JPH04270926A - Method for manufacturing photoelectric conversion elements - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a photoelectric conversion element using a biopolymer composite having a photoelectric conversion function.

0002

[Prior Art] Photosynthetic bacteria have photosynthetic organs as inner membrane structures. Photosynthetic organs contain lipids, photosynthetic units, oxidoreductases, etc., and the photosynthetic granules obtained as fragments are closed vesicles composed of membranes made of proteins, lipids, etc., such as chromatophores and spheroplast vesicles. It is. This type of membrane has a photosynthetic reaction center protein complex that performs photoelectric conversion reactions, and when stimulated by light, it sandwiches the membrane and generates a potential difference.

[0003] Membrane fragments such as chromatophores can be obtained by disrupting bacterial cell membranes by methods such as ultrasonication. Photosynthetic membrane fragments such as chromatophores, photoreaction units, and reaction centers are photosynthetic proteins (collectively referred to as photosynthetic granules) that
Photoelectric conversion elements that utilize light stimulation to cause charge separation and electron transfer have been considered (Japanese Unexamined Patent Publication No. 1999-1-1).
No. 10224).

As shown in FIG. 2, this photoelectric conversion element has an I
A dried solidified film of photosynthetic granules that will become the photoelectric conversion active layer 1 is provided on a glass substrate 4 on which a transparent electrode 3 of TO (indium-tin oxide) or the like is formed, and an upper counter electrode 2 is further formed by Au vapor deposition or the like. There is. Silver paste 5 from each electrode 2, 3
A lead wire 6 is led out through the.

Electric power can be obtained by irradiating this element with light from the transparent electrode 3 side.

However, in such conventional devices, since vacuum evaporation has been mainly used as a method for forming the upper counter electrode, the photoelectric conversion active layer 1 is a monomolecular layer prepared by the Langmuir-Blodgett (LB) method or the like. If the film thickness is extremely thin, such as when the film is made up of a multilayer structure or a laminated layer thereof, there is a drawback that conduction will occur between the two electrodes through the element. It was necessary to intervene. In this case, the element becomes a capacitive type and no direct current flows, so a response signal is generated when the input changes.

Furthermore, in the method of forming the upper counter electrode by vacuum evaporation, the biopolymer constituting the photoelectric conversion active layer is exposed to high-temperature metal vapor or receives the heat, resulting in local protein denaturation. I couldn't avoid it.

[0008]

[Problems to be Solved by the Invention] It is an object of the present invention to prevent short circuits between electrodes even on extremely thin photoelectric conversion active layers prepared by the LB method, etc., and to prevent deterioration of device characteristics due to thermal denaturation of biopolymers. This is an attempt to easily produce an upper counter electrode without causing any damage.

[0009]

[Means for Solving the Problems] The present invention is directed to the production of a photoelectric conversion element having a laminated structure of a transparent electrode, an active layer consisting of a dried and solidified film of a biopolymer composite having a photoelectric conversion function, and an upper counter electrode. , the method for forming the upper counter electrode is characterized in that the electrode material foil obtained by peeling off the vapor-deposited film of the electrode material on the water surface is scooped onto the active layer.

0010

[Operation] Since the upper counter electrode is formed by scooping the electrode material foil peeled off from the water surface onto the active layer, the electrode pair can be formed without applying strong stimulation to the active layer such as in a vacuum deposition process.

[0011] Therefore, electrodes can be formed on both sides of the thin active layer without causing a short circuit between the electrodes.

0012

EXAMPLES A method for manufacturing a photoelectric conversion element according to the present invention will be described in detail below. The structure of the element is similar to that shown in FIG.

First, the transparent electrode 5 is formed on the substrate 4. As the transparent electrode, indium tin oxide (ITO), tin dioxide (SnO2), zinc oxide (ZnO), a sufficiently thin vapor-deposited gold electrode, or the like is used.

[0014] Next, a photoelectric conversion active layer 1 is provided on this transparent electrode 3. The biopolymer complexes constituting the photoelectric conversion active layer include photosynthetic granules such as chromatophores, photosynthetic units (PRUs), and reaction centers (RCs) derived from photosynthetic bacteria, and photosynthetic protein complexes derived from other photosynthetic organisms. can be mentioned. As the photosynthetic bacteria, purple photosynthetic bacteria are preferred. Chromatophores are obtained by disrupting photosynthetic bacteria using techniques such as ultrasonication. The chromatophore in purple photosynthetic bacteria has a structure in which a photosynthetic reaction unit is embedded in a lipid bilayer. The reaction center protein, which is a structure in which the light-trapping protein complex is missing from the photosynthetic reaction unit, can be obtained by treating the chromatophore with a surfactant.

Methods for forming the active layer made of such a biopolymer composite include coating methods such as brush coating, spin coating, and printing, film formation methods by electrodeposition of photosynthetic granules, and film formation methods such as the LB method. There are cumulative methods, etc. After forming the active layer,
It is dried to form a solidified film by methods such as natural drying and vacuum drying.

The upper counter electrode 2 is formed by peeling off the vapor-deposited film of the electrode material on the water surface and scooping the electrode material foil onto the active layer. First, a thin film of an electrode material is formed on a suitable substrate such as glass slide or mica by vacuum evaporation. In this case, it may be effective to apply a very thin and uniform coating of glycerin, grease, etc. on the substrate in advance in order to promote subsequent peeling of the deposited film from the water surface.

Next, as shown in FIG. 1A, the slide glass 7 is lowered into distilled water 9, one side of the boundary of the vapor deposited film 8 is brought into contact with the water surface, and water is formed between the substrate 7 and the thin film 8. Hold until intrusion. After that, as the thin film is peeled off, the substrate 7 is slowly submerged in water, and the electrode material foil 8 of the required area is
float on the water surface.

As shown in FIG. 1(B), the ITO electrode 3,
The glass substrate 4 on which the photosynthetic granule membrane 1 is formed is submerged in water. This glass substrate 4 is gradually pulled up, and the peeling film 8 floating on the water surface is slowly scooped onto the active layer 1. Excess water is removed and dried to complete device formation. Lead wires for external connection are connected to both electrodes using silver paste or the like.

Note that it is also possible to scoop off the peeling film 8 from the upper surface thereof. In this case, when a release agent such as glycerin is provided, no release agent remains between the active layer 1 and the release agent 8, which is effective.

From the photoelectric conversion element thus produced, a photoelectric response output can be obtained by irradiating light from sunlight, a strobe, an LED, etc. from the transparent electrode side.

[0021] Specific example

(1). Culture of photosynthetic bacteria and preparation of chromatophores Rhodopseudomonas viridis (Rh)
odopseudomonas viridis, A.T.
CC 19567) was cultured at 30°C under light irradiation and anaerobic conditions. The collected cells were suspended in a buffer solution, and the cell membrane was disrupted using ultrasound. Chromatophores were then prepared by differential centrifugation. The chromatophores were homogenized and uniformly suspended in a buffer solution.

(2). Preparation of reaction center protein The reaction center protein was prepared by solubilizing the above chromatophore with surfactant DDAO and fractionating the solubilized supernatant by gel filtration chromatography.

(3). Formation of photoelectric conversion active layer The photoelectric conversion active layer is formed by the LB method in which a monomolecular film obtained by spreading and compressing the reaction center protein at the air-water interface is accumulated on a glass substrate on which an ITO electrode is formed. I did it.

In this example, a cumulative number of photoelectric conversion active layers of 50 to 100 layers was used.

(4). Formation of upper counter electrode A thin gold film (thickness: 20 nm) was deposited on a slide glass through a mask having an opening pattern of a desired shape, and was peeled off onto the water surface using the above method, and placed on the active layer of the reaction center LB film. Scoop it out,
It was dried and used as an upper counter electrode.

When producing the upper counter electrode of a photoelectric conversion element having an extremely thin active layer such as an LB film, if the electrode is formed by the conventional direct vacuum deposition method, conduction between the two electrodes cannot be avoided. For example, L of the 100-layer reaction center protein prepared in this example.
Even in an element having the B film as an active layer, conduction occurs, and it is necessary to interpose some kind of insulating protective layer in the element. On the other hand, in the above-mentioned example, the upper counter electrode could be formed without electrical conduction even on the extremely thin active layer with a cumulative number of about 50 layers. In addition, in the device with an insulating protective layer, only a transient photoelectric response could be observed, but in the device of this example, a photoelectric response including steady current and voltage components accompanying light irradiation was observed. be done.

Furthermore, in the vacuum evaporation method, since the active layer comes into contact with the high-temperature vapor of the electrode material, the possibility of local thermal denaturation of proteins in the vicinity of the electrode could not be ruled out. In this example, since the upper electrode is formed by a method similar to the active layer accumulation method, the risk of deterioration of device characteristics due to thermal denaturation of protein molecules can be reduced.

[0029] Such a photoelectric conversion element can be used as an optical sensor.
It is extremely useful as an element for solar cells, etc.

[0030] The present invention has been explained above in accordance with the embodiments, but
The present invention is not limited to these. for example,
It will be obvious to those skilled in the art that various changes, improvements, combinations, etc. are possible.

[0031]

[Effects of the Invention] Using a biopolymer composite having a photoelectric conversion function, a photoelectric conversion element capable of effectively extracting a photoelectric response can be produced.

It is also possible to extract a DC response.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a manufacturing process of a photoelectric conversion element according to an example of the present invention. FIG. 1(A) shows the process of peeling off the vapor-deposited electrode film from the water surface, and FIG. 1(B) shows the process of scooping the vapor-deposited electrode film from the water surface onto the substrate.

FIG. 2 is a cross-sectional view showing the configuration of a photoelectric conversion element.

[Explanation of symbols]

1 Photoelectric conversion active layer (photosynthetic granule membrane) 2 Upper counter electrode (Au vapor deposited film electrode) 3 Transparent electrode 4 Transparent substrate 5 Silver paste 6 Lead wire 7 Slide glass 8 Electrode material vapor deposited film 9 Distilled water

Claims (4)

[Claims] 1. In the production of a photoelectric conversion element having a laminated structure of a transparent electrode, an active layer consisting of a dried and solidified film of a biopolymer composite having a photoelectric conversion function, and an upper counter electrode, a method for forming the upper counter electrode is disclosed. A method for producing a photoelectric conversion element, which comprises scooping an electrode material foil obtained by peeling a vapor-deposited electrode film onto an active layer onto an active layer. 2. The production method according to claim 1, wherein photosynthetic granules derived from purple photosynthetic bacteria are used in the active layer. 3. The production method according to claim 2, wherein the active layer is made of a thin film in which photosynthetic granules derived from purple photosynthetic bacteria are accumulated by the LB method. 4. The manufacturing method according to claim 1, wherein the upper counter electrode is made of gold foil.