a retinal derivative, a spirooxazine derivative, a spiropyran derivative and a fulgide derivative. 3. The photoelectric conversion element according to claim 1, wherein the thickness of the insulating thin film is substantially uniform and is 5 nm or more and 500 nm or less. 4. The photoelectric conversion element according to claim 1, wherein one or both of the insulating thin film and the photosensitive dye layer is a Langmuir-Blodgett film.