Imaging device

Abstract

This imaging device comprises: a semiconductor substrate; a plurality of pixel electrodes located above the semiconductor substrate, each being electrically connected to the semiconductor substrate; a counter electrode located above the plurality of pixel electrodes; a first photoelectric conversion layer located between the plurality of pixel electrodes and the counter electrode; and at least one first light blocking body located within the first photoelectric conversion layer or above the first photoelectric conversion layer. The first photoelectric conversion layer comprises semiconductor quantum dots which absorb light of a first wavelength range, and a coating material which coats the semiconductor quantum dots, absorbs light of a second wavelength range, and emit fluorescence of a third wavelength range. The at least one first light blocking body absorbs or reflects light of at least some of the wavelengths in the second wavelength range.

Description

[Technical field]

[0001] The present disclosure relates to an imaging device. [Background technology]

[0002] Research is being actively conducted into imaging devices in which a photoelectric conversion section made of semiconductor quantum dots is stacked on a semiconductor substrate. Since semiconductor quantum dots have the characteristic that the energy gap changes due to the quantum size effect when the crystal size is changed, it is possible to realize an imaging device that has sensitivity to a desired wavelength range by controlling the material and crystal size of the semiconductor quantum dots used in the photoelectric conversion section. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 150971 [Non-patent literature]

[0004] [Non-Patent Document 1] Mengxia Liu et. al., “Lattice anchoring stabilizes solution-processed semiconductors”, Nature, 2019, Vol.570, p.96-101 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a demand for an imaging device with reduced noise, and the present disclosure provides an imaging device with reduced noise. [Means for solving the problem]

[0006] An imaging device according to an embodiment of the present disclosure includes a semiconductor substrate, a plurality of pixel electrodes located above the semiconductor substrate and each of which is electrically connected to the semiconductor substrate, a counter electrode located above the plurality of pixel electrodes, a first photoelectric conversion layer located between the plurality of pixel electrodes and the counter electrode, and at least one first light shielding body located in the first photoelectric conversion layer or above the first photoelectric conversion layer. The first photoelectric conversion layer includes semiconductor quantum dots having a property of absorbing light in a first wavelength range, and a coating material that covers the semiconductor quantum dots and has a property of absorbing light in a second wavelength range and emitting fluorescence in a third wavelength range. The at least one first light shielding body absorbs or reflects light of at least a part of the wavelengths in the second wavelength range.

[0007] An imaging device according to an embodiment of the present disclosure includes a semiconductor substrate, a plurality of pixel electrodes located above the semiconductor substrate and each of which is electrically connected to the semiconductor substrate, a counter electrode located above the plurality of pixel electrodes, a first photoelectric conversion layer located between the plurality of pixel electrodes and the counter electrode, and at least one second light shielding body located in the first photoelectric conversion layer or between the first photoelectric conversion layer and the plurality of pixel electrodes. The first photoelectric conversion layer includes semiconductor quantum dots having a property of absorbing light in a first wavelength range, and a coating material that covers the semiconductor quantum dots and has a property of absorbing light in a second wavelength range and emitting fluorescence in a third wavelength range. The at least one second light shielding body absorbs or reflects light of at least a part of the wavelengths in the third wavelength range. Effect of the Invention

[0008] It is possible to provide an imaging device with reduced noise. [Brief description of the drawings]

[0009] [Figure 1A] FIG. 1A is a schematic diagram showing an example of the morphology of a semiconductor quantum dot. [Figure 1B] FIG. 1B is a schematic diagram showing an example of the morphology of a semiconductor quantum dot. [Diagram 2]FIG. 2 shows the absorption and fluorescence spectra of a P3HT thin film. [Figure 3A] FIG. 3A shows the absorption and fluorescence spectra of a CsPbBr2I thin film. [Figure 3B] FIG. 3B shows the absorption and fluorescence spectra of the CsSnI3 thin film. [Figure 3C] FIG. 3C shows the absorption and fluorescence spectra of a CH3NH3SnI3 thin film. [Figure 4] FIG. 4 is a circuit diagram illustrating an exemplary circuit configuration of the imaging device according to the first embodiment. [Diagram 5] FIG. 5 is a schematic diagram showing a cross-sectional structure of a plurality of pixels of the imaging device according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing an example of the absorption spectrum of a semiconductor quantum dot. [Figure 7] FIG. 7 is a schematic diagram showing an example of an absorption spectrum of semiconductor quantum dots containing multiple types of semiconductor quantum dots. [Figure 8] FIG. 8 is a schematic diagram showing a cross-sectional structure of a plurality of pixels of an imaging device according to the second embodiment. [Figure 9] FIG. 9 shows the absorption spectra of C60, C70, BT-CIC and COi8DFIC thin films. [Figure 10] FIG. 10 is a diagram showing the simulation results of the light transmittance of C70 layers having different thicknesses. [Figure 11] FIG. 11 is a diagram showing the simulation results of the light transmittance of mixed layers of COi8DFIC and C70 having different thicknesses. [Figure 12] FIG. 12 is a schematic diagram showing a cross-sectional structure of a plurality of pixels of an imaging device according to the third embodiment. [Figure 13] FIG. 13 is a diagram showing the absorption spectrum of a mixed film of SnNcCl2 and C70. [Figure 14] FIG. 14 is a schematic diagram showing a cross-sectional structure of a plurality of pixels of an imaging device according to the fourth embodiment. [Figure 15]FIG. 15 is a schematic diagram showing a cross-sectional structure of a plurality of pixels of an imaging device according to the fifth embodiment. [Figure 16] FIG. 16 is a schematic diagram showing a cross-sectional structure of a plurality of pixels of an imaging device according to the sixth embodiment. [Figure 17] FIG. 17 is a schematic diagram showing a cross-sectional structure of a plurality of pixels of an imaging device according to the seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Findings that have led to one aspect of the present disclosure) Semiconductor quantum dots can be used as photoelectric conversion materials as they are. However, the semiconductor quantum dots immediately after synthesis are coated with ligands or the like to improve the dispersion stability in the solvent and suppress the formation of secondary particles. Figures 1A and 1B are schematic diagrams showing examples of the shape of semiconductor quantum dots. For example, in the semiconductor quantum dots immediately after synthesis, a surface modification group called a ligand 230 is adsorbed or bonded to the surface of a semiconductor quantum dot 200A having a two-layer structure of a core 210 and a shell 220 as shown in Figure 1A, or to the surface of a semiconductor quantum dot 200B having a single-layer structure of a core 210 as shown in Figure 1B. Usually, the ligand 230 that coats the semiconductor quantum dots immediately after synthesis is often a molecule having a long-chain alkyl group, such as oleic acid or oleylamine. A molecule having a long-chain alkyl group inhibits the electrical conductivity between semiconductor quantum dots. Therefore, the electrical conductivity between semiconductor quantum dots can be improved by ligand-exchanging a molecule having a long-chain alkyl group with a shorter organic molecule, a low molecule having a π-conjugated system, or a halogen atom.

[0011] When the semiconductor quantum dots thus ligand-exchanged are used in a photoelectric conversion layer, a dispersion liquid in which the semiconductor quantum dots are dispersed is applied to an electrode or the like. However, when a dispersion liquid in which only the semiconductor quantum dots are dispersed is applied to an electrode or the like, the semiconductor quantum dot thin film after drying is brittle and prone to cracking, making it difficult to form a homogeneous film. In this case, for example, a material softer than the semiconductor quantum dots, such as a semiconductor polymer or perovskite material, is mixed with the semiconductor quantum dots to form a semiconductor quantum dot thin film, thereby improving the film quality of the thin film after drying.

[0012] Patent Document 1 discloses a photoelectric conversion layer including semiconductor quantum dots in which the ligand modifying the surface of the semiconductor quantum dots is replaced with a conductive compound having a π-conjugated system such as an acene or a thiophene compound in order to improve the electrical conductivity between the semiconductor quantum dots, and the semiconductor quantum dots are mixed with a semiconductor polymer such as a thiophene-based polymer or 3-hexylthiophene (P3HT). However, when ligand exchange is performed with a conductive compound having a π-conjugated system, it is difficult to completely remove the conductive compound having an excess π-conjugated system that does not modify the surface of the semiconductor quantum dots. In addition, when mixing with a semiconductor polymer, not all of the mixed semiconductor polymer necessarily comes into contact with and covers the surface of the semiconductor quantum dots. Therefore, a thin film composed of semiconductor quantum dots that have been subjected to ligand exchange, a thin film in which a semiconductor polymer and a semiconductor quantum dot are mixed, or a thin film of a mixture obtained by combining these usually includes a ligand and a semiconductor polymer that are not in contact with the semiconductor quantum dots.

[0013] In addition, Non-Patent Document 1 discloses a solar cell using a structure in which semiconductor quantum dots are embedded in a perovskite material thin film by preparing a dispersion liquid in which lead sulfide (PbS) quantum dots, which are semiconductor quantum dots, and a precursor of a perovskite material having a lattice constant matching the lattice constant of the surface atoms are mixed, and then forming a film by a spin coating method. Here, at the contact interface between the perovskite material layer and the semiconductor quantum dots, an interface with suppressed structural defects is formed because the lattice spacing of the lead atoms matches the lattice spacing of the perovskite material layer, and as a result, good solar cell characteristics are obtained. In this way, even in a thin film of a mixture in which a perovskite material is used as a matrix material and semiconductor quantum dots are embedded therein, a matrix material that is not in contact with the semiconductor quantum dots is included.

[0014] The present inventor discovered the following problem in the course of researching an imaging device equipped with a photoelectric conversion layer containing semiconductor quantum dots. Many of the coating materials for coating semiconductor quantum dots, such as ligand materials and matrix materials such as semiconductor polymers and perovskite materials, suitable for improving electrical conductivity between semiconductor quantum dots, absorb light and emit fluorescence. The wavelength of the absorbed light varies depending on the type of coating material, but is in the range from ultraviolet light to near infrared light. In addition, the wavelength of the fluorescence emitted by the coating material varies depending on the type of material, but is often several tens of nm to about 100 nm longer than the wavelength of the absorbed light.

[0015] FIG. 2 shows the absorption spectrum and fluorescence spectrum of a thin film of P3HT, a semiconducting polymer, as an example of a matrix material. In FIG. 2, the absorption spectrum of the P3HT thin film is shown by a dotted line, and the fluorescence spectrum is shown by a solid line. In FIG. 2, the horizontal axis of both the absorption spectrum and the fluorescence spectrum is wavelength, the vertical axis of the absorption spectrum is absorbance, and the vertical axis of the fluorescence spectrum is fluorescence intensity. These are the same in FIG. 3A to FIG. 3C used in the following description.

[0016] As shown in FIG. 2, a thin film of P3HT, a type of semiconducting polymer, absorbs light in the wavelength range of about 400 nm to about 650 nm and emits fluorescence in the wavelength range of about 550 nm to about 750 nm.

[0017] 3A is a diagram showing the absorption spectrum and the fluorescence spectrum of a thin film of CsPbBr2I, which is a perovskite material as another example of a matrix material. As shown in FIG. 3A, the CsPbBr2I thin film absorbs light in the wavelength range of about 340 nm to about 600 nm and emits fluorescence in the wavelength range of about 560 nm to about 620 nm.

[0018] 3B is a diagram showing the absorption spectrum and the fluorescence spectrum of a CsSnI3 thin film, which is a perovskite material as yet another example of a matrix material. As shown in FIG. 3B, the CsSnI3 thin film absorbs light in the wavelength range of about 400 nm to about 950 nm and emits fluorescence in the wavelength range of about 850 nm to about 1000 nm.

[0019] 3C is a diagram showing the absorption spectrum and the fluorescence spectrum of a CH3NH3SnI3 thin film as yet another example of a matrix material. As shown in FIG. 3C, the CH3NH3SnI3 thin film absorbs light in the wavelength range of about 1050 nm or less and emits fluorescence in the wavelength range of about 800 nm to about 1100 nm.

[0020] In an imaging device, when light is irradiated onto the photoelectric conversion layer, the semiconductor quantum dots absorb the photons and convert them into charges, which are then taken out as signal charges. When the photoelectric conversion layer contains a matrix material such as a semiconductor polymer or a perovskite material, the matrix material in the photoelectric conversion layer also absorbs photons and emits fluorescence isotropically. As a result, the fluorescence emitted by the matrix material in the photoelectric conversion layer is also emitted in a direction different from the direction of the light irradiated onto the imaging device. Since the fluorescence emitted from this matrix material is isotropically emitted from within the photoelectric conversion layer, in the case of an imaging device in which a photoelectric conversion layer is provided above a semiconductor substrate, it can be irradiated onto the semiconductor layer that constitutes the charge storage region and control circuit of the imaging device. For example, in the case of single crystal silicon, which is most commonly used as a material for the charge storage region and control circuit, it absorbs light in the wavelength range of about 200 nm to about 1100 nm. Therefore, when a semiconductor substrate containing silicon is used, if fluorescence in this wavelength range is irradiated, the irradiated fluorescence may be absorbed in the charge storage region and control circuit of the semiconductor substrate. As shown in Figures 2, 3A, 3B, and 3C, the wavelengths of fluorescence emitted by typical semiconducting polymers and perovskite materials are almost within the wavelength range absorbed by the semiconductor layer. The same phenomenon can also occur when π-conjugated compounds such as acenes or thiophene compounds are used as ligand materials. Although it depends on the type of material, most of these π-conjugated compound ligand materials absorb light with wavelengths in the ultraviolet to visible light range and emit fluorescence with wavelengths several tens to 100 nm longer than that.

[0021] Furthermore, for example, single crystal gallium arsenide, which is often used as a material for charge storage regions and control circuits, absorbs light in the wavelength range of about 200 nm to about 800 nm. Therefore, even when a semiconductor substrate containing gallium arsenide is used, if fluorescence in this wavelength range is irradiated, the irradiated fluorescence may be absorbed in the charge storage region and control circuit of the semiconductor substrate.

[0022] When a photon of fluorescence is absorbed in the charge accumulation region, a charge is generated in the charge accumulation region. Such a charge generated by absorbing fluorescence cannot be distinguished from a charge generated by a semiconductor quantum dot in the photoelectric conversion layer absorbing an incident photon from the outside. A particular problem occurs when a photon of fluorescence generated from a ligand material or matrix material of a π-conjugated compound in the photoelectric conversion layer of a pixel is absorbed in the charge accumulation region of another pixel. In this case, a signal charge is generated in a position other than the position where the light was originally irradiated, which causes image bleeding, color mixing, noise, and the like. This problem occurs when light is emitted from the ligand material or matrix material of the π-conjugated compound in the photoelectric conversion layer in a direction different from the direction of the light irradiated to the imaging device. In addition, when the fluorescence emitted from the ligand material or matrix material of the π-conjugated compound in the photoelectric conversion layer is absorbed by the control circuit, it also causes a malfunction of the circuit and an increase in noise.

[0023] As described above, the present inventor has found that in the case of an imaging device having a photoelectric conversion layer above a semiconductor substrate, in which semiconductor quantum dots mixed with a ligand material or matrix material of a π-conjugated compound are used as a photoelectric conversion material, the fluorescence emitted by the ligand material or matrix material of a π-conjugated compound causes an increase in noise in the imaging device. Therefore, the present disclosure provides an imaging device with reduced noise even in the case of an imaging device having a photoelectric conversion layer above a semiconductor substrate, in which semiconductor quantum dots mixed with a coating material for semiconductor quantum dots, such as a ligand material or matrix material of a π-conjugated compound, are used as a photoelectric conversion material.

[0024] An outline of one aspect of the present disclosure is as follows.

[0025] An imaging device according to an embodiment of the present disclosure includes a semiconductor substrate, a plurality of pixel electrodes located above the semiconductor substrate and each of which is electrically connected to the semiconductor substrate, a counter electrode located above the plurality of pixel electrodes, a first photoelectric conversion layer located between the plurality of pixel electrodes and the counter electrode, and at least one first light shielding body located in the first photoelectric conversion layer or above the first photoelectric conversion layer. The first photoelectric conversion layer includes semiconductor quantum dots having a property of absorbing light in a first wavelength range, and a coating material that covers the semiconductor quantum dots and has a property of absorbing light in a second wavelength range and emitting fluorescence in a third wavelength range. The at least one first light shielding body absorbs or reflects light of at least a part of the wavelengths in the second wavelength range.

[0026] As a result, the first light shield is located in the first photoelectric conversion layer or above the first photoelectric conversion layer. Here, the first light shield is located above the first photoelectric conversion layer means that the first light shield is located above the first surface of the first photoelectric conversion layer, which is closer to the counter electrode than the plurality of pixel electrodes, among the first surface and the second surface opposite to the first surface. Also, the first light shield is located above the first photoelectric conversion layer means that the first light shield is located in a region opposite to the region where the semiconductor substrate is located, across the first photoelectric conversion layer, and in a region where light is incident on the first photoelectric conversion layer. Therefore, the first light shield absorbs or reflects the light in the second wavelength range before the light in the second wavelength range reaches the coating material. Therefore, the light in the second wavelength range absorbed by the coating material can be reduced, and as a result, the fluorescence emitted by the coating material can also be reduced. Therefore, the charge accumulation region or control circuit formed of an impurity region or the like of the semiconductor substrate is suppressed from absorbing the fluorescence emitted by the coating material and generating noise. In other words, the first light blocking body reduces light in the second wavelength range that reaches the coating material and causes noise in the imaging device, thereby achieving an imaging device with reduced noise.

[0027] Furthermore, for example, the at least one first light shield may be located above the counter electrode and may include an optical filter that absorbs or reflects the light having at least a portion of the wavelength in the second wavelength range.

[0028] As a result, the optical filter is located above the first photoelectric conversion layer, on the side where light enters the imaging device relative to the first photoelectric conversion layer. Therefore, the optical filter absorbs or reflects at least a portion of the light in the second wavelength range before it reaches the first photoelectric conversion layer. Therefore, the light in the second wavelength range that reaches the coating material can be efficiently reduced, and noise in the imaging device is reduced.

[0029] Also, for example, the at least one first light shielding body may be located between the first photoelectric conversion layer and the counter electrode and may include a first charge transport layer that absorbs the light of at least a portion of the wavelengths in the second wavelength range.

[0030] As a result, the first charge transport layer is located above the first photoelectric conversion layer, on the side where light enters the imaging device relative to the first photoelectric conversion layer. Therefore, the first charge transport layer absorbs at least a part of the light in the second wavelength range before it reaches the first photoelectric conversion layer. Therefore, the light in the second wavelength range that reaches the coating material can be efficiently reduced, and noise in the imaging device is reduced.

[0031] Also, for example, the at least one first light shield may include a second photoelectric conversion layer located between the first photoelectric conversion layer and the counter electrode and absorbing the light of at least a portion of the wavelengths in the second wavelength range.

[0032] As a result, the second photoelectric conversion layer is located above the first photoelectric conversion layer, on the side where light enters the imaging device relative to the first photoelectric conversion layer. Therefore, the second photoelectric conversion layer absorbs at least a part of the light in the second wavelength range before it reaches the first photoelectric conversion layer. Therefore, the light in the second wavelength range that reaches the coating material can be efficiently reduced, and the noise of the imaging device is reduced.

[0033] Also, for example, the at least one first light shielding body may include a first material different from the semiconductor quantum dots that absorbs the light of at least a portion of the wavelengths in the second wavelength range, and the first material may be located within the first photoelectric conversion layer.

[0034] As a result, the first material is located in the first photoelectric conversion layer, and the first material absorbs at least a portion of the light in the second wavelength range that is incident on the first photoelectric conversion layer, thereby reducing the amount of light in the second wavelength range that reaches the coating material, thereby reducing noise in the imaging device.

[0035] Furthermore, for example, the first light shield may transmit light having at least a portion of the wavelengths in the first wavelength range.

[0036] This allows light in the first wavelength range to easily reach the semiconductor quantum dots, thereby suppressing a decrease in the photoelectric conversion function in the first photoelectric conversion layer.

[0037] The at least one first light blocking body may absorb or reflect light having a wavelength of 1050 nm or less.

[0038] As a result, light in the wavelength range from near infrared to visible light is absorbed or reflected by the first light shielding body, and light in the wavelength range from near infrared to visible light is less likely to be absorbed by the coating material.

[0039] Furthermore, for example, the pixel may further include at least one second light shield located within the first photoelectric conversion layer or between the first photoelectric conversion layer and the plurality of pixel electrodes, and absorbing or reflecting light of at least a portion of the wavelengths in the third wavelength range.

[0040] As a result, the second light shield is located in the first photoelectric conversion layer or between the first photoelectric conversion layer and the plurality of pixel electrodes. Therefore, even if the covering material emits fluorescence in the third wavelength range, the second light shield absorbs or reflects the light in the third wavelength range. This makes it possible to reduce the light in the third wavelength range that reaches the charge accumulation region or the control circuit made of the impurity region of the semiconductor substrate. In other words, the first light shield reduces the light in the second wavelength range that reaches the covering material, and the second light shield reduces the light in the third wavelength range that reaches the charge accumulation region or the control circuit made of the impurity region of the semiconductor substrate, which causes noise in the imaging device. Thus, an imaging device with reduced noise is realized.

[0041] An imaging device according to an embodiment of the present disclosure includes a semiconductor substrate, a plurality of pixel electrodes located above the semiconductor substrate and each of which is electrically connected to the semiconductor substrate, a counter electrode located above the plurality of pixel electrodes, a first photoelectric conversion layer located between the plurality of pixel electrodes and the counter electrode, and at least one second light shielding body located in the first photoelectric conversion layer or between the first photoelectric conversion layer and the plurality of pixel electrodes. The first photoelectric conversion layer includes semiconductor quantum dots having a property of absorbing light in a first wavelength range, and a coating material that covers the semiconductor quantum dots and has a property of absorbing light in a second wavelength range and emitting fluorescence in a third wavelength range. The at least one second light shielding body absorbs or reflects light of at least a part of the wavelengths in the third wavelength range.

[0042] As a result, the second light shield is located in the first photoelectric conversion layer or between the first photoelectric conversion layer and the plurality of pixel electrodes. Therefore, even if the covering material emits fluorescence in the third wavelength range, the second light shield absorbs or reflects the light in the third wavelength range. This makes it possible to reduce the light in the third wavelength range that reaches the charge accumulation region or the control circuit formed of the impurity region of the semiconductor substrate. In other words, the second light shield reduces the light in the third wavelength range that reaches the charge accumulation region or the control circuit formed of the impurity region of the semiconductor substrate, which causes noise in the imaging device. Thus, an imaging device with reduced noise is realized.

[0043] Also, for example, the at least one second light shielding body may include a second material different from the semiconductor quantum dots that absorbs the light of at least a portion of the wavelengths in the third wavelength range, and the second material may be located within the first photoelectric conversion layer.

[0044] As a result, the second material is located in the first photoelectric conversion layer, and the second material absorbs at least a part of the fluorescence in the third wavelength range emitted by the coating material, thereby reducing the amount of light in the third wavelength range that reaches the charge accumulation region or the control circuit formed of the impurity region of the semiconductor substrate, and thus reducing noise in the imaging device.

[0045] Also, for example, the at least one second light shielding body may include a second charge transport layer located between the first photoelectric conversion layer and the multiple pixel electrodes and absorbing the light of at least a portion of the wavelengths in the third wavelength range.

[0046] As a result, the second charge transport layer is located closer to the semiconductor substrate than the first photoelectric conversion layer, which is the side of the pixel electrodes of the first photoelectric conversion layer. Therefore, the second charge transport layer absorbs at least a part of the light in the third wavelength range before it reaches the semiconductor substrate. Therefore, it is possible to reduce the light in the third wavelength range that reaches the charge accumulation region or the control circuit formed of the impurity region of the semiconductor substrate, and the noise of the imaging device is reduced.

[0047] For example, the coating material may include at least one selected from the group consisting of a matrix material and a ligand material having π-conjugation. The matrix material may include at least one selected from the group consisting of a semiconducting polymer, a semiconducting copolymer, a semiconducting oligomer, a small molecule semiconductor, a perovskite material, and a double perovskite material.

[0048] This makes it possible to increase the electrical conductivity in the first photoelectric conversion layer, thereby improving the efficiency of extracting signal charges from the first photoelectric conversion layer.

[0049] Furthermore, for example, the first photoelectric conversion layer may include a third material that functions as an acceptor for the semiconductor quantum dots.

[0050] As a result, electrons move from the hole-electron pairs generated in the semiconductor quantum dots to the acceptor material, suppressing recombination of the hole-electron pairs and improving the photoelectric conversion efficiency of the first photoelectric conversion layer.

[0051] Furthermore, for example, the first photoelectric conversion layer may include a third material that functions as an acceptor for the semiconductor quantum dots and the first material.

[0052] As a result, electrons move from the hole-electron pairs generated in the semiconductor quantum dots to the acceptor material, suppressing the recombination of the hole-electron pairs and improving the photoelectric conversion efficiency of the first photoelectric conversion layer. In addition, electrons move from the hole-electron pairs generated by the first material absorbing light to the acceptor material, suppressing the generation of energy due to the recombination of the hole-electron pairs.

[0053] Furthermore, for example, the first photoelectric conversion layer may include a third material that functions as an acceptor for the semiconductor quantum dots and the second material.

[0054] As a result, electrons move from the hole-electron pairs generated in the semiconductor quantum dots to the acceptor material, suppressing the recombination of the hole-electron pairs and improving the photoelectric conversion efficiency of the first photoelectric conversion layer. In addition, electrons move from the hole-electron pairs generated by the second material absorbing light to the acceptor material, suppressing the generation of energy due to the recombination of the hole-electron pairs.

[0055] For example, the semiconductor substrate may include silicon.

[0056] Even in such an imaging device using a semiconductor substrate containing silicon that easily absorbs the fluorescence emitted by the coating material, the noise of the imaging device is reduced.

[0057] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0058] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component arrangements and connection forms, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not described in the independent claims are described as optional components.

[0059] In addition, in this specification, elements that are essential for the operation of an imaging device or are effective in improving characteristics but are unnecessary for the explanation of this disclosure are omitted. Furthermore, each drawing is merely a diagram showing a concept, and scale, shape, etc. are not taken into consideration at all. Therefore, for example, the scale, etc. in each drawing do not necessarily match. Furthermore, in each drawing, substantially the same configuration is given the same reference numeral, and duplicate explanations are omitted or simplified.

[0060] Furthermore, in this specification, terms indicating relationships between elements, such as "equal," terms indicating the shapes of elements, such as "square" or "circle," and numerical ranges are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about a few percent.

[0061] In this specification, the terms "upper" and "lower" do not refer to the upper direction (vertically upward) and lower direction (vertically downward) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. The terms "upper" and "lower" are applied not only to the case where two components are arranged with a gap between them and another component exists between the two components, but also to the case where two components are arranged closely together and are in contact with each other.

[0062] (Embodiment 1) [Circuit configuration of imaging device] First, the circuit configuration of the imaging device according to the present embodiment will be described with reference to FIG.

[0063] Fig. 4 is a circuit diagram showing an exemplary circuit configuration of an imaging device according to the present embodiment. The imaging device 100 shown in Fig. 4 has a pixel array PA including a plurality of pixels 10 arranged two-dimensionally. Fig. 4 shows a schematic example in which the pixels 10 are arranged in a matrix of two rows and two columns. The number and arrangement of the pixels 10 in the imaging device 100 are not limited to the example shown in Fig. 4. For example, the imaging device 100 may be a line sensor in which a plurality of pixels 10 are arranged in one column.

[0064] Each pixel 10 has a photoelectric conversion unit 13 and a signal detection circuit 14. The photoelectric conversion unit 13 receives incident light and generates a signal. The photoelectric conversion unit 13 does not need to be an independent element for each pixel 10, and for example, a part of the photoelectric conversion unit 13 may span a plurality of pixels 10. The signal detection circuit 14 is a circuit that detects a signal generated by the photoelectric conversion unit 13. In this example, the signal detection circuit 14 includes a signal detection transistor 24 and an address transistor 26. The signal detection transistor 24 and the address transistor 26 are typically field effect transistors (FETs). Here, an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is exemplified as the signal detection transistor 24 and the address transistor 26. Each transistor, such as the signal detection transistor 24, the address transistor 26, and a reset transistor 28 described later, has a control terminal, an input terminal, and an output terminal. The control terminal is, for example, a gate. The input terminal is one of a drain and a source, for example, a drain. The output terminal is the other of the drain and the source, for example, the source.

[0065] As shown in FIG. 4, the control terminal of the signal detection transistor 24 is electrically connected to the photoelectric conversion unit 13. The signal charge generated by the photoelectric conversion unit 13 is accumulated in a charge accumulation node 41 between the gate of the signal detection transistor 24 and the photoelectric conversion unit 13. Here, the signal charge is a hole or an electron. The charge accumulation node is an example of a charge accumulation unit and is also called a "floating diffusion node." In this specification, the charge accumulation node is also called a charge accumulation region. The structure of the photoelectric conversion unit 13 will be described in detail later.

[0066] The photoelectric conversion unit 13 of each pixel 10 is further connected to a bias control line 42 and a predetermined voltage is applied thereto. In the configuration illustrated in FIG.

[0067] Each pixel 10 is connected to a power supply line 40 that supplies a power supply voltage VDD. As shown in Fig. 4, an input terminal of a signal detection transistor 24 is connected to the power supply line 40. The power supply line 40 functions as a source follower power supply, so that the signal detection transistor 24 amplifies and outputs a signal generated by the photoelectric conversion unit 13.

[0068] An input terminal of the address transistor 26 is connected to an output terminal of the signal detection transistor 24. An output terminal of the address transistor 26 is connected to one of a plurality of vertical signal lines 47 arranged for each column of the pixel array PA. A control terminal of the address transistor 26 is connected to an address control line 46. By controlling the potential of the address control line 46, the output of the signal detection transistor 24 can be selectively read out to the corresponding vertical signal line 47.

[0069] In the illustrated example, the address control line 46 is connected to the vertical scanning circuit 36. The vertical scanning circuit is also called a "row scanning circuit." The vertical scanning circuit 36 ​​applies a predetermined voltage to the address control line 46 to select a plurality of pixels 10 arranged in each row on a row-by-row basis. As a result, signals of the selected pixels 10 are read out and the charge storage nodes 41 are reset.

[0070] The vertical signal lines 47 are main signal lines that transmit pixel signals from the pixel array PA to peripheral circuits. The column signal processing circuits 37 are connected to the vertical signal lines 47. The column signal processing circuits 37 are also called "row signal storage circuits". The column signal processing circuits 37 perform noise suppression signal processing, such as correlated double sampling, and analog-to-digital conversion. As shown in the figure, the column signal processing circuits 37 are provided corresponding to each column of pixels 10 in the pixel array PA. The column signal processing circuits 37 are connected to horizontal signal readout circuits 38. The horizontal signal readout circuits are also called "column scanning circuits". The horizontal signal readout circuits 38 sequentially read out signals from the multiple column signal processing circuits 37 to a horizontal common signal line 49.

[0071] In the configuration illustrated in FIG. 4, the pixel 10 has a reset transistor 28. The reset transistor 28 is, for example, a field effect transistor, similar to the signal detection transistor 24 and the address transistor 26. In the following, unless otherwise specified, an example in which an N-channel MOSFET is applied as the reset transistor 28 will be described. As illustrated, the reset transistor 28 is connected between a reset voltage line 44 that supplies a reset voltage Vr and a charge storage node 41. A control terminal of the reset transistor 28 is connected to a reset control line 48. By controlling the potential of the reset control line 48, the potential of the charge storage node 41 can be reset to the reset voltage Vr. In this example, the reset control line 48 is connected to a vertical scanning circuit 36. Therefore, by the vertical scanning circuit 36 ​​applying a predetermined voltage to the reset control line 48, it is possible to reset a plurality of pixels 10 arranged in each row on a row-by-row basis.

[0072] In this example, a reset voltage line 44 that supplies a reset voltage Vr to the reset transistor 28 is connected to the reset voltage source 34. The reset voltage source is also called a "reset voltage supply circuit." The reset voltage source 34 is not limited to a specific power supply circuit as long as it has a configuration capable of supplying a predetermined reset voltage Vr to the reset voltage line 44 during operation of the imaging device 100, similar to the above-mentioned voltage supply circuit 32. Each of the voltage supply circuit 32 and the reset voltage source 34 may be a part of a single voltage supply circuit or may be an independent separate voltage supply circuit. Note that one or both of the voltage supply circuit 32 and the reset voltage source 34 may be a part of the vertical scanning circuit 36. Alternatively, the control voltage from the voltage supply circuit 32 and / or the reset voltage Vr from the reset voltage source 34 may be supplied to each pixel 10 via the vertical scanning circuit 36.

[0073] It is also possible to use the power supply voltage VDD of the signal detection circuit 14 as the reset voltage Vr. In this case, a voltage supply circuit (not shown in FIG. 4) that supplies a power supply voltage to each pixel 10 and the reset voltage source 34 can be made common. In addition, since the power supply line 40 and the reset voltage line 44 can be made common, the wiring in the pixel array PA can be simplified. However, by making the reset voltage Vr a voltage different from the power supply voltage VDD of the signal detection circuit 14, more flexible control of the imaging device 100 is possible.

[0074] [Pixel device structure] Next, the cross-sectional structure of the pixels 10 of the imaging device 100 according to the present embodiment will be described with reference to FIG.

[0075] The imaging device 100 includes a first light shield. The first light shield absorbs or reflects light of at least a part of the wavelengths in the second wavelength range. The first light shield is located in the first photoelectric conversion layer 15 or above the first photoelectric conversion layer 15. Details of the first light shield will be described later with various examples.

[0076] FIG. 5 is a schematic cross-sectional view showing the cross-sectional structure of a plurality of pixels 10 of an imaging device 100 according to the present embodiment. Although the plurality of pixels 10 shown in FIG. 5 all have the same structure, the plurality of pixels 10 may have a structure that is partially different. Hereinafter, one pixel 10 out of the plurality of pixels 10 will be described. Each pixel 10 of the imaging device 100 includes a semiconductor substrate 20, a plurality of pixel electrodes 11 located above the semiconductor substrate 20 and each of which is electrically connected to the semiconductor substrate 20, a counter electrode 12 located above the plurality of pixel electrodes 11, a first photoelectric conversion layer 15 located between the plurality of pixel electrodes 11 and the counter electrode 12, and an optical filter 16 located above the counter electrode 12. Light is incident on the pixel 10 from above the semiconductor substrate 20. The first light shielding body according to the present embodiment includes the optical filter 16.

[0077] In the configuration illustrated in FIG. 5, the above-mentioned signal detection transistor 24, address transistor 26, and reset transistor 28 are formed on a semiconductor substrate 20. The semiconductor substrate 20 is not limited to a substrate whose entirety is a semiconductor. The semiconductor substrate 20 may be an insulating substrate having a semiconductor layer provided on the surface on which the photosensitive region is formed. For example, a semiconductor substrate containing silicon is used as the semiconductor substrate 20. Here, an example in which a P-type silicon (Si) substrate is used as the semiconductor substrate 20 will be described. The semiconductor substrate 20 is not limited to a semiconductor substrate containing silicon, and may be another semiconductor substrate such as a semiconductor substrate containing gallium arsenide.

[0078] The semiconductor substrate 20 has impurity regions 26s, 24s, 24d, 28d, and 28s, and an element isolation region 20t for electrical isolation between the pixels 10. Here, the impurity regions 26s, 24s, 24d, 28d, and 28s are N-type regions. The element isolation region 20t is also provided between the impurity region 24d and the impurity region 28d. The element isolation region 20t is formed, for example, by ion implantation of an acceptor under predetermined implantation conditions.

[0079] The impurity regions 26s, 24s, 24d, 28d, and 28s are, for example, impurity diffusion layers formed in the semiconductor substrate 20. As shown in FIG. 5, the signal detection transistor 24 includes the impurity region 24s, the impurity region 24d, and the gate electrode 24g. The gate electrode 24g is formed using a conductive material. The conductive material is, for example, polysilicon that is doped with impurities to give it conductivity, but may also be a metal material. The impurity region 24s functions as, for example, a source region of the signal detection transistor 24. The impurity region 24d functions as, for example, a drain region of the signal detection transistor 24. A channel region of the signal detection transistor 24 is formed between the impurity region 24s and the impurity region 24d.

[0080] Similarly, the address transistor 26 includes an impurity region 26s, an impurity region 24s, and a gate electrode 26g. The gate electrode 26g is formed using a conductive material. The conductive material is, for example, polysilicon that is doped with impurities to give it conductivity, but may be a metal material. The gate electrode 26g is connected to an address control line 46 not shown in FIG. 5. In this example, the signal detection transistor 24 and the address transistor 26 are electrically connected to each other by sharing the impurity region 24s. The impurity region 24s functions as, for example, a drain region of the address transistor 26. The impurity region 26s functions as, for example, a source region of the address transistor 26. The impurity region 26s is connected to a vertical signal line 47 not shown in FIG. 5. Note that the impurity region 24s does not have to be shared by the signal detection transistor 24 and the address transistor 26. Specifically, the source region of the signal detection transistor 24 and the drain region of the address transistor 26 are separated in the semiconductor substrate 20, and may be electrically connected via a wiring layer provided in the interlayer insulating layer 50.

[0081] The reset transistor 28 includes impurity regions 28d and 28s and a gate electrode 28g. The gate electrode 28g is formed using, for example, a conductive material. The conductive material is, for example, polysilicon that is doped with impurities to give it conductivity, but may also be a metal material. The gate electrode 28g is connected to a reset control line 48 not shown in FIG. 5. The impurity region 28s functions as, for example, a source region of the reset transistor 28. The impurity region 28s is connected to a reset voltage line 44 not shown in FIG. 5. The impurity region 28d functions as, for example, a drain region of the reset transistor 28.

[0082] An interlayer insulating layer 50 is disposed on the semiconductor substrate 20 so as to cover the signal detection transistor 24, the address transistor 26, and the reset transistor 28. The interlayer insulating layer 50 is formed of an insulating material such as silicon dioxide. As shown in the figure, a wiring layer 56 is disposed in the interlayer insulating layer 50. The wiring layer 56 is typically formed of a metal such as copper. The wiring layer 56 may include, for example, a signal line such as the vertical signal line 47 or a power line in a part thereof. The number of insulating layers in the interlayer insulating layer 50 and the number of layers included in the wiring layer 56 disposed in the interlayer insulating layer 50 can be set arbitrarily and are not limited to the example shown in FIG. 5.

[0083] 5, a plug 52, a wiring 53, a contact plug 54, and a contact plug 55 are provided in the interlayer insulating layer 50. The wiring 53 may be a part of a wiring layer 56. The plug 52, the wiring 53, the contact plug 54, and the contact plug 55 are each formed using a conductive material. For example, the plug 52 and the wiring 53 are formed from a metal such as copper. The contact plugs 54 and 55 are formed from, for example, polysilicon doped with impurities to provide conductivity. The plug 52, the wiring 53, the contact plug 54, and the contact plug 55 may be formed from the same material as each other, or may be formed from different materials.

[0084] 5, the plug 52, the wiring 53, and the contact plug 54 form at least a part of the charge accumulation node 41 between the signal detection transistor 24 and the photoelectric conversion unit 13. In the configuration illustrated in FIG. 5, the gate electrode 24g of the signal detection transistor 24, the plug 52, the wiring 53, the contact plugs 54 and 55, and the impurity region 28d which is one of the source region and the drain region of the reset transistor 28 function as a charge accumulation region that accumulates the signal charge collected by the pixel electrode 11 of the photoelectric conversion unit 13.

[0085] Specifically, the pixel electrode 11 of the photoelectric conversion unit 13 is connected to the gate electrode 24g of the signal detection transistor 24 via the plug 52, the wiring 53, and the contact plug 54. In other words, the gate of the signal detection transistor 24 is electrically connected to the pixel electrode 11. The pixel electrode 11 is also connected to the impurity region 28d via the plug 52, the wiring 53, and the contact plug 55.

[0086] When the pixel electrode 11 collects the signal charge, a voltage corresponding to the amount of the signal charge accumulated in the charge accumulation region is applied to the gate of the signal detection transistor 24. The signal detection transistor 24 amplifies this voltage. The voltage amplified by the signal detection transistor 24 is selectively read out as a signal voltage via the address transistor 26.

[0087] The above-mentioned photoelectric conversion unit 13 is disposed on the interlayer insulating layer 50. When the semiconductor substrate 20 is viewed in a plan view, the multiple pixels 10 arranged two-dimensionally form a photosensitive region. The photosensitive region is also called a pixel region. The distance between two adjacent pixels 10, i.e., the pixel pitch, may be, for example, about 2 μm.

[0088] [Photoelectric conversion section configuration] The specific configuration of the photoelectric conversion unit 13 will be described below.

[0089] 5, the photoelectric conversion unit 13 includes a plurality of pixel electrodes 11, a counter electrode 12, and a first photoelectric conversion layer 15 disposed between the plurality of pixel electrodes 11 and the counter electrode 12. An optical filter 16 is provided on the counter electrode 12 of the photoelectric conversion unit 13. In this embodiment, the optical filter 16, the counter electrode 12, the first photoelectric conversion layer 15, and the plurality of pixel electrodes 11 are disposed in this order from the light incident side of the imaging device 100. That is, the optical filter 16 is disposed at a position closer to the counter electrode 12 than the first photoelectric conversion layer 15, in other words, on the light incident side.

[0090] The photoelectric conversion section 13 may further include other elements such as an electron blocking layer and a hole blocking layer.

[0091] 5, the counter electrode 12, the first photoelectric conversion layer 15, and the optical filter 16 are formed across a plurality of pixels 10. A pixel electrode 11 is provided for each pixel 10. The pixel electrode 11 is spatially separated from the pixel electrodes 11 of other adjacent pixels 10, and is thereby electrically separated from the pixel electrodes 11 of the other pixels 10. At least one of the counter electrode 12, the first photoelectric conversion layer 15, and the optical filter 16 may be provided separately for each pixel 10.

[0092] The pixel electrode 11 is an electrode for reading out a signal charge generated in the photoelectric conversion unit 13. At least one pixel electrode 11 exists for each pixel 10. The pixel electrode 11 is electrically connected to a gate electrode 24g of the signal detection transistor 24 and an impurity region 28d.

[0093] The pixel electrode 11 is formed using a conductive material, such as a metal such as aluminum or copper, a metal nitride, or polysilicon doped with impurities to be made conductive.

[0094] The counter electrode 12 is, for example, a transparent electrode made of a transparent conductive material. The counter electrode 12 is disposed on the side of the first photoelectric conversion layer 15 on which light is incident. Therefore, light transmitted through the counter electrode 12 is incident on the first photoelectric conversion layer 15. Note that the light detected by the imaging device 100 is not limited to light within the wavelength range of visible light. For example, the imaging device 100 may detect infrared light or ultraviolet light. Here, the wavelength range of visible light is, for example, 380 nm or more and 780 nm or less.

[0095] In this specification, "transparent" means that at least a part of the light in the wavelength range to be detected is transmitted, and it is not essential that the light is transmitted over the entire wavelength range of visible light. For convenience, in this specification, electromagnetic waves in general, including infrared light and ultraviolet light, are referred to as "light."

[0096] The counter electrode 12 is formed using a transparent conducting oxide (TCO) such as ITO, IZO, AZO, FTO, SnO2, TiO2, or ZnO. A voltage supply circuit 32 shown in Fig. 4 is connected to the counter electrode 12. By adjusting the voltage applied to the counter electrode 12 by the voltage supply circuit 32, the potential difference between the counter electrode 12 and the pixel electrode 11 can be set and maintained at a desired potential difference.

[0097] As described with reference to Fig. 4, the counter electrode 12 is connected to a bias control line 42 that is connected to the voltage supply circuit 32. Here, the counter electrode 12 is formed across a plurality of pixels 10. Therefore, a control voltage of a desired magnitude can be applied collectively between a plurality of pixels 10 from the voltage supply circuit 32 via the bias control line 42. Note that, as long as a control voltage of a desired magnitude can be applied from the voltage supply circuit 32, the counter electrode 12 may be provided separately for each pixel 10.

[0098] The voltage supply circuit 32 controls the potential of the counter electrode 12 relative to the potential of the pixel electrode 11, so that either the holes or the electrons of the hole-electron pairs generated in the first photoelectric conversion layer 15 by photoelectric conversion can be collected by the pixel electrode 11 as a signal charge. For example, when holes are used as signal charges, the pixel electrode 11 can selectively collect the holes by setting the potential of the counter electrode 12 higher than that of the pixel electrode 11. The following illustrates a case where holes are used as signal charges. Of course, electrons can also be used as signal charges, and in this case, the potential of the counter electrode 12 can be set lower than that of the pixel electrode 11. The pixel electrode 11 facing the counter electrode 12 collects one of the positive and negative charges generated by photoelectric conversion in the first photoelectric conversion layer 15 by applying an appropriate bias voltage between the counter electrode 12 and the pixel electrode 11.

[0099] The first photoelectric conversion layer 15 is a layer that absorbs photons and generates photocharges. Specifically, the first photoelectric conversion layer 15 receives incident light and generates hole-electron pairs. That is, the signal charge is either a hole or an electron. In this embodiment, a case where the signal charge is a hole will be described as an example, but the signal charge may be an electron. The hole, which is the signal charge, is collected by the pixel electrode 11. The electron, which is a charge of the opposite polarity to the signal charge, is collected by the counter electrode 12.

[0100] The first photoelectric conversion layer 15 includes semiconductor quantum dots and a coating material that coats the semiconductor quantum dots. The first photoelectric conversion layer 15 may further include an acceptor material. The acceptor material is an example of a third material.

[0101] The semiconductor quantum dots generate hole-electron pairs, i.e., positive and negative charges, upon receiving incident light. The semiconductor quantum dots function, for example, as donors to an acceptor material. That is, the semiconductor quantum dots donate electrons to the acceptor material. The semiconductor quantum dots may also transfer electrons to the pixel electrode 11 or the counter electrode 12 without passing through the acceptor material.

[0102] Semiconductor quantum dots are materials that exhibit a three-dimensional quantum confinement effect. Semiconductor quantum dots are nanocrystals with a diameter of about 2 nm to 10 nm, and are composed of about several tens of atoms. The materials of semiconductor quantum dots are, for example, group IV semiconductors such as Si or Ge, group IV-VI semiconductors such as PbS, PbSe, or PbTe, group III-V semiconductors such as InAs or InSb, or ternary mixed crystals such as HgCdTe or PbSnTe.

[0103] The semiconductor quantum dot has a characteristic of absorbing light in a first wavelength range. FIG. 6 is a diagram showing an example of an absorption spectrum of a semiconductor quantum dot. The absorption spectrum shown in FIG. 6 is an absorption spectrum of a semiconductor quantum dot whose core material is PbS and whose particle size is about 5 nm. FIG. 6 also shows a spectrum in which the range from 1200 nm to 1800 nm is enlarged by 10 times. As shown in FIG. 6, the semiconductor quantum dot has an absorption peak. In the example shown in FIG. 6, the wavelength of the absorption peak of the semiconductor quantum dot is in the wavelength range of infrared light. The absorption peak wavelength of the semiconductor quantum dot is derived from the energy gap of the semiconductor quantum dot and can be controlled by the core material and particle size of the semiconductor quantum dot.

[0104] The first wavelength range is a wavelength range in which the semiconductor quantum dot absorbs light and generates electric charges, such as the light absorption peak wavelength shown in Fig. 6. In other words, the first wavelength range is a wavelength range in which the semiconductor quantum dot exhibits significant quantum efficiency. For example, the first wavelength range is a wavelength range in which the light absorptance of the semiconductor quantum dot is 1% or more.

[0105] Since the semiconductor quantum dots exhibit an absorption peak in a specific narrow wavelength range, narrowband wavelength imaging can be realized by the first photoelectric conversion layer 15 using the semiconductor quantum dots. In particular, when the semiconductor quantum dots exhibit light absorption in a narrow wavelength range in the infrared light wavelength range, high sensitivity imaging using the infrared light wavelength, etc. is possible. Examples of semiconductor quantum dots exhibiting an absorption peak in the infrared light wavelength range include semiconductor quantum dots whose core material is PbS, PbSe, PbTe, InAs, InSb, Ag2S, Ag2Se, Ag2Te, CuS, CuInS2, CuInSe2, AgInS2, AgInSe2, AgInTe2, ZnSnAs2, ZnSnSb2, CdGeAs2, CdSnAs2, HgCdTe, or InGaAs.

[0106] The first photoelectric conversion layer 15 may contain multiple types of semiconductor quantum dots with different particle sizes and / or multiple types of semiconductor quantum dots with different core materials. Fig. 7 is a schematic diagram showing an example of the absorption spectrum of a semiconductor quantum dot containing multiple types of semiconductor quantum dots. As shown in Fig. 7, a semiconductor quantum dot containing multiple types of semiconductor quantum dots with different particle sizes and / or multiple types of semiconductor quantum dots with different core materials has multiple absorption peaks.

[0107] Furthermore, the first photoelectric conversion layer 15 may contain, in addition to the semiconductor quantum dots, a material that donates electrons to the acceptor material and functions as a donor.

[0108] The acceptor material functions as an acceptor for the semiconductor quantum dots. The acceptor material is, for example, an electron acceptor material that accepts electrons from the semiconductor quantum dots. As a result, electrons move from the hole-electron pairs generated in the semiconductor quantum dots to the acceptor material, suppressing recombination of the hole-electron pairs and improving the photoelectric conversion efficiency of the first photoelectric conversion layer 15.

[0109] Acceptor materials include, for example, C60 (fullerene) and PCBM (phenyl C 61 Butyric acid methyl ester), ICBA (Indene C60 Examples of the acceptor material include C60 derivatives such as bis-adducts, and oxide semiconductors such as TiO2, ZnO, and SnO2. Note that the acceptor material is not limited to these, and any material that can accept electrons from the semiconductor quantum dots may be used as the acceptor material, as described above. The acceptor material may be one material type or a combination of multiple material types.

[0110] The coating material is a material that coats the semiconductor quantum dots and is used to suppress the formation of secondary particles of the semiconductor quantum dots, stabilize the film quality, and improve the electrical conductivity between the semiconductor quantum dots. The coating material has the property of absorbing light in a second wavelength range and emitting fluorescence in a third wavelength range. The coating material includes, for example, at least one of a ligand material and a matrix material.

[0111] The second wavelength range is a wavelength range in which the coating material exhibits significant absorption, specifically, a wavelength range of light absorbed by the coating material when the coating material absorbs light and emits fluorescence to an extent that affects the operation of the imaging device 100, such as image bleeding, color mixing noise, or malfunction. For example, it is a wavelength range in which the light absorption rate of the coating material is 1% or more. The second wavelength range also depends on, for example, the type of coating material, the fluorescence emission probability, the thickness of the first photoelectric conversion layer 15, the imaging purpose of the image sensor, the shooting environment, and the like.

[0112] The third wavelength range is the wavelength range of the fluorescence emitted when the coating material absorbs light in the second wavelength range. For example, in the case of P3HT, which is an example of a matrix material, as shown in Figure 2, it emits significant fluorescence when it absorbs light in the wavelength range from about 400 nm to about 650 nm.

[0113] The matrix material is a material that fills the spaces between the multiple semiconductor quantum dots in the first photoelectric conversion layer 15 to cover the semiconductor quantum dots and improves the electrical conductivity of the first photoelectric conversion layer 15.

[0114] The matrix material is, for example, a material containing at least one of a semiconductor polymer, a semiconductor copolymer, a semiconductor oligomer, a low molecular weight semiconductor, a perovskite material, and a double perovskite material. By including these materials in the matrix material, the electrical conductivity between the semiconductor quantum dots is improved, the electrical conductivity in the first photoelectric conversion layer 15 is improved, and the first photoelectric conversion layer 15 having good film quality can be formed.

[0115] As the semiconducting polymer and semiconducting oligomer, for example, a semiconducting oligomer and semiconducting polymer having a planar monomer skeleton, such as a polymer of fluorene, a fluorene derivative, a thiophene, a thiophene derivative, and a phenylenevinylene derivative, and being of π-electron conjugation type, is used. The semiconducting polymer may be a semiconducting copolymer containing 50% or more of the above-mentioned monomers. Specific examples of the semiconducting polymer and semiconducting copolymer include P3HT, PFO (polyfluorene), PFO-BT (poly(fluorene-benzothiadiazole)), PT (polythiophene), and MDMO-PPV (poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene]), etc.

[0116] Low child and half The conductor is, for example, a small molecule organic semiconductor that is soluble in the solvent of the semiconductor quantum dot.

[0117] The perovskite material is, for example, an inorganic perovskite compound such as CsPbBr2I, CsSnI3, etc. The perovskite material may also be an organic-inorganic perovskite compound such as CH3NH3SnI3.

[0118] The double perovskite material is, for example, an inorganic double perovskite type compound. double The perovskite material may be an organic-inorganic double perovskite compound.

[0119] The ligand material is a surface modification group that coats the semiconductor quantum dots by modifying the surface of the semiconductor quantum dots. The ligand material is, for example, a ligand material having π-conjugation. This improves the electrical conductivity between the semiconductor quantum dots, improves the electrical conductivity in the first photoelectric conversion layer 15, and suppresses the formation of secondary particles of the semiconductor quantum dots.

[0120] Specific examples of ligand materials having π-conjugation include organic molecules having a π-conjugated molecular skeleton such as a polyacene skeleton or a thiophene derivative skeleton, and having at least one terminal group such as a thiol group, a carboxyl group, or an amino group that adsorbs to atoms on the surface of the semiconductor quantum dot.

[0121] The optical filter 16 has a non-zero optical reflectance or a non-zero optical absorbance at at least a portion of the wavelengths in the second wavelength range in which the coating material exhibits significant absorption. Also, for example, the optical filter 16 has a non-zero optical reflectance or a non-zero optical absorbance at wavelengths in the second wavelength range that include a wavelength in which the coating material exhibits maximum optical absorbance. Also, for example, the optical filter 16 has a non-zero optical reflectance or a non-zero optical absorbance at all wavelengths in the second wavelength range.

[0122] The optical filter 16 reduces the transmittance of light in the second wavelength range by reflecting or absorbing the light in the second wavelength range, and reduces the amount of light absorbed and fluorescently emitted by the coating material.

[0123] For example, the optical filter 16 does not substantially transmit light in the second wavelength range. "Substantially not transmitting light in the second wavelength range" means that the light transmitted through the optical filter 16 is absorbed by the coating material, the coating material emits fluorescence, and the fluorescence is absorbed in the charge accumulation region and does not significantly generate a false signal or does not significantly cause the control circuit to malfunction.

[0124] The optical filter 16 absorbs or reflects light with a wavelength of, for example, 1050 nm or less. This makes it difficult for light in the wavelength range from near infrared to visible light to be absorbed by the coating material. The optical filter 16 may also absorb or reflect light with a wavelength of 700 nm or less.

[0125] The transmittance of the optical filter 16 for light in the second wavelength range depends on the absorption coefficient and fluorescence emission probability of the covering material, the thickness of the first photoelectric conversion layer 15, the imaging purpose and imaging environment of the imaging device 100, etc., but is, for example, a transmittance at which the light absorptance of the covering material is 1% or less for all wavelengths in the second wavelength range. Specifically, the transmittance of the optical filter 16 for light in the second wavelength range is, for example, 5% or less, and may be 1% or less.

[0126] As described above, the optical filter 16 is located on the side where light enters the imaging device relative to the first photoelectric conversion layer 15, and absorbs or reflects at least a portion of the light in the second wavelength range. This makes it possible to reduce the amount of light in the second wavelength range that reaches the coating material. This makes it possible to reduce the fluorescence emitted by the coating material being excited by light in the second wavelength range. In other words, it is possible to reduce noise and the like that occurs when the charge accumulation region or the like absorbs the fluorescence emitted by the coating material.

[0127] The optical filter 16 transmits light of at least a part of the wavelengths in the first wavelength range. In other words, the optical filter 16 has significant transmittance for at least a part of the wavelengths in the first wavelength range. Having significant transmittance means that the light transmitted through the optical filter 16 is photoelectrically converted by the semiconductor quantum dots and has a transmittance to the extent that imaging is possible. The transmittance of the optical filter 16 for light of the first wavelength range depends on the shooting conditions and the shooting intention, but is, for example, 50% or more.

[0128] In addition, when the first photoelectric conversion layer 15 contains multiple types of semiconductor quantum dots with different particle sizes and / or multiple semiconductor quantum dots with different core materials as shown in Figure 7, the optical filter 16 may have significant transparency in a wavelength range that includes the absorption peak wavelength of any of the types of semiconductor quantum dots.

[0129] In this manner, the optical filter 16 transmits light of at least a portion of the wavelengths in the first wavelength range, so that degradation of the photoelectric conversion function in the first photoelectric conversion layer 15 can be suppressed.

[0130] The optical filter 16 may be an absorption type filter using colored glass or the like, or may be a reflection type filter having a laminate of dielectric multilayer films.

[0131] An example of an absorption type filter is colored glass RG715 manufactured by Schott. Colored glass RG715 has the property of blocking light with a wavelength of 700 nm or less and transmitting light with a wavelength of 800 nm or more. For example, when colored glass RG715 is used for the optical filter 16, the optical filter 16 can transmit light with an absorption peak wavelength of a semiconductor quantum dot having an energy gap in the near infrared region.

[0132] Furthermore, when the colored glass RG715 is used for the optical filter 16, if the upper limit value of the second wavelength range of the matrix material, such as P3HT or CsPbBr2I, is 700 nm or less, the optical filter 16 will not substantially transmit light in the second wavelength range.

[0133] The above is merely an example, and an optical filter having appropriate characteristics may be selected based on the absorption spectrum of the coating material and the absorption spectrum of the semiconductor quantum dots.

[0134] The optical filter 16 may be, for example, a long-pass filter that blocks light having a wavelength shorter than a certain wavelength and transmits light having a wavelength longer than the wavelength, or a band-pass filter that transmits only light in a specific wavelength range and blocks light having a wavelength shorter than the wavelength range and light having a wavelength longer than the wavelength range. For example, the transmission wavelength range of the band-pass filter may be substantially the same as the absorption peak wavelength of the semiconductor quantum dot.

[0135] Alternatively, the optical filter 16 may be, for example, a notch filter that blocks a wavelength range that includes the second wavelength range and transmits light with wavelengths shorter and longer than that wavelength range.

[0136] As shown in FIG. 5, the optical filter 16 may be disposed directly above the counter electrode 12, or may be disposed on a sealing film (not shown in FIG. 5) formed on the counter electrode 12, or may be disposed on glass (not shown in FIG. 5) attached to protect the imaging surface of the imaging device 100.

[0137] Furthermore, the optical filter 16 does not need to be disposed near the photoelectric conversion unit 13, and may be disposed on the optical path of the imaging system. For example, the optical filter 16 may be disposed between the imaging lens and the photoelectric conversion unit 13, within the imaging lens, or in front of the imaging lens.

[0138] The optical filter 16 may also function as a sealing film that suppresses the transmission of oxygen and water vapor.

[0139] The optical filter 16 may also be used together with a multispectral imaging optical filter for changing the imaging spectrum for each pixel, for example. Alternatively, the multispectral imaging optical filter may perform the function of the optical filter 16.

[0140] Furthermore, the optical filter 16 is not limited to being fixed, but may be configured to be switchable with other optical filters as necessary, for example.

[0141] (Embodiment 2) Next, a description will be given of embodiment 2. In embodiment 2, a first charge transport layer is used as the first light shielding body instead of an optical filter, which is different from embodiment 1. In the following, the description will be centered on the differences from embodiment 1, and the description of the commonalities will be omitted or simplified.

[0142] [Photoelectric conversion section configuration] Fig. 8 is a schematic cross-sectional view showing a cross-sectional structure of a plurality of pixels 10a of the imaging device 100 according to the present embodiment. As shown in Fig. 8, the pixel 10a is different from the pixel 10 according to the first embodiment in that the pixel 10a does not include the optical filter 16 and includes a photoelectric conversion unit 13a instead of the photoelectric conversion unit 13.

[0143] The photoelectric conversion unit 13a includes a plurality of pixel electrodes 11, a counter electrode 12, a first photoelectric conversion layer 15 located between the plurality of pixel electrodes 11 and the counter electrode 12, and a first charge transport layer 17 located between the counter electrode 12 and the first photoelectric conversion layer 15. In this embodiment, the counter electrode 12, the first charge transport layer 17, the first photoelectric conversion layer 15, and the plurality of pixel electrodes 11 are arranged in this order from the light incidence side of the imaging device 100. In other words, the first charge transport layer 17 is arranged closer to the light incidence side than the first photoelectric conversion layer 15. The first light shield according to this embodiment includes the first charge transport layer 17.

[0144] 8, the first charge transport layer 17 is disposed between and in contact with the first photoelectric conversion layer 15 and the counter electrode 12. The first charge transport layer 17 has a function of transporting the charges collected by the counter electrode 12 out of the positive charges or negative charges generated in the first photoelectric conversion layer 15.

[0145] The first charge transport layer 17 has a non-zero light absorptance at at least a portion of the wavelengths in the second wavelength range. For example, the first charge transport layer 17 has a non-zero light absorptance at wavelengths in the second wavelength range that include a wavelength at which the coating material exhibits the maximum light absorptance. For example, the first charge transport layer 17 has a non-zero light absorptance at all wavelengths in the second wavelength range. For example, the first charge transport layer 17 may not substantially transmit light in the second wavelength range.

[0146] The first charge transport layer 17 absorbs light having a wavelength of, for example, 1050 nm or less. This makes it difficult for light having a wavelength range from near infrared to visible light to be absorbed by the coating material. The first charge transport layer 17 may also absorb light having a wavelength of 700 nm or less.

[0147] The first charge transport layer 17 has significant transparency to at least a part of light in a first wavelength range. When the first photoelectric conversion layer 15 including semiconductor quantum dots has a plurality of light absorption peak wavelengths, the first charge transport layer 17 may have significant transparency at any of the light absorption peak wavelengths of the semiconductor quantum dots.

[0148] The light transmittance of the first charge transport layer 17 depends on the light absorption coefficient of the material constituting the first charge transport layer 17 and the thickness of the first charge transport layer 17 .

[0149] The transmittance of the first charge transport layer 17 for light in the second wavelength range is, for example, 5% or less, and may be 1% or less.

[0150] The charge transport material of the first charge transport layer 17 is not particularly limited as long as it is a material having the above-mentioned light transparency. Examples of the charge transport material of the first charge transport layer 17 include fullerene and fullerene derivatives such as PCBM, perylene derivatives such as PTCDA and PTCBI, and BT-CIC represented by the following structural formula (1) and CO represented by the following structural formula (2). iExamples of such a material include non-fullerene-based low-bandgap organic semiconductors such as 8DFIC. These materials have a relatively deep lowest unoccupied molecular orbital level based on the vacuum level, and tend to easily accept electrons from the semiconductor quantum dots at the contact interface with the semiconductor quantum dots. In this way, when it is desired to transport electrons, which are negative charges, as the first charge transport layer 17, a material having the above-mentioned optical transparency may be selected from among materials having a lowest unoccupied molecular orbital level or a conduction band lower end level deeper than the lowest unoccupied molecular orbital level of the semiconductor quantum dots used as the charge transport material of the first charge transport layer 17. Conversely, when it is desired to transport holes, which are positive charges, as the first charge transport layer 17, a material having the above-mentioned optical transparency may be selected from among materials having a highest occupied molecular orbital level or a valence band upper end level shallower than the highest occupied molecular orbital level of the semiconductor quantum dots used as the charge transport material of the first charge transport layer 17.

[0151] [ka] [ka]

[0152] The transmittance of the first charge transport layer 17 will be described using C70, which exhibits negative charge transport properties, as an example. i FIG. 1 shows the absorption spectrum of 8DFIC.

[0153] As shown in FIG. 9, C60 tends to absorb light in the wavelength range of about 550 nm or less. C70 tends to absorb light in the wavelength range of about 700 nm or less. BT-CIC tends to absorb light in the wavelength range of 600 nm to 950 nm. i 8DFIC easily absorbs light in the wavelength range of 600 nm or more and 1000 nm or less.

[0154] FIG. 10 is a diagram showing the results of simulating the light transmittance of C70 layers of different thicknesses. In the simulation results of the transmittance shown in FIG. 10, the vertical axis indicates the transmittance and the horizontal axis indicates the wavelength. In FIG. 10, the transmittance is shown assuming that the case where all light of the wavelength on the horizontal axis is transmitted is 1. For example, when the transmittance is converted into a percentage, 1 is 100% and 0.01 is 1%. In FIG. 10, the vertical axis is a logarithmic axis in common logarithm format. Transmittance is shown.

[0155] As shown in FIG. 10, the transmittance of the light having a wavelength of 600 nm or less in the C70 layer having a thickness of 400 nm or more is 5% or less, and the transmittance of the light having a wavelength of 600 nm or less in the C70 layer having a thickness of 600 nm or more is 1% or less. In addition, C70 has a function of transporting negative charges. Therefore, in the imaging device 100 in which the counter electrode 12 collects negative charges, the C70 layer functions as a charge transport layer and also serves to reduce the proportion of light having a wavelength of 600 nm or less that reaches the first photoelectric conversion layer 15. Therefore, when the matrix material is the perovskite material CsPbBr2I, the transmittance of the matrix material in the absorption wavelength range can be reduced, and the fluorescent emission that causes noise can be suppressed.

[0156] In this way, from the viewpoint of reducing the transmittance of light in the second wavelength range, the thickness of the first charge transport layer 17 is, for example, 400 nm or more, and may be 600 nm or more.

[0157] The first charge transport layer 17 may be made of a single type of material or a plurality of types of materials. For example, by mixing a plurality of materials with different absorption spectra, the transmittance of light can be reduced in a wider wavelength range. For example, CO, which has a large absorption coefficient in the wavelength range from 600 nm to 1000 nm, can be mixed. i If the first charge transport layer 17 is made of a mixed layer of 8DFIC and C70, which has a large absorption coefficient in the wavelength range of 700 nm or less, the light transmittance can be reduced in a wider wavelength range than if the first charge transport layer 17 was made of only C70.i FIG. 11 is a diagram showing the results of a simulation of the light transmittance of a mixed layer of 8DFIC and C70. i The results of the mixed layer when 8DFIC and C70 are mixed in a 1:1 ratio are shown in Fig. 11. As shown in Fig. 11, by making the thickness of the mixed layer 1000 nm or more, the transmittance of light with a wavelength of 900 nm or less can be reduced to 1% or less.

[0158] The first charge transport layer 17 may be composed of a mixture of a charge transporting material and a non-charge transporting material. For example, a material that performs the function of transporting charges may be selected as the charge transporting material, and a material that has a desired absorption spectrum, such as absorbing light in a second wavelength range, may be selected as the non-charge transporting material.

[0159] (Embodiment 3) Next, a description will be given of embodiment 3. In embodiment 3, a second photoelectric conversion layer is used as the first light shielding body instead of an optical filter, which is different from embodiment 1. In the following, the description will be centered on the differences from embodiment 1, and the description of the commonalities will be omitted or simplified.

[0160] [Photoelectric conversion section configuration] Fig. 12 is a schematic cross-sectional view showing the cross-sectional structure of a plurality of pixels 10b of the imaging device 100 according to the present embodiment. As shown in Fig. 12, the pixel 10b is different from the pixel 10 according to the first embodiment in that the pixel 10b does not include the optical filter 16 and includes a photoelectric conversion unit 13b instead of the photoelectric conversion unit 13.

[0161] The photoelectric conversion unit 13b includes a plurality of pixel electrodes 11, a counter electrode 12, a first photoelectric conversion layer 15 located between the plurality of pixel electrodes 11 and the counter electrode 12, and a second photoelectric conversion layer 18 located between the counter electrode 12 and the first photoelectric conversion layer 15. In this embodiment, the counter electrode 12, the second photoelectric conversion layer 18, the first photoelectric conversion layer 15, and the plurality of pixel electrodes 11 are arranged in this order from the light incidence side of the imaging device 100. In other words, the second photoelectric conversion layer 18 is arranged closer to the light incidence side than the first photoelectric conversion layer 15. The first light shield according to this embodiment includes the second photoelectric conversion layer 18.

[0162] The second photoelectric conversion layer 18 includes, for example, a donor material and an acceptor material. The donor material included in the second photoelectric conversion layer 18 is a material different from the semiconductor quantum dots, and is an electron donor material that functions as a donor that provides electrons to the acceptor material included in the second photoelectric conversion layer 18. The acceptor material included in the second photoelectric conversion layer 18 is an electron acceptor material that functions as an acceptor that accepts electrons to the donor material included in the second photoelectric conversion layer 18. Even if the donor material is a material that emits fluorescence when it absorbs light, if an appropriate amount of acceptor material is included, excited electrons move to the acceptor material, and the generation of fluorescence is suppressed.

[0163] The electron transport material contained in the first photoelectric conversion layer 15 and the acceptor material contained in the second photoelectric conversion layer 18 may be the same substance or different substances. For example, the acceptor material contained in the first photoelectric conversion layer 15 and the acceptor material contained in the second photoelectric conversion layer 18 may both be C60, or the acceptor material contained in the first photoelectric conversion layer 15 may be C60 and the acceptor material contained in the second photoelectric conversion layer 18 may be PCBM.

[0164] The second photoelectric conversion layer 18 has a non-zero light absorptance at at least a portion of the wavelengths in the second wavelength range. For example, the second photoelectric conversion layer 18 has a non-zero light absorptance at wavelengths in the second wavelength range that include a wavelength at which the coating material exhibits the maximum light absorptance. For example, the second photoelectric conversion layer 18 has a non-zero light absorptance at all wavelengths in the second wavelength range. For example, the second photoelectric conversion layer 18 does not substantially transmit light in the second wavelength range.

[0165] The second photoelectric conversion layer 18 absorbs light with a wavelength of, for example, 1050 nm or less. This makes it difficult for light with a wavelength range from near infrared to visible light to be absorbed by the coating material. The second photoelectric conversion layer 18 may also absorb light with a wavelength of 700 nm or less.

[0166] The second photoelectric conversion layer 18 has significant transparency to at least a part of light in the first wavelength range. When the photoelectric conversion layer including the semiconductor quantum dots has a plurality of light absorption peak wavelengths, the second photoelectric conversion layer 18 may have significant transparency at any of the light absorption peak wavelengths of the semiconductor quantum dots.

[0167] For example, it is preferable that the wavelength at which the second photoelectric conversion layer 18 does not substantially transmit light is shorter than the shortest wavelength among the multiple light absorption peak wavelengths possessed by the first photoelectric conversion layer 15 containing semiconductor quantum dots.

[0168] The light transmittance of the second photoelectric conversion layer 18 depends on the light absorption coefficient of each material constituting the second photoelectric conversion layer 18 and the thickness of the second photoelectric conversion layer 18 .

[0169] FIG. 13 is a diagram showing the absorption spectrum of a mixed film of SnNcCl2 and C70. FIG. 13 shows the absorption spectrum of the mixed film when SnNcCl2 and C70 are mixed at 1:1. As shown in FIG. 13, for example, in the second photoelectric conversion layer 18, when the donor material is SnNcCl2 (tin phthalocyanine dichloride) and the acceptor material is C70, the second photoelectric conversion layer 18 consisting of a 1:1 mixed film of the donor material and the acceptor material does not show significant absorption at wavelengths of about 1200 nm or more. In other words, the mixed film transmits light with a wavelength of about 1200 nm or more. On the other hand, the mixed film shows absorption at light with a wavelength of about 1200 nm or less. For example, in the wavelength range of 600 nm or less and the wavelength range of 720 nm to 980 nm, the light absorption coefficient of the mixed film is 2.0×10 4 cm -1The value is equal to or more. Therefore, if the mixed film has a thickness of 1000 nm or more, the mixed film has a transmittance of 1% or less for light in the wavelength range of 600 nm or less and the wavelength range of 720 nm to 980 nm. Therefore, even if the first photoelectric conversion layer 15 contains, for example, CsPbBr2I as a matrix material, the second photoelectric conversion layer 18 has a transmittance of 1% or less for light in the second wavelength range of CsPbBr2I, so that the generation of fluorescence due to CsPbBr2I is suppressed. Also, even if the second photoelectric conversion layer 18 contains, for example, P3HT, CsSnI3, and CH3NH3SnI3 as a matrix material, the second photoelectric conversion layer 18 has a transmittance of 1% or less for light in most wavelengths in the second wavelength range of P3HT, CsSnI3, and CH3NH3SnI3, so that the generation of fluorescence due to P3HT, CsSnI3, and CH3NH3SnI3 is suppressed.

[0170] The light absorption coefficient may vary slightly depending on the mixture ratio, film quality, and the like.

[0171] The donor material contained in the second photoelectric conversion layer 18 may have quantum efficiency for light in the second wavelength range. As a result, light in the second wavelength range absorbed by the donor material contained in the second photoelectric conversion layer 18 becomes energy that generates hole-electron pairs, and is less likely to reach the coating material contained in the first photoelectric conversion layer 15.

[0172] The donor material and the acceptor material contained in the second photoelectric conversion layer 18 are not particularly limited as long as they are materials capable of forming a mixed film having the above-mentioned transparency. From the viewpoint of showing a high absorption coefficient in the wavelength region from ultraviolet light to near infrared light and functioning well as a donor, for example, quinacridone, phthalocyanine, naphthalocyanine, quinacridone derivatives, phthalocyanine derivatives, and naphthalocyanine derivatives can be mentioned as the donor material. In addition, the acceptor material may be Alq3 (tris(8-quinolinolato)aluminum), which is a material showing a high light absorption coefficient in the range of 300 nm to 500 nm. The donor material contained in the second photoelectric conversion layer 18 may be a single material, or multiple types of donor materials may be contained in the second photoelectric conversion layer 18. For example, by using multiple types of donor materials with different absorption spectra, the light transmittance in a wider wavelength range can be reduced.

[0173] (Embodiment 4) Next, a fourth embodiment will be described. The fourth embodiment differs from the first embodiment in that a first light-shielding donor material is used as the first light-shielding body instead of an optical filter. The following description will focus on the differences from the first embodiment, and the description of the commonalities will be omitted or simplified.

[0174] [Photoelectric conversion section configuration] Fig. 14 is a schematic cross-sectional view showing a cross-sectional structure of a plurality of pixels 10c of the imaging device 100 according to the present embodiment. As shown in Fig. 14, the pixel 10c is different from the pixel 10 according to the first embodiment in that the pixel 10c does not include the optical filter 16 and includes a photoelectric conversion unit 13c instead of the photoelectric conversion unit 13.

[0175] The photoelectric conversion unit 13c includes a plurality of pixel electrodes 11, a counter electrode 12, and a first photoelectric conversion layer 15a located between the plurality of pixel electrodes 11 and the counter electrode 12. In this embodiment, the counter electrode 12, the first photoelectric conversion layer 15a, and the plurality of pixel electrodes 11 are arranged in this order from the light incident side of the imaging device 100. The first photoelectric conversion layer 15a includes semiconductor quantum dots, a coating material, and a first light-shielding donor material. That is, the first light-shielding donor material is located in the first photoelectric conversion layer 15a. The first light-shielding donor material is an example of a first material. The first light-shielding body according to this embodiment includes the first light-shielding donor material. The first photoelectric conversion layer 15a may further include an acceptor material that functions as an acceptor for the semiconductor quantum dots and the first light-shielding donor material.

[0176] The first light-blocking donor material receives incident light and generates hole-electron pairs. The first light-blocking donor material, for example, functions as a donor to the acceptor material and is a material different from the semiconductor quantum dots.

[0177] The first light-blocking donor material has a non-zero optical absorptance at at least a portion of the second wavelength range. For example, the first light-blocking donor material has a non-zero optical absorptance at wavelengths in the second wavelength range that include a wavelength at which the covering material exhibits a maximum optical absorptance. For example, the first light-blocking donor material has a non-zero optical absorptance at all wavelengths in the second wavelength range. The optical absorption coefficient of the first light-blocking donor material may be equal to or greater than the optical absorption coefficient of the covering material in the second wavelength range.

[0178] The first light-blocking donor material absorbs light with a wavelength of, for example, 1050 nm or less. This makes it difficult for the coating material to absorb light in the wavelength range from near infrared to visible light. The first light-blocking donor material may also absorb light with a wavelength of 700 nm or less.

[0179] In this embodiment, light in the second wavelength range is incident on the first photoelectric conversion layer 15a and may be absorbed by the covering material. However, light in the second wavelength range may also be absorbed by the first light-blocking donor material, and the light absorbed by the first light-blocking donor material becomes energy that generates hole-electron pairs and is not absorbed by the covering material. Therefore, by including the first light-blocking donor material in the first photoelectric conversion layer 15a, the probability that the covering material will absorb light and generate fluorescence is reduced.

[0180] The greater the amount of the first light-blocking donor material relative to the coating material contained in the first photoelectric conversion layer 15a, the lower the probability that the coating material will absorb light and emit fluorescence. For example, if the first photoelectric conversion layer 15a contains equal amounts of the coating material and the first light-blocking donor material and the coating material and the first light-blocking donor material have the same light absorption coefficient in the second wavelength range, the probability that light in the second wavelength range will be absorbed by the coating material will be half that in the absence of the first light-blocking donor material.

[0181] The first light-blocking donor material has the above-mentioned light absorption characteristics and functions as a donor for the acceptor material, for example. Examples of the first light-blocking donor material include quinacridone, phthalocyanine, naphthalocyanine, quinacridone derivatives, phthalocyanine derivatives, and naphthalocyanine derivatives.

[0182] (Embodiment 5) Next, the fifth embodiment will be described. The fifth embodiment differs from the first embodiment in that a second light shield is used instead of the first light shield. The second light shield absorbs or reflects light of at least a part of the wavelengths in the third wavelength range. The second light shield is located in the first photoelectric conversion layer or between the first photoelectric conversion layer and the plurality of pixel electrodes. Details of the second light shield will be described later with various examples. The following mainly describes the differences from the first embodiment, and the description of the commonalities will be omitted or simplified.

[0183] [Photoelectric conversion section configuration] Fig. 15 is a schematic cross-sectional view showing the cross-sectional structure of a plurality of pixels 10d of the imaging device 100 according to the present embodiment. As shown in Fig. 15, the pixel 10d is different from the pixel 10 according to the first embodiment in that the pixel 10d does not include the optical filter 16 and includes a photoelectric conversion unit 13d instead of the photoelectric conversion unit 13.

[0184] The photoelectric conversion unit 13d includes a plurality of pixel electrodes 11, a counter electrode 12, and a first photoelectric conversion layer 15b located between the plurality of pixel electrodes 11 and the counter electrode 12. In this embodiment, the counter electrode 12, the first photoelectric conversion layer 15b, and the plurality of pixel electrodes 11 are arranged in this order from the light incident side of the imaging device 100. The first photoelectric conversion layer 15b ,half The first photoelectric conversion layer 15b includes a conductive quantum dot, a coating material, and a second light-shielding donor material. That is, the second light-shielding donor material is located in the first photoelectric conversion layer 15b. The second light-shielding donor material is an example of a second material. The second light-shielding body according to the present embodiment includes the second light-shielding donor material. The first photoelectric conversion layer 15b may further include an acceptor material that functions as an acceptor for the semiconductor quantum dots and the second light-shielding donor material.

[0185] The second light-blocking donor material generates hole-electron pairs upon receiving incident light. The second light-blocking donor material, for example, functions as a donor to the acceptor material and is a material different from the semiconductor quantum dots.

[0186] The second light-blocking donor material has a non-zero light absorptance in at least a part of the third wavelength range, which is the wavelength range of the fluorescence emitted by the coating material. Light-shielding donor The material has a non-zero optical absorptivity in a third wavelength range including the wavelength at which the coating material exhibits maximum fluorescence intensity. Light-shielding donor The material has a non-zero optical absorptance at all wavelengths in the third wavelength range.

[0187] Second Light-shielding donor The material absorbs light having a wavelength of, for example, 1150 nm or less. This makes it difficult for light having a wavelength range from near infrared to visible light to reach the semiconductor substrate 20. Light-shielding donor The material may absorb light at wavelengths below 750 nm.

[0188] In this embodiment, light in the second wavelength range is incident on the first photoelectric conversion layer 15b and may be absorbed by the coating material. When the coating material absorbs light in the second wavelength range, the coating material emits fluorescence. However, since the second light-blocking donor material has a non-zero light absorptance in the third wavelength range, it absorbs a part or all of the fluorescence emitted by the coating material.

[0189] The fluorescence emitted by the coating material absorbed in the second light-shielding donor material becomes energy that generates hole-electron pairs, and the generated electrons are then separated from the second light-shielding donor material by, for example, the acceptor material, causing the fluorescence to disappear. Therefore, the amount of fluorescence that can reach the semiconductor substrate 20 is reduced compared to when the second light-shielding donor material is not present. The greater the amount of the second light-shielding donor material relative to the coating material contained in the first photoelectric conversion layer 15b, the lower the probability that the fluorescence emitted by the coating material will reach the semiconductor substrate 20.

[0190] The second light-blocking donor material has the above-mentioned light absorption characteristics and functions as a donor for the acceptor material, for example. Examples of the second light-blocking donor material include quinacridone, phthalocyanine, naphthalocyanine, quinacridone derivatives, phthalocyanine derivatives, and naphthalocyanine derivatives.

[0191] (Embodiment 6) Next, the sixth embodiment will be described. The sixth embodiment differs from the first embodiment in that a second light shielding body is used instead of the first light shielding body. The sixth embodiment also differs from the fifth embodiment in that a second light shielding body is used as the second light shielding body instead of the second light shielding donor material. The following description will focus on the differences with the first and fifth embodiments, and the description of the commonalities will be omitted or simplified.

[0192] [Photoelectric conversion section configuration] Fig. 16 is a schematic cross-sectional view showing a cross-sectional structure of a plurality of pixels 10e of the imaging device 100 according to the present embodiment. As shown in Fig. 16, the pixel 10e is different from the pixel 10 according to the first embodiment in that the pixel 10e does not include the optical filter 16 and includes a photoelectric conversion unit 13e instead of the photoelectric conversion unit 13.

[0193] The photoelectric conversion unit 13e includes a plurality of pixel electrodes 11, a counter electrode 12, a first photoelectric conversion layer 15 located between the plurality of pixel electrodes 11 and the counter electrode 12, and a second charge transport layer 19 located between the first photoelectric conversion layer 15 and the plurality of pixel electrodes 11. In this embodiment, the counter electrode 12, the first photoelectric conversion layer 15, the second charge transport layer 19, and the plurality of pixel electrodes 11 are arranged in this order from the light incidence side of the imaging device 100. That is, the second charge transport layer 19 is arranged on the semiconductor substrate 20 side of the first photoelectric conversion layer 15. The second light shield according to this embodiment includes the second charge transport layer 19.

[0194] 16, the second charge transport layer 19 is disposed between and in contact with the first photoelectric conversion layer 15 and the plurality of pixel electrodes 11. The second charge transport layer 19 has a function of transporting the charges collected by the pixel electrodes 11 among the positive charges or negative charges generated in the first photoelectric conversion layer 15.

[0195] The second charge transport layer 19 has a non-zero light absorptance at at least a part of the wavelengths in the third wavelength range. For example, the second charge transport layer 19 has a non-zero light absorptance at wavelengths in the third wavelength range including the wavelength at which the coating material exhibits the maximum fluorescence intensity. For example, the second charge transport layer 19 has a non-zero light absorptance at all wavelengths in the third wavelength range. For example, the second charge transport layer 19 does not substantially transmit light in the third wavelength range.

[0196] The second charge transport layer 19 absorbs light with a wavelength of, for example, 1150 nm or less. This makes it difficult for light with a wavelength range from near infrared to visible light to reach the semiconductor substrate 20. The second charge transport layer 19 may also absorb light with a wavelength of 750 nm or less.

[0197] The transmittance of the second charge transport layer 19 depends on the light absorption coefficient of the material constituting the second charge transport layer 19 and the thickness of the second charge transport layer 19 .

[0198] For example, the absorption spectrum and transmittance when C70 exhibiting negative charge transport properties is used as the second charge transport layer 19 are as described in the second embodiment with reference to FIG. 9 and FIG. 10. As shown in FIG. 10, the transmittance of a C70 layer having a thickness of 400 nm or more for light having a wavelength of 600 nm or less is 5% or less, and the transmittance of a C70 layer having a thickness of 600 nm or more for light having a wavelength of 600 nm or less is 1% or less. C70 also has the function of transporting negative charges. Therefore, in an imaging device in which the pixel electrode 11 collects negative charges, the C70 layer functions as a charge transport layer and also serves to reduce the proportion of light having a wavelength of 600 nm or less that reaches the semiconductor substrate 20.

[0199] The charge transport material of the second charge transport layer 19 is not particularly limited as long as it is a material having the above-mentioned light transparency. In an image pickup device in which the pixel electrode 11 collects negative charges, the charge transport material may be, for example, fullerene and fullerene derivatives such as PCBM, perylene derivatives such as PTCDA and PTCBI, and BT-CIC and CO iExamples of the electron transport material include a non-fullerene-based low-bandgap organic semiconductor such as 8DFIC, which has an energy of the lowest unoccupied molecular orbital level based on the vacuum level of approximately 3.8 eV or more. On the other hand, examples of the charge transport material include hole transport materials, such as quinacridone derivatives, polyacene derivatives, phthalocyanine derivatives, cyanine derivatives, naphthalocyanine derivatives such as SnNcCl2, benzothiadiazole derivatives, and benzobisthiadiazole derivatives, which have an energy of the highest occupied molecular orbital level based on the vacuum level of approximately 5.4 eV or less, in an imaging device in which the pixel electrode 11 collects positive charges. The second charge transport layer 19 may be composed of a single type of material or may be composed of multiple types of materials. For example, by mixing multiple materials with different absorption spectra, the light transmittance can be reduced in a wider wavelength range. The second charge transport layer 19 may also be composed of a mixture of a charge transport material and a non-charge transport material. For example, a material that functions to transport charges may be selected as the charge transporting material, and a material that has a desired absorption spectrum, such as absorbing light in a third wavelength range, may be selected as the non-charge transporting material.

[0200] As described above, the second charge transport layer 19 is located closer to the semiconductor substrate 20 than the first photoelectric conversion layer 15, and absorbs or reflects at least a part of the light in the third wavelength range. This makes it possible to reduce the light in the third wavelength range that reaches the charge accumulation region or the control circuit formed of the impurity region of the semiconductor substrate. This makes it possible to reduce noise and the like that occurs when the charge accumulation region or the like absorbs the fluorescence emitted by the coating material.

[0201] (Embodiment 7) Next, a seventh embodiment will be described. The seventh embodiment differs from the first embodiment in that a second light shield is used in addition to the first light shield. The following description will focus on the differences from the first embodiment, and the description of the commonalities will be omitted or simplified.

[0202] [Photoelectric conversion section configuration] Fig. 17 is a schematic cross-sectional view showing a cross-sectional structure of a plurality of pixels 10f of the imaging device 100 according to the present embodiment. As shown in Fig. 17, the pixel 10f is different from the pixel 10 according to the first embodiment in that the pixel 10f includes a photoelectric conversion unit 13f instead of the photoelectric conversion unit 13.

[0203] The photoelectric conversion unit 13f includes a plurality of pixel electrodes 11, a counter electrode 12, and a first photoelectric conversion layer 15b located between the plurality of pixel electrodes 11 and the counter electrode 12. An optical filter 16 is provided on the counter electrode 12 of the photoelectric conversion unit 13f. In this embodiment, the optical filter 16, the counter electrode 12, the first photoelectric conversion layer 15b, and the plurality of pixel electrodes 11 are arranged in this order from the light incidence side of the imaging device 100. That is, the optical filter 16 is arranged on the light incidence side of the first photoelectric conversion layer 15b. The first photoelectric conversion layer 15b includes semiconductor quantum dots, a coating material, and a second light-shielding donor material, as in the fifth embodiment. The first photoelectric conversion layer 15b may further include an acceptor material that functions as an acceptor for the semiconductor quantum dots and the second light-shielding donor material.

[0204] The imaging device 100 according to the present embodiment includes a first light shield and a second light shield. The first light shield according to the present embodiment includes an optical filter 16, and the second light shield according to the present embodiment includes a second light-shielding donor material. Therefore, the optical filter 16 absorbs or reflects light in the second wavelength range, and can prevent the coating material from emitting fluorescence. Even if the coating material emits fluorescence, the second light-shielding donor material absorbs the fluorescence, and can prevent the fluorescence from reaching the semiconductor substrate 20.

[0205] (Other embodiments) Although the imaging device according to one or more aspects has been described based on the embodiments, the present disclosure is not limited to these embodiments. As long as it does not deviate from the gist of the present disclosure, various modifications conceived by a person skilled in the art to the present embodiment and forms constructed by combining components of different embodiments are also included within the scope of the present disclosure.

[0206] For example, in the above embodiment, the first photoelectric conversion layer is a semiconductor quantum dot layer mixed with a coating material for semiconductor quantum dots, such as a ligand material or a matrix material of a π-conjugated compound, but is not limited thereto. The first photoelectric conversion layer may be a photoelectric conversion layer containing both semiconductor quantum dots and an acceptor material that functions as an acceptor for the semiconductor quantum dots, or may be a two-layered photoelectric conversion layer in which a layer containing semiconductor quantum dots and a layer containing an acceptor material are joined together.

[0207] In addition, for example, in the sixth embodiment, the second charge transport layer is disposed as the second light shield, but this is not limiting. Instead of the second charge transport layer as the second light shield, a third photoelectric conversion layer that absorbs light of at least a part of the wavelengths in the third wavelength range may be disposed.

[0208] Also, for example, the imaging device may be one in which a plurality of first light shields and second light shields used in each of the embodiments are combined. [Industrial Applicability]

[0209] The imaging device according to the present disclosure can be applied to high-sensitivity imaging using infrared wavelengths, etc. in various camera systems and sensor systems, such as medical cameras, surveillance cameras, vehicle-mounted cameras, distance measuring cameras, microscope cameras, drone cameras, and robot cameras. [Explanation of symbols]

[0210] 10, 10a, 10b, 10c, 10d, 10e, 10f pixels 11 Pixel electrode 12 Counter electrode 13, 13a, 13b, 13c, 13d, 13e, 13f Photoelectric conversion section 14 Signal detection circuit 15, 15a, 15b First photoelectric conversion layer 16 Optical Filters 17 First charge transport layer 18 Second photoelectric conversion layer 19 Second charge transport layer 20 Semiconductor substrate 20t Element isolation area 24 Signal detection transistor 24d, 24s, 26s, 28d, 28s impurity region 24g, 26g, 28g Gate electrode 26 Address transistor 28 Reset transistor 32 Voltage supply circuit 34 Reset voltage source 36 Vertical scanning circuit 37 Column signal processing circuit 38 Horizontal signal readout circuit 40 Power line 41 Charge storage node 42 Bias control line 44 Reset voltage line 46 Address Control Line 47 Vertical signal line 48 Reset control line 49 Horizontal common signal line 50 Interlayer insulation layer 52 Plug 53 Wiring 54, 55 Contact plug 56 wiring layer 100 Imaging device 200A, 200B Semiconductor quantum dots 210 cores 220 Shell 230 Ligand

Claims

1. A semiconductor substrate; a plurality of pixel electrodes located above the semiconductor substrate and each of the pixel electrodes being electrically connected to the semiconductor substrate; a counter electrode located above the plurality of pixel electrodes; a first photoelectric conversion layer located between the plurality of pixel electrodes and the counter electrode; At least one first light shield located in the first photoelectric conversion layer or above the first photoelectric conversion layer; Equipped with The first photoelectric conversion layer is A semiconductor quantum dot having a characteristic of absorbing light in a first wavelength range; a coating material that coats the semiconductor quantum dots and has a property of absorbing light in a second wavelength range and emitting fluorescence in a third wavelength range; Including, The at least one first light blocking body absorbs or reflects light having at least a part of a wavelength in the second wavelength range. Imaging device.

2. the at least one first light shield is located above the counter electrode and includes an optical filter that absorbs or reflects the light having at least a portion of the wavelength in the second wavelength range; The imaging device according to claim 1 .

3. the at least one first light shield is located between the first photoelectric conversion layer and the counter electrode and includes a first charge transport layer that absorbs the light having at least a portion of the wavelength in the second wavelength range; 3. The imaging device according to claim 1.

4. the at least one first light shielding body is located between the first photoelectric conversion layer and the counter electrode and includes a second photoelectric conversion layer that absorbs the light having at least a part of the wavelength in the second wavelength range; The imaging device according to claim 1 .

5. the at least one first light blocking body includes a first material that absorbs the light at least in the portion of the second wavelength range, the first material being different from the semiconductor quantum dots; The first material is located in the first photoelectric conversion layer. The imaging device according to claim 1 .

6. The at least one first light blocking body transmits light having at least a part of a wavelength in the first wavelength range. The imaging device according to claim 1 .

7. The at least one first light blocking body absorbs or reflects light having a wavelength of 1050 nm or less. The imaging device according to claim 1 .

8. Further comprising at least one second light shield located in the first photoelectric conversion layer or between the first photoelectric conversion layer and the plurality of pixel electrodes, the second light shield absorbing or reflecting light having at least a part of a wavelength in the third wavelength range. The imaging device according to claim 1 .

9. A semiconductor substrate; a plurality of pixel electrodes located above the semiconductor substrate and each of the pixel electrodes being electrically connected to the semiconductor substrate; a counter electrode located above the plurality of pixel electrodes; a first photoelectric conversion layer located between the plurality of pixel electrodes and the counter electrode; at least one second light shielding body located in the first photoelectric conversion layer or between the first photoelectric conversion layer and the plurality of pixel electrodes; Equipped with The first photoelectric conversion layer is A semiconductor quantum dot having a characteristic of absorbing light in a first wavelength range; a coating material that coats the semiconductor quantum dots and has a property of absorbing light in a second wavelength range and emitting fluorescence in a third wavelength range; Including, The at least one second light blocking body absorbs or reflects light having at least a part of a wavelength in the third wavelength range. Imaging device.

10. the at least one second light blocking body includes a second material that absorbs the light at least in the portion of the third wavelength range, the second material being different from the semiconductor quantum dots; The second material is located within the first photoelectric conversion layer.

10. The imaging device according to claim 8.

11. the at least one second light shield is located between the first photoelectric conversion layer and the plurality of pixel electrodes and includes a second charge transport layer that absorbs the light having at least a portion of the wavelength in the third wavelength range; The imaging device according to claim 8 .

12. the coating material includes at least one selected from the group consisting of a matrix material and a ligand material having π-conjugation; The matrix material comprises at least one selected from the group consisting of a semiconducting polymer, a semiconducting copolymer, a semiconducting oligomer, a small molecule semiconductor, a perovskite material, and a double perovskite material; The imaging device according to claim 1 .

13. The first photoelectric conversion layer includes a third material that functions as an acceptor for the semiconductor quantum dots. The imaging device according to claim 1 .

14. The first photoelectric conversion layer includes a third material that functions as an acceptor for the semiconductor quantum dots and the first material. The imaging device according to claim 5 .

15. The first photoelectric conversion layer includes a third material that functions as an acceptor for the semiconductor quantum dots and the second material. The imaging device according to claim 10.

16. The semiconductor substrate comprises silicon. The imaging device according to claim 1 .

Images