JPH0612815B2 - Method for producing photoelectric conversion element using functional protein complex - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a photoelectric conversion element, and more particularly to a method for producing a photoelectric conversion element using a photosynthetic reaction unit obtained from a photosynthetic organism.

[Prior Art] Photosynthetic organisms such as plants and photosynthetic bacteria have photosynthetic organs involved in photosynthetic reactions. Photosynthetic organs include lipids, photosynthetic units, oxidoreductases, and the like. The photosynthetic granules obtained as the fragments are normally closed vesicles composed of a membrane composed of chromatophores, proteins such as spheroplast membrane vesicles, lipids and the like. It is known that this type of membrane has a functional protein complex including a photosynthetic reaction center protein complex that performs a photoelectric conversion reaction, and a potential difference is generated across the membrane by photostimulation.

The photosynthetic granule is a vesicle in which a lipid bilayer is divided, and a functional protein complex having a photosynthetic function is embedded in the vesicle. This functional protein complex has an activity of absorbing light and inducing charge separation.

Since the electrons generated as a result of charge separation move through a specific pathway of the complex, the function of this functional protein complex has polarity (direction). In the living body, the functional protein complex is regularly oriented so that the directions are aligned.

The photosynthetic organ of the red-colored Empress bacterium has a protein complex called a photosynthetic reaction unit embedded in a vesicular, lamellar, or tubular membrane structure composed of lipid bilayers. A chromatophore is known as one of the structures in which this photosynthetic organ is taken out of the cell.

A chromatophore is a photosynthetic granule obtained when a photosynthetic bacterium is disrupted by a method such as ultrasonication, and a photosynthetic reaction unit is embedded in a lipid bilayer.

The chromatophore is a structure having a complicated molecular composition in which a protein of the electron transfer system, a redox enzyme, etc. are mixed in addition to the photosynthetic reaction unit, and is a vesicle having a diameter of about 60 to 100 nm.

3 (A) and 3 (B), the present inventors have previously proposed,
1 shows a simple photoelectric conversion device in which photosynthetic granules of red photosynthetic bacteria are sandwiched between two types of electrodes.

In FIG. 3 (A), a transparent electrode such as ITO (indium tin oxide) or NESA (trade name) or a light transmissive electrode 2 such as a vapor deposited Au thin film is formed on a substrate 1, and photosynthetic granules are formed thereon. A solidified film 3 is formed by applying and drying (chromophore, spheroplast membrane vesicles, etc.). The counter electrode 4 is provided on the solidified film 3 by a method such as vapor deposition.
Lead wires 5 are drawn from the upper and lower electrodes.

FIG. 3 (B) shows another configuration example of the photoelectric conversion element, which is different from the configuration in FIG. 3 (A) in that the upper counter electrode 4 is not a deposited film such as a vapor deposition film but a mercury ball. The other points are the same as in FIG. 3 (A).

In the photoelectric conversion element shown in FIGS. 3A and 3B, light is incident from the substrate side, and the photoresponse generated by the solidified film 3 of the photosynthetic granules is extracted from the lead wire 5 via the electrodes 2 and 4.

In the photoelectric conversion element using conventional photosynthetic granules,
No special consideration was given to aligning the direction of the photoelectric response of the photosynthetic granules.

For example, since the chromatophore is a vesicle, it is considered that the control of the molecular orientation is difficult and the control of the molecular composition is not easy when constructing a device that applies the function of the photosynthetic reaction unit.

Therefore, the output obtained from the conventional photoelectric conversion device is the sum of the responses of the functional protein complex having a disordered directionality, the minute response, and the electron between the different electrodes and the functional protein complex. It is probable that the response was weak depending on the difference in work functions related to movement.

[Problems to be Solved by the Invention] In the above-mentioned device, no special consideration is given to aligning the directions of the functional protein complexes in the photosynthetic granules. Therefore, the protein complex is in a disorderly direction. The photoelectric response obtained as the output is due to a slight difference between the two electrodes 2 and 4 as the sum of reactions having a disordered directionality, and the work function of electron transfer between the protein complex and the electrode. It is considered to be a weak response that depends on the difference between

Therefore, it cannot be said that the photoelectric conversion element as shown in FIGS. 3 (A) and 3 (B) described above sufficiently utilizes the response of the photosynthetic function of the functional protein complex such as the purple photosynthetic bacterium. It is believed that only a small part of it is taken out.

The present invention is to provide a method for producing a photoelectric conversion element which can give a sufficient orientation to the functional protein complex in the photoelectric conversion element using the functional protein complex.

[Means for Solving the Problems] According to the present invention, after forming a photoelectric conversion element structure, an electric field having a polarity is applied between the electrodes to align the functional protein complex sandwiched between the electrodes. Take control.

[Action] A protein molecule has an electric dipole due to a charge distribution based on an amino acid sequence, and in the electric field, this electric dipole interacts with the electric field. When a polar electric field is applied to a photoelectric conversion element sandwiching a functional protein complex between electrodes, the orientation of the protein molecule is controlled by the interaction between the electric dipole of the protein molecule and the electric field.

[Examples] Photosynthetic granules are prepared by crushing photosynthetic bacteria cultured under light irradiation by a method such as ultrasonic treatment or French press, and then purifying by fractional centrifugation.

1 (A) and 1 (B) show the cross-sectional structure of a photoelectric conversion element manufactured according to an embodiment of the present invention.

A transparent electrode 2 such as ITO or NESA is formed on a transparent substrate 1 such as glass by a method such as vacuum deposition, sputtering or ion plating.

The photosynthetic granules produced as described above are applied onto the transparent electrode 2 by a method such as brush coating, dipping, spin coating, screen printing, offset printing, etc., and dried. Drying is natural drying,
It can be performed by vacuum drying, heat drying, or the like. After drying, a metal film is vapor-deposited on the dried and solidified film 3 of the photosynthetic granules by vacuum vapor deposition, sputtering or the like to form the counter electrode 4.

In FIG. 1 (B), the counter electrode 4 is formed by pressing a metal foil.

The lead wire 5 is pulled out from the transparent electrode 2 and the counter electrode 4.

An electric field having a polarity is applied to the functional protein complex of the photoelectric conversion element thus formed via the lead wire 5 electrodes 2 and 4. For example, pulsed DC electric field, steady DC electric field,
An AC electric field with a DC bias electric field added is applied.

FIG. 2 shows an example of a voltage waveform applied between the electrodes 2 and 4 when a pulsed electric field having polarity is applied.

The functional protein complex in the photosynthetic granule enhances the orientation in the electric field. This alignment adjustment improves the photoelectric response of the device.

By applying a polar electric field, the structure of the lipid bilayer in which the functional protein complex is embedded is destroyed, and the electric dipole potentially possessed by the protein molecule interacts with the electric field, causing photosynthesis. It is considered that the functional protein complex responsible for the function is oriented in the electric field direction. It is considered that after removing the electric field, the lipid bilayer is spontaneously restored, and a device having high orientation is obtained.

Further, in the conventional photoelectric conversion element, it is difficult to avoid pinholes in the dried and solidified film, and there are locally low resistance portions and conductive portions, resulting in non-uniform characteristics.
However, it is considered that by applying the electric field as described above, a large current flows through these low resistance (conduction) portions at the initial stage of conduction, and the portions are burned out, whereby defects can be removed. Defect removal increases the uniformity of properties.

From the transparent electrode 2 side of the photoelectric conversion element thus configured,
Irradiation with sunlight, LED light, strobe light, laser light, arc lamp light, etc. was performed to measure potential and current changes in photoelectric response.

As an example, a glass substrate is used as the substrate 1, an ITO transparent electrode is used as the transparent electrode 2, and Rhodopseudomonas viridis (AT) is used as the solidified film 3 of the functional protein complex.
A solidified film obtained by drying the chromatophore of CC19567) was used, and a gold vapor deposition film was used as the counter electrode 4. The thickness of the solidified film 3 is estimated to be about 1 to 10 μm. Between the electrodes 2 and 4 of this element, a pulsed DC voltage (1H
z, peak value 75 to 150 V, 0.5 to 2 hours), and the electric field strength is 10 ⁷ to 10 when a voltage of 100 V is applied.
^It is estimated to be about ⁸ V / m. It should be noted that 10 nm for biological membranes
A membrane potential of about 100 mV is generated in the lipid bilayer having a certain thickness due to the avoidance of ion concentration inside and outside the cell. This electric field strength is about 10 ⁷ V / m. That is, it means that an electric field having an intensity that is equivalent to about 10 times the electric field intensity to which the functional protein complex is exposed in the living body is applied.

The photoelectric conversion element thus subjected to the alignment treatment was irradiated with LED light (having an emission peak at 850 nm), and the photoelectric response was measured. For comparison, measurement was performed before and after the alignment treatment. By the orientation process of applying a pulsed DC electric field, the voltage response is 20 to 100 times and the current response is about 2 compared to before treatment
Responses of 5-100 fold were obtained.

The polarity of the response obtained by reversing the polarity of the applied electric field was also reversed.

From this, it is understood that the orientation of the functional protein complex is controlled by applying a polar electric field.

[Effects of the Invention] According to the present invention, the photosynthetic granules that can be easily cultured can be used as the material source and the photosynthetic granules that can be produced by a very simple method as compared with the semiconductor material can be used as they are to achieve efficient photoelectric conversion. Reactive elements can be manufactured.

According to the present invention, after the photoelectric conversion device structure is prepared by using the conventional technique, the electrical treatment is carried out to overcome the lack of orientation which is a problem in the functional photoelectric conversion device, and the functional protein composite is obtained. It is possible to provide a highly efficient photoelectric response element in which the body orientation is controlled.

By controlling the applied electric field, the orientation direction of the protein complex can be easily controlled.

A far larger photoelectric reaction can be obtained as compared with a conventional photoelectric conversion device using a functional protein complex.

Further, as an additional effect of applying an electric field, it is possible to burn off a low resistance current path derived from a pinhole in the dried and solidified film to obtain a more uniform characteristic.

[Brief description of drawings]

1 (A) and 1 (B) are cross-sectional views showing a configuration example of a photoelectric conversion element manufactured according to the present invention, and FIG. 2 is a direct current applied to the photoelectric conversion element shown in FIGS. 1 (A) and 1 (B). A graph showing an example of a pulsed electric field, and FIGS. 3A and 3B are cross-sectional views showing an example of the structure of a photoelectric conversion element according to a conventional technique. In the figure, 1 ... Substrate 2 ... Transparent electrode 3 ... Solidified film of functional protein complex 4 ... Counter electrode 5 ... Lead

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location H01L 49/00 Z 8728-4M (72) Inventor Sugio Kawamura 1-3-1 East, Tsukuba-shi, Ibaraki (72) Inventor, Toshikazu Majima, 1-4 Umezono, Tsukuba, Ibaraki Prefecture (72) Inside, Institute of Electronic Technology, Institute of Industrial Technology (72) Hiroaki Sugino, Tokodai, Tsukuba, Ibaraki Prefecture No. 5 5 Stanley Electric Co., Ltd. Tsukuba Research Center (72) Inventor Yasuyuki Kawakami Tokodai 5 Tsukuba City, Ibaraki Prefecture No. 5 No. 5 Stanley Electric Co., Ltd. Tsukuba Research Center (72) Inventor Shuichi Azushi Tokodai Tsukuba City Ibaraki Prefecture 5-9, 5 Stanley Electric Co., Ltd., Tsukuba Research Center (72) Inventor Hideki Toyodama East of Tsukuba City, Ibaraki Prefecture Stand 5-chome 5 Stanley Electric Co., Ltd. Tsukuba Research Laboratories in the examiner Ushiroya Yoichi of the address 9 (56) Reference Patent Sho 63-237585 (JP, A)

Claims (2)

[Claims] 1. A step of forming a photoelectric conversion element structure in which photosynthetic granules are sandwiched between electrodes on a substrate, and after forming the photoelectric conversion element structure, an electric field having a polarity is applied between the electrodes, and this electric field and photosynthesis are applied. And a step of controlling the orientation of the functional protein complex by utilizing the interaction of the protein molecule of the functional protein complex contained in the granule with the electric dipole. 2. The method for producing a photoelectric conversion element according to claim 1, wherein photosynthetic granules of purple photosynthetic bacteria are used as the photosynthetic granules.