JP2005294666A - Photoelectric conversion device, and radiation picture detector using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an efficient photoelectric conversion device by solving the problem of electronic transportation after the separation of photoexcited charge which deteriorates photoelectric conversion efficiency in the photoelectric conversion device which does not use an electrolyte, and to provide a radiation picture detector by which a digital radiation picture of a high picture quality is obtained in the medical radiation picture detector using the photoelectric conversion device. <P>SOLUTION: In the photoelectric conversion device having a transparent electrode, a photoelectric conversion layer which absorbs light having passed through the transparent electrode and separates electric charges and a counter electrode provided on a side opposite to the transparent electrode across the photoelectric conversion layer, the photoelectric conversion layer has an electron acceptor layer and an electron donor layer separate from the transparent electrode and the counter electrode, and the electron acceptor layer has a monomolecular film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photoelectric conversion element and a radiation image detector using the photoelectric conversion element.

  Gretzel et al. Have reported a photoelectric conversion element (Gretzel cell) having a performance close to that of an amorphous silicon photoelectric conversion element by forming a film of an organic dye having a photoelectric conversion function on a transparent electrode such as titanium oxide. Patent Document 1). In recent years, a Gretzel cell using a monomolecular film having fullerene has also been reported using a nanotechnology technique (Patent Documents 1 and 2). Since these Gretzel cells are wet solar cells that are electrically connected to the counter electrode by a liquid redox electrolyte, the photoelectric conversion function is significantly reduced due to depletion of the electrolyte when used over a long period of time, and function as a photoelectric conversion element. There is concern that it will disappear. In addition, as a photoelectric conversion element using an organic dye that does not use an electrolytic solution, a photoelectric conversion element in which a layer in which an electron donor and an electron acceptor are mixed is formed between a transparent electrode and a counter electrode, or between a transparent electrode and a counter electrode. A photoelectric conversion element having an electron donor layer and an electron acceptor layer sandwiched between them has been proposed (Patent Document 3).

  The operational principle of these photoelectric conversion elements is that holes and electrons are generated by the movement of electrons from the electron donor (or electron donor layer) to the electron acceptor (or electron acceptor layer) by photoexcitation. Due to the potential difference, holes are transported between electron donors (or electron donor layer) to one electrode, electrons are transported between electron acceptors (or electron acceptor layer) to the other electrode, and photocurrent Is observed. However, there is almost no highly conductive electron transport material having a photoelectric conversion function, and the fact that the electron transport speed is lower than the hole transport speed is a cause of lowering the photoelectric conversion efficiency.

  Next, an X-ray image detector to which the photoelectric conversion element is applied will be described. Amorphous silicon photoelectric conversion elements are applied in the medical field as flat panel radiation detectors (FPDs) in addition to application as photosensitive drums for solar cells and copying machines. Also, photoelectric conversion elements using organic dyes have been proposed for application to FPD (Patent Document 4).

  FPD is a kind of digital X-ray image detector, and is a system that reads out a radiographic image as a digital signal and can make a diagnosis on a monitor such as a personal computer without using a radiographic film (such as an X-ray film). In FPD, a photoelectric conversion element absorbs X-rays directly and performs photoelectric conversion (direct FPD), and a fluorescent substance converts X-rays into fluorescence, and the photoelectric conversion element absorbs the fluorescence and performs photoelectric conversion. (Indirect type FPD), and the amorphous silicon photoelectric conversion element and the organic dye photoelectric conversion element are used for the latter indirect FPD.

The advantage of the indirect FPD using the amorphous silicon photoelectric conversion element is that a high-quality image comparable to the conventional analog system can be obtained. The amorphous silicon photoelectric conversion element is an inorganic semiconductor material such as amorphous silicon. Is required to be finely processed on a thin film transistor (TFT), which requires very advanced technology and equipment, resulting in a very high product price. On the other hand, photoelectric conversion elements using organic dyes have the advantage that they are very easy to process due to the use of organic matter and the product price is very low, but in order to obtain high-quality images comparable to analog systems. In terms of photoelectric conversion efficiency, it is insufficient.
JP 2000-261016 A JP 2002-94146 A JP-T-2002-502129 JP 2003-50280 A Journal of the American Chemical Society 115 (1993) 6382

  Therefore, an object of the present invention is to solve the problem of electron transport after photoexcited charge separation that lowers the photoelectric conversion efficiency in a photoelectric conversion element that does not use an electrolytic solution, and to provide a highly efficient photoelectric conversion element. . Another object of the present invention is to provide a radiation image detector that can obtain a high-quality digital radiation image in a medical radiation image detector using the photoelectric conversion element.

  Means for solving the above problems are as follows.

  (1) A photoelectric conversion element having a transparent electrode, a photoelectric conversion layer that absorbs light transmitted through the transparent electrode and performs charge separation, and a counter electrode provided on the opposite side of the transparent electrode with the photoelectric conversion layer interposed therebetween The photoelectric conversion layer has an electron acceptor layer and an electron donor layer that are separate from the transparent electrode and the counter electrode, and the electron acceptor layer has a monomolecular film. .

  (2) The photoelectric conversion element according to (1), wherein the electron acceptor layer contains a π-conjugated compound.

  (3) The photoelectric conversion element according to (1), wherein the electron donor layer contains a conductive polymer compound.

  (4) The conductive polymer compound includes polyphenylene vinylene and derivatives thereof, polythiophene and derivatives thereof, poly (thiophene vinylene) and derivatives thereof, polyacetylene and derivatives thereof, polypyrrole and derivatives thereof, polyfluorene and derivatives thereof, poly (p The photoelectric conversion element according to (3), which contains at least one of -phenylene) and derivatives thereof, or polyaniline and derivatives thereof.

  (5) The π-conjugated compound contains at least one of fullerene and a derivative thereof, carbon nanotube and a derivative thereof, porphyrin and a derivative thereof, phthalocyanine and a derivative thereof, according to (2) Photoelectric conversion element.

  (6) The conductive polymer compound contains at least one of polythiophene and derivatives thereof, and the π-conjugated compound contains at least one of fullerenes and derivatives thereof, The photoelectric conversion element according to (3) or (4).

  (7) a first layer that emits light according to the intensity of incident radiation, a second layer that converts light energy output from the first layer into electrical energy, and electrical energy obtained in the second layer in the previous period And a third layer for outputting a signal based on the accumulated electric energy and a fourth layer for holding the first to third layers, wherein the second layer comprises a transparent electrode and an electron. A radiation image detector comprising a donor layer and an electron acceptor layer having a monomolecular film between them.

  (8) The radiation image detector according to (7), wherein the electron acceptor layer contains a π-conjugated compound.

  (9) The radiation image detector according to (7), wherein the electron donor layer contains a conductive polymer compound.

  (10) The conductive polymer compound includes polyphenylene vinylene and derivatives thereof, polythiophene and derivatives thereof, poly (thiophene vinylene) and derivatives thereof, polyacetylene and derivatives thereof, polypyrrole and derivatives thereof, polyfluorene and derivatives thereof, poly (p The radiation image detector according to (9), which contains at least one of -phenylene) and derivatives thereof, or polyaniline and derivatives thereof.

  (11) The π-conjugated compound contains at least one of fullerene and a derivative thereof, carbon nanotube and a derivative thereof, porphyrin and a derivative thereof, phthalocyanine and a derivative thereof, according to (8) Radiation image detector.

  (12) The conductive polymer compound includes at least one of polythiophene and a derivative thereof, and the π-conjugated compound includes at least one of fullerene and a derivative thereof ( The radiation image detector according to 9) or (10).

  In a photoelectric conversion element having a transparent electrode, a photoelectric conversion layer that absorbs light transmitted through the transparent electrode and performs charge separation, and a counter electrode provided on the opposite side of the transparent electrode with the photoelectric conversion layer interposed therebetween, Since the conversion layer has an electron acceptor layer and an electron donor layer that are separate from the transparent electrode and the counter electrode, and the electron acceptor layer has a monomolecular film, it can efficiently transport electrons. The photoelectric current value and the photoelectric conversion efficiency are improved, and a highly efficient photoelectric conversion element can be provided.

  Also, a first layer that emits light according to the intensity of incident radiation, a second layer that converts light energy output from the first layer into electrical energy, and storage of electrical energy obtained in the second layer in the previous period. And a radiation image detector having a third layer for outputting a signal based on the stored electrical energy, and a fourth layer for retaining the third layer from the first layer, wherein the second layer comprises a transparent electrode and an electron donor. By having an electron acceptor layer having a monomolecular film between the layers, the radiation sensitivity can be improved, and the radiation image detector that can obtain a high-quality digital radiation image can be provided.

  Next, the best mode for carrying out the present invention will be described, but the present invention is not limited thereto.

  FIG. 1 shows a cross-sectional view of the photoelectric conversion element of this embodiment. The photoelectric conversion element of FIG. 1 has a configuration in which an electrolytic solution in which a photoelectric conversion layer is sandwiched between a transparent electrode and a counter electrode is not used (a transparent electrode may be used as the counter electrode). The photoelectric conversion layer has an electron donor layer and an electron acceptor layer. Here, the electron donor layer is “a layer containing an electron donor”, and the electron acceptor layer is “a layer containing an electron acceptor”. In addition, the electron donor and the electron acceptor are “an electron donor that, when absorbing light, moves from the electron donor to the electron acceptor to form a hole-electron pair (charge separation state) and It is an “electron acceptor” and does not simply donate or accept electrons as in the case of an electrode, but donates or accepts electrons by the photoreaction described above.

  In FIG. 1, light incident from a transparent electrode or a counter electrode is absorbed by an electron donor layer or an electron acceptor layer, electrons move from the electron donor to the electron acceptor, and a hole-electron pair (charge) A separated state). Due to the potential difference between the transparent electrode and the counter electrode, the generated charge is transported to the electrode through which the electrons pass through the electron acceptor layer and through the electron donor layer, and the photocurrent is detected. .

  The feature of the present invention is to reduce the distance of electron transport in the electron acceptor layer, which is a cause of deteriorating device performance, by having a monomolecular film in the electron acceptor layer. In other words, by using a monomolecular film for the electron acceptor layer, electrons generated by charge separation due to light absorption are remarkably reduced in the electron transport distance in the electron acceptor layer, and passed to the electrode in direct contact. It is.

The transparent electrode refers to an electrode that transmits light to be photoelectrically converted, and is preferably an electrode that transmits light of 300 to 800 nm. For example, it is preferable to use a transparent conductive metal oxide such as indium titanium oxide (ITO), SnO ₂ , or ZnO, a metal thin film such as gold, silver, or platinum, or a conductive polymer. Absent.

  The transparent electrode may be formed on a glass substrate or a resin substrate, but the substrate is not essential, and may be formed on another layer such as a phosphor layer. Further, the substrate may not be used if it is a strong thin film.

  The material for the counter electrode is preferably a metal (eg, gold, silver, copper, platinum, rhodium, ruthenium, aluminum, magnesium, indium, etc.), carbon, or the transparent electrode material, but is not limited thereto. The counter electrode may be formed on a glass substrate, a resin substrate, or a metal substrate, but the substrate is not essential, and may be formed on another layer such as a phosphor layer, or a strong thin film. If necessary, the substrate may not be used.

  The potential difference between the transparent electrode and the counter electrode for detecting the photocurrent may be generated by applying a voltage from the outside, for example, or by using materials having different ionization potentials between the transparent electrode material and the counter electrode material. It may be generated.

  The monomolecular film of the electron acceptor layer may be formed on a transparent electrode or a counter electrode. Monomolecular film formation methods include the Langmuir-Blodget (LB) method, methods using chemical bonding and chemical adsorption, vapor deposition methods, and coating methods (including cast methods and spin coating methods). Not exclusively. In the examples described later, a method using chemical bonding or chemical adsorption was used.

  As an example, an electron acceptor molecule monolayer formed on an electrode is shown in FIG. Here, the electron acceptor is preferably a π-conjugated compound. The π-conjugated compound means a compound having 7 or more aromatic π electrons. Therefore, for example, the pyromellitic imide derivative (compound 1-5) shown below is not a π-conjugated compound because it has only six aromatic π electrons, but the naphthimide derivative (compound 1-6) Since it has 10 group π electrons, it is a π-conjugated compound.

  Among the π-conjugated compounds, electrons having the basic skeletons of fullerene (compound 2-1), carbon nanotube (compound 2-2), porphyrin (compound 2-3), and phthalocyanine (compound 2-4) shown below. A receptor is preferred.

  Next, preferred specific examples of fullerene and derivatives thereof, carbon nanotubes and derivatives thereof are shown in compounds 3-1 to 3-6 and compound 4-1. In compound 4-1, n is an integer of 1 or more. Preferred specific examples of porphyrin and derivatives thereof are shown as compound 5-1 and compound 5-2. In Compound 5-1 and Compound 5-2, n is an integer of 0 or more, and m is an integer of 1 or more. Preferred specific examples of phthalocyanine and derivatives thereof are shown in Compound 6-1 and Compound 6-2. In Compound 6-1 and Compound 6-2, n is an integer of 0 or more. The π-conjugated compounds are not limited to the specific examples shown here.

  Further, as shown in FIG. 2, the electron acceptor preferably has a structure in which a basic skeleton and a functional group are connected by a spacer. In this case, the spacer is preferably a substituted or unsubstituted group containing an alkyl group, a phenyl group, an amide group, an ester group, an acetylene group or an oligothiophene, particularly preferably an alkyl group. It is not limited, and a spacer need not be used.

  As a method for producing the monomolecular film, the above-described method using chemical bonding or chemical adsorption is preferable. Specifically, for example, when a monomolecular film is formed on an electrode, an electron acceptor molecule introduced with a “functional group capable of chemical bonding or chemical adsorption with an electrode” is dissolved or dispersed in an organic solvent. What is necessary is just to immerse an electrode in a solution. In order to bind or adsorb efficiently, heat treatment or reflux treatment may be performed. Thereafter, the electrode is taken out from the solution and washed to form a monomolecular film of electron acceptor molecules on the electrode. In the same way, a monomolecular film of a molecule having a “functional group capable of chemically bonding or chemisorbing with an electrode” is first formed, and then the resulting monomolecular film and an electron acceptor molecule are chemically bonded ( A monomolecular film of electron acceptor molecules may be formed by, for example, ester condensation or amide condensation. As the “functional group capable of chemical bonding or chemical adsorption with the electrode”, for example, when an ITO electrode is used, those having a carboxyl group, a silicon hydroxide group, a sulfonic acid group, a phosphoric acid group or a hydroxyl group are preferable. Not limited to this. When a gold metal thin film is used as the electrode, a thiol group or a cationic group is preferable, and alkylthiol or alkylamine is particularly preferable, but is not limited thereto.

The electron donor layer is preferably formed containing a conductive material in order to transport charges generated by light absorption. For example, as a conductive material, a p-type inorganic semiconductor (GaP, NiO, CoO, FeO, Bi ₂ O ₃ , MoO ₂ , Cr ₂ O ₃ , a compound containing monovalent copper, etc.) or a conductive polymer compound is used. preferable. Conductive polymer compounds having the basic skeletons of polyphenylene vinylene, polythiophene, poly (thiophene vinylene), polyacetylene, polypyrrole, poly (p-phenylene), and polyaniline shown in compounds 7-1 to 7-8 below (In the compounds 7-1 to 7-8, x is preferably an integer of 1 or more). Preferred specific examples of polyphenylene vinylene and derivatives thereof are shown in compounds 8-1 to 8-4 (in compounds 8-1 to 8-4, n, m, k, j are integers of 0 or more, and x is an integer of 2 or more. .) Preferred specific examples of polythiophene and derivatives thereof are shown in compounds 9-1 to 9-11 (in compounds 9-1 to 9-11, n and m are integers of 0 or more, k is an integer of 1 or more, and x is 2 or more. Is an integer.) Preferred specific examples of poly (thiophene vinylene) and derivatives thereof are shown as compounds 10-1 to 10-3 (in compounds 10-1 to 10-3, n, m, k, j are integers of 0 or more, x is 2) It is an integer above.) Preferred specific examples of polyacetylene and derivatives thereof are shown in compounds 11-1 to 11-5 (in compounds 11-1 to 11-5, n and m are integers of 0 or more, and x is an integer of 2 or more). Preferred specific examples of polypyrrole and derivatives thereof are shown in compounds 12-1 to 12-7 (in compounds 12-1 to 12-7, n is an integer of 0 or more, k is an integer of 1 or more, and x is an integer of 1 or more. .) Preferred specific examples of polyfluorene and derivatives thereof are shown in compounds 13-1 to 13-8 (in compounds 13-1 to 13-8, n and m are integers of 0 or more, and x is an integer of 1 or more.) . Preferred specific examples of poly (p-phenylene) and derivatives thereof are shown in compounds 14-1 to 14-3 (in compounds 14-1 to 14-3, n and m are integers of 0 or more, x and y are 1 or more) Is an integer.) Preferred specific examples of polyaniline and derivatives thereof are shown in compounds 15-1 to 15-4 (in compounds 15-1 to 15-4, n is an integer of 0 or more, and x is an integer of 2 or more). The conductive polymer compound is not limited to these specific examples.

  Examples of the method for forming the electron donating layer on the electron acceptor layer include a vapor deposition method, a coating method (including a casting method and a spin coating method), a method using chemical bonding and chemical adsorption, and an electrolytic polymerization method. The film thickness is preferably 50 nm or more (particularly 100 nm or more) from the viewpoint of increasing the amount of light absorption, and is preferably 1 μm or less (particularly 300 nm or less) from the viewpoint that the electrical resistance does not become too large.

  The photoelectric conversion element is not limited to one composed of only two electrodes including a transparent electrode and a photoelectric conversion layer including an electron acceptor layer and an electron donor layer. Another layer such as a conductive layer, an insulating layer, or an undercoat layer may be provided between the body layer and the electron donor layer.

  Next, an embodiment of a system using a radiation image detector to which the above-described photoelectric conversion element is applied will be described in detail. However, the present invention is not limited to the description of this embodiment or the one shown in the drawings.

  FIG. 3 shows a system using the radiation image detector of the present embodiment. In FIG. 3, the radiation emitted from the radiation generator 10 is irradiated to the radiation image detector 20 through a subject (for example, a patient in a medical facility) 15. The radiation image detector 20 generates an image signal DFE based on the intensity of the irradiated radiation. The generated image signal DFE is read by the image processing unit 51 connected to the radiation image detector 20. Alternatively, after being stored in a portable recording medium such as a semiconductor memory card attached to the radiation image detector 20, the recording medium is removed from the radiation image detector 20 and attached to the image processing unit 51. , And supplied to the image processing unit 51.

  The image processing unit 51 performs image processing such as shading correction, gain correction, gradation correction, edge enhancement processing, and dynamic range compression processing on the image signal DFE generated by the radiation image detector 20 to perform diagnosis or the like. The image signal suitable for is output. An image display unit 52 is connected to the image processing unit 51, and the image display unit 52 displays an image based on the image processed image signal output from the image processing unit 51.

  Further, the image processing unit 51 can perform enlargement and reduction of an image, and can also perform compression and expansion processing of an image signal in order to facilitate storage and transfer of the image signal. For this reason, by confirming that the image displayed on the image display unit 52 is enlarged or reduced, it is possible to easily confirm the imaging region and to perform the processing state. It is also possible to automatically specify the displayed image and the area of the displayed image and automatically perform appropriate image processing on the specified image and the specified area.

  Further, an operation input unit 53 having a keyboard, mouse, pointer, etc. is connected to the image processing unit 51, and patient information and the like can be input by this operation input unit 53 and additional information can be added to the image signal. . The operation input unit 53 also gives instructions for specifying image processing, storing and reading image signals, and transmitting and receiving image signals via a network.

  An image output unit 54, an image storage unit 55, and a computer-aided image automatic diagnosis unit (CAD) 56 are further connected to the image processing unit 51.

  The image output unit 54 records and outputs a radiation image on a recording sheet, a film, or the like. For example, an imager may be used that exposes a silver salt photographic film based on an image signal and records and outputs a radiation image as a silver image by developing the exposed silver salt photographic film. Further, it may be an ink jet printer that prints ink on recording paper or film by an ink jet method based on an image signal, or a thermal that transfers an image to recording paper or film by melting or sublimating ink based on an image signal. It may be a printer, or it scans the photoconductor with a laser beam based on the image signal, transfers the toner adhering to the photoconductor to the paper, and then fixes it with heat and pressure so that the image is printed on the recording paper. It may be an electrophotographic printer to be formed.

  In the image storage unit 55, the image signal of the radiation image is stored in an information recording medium such as a hard disk so that it can be read out as needed.

  The CAD 56 provides information useful for diagnosis to a doctor so that the diagnosis is supported so that there is no oversight of the lesion, and the computerized image processing and computer analysis of the captured radiographic image is performed to obtain information useful for the diagnosis. Append to signal.

  The image processing unit 51 transmits the radiographic image signal to the hospital via the network 60 such as a so-called LAN, the Internet, and a PACS (medical image network) as well as the image output unit 54, the image storage unit 55, and the CAD 56 described above. It can also be sent to other departments or remote locations within the facility. The image processing unit 51 can also receive an image signal obtained from the CT 61 or the MRI 62, an image signal obtained from the CR or another FPD 63, and other inspection information via this network, and a radiation image detector. For comparison with the radiographic image obtained at 20, the image signal, inspection information, etc. sent via the network 60 can be displayed on the image display unit 52 or output from the image output unit 54. Further, the image processing unit 51 can store the transmitted image signal, inspection information, and the like in the image storage unit 55. In addition, the image processing unit 51 stores an image signal or the like of the radiographic image obtained by the radiographic image detector 20 in the external image storage device 64, or displays the radiographic image detector 20 on the screen of the external image display device 65. The obtained radiation image can also be displayed.

  Next, an example of the structure of the radiation image detector 20 is shown in FIG. The radiation image detector 20 includes an imaging panel 21, a scanning drive circuit 25, a signal selection circuit 27, a control circuit 30, a memory unit 31, an operation unit 32, a display unit 33, a power supply unit 34, a connector 35, and a housing 40. ing. The imaging panel 21 generates accumulated electrical energy according to the intensity of the irradiated radiation. The generated electrical energy is read by the scanning drive circuit 25 and output as an image signal by the signal selection circuit 27. Is done. The output image signal is stored in the memory unit 31 using a rewritable read-only memory (for example, a flash memory) or the like. The operation of the radiation image detector 20 is controlled by the control circuit 30, and the operation is switched by the operation unit 32.

  The display unit 33 indicates that a predetermined amount of an image signal has been written to the memory unit 31 when the image shooting preparation is completed, and the power supply unit 34 drives the imaging panel 21 to obtain an image signal. The connector 35 is for supplying power necessary for the communication, and the connector 35 is used for communication between the radiation image detector 20 and the image processing unit 51. The inside of the housing 40, the scanning drive circuit 25, the signal selection circuit 27, the control circuit 30, the memory unit 31, and the like are covered with a radiation shielding member (not shown). The radiation shielding member prevents scattering of radiation inside the housing 40 and irradiation of radiation to each circuit.

  The casing 40 is preferably made of a material that can withstand external impacts and has a mass as light as possible, such as aluminum or an alloy thereof. The radiation incident surface side of the housing 40 is configured using a non-metal that easily transmits radiation, such as carbon fiber. Further, on the back side opposite to the radiation incident surface, it is generated for the purpose of preventing the radiation from being transmitted through the radiation image detector 20 or by the material constituting the radiation image detector 20 absorbing the radiation. In order to prevent the influence from secondary radiation, it is a preferred embodiment to use a material that effectively absorbs radiation, such as a lead plate.

  FIG. 5 is a diagram illustrating a circuit configuration of the imaging panel 21. The imaging panel 21 has a two-dimensionally arranged collection electrode 220 for reading out the stored electric energy according to the intensity of the irradiated radiation. Energy is stored in the capacitor 221. Here, one collecting electrode 220 corresponds to one pixel of the radiation image.

  Between the pixels, scanning lines 223-1 to 223-m and signal lines 224-1 to 224-n are disposed so as to be orthogonal, for example. The capacitor 221- (1,1) is connected to a transistor 222- (1,1) made of a silicon laminated structure or an organic semiconductor. The transistor 222- (1,1) is, for example, a field effect transistor, and the drain electrode or the source electrode is connected to the collecting electrode 220- (1,1), and the gate electrode is connected to the scanning line 223-1. The When the drain electrode is connected to the collection electrode 220- (1,1), the source electrode is connected to the signal line 224-1, and when the source electrode is connected to the collection electrode 220- (1,1), the drain electrode is a signal. Connected to line 224-1. Similarly, the scanning line 223 and the signal line 224 are connected to the collecting electrode 220, the capacitor 221 and the transistor 222 of other pixels.

FIG. 6 is a partial cross-sectional view of the imaging panel 21, and a first layer 211 that emits light according to the intensity of the incident radiation is provided on the radiation irradiation surface side. Examples of radiation include X-rays. In this case, for example, an X-ray that is an electromagnetic wave having a wavelength of about 1 mm (1 × 10 ⁻¹⁰ m) and transmitted through a human body, a ship, an aircraft member, or the like is irradiated. This X-ray is output from the radiation generator 10, and the radiation generator 10 is generally a fixed anode or a rotary anode X-ray tube. In addition, the X-ray tube usually has an anode load voltage of 10 kV to 300 kV, and 20 kV to 150 kV when used for medical purposes.
The first layer 211 is a scintillator having a phosphor as a main component, and emits fluorescence having a wavelength of 300 nm to 800 nm by incident radiation.

The phosphors used in the first layer 211 are tungstate phosphors such as CaWO ₄ , CaWO ₄ : Pb, MgWO, Y ₂ O ₂ S: Tb, Gd ₂ O ₂ S: Tb, La ₂ O _2. S: Tb, (Y, Gd) ₂ O ₂ S: Tb, (Y, Gd) ₂ O ₂ S: Terbium-activated rare earth oxysulfide phosphors such as Tb, Tm, YPO ₄ : Tb, GdPO ₄ : Tb Terbium-activated rare earth phosphate phosphors such as LaPO ₄ : Tb, LaOBr: Tb, LaOBr: Tb, Tm, LaOCl: Tb, LaOCl: Tb, Tm, GdOBr: Tb, GdOBr: Tb, Tm, GdOCl: Tb, Terbium activated rare earth oxyhalide phosphors such as GdOCl: Tb, Tm, thulium activated rare earth oxyhalide phosphors such as LaOBr: Tm, LaOCl: Tm Gadolinium-activated rare earth oxyhalide phosphors such as LaOBr: Gd and LuOCl: Gd, cerium-activated rare earth oxy such as GdOBr: Ce, GdOCl: Ce, (Gd, Y) OBr: Ce, (Gd, Y) OCl: Ce Halide-based phosphors, BaSO ₄ : Pb, BaSO ₄ : Eu ²⁺ , (Ba, Sr) SO ₄ : Eu ²⁺ and other barium sulfate-based phosphors, Ba ₃ (PO4) ₂ : Eu ²⁺ , (Ba ₂ PO ₄ ) ₂ : Eu ²⁺ , Sr ₃ (PO ₄ ) ₂ : Eu ²⁺ , (Sr ₂ PO ₄ ) ₂ : Eu ^2+, etc., divalent europium activated alkaline earth metal phosphate phosphors, BaFCl: Eu ²⁺ , BaFBr: Eu ²⁺ , BaFCl: Eu ²⁺ , Tb, BaFCl: Eu ²⁺ , Tb, BaF ₂ .BaCl ₂ .KCl: Eu ²⁺ , (Ba, Mg) F ₂ .BaCl ₂・ KCl: Eu ²⁺ divalent europium-activated alkaline earth metal fluoride halide phosphor, iodide phosphor such as CsI: Na, CsI: Tl, NaI, KI: Tl, ZnS: Ag, (Zn, Cd ) S: Ag, (Zn, Cd) S: Cu, (Zn, Cd) S: Cu, Ag, and other sulfide-based phosphors, HfP ₂ O ₇ , HfP ₂ O ₇ : Cu, Hf ₃ (PO ₄ ) Hafnium phosphate phosphor such as ₄ , YTaO ₄ , YTaO ₄ : Tm, YTaO ₄ : Nb, (Y, Sr) TaO ₄ : Nb, LuTaO ₄ , LuTaO ₄ : Tm, LuTaO ₄ : Nb, (Lu, Sr) _{TaO 4: Nb, GdTaO 4:} Tm, Mg4Ta 2 O 9: Nb, Gd 2 O 3 · Ta 2 O 5 · B 2 O 3: tantalate based phosphor such as Tb, other, Gd ₂ O ₂ S : Eu ³⁺ , (La, Gd, Lu) ₂ Si ₂ O ₇ : E u, ZnSiO ₄ : Mn, Sr ₂ P ₂ O ₇ : Eu can be used.

In particular, cesium iodide (CsI: X, where X is an activator) and gadolinium oxysulfide (Gd ₂ O ₂ S: X, where X is an activator) are preferred because of their high X-ray absorption and luminous efficiency, and these are used. Thus, a high-quality image with low noise can be obtained.

  In addition, the scintillator has a columnar crystal structure, and the columnar crystal has a light guiding effect, that is, an effect that can reduce the emission of light within the crystal from the side surface of the columnar crystal. It is possible to suppress the decrease in the thickness of the phosphor layer, and by increasing the phosphor layer thickness, X-ray absorption can be increased and graininess can be improved, which is preferable.

  However, the phosphor used in the present invention is not limited to these, and may be any phosphor that outputs electromagnetic waves in a region where the light receiving element has sensitivity such as the visible, ultraviolet, or infrared region by irradiation of radiation. good. The diameter of the phosphor particles used in the present invention is preferably 7 μm or less, particularly 4 μm or less. This is because the smaller the diameter of the phosphor particles, the more it becomes possible to prevent light from being scattered in the scintillator layer, and a higher sharpness can be obtained. The phosphor particles may be dispersed in a binder. Examples of such a binder include polyurethane, vinyl chloride copolymer, vinyl chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, various types of synthesis. Examples thereof include rubber resins, phenol resins, epoxy resins, urea resins, melanin resins, phenoxy resins, silicon resins, acrylic resins, urea formamide resins, and the like. Among these, it is preferable to use polyurethane, polyester, vinyl chloride copolymer, polyvinyl butyral, or nitrocellulose. By using such a preferable binder, it becomes possible to increase the dispersibility of the phosphor and increase the filling rate of the phosphor, thereby contributing to the improvement of the graininess.

  The mass content of the phosphor dispersed in the binder is preferably 90 to 99%. The thickness of the first layer is preferably 20 μm or more (particularly 50 μm or more) from the viewpoint of improving graininess, and is preferably 1 mm or less (particularly 300 μm or less) from the viewpoint of improving sharpness.

In addition, since the fluorescent substance used by this invention is hygroscopic except for a part, it is preferable to seal so that it may not be influenced by environmental moisture. For this reason, for example, the entire imaging panel 21 is sealed by using the methods disclosed in JP-A-11-223890, JP-A-11-249243, JP-A-11-344598, and JP-A-2000-171597. Can do.
Next, a second layer 212 that converts electromagnetic waves (light) output from the first layer into electrical energy is formed on the side of the first layer 211 opposite to the radiation irradiation surface side. The second layer 212 is provided with a diaphragm 212a, a transparent electrode 212b, an electron acceptor layer 212c, an electron donor layer 212d, and a conductive layer 212f from the first layer 211 side. The electron acceptor layer 212c and the electron donor layer 212d used here have the same role as the electron acceptor layer and the electron donor layer in the photoelectric conversion element described above.

  The diaphragm 212a is for separating the first layer 211 from other layers, and for example, Oxi-nitride is used. The transparent electrode 212b can form a thin film using a method such as vapor deposition or sputtering. In addition, a pattern having a desired shape may be formed by a photolithography method, or when high pattern accuracy is not required (about 100 μm or more), a mask having a desired shape is used during vapor deposition or sputtering of the electrode material. A pattern may be formed. This transparent electrode desirably has a transmittance of more than 5%. Further, although depending on the material, the film thickness is preferably 10 nm or more from the viewpoint of improving the uniformity of the film, and preferably 1 μm or less (particularly 200 nm) from the viewpoint of shortening the production time. In the electron acceptor layer 212c and the electron donor layer 212d, electrons and holes are generated by absorbing the electromagnetic wave (light) output from the first layer 211. The holes generated here are collected in the conductive layer 212f, and the electrons are collected in the transparent electrode 212b. In this structure, a hole conductive layer may be formed between the transparent electrode 212b and the electron acceptor layer 212c, and an electron conductive layer may be formed between the electron donor layer 212d and the conductive layer 212f. Not something.

The conductive layer 212f is made of, for example, chromium. In addition, a general metal electrode or the transparent electrode can be selected, but in order to obtain good characteristics, a metal, an alloy, an electrically conductive compound and a mixture thereof having a small work function (4.5 eV or less) are used. What is used as an electrode material is preferable. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, indium, lithium / aluminum mixtures, all rare earths and the like. The conductive layer 212f can be generated using a method such as vapor deposition or sputtering using these electrode materials as raw materials. The sheet thickness of the conductive layer 212f is preferably 10 nm or more (particularly 50 nm or more) from the viewpoint of improving the uniformity of the film, and is preferably 1 μm or less (particularly 500 nm) from the viewpoint of shortening the production time.

  A third layer 213 is formed on the side of the second layer 212 opposite to the radiation-irradiated surface side to accumulate electrical energy obtained in the second layer 212 and to output a signal based on the accumulated electrical energy. ing. The third layer 213 includes a capacitor 221 that stores the electrical energy generated in the second layer 212 for each pixel, and a transistor 222 that is a switching element for outputting the stored electrical energy as a signal. . Note that the third layer is not limited to the one using the switching element, and may be configured to generate and output a signal corresponding to the energy level of the stored electrical energy, for example.

  As the transistor 222, for example, a TFT (Thin Film Transistor) is used. This TFT may be an inorganic semiconductor type used in a liquid crystal display or the like or an organic semiconductor type, and is preferably a TFT formed on a plastic film. As the TFT formed on the plastic film, an amorphous silicon type is known, but in addition, it was manufactured by FSA (Fluidic Self Assembly) technology developed by Alien Technology of the United States, that is, made of single crystal silicon. A TFT may be formed on a flexible plastic film by arranging micro CMOS (Nanoblocks) on an embossed plastic film. Furthermore, Science 283, 822 (1999) and Appl. Phys. A TFT using an organic semiconductor as described in documents such as Lett, 771488 (1998), Nature, 403, 521 (2000) may be used.

  As described above, the switching element used in the present invention is preferably a TFT manufactured by the FSA technique and a TFT using an organic semiconductor, and a TFT using an organic semiconductor is particularly preferable. If a TFT is formed using this organic semiconductor, equipment such as a vacuum deposition apparatus is not required as in the case where a TFT is formed using silicon, and the TFT can be formed by utilizing printing technology or inkjet technology. Cost is low. Furthermore, since the processing temperature can be lowered, it can be formed into a plastic substrate shape that is weak against heat.

  Of the TFTs using organic semiconductors, field effect transistors (FETs) are particularly preferable, and specifically, organic TFTs having a structure shown in FIGS. 7A to 7C are preferable. The organic TFT shown in FIG. 7A is obtained by sequentially forming a gate electrode, a gate insulating layer, source / drain electrodes, and an organic semiconductor layer on a substrate. The organic TFT shown in FIG. 7B has a gate electrode, a gate insulating layer, an organic semiconductor layer, and a source / drain electrode formed in this order on a substrate. The organic TFT shown in FIG. A source / drain electrode, a gate insulating layer, and a gate electrode are sequentially formed on a single crystal.

  The compound forming the organic semiconductor layer may be a single crystal material or an amorphous material, and may be a low molecule or a polymer, but particularly preferred are condensed aromatic carbonized carbons represented by pentacene, triphenylene, anthracene, etc. Examples thereof include a single crystal of a hydrogen compound and the π-conjugated polymer.

  The source electrode, the drain electrode, and the gate electrode may be either a metal, a conductive inorganic compound, or a conductive organic compound, but are preferably a conductive organic compound from the viewpoint of ease of production. Lewis acid (iron chloride, aluminum chloride, antimony bromide, etc.), halogen (iodine, bromine, etc.), sulfonate (polystyrene sulfonic acid sodium salt (PSS), p-toluenesulfonic acid And the like. Specific examples include conductive polymers obtained by adding PSS to PEDOT. Specific examples of the organic TFT include those shown in FIG.

  As shown in FIGS. 5 and 6, the transistor 222 that is a switching element accumulates the electric energy generated in the second layer 212 and is connected to a collecting electrode 220 that is one electrode of the capacitor 221. . The capacitor 221 stores the electric energy generated in the second layer 212, and the stored electric energy is read by driving the transistor 222. That is, a signal for each pixel can be generated from the radiation image by driving the switching element. In FIG. 6, the transistor 222 includes a gate electrode 222a, a source electrode (drain electrode) 222b, a drain electrode (source electrode) 222c, an organic semiconductor layer 222d, and an insulating layer 222e.

The fourth layer 214 is a substrate of the imaging panel 21. The substrate preferably used as the fourth layer 214 is a plastic film. Examples of the plastic film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, and polyetherether. Examples thereof include films of ketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC), and cellulose acetate propionate (CAP). Thus, by using a plastic film, it is possible to reduce the weight as compared with the case of using a glass substrate and to improve resistance to impact.
Furthermore, a plasticizer such as trioctyl phosphate or dibutyl phthalate may be added to these plastic films, or a known ultraviolet absorber such as benzotriazole or benzophenone may be added. In addition, a resin prepared by applying a so-called organic-inorganic polymer hybrid method in which a raw material of an inorganic polymer such as tetraethoxysilane is added and the molecular weight is increased by applying energy such as a chemical catalyst, heat, or light. It can also be used as a raw material.

  Further, a power source 34, for example, a primary battery such as a manganese battery, a nickel / cadmium battery, a mercury battery, a lead battery, or a rechargeable secondary battery may be provided on the side opposite to the side surface of the third layer of the fourth layer 214. good. As a form of this battery, a flat form is preferable so that the radiation image detector can be thinned.

  Further, in the imaging panel 21, initialization transistors 232-1 to 232-n connected to, for example, drain electrodes are provided on the signal lines 224-1 to 224-n. The source electrodes of the transistors 232-1 to 232-n are grounded. The gate electrode is connected to the reset line 231.

  The scanning lines 223-1 to 223 -m and the reset line 231 of the imaging panel 21 are connected to the scanning drive circuit 25 as shown in FIG. When the readout signal RS is supplied from the scanning drive circuit 25 to one of the scanning lines 223-1 to 223-m, the scanning line 223-p (p is any value of 1 to m), the scanning line 223. The transistors 222- (p, 1) to 222- (p, n) connected to −p are turned on, and the electricity stored in the capacitors 221- (p, 1) to 221- (p, n) Energy is read out to the signal lines 224-1 to 224-n, respectively. The signal lines 224-1 to 224-n are connected to the signal converters 271-1 to 271-n of the signal selection circuit 27. In the signal converters 271-1 to 271-n, the signal lines 224-1 to 224 are connected. Voltage signals SV-1 to SV-n that are proportional to the amount of electrical energy read on -n are generated. The voltage signals SV-1 to SV-n output from the signal converters 271-1 to 271-n are supplied to the register 272.

  In the register 272, the supplied voltage signal is sequentially selected and converted into a digital image signal for one scanning line (for example, 12 bits to 14 bits) by the A / D converter 273, and the control circuit 30 performs scanning. A scanning signal is supplied to each of the lines 223-1 to 223 -m through the scanning drive circuit 25 to perform image scanning, and a digital image signal for each scanning line is captured to generate an image signal of a radiation image. . This image signal is supplied to the control circuit 30. Note that the reset signal RT is supplied from the scanning drive circuit 25 to the reset line 231 to turn on the transistors 232-1 to 232-n, and the readout signal RS is supplied to the scanning lines 223-1-223-m. When the transistors 222- (1,1) to 222- (m, n) are turned on, the electrical energy stored in the capacitors 221- (1,1) to 221- (m, n) is converted into the transistors 232-1 to 232-1. The imaging panel 21 can be initialized by discharging through 232-n.

  A memory unit 31 and an operation unit 32 are connected to the control circuit 30, and the operation of the radiation image detector 20 is controlled based on an operation signal PS from the operation unit 32. The operation unit 32 is provided with a plurality of switches. Based on the operation signal PS corresponding to the switch operation from the operation unit 32, the imaging panel 21 is initialized and an image signal of a radiographic image is generated. The generation of the image signal of the radiation image may be performed when a radiation irradiation end signal is supplied from the radiation generator 10 via the connector 35. Furthermore, the process etc. which memorize | store the produced | generated image signal in the memory part 31 are also performed.

  Here, as shown in FIG. 4, the radiation image detector 20 is provided with a power supply unit 34 and a memory unit 31 for storing an image signal of the radiation image, and the radiation image detector 20 is detachable via a connector 35. By doing so, a system capable of carrying the radiation image detector 20 can be constructed. Further, if the memory unit 31 is configured to be detachable using a non-volatile memory, the image signal can be obtained only by attaching the memory unit 31 to the image processing unit 51 without connecting the radiation image detector 20 and the image processing unit 51. Can be supplied to the image processing unit 51, so that radiographic images can be easily captured and processed, and operability can be improved. When the radiological image detector 20 is used as a stationary type, by supplying power and reading out an image signal via the connector 35, the radiographic image can be read without providing the memory unit 31 and the power source unit 34. Of course, an image signal can be obtained.

As described above, in the above-described embodiment, the fourth layer 214 serving as the substrate is made of resin, so that the weight can be reduced as compared with the conventional radiation image detector using the glass substrate. In addition, since the fourth layer 214 is made of resin, the third layer 213 formed on the fourth layer 214 is formed by using a divided silicon laminated structure element or an organic semiconductor. Therefore, unlike the conventional radiographic image detector using a glass substrate, it is not necessary to use an expensive and special manufacturing apparatus for forming a thin film transistor mainly composed of silicon on the glass substrate. Can be manufactured at low cost.
Furthermore, since the second layer 212 formed on the third layer 213 is made of a conductive polymer compound and a π-conjugated organic compound, it is not necessary to use an optical semiconductor manufacturing apparatus using silicon. Even in this respect, the radiation image detector can be manufactured at low cost.

  Hereinafter, although the photoelectric conversion element in this invention is explained in full detail according to an Example, this invention is not limited to these.

  In addition, the structure of the electron donor and the electron acceptor used for the Example is shown by the said exemplary compound.

(Comparative Example 1)
(1) Fabrication of element A pyromellitic imide derivative (compound 1-5) film as an electron acceptor layer is thick on an ITO transparent electrode (1 cm long, 1 cm wide, 0.5 mm thick) formed on a glass substrate. The film was formed by vapor deposition at a thickness of 50 nm. Further, an oligothiophene (compound 1-1) film was formed as an electron donor layer on the electron acceptor layer by a vapor deposition method with a thickness of 100 nm. Thereafter, an aluminum counter electrode having a thickness of 100 nm was formed on the electron donor layer by vapor deposition, and the device was sealed with an epoxy resin adhesive.

(2) Evaluation of the device The exposed surface of the photoelectric conversion device is set to 0.5 cm × 0.5 cm using a masking tape, and immediately after the device is manufactured and one month after the device is manufactured, a halogen lamp is used. White light was irradiated to the entire exposed surface of the photoelectric conversion element under the conditions of an irradiation wavelength of 550 nm, a light amount of 1 mW / cm ² and a voltage of 0 V, and the photocurrent was measured with an ammeter.

  Table 1 shows the relative photocurrent value immediately after production in Comparative Example and Examples 1 to 7 and the relative photocurrent value after one month (the relative photocurrent value was measured immediately after production of Comparative Example 1). This is the relative value of the photocurrent with the photocurrent value being 1. The photocurrent value is proportional to the photoelectric conversion efficiency.

(Example 1)
12 ITO transparent electrodes (1 cm long, 1 cm wide, 0.5 mm thick) formed on a glass substrate in 5 ml of a tetrahydrofuran (THF) / ethanol = 1: 1 solution in which a pyromellitic imide derivative (compound 1-5) is dissolved. After soaking for an hour, the ITO transparent electrode was taken out, washed with a THF / ethanol = 1: 1 solution, and then dried to form a monomolecular film of an electron acceptor layer on the ITO electrode. Further, an oligothiophene (compound 1-1) film was formed as an electron donor layer on the electron acceptor layer by a vapor deposition method with a thickness of 100 nm. Thereafter, an aluminum counter electrode having a thickness of 100 nm was formed on the electron donor layer by vapor deposition, and the device was sealed with an epoxy resin adhesive. The element evaluation was performed in the same manner as in Comparative Example 1, and the results are shown in Table 1.

(Example 2)
An ITO transparent electrode (1 cm long, 1 cm wide, 0.5 mm thick) formed on a glass substrate was immersed in 5 ml of a THF / ethanol = 1: 1 solution in which a pyromellitic imide derivative (compound 1-5) was dissolved for 12 hours. Thereafter, the ITO transparent electrode was taken out, washed with a THF / ethanol = 1: 1 solution, and then dried to form a monomolecular film of an electron acceptor layer on the ITO electrode. Further, polycarbazole (compound 1-2) as an electron donor layer was spin-coated on the electron acceptor layer at a thickness of 100 nm using a spin coater. The spin coating conditions were performed at 1000 to 2000 rpm using a chloroform solution in which polycarbazole was dissolved at 40 mg / ml (the reason for using the spin coating method without using the vapor deposition method is that the spin coating method is more effective than the vapor deposition method). Film formation is easier with this method, and since high molecular compounds (polymers) have film-forming properties, spin coating is possible, and because of their high boiling point and high melting point, vapor deposition is difficult. The following polymers were all formed by spin coating.) Next, annealing was performed at 60 ° C. for 30 minutes to remove residual solvent. Thereafter, an aluminum counter electrode having a thickness of 100 nm was formed on the electron donor layer by vapor deposition, and the device was sealed with an epoxy resin adhesive. The element evaluation was performed in the same manner as in Comparative Example 1, and the results are shown in Table 1.

(Example 3)
An ITO transparent electrode (1 cm long, 1 cm wide, 0.5 mm thick) formed on a glass substrate was immersed in 5 ml of a THF / ethanol = 1: 1 solution in which a naphthimide derivative (compound 1-6) was dissolved, for 12 hours, Thereafter, the ITO transparent electrode was taken out, washed with a THF / ethanol = 1: 1 solution, and then dried to form a monomolecular film of an electron acceptor layer on the ITO electrode. Further, polycarbazole (compound 1-2) as an electron donor layer was spin-coated on the electron acceptor layer at a thickness of 100 nm using a spin coater. The spin coating was performed at 1000 to 2000 rpm using a chloroform solution in which polycarbazole was dissolved at 40 mg / ml. Next, annealing was performed at 60 ° C. for 30 minutes to remove residual solvent. Thereafter, an aluminum counter electrode having a thickness of 100 nm was formed on the electron donor layer by vapor deposition, and the device was sealed with an epoxy resin adhesive. The element evaluation was performed in the same manner as in Comparative Example 1, and the results are shown in Table 1.

Example 4
An ITO transparent electrode (1 cm long, 1 cm wide, 0.5 mm thick) formed on a glass substrate was immersed in 5 ml of a THF / ethanol = 1: 1 solution in which a naphthimide derivative (compound 1-6) was dissolved, for 12 hours, Thereafter, the ITO transparent electrode was taken out, washed with a THF / ethanol = 1: 1 solution, and then dried to form a monomolecular film of an electron acceptor layer on the ITO electrode. Further, polyphenylene vinylene (compound 1-3) was spin-coated on the electron acceptor layer at a thickness of 100 nm using a spin coater as an electron donor layer. The spin coating conditions were performed at 1000 to 2000 rpm using a chloroform solution in which MEH-PPV was dissolved at 40 mg / ml. Next, annealing was performed at 60 ° C. for 30 minutes to remove residual solvent. Thereafter, an aluminum counter electrode having a thickness of 100 nm was formed on the electron donor layer by vapor deposition, and the device was sealed with an epoxy resin adhesive. The element evaluation was performed in the same manner as in Comparative Example 1, and the results are shown in Table 1.

(Example 5)
An ITO transparent electrode (1 cm in length, 1 cm in width, 0.5 mm in thickness) formed on a glass substrate was immersed in 5 ml of a THF / ethanol = 1: 1 solution in which a porphyrin derivative (compound 1-7) was dissolved, for 12 hours, Thereafter, the ITO transparent electrode was taken out, washed with a THF / ethanol = 1: 1 solution, and then dried to form a monomolecular film of an electron acceptor layer on the ITO electrode. Further, polyphenylene vinylene (compound 1-3) was spin-coated on the electron acceptor layer at a thickness of 100 nm using a spin coater as an electron donor layer. The spin coating conditions were performed at 1000 to 2000 rpm using a chloroform solution in which MEH-PPV was dissolved at 40 mg / ml. Next, annealing was performed at 60 ° C. for 30 minutes to remove residual solvent. Thereafter, an aluminum counter electrode having a thickness of 100 nm was formed on the electron donor layer by vapor deposition, and the device was sealed with an epoxy resin adhesive. The element evaluation was performed in the same manner as in Comparative Example 1, and the results are shown in Table 1.

(Example 6)
An ITO transparent electrode (1 cm in length, 1 cm in width, 0.5 mm in thickness) formed on a glass substrate was immersed in 5 ml of a THF / ethanol = 1: 1 solution in which a porphyrin derivative (compound 1-7) was dissolved, for 12 hours, Thereafter, the ITO transparent electrode was taken out, washed with a THF / ethanol = 1: 1 solution, and then dried to form a monomolecular film of an electron acceptor layer on the ITO electrode. Furthermore, polythiophene (compound 1-4) as an electron donor layer was spin-coated on the electron acceptor layer at a thickness of 100 nm using a spin coater. Spin coating conditions were performed at 1000 to 2000 rpm using a chloroform solution in which PHT was dissolved at 40 mg / ml. Next, annealing was performed at 60 ° C. for 30 minutes to remove residual solvent. Thereafter, an aluminum counter electrode having a thickness of 100 nm was formed on the electron donor layer by vapor deposition, and the device was sealed with an epoxy resin adhesive. The element evaluation was performed in the same manner as in Comparative Example 1, and the results are shown in Table 1.

(Example 7)
An ITO transparent electrode (1 cm long, 1 cm wide, 0.5 mm thick) formed on a glass substrate was immersed in 5 ml of a THF / ethanol = 1: 1 solution in which a fullerene derivative (compound 1-8) was dissolved, for 12 hours, Thereafter, the ITO transparent electrode was taken out, washed with a THF / ethanol = 1: 1 solution, and then dried to form a monomolecular film of an electron acceptor layer on the ITO electrode. Furthermore, polythiophene (compound 1-4) as an electron donor layer was spin-coated on the electron acceptor layer at a thickness of 100 nm using a spin coater. Spin coating conditions were performed at 1000 to 2000 rpm using a chloroform solution in which PHT was dissolved at 40 mg / ml. Next, annealing was performed at 60 ° C. for 30 minutes to remove residual solvent. Thereafter, an aluminum counter electrode having a thickness of 100 nm was formed on the electron donor layer by vapor deposition, and the device was sealed with an epoxy resin adhesive. The element evaluation was performed in the same manner as in Comparative Example 1, and the results are shown in Table 1.

  In Table 1, when Comparative Example 1 and Example 1 were compared, the photocurrent value immediately after fabrication was greatly increased by 10.2 times by making the electron acceptor multimolecular film a monomolecular film (photocurrent value). Is proportional to the photoelectric conversion rate, so the photoelectric conversion efficiency is also increased 10.2 times). The photocurrent value after one month also increased by 17 times, but it did not prevent deterioration of the device. Therefore, in Example 2, in order to increase the stability of the photoelectric conversion layer, element evaluation was performed using an electron donor material as a conductive polymer compound instead of a low molecular compound. Comparing Example 1 and Example 2, by changing the electron donor material from oligothiophene (compound 1-1), which is a low molecular compound, to polycarbazole (compound 1-2), which is a conductive polymer compound, The photocurrent value immediately after production increased by 1.5 times, and in particular, the photocurrent value after one month increased significantly by 9 times and became the same value as the photocurrent value immediately after production, and no deterioration was observed. . Next, when Example 2 and Example 3 are compared, the electron acceptor material is a naphthimide derivative (compound 1) which is a π-conjugated compound (here, the π-conjugated compound is an organic compound having 7 or more aromatic π electrons). By setting to −6), the photocurrent value immediately after production increased 1.7 times. Further, when Example 3 and Example 4 are compared, the conductive polymer compound, which is an electron donor material, is changed from polycarbazole (Compound 1-2) to polyphenylene vinylene (Compound 1-3). The photocurrent value increased 2.1 times. Although not specifically shown in the examples, in addition to the polyphenylene vinylene derivative (compound 1-3), the polyphenylene vinylene and derivatives thereof shown in compounds 8-1 to 8-4, and compounds 9-1 to 9-11 were shown. Polythiophene and derivatives thereof, poly (thiophene vinylene) and derivatives thereof shown in compounds 10-1 to 10-3, polyacetylene and derivatives thereof shown in compounds 11-1 to 11-5, and compounds 12-1 to 12-7 For the polypyrrole and derivatives thereof shown, polyfluorene and derivatives thereof shown in compounds 13-1 to 13-8, and polyaniline and derivatives thereof shown in compounds 15-1 to 15-4, the photocurrent values immediately after production were similarly measured. An increasing trend was observed. Next, when Example 4 is compared with Example 5, the porphyrin derivative (compound 1-), which is a compound having a larger π-conjugated system (more aromatic π electrons) than the naphthimide derivative (compound 1-6), is used as the electron acceptor material. By 7), the photocurrent value immediately after the production increased 1.6 times. Here, many examples are not particularly shown, but in addition to the porphyrin derivative (compound 1-7), the porphyrins and derivatives thereof shown in compounds 5-1 to 5-2, compounds 3-1 to 3- The fullerenes and derivatives thereof shown in FIG. 6, the carbon nanotubes and derivatives thereof shown in compound 4-1, and the phthalocyanines and derivatives thereof shown in compounds 6-1 to 6-2 are also increasing in the same manner immediately after production. Was observed. In addition, when Example 5 and Example 6 are compared, the electron donor material is changed from polyphenylene vinylene (compound 1-3) to polythiophene (compound 1-4) having sensitivity at a light irradiation wavelength of 550 nm. The current value increased 1.3 times. Although not specifically shown in the examples, in addition to the polythiophene (compound 1-4) used in the examples, the polythiophene and derivatives thereof shown in compounds 9-1 to 9-11 were similarly increased in photocurrent value. A trend was observed. Further, when Example 6 and Example 7 are compared, the electron acceptor material is changed from a porphyrin derivative (Compound 1-7) to a fullerene derivative (Compound 1-) having a wider π-conjugated system and having a rigid three-dimensional structure. By 8), the charge separation state was further stabilized, and the photocurrent value immediately after the device fabrication increased 1.8 times. Here, although not specifically shown in the examples, in addition to the fullerene derivative (Compound 1-8), the fullerenes shown in Compounds 3-1 to 3-6 and their derivatives were similarly subjected to photocurrent values immediately after the device was fabricated. An increase was observed.

  Next, an embodiment of the radiation image detector in the present invention will be described in detail. The structures of the electron donor and the electron acceptor used in the examples are shown in the above exemplary compounds.

(Comparative Example 2)
(1) Element FIG. 6 shows a partial cross-sectional view of the radiation image detector used in the example. As the scintillator of the first layer, cesium iodide (CsI: Tl) was used, and the thickness was 150 μm. About the 2nd photoelectric converting layer, ITO was used for the transparent electrode and thickness was 100 nm. For the electron acceptor layer, a 50 nm thick multilayer film of a pyromellitic imide derivative (Compound 1-5) was used.

  As the electron donor layer, an oligothiophene (compound 1-1) film having a thickness of 100 nm was used. The conductive layer was made of aluminum and had a thickness of 250 nm. For the third layer, amorphous silicon was used to form the above-described thin film transistor (TFT). For the fourth layer, polyethylene terephthalate (PET) was used.

(2) Evaluation of the device As shown in FIG. 6, X-ray (50 kV) irradiation is performed from the scintillator side of the first layer of the device, and the signal value from the thin layer transistor of the third layer is set immediately after the device is manufactured. Measurement was made one month after the device was fabricated. Table 2 shows the relative signal value immediately after production in Comparative Example and Examples 8 to 14 and the relative signal value after one month (the relative signal value is the signal value measured immediately after production of Comparative Example 2). Relative value set to 1.)

(Example 8)
A partial cross-sectional view of the radiation image detector used in the example is shown in FIG. As the scintillator of the first layer, cesium iodide (CsI: Tl) was used, and the thickness was 150 μm. About the 2nd photoelectric converting layer, ITO was used for the transparent electrode and thickness was 100 nm. A monomolecular film of a pyromellitic imide derivative (Compound 1-5) was used for the electron acceptor layer. As the electron donor layer, an oligothiophene (compound 1-1) film having a thickness of 100 nm was used. Aluminum was used for the conductive layer, and the thickness was 250 nm. For the third layer, amorphous silicon was used to form the above-described thin film transistor (TFT). For the fourth layer, polyethylene terephthalate (PET) was used. The element evaluation was performed in the same manner as in Comparative Example 2, and the results are shown in Table 2.

Example 9
A partial cross-sectional view of the radiation image detector used in the example is shown in FIG. The scintillator of the first layer was cesium iodide (CsI: Tl) and had a thickness of 150 μm. About the 2nd photoelectric converting layer, ITO was used for the transparent electrode and thickness was 100 nm. A monomolecular film of a pyromellitic imide derivative (Compound 1-5) was used for the electron acceptor layer. As the electron donor layer, a polycarbazole (compound 1-2) film having a thickness of 100 nm was used. Aluminum was used for the conductive layer, and the thickness was 250 nm. For the third layer, amorphous silicon was used to form the above-described thin film transistor (TFT). For the fourth layer, polyethylene terephthalate (PET) was used. The element evaluation was performed in the same manner as in Comparative Example 2, and the results are shown in Table 2.

(Example 10)
A partial cross-sectional view of the radiation image detector used in the example is shown in FIG. The scintillator of the first layer was cesium iodide (CsI: Tl) and had a thickness of 150 μm. About the 2nd photoelectric converting layer, ITO was used for the transparent electrode and thickness was 100 nm. A monomolecular film of a naphthimide derivative (Compound 1-6) was used for the electron acceptor layer. As the electron donor layer, a polycarbazole (compound 1-2) film having a thickness of 100 nm was used. Aluminum was used for the conductive layer, and the thickness was 250 nm. For the third layer, amorphous silicon was used to form the above-described thin film transistor (TFT). For the fourth layer, polyethylene terephthalate (PET) was used. The element evaluation was performed in the same manner as in Comparative Example 2, and the results are shown in Table 2.

(Example 11)
A partial cross-sectional view of the radiation image detector used in the example is shown in FIG. The scintillator of the first layer was cesium iodide (CsI: Tl) and had a thickness of 150 μm. About the 2nd photoelectric converting layer, ITO was used for the transparent electrode and thickness was 100 nm. A monomolecular film of a naphthimide derivative (Compound 1-6) was used for the electron acceptor layer. A 100-nm-thick polyphenylene vinylene (compound 1-3) film was used for the electron donor layer, and aluminum was used for the conductive layer to a thickness of 250 nm. For the third layer, amorphous silicon was used to form the above-described thin film transistor (TFT). For the fourth layer, polyethylene terephthalate (PET) was used. The element evaluation was performed in the same manner as in Comparative Example 2, and the results are shown in Table 2.

(Example 12)
A partial cross-sectional view of the radiation image detector used in the example is shown in FIG. The scintillator of the first layer was cesium iodide (CsI: Tl) and had a thickness of 150 μm. About the 2nd photoelectric converting layer, ITO was used for the transparent electrode and thickness was 100 nm. A monomolecular film of a porphyrin derivative (Compound 1-7) was used for the electron acceptor layer. A 100-nm-thick polyphenylene vinylene (compound 1-3) film was used for the electron donor layer. Aluminum was used for the conductive layer, and the thickness was 250 nm. For the third layer, amorphous silicon was used to form the above-described thin film transistor (TFT). For the fourth layer, polyethylene terephthalate (PET) was used. The element evaluation was performed in the same manner as in Comparative Example 2, and the results are shown in Table 2.

(Example 13)
A partial cross-sectional view of the radiation image detector used in the example is shown in FIG. The scintillator of the first layer was cesium iodide (CsI: Tl) and had a thickness of 150 μm. About the 2nd photoelectric converting layer, ITO was used for the transparent electrode and thickness was 100 nm. A monomolecular film of a porphyrin derivative (Compound 1-7) was used for the electron acceptor layer. A 100-nm-thick polythiophene (compound 1-4) film was used for the electron donor layer, and aluminum was used for the conductive layer to a thickness of 250 nm. For the third layer, amorphous silicon was used to form the above-described thin film transistor (TFT). For the fourth layer, polyethylene terephthalate (PET) was used. The element evaluation was performed in the same manner as in Comparative Example 2, and the results are shown in Table 2.

(Example 14)
A partial cross-sectional view of the radiation image detector used in the example is shown in FIG. The scintillator of the first layer was cesium iodide (CsI: Tl) and had a thickness of 150 μm. About the 2nd photoelectric converting layer, ITO was used for the transparent electrode and thickness was 100 nm. A monomolecular film of a fullerene derivative (Compound 1-8) was used for the electron acceptor layer. A 100-nm-thick polythiophene (compound 1-4) film was used for the electron donor layer. Aluminum was used for the conductive layer, and the thickness was 250 nm. For the third layer, amorphous silicon was used to form the above-described thin film transistor (TFT). For the fourth layer, polyethylene terephthalate (PET) was used. The element evaluation was performed in the same manner as in Comparative Example 2, and the results are shown in Table 2.

  In Table 2, when Comparative Example 2 and Example 8 were compared, the signal value immediately after fabrication was greatly increased by 11.5 times by changing the electron acceptor layer from a multimolecular film to a monomolecular film (the signal value was (Because it is proportional to the conversion rate, the conversion efficiency also increases by 11.5 times.) The signal value after one month also increased 18 times, but it did not prevent deterioration of the device. Therefore, in Example 9, in order to increase the stability of the photoelectric conversion layer, the element evaluation was performed using the conductive layer as the electron donor layer instead of the low molecular compound. Comparing Example 8 and Example 9, by changing the electron donor layer from oligothiophene (compound 1-1), which is a low molecular compound, to polycarbazole (compound 1-2), which is a conductive polymer compound, The signal value immediately after the production increased by 1.4 times, and in particular, the signal value after one month increased significantly by 9.3 times and became the same value as the signal value immediately after the production, and no deterioration was observed. Next, when Example 9 and Example 10 are compared, the electron acceptor layer has a naphthoimide derivative (compound 1) which is a π-conjugated compound (here, the π-conjugated compound is an organic compound having 7 or more aromatic π electrons). By setting to −6), the signal value immediately after the production increased 1.6 times. Further, when Example 10 and Example 11 are compared, the signal value immediately after production is 2.0 times by changing the electron donor layer from polycarbazole (compound 1-2) to polyphenylene vinylene (compound 1-3). Increased to. Although not specifically shown in the examples, in addition to the polyphenylene vinylene derivative (compound 1-3), the polyphenylene vinylene and derivatives thereof shown in compounds 8-1 to 8-4 and compounds 9-1 to 9 were used for the electron donor layer. -11, polythiophene and derivatives thereof, poly (thiophene vinylene) and derivatives thereof shown in compounds 10-1 to 10-3, polyacetylene and derivatives thereof shown in compounds 11-1 to 11-5, compound 12-1 To 12-7, polypyrrole and derivatives thereof, polyfluorene and derivatives thereof shown in compounds 13-1 to 13-8, poly (p-phenylene) and derivatives thereof shown in compounds 14-1 to 14-3, Similarly, the polyaniline and its derivatives shown in compounds 15-1 to 15-4 are also increasing in signal value immediately after production. It was observed. Next, when Example 11 and Example 12 are compared, the porphyrin derivative (compound 1-) in which the electron acceptor layer is a compound having a larger π-conjugated system (more aromatic π electrons) than the naphthimide derivative (compound 1-6). By 7), the signal value immediately after fabrication increased 1.6 times. Here, although not specifically shown in the examples, the porphyrin derivative shown in compounds 5-1 to 5-2 and its derivatives, compounds 3-1 to 5-2 other than the porphyrin derivative (compound 1-7) are used for the electron acceptor layer. In the same manner, the signal values immediately after production of fullerenes and derivatives thereof shown in 3-6, carbon nanotubes and derivatives thereof shown in compounds 4-1 and phthalocyanines and derivatives thereof shown in compounds 6-1 to 6-2 are also increased. A trend was observed.

  Further, when Example 12 and Example 13 are compared, the signal value immediately after production is obtained by changing the electron donor layer from polyphenylene vinylene (compound 1-3) to polythiophene (compound 1-4) having sensitivity by scintillator fluorescence. Increased 1.3 times. Although not specifically shown in the examples, in addition to the polythiophene (compound 1-4) in which the electron donor layer was used in the examples, the polythiophene and derivatives thereof shown in compounds 9-1 to 9-11 were similarly used. A trend of increasing signal values was observed. Further, comparing Example 13 and Example 14, the electron acceptor layer was changed from a porphyrin derivative (Compound 1-7) to a fullerene derivative (Compound 1-) having a wider π-conjugated system and having a rigid three-dimensional structure. With 8), the charge separation state was further stabilized, and the signal value immediately after the device fabrication increased 1.8 times. Although not specifically shown in the examples, the electron acceptor layer was also used for the fullerenes and their derivatives shown in the compounds 3-1 to 3-6 in addition to the fullerene derivative (compound 1-8). An increase in the signal value of was observed.

It is a figure which shows sectional drawing of a photoelectric conversion element. It is a figure which shows an example of a structure of a monomolecular film. It is a figure which shows an example of the system using a radiographic image detector. It is a figure which shows an example of the structure of a radiographic image detector. It is a figure which shows the circuit structure of a radiographic image detector. It is a partial cross section figure of an imaging panel. It is a figure which shows the structure of organic TFT. It is a figure which shows the specific example of organic TFT.

Explanation of symbols

2 Photoelectric conversion layer 10 Radiation generator 20 Radiation image detector 21 Imaging panel 25 Scanning drive circuit 27 Signal selection circuit 30 Control circuit 31 Memory unit 32 Operation unit 33 Display unit 34 Power supply unit 35 Connector 40 Housing 51 Image processing unit 52 Image Display unit 53 Operation input unit 54 Image output unit 55 Image storage unit 211 First layer 212 Second layer 212a Diaphragm 212b Transparent electrode 212c Electron acceptor layer 212d Electron donor layer 212f Counter electrode (conductive layer)
213 Third layer 214 layer 220 Collection electrode 221 Capacitor 222, 232 Transistor 223 Scan line 224 Signal line 231 Reset line 271 Signal converter 272 Register 273 A / D converter

Claims (12)

In a photoelectric conversion element having a transparent electrode, a photoelectric conversion layer that absorbs light transmitted through the transparent electrode and performs charge separation, and a counter electrode provided on the opposite side of the transparent electrode with the photoelectric conversion layer interposed therebetween, The conversion layer has an electron acceptor layer and an electron donor layer that are separate from the transparent electrode and the counter electrode, and the electron acceptor layer has a monomolecular film. The photoelectric conversion element according to claim 1, wherein the electron acceptor layer contains a π-conjugated compound. The photoelectric conversion element according to claim 1, wherein the electron donor layer contains a conductive polymer compound. The conductive polymer compound includes polyphenylene vinylene and derivatives thereof, polythiophene and derivatives thereof, poly (thiophene vinylene) and derivatives thereof, polyacetylene and derivatives thereof, polypyrrole and derivatives thereof, polyfluorene and derivatives thereof, poly (p-phenylene) And at least one of polyaniline and derivatives thereof, or a derivative thereof, or the photoelectric conversion element according to claim 3. The photoelectric conversion element according to claim 2, wherein the π-conjugated compound contains at least one of fullerene and a derivative thereof, carbon nanotube and a derivative thereof, porphyrin and a derivative thereof, phthalocyanine and a derivative thereof. . The conductive polymer compound contains at least one of polythiophene and a derivative thereof, and the π-conjugated compound contains at least one of fullerene and a derivative thereof. The photoelectric conversion element of Claim 3 or Claim 4. A first layer that emits light in accordance with the intensity of incident radiation; a second layer that converts light energy output from the first layer into electrical energy; and storage of electrical energy obtained in the second layer; A radiological image detector having a third layer for outputting a signal based on the stored electrical energy, and a fourth layer for holding the third layer from the first layer, wherein the second layer is a transparent electrode and an electron donor layer And a radiographic image detector comprising an electron acceptor layer having a monomolecular film therebetween. The radiation image detector according to claim 7, wherein the electron acceptor layer contains a π-conjugated compound. The radiation image detector according to claim 7, wherein the electron donor layer contains a conductive polymer compound. The conductive polymer compound includes polyphenylene vinylene and derivatives thereof, polythiophene and derivatives thereof, poly (thiophene vinylene) and derivatives thereof, polyacetylene and derivatives thereof, polypyrrole and derivatives thereof, polyfluorene and derivatives thereof, poly (p-phenylene) The radiation image detector according to claim 9, further comprising at least one of a polyaniline and a derivative thereof. The radiological image detection according to claim 8, wherein the π-conjugated compound contains at least one of fullerene and a derivative thereof, carbon nanotube and a derivative thereof, porphyrin and a derivative thereof, phthalocyanine and a derivative thereof. vessel. The conductive polymer compound includes at least one of polythiophene and a derivative thereof, and the π-conjugated compound includes at least one of fullerene and a derivative thereof. The radiation image detector according to claim 10.

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