JP2006319275A - Photoelectric conversion element and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element which includes a layer comprised of an organic material and reduces an operating voltage, and an imaging device employing said photoelectric conversion element. <P>SOLUTION: A photoelectric conversion element comprises a photoelectric conversion film including an organic layer comprised of an organic material wherein the organic layer is comprised of any one of a micro-crystal, polycrystal, or monocrystal of organic molecules. The photoelectric conversion film may also be a multilayered structure including a photoelectric conversion layer, and the photoelectric conversion film may also include an electron injection blocking layer and a hole injection blocking layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element having a layer made of an organic material, and an imaging element using the photoelectric conversion element.

  Currently, for example, Si and a-Se are used as a photoelectric conversion layer in a photoelectric conversion element used for an imaging element such as a television camera. An imaging device using these materials has a prism that separates incident light into three primary colors of blue, green, and red in order to be color-compatible, and further includes three photoelectric conversion layers corresponding to the colors. It has a so-called three-plate type.

  However, since it is difficult to reduce the size and weight of the three-plate image sensor, a single-plate structure that can be reduced in size and weight has been proposed. For example, red, green as color pixels in the plane of the photoelectric conversion layer. A blue filter with Bayer arrangement has been proposed (see, for example, Non-Patent Document 1).

  However, in the above Bayer structure, since it is necessary to form one pixel with only one of red, green, and blue, the resolution is poor, and incident light other than the desired color is absorbed by the color filter. Therefore, there was a problem that the light utilization efficiency was poor.

  Such problems of resolution and light utilization efficiency can be improved by using, for example, a photodiode formed so that the impurity concentration differs in the light entrance direction (see, for example, Patent Document 1).

  However, when the charge readout unit of the photodiode is installed, it must be installed on the same plane as the light receiving surface due to the structure of the photodiode, and the aperture ratio of the photoelectric conversion unit is reduced. It was inevitable.

  Therefore, in order to solve such a problem, a method for forming a photoelectric conversion element by laminating a plurality of photoelectric conversion layers having wavelength selectivity has been proposed (see, for example, Patent Document 2). In the case of forming a photoelectric conversion layer having such wavelength selectivity, an organic material is preferable because many organic materials have a characteristic of absorbing only a specific wavelength region. For example, by using a molecular design to efficiently absorb the three primary colors of blue, green, and red using an organic material, a photoelectric conversion layer having good sensitivity for each wavelength region can be formed. .

  By using a photoelectric conversion element in which photoelectric conversion layers having such wavelength selectivity are laminated, a single-plate type, which can be easily reduced in size and weight, and has an excellent resolution and light utilization efficiency is formed. Is possible.

  FIG. 1 is a cross-sectional view schematically showing an example of a photoelectric conversion element formed using an organic material.

  Referring to FIG. 1, a photoelectric conversion element 1A shown in this figure has a photoelectric conversion film 1B including a photoelectric conversion layer 3 made of an organic material in which electron-hole pairs are generated by the incidence of light. .

  An anode 1 and a cathode 5 are connected to the photoelectric conversion film 1 </ b> B, and a predetermined voltage is applied between the anode 1 and the cathode 5 by a voltage applying means 6. In addition, the photoelectric conversion film 1 </ b> B may include the hole injection blocking layer 2 and the electron injection blocking layer 4.

  For example, the hole injection blocking layer 2 is formed between the anode 1 and the photoelectric conversion layer 3, and the electron injection blocking layer 4 is formed between the cathode 5 and the photoelectric conversion layer 3. The hole injection blocking layer 2 and the electron injection blocking layer 4 suppress the generation of dark current due to the injection of holes or electrons from the electrodes into the photoelectric conversion layer 3. It has a function to improve S / N.

When light is incident on the photoelectric conversion element 1A, electrons and holes generated in the photoelectric conversion layer 3 move to the anode 1 and the cathode 5, respectively, and are detected as photocurrents (optical signals). Conversion is performed. Further, in this figure, the case where the photoelectric conversion layer 3 is a single layer is shown as an example. However, if the photoelectric conversion layer 3 is composed of a plurality of layers having different wavelength regions to be absorbed, color correspondence is possible.
USP 5965875 gazette JP 2002-217474 A Yuji Kiuchi, Image Sensor Basics and Applications, p145

  As the organic material used for the photoelectric conversion layer, an amorphous material has been used in order to ensure stability during operation. Electron and hole conduction in an amorphous solid is caused by electrons hopping between individual molecules using an external electric field as a driving force, and this conduction is called hopping conduction.

The charge mobility in hopping conduction is about 10 ⁻³ cm ² / Vs, but actually it is necessary to thermally excite electrons and holes trapped in a deep level to a level where hopping occurs. Therefore, the mobility of the charge is often a ^{10 -3 cm 2 / Vs~10 -7 cm} 2 / Vs about.

Since such an organic material is a substantial insulator usually exhibiting a resistivity of 10 ¹⁵ Ωcm or more, for example, in the photoelectric conversion element 10 of FIG. When the conversion layer 3 is formed, a photocurrent is observed by applying an electric field of about 10 ⁶ V / cm or more.

  For example, in the case of an organic EL element (light-emitting element), in addition to reducing the film thickness of the entire organic film to some extent, a layer structure that facilitates current injection from the electrode suppresses the operating voltage. . However, in the case of a photoelectric conversion element, current injection from the electrode causes a decrease in S / N (increase in dark current) of the element, so that it is difficult to form a layer structure in which current injection is easy. Thus, it is preferable to provide an electron or hole injection blocking layer.

Therefore, the photoelectric conversion element requires a larger electric field than the light emitting element, and in order to obtain a practical photocurrent, the electric field of the photoelectric conversion film is preferably about 10 ⁶ V / cm or more. For example, when the total thickness of the hole injection blocking layer 2, the electron injection blocking layer 4, and the photoelectric conversion layer 3 is 300 nm, in order to obtain an electric field of 10 ⁶ V / cm, the anode 1 and the The voltage between the cathodes 5 needs to be 30V.

  In this case, if the photoelectric conversion layer 3 is thinned, the operating voltage can be lowered. However, if the photoelectric conversion layer 3 is thin, there is a concern that light is not sufficiently absorbed by the photoelectric conversion layer. There is a limit to the suppression of the operating voltage by reducing the thickness.

  Thus, when application of a high voltage to the photoelectric conversion element is required, not only the power consumption of the imaging apparatus is increased, but also the breakdown voltage of the charge readout circuit of the photoelectric conversion element may be a problem.

  For example, a CMOS (complementary MOS), a TFT (thin film transistor), a CCD (charge coupled device), or the like is used for the charge readout circuit. Such a read circuit has a low withstand voltage, and may be damaged when the above voltage is applied.

  For example, when a short circuit occurs in a layer made of an organic material or a part where the resistance value is partially reduced, a high voltage is applied to the read circuit, and the read circuit may be damaged. was there.

  For this reason, when using a photoelectric conversion element including an organic layer, it is difficult to use a conventional charge readout circuit, and a charge readout circuit that can withstand high voltage is configured, or a protection circuit for the charge readout circuit is separately configured. There is a problem that the structure of the image sensor is complicated.

  It is an object of the present invention to provide a novel and useful photoelectric conversion element that solves the above problems, and an imaging element using the photoelectric conversion element.

  A specific problem of the present invention is to provide a photoelectric conversion element including an organic material layer in which an operating voltage is suppressed, and an imaging element using the photoelectric conversion element.

  In the first aspect of the present invention, the above-described problem is a photoelectric conversion element having a photoelectric conversion film including an organic layer made of an organic material, wherein the organic layer is a microcrystal, a polycrystal, or a single molecule of an organic molecule. This is solved by a photoelectric conversion element characterized by being an organic layer made of any one of crystals.

  The photoelectric conversion element has a simple structure, can be reduced in size and weight, and has a low operating voltage.

  In addition, when the organic layer is a photoelectric conversion layer and the thickness of the photoelectric conversion layer is 50 nm to 500 nm, it is possible to suppress the operating voltage while improving the photoelectric conversion efficiency of incident light.

  Further, when the organic layer is an electron injection blocking layer or a hole injection blocking layer, and the thickness of the electron injection blocking layer or the hole injection blocking layer is 10 nm to 200 nm, an electron or hole photoelectric conversion layer is formed. Injection is prevented, and charge extraction efficiency is improved, which is preferable.

  According to a second aspect of the present invention, the above-described problem is solved by an imaging device comprising the above-described photoelectric conversion element and charge reading means for reading out the charge generated in the photoelectric conversion element. To do.

  The image sensor has a simple structure, can be reduced in size and weight, and has a low operating voltage.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the photoelectric conversion element by which the layer which consists of organic materials and the operating voltage was reduced, and the image pick-up element using the said photoelectric conversion element.

  A photoelectric conversion element according to the present invention is a photoelectric conversion element having a photoelectric conversion film including an organic layer made of an organic material, and the organic layer is an organic molecule of a microcrystal, a polycrystal, or a single crystal of an organic molecule. It is characterized by being a layer. For this reason, the charge mobility of the organic layer is improved, and the operating voltage of the photoelectric conversion layer can be reduced.

  In this case, the photoelectric conversion film includes a photoelectric conversion layer in which electron-hole pairs are generated when light enters. Further, if necessary, the photoelectric conversion layer may be laminated with a hole injection blocking layer or an electron injection blocking layer to constitute the photoelectric conversion layer.

  In the case of the above configuration, at least one of the photoelectric conversion layer, the hole injection blocking layer, and the electron injection blocking layer is formed of an organic layer of organic crystal microcrystal, polycrystal, or single crystal, and Two layers of the photoelectric conversion layer, the hole injection blocking layer, and the electron injection blocking layer may be formed of organic layers of organic crystal microcrystals, polycrystals, or single crystals. Further, the three layers of the photoelectric conversion layer, the hole injection blocking layer, and the electron injection blocking layer may be composed of organic layers of organic crystal microcrystals, polycrystals, or single crystals.

  Here, the crystal refers to a solid formed by regularly arranging organic molecules three-dimensionally. Of these, in all regions of a solid made of a certain organic molecule, the molecules are substantially completely arranged regularly. This is called a single crystal. In addition, a crystal in which a large number of fine crystal grains are bonded in different orientations is called a polycrystal, and a crystal having a size of several μm or less, particularly a few to several hundred nm, is called a microcrystal. (Same below).

Usually, when an atom has a periodic structure like an inorganic semiconductor crystal, there is a forbidden band between which the existence of electrons is not allowed between the valence band and the conduction band. Such a structure is called a band structure, and electrons and holes excited from the valence band to the conduction band move by the band conduction mechanism. In general, the mobility of band conduction electrons is 10 cm ² / Vs or more.

  On the other hand, in general amorphous organic materials, as described above, conduction of electrons and holes in an amorphous solid is caused by hopping conduction.

The charge mobility in hopping conduction is about 10 ⁻³ cm ² / Vs, and actually, it is necessary to thermally excite electrons and holes trapped in deep levels to the level where hopping occurs. It is often about 10 ⁻³ cm ² / Vs to 10 ⁻⁷ cm ² / Vs.

  Therefore, in the present invention, the organic layer used for the photoelectric conversion film includes any one of a microcrystal, a polycrystal, and a single crystal. The organic molecules used in the organic layer are bonded with a weak interaction between the organic molecules. In this case, in the organic layer, although the charge mobility is smaller than the band conduction, the charge mobility is larger than the hopping conduction. For this reason, the operating voltage is lower than that of the photoelectric conversion element using the conventional organic layer. It is possible to do.

For example, in an organic layer containing any one of a microcrystal, a polycrystal, and a single crystal according to the present invention, the electron mobility is about 0.1-10 cm ² / Vs, which is an intermediate between band conduction and hopping conduction. It is a typical value.

  Next, specific examples of the configuration of the photoelectric conversion element according to the present invention will be described below with reference to the drawings.

  FIG. 2 is a cross-sectional view schematically showing an example of the photoelectric conversion element according to Example 1 of the present invention.

  Referring to FIG. 2, the photoelectric conversion element 10 according to the present embodiment includes a photoelectric conversion film 10 </ b> A including a photoelectric conversion layer 13 made of an organic material in which electron-hole pairs are generated by the incidence of light. .

  An anode 11 and a cathode 15 are connected to the photoelectric conversion film 10 </ b> A, and a predetermined voltage is applied between the anode 11 and the cathode 15 by a voltage applying unit 16. Further, the photoelectric conversion film 10 </ b> A may include a hole injection blocking layer 12 and an electron injection blocking layer 14.

  For example, the hole injection blocking layer 12 is formed between the anode 11 and the photoelectric conversion layer 13, and the electron injection blocking layer 14 is formed between the cathode 15 and the photoelectric conversion layer 13. The hole injection blocking layer 12 and the electron injection blocking layer 14 suppress the generation of dark current due to the injection of holes or electrons from the electrode into the photoelectric conversion layer 13, and the S / It has a function of improving N.

  In this case, in order to improve the effect of suppressing dark current, for example, when the injection of holes from the anode 11 to the photoelectric conversion layer 13 is suppressed, the work function of the anode 11 and the hole injection What is necessary is just to enlarge the difference of the ionization potential of the blocking layer 12. Further, when the injection of electrons from the cathode 15 to the photoelectric conversion layer 13 is suppressed, the difference between the work function of the cathode 15 and the electron affinity of the electron injection blocking layer 14 may be increased.

  When light enters the photoelectric conversion element 10, electrons and holes generated in the photoelectric conversion layer 13 move to the anode 11 and the cathode 15, respectively, and are detected as photocurrents (optical signals). Conversion is performed. Further, in this figure, the case where the photoelectric conversion layer 13 is a single layer is shown as an example. However, if the photoelectric conversion layer 13 is composed of a plurality of layers having different wavelength regions to be absorbed, color correspondence is possible.

  In the photoelectric conversion element 10 according to the present embodiment, the photoelectric conversion layer 13 is formed of an organic layer made of any one of an organic molecular microcrystal, a polycrystal, and a single crystal (the method of making will be described later). For this reason, the mobility of the electron and the hole in the said photoelectric converting layer 13 is large compared with the case of the photoelectric converting layer formed of the amorphous organic layer, and the effect that the operating voltage of a photoelectric conversion element is reduced. Play.

  Further, the same effect can be obtained even when the hole injection blocking layer 12 and the electron injection blocking layer 14 are composed of organic layers made of organic crystal microcrystals, polycrystals, or single crystals.

  As described above, this embodiment is characterized in that the photoelectric conversion film 10A is composed of an organic layer made of organic crystal microcrystals, polycrystals, or single crystals. Further, at least one of the photoelectric conversion layer 13, the hole injection blocking layer 12, and the electron injection blocking layer 14 is an organic layer made of any one of an organic molecular microcrystal, a polycrystal, or a single crystal. It only has to be configured. In this case, the operating voltage can be lowered as compared with the case where a photoelectric conversion film made of an amorphous organic layer is used.

  Further, two of the photoelectric conversion layer 13, the hole injection blocking layer 12, and the electron injection blocking layer 14 are each composed of an organic layer made of any one of organic crystal microcrystals, polycrystals, or single crystals. May be. Further, the photoelectric conversion layer 13, the hole injection blocking layer 12, and the electron injection blocking layer 14 may each be composed of an organic layer made of organic crystal microcrystal, polycrystal, or single crystal. Good.

  In addition, as a method for crystallization of the organic layer, a method for forming a normal single crystal, polycrystal, or microcrystal related to an organic molecule can be used. It can be classified into crystallization by phase growth.

  For example, in crystallization from a solution, a saturated solution of molecules to be crystallized is prepared and then slowly changed to a supersaturated state. For example, there are methods such as crystallization by controlling the temperature of the solution, crystallization by evaporating the solvent, crystallization by diffusion, and crystallization by solution diffusion.

  On the other hand, examples of crystallization by vapor phase growth include the following methods. For example, in the case of a molecule having good stability against temperature change, a molecular crystal can be obtained by performing vapor phase growth by a sublimation method using a glass tube or the like.

  In addition to the above, the crystal growth method can be appropriately selected depending on the properties of the molecules to be used and the crystal state to be formed, such as a melt growth method, a growth method from a gel state, or a growth method by heat treatment of an amorphous organic layer.

  In addition, as the organic material constituting the organic layer, various materials that form crystals can be used. For example, organic pigments, organic nonlinear crystal materials, amino acids, proteins, low molecular electron transport materials, A low molecular hole transport material, a low molecular electron injection blocking material, a low molecular hole injection blocking material, or the like can be used.

  Next, an example of the thickness of the layer constituting the photoelectric conversion film 10A will be described. First, since the hole injection blocking layer 12 and the electron injection blocking layer 14 are too thin, the charge injection blocking function does not work. Moreover, since the extraction efficiency of the electric charge produced | generated in the said photoelectric converting layer 13 will fall when these film thickness is too thick, it is preferable that it is below predetermined thickness.

  From these conditions, for example, when the hole injection blocking layer 12 and the electron injection blocking layer 14 are organic layers made of microcrystals, polycrystals, or single crystals of organic molecules, the hole injection blocking layer 12 is used. The thickness of the electron injection blocking layer 14 is preferably about 10 nm to 200 nm. When the hole injection blocking layer 12 and the electron injection blocking layer 14 are made of an amorphous organic layer of organic molecules, the film thickness is preferably about 10 nm to 100 nm.

  Further, the film thickness of the photoelectric conversion layer 13 is preferably set so that the peak of the light absorption rate is about 90% or more. For this reason, the film thickness of the photoelectric conversion layer 13 is a predetermined value. The thickness is preferably greater than or equal to the thickness. In addition, if the photoelectric conversion layer 13 becomes too thick, it is difficult to efficiently take out the generated charges. Therefore, the thickness of the photoelectric conversion layer 13 is preferably equal to or less than a predetermined thickness.

  From these conditions, for example, when the photoelectric conversion layer 13 is made of an organic layer containing a microcrystal, a polycrystal, or a single crystal, the thickness of the photoelectric conversion layer 13 is preferably about 50 nm to 500 nm. . Moreover, when the said photoelectric converting layer 13 consists of an amorphous organic layer, it is preferable that the film thickness of the said photoelectric converting layer 13 is about 50 nm-200 nm.

  Further, the charge reading means (charge reading circuit) for reading the charges generated by the photoelectric conversion element 10 is used without substantially changing, for example, a conventionally used CMOS, TFT, CCD, image pickup tube, or the like. It is possible. Since the operation voltage is suppressed in the photoelectric conversion element according to the present embodiment, the conventionally used charge read-out means can be used as it is without substantially changing without adding countermeasures for withstand voltage. Is a feature. Therefore, it is possible to form an imaging element having a photoelectric conversion element including an organic material with a simple configuration.

  Next, an example in which an imaging device is configured by combining the structure corresponding to the photoelectric conversion element 10 described in Example 1 and the charge reading unit will be described below.

  FIG. 3 is a diagram schematically showing the basic structure of an image sensor using the XY address method. Referring to FIG. 3, in the image sensor 200 according to this embodiment, a structure corresponding to the photoelectric conversion element 10 is formed on a substrate (not shown). On the substrate, a structure (not shown) corresponding to the photoelectric conversion film 10A is stacked on a plurality of pixel electrodes 215 (corresponding to the cathode 15) formed for each pixel arranged in an array. Further, a transparent electrode 211 (corresponding to the anode 11) is laminated.

  The material of the transparent electrode 211 is preferably a highly transparent material that transmits visible light. For example, an inorganic transparent material such as indium tin oxide film (ITO), or PEDT / PSS (Polyethylene dioxythiophene polystyrene sulphonate) Organic conductive materials such as may be used.

  Further, a vertical selection line 201 and a horizontal selection line 202 formed so as to be orthogonal to each other corresponding to the pixel are connected to the vertical scanning control circuit 201A and the horizontal scanning control circuit 202A, respectively. In addition, a transistor 203 is provided for each pixel (only one pixel is shown), the gate electrode of the transistor 203 is the vertical selection line 201, the drain electrode is the pixel electrode 211, and the source electrode is the horizontal selection line 202. It is connected.

  In the image sensor according to the present embodiment, a signal from the pixel can be extracted by appropriately selecting the pixel by the vertical scanning control circuit 201A and the horizontal scanning control circuit 202A.

  For example, first, one of the plurality of vertical selection lines 201 is selected by the vertical scanning control circuit 201A. Next, pulses are sequentially applied from the right to the left in the figure by the horizontal scanning control circuit 202A, and the charges accumulated in each pixel are output.

  Next, an example of a basic structure of an image sensor in which a structure corresponding to the photoelectric conversion element 10 described in Embodiment 1 and a charge transfer method are combined will be described.

  FIG. 4 is a diagram schematically showing an image pickup device that combines a structure corresponding to the photoelectric conversion device 10 described in the first embodiment and an interline CCD (charge coupled device).

  Referring to FIG. 4, in the image sensor 300 according to the present embodiment, a structure (photodiode) corresponding to the photoelectric conversion element 10 is formed on a substrate (not shown). On the substrate, a structure (not shown) corresponding to the photoelectric conversion film 10A is laminated on pixel electrodes 315 (corresponding to the cathode 15) formed for each pixel, which are arranged in an array. Further, a transparent electrode 311 (corresponding to the anode 11) is laminated.

  As the material of the transparent electrode 311, it is preferable to use a highly transparent material that transmits visible light. For example, an inorganic transparent material such as an indium tin oxide film or an organic conductive material such as PEDT / PSS is used. Also good.

  In the image pickup device 300 according to the present embodiment, a plurality of vertical transfer CCDs 316 are arranged in the vertical direction between the photodiodes arranged in the vertical direction in the drawing, and are further connected to the vertical transfer CCD 316 at the end. A plurality of CCDs 317 are arranged in the horizontal direction.

  In this embodiment, the charges accumulated in the photodiode are transferred to the vertical transfer CCD 316 all at once by a field shift pulse. Subsequently, all the vertical transfer CCDs 316 start to transfer charges in parallel downward (in the direction of the horizontal transfer CCD 317), and each time a signal for one horizontal row is sent to the horizontal transfer CCD 317, the horizontal transfer CCD 317 A signal is output via the output circuit 318.

  The above embodiment has been described by taking an interline type CCD as an example, but the present invention is not limited to this, and for example, a full frame type, a frame transfer type, a frame interline transfer type, etc. may be used. Good.

  In addition, it is preferable that a circuit such as a CMOS, a TFT, or a CCD used for the reading circuit be light-transmitting because an aperture ratio can be increased. Further, the light transmission type readout circuit is more preferably used when the photoelectric conversion layer is a laminated type as shown below, for example.

  As described above, it is preferable that the photoelectric conversion layer has a stacked structure including a plurality of layers having different wavelength regions of light to be absorbed because a simple structure enables color correspondence. For example, among the three primary colors of light, the photoelectric conversion layer and its readout circuit that have photosensitivity mainly in blue, the photoelectric conversion layer and this readout circuit that mainly has photosensitivity in red, and the photoelectric conversion that mainly has photosensitivity in green By laminating the layer and this readout circuit in order, a single-plate multilayer image sensor with high light utilization efficiency and high resolution can be configured.

  A known technique (for example, a method described in Japanese Patent Application Laid-Open No. 2005-51115) can be used as a method for creating a light transmissive readout circuit.

  Further, the charge readout circuit of the photoelectric conversion element is not limited to a solid state element. For example, the image sensor can be configured as a conventional image pickup tube.

  FIG. 5 is a diagram schematically illustrating an imaging tube (imaging device) 400 according to the fourth embodiment of the present invention. Referring to FIG. 5, the imaging tube 400 according to the present embodiment includes a photoelectric conversion film 400 </ b> A corresponding to the photoelectric conversion film 10 </ b> A according to the first embodiment.

  The photoelectric conversion film 400A has a hole injection blocking layer 412 (corresponding to the hole injection blocking layer 12) on the first side of the photoelectric conversion layer 413 (corresponding to the photoelectric conversion layer 13), and the opposite of the first side. The electron injection blocking layer 414 (corresponding to the electron injection blocking layer 14) is formed on the second side. A transparent electrode 411 (corresponding to the anode 11) is formed on the hole injection blocking layer 412, and the transparent electrode 411 is attached to a light transmissive face plate 416.

  The photoelectric conversion film 400A and the transparent electrode 411 are installed so as to be housed in an electron gun casing 417, and the face plate 416 is installed so as to block the opening of the electron gun casing 417. .

  An electron gun 415 is installed in the electron gun casing 417 so as to face the electron injection blocking layer 414. A predetermined voltage is applied between the transparent electrode 411 and the electron gun 415, and the electron beam 419 emitted from the electron gun 415 is scanned on the electron injection blocking layer 414. Here, the charges accumulated in the photoelectric conversion layer 413 are detected as video signals at both ends of the load resistor 418.

  As described above, the charge can be read out by scanning the electron beam using the electron gun.

  Next, the detail is demonstrated below about the example which formed the photoelectric conversion element containing the organic layer containing either a microcrystal, a polycrystal, and a single crystal.

  In this embodiment, an example in which zinc phthalocyanine (ZnPc) having sensitivity to red is used as a photoelectric conversion layer and bathocuproine (BCP) is used as a hole injection blocking layer will be described.

  First, ZnPc and BCP were separately filled in a crucible in a vacuum deposition apparatus, and a glass substrate with a transparent electrode was placed at a height of 20 cm from the top of the crucible.

Next, the inside of the vacuum deposition apparatus is evacuated to about 10 ⁻⁵ Pa, and while heating the glass substrate to 50 ° C., BCP is deposited to a thickness of 180 nm, and then ZnPc is deposited to a thickness of 120 nm. And the photoelectric conversion film was comprised.

  In this case, it was confirmed by visual observation and an optical microscope that BCP formed a polycrystalline film by evaporating BCP while heating the substrate to 50 ° C. In this embodiment, ZnPc also functions as an electron injection blocking layer.

  Next, FIG. 6 shows the result of measuring the applied voltage-signal current by incorporating the formed photoelectric conversion element into the imaging tube.

  In this case, the produced photoelectric conversion element was incorporated into a 2/3 inch electromagnetic convergence / electromagnetic deflection imaging tube. The imaging tube is attached to a monochrome camera and irradiated with light of 5750 lux to measure applied voltage-signal current. The result is shown as Experiment EX2 in FIG. For comparison, the measurement result of the applied voltage-signal current when using a photoelectric conversion element in which the organic layer is not crystallized is shown as Experiment EX1. When forming the photoelectric conversion element used for the experiment EX1, the temperature of the glass substrate during vapor deposition was kept at room temperature. A photoelectric conversion element was formed under the same film forming conditions as in Experiment EX2 except for the temperature of the glass substrate, and the applied voltage-signal current was measured under the same conditions as in Experiment EX1.

  Referring to FIG. 6, for example, in order to obtain a signal current of 40 nA, in the case of Experiment EX1, a voltage of about 33V is required, whereas in the case of Experiment EX2, a voltage of about 9V is sufficient. . For this reason, it was confirmed that the voltage applied to the photoelectric conversion layer was lowered by polycrystallizing BCP.

  Further, using the photoelectric conversion element used in Experiment EX1 and the photoelectric conversion element used in Experiment EX2, TV images were taken and the image quality of the images was compared. In this case, superiority or inferiority in image quality was not observed, and it was confirmed that the imaging characteristics did not deteriorate even when a polycrystalline film was used.

  Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the specific embodiments described above, and various modifications and changes can be made within the scope described in the claims.

It is an example of the structure of the conventional photoelectric conversion element. 1 is a diagram schematically illustrating a photoelectric conversion element according to Example 1. FIG. FIG. 6 is a diagram schematically illustrating an image sensor according to a second embodiment. FIG. 6 is a diagram schematically illustrating an image sensor according to a third embodiment. FIG. 6 is a diagram schematically illustrating an image sensor according to Example 4. It is a figure which shows the effect of this invention.

Explanation of symbols

1A, 10 Photoelectric conversion element 1B, 10A Photoelectric conversion film 200, 300, 400 Image sensor 1,11 Anode 2,12,412 Electron injection blocking layer 3,13,413 Photoelectric conversion layer 4,14,414 Electron injection suppression layer 5 , 15 Cathode 201 Vertical selection line 201A Vertical scanning control circuit 202 Horizontal selection line 202A Horizontal scanning control circuit 203 Transistor 211, 311, 411 Transparent electrode 215, 311 Pixel electrode 316 Vertical transfer CCD
317 Horizontal transfer CCD
318 Output circuit 415 Electron gun 416 Face plate 417 Electron gun housing 418 Load resistance

Claims (4)

A photoelectric conversion element having a photoelectric conversion film including an organic layer made of an organic material,
The photoelectric conversion element, wherein the organic layer is an organic layer made of any one of microcrystals, polycrystals, and single crystals of organic molecules.   The photoelectric conversion element according to claim 1, wherein the organic layer is a photoelectric conversion layer, and the thickness of the photoelectric conversion layer is 50 nm to 500 nm.   2. The photoelectric conversion element according to claim 1, wherein the organic layer is an electron injection blocking layer or a hole injection blocking layer, and the thickness of the electron injection blocking layer or the hole injection blocking layer is 10 nm to 200 nm. . An image pickup device comprising: the photoelectric conversion device according to any one of claims 1 to 3; and charge reading means for reading out electric charges generated in the photoelectric conversion device.

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