Photoelectric conversion element and camera device

Abstract

The photoelectric conversion element of one embodiment of the present application comprises: a first electrode; a second electrode; a photoelectric conversion layer, which is arranged between the first electrode and the second electrode and contains a donor organic semiconductor material and an acceptor organic semiconductor material; and a hole blocking layer, which is arranged between the first electrode and the second electrode and the photoelectric conversion layer. The ionization potential of the photoelectric conversion layer is 5.3 eV or less. The electron affinity of the hole blocking layer is less than the electron affinity of the acceptor organic semiconductor material contained in the photoelectric conversion layer. It has spectral sensitivity in the near-infrared light region with a wavelength of 650nm to 3000nm.

Description

Technical Field

[0001] This application relates to photoelectric conversion elements and camera devices. Background Technology

[0002] Organic semiconductor materials possess physical properties and functions that are not found in conventional inorganic semiconductor materials such as silicon. Therefore, as disclosed in Non-Patent Document 1, organic semiconductor materials have been actively researched in recent years as semiconductor materials that can realize new semiconductor devices and electronic devices.

[0003] For example, studies have been conducted on realizing photoelectric conversion elements by thinning organic semiconductor materials and using them as photoelectric conversion materials. As disclosed in Non-Patent Document 2, photoelectric conversion elements using organic material thin films can be used as organic thin-film solar cells by extracting the charge (i.e., charge carriers) generated by light as energy. Alternatively, as disclosed in Patent Documents 1, 2, and 3, the aforementioned photoelectric conversion elements can be used as light sensors such as imaging elements by extracting the charge generated by light as an electrical signal.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 4677314

[0007] Patent Document 2: Japanese Patent No. 5349156

[0008] Patent Document 3: Japanese Patent No. 5969843

[0009] Non-patent literature

[0010] Non-Patent Literature 1: JANA ZAUMSEIL et al., “Electron and Ambipolar Transport in Organic Field-Effect Transistors”, Chemical Reviews, American Chemical Society, 2007, Vol. 107, No. 4, pp. 1296-1323

[0011] Non-patent literature 2: SERAP GUNES et al., “Conjugated Polymer-Based Orgenic SolarCells”, Chemical Reviews, American Chemical Society, 2007, Vol. 107, No. 4, pp. 1324-1338 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] When organic semiconductor materials are used as photoelectric conversion elements, in order to improve the S / N ratio of the photoelectric conversion element, it is desirable to reduce the current flowing in the dark state, i.e., the dark current.

[0014] This application provides photoelectric conversion elements that have spectral sensitivity in the near-infrared region and can reduce dark current.

[0015] Methods for solving problems

[0016] One embodiment of this application provides a photoelectric conversion element comprising: a first electrode; a second electrode; a photoelectric conversion layer disposed between the first electrode and the second electrode, and comprising a donor organic semiconductor material and an acceptor organic semiconductor material; and a hole blocking layer disposed between one of the first electrode and the second electrode and the photoelectric conversion layer. The ionization potential of the photoelectric conversion layer is 5.3 eV or less. The electron affinity of the hole blocking layer is less than the electron affinity of the acceptor organic semiconductor material contained in the photoelectric conversion layer. It exhibits spectral sensitivity in the near-infrared region with wavelengths from 650 nm to 3000 nm.

[0017] In addition, one aspect of the imaging device of this application includes: a substrate; and a pixel, which includes a charge detection circuit disposed on the substrate, a photoelectric conversion unit disposed on the substrate, and a charge accumulation node electrically connected to the charge detection circuit and the photoelectric conversion unit, wherein the photoelectric conversion unit includes the photoelectric conversion element.

[0018] Invention Effects

[0019] According to this application, photoelectric conversion elements that have spectral sensitivity in the near-infrared region and can reduce dark current can be provided. Attached Figure Description

[0020] Figure 1 This is a schematic cross-sectional view showing an example of a photoelectric conversion element without a hole blocking layer and an electron blocking layer.

[0021] Figure 2 This is a schematic cross-sectional view showing an example of a photoelectric conversion element in an embodiment.

[0022] Figure 3 yes Figure 2 An illustrative band diagram of a photoelectric conversion element is shown.

[0023] Figure 4This is a diagram illustrating an example of the circuit configuration of the camera device in the embodiment.

[0024] Figure 5 This is a schematic cross-sectional view showing an example of the device structure of the pixels of the camera device in the embodiment.

[0025] Figure 6 This is a graph showing the absorption spectrum of the photoelectric conversion layer in Example 1.

[0026] Figure 7 This is a graph showing the absorption spectrum of the photoelectric conversion layer in Example 2.

[0027] Figure 8 This is a graph showing the absorption spectrum of the photoelectric conversion layer of Comparative Example 1.

[0028] Figure 9 This is a graph of the spectral sensitivity spectrum of the photoelectric conversion element in Example 5.

[0029] Figure 10 This is a graph of the spectral sensitivity spectrum of the photoelectric conversion element in Example 6.

[0030] Figure 11 This is a graph of the spectral sensitivity spectrum of the photoelectric conversion element in Comparative Example 9. Detailed Implementation

[0031] (Insights that form the basis of this application)

[0032] In the case of organic semiconductor materials, changing the molecular structure of the organic compound used can alter the energy levels. Therefore, for example, when using organic semiconductor materials as photoelectric conversion materials, it is possible to control the absorption wavelength, enabling them to possess spectral sensitivity in the near-infrared region, where silicon (Si) lacks spectral sensitivity. In other words, by using organic semiconductor materials, it is possible to utilize light in wavelength regions not previously used for photoelectric conversion, enabling the high efficiency of solar cells and near-infrared light region photosensors. Therefore, in recent years, research has been actively conducted on organic semiconductor materials, photoelectric conversion elements, and imaging elements with spectral sensitivity in the near-infrared region. Hereinafter, photoelectric conversion elements using organic semiconductor materials will sometimes be referred to as "organic photoelectric conversion elements."

[0033] To improve spectral sensitivity in the near-infrared region, narrowing the band gap in the electronic excitation of organic semiconductor materials is effective. On the other hand, to improve the signal-to-noise ratio (S / N ratio) of photoelectric conversion elements, in addition to improving photoelectric conversion efficiency, it is also necessary to reduce dark current.

[0034] In organic photoelectric conversion devices, dark current can originate from charge injection from the external electrode and charge generation within the photoelectric conversion layer. When using a bulk heterostructure photoelectric conversion layer composed of a hybrid film of donor and acceptor organic semiconductor materials, charge injection from the cathode is facilitated due to the contact between the donor and acceptor organic semiconductor materials, thus easily generating dark current from charge injection from the external electrode. In particular, when using materials in the near-infrared region of the photoelectric conversion layer, the ionization potential is relatively small due to the narrow bandgap used to lengthen the absorption wavelength, thereby lowering the charge injection barrier from the cathode and promoting charge injection. Therefore, by using a hole-blocking layer with a relatively high ionization potential between the photoelectric conversion layer and the cathode, dark current can be suppressed. However, as mentioned above, dark current can also originate from charge generation within the photoelectric conversion layer. In particular, when using a hole-blocking layer, dark current may be generated due to charge generation at the interface between the photoelectric conversion layer and the hole-blocking layer, making it impossible to sufficiently suppress dark current. The ionization potential and electron affinity of the materials used in the photoelectric conversion layer and hole blocking layer affect the charge generation at the interface between the photoelectric conversion layer and the hole blocking layer.

[0035] The inventors of this invention have discovered that in photoelectric conversion elements with spectral sensitivity in the near-infrared region, dark current can be suppressed by controlling the ionization potential of the photoelectric conversion layer and the electron affinity between the photoelectric conversion layer and the hole blocking layer.

[0036] Therefore, in this application, by controlling the ionization potential of the donor organic semiconductor material and the electron affinity of the acceptor organic semiconductor material and the hole blocking layer, a photoelectric conversion element with spectral sensitivity in the near-infrared region and the ability to reduce dark current is provided.

[0037] A summary of one embodiment of this application is described below.

[0038] One embodiment of this application provides a photoelectric conversion element comprising: a first electrode; a second electrode; a photoelectric conversion layer disposed between the first electrode and the second electrode, and comprising a donor organic semiconductor material and an acceptor organic semiconductor material; and a hole blocking layer disposed between one of the first electrode and the second electrode and the photoelectric conversion layer. The ionization potential of the photoelectric conversion layer is 5.3 eV or less. The electron affinity of the hole blocking layer is less than the electron affinity of the acceptor organic semiconductor material contained in the photoelectric conversion layer. It exhibits spectral sensitivity in the near-infrared region with wavelengths from 650 nm to 3000 nm.

[0039] It should be noted that in this specification, the term "near-infrared region" refers to the wavelength range of light from 650nm to 3000nm.

[0040] Furthermore, in this specification, the phrase "having spectral sensitivity" of a photoelectric conversion element at a certain wavelength means that the external quantum efficiency of the photoelectric conversion element at that wavelength is 1% or higher.

[0041] In this way, by using the photoelectric conversion element of one embodiment of this application, even with spectral sensitivity in the near-infrared region, electron excitation at the interface between the photoelectric conversion layer and the hole blocking layer can be suppressed because the electron affinity of the hole blocking layer is lower than that of the acceptor organic semiconductor material contained in the photoelectric conversion layer. Therefore, a photoelectric conversion element with spectral sensitivity in the near-infrared region and capable of reducing dark current can be provided.

[0042] In addition, for example, the aforementioned photoelectric conversion layer may also have a maximum absorption wavelength in the near-infrared region.

[0043] In this way, since the photoelectric conversion layer has the maximum absorption wavelength in the near-infrared region, the spectral sensitivity in the near-infrared region becomes higher.

[0044] Alternatively, for example, the photoelectric conversion layer may also contain at least one selected from fullerenes and fullerene derivatives as the aforementioned acceptor organic semiconductor material.

[0045] In this way, higher photoelectric conversion efficiency can be obtained because electron movement between donor and acceptor organic semiconductor materials can proceed smoothly.

[0046] Alternatively, for example, the aforementioned receptor-dependent organic semiconductor materials may also contain soluble fullerene derivatives.

[0047] In this way, since the acceptor organic semiconductor material is soluble in solvents, it can be manufactured using printing processes.

[0048] In addition, one aspect of the imaging device of this application includes: a substrate; and a pixel, which includes a charge detection circuit disposed in or on the substrate, a photoelectric conversion unit disposed on the substrate, and a charge accumulation node electrically connected to the charge detection circuit and the photoelectric conversion unit, wherein the photoelectric conversion unit includes the aforementioned photoelectric conversion element.

[0049] Thus, since the imaging device of one embodiment of this application includes the aforementioned photoelectric conversion element, it exhibits spectral sensitivity in the near-infrared region and reduces dark current. Consequently, the signal-to-noise ratio is improved, resulting in excellent imaging characteristics.

[0050] Hereinafter, embodiments of this application will be described in detail with reference to the accompanying drawings.

[0051] It should be noted that the embodiments described below are all general or specific examples. The numerical values, shapes, constituent elements, the arrangement and connection of constituent elements, steps, and the order of steps shown in the following embodiments are examples and are not intended to limit this application. In addition, constituent elements in the following embodiments that are not described in the independent claims representing the highest-level concept are described as optional constituent elements. Furthermore, the figures are not necessarily strictly illustrative. In the figures, the same symbol is used to denote substantially the same constituent element, and repeated descriptions are sometimes omitted or simplified.

[0052] (Implementation Method)

[0053] The following describes this embodiment.

[0054] Photoelectric conversion element

[0055] Hereinafter, the photoelectric conversion element of this embodiment will be used... Figure 1 and Figure 2 The following explanation will be provided. The photoelectric conversion element in this embodiment is, for example, a charge readout type photoelectric conversion element. Figure 1 This is a schematic cross-sectional view of the photoelectric conversion element 10A used to illustrate the photoelectric conversion element of this embodiment. The photoelectric conversion element 10A does not have the hole blocking layer 6 and electron blocking layer 5 described later, but first, the first electrode, i.e., the upper electrode 4, the second electrode, i.e., the lower electrode 2, and the photoelectric conversion layer 3 provided by the photoelectric conversion element of this embodiment will be described.

[0056] The photoelectric conversion element 10A includes: a first electrode, i.e., an upper electrode 4; a second electrode, i.e., a lower electrode 2; and a photoelectric conversion layer 3 disposed between the first electrode and the second electrode. The photoelectric conversion layer 3 is a bulk heterostructure hybrid film formed by mixing donor organic semiconductor materials and acceptor organic semiconductor materials.

[0057] like Figure 1 As shown, the photoelectric conversion element 10A includes a lower electrode 2, an upper electrode 4, and a photoelectric conversion layer 3 disposed between the lower electrode 2 and the upper electrode 4. The photoelectric conversion element 10A includes a photoelectric conversion layer 3 that absorbs light in the near-infrared region.

[0058] The photoelectric conversion element 10A is supported, for example, by a support substrate 1. The support substrate 1 is transparent, and light is incident on the photoelectric conversion element 10A through the support substrate 1. The support substrate 1 can be any substrate used in general photoelectric conversion elements, such as a glass substrate, a quartz substrate, a semiconductor substrate, or a plastic substrate. It should be noted that the term "transparent" in this specification means that at least a portion of the wavelength of light that can be absorbed by the photoelectric conversion layer 3 is transmitted, and does not necessarily mean that light must be transmitted over the entire wavelength range.

[0059] The following describes the constituent elements of the photoelectric conversion element 10A of this embodiment.

[0060] The photoelectric conversion layer 3 of the photoelectric conversion element 10A is made using organic semiconductor materials.

[0061] The photoelectric conversion layer 3 can be fabricated using methods such as spin coating or vacuum evaporation, where the material of the layer is vaporized and deposited onto a substrate under vacuum. In the case of spin coating, film formation can be performed under atmospheric or N2 atmosphere, and at a rotation speed of 300 rpm to 3000 rpm. Furthermore, a baking process can be performed to evaporate the solvent and stabilize the film after spin coating. The baking temperature can be any temperature, for example, 60°C to 250°C.

[0062] As a method for fabricating the photoelectric conversion layer 3, evaporation deposition can also be used, taking into account the need to prevent the introduction of impurities and to allow for more flexible multilayering for high functionality. Commercially available evaporation deposition equipment can also be used. The temperature of the evaporation source during deposition can be 100℃~500℃ or 150℃~400℃. The vacuum level during deposition can be 1×10⁻⁶. -4 Pa ~ 1 Pa, or 1 × 10 -3 Pa ~ 0.1 Pa. Alternatively, the photoelectric conversion layer 3 can also be fabricated by adding metal particles or the like to the evaporation source to increase the evaporation rate.

[0063] The proportions of the materials in the photoelectric conversion layer 3 are expressed as a weight ratio in the coating method and as a volume ratio in the vapor deposition method. More specifically, in the coating method, the proportions are defined by the weight of each material during solution preparation; in the vapor deposition method, the proportions are defined while monitoring the vapor deposition layer thickness of each material using a thickness gauge during vapor deposition.

[0064] Furthermore, the photoelectric conversion layer 3 is composed of a bulk heterolayer as the photoelectric conversion material, which is a hybrid film formed by mixing a donor organic semiconductor material and an acceptor organic semiconductor material. In this case, the acceptor organic semiconductor material may also include at least one of fullerenes and fullerene derivatives. In this way, the photoelectric conversion element 10A can achieve higher photoelectric conversion efficiency because electron movement between the donor and acceptor organic semiconductor materials proceeds smoothly. Additionally, the acceptor organic semiconductor material may also include soluble fullerenes. In this way, since the acceptor organic semiconductor material is soluble in solvents, it can be fabricated using a printing process. Furthermore, details of the donor and acceptor organic semiconductor materials will be described below.

[0065] At least one of the upper electrode 4 and the lower electrode 2 is a transparent electrode made of a conductive material that is transparent to light relative to the response wavelength. A bias voltage is applied to the lower electrode 2 and the upper electrode 4 via wiring (not shown). For example, the polarity of the bias voltage is determined such that, among the charges generated in the photoelectric conversion layer 3, electrons move to the upper electrode 4 and holes move to the lower electrode 2. Alternatively, the bias voltage can be set such that, among the charges generated in the photoelectric conversion layer 3, holes move to the upper electrode 4 and electrons move to the lower electrode 2.

[0066] Furthermore, the bias voltage should preferably be applied in the following manner: the intensity of the electric field generated in the photoelectric conversion element 10A, i.e., the applied voltage value, divided by the distance between the lower electrode 2 and the upper electrode 4, should be 1.0 × 10⁻⁶. 3 V / cm~1.0×10 7 Within the range of V / cm, it can also be 1.0×10. 4 V / cm~1.0×10 6 Within the range of V / cm. By adjusting the magnitude of the bias voltage in this way, the charge can be effectively moved to the upper electrode 4, and the signal corresponding to the charge can be extracted to the outside.

[0067] As materials for the lower electrode 2 and the upper electrode 4, transparent conductive oxides (TCOs) with high transmittance and low resistance in the near-infrared region can also be used. In the case of photoelectric conversion elements with spectral sensitivity in the near-infrared region, thin films of metals such as gold (Au) can also be used as transparent electrodes. However, if a transmittance of over 90% in the near-infrared region is desired, the resistance may increase drastically compared to fabricating transparent electrodes with a transmittance of 60% to 80%. Therefore, compared to metal materials such as Au, TCOs are more likely to produce transparent electrodes with high transparency to near-infrared light and low resistance. TCOs are not particularly limited; examples include ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), AZO (Aluminum-doped Zinc Oxide), FTO (Fluorine-doped Tin Oxide), SnO2, TiO2, and ZnO2. In addition, depending on the desired transmittance, the lower electrode 2 and the upper electrode 4 can be made of TCO, aluminum (Al) and Au, or a combination of these metals, either individually or in combination.

[0068] Furthermore, the materials of the lower electrode 2 and the upper electrode 4 are not limited to the conductive materials with high transmittance for near-infrared light, as described above; other materials may also be used.

[0069] The fabrication of the lower electrode 2 and the upper electrode 4 is carried out using various methods depending on the materials used. For example, when using ITO, methods such as electron beam deposition, sputtering, resistance heating vapor deposition, chemical reaction methods such as sol-gel deposition, and coating of indium tin oxide dispersions can be used. In this case, after forming the ITO film, further UV-ozone treatment or plasma treatment can also be performed on the lower electrode 2 and the upper electrode 4.

[0070] According to the photoelectric conversion element 10A, near-infrared light incident through the support substrate 1 and the lower electrode 2 is photoelectricly converted in the photoelectric conversion layer 3. The holes in the resulting electron-hole pairs are concentrated at the lower electrode 2, and the electrons are concentrated at the upper electrode 4. Thus, for example, by measuring the potential of the lower electrode 2, the near-infrared light incident on the photoelectric conversion element 10A can be detected.

[0071] In this embodiment, the photoelectric conversion element 10A has a hole blocking layer 6 between the photoelectric conversion layer 3 and the electrode (see reference). Figure 2It can also be further equipped with an electron blocking layer 5 that, together with the hole blocking layer 6, holds the photoelectric conversion layer 3 (see reference). Figure 2 By sandwiching the photoelectric conversion layer 3 between the electron blocking layer 5 and the hole blocking layer 6, it is possible to suppress the injection of electrons from the lower electrode 2 into the photoelectric conversion layer 3 and to suppress the injection of holes from the upper electrode 4 into the photoelectric conversion layer 3. This suppresses dark current. Furthermore, details regarding the electron blocking layer 5 and the hole blocking layer 6 will be described below, and therefore are omitted here.

[0072] Next, use Figure 2 The photoelectric conversion element of this embodiment will be described. Figure 2 This is a schematic cross-sectional view showing the photoelectric conversion element 10B of this embodiment.

[0073] It should be noted that, in Figure 2 In the photoelectric conversion element 10B shown, for the relationship with Figure 1 The same components of the photoelectric conversion element 10A shown are labeled with the same reference symbols.

[0074] like Figure 2 As shown, the photoelectric conversion element 10B of this embodiment includes: a first electrode, i.e., an upper electrode 4; a second electrode, i.e., a lower electrode 2; and a photoelectric conversion layer 3 sandwiched between the first electrode and the second electrode. Furthermore, the photoelectric conversion element 10B includes a hole blocking layer 6 disposed between the second electrode and the photoelectric conversion layer 3. More specifically, the photoelectric conversion element 10B includes: an electron blocking layer 5 disposed between the lower electrode 2 and the photoelectric conversion layer 3; and a hole blocking layer 6 disposed between the upper electrode 4 and the photoelectric conversion layer 3. Furthermore, the method for forming the photoelectric conversion layer 3, etc., is omitted here as described above in the description of the photoelectric conversion element 10A.

[0075] The photoelectric conversion layer 3 is a bulk heterolayer made of a mixed film containing donor organic semiconductor materials and acceptor organic semiconductor materials. In the bulk heterolayer constituting the photoelectric conversion layer 3, due to the contact between the donor and acceptor organic semiconductor materials, electron excitation is induced from the donor organic semiconductor material to the acceptor organic semiconductor material, potentially generating charge even in the dark. Therefore, by reducing the contact between the donor and acceptor organic semiconductor materials, dark current can be suppressed. Furthermore, from the viewpoint of charge mobility, when the bulk heterolayer contains a large amount of acceptor organic semiconductor materials such as fullerene derivatives, the element resistance can be suppressed.

[0076] The photoelectric conversion layer 3 has an absorption wavelength in the near-infrared region. Specifically, the absorption end of the absorption spectrum of the photoelectric conversion layer 3 exists in the near-infrared region. Therefore, the photoelectric conversion element 10B equipped with the photoelectric conversion layer 3 has spectral sensitivity in the near-infrared region. That is, as described above, the external quantum efficiency, an indicator of the spectral sensitivity of the photoelectric conversion element 10B, is 1% or more, or 10% or more, and further, 20% or more at any wavelength in the near-infrared region. In addition, the photoelectric conversion layer 3 may also have a maximum absorption wavelength in the near-infrared region. The photoelectric conversion layer 3 uses a material with an absorption wavelength in the near-infrared region as the donor organic semiconductor material described later.

[0077] The following provides specific examples of donor organic semiconductor materials and acceptor organic semiconductor materials.

[0078] Donor organic semiconductor materials are primarily represented by hole-transporting organic compounds, which are organic compounds that readily donate electrons. More specifically, donor organic semiconductor materials are organic compounds with low ionization potential when used in contact with other organic materials. Therefore, any organic compound can be used as a donor organic semiconductor material, provided it has an absorption wavelength in the near-infrared region and possesses electron-donating properties. Examples include triarylamine compounds, benzidine compounds, pyrazoline compounds, styreneamine compounds, hydrazone compounds, triphenylmethane compounds, carbazole compounds, polysilane compounds, thiophene compounds, phthalocyanine compounds, naphthylphthalocyanine compounds, anthocyanin compounds, oxacyanine compounds, polyamine compounds, indole compounds, pyrrole compounds, pyrazole compounds, polyaryl compounds, fused aromatic carbocyclic compounds (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetraphenylene derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives), and metal complexes with nitrogen-containing heterocyclic compounds as ligands. Furthermore, not limited to this, as mentioned above, any organic compound with a smaller ionization potential compared to the organic compounds used as acceptor organic semiconductor materials can be used as donor organic semiconductor materials.

[0079] Acceptor organic semiconductor materials are primarily represented by electron-transporting organic compounds, which are organic compounds that readily accept electrons. More specifically, acceptor organic semiconductor materials are organic compounds with a high electron affinity when used in contact with two other organic compounds. Therefore, any organic compound can be used as an acceptor organic compound, as long as it possesses electron-accepting properties. Examples include fullerenes, fullerene derivatives, fused aromatic carbocyclic compounds (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetraphenylbenzene derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives), and 5- to 7-membered heterocyclic compounds containing nitrogen, oxygen, and sulfur atoms (e.g., pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxaline, quinazoline, phthalazine, cinnamon, isoquinoline, pteridine, acridine, phenazine, phenanthrene, tetrazolium). This includes compounds such as pyrazole, imidazole, thiazole, oxazole, indazole, benzimidazole, benzotriazole, benzoxazole, benzothiazole, carbazole, purine, triazolidinedion, triazolylpyrimidine, tetrazalindene, oxadiazole, imidazolepyridine, pyrazolidine, pyrrolopyridine, thiadiazopyridine, diphenylazepam, triphenylazepam, etc.), polyarylene compounds, fluorene compounds, cyclopentadiene compounds, silyl compounds, and metal complexes with nitrogen-containing heterocyclic compounds as ligands. Furthermore, not limited to these, as mentioned above, any organic compound with a higher electron affinity than the organic compound used as a donor organic semiconductor material can be used as an acceptor organic semiconductor material.

[0080] Furthermore, in the photoelectric conversion element 10B of this embodiment, the acceptor organic semiconductor material preferably includes at least one selected from fullerenes and fullerene derivatives. This allows the photoelectric conversion element 10B of this embodiment to achieve higher photoelectric conversion efficiency because electron movement between the donor and acceptor organic semiconductor materials proceeds smoothly. Additionally, the acceptor organic semiconductor material preferably includes a soluble fullerene. Therefore, it can be manufactured using a printing process.

[0081] Figure 3 It means possessing Figure 2 The diagram shows an example of the schematic performance characteristics of the photoelectric conversion element 10B as shown.

[0082] In the photoelectric conversion element 10B, the ionization potential of the electron blocking layer 5 is greater than that of the donor organic semiconductor material 3A contained in the photoelectric conversion layer 3. In the photoelectric conversion element 10B, the electron affinity of the hole blocking layer 6 is smaller than that of the acceptor organic semiconductor material 3B contained in the photoelectric conversion layer 3.

[0083] The electron blocking layer 5 is provided to reduce dark current caused by electron injection from the lower electrode 2, and to suppress the injection of electrons from the lower electrode 2 into the photoelectric conversion layer 3. The material of the electron blocking layer 5 can also be an organic compound used in the donor organic semiconductor material or a hole-transporting organic compound. To suppress the injection of electrons from the lower electrode 2 into the photoelectric conversion layer 3, the material of the electron blocking layer 5 must have an electron affinity that is at least lower than the work function of the lower electrode 2 and the electron affinity of the acceptor organic semiconductor material 3B of the photoelectric conversion layer 3.

[0084] like Figure 3 As shown, the electron blocking layer 5 has a larger ionization potential and a smaller electron affinity than the donor organic semiconductor material 3A of the photoelectric conversion layer 3.

[0085] The hole blocking layer 6 is provided to reduce dark current caused by holes injected from the upper electrode 4. To suppress the injection of holes from the upper electrode 4 into the photoelectric conversion layer 3, the material of the hole blocking layer 6 has an ionization potential that is at least greater than the work function of the upper electrode 4 and the ionization potential of the donor organic semiconductor material 3A of the photoelectric conversion layer 3. Furthermore, Figure 3 In this process, the ionization potential of the hole blocking layer 6 is less than the ionization potential of the acceptor semiconductor material 3B of the photoelectric conversion layer 3, but it is not limited to this and can also be greater than the ionization potential of the acceptor semiconductor material 3B of the photoelectric conversion layer 3.

[0086] Furthermore, in order to suppress the increase in dark current caused by the generation of charges (holes) at the interface between the photoelectric conversion layer 3 and the hole blocking layer 6, the energy difference between the ionization potential of the donor organic semiconductor material 3A of the photoelectric conversion layer 3 and the electron affinity of the hole blocking layer 6 is increased. In particular, by making the electron affinity of the hole blocking layer 6 greater than the electron affinity of the acceptor organic semiconductor material 3B of the photoelectric conversion layer 3, a greater dark current suppression effect can be obtained.

[0087] Furthermore, the ionization potential of the photoconversion layer 3 is 5.3 eV or less. In this case, when the ionization potential of the photoconversion layer 3 is relatively small, the dark current suppression effect brought about by the hole blocking layer 6 in this embodiment becomes significant. In the case of the photoconversion layer 3 made of a mixed film comprising a donor organic semiconductor material and an acceptor organic semiconductor material, the ionization potential of the donor semiconductor material is smaller than that of the acceptor semiconductor material. Therefore, the ionization potential of the photoconversion layer 3 is the ionization potential of the donor organic semiconductor material in the photoconversion layer 3.

[0088] Furthermore, to avoid hindering the light absorption of the photoelectric conversion layer 3, the hole blocking layer 6 can also improve the near-infrared light transmittance. Alternatively, a material that does not absorb in the visible light region can be selected as the material for the hole blocking layer 6, and the thickness of the hole blocking layer 6 can be reduced. The thickness of the hole blocking layer 6 depends on the composition of the photoelectric conversion layer 3, the thickness of the upper electrode 4, etc., and can be, for example, 2nm to 50nm. For the material of the hole blocking layer 6, organic compounds used in the aforementioned acceptor organic semiconductor materials or electron transport organic compounds can also be used.

[0089] In addition, such as Figure 3 As shown, the photoelectric conversion element 10B has a single hole blocking layer 6, but it may also have multiple hole blocking layers. When multiple hole blocking layers are present, it is sufficient that the electron affinity of the hole blocking layer adjacent to the photoelectric conversion layer is less than the electron affinity of the acceptor organic semiconductor material of the photoelectric conversion layer.

[0090] When the electron blocking layer 5 is provided, the material for the lower electrode 2 is selected from the aforementioned materials, taking into account factors such as adhesion to the electron blocking layer 5, electron affinity, ionization potential, and stability. The same applies to the upper electrode 4.

[0091] As described above, the photoelectric conversion element 10B of this embodiment, by using the aforementioned photoelectric conversion material, exhibits light absorption characteristics in the near-infrared region and reduces dark current. Therefore, according to this embodiment, a photoelectric conversion element such as an imaging element capable of detecting near-infrared light can be realized.

[0092] [Camera device]

[0093] The imaging device in this embodiment will be described below with reference to the accompanying drawings. The imaging device in this embodiment is, for example, a charge readout imaging device.

[0094] Use of the camera device in this embodiment Figure 4 and Figure 5 Please provide an explanation. Figure 4 This is a diagram illustrating an example of the circuit configuration of the camera device 100 according to this embodiment. Figure 5 This is a schematic cross-sectional view showing an example of the device structure of pixel 24 in the camera device 100 of this embodiment.

[0095] The imaging device 100 of this embodiment includes a semiconductor substrate 40 as a substrate and a pixel 24. The pixel 24 includes: a charge detection circuit 35 disposed on the semiconductor substrate 40; a photoelectric conversion unit 10C disposed on the semiconductor substrate 40; and a charge accumulation node 34 electrically connected to the charge detection circuit 35 and the photoelectric conversion unit 10C. The photoelectric conversion unit 10C of the pixel 24 includes the aforementioned photoelectric conversion element 10B. The charge accumulation node 34 accumulates the charge obtained by the photoelectric conversion unit 10C, and the charge detection circuit 35 detects the charge accumulated in the charge accumulation node 34. Furthermore, the charge detection circuit 35 disposed on the semiconductor substrate 40 may be disposed on the semiconductor substrate 40 or directly disposed in the semiconductor substrate 40.

[0096] like Figure 4 As shown, the camera device 100 includes a plurality of pixels 24 and peripheral circuitry. The camera device 100 is an organic image sensor implemented by a single-chip integrated circuit, having a pixel array comprising a plurality of pixels 24 arranged in two dimensions.

[0097] Multiple pixels 24 are arranged two-dimensionally, i.e., along the row and column directions, on the semiconductor substrate 40 to form a photosensitive area that serves as a pixel region. Figure 4 In the image, pixel 24 shows an example of a 2x2 matrix arrangement. It should be noted that... Figure 4 For ease of illustration, the diagram of the circuitry (e.g., pixel electrode control circuitry) used to individually set the sensitivity of each pixel 24 is omitted. Additionally, the imaging device 100 may also be a linear sensor. In this case, the multiple pixels 24 can be arranged in one dimension. Furthermore, in this specification, the terms "row direction" and "column direction" refer to the directions in which rows and columns extend, respectively. That is, the vertical direction is the column direction, and the horizontal direction is the row direction.

[0098] like Figure 4 and Figure 5 As shown, each pixel 24 includes a photoelectric conversion unit 10C and a charge accumulation node 34 electrically connected to a charge detection circuit 35. The charge detection circuit 35 includes an amplifying transistor 21, a reset transistor 22, and an addressing transistor 23.

[0099] The photoelectric conversion unit 10C includes a lower electrode 2, which is provided as a pixel electrode, and an upper electrode 4, which is provided as a counter electrode. The photoelectric conversion unit 10C includes the aforementioned photoelectric conversion element 10B. A predetermined bias voltage is applied to the upper electrode 4 via the counter electrode signal line 26.

[0100] The lower electrode 2 is connected to the gate electrode 21G of the amplifying transistor 21. The signal charge collected by the lower electrode 2 is stored in the charge storage node 34 located between the lower electrode 2 and the gate electrode 21G of the amplifying transistor 21. In this embodiment, the signal charge is a hole, but the signal charge can also be an electron.

[0101] The signal charge accumulated at charge accumulation node 34 is applied as a voltage corresponding to the amount of signal charge to the gate electrode 21G of amplifying transistor 21. Amplifying transistor 21 amplifies this voltage, which is then selectively read out as a signal voltage via addressing transistor 23. The source / drain electrodes of reset transistor 22 are connected to the lower electrode 2, resetting the signal charge accumulated at charge accumulation node 34. In other words, reset transistor 22 resets the potentials of the gate electrode 21G and the lower electrode 2 of amplifying transistor 21.

[0102] To selectively perform the aforementioned operations on multiple pixels 24, the imaging device 100 includes a power supply line 31, a vertical signal line 27, an addressing signal line 36, and a reset signal line 37, which are connected to each pixel 24 respectively. Specifically, the power supply line 31 is connected to the source / drain electrodes of the amplifying transistor 21, and the vertical signal line 27 is connected to the source / drain electrodes of the addressing transistor 23. The addressing signal line 36 is connected to the gate electrode 23G of the addressing transistor 23. Furthermore, the reset signal line 37 is connected to the gate electrode 22G of the reset transistor 22.

[0103] The peripheral circuitry includes a vertical scanning circuit 25, a horizontal signal readout circuit 20, multiple column signal processing circuits 29, multiple load circuits 28, and multiple differential amplifiers 32. The vertical scanning circuit 25 is also referred to as a row scanning circuit. The horizontal signal readout circuit 20 is also referred to as a column scanning circuit. The column signal processing circuit 29 is also referred to as a row signal accumulation circuit. The differential amplifiers 32 are also referred to as feedback amplifiers.

[0104] The vertical scanning circuit 25 is connected to the addressing signal line 36 and the reset signal line 37, selecting multiple pixels 24 arranged in each row in row units to read out the signal voltage and reset the potential of the lower electrode 2. The power supply wiring 31, serving as the source follower power supply, supplies a predetermined power voltage to each pixel 24. The horizontal signal readout circuit 20 is electrically connected to multiple column signal processing circuits 29. The column signal processing circuits 29 are electrically connected to the pixels 24 arranged in each column via vertical signal lines 27 corresponding to each column. The load circuit 28 is electrically connected to each vertical signal line 27. The load circuit 28 and the amplifying transistor 21 form a source follower circuit.

[0105] Multiple differential amplifiers 32 are arranged corresponding to each column. The negative input terminal of the differential amplifier 32 is connected to the corresponding vertical signal line 27. In addition, the output terminal of the differential amplifier 32 is connected to the pixel 24 via the feedback line 33 corresponding to each column.

[0106] The vertical scan circuit 25 applies a row selection signal to the gate electrode 23G of the addressing transistor 23 via the address signal line 36, controlling the on and off states of the addressing transistor 23. This scans and selects the row to be read. A signal voltage is read from the pixel 24 of the selected row to the vertical signal line 27. Additionally, the vertical scan circuit 25 applies a reset signal to the gate electrode 22G of the reset transistor 22 via the reset signal line 37, controlling the on and off states of the reset transistor 22. This selects the row containing the pixel 24 to be reset. The vertical signal line 27 transmits the signal voltage read from the pixel 24 selected by the vertical scan circuit 25 to the column signal processing circuit 29.

[0107] The signal processing circuit 29 performs noise suppression signal processing, such as correlated double sampling, and analog-to-digital conversion (AD conversion).

[0108] The horizontal signal readout circuit 20 reads signals sequentially from multiple column signal processing circuits 29 to the horizontal common signal line (not shown).

[0109] The differential amplifier 32 is connected to the drain electrode of the reset transistor 22 via feedback line 33. Therefore, when both the address transistor 23 and the reset transistor 22 are in the ON state, the differential amplifier 32 receives the output value of the address transistor 23 at its negative terminal. The differential amplifier 32 performs feedback operation according to the specified feedback voltage, where the gate potential of the amplifying transistor 21 becomes the feedback voltage. At this time, the output voltage of the differential amplifier 32 is 0V or a positive voltage near 0V. The feedback voltage refers to the output voltage of the differential amplifier 32.

[0110] like Figure 5 As shown, pixel 24 includes a semiconductor substrate 40, a charge detection circuit 35, a photoelectric conversion unit 10C, and a charge accumulation node 34 (see reference). Figure 4 ).

[0111] The semiconductor substrate 40 may also be an insulating substrate, such as a p-type silicon substrate, on the surface where a semiconductor layer is formed on the side where the photosensitive area is formed. The semiconductor substrate 40 has: impurity regions (here, n-type regions) 21D, 21S, 22D, 22S, and 23S; and a component separation region 41 for electrical separation between pixels 24. Here, the component separation region 41 is also provided between impurity regions 21D and 22D. This suppresses leakage of signal charge accumulated in the charge accumulation node 34. Furthermore, the component separation region 41 is formed, for example, by ion implantation of a acceptor under specified implantation conditions.

[0112] Impurity regions 21D, 21S, 22D, 22S, and 23S are typically diffusion layers formed within the semiconductor substrate 40. For example... Figure 5 As shown, the amplifying transistor 21 includes impurity regions 21S and 21D and a gate electrode 21G. Impurity regions 21S and 21D function as, for example, the source and drain regions of the amplifying transistor 21, respectively. A channel region of the amplifying transistor 21 is formed between the impurity regions 21S and 21D.

[0113] Similarly, the addressing transistor 23 includes impurity regions 23S and 21S and a gate electrode 23G connected to the address signal line 36. In this example, the amplifying transistor 21 and the addressing transistor 23 are electrically connected to each other through a shared impurity region 21S. The impurity region 23S functions as, for example, the source region of the addressing transistor 23. The impurity region 23S has a similar characteristic to... Figure 4 The connection of the vertical signal line 27 shown.

[0114] The reset transistor 22 includes impurity regions 22D and 22S and a gate electrode 22G connected to the reset signal line 37. The impurity region 22S functions as, for example, the source region of the reset transistor 22. The impurity region 22S has a similar characteristic to... Figure 4 The connection of the reset signal line 37 shown.

[0115] An interlayer insulating layer 50 is stacked on the semiconductor substrate 40 in such a way that it covers the amplification transistor 21, the addressing transistor 23 and the reset transistor 22.

[0116] Additionally, a wiring layer (not shown) may be configured in the interlayer insulating layer 50. The wiring layer is typically formed of a metal such as copper, and for example, a portion of it may contain wiring such as the aforementioned vertical signal line 27. The number of insulating layers in the interlayer insulating layer 50 and the number of layers contained in the wiring layer configured in the interlayer insulating layer 50 can be arbitrarily set.

[0117] The interlayer insulating layer 50 includes: a contact plug 54 connected to the impurity region 22D of the reset transistor 22; a contact plug 53 connected to the gate electrode 21G of the amplifying transistor 21; a contact plug 51 connected to the lower electrode 2; and wiring 52 connecting the contact plugs 51, 54, and 53. Thus, the impurity region 22D of the reset transistor 22 is electrically connected to the gate electrode 21G of the amplifying transistor 21.

[0118] The charge detection circuit 35 detects the signal charge captured by the lower electrode 2 and outputs a signal voltage. The charge detection circuit 35 includes an amplifying transistor 21, a reset transistor 22, and an addressing transistor 23, and is formed on the semiconductor substrate 40.

[0119] The amplifying transistor 21 is formed in the semiconductor substrate 40 and includes: an impurity region 21D and an impurity region 21S that function as a drain electrode and a source electrode, respectively; a gate insulating layer 21X formed on the semiconductor substrate 40; and a gate electrode 21G formed on the gate insulating layer 21X.

[0120] The reset transistor 22 is formed in the semiconductor substrate 40 and includes: an impurity region 22D and an impurity region 22S that function as a drain electrode and a source electrode, respectively; a gate insulating layer 22X formed on the semiconductor substrate 40; and a gate electrode 22G formed on the gate insulating layer 22X.

[0121] Addressing transistor 23 is formed within semiconductor substrate 40 and includes: impurity regions 21S and 23S that function as drain and source electrodes, respectively; a gate insulating layer 23X formed on semiconductor substrate 40; and a gate electrode 23G formed on gate insulating layer 23X. Impurity region 21S is shared by amplifying transistor 21 and addressing transistor 23, thereby amplifying transistor 21 and addressing transistor 23 are connected in series.

[0122] The photoelectric conversion unit 10C described above is disposed on the interlayer insulating layer 50. In other words, in this embodiment, a plurality of pixels 24 constituting a pixel array are formed on the semiconductor substrate 40. Moreover, the plurality of pixels 24 arranged two-dimensionally on the semiconductor substrate 40 form a photosensitive area. The distance between two adjacent pixels 24 (pixel pitch) can be, for example, about 2 μm.

[0123] The photoelectric conversion unit 10C has the structure of the photoelectric conversion element 10B described above.

[0124] A color filter 60 is formed above the photoelectric conversion unit 10C, and a microlens 61 is formed above it. The color filter 60 is formed, for example, using a patterned on-chip color filter, and employing a photosensitive resin in which dyes or pigments are dispersed. The microlens 61 is formed, for example, using an on-chip microlens, and employing an ultraviolet photosensitive material.

[0125] The camera device 100 can be manufactured using conventional semiconductor manufacturing processes. In particular, when a silicon substrate is used as the semiconductor substrate 40, it can be manufactured using various silicon semiconductor processes.

[0126] In summary, according to this embodiment, a photoelectric conversion element and imaging device that have high light absorption characteristics in the near-infrared region and exhibit low dark current can be obtained.

[0127] Example

[0128] The photoelectric conversion element of this application will be specifically described below through embodiments, but this application is not limited to the following embodiments only. In detail, various samples of the embodiments of this application were prepared, and the absorption end, ionization potential, electron affinity, and dark current were measured.

[0129] Hereinafter, phenyl will sometimes be represented as Ph, C4H9 as Bu, and C6H... 13 Represented as Hex, C 48 H 26 N8 is represented as Nc.

[0130] (Measurement of the absorption end and ionization potential of the photoelectric conversion layer)

[0131] The following examples, namely Example 1, Example 2, and Comparative Example 1, provide a detailed description of the absorption end and ionization potential of the photoelectric conversion layer of this application.

[0132] (Example 1)

[0133] <Sample Making>

[0134] A 0.7 mm thick quartz glass substrate is used as the support substrate. On it, as a photoelectric conversion layer, a donor organic semiconductor material PCPDTBT (manufactured by MERCK / Sigma-Aldrich, structural formula (1) below) and an acceptor organic semiconductor material phenyl C are coated by spin coating. 61A mixed solution of methyl butyrate (PCBM: ([6,6]-phenyl-C61-methyl butyrate, manufactured by Frontier Carbon Corporation), with the following structural formula (2)) was used to form a mixed film. The weight ratio of PCPDTBT to PCBM in the mixed solution was 1:3, and the solvent was chlorobenzene. The concentrations of PCPDTBT and PCBM in the mixed solution were 30 mg / ml. Furthermore, the thickness of the mixed film obtained at this time was approximately 150 nm.

[0135] [Chemical Formula 1]

[0136]

[0137] [Chemical Formula 2]

[0138]

[0139] <Determination of the absorption end>

[0140] The absorption spectrum of the photoelectric conversion layer formed on the quartz substrate was measured using a spectrophotometer (Hitachi High-Technologies Corporation, U4100). The obtained absorption spectra are shown below. Figure 6 In Example 1, the photoelectric conversion layer exhibited a peak of maximum absorption near 715 nm. The absorption endpoint was estimated based on the position of the rise on the longer wavelength side of the absorption spectrum. Furthermore, in this example, the intersection of the tangent extending from the point where the slope of the rise on the longer wavelength side of the absorption spectrum becomes the largest and the wavelength axis (where absorbance is zero) was defined as the absorption endpoint. The obtained measurement results are shown in Table 1.

[0141] <Determination of Ionization Potential>

[0142] The same photoelectric conversion layer as described in the <Sample Fabrication> was formed on an ITO substrate, and the ionization potential was measured. An atmospheric photoelectron spectrometer (AC-3, Riken Keiki) was used to measure the ionization potential. The ionization potential was measured by detecting the number of photoelectrons when the energy of ultraviolet radiation changes. Therefore, the energy position at which photoelectron detection begins can be set as the ionization potential. The obtained measurement results are shown in Table 1.

[0143] (Example 2)

[0144] As the donor organic semiconductor material, (OBu)8Si(OPOPh-3,5bisCF3)2Nc (synthesized based on the applicant's unpublished patent application, Japanese Patent Application 2018-215957) was used instead of PCPDTBT. Otherwise, the same procedures as in Example 1 were performed, including sample preparation, absorption end measurement, and ionization potential measurement. Furthermore, the thickness of the mixed film obtained at this time was approximately 230 nm.

[0145] [Chemical Formula 3]

[0146]

[0147] The obtained absorption spectrum is shown in Figure 7 In Example 2, the photoelectric conversion layer showed a peak of maximum absorption near 950 nm. Furthermore, the results of the absorption end and ionization potential measurements are shown in Table 1.

[0148] (Comparative Example 1)

[0149] As the donor organic semiconductor material, Si(OSiHex3)2Nc (manufactured by MERCK / Sigma-Aldrich) as shown in the following structural formula (4) was used instead of PCPDTBT. Otherwise, the same procedures as in Example 1 were performed, including sample preparation, absorption end measurement, and ionization potential measurement. Furthermore, the thickness of the hybrid film obtained at this time was approximately 180 nm.

[0150] [Chemical Formula 4]

[0151]

[0152] The obtained absorption spectrum is shown in Figure 8 In Comparative Example 1, the photoelectric conversion layer showed a peak of maximum absorption near 790 nm. Furthermore, the results of measurements of the absorption end and ionization potential are shown in Table 1.

[0153] [Table 1]

[0154]

[0155] As shown in Table 1, the photoelectric conversion layers of Examples 1, 2, and Comparative Example 1 all have near-infrared light absorption ends, thus confirming spectral sensitivity in the near-infrared light region. Furthermore, the ionization potentials of the photoelectric conversion layers of Examples 1, 2, and Comparative Example 1 are 5.1 eV, 5.3 eV, and 5.4 eV, respectively.

[0156] (Determination of ionization potential and electron affinity of acceptor organic semiconductor materials and hole blocking layers)

[0157] The following examples, namely Examples 3 and 4, Comparative Examples 2, 3 and 4, specifically illustrate the ionization potential and electron affinity of the acceptor organic semiconductor material of the photoelectric conversion layer and the hole blocking layer of this application. The ionization potential and electron affinity of the acceptor organic semiconductor material and the hole blocking layer were measured using a single film.

[0158] (Example 3)

[0159] <Sample Preparation Method>

[0160] A 0.7 mm thick quartz glass substrate is used as the support substrate. On this substrate, a phenyl C4000 styrene organic semiconductor material, which serves as the photoelectric conversion layer, is spin-coated. 61 An organic material film was formed by preparing a solution of methyl butyrate (PCBM: ([6,6]-phenyl-C61-methyl butyrate, manufactured by Frontier Carbon Corporation), structural formula (2) above) (solvent: chlorobenzene, 10 ml / ml). The thickness of the organic material film obtained at this time was approximately 30 nm.

[0161] <Determination of the absorption end>

[0162] For the organic material thin film formed on the quartz substrate, the absorption spectrum was measured using a spectrophotometer (Hitachi High-Technologies Corporation, U4100) in the same manner as in Example 1, and the absorption end was estimated.

[0163] <Determination of Ionization Potential>

[0164] An organic material thin film, identical to that used in the <Sample Fabrication>, was formed on an ITO substrate, and its ionization potential was measured. The ionization potential was measured using the same method as in Example 1, except that the organic material thin film described above was used. The results of the obtained ionization potentials are shown in Table 2.

[0165] <Determination of Electron Affinity>

[0166] The optical band gap was calculated from the absorption end result obtained in the above-mentioned <Determination of Absorption End> using the difference between the ionization potential and the electron affinity. The electron affinity was estimated using the difference between the ionization potential result obtained in the above-mentioned <Determination of Ionization Potential> and the optical band gap. The obtained electron affinity results are shown in Table 2.

[0167] (Example 4)

[0168] Instead of PCBM, ClAlPc (manufactured by MERCK / Sigma-Aldrich) of the following structural formula (5) was used as the hole blocking layer to form a film by vacuum evaporation. Otherwise, the same procedures as in Example 3 were performed, including sample preparation, measurement of the absorption end, measurement of ionization potential, and measurement of electron affinity. Furthermore, the thickness of the organic material film obtained at this time was approximately 30 nm.

[0169] [Chemical Formula 5]

[0170]

[0171] The results of the obtained ionization potential and electron affinity are shown in Table 2.

[0172] (Comparative Example 2)

[0173] As a material, PTCBI (Tokyo Chemical Manufacturing Co., Ltd.) as shown in the following structural formula (6) was used instead of ClAlPc as a hole blocking layer. Otherwise, the same procedures as in Example 4 were performed, including sample preparation, absorption end measurement, ionization potential measurement, and electron affinity measurement. Furthermore, the thickness of the organic material film obtained at this time was approximately 30 nm.

[0174] [Chemical Formula 6]

[0175]

[0176] The results of the obtained ionization potential and electron affinity are shown in Table 2.

[0177] (Comparative Example 3)

[0178] As a material, PTCDI (Tokyo Chemical Manufacturing Co., Ltd.) with the following structural formula (7) as the hole blocking layer was used instead of ClAlPc. Otherwise, the same procedures as in Example 4 were performed, including sample preparation, measurement of the absorption end, measurement of ionization potential, and measurement of electron affinity. Furthermore, the thickness of the organic material film obtained at this time was approximately 25 nm.

[0179] [Chemical Formula 7]

[0180]

[0181] The results of the obtained ionization potential and electron affinity are shown in Table 2.

[0182] (Comparative Example 4)

[0183] As a material, C60 (fullerene, manufactured by Frontier Carbon Corporation) as shown in the following structural formula (8) was used instead of ClAlPc as a hole-blocking layer. Otherwise, the same procedures as in Example 4 were performed, including sample preparation, absorption end measurement, ionization potential measurement, and electron affinity measurement. Furthermore, the thickness of the organic material film obtained at this time was approximately 50 nm.

[0184] [Chemical Formula 8]

[0185]

[0186] The results of the obtained ionization potential and electron affinity are shown in Table 2.

[0187] [Table 2]

[0188]

[0189] As shown in Table 2, it was confirmed that the hole blocking layer formed by ClAlPc in Example 4 had a lower electron affinity than the acceptor organic semiconductor material in the photoelectric conversion layer formed by PCBM in Example 3, while the hole blocking layers in Comparative Examples 2-4 had a higher electron affinity than PCBM.

[0190] (Near-infrared photoelectric conversion element)

[0191] The near-infrared photoelectric conversion element of this application will be described in more detail below with reference to Examples 5, 6 and Comparative Examples 5 to 12.

[0192] (Example 5)

[0193] <Fabrication of Photoelectric Conversion Components>

[0194] A photoelectric conversion element sample was fabricated using the following steps. All sample fabrication was performed under a nitrogen atmosphere. First, a glass substrate with a thickness of 0.7 mm and an ITO film of 150 nm on one main surface was prepared as the lower electrode. On the lower electrode, an electron blocking layer was formed by spin-coating a solution of VNPB (N4,N4′-bis(naphthyl-1-yl)-N4,N4′-bis(4-vinylphenyl); biphenyl-4,4′-diamine, manufactured by LUMTEC) (solvent: o-xylene, 10 mg / ml). The substrate was then crosslinked by heating it to 200°C for 50 minutes using a hot plate to prevent melting. Next, as the photoelectric conversion layer, a mixed solution of PCPDTBT and PCBM (weight ratio 1:3, solvent: chlorobenzene, 30 mg / ml) was spin-coated as in Example 1 to form a mixed film. The thickness of the resulting mixed film was approximately 150 nm.

[0195] Furthermore, on the substrate on which the hybrid film is formed, a film of the same material as in Example 4, namely ClAlPc, is formed with a thickness of 30 nm by vacuum evaporation through a metal shadow mask as a hole blocking layer.

[0196] Subsequently, an 80 nm thick Al electrode was formed on the hole-blocking layer as the upper electrode, resulting in a photoelectric conversion element. The Al electrode has a thickness of 5.0 × 10⁻⁶ nm. -4 Vacuum degree below Pa, at evaporation rate Film formation is carried out.

[0197] Since the photoelectric conversion layer in Example 5 is formed of the same material as the photoelectric conversion layer in Example 1, the results of the ionization potential measured in Example 1 are shown in Table 3. Furthermore, since the hole blocking layer in Example 5 is formed of the same material as the hole blocking layer in Example 4, the results of the electron affinity measured in Example 4 are shown in Table 3.

[0198] <Comparative Fabrication of Photoelectric Conversion Components>

[0199] In the above-mentioned <Fabrication of Photoelectric Conversion Element>, except that a hole blocking layer is not formed, a photoelectric conversion element is fabricated using the same method as described above to obtain a comparative photoelectric conversion element.

[0200] Measurement of Dark Current

[0201] Dark currents were measured for both the obtained photoelectric conversion element and the comparative photoelectric conversion element. The measurements were performed using a B1500A semiconductor device parameter analyzer (manufactured by Keysight Technologies). More specifically, the dark current of the photoelectric conversion element was measured in a glove box under a nitrogen atmosphere at a voltage of 2.5V. From the results obtained, the ratio of the dark current value of the photoelectric conversion element with a hole blocking layer to the dark current value of the comparative photoelectric conversion element without a hole blocking layer was calculated using the following formula, i.e., the relative dark current.

[0202] Relative dark current = Dark current value of photoelectric conversion element / Dark current value of photoelectric conversion element used for comparison

[0203] The results of the relative dark currents are shown in Table 3.

[0204] <Determination of Spectral Sensitivity>

[0205] The spectral sensitivity of the obtained photoelectric conversion element was measured. Specifically, the photoelectric conversion element was introduced into a sealable measurement fixture in a glovebox under a nitrogen atmosphere, and the spectral sensitivity was measured using a long-wavelength corresponding spectral sensitivity measuring device (spectrometer, CEP-25RR) at a voltage condition of 2.5V. The results of the spectral sensitivity measurement are shown below. Figure 9 In the near-infrared region, the photoelectric conversion element in Example 5 exhibits spectral sensitivity because the rise in the long-wavelength side of the spectral sensitivity spectrum is around 900 nm. The external quantum efficiency at the maximum peak wavelength in the near-infrared region is shown in Table 3.

[0206] (Comparative Example 5)

[0207] As the hole blocking layer, PTCBI, the same material as in Comparative Example 2, was used instead of ClAlPc. Otherwise, the same procedures as in Example 5 were performed, including the fabrication of the photoelectric conversion element, the fabrication of the comparative photoelectric conversion element, the measurement of dark current, and the measurement of spectral sensitivity. The ionization potential of the obtained photoelectric conversion layer, the electron affinity of the hole blocking layer, the relative dark current, and the external quantum efficiency are shown in Table 3.

[0208] (Comparative Example 6)

[0209] As the hole blocking layer, PTCDI, the same material as in Comparative Example 3, was used instead of ClAlPc. Otherwise, the same procedures as in Example 5 were performed, including the fabrication of the photoelectric conversion element, the fabrication of the comparative photoelectric conversion element, the measurement of dark current, and the measurement of spectral sensitivity. The ionization potential of the obtained photoelectric conversion layer, the electron affinity of the hole blocking layer, the relative dark current, and the external quantum efficiency are shown in Table 3.

[0210] (Comparative Example 7)

[0211] As the hole blocking layer, C60, the same material as in Comparative Example 4, was used instead of ClAlPc. Otherwise, the same procedures as in Example 5 were performed, including the fabrication of the photoelectric conversion element, the fabrication of the comparative photoelectric conversion element, the measurement of dark current, and the measurement of spectral sensitivity. The ionization potential of the obtained photoelectric conversion layer, the electron affinity of the hole blocking layer, the relative dark current, and the external quantum efficiency are shown in Table 3.

[0212] (Example 6)

[0213] As the photoelectric conversion layer, the same material as in Example 2, namely a mixed solution of (OBu)8Si(OPOPh-3,5bisCF3)2Nc and PCBM, was used instead of the mixed solution of PCPDTBT and PCBM. Otherwise, the same procedures as in Example 5 were performed, including the fabrication of the photoelectric conversion element, the fabrication of the comparative photoelectric conversion element, the measurement of dark current, and the measurement of spectral sensitivity. The ionization potential of the obtained photoelectric conversion layer, the electron affinity of the hole blocking layer, the relative dark current, and the external quantum efficiency are shown in Table 3. Furthermore, the results of the obtained spectral sensitivity measurements are shown in… Figure 10 In the near-infrared region, the photoelectric conversion element in Example 6 exhibits spectral sensitivity because the long-wavelength side of the spectral sensitivity spectrum rises to around 1000 nm.

[0214] (Comparative Example 8)

[0215] As the hole blocking layer, C60, the same material as in Comparative Example 4, was used instead of ClAlPc. Otherwise, the same procedures as in Example 6 were performed, including the fabrication of the photoelectric conversion element, the fabrication of the comparative photoelectric conversion element, the measurement of dark current, and the measurement of spectral sensitivity. The ionization potential of the obtained photoelectric conversion layer, the electron affinity of the hole blocking layer, the relative dark current, and the external quantum efficiency are shown in Table 3.

[0216] (Comparative Example 9)

[0217] As the photoelectric conversion layer, a mixed solution of Si(OSiHex3)2Nc and PCBM, the same material as in Comparative Example 1, was used instead of the mixed solution of PCPDTBT and PCBM. Otherwise, the same procedures as in Example 5 were performed, including the fabrication of the photoelectric conversion element, the fabrication of the comparative photoelectric conversion element, the measurement of dark current, and the measurement of spectral sensitivity. The ionization potential of the obtained photoelectric conversion layer, the electron affinity of the hole blocking layer, the relative dark current, and the external quantum efficiency are shown in Table 3. The results of the obtained spectral sensitivity measurements are shown in... Figure 11In Comparative Example 9, the photoelectric conversion element exhibits spectral sensitivity in the near-infrared region because the long-wavelength side of the spectral sensitivity spectrum rises to around 850 nm.

[0218] (Comparative Example 10)

[0219] As the hole blocking layer, PTCBI, the same material as in Comparative Example 2, was used instead of ClAlPc. Otherwise, the same procedures as in Comparative Example 9 were performed, including the fabrication of a photoelectric conversion element, the fabrication of a comparative photoelectric conversion element, the measurement of dark current, and the measurement of spectral sensitivity. The ionization potential of the obtained photoelectric conversion layer, the electron affinity of the hole blocking layer, the relative dark current, and the external quantum efficiency are shown in Table 3.

[0220] (Comparative Example 11)

[0221] As the hole blocking layer, PTCDI, the same material as in Comparative Example 3, was used instead of ClAlPc. Otherwise, the same procedures as in Comparative Example 9 were performed, including the fabrication of a photoelectric conversion element, the fabrication of a comparative photoelectric conversion element, the measurement of dark current, and the measurement of spectral sensitivity. The ionization potential of the obtained photoelectric conversion layer, the electron affinity of the hole blocking layer, the relative dark current, and the external quantum efficiency are shown in Table 3.

[0222] (Comparative Example 12)

[0223] As the hole blocking layer, C60, the same material as in Comparative Example 4, was used instead of ClAlPc. Otherwise, the same procedures as in Comparative Example 9 were performed, including the fabrication of a photoelectric conversion element, the fabrication of a comparative photoelectric conversion element, the measurement of dark current, and the measurement of spectral sensitivity. The ionization potential of the obtained photoelectric conversion layer, the electron affinity of the hole blocking layer, the relative dark current, and the external quantum efficiency are shown in Table 3.

[0224] [Table 3]

[0225]

[0226] As shown in Table 3, it was confirmed that in Examples 5, 6, Comparative Examples 5-7, and Comparative Examples 9-12, when the relative dark current was less than 1, the dark current value did not change or decreased after introducing the hole blocking layer. In Comparative Example 8, the relative dark current was 1.7, and the dark current value increased after introducing the hole blocking layer.

[0227] Furthermore, the results of Comparative Examples 9-12 show that when using Si(OSiHex3)2Nc:PCBM with an ionization potential of 5.4 eV as the photoelectric conversion layer, the relative dark current is independent of the hole blocking layer material and remains around 1 regardless of the material used. That is, it is confirmed that even when the hole blocking layer used in Comparative Examples 9-12 is incorporated into the photoelectric conversion element with a photoelectric conversion layer having an ionization potential of 5.4 eV, the effect of reducing dark current is not obtained.

[0228] In contrast, a comparison between Example 5 and Comparative Examples 5-7, and between Example 6 and Comparative Example 8, revealed that when using (OBu)8Si(OPOPh-3,5bisCF3)2Nc:PCBM (5.3eV) and PCPDTBT:PCBM (5.1eV) with an ionization potential of 5.3eV or less for the photoelectric conversion layer, the relative dark current is smaller compared to the case where the electron affinity of the hole blocking layer is greater than that of the acceptor organic semiconductor material PCBM (4.3eV, see Example 3 in Table 2) (Comparative Examples 5-8). That is, it was confirmed that by introducing a hole blocking layer with an ionization potential of 5.3eV or less for the photoelectric conversion element, the effect of reducing dark current becomes even greater.

[0229] Industrial availability

[0230] The photoelectric conversion materials and photoelectric conversion elements of this application can be applied to image sensors, for example, to image sensors with high light absorption characteristics in the near-infrared region.

[0231] Explanation of symbols

[0232] 1. Support substrate

[0233] 2 Lower electrode

[0234] 3 Photoelectric conversion layer

[0235] 4. Upper electrode

[0236] 5 Electron blocking layer

[0237] 6. Cavity blocking layer

[0238] 10A and 10B photoelectric conversion elements

[0239] 10C Photoelectric Conversion Unit

[0240] 20 Horizontal Signal Readout Circuit

[0241] 21 Amplifying Transistors

[0242] 22 Reset transistor

[0243] 23 Addressing transistors

[0244] 21G, 22G, 23G gate electrodes

[0245] Impurity regions 21D, 21S, 22D, 22S, 23S

[0246] 21X, 22X, 23X gate insulating layers

[0247] 24 pixels

[0248] 25 Vertical Scanning Circuit

[0249] 26 Opposite electrode signal lines

[0250] 27 Vertical signal lines

[0251] 28 Load Circuit

[0252] 29 signal processing circuits

[0253] 31 Power Wiring

[0254] 32 Differential Amplifier

[0255] 33 Feedback Line

[0256] 34 Charge accumulation nodes

[0257] 35 Charge Detection Circuit

[0258] 36 Addressing signal lines

[0259] 37 Reset signal line

[0260] 40 Semiconductor substrate

[0261] 41 Component Separation Area

[0262] 50 interlayer insulation layers

[0263] 51, 53, 54 Contact plugs

[0264] 52 Wiring

[0265] 60 color filter

[0266] 61 Microlenses

[0267] 100 camera devices

Claims

1. A camera device comprising: Semiconductor substrates; a first electrode; a second electrode; a photoelectric conversion layer disposed between the first electrode and the second electrode and comprising a donor organic semiconductor material and an acceptor organic semiconductor material; and a charge storage node located in the semiconductor substrate and electrically connected to the second electrode; The first blocking layer as a hole blocking layer is arranged between the first electrode and the photoelectric conversion layer. in, The ionization potential of the photoelectric conversion layer is 5.3 eV or less, The electron affinity of the first blocking layer is smaller than the electron affinity of the acceptor organic semiconductor material contained in the photoelectric conversion layer. It has spectral sensitivity in the near-infrared region with a wavelength of 650nm to 3000nm.

2. The imaging device according to claim 1, wherein: The photoelectric conversion layer has an absorption wavelength maximum in the near-infrared light region.

3. The imaging device according to claim 1 or 2, wherein: The photoelectric conversion layer contains at least one selected from fullerene and fullerene derivatives as the acceptor organic semiconductor material.

4. The imaging device according to claim 3, wherein: The acceptor organic semiconductor material comprises a soluble fullerene derivative.

5. The imaging device according to claim 1 or 2, wherein: The acceptor organic semiconductor material is the same as the material of the first blocking layer.

6. The imaging device according to claim 1 or 2, wherein: The electron affinity of the first blocking layer is less than the work function of the first electrode.

7. The imaging device according to claim 1 or 2, wherein: The first blocking layer has an ionization potential lower than an ionization potential of the acceptor organic semiconductor material contained in the photoelectric conversion layer. 8 . The imaging device according to claim 1 , further comprising a second blocking layer provided between the second electrode and the photoelectric conversion layer.

9. The imaging device according to claim 8, wherein: The electron affinity of the second blocking layer is lower than the electron affinity of the donor organic semiconductor material contained in the photoelectric conversion layer.

10. The imaging device according to claim 8, wherein: The second blocking layer has an ionization potential greater than an ionization potential of the donor organic semiconductor material contained in the photoelectric conversion layer.

11. The imaging device according to claim 8, wherein: The electron affinity of the second blocking layer is less than the work function of the second electrode.

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