JPH056355B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a photoelectric conversion element, and particularly to a photoelectric conversion element that can discriminate the wavelength of incident light.

(B) Prior art and its problems Photoelectric conversion elements that use space charge layers, such as PN junctions or metal-semiconductor junctions, respond to incident light with a constant applied voltage.
A photocurrent or photovoltaic force can be obtained. Also, if the applied voltage is zero at this time, it is a battery. In this way, the photocurrent or photovoltaic force obtained using a PN junction or metal-semiconductor junction is positive, zero, or negative zero depending on the circuit, and it depends on the amount of incident light and the quantum yield of the photoelectric conversion element. Absolute value changes.
However, in this case, there is only one process in which the photocurrent or photovoltaic force rises from the dark value upon light irradiation, regardless of the incident light wavelength, and returns to the dark value once the light irradiation is turned off. . Thionin
In Fe ²⁺ -based photovoltaic cells, a complex photocurrent has been observed from the combination of anode photocurrent and cathode photocurrent, but changes in the photocurrent waveform depending on the wavelength of incident light have not been reported.

The photoelectric conversion element described above cannot distinguish incident light by itself. In order to perform identification, a filter must be inserted into the incident optical path, and for example, when this type of incident light is received, the optical path must be separated into two.

(C) Object of the Invention It is an object of the invention to provide a photoelectric conversion element that can identify the wavelength of incident light without inserting a filter into the incident optical path.

(A) Structure of the Invention The object of the present invention is to provide a phthalocyanine pigment that has a photovoltaic force in response to visible light or infrared light, and that provides a positive or negative photocurrent signal upon irradiation depending on the wavelength of incident light. , thio-indigo pigments, indigo pigments, perylene pigments, azo pigments, cyanine pigments, polycyclic quinone pigments, pyrylium dyes, thiopyrylium dyes, triarylmethane dyes, thiodine dyes, and cyanine dyes. Using a photoelectric conversion element having a film with a thickness of 0.1 to 10 μm containing one photoconductive organic compound and a binder, and two electrodes in contact with both sides of the film, at least one of which is transparent. This is accomplished by a method of identifying the wavelength of the irradiated light by irradiating the element with light from one transparent electrode of the element and obtaining a positive or negative photocurrent signal.

As a method for forming the film, a method of dissolving or dispersing it in a binder and coating it, a method of forming it into pellets by applying pressure, etc. are selected as appropriate. The binder may be one that forms a film as a binder, such as polycarbonate, polystyrene, polyester, polyarylate, polyvinyl alcohol, melanin resin, or phenolic resin.

At least one of the electrodes in contact with both surfaces of the film must be a conductive transparent electrode because of the need for light irradiation. As the transparent electrode, a Nesa film, ITO, or a metal film such as Pt, Au, Ag, Cu, Al, In, etc. is used.

The substrate does not need to be transparent or opaque as long as it is an insulating material, and may be of any material ranging from a hard material such as glass to a highly flexible material such as polyethylene terephthalate.

The effects of the present invention are considered to be based on the following principle. When such a photoresponsive film is irradiated with light, electrons and holes are generated in the film, but if the light is absorbed unevenly in the film, a concentration gradient of electrons and holes is created and this When there is a difference in diffusion rate between holes and electrons, a photoelectromotive force is generated separately from the photoelectromotive force caused by the space charge layer. However, depending on the fermi level of the electrode, it may make non-ohmic contact with the membrane, but in this case the behavior becomes more complex.

Due to the above-mentioned effects, when a photovoltaic force or photocurrent signal is obtained, the waveform changes slightly depending on the distribution of electron and hole generation in the film and the capacity of the electric field. As a result, the region where electron-hole pairs are generated follows the extinction coefficient of the photoconductive organic material, and the same photoelectric conversion element can obtain a positive or negative signal for the wavelength of incident light, so wavelength can be identified. becomes possible.

The film thickness is preferably 10 μm or less in order to avoid increasing the internal resistance of the film, and to avoid problems with light absorption.
A thickness of 0.1 μm or more is desirable.

(B) Example The present invention will be explained in detail below based on the drawings.

Example 1 FIG. 1 shows a cross-sectional view of an element as an example of the present invention. It consists of three layers: a substrate 1, a first electrode 2, a film 3, and a second electrode 4. Further, a protective layer 6 may be provided to physically or chemically protect these three layers.

A vapor-deposited film of indium was used for the first electrode 2 and gold was used for the second electrode 4, and light was irradiated from this direction using gold as a transparent electrode.

Since contact is made with different metals, the gold electrode side becomes a cathode, allowing it to behave as a type of battery. The membrane was prepared by dissolving a copolymer of butyl acrylate and methacrylic acid as a binder in a highly polar solvent such as dioxane, mechanically dispersing copper phthalocyanine (manufactured by Toyo Ink), and coating the mixture on an indium electrode. The coated film was sufficiently dried at around 90°C in a dryer. The ratio of copper phthalocyanine to binder was 16% by weight, and the thickness of the coating film was about 3 μm.

Figure 2 shows the measurement circuit. Figure 2-1 shows a simple measurement system, in which the ammeter 7 was a Keithley Pyu Animator Model 610C, and the recorder 8 tracked the photocurrent waveform.

Figure 2-2 shows a system with faster response speed, 9
is a resistor, the preamplifier 10 is LI-75A manufactured by NF Circuit Design Block, and the waveforms are stored in a transient memory S-121 (11) manufactured by Autonics and recorded by a recorder 12. 13 is a sample box made of Al, and 14 is a sample.

A tungsten halogen lamp was used as the light source, and monochromatic light was extracted with a diffraction grating and passed through a high-frequency cut-of-filter as incident light hν. A camera shutter was attached to the light outlet of the monochromator, and this shutter was used to irradiate light. The incident hν is 1.8×10 ³ to 2.0× at 520 to 550 nm.
It was 10 ³ erg/cm ³ sec.

All measurements were performed at room temperature.

FIG. 3 shows photocurrent waveforms when the wavelength of incident light is changed. A, b, c, and d in FIG. 3 are the photocurrent waveforms at 530, 540, 550, and 580 nm, respectively, measured using the measurement system shown in FIG. 2-1. The photocurrent changes dynamically depending on the wavelength of the incident light, and in the wavelength range of 550 to 730 nm, when light is incident, signals with the opposite sign (negative) to the dark current are observed as shown in c and d in Figure 3. It was done. Since this signal is not observed in other incident light wavelength ranges such as a and b in FIG. 3, these two wavelength ranges can be distinguished.

The former wavelength range corresponds to the region where the extinction coefficient of copper phthalocyanine is large. In the measurement system shown in Figure 2-2, the time of this opposite sign (negative) signal is 10 to 100 msec.
The magnitude is about 630 nm, which is more than 10 times the steady value of the photocurrent.

This signal slowly decays in air as it reaches its steady state, but it recovers to its original value after being left in a vacuum of about 10 ^-5 torr for about 2 hours. Furthermore, the dark current value can be freely set depending on the applied voltage.
By taking advantage of such characteristics during light irradiation, it becomes possible to distinguish two types of incident light wavelengths.

Example 2 Styron 685 which is polystyrene (manufactured by Asahi Dow)
2-1 shows the photocurrent waveform of a sample having the same configuration as in Example 1 except for using the binder as the binder.
Tracking was performed using the measurement system shown in the figure. The film thickness of this sample was 3.5 nm. The results are the same as in Example 1.
An opposite sign (negative) signal was observed in the wavelength region of 550-730 nm.

(F) Effect of the Invention In this way, according to the present invention, one light-receiving element can distinguish incident light in two or more different wavelength regions without using a filter, so when used in an image reading sensor, for example, the sensor It has the advantage of simplifying the structure. Further, since the wavelength range that can be identified corresponds to the absorption spectrum of the electron-hole generator forming the film, it can be arbitrarily set depending on the material.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing one example of the photoelectric conversion element of the present invention, and Fig. 2 is a measurement circuit diagram.
Figure-2 shows the high-speed type. FIG. 3 a, b, c and d are graphs showing photocurrent waveforms at 530, 540, 550 and 580 nm, respectively. In the figure, 1... substrate, 2... first electrode, 3...
Membrane, 4... Second electrode, 5... Lead wire, 6... Protective film, 7... Ammeter, 8... Recorder, 9... Resistor, 10... Preamplifier, 11... Transient memory, 12 . . . recorder, 13 . . . sample box, 14 . . . sample.

Claims (1)

[Claims] 1. Phthalocyanine pigments, thio-indigo pigments, and indigo pigments that have photovoltaic force against visible light or infrared light, and can provide a positive or negative photocurrent signal when irradiated with light depending on the wavelength of incident light. Perylene pigments, azo pigments, cyanine pigments,
A film having a thickness of 0.1 to 10 μm containing a binder and at least one photoconductive organic compound selected from polycyclic quinone pigments, pyrylium dyes, thiopyrylium dyes, triarylmethane dyes, thiodine dyes, and cyanine dyes, and A photoelectric conversion element having two electrodes in contact with both sides of the film, at least one of which is transparent, is used, and light is irradiated from one transparent electrode of the element to the element to generate positive or negative signals. By obtaining the photocurrent signal of
A method of identifying the wavelength of the illumination light.