JPH05347423A - Manufacture of optoelectric transducer - Google Patents

Abstract

PURPOSE:To manufacture an optoelectric transducer having a large photoelectric response by a method wherein an optoelectric transducing active layer is made of biopolymer composition and buffer solution is added to it to obtain a required buffer concentration. CONSTITUTION:An indium-tin-oxide electrode 1 is formed on a glass substrate 10. The ITO electrode 1 is divided into two parts 1a and 1b. An optoelectric transducing active layer 2 having a higher buffer concentration than a conventional optoelectric transducing active layer is formed on the ITO electrode 1. After the optoelectric transducing active layer 2 is dried, a gold facing electrode 3 is formed on it. The end part of the gold facing electrode 3 is connected the one part 1b of the ITO electrode 1. A drawing-out lead wire 4a is connected to the other part 1a of the ITO electrode 1 and a drawing-out lead wire 4b is connected to the gold facing electrode 3. If a light is applied to the glass substrate 10 side of an optoelectric transducer constituted as described above, the applied light transmits the glass substrate 10 and the ITO electrode 1 and falls on the optoelectric transducing active layer 2. The response of the optoelectric transducing active layer 2 is taken out through the drawing out lead wires 4a and 4b and a large photoelectric response can be obtained.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A technique for producing a photoelectric conversion element by using a biopolymer complex having a photoelectric conversion function prepared from photosynthetic bacteria is disclosed in JP-A-1-110224 and 1-2.
It is proposed in Japanese Patent No. 31886. Known methods for forming the photoelectric conversion active layer include a coating method, a printing method, an electrodeposition method, and a spin coating method.

As materials for the photoelectric conversion active layer, chromatophores (photosynthetic organ membrane fragments), spheroplasts (membrane vesicles with cell walls removed), and biopolymer complexes having a photoelectric conversion function are solubilized and purified. Samples and the like which are incorporated into liposomes after that are known.

For example, JP-A-1-110224 and JP-A-1-231886 disclose Rhodopseudomonas viridis (ATC) which is a kind of red photosynthetic bacteria.
Disclosed is a method for producing a photoelectric conversion element using a chromatophore of C19567).

By crushing the bacterial cells and fractionating, vesicles of a photosynthetic membrane fragment called a chromatophore are obtained, and the chromatophore is tris-hydrochloric acid buffer solution (pH 8.0).
A photoelectric conversion active layer is formed by using the one suspended in.

About 10 by the coating and drying method and the spin coating method.
mM Tris-HCl (pH about 7.8) was used as a buffer. Further, in the electrodeposition method, it is necessary to reduce the conductivity of the solution in order to use an electric field, and a low concentration (usually about 3 mM) of Tris-hydrochloric acid (pH about 7.8) that can maintain the buffer capacity is used as a buffer solution. Was used as.

From the photoelectric conversion device obtained by such a method, an open-circuit photovoltage of about 10 mV and a short-circuit photocurrent of about 100 pA were obtained.
A light response of a certain degree was obtained, and its duration was about several tens of milliseconds.

[0008]

As described above,
A photoelectric conversion element can be produced using the biopolymer composite. However, the photoelectric response had a low absolute value.

An object of the present invention is to provide a method for producing a photoelectric conversion element, which can produce a photoelectric conversion element having a large photoelectric response by using a biopolymer composite.

[0010]

A method for manufacturing a photoelectric conversion element of the present invention comprises a step of forming a photoelectric conversion active layer using a biopolymer composite having a photoelectric conversion function, and a buffer solution for the photoelectric conversion active layer. Is added to obtain a predetermined buffer concentration.

Further, in the method for producing a photoelectric conversion element of the present invention, the chromatophore is dispersed in a phosphate buffer solution to obtain a protein concentration of 4 to 400 mg / ml and a phosphoric acid concentration of 10 to 150 mM.
And a step of forming a layer of the dispersion chromatophore on the substrate and a step of drying the layer of the dispersion chromatophore.

[0012]

The present inventors have discovered that increasing the concentration of the buffer solution in which the biopolymer complex having a photoelectric conversion function is dispersed increases the photoelectric response.

If increasing the buffer solution concentration before forming the photoelectric conversion active layer affects the manufacturing process, once the photoelectric conversion active layer is formed with a low buffer solution concentration, and then the photoelectric conversion active layer is buffered. The liquid may be added.

[0014]

EXAMPLE FIG. 1 schematically shows the structure of a photoelectric conversion element manufactured by the manufacturing method described below. Glass substrate 1
An indium tin oxide (ITO) electrode 1 is formed on 0. This ITO electrode 1 is divided into two parts 1a and 1b.

A photoelectric conversion active layer 2 having a buffer solution concentration higher than that of a conventional photoelectric conversion active layer is formed on the ITO electrode 1. After the photoelectric conversion active layer 2 is dried, gold (A
The counter electrode 3 of u) is formed.

The Au counter electrode 3 is connected to one of the ITO electrodes 1b at the end. The lead wire 4a is connected to the other ITO electrode 1a, and the lead wire 4b is connected to the Au counter electrode 3.

When light enters the photoelectric conversion element thus formed from the glass substrate 10 side, the incident light passes through the glass substrate 10 and the ITO electrode 1 and enters the photoelectric conversion active layer 2. The photoelectric response of the photoelectric conversion active layer 2 is taken out from the lead wires 4a and 4b.

When the photoelectric conversion element in the above process is put to practical use, it is preferable to hermetically seal the photoelectric conversion element by further stacking a glass substrate on the Au counter electrode and sealing the periphery. .. Other structures may be adopted as long as the optical conversion active layer is sandwiched between the transparent electrode and another electrode.

Hereinafter, the case where the photoelectric conversion active layer 2 is formed by using a chromatophore will be described as an example. A red-colored photosynthetic bacterium, Rhodopseudomonas, cultured under anaerobic conditions
Crush Viridis (ATCC 19567) with ultrasonic waves,
A chromatophore, which is a photosynthetic organ membrane fragment, is prepared by performing fractional centrifugation.

This chromatophore was suspended in a sodium phosphate buffer (3 mM, pH 7.0) and the chromatophore concentration was about 10 at an optical absorption density (OD) at a wavelength of 1015 nm.
Adjust to 0. A chromatophore solution showing this optical absorption density corresponds to a protein concentration of about 40 mg / ml. This correspondence was determined by the dye binding method (Bradford method) using bovine serum γ-globumin as a standard sample.

Separately, the ITO electrode 1 is formed on the glass substrate 10.
a and 1b are formed. A photoelectric conversion active layer is formed on the glass substrate 10 on which the ITO electrode 1 is formed, using the chromatophore suspension prepared as described above. An appropriate amount of buffer solution is added to this undried photoelectric conversion active layer.
The concentration of the buffer solution is, for example, about 10 to 1000 mM.

The photoelectric conversion active layer containing the buffer solution is dried, and the dried photoelectric conversion active layer is vacuum-deposited on the photoelectric conversion active layer to form A.
About 200Å of u is vapor-deposited to form the Au counter electrode 3. After that, the lead wires 4a and 4b are attached to the ITO electrode 1a and the Au counter electrode 3 to complete the photoelectric conversion element.

Photosynthetic bacteria include Rhodobacter sphaeroides (A) in addition to Rhodopseudomonas viridis described above.
It is also possible to use bacterial cells such as TCC17023). Further, a sample in which spheroplast, a photoreaction unit (PRU), and a photoreaction center (RC) are reconstituted in a liposome can also be used.

The formation of the photoelectric conversion active layer on the ITO substrate can be carried out by various methods such as coating, spin coating, printing and electrodeposition. The electrodeposition method is different from the coating method and the printing method. It is a method suitable for producing a thick film having a large area and uniform. For example, a uniform photoelectric conversion active layer having a thickness of several μm or more can be produced by the electrodeposition method.

When the electrodeposition method is used, the chromatophore suspension buffer is required to obtain the required electric field strength during the electrodeposition operation.
It is necessary to keep the conductivity low. For this reason, it is preferable to set it to about several mM, which is the lower limit of the buffer action.

In this case, since the concentration of the buffer solution in the obtained photoelectric conversion active layer is insufficient, the insufficient amount is supplemented by adding the buffer solution to the photoelectric conversion active layer after forming the photoelectric conversion active layer.

The photoelectric conversion active layer can be formed by an electrodeposition method, a coating method, a spin coating method, a screen printing method, a Langmuir-Bloget method (LB method), or the like.
When these methods are used, there is no restriction on conductivity when forming the photoelectric conversion active layer.

Therefore, it is also possible to prepare a chromatophore suspension having a desired buffer concentration and use this chromatophore suspension to prepare a photoelectric conversion active layer. Of course, similarly to the above-mentioned electrodeposition method, it is also possible to first form a photoelectric conversion active layer having a low buffer solution concentration and then add the buffer solution.

The buffer solution can be added not only before drying the photoelectric conversion active layer, but also after drying the photoelectric conversion active layer. As a drying method, natural drying, vacuum drying or the like can be used.

The buffer solution to be added may be used not only alone but also to which other buffer solution or components such as an electron transfer substance called a mediator and a redox agent are added.

As the counter electrode, in addition to Au, ITO, M
Other metal electrodes such as g-Ag, compound semiconductor electrodes, and organic conductive materials such as polypyrrole obtained by the electric field polymerization method can also be used.

Example 1 A Rhodopseudomonas viridis chromatophore was used as the material for the photoelectric conversion active layer, and a phosphate buffer whose pH was adjusted to 7.0 with sodium hydroxide was used as the buffer.

Glass substrate with ITO transparent electrode and Au
A glass substrate provided with a counter electrode is made to face each other with a gap of about 0.5 mm, and a chromatophore suspension is filled between the two substrates.
A film was formed by the electrodeposition method. A positive voltage of 3.5 V was applied to the ITO electrode with respect to the Au counter electrode for about 30 seconds.
By applying this voltage, a chromatophore film having a thickness of about 20 μm was deposited on the ITO electrode. At this time, the absorbance is 10
It was 1-1.5 abs at 15 nm.

10-100 on the deposited chromatophore membrane
After adding an appropriate amount of a buffer solution having a concentration of 0 mM, the membrane was naturally dried. The element area was 1 cm ² . After drying the chromatophore film, Au was vacuum-deposited on the chromatophore film by using Au as a counter electrode. Furthermore, extraction lead wires were attached to the ITO electrode and the Au counter electrode.

The thus-formed photoelectric conversion element was irradiated with near infrared light having a central wavelength of 850 nm by using a light source of a light emitting diode. At this time, the photoelectric response obtained from the photoelectric conversion element is shown in FIGS. Note that FIG. 2C shows the waveform of the irradiated near-infrared light pulse.

When a near-infrared light pulse is emitted, the photoelectric response voltage (light open voltage) when the photoelectric conversion element is opened
Rapidly rises and gradually changes to a gradually increasing value, and after about 3 seconds, the value becomes about 120 mV. When the light irradiation was stopped, the light release voltage gradually decreased.

The optical short circuit current flowing when the lead wires are short-circuited rapidly rises at the same time as the irradiation of the near infrared light pulse, reaches a value of 150 nA or more, then abruptly attenuates, and then gradually decreases. Changes to about 90nA
The value of the degree was kept. The current value was observed while the near infrared light pulse was continuous.

The concentration of the added phosphate buffer was variously changed, and the photoelectric response of the optical open circuit voltage and the optical short circuit current 3 seconds after the near infrared light pulse irradiation as shown in FIG. 2 was examined. The result is shown in FIG. The horizontal axis shows the amount of the added phosphate buffer, and the vertical axis shows the photo-release voltage (mV) and photo-short-circuit current (nA / cm ² ).

As the added phosphate buffer increases, the light release voltage rises sharply and gradually shows a saturation tendency.
The saturation value was almost reached at about 1000 nanomol / cm ² . When the added phosphate buffer solution is further increased, the photo-opening voltage starts decreasing.

However, about 2500 nanomol
/ Cm ² still shows a high value. The optical short circuit current is
As the concentration of the added phosphate buffer increases, it rises more slowly than the light open-circuit voltage, and about 1000 nanomol / cm ²
It became a saturation value at about the level. Further increase in the added phosphate buffer reduced the photoshort circuit current slightly.

Example 2 As the material for the photoelectric conversion active layer, a chromatophore from Rhodopseudomonas viridis was used as in Example 1. As the buffer solution, PIPES (piperazine-N, N'-) adjusted to pH 7.0 with sodium hydroxide (NaOH) was used.
Bis (2-ethanesulfonic acid)) was used. The photoelectric conversion active layer was formed and measured in the same manner as in Example 1. The results of measuring the amount of added buffer and the photoelectric response 3 seconds after light irradiation are shown in FIG.

The light release voltage starts to increase immediately when the amount of added PIPES increases, and the amount of added PIPES becomes 250 n.
It reached a saturation value of about 30 mV at anomol / cm ² . Even if the amount of added PIPES was further increased, the light release voltage showed almost the same value. The value of the light release voltage is smaller than that in the case of Example 1.

The optical short circuit current is about 25 when the amount of added PIPES is about 25.
0nanomol / cm hardly increased to ^2, reached 3.5nA / cm ² of near saturation value 750nanomol / cm ² and thereafter rapidly increases. Furthermore, even when the amount of added PIPES was increased to 1000 nanomol / cm ^{2, the} photo-short circuit current showed almost the same value. The photo-short circuit current is smaller than that in Example 1 and hardly occurs at low concentration.

Example 3 Rhodopseudomonas viridis chromatophore was used as the material for the photoelectric conversion active layer, and the pH was adjusted to 7.8 with sodium hydroxide (NaOH) as an addition buffer.
OPS (3- (N-morpholino) propanesulfonic acid)
Was used. Formation of the photoelectric conversion active layer and measurement of photoelectric response were performed in the same manner as in Example 1.

FIG. 5 shows the amount of added buffer and the value of photoelectric response 3 seconds after light irradiation. The optical open-circuit voltage rises rapidly as soon as the amount of added MOPS increases, and it reaches 250 nanomo
The peak value was drawn at 1 / cm ² , and then dropped sharply.
Concentration of added MOPS is about 2000 nanomol / cm
^{At 2} , the light release voltage was almost zero.

The optical short circuit current is 500 nanomol / c
It rises from m ^2, 1000nanomol / cm ²
Reached a saturation value at 2000 nanomol / cm ²
Up to almost the same value. The magnitude of the photoelectric response is smaller than that in Example 2, but larger than that obtained in the related art.

Example 4 A chromatophore obtained from Rhodopseudomonas viridis was used as a material for the photoelectric conversion active layer, and Tris was adjusted to pH 7.9 with hydrochloric acid (HCl) as an addition buffer.
(Tris (hydroxymethyl) aminomethane) was used. The formation of the photoelectric conversion active layer and the measurement of the photoelectric response are described in Example 1.
It carried out similarly to.

FIG. 6 shows the amount of added buffer and the photoelectric response 3 seconds after light irradiation. When the concentration of added Tris-HCl increases, the light open-circuit voltage rises sharply to reach 250 nanom.
A peak value of about 12 mV was shown at ol / cm ² .
After that, the optical open-circuit voltage decreases and 2500 nanomol /
It became almost 0 in cm ² .

The optical short circuit current is 250 nanomol / c.
Standing up from about m ² , 500 nanomol / cm
Becomes almost 1.5 nA / cm ² about the peak value at ^2, 1
It showed almost the same value up to 250 nanomol / cm ² , and then decreased. The magnitude of the photoelectric response was smaller than that in Example 3, but it was neither superior nor inferior to the conventional one.

In the above examples, first, the photoelectric conversion active layer was formed by the electrodeposition method, and the buffer was added to the photoelectric conversion active layer. When the electrodeposition method is used, it is not possible to increase the buffer concentration during the formation of the photoelectric conversion active layer, so it is preferable to add a buffer after the formation of the photoelectric conversion active layer, but according to other film forming methods. It is not always necessary to adopt such a two-step formation method. For example, when the photoelectric conversion active layer is formed using a coating method or the like, a solution in which a chromatophore is dispersed in a buffer solution having a predetermined concentration can be used from the beginning.

Example 5 A chromatophore obtained from Rhodopseudomonas viridis was used as the material for the photoelectric conversion active layer, and sodium phosphate (pH 7.0) was used as the buffer. The concentration of the chromatophore solution is the optical absorption density (O
D) was adjusted to 100 (cell length 1 cm).

The chromatophore concentration corresponds to about 40 mg / ml when converted into protein concentration. In addition,
This calibration was performed using a dye binding method (Bradford method) with bovine serum γ-globumin as a standard.

About 20 μl of the chromatophore suspension thus prepared was used to form a photoelectric conversion active layer on the ITO electrode on the glass substrate by a coating method. The film thickness was about 8 μm.

The sodium phosphate concentration of the buffer solution is 5 to 80 m.
FIG. 7 shows the change in photoelectric response with respect to the buffer solution concentration when changed to M. The light open-circuit voltage suddenly showed a large value when the concentration of the phosphate buffer solution increased to a certain degree, and thereafter showed a substantially constant value regardless of the buffer solution concentration. The photoshort-circuit current rises relatively slowly until the concentration of the phosphate buffer is about 10 mM, and then rises more rapidly to 20 mM.
It seems that the rate of increase is weakened again and it continues to increase to 80 mM.

When the photoelectric conversion active layer was naturally dried, when the phosphate buffer solution concentration was 80 mM or more, the buffer agent was deposited on the photoelectric conversion active layer, and the film was broken. Therefore, although data above a concentration of 80 mM were not obtained, by suppressing the precipitation, a photoelectric response would be obtained even at a higher concentration.

Although a protein concentration of about 40 mg / ml was used, it is believed that it can be used within a range of about 4-400 mg / ml. Also, the concentration of the phosphate buffer can be used up to about 150 mM by devising the drying method and the like.

However, when the concentration of the phosphate buffer solution is 10 mM or less, the value of the photo-short-circuit current is low, so that it is preferably 10 to 150 mM. More preferably, the protein concentration is 20-
It is preferable that the concentration is 150 mg / ml and the phosphate buffer concentration is 20 to 80 mM.

For comparison, in the conventional method for manufacturing a photoelectric conversion active layer, Tr is used as a buffer solution.
The buffer concentration was about 10 mM or less using is-HCl.

From the photoelectric response of FIGS. 2 to 7, it can be seen that it is particularly preferable to use phosphate as the buffer solution. Then PIPES is preferred. In the above example, p
Although H was adjusted with NaOH and HCl, the material for adjusting the pH is not limited to these. Further, as shown in the above-mentioned example, the current characteristics and voltage characteristics of the device obtained by using the same photoelectric conversion substance are the kind of buffer solution to be added, pH,
Depends on the added concentration. Optimal characteristics can be obtained by optimally selecting these parameters.

According to the above-mentioned example, a large photoelectric response of about 20 times at the open circuit voltage and about 100 times at the optical short circuit current is obtained as compared with the photoelectric response of the photoelectric conversion active layer by the conventional manufacturing method, especially the electrodeposition method. You can also

Use phosphate or PIPES as buffer
If it is present, the addition amount is 250 to 2500 nanomol /
cm²It is preferable that Also, as a buffer solution, MO
When using PS or Tris, the buffer should be 50-2.
500 nanomol / cm ²It is preferable that

As described above, according to the method for manufacturing the photoelectric conversion element of the embodiment of the present invention, it is possible to obtain an excellent photoelectric response far exceeding the photoelectric response obtained in the related art.

[0063]

As described above, according to the present invention,
The biopolymer composite having a photoelectric conversion function can be used to manufacture a photoelectric conversion element exhibiting a large photoelectric response.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing the structure of a photoelectric conversion element to be manufactured according to an embodiment of the present invention.

FIG. 2 is a graph showing the photoelectric response of the photoelectric conversion element manufactured according to Example 1.

FIG. 3 is a graph showing the photoelectric response of the photoelectric conversion device manufactured in Example 1 as a function of the amount of phosphate buffer added.

FIG. 4 is a graph showing the photoelectric response of the photoelectric conversion device manufactured in Example 2 as a function of the amount of PIPES added.

FIG. 5 is a graph showing the photoelectric response of a photoelectric conversion element manufactured according to Example 3 as a function of the amount of MOPS added.

FIG. 6 is a graph showing the photoelectric response of a photoelectric conversion element manufactured according to Example 4 as a function of the amount of Tris-HCl added.

FIG. 7 is a graph showing the photoelectric response of a photoelectric conversion element manufactured according to Example 5 as a function of phosphate buffer solution concentration.

[Explanation of symbols]

 1 ITO electrode 2 Photoelectric conversion active layer 3 Au counter electrode 4 Extraction lead wire 10 Glass substrate

Claims (7)

[Claims] 1. A step of forming a photoelectric conversion active layer using a biopolymer composite having a photoelectric conversion function, and a step of adding a buffer solution to the photoelectric conversion active layer to obtain a predetermined buffer agent concentration. Method for manufacturing photoelectric conversion element. 2. The buffer solution has a buffer capacity region of pH 4 to 10, and the predetermined buffer agent concentration is 50 to 5000 nan.
The method for producing a photoelectric conversion element according to claim 1, wherein the photoelectric conversion element has an omol / cm ² . 3. The step of forming the photoelectric conversion active layer,
The method for manufacturing a photoelectric conversion element according to claim 1, which comprises film formation by electrodeposition or coating. 4. The buffer is phosphate or piperazine.
N, N′-bis (2-ethanesulfonic acid), and the predetermined buffer concentration is 250 to 2500 nanomol /
The method for producing a photoelectric conversion element according to claim 1, wherein the photoelectric conversion element has a size of cm ² . 5. The buffering agent is 3- (N-morpholino) propanesulfonic acid or tris (hydroxymethyl) aminomethane, and the predetermined buffering agent concentration is 50 to 250.
It is 0 nanomol / cm < ² >, The manufacturing method of the photoelectric conversion element in any one of Claims 1-3. 6. The chromatophore is dispersed in a phosphate buffer solution to give a protein concentration of 4 to 400 mg / ml and a phosphoric acid concentration of 10 to 10.
A method for producing a photoelectric conversion element, comprising: a step of forming a dispersion chromatophore layer on a substrate at 150 mM; and a step of drying the dispersion chromatophore layer. 7. The protein concentration is 20 to 150 mg / m 2.
7. The method for producing a photoelectric conversion element according to claim 6, wherein the concentration of phosphate is 20 to 80 mM.