Infrared sensor, nanomaterial, dispersion liquid, and method for manufacturing infrared sensor

Abstract

The purpose of the present invention is to provide: an infrared sensor in which a combination of preferred materials for an electron transport layer and a hole transport layer can be selected; and a method for manufacturing the infrared sensor. This infrared sensor is provided with an electron transport layer, a light absorption layer, and a hole transport layer, and is characterized in that the light absorption layer contains quantum dots, the electron transport layer contains at least one of ZnO, MgZnO, and SnO, and the hole transport layer or hole extraction layer contains at least one of NiO and MoO. In the invention, preferably, the oxygen defect of the metal oxide forming the electron transport layer and the hole transport layer is smaller than that of the body material.

Description

Technical Field

[0001] This invention relates to an infrared sensor having a light-absorbing layer that absorbs infrared light. Background Technology

[0002] Patent Document 1 disclosed below discloses a photoelectric conversion element having a photoelectric conversion layer that receives light in the near-infrared region and performs photoelectric conversion.

[0003] The photoelectric conversion element consists of a transparent electrode, an electron transport layer, a photoelectric conversion layer, a hole transport layer, and a metal electrode stacked sequentially.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2021-012906 Summary of the Invention

[0005] The problem that the invention aims to solve However, in the invention described in Patent Document 1, there is no description of a preferred combination of materials associated with the absorption edge, the electron transport layer, and the hole transport layer.

[0006] The present invention was made in view of the above-mentioned problems, and its object is to provide an infrared sensor capable of selecting a preferred combination of materials for the electron transport layer and the hole transport layer.

[0007] Methods for solving problems The present invention is characterized in that it is an infrared sensor having an electron transport layer, a light absorption layer and a hole transport layer, wherein the light absorption layer comprises quantum dots, the electron transport layer comprises at least one of ZnO, MgZnO or SnO, and the hole transport layer or hole extraction layer comprises at least one of NiO or MoO.

[0008] The present invention is characterized in that the material used in the electronic transmission layer constituting the infrared sensor described above has a slope greater than that of the bulk material when the absorption edge is plotted using the Tauc method.

[0009] The present invention is characterized in that the polydispersity index of the dispersion of the material described above is less than 0.1 in the DLS measurement.

[0010] Invention Effects According to the infrared sensor of the present invention, the absorption edge can be greatly increased by combining the materials constituting the electron transport layer and the hole transport layer. Attached Figure Description

[0011] Figure 1 This is a perspective view of an infrared camera device equipped with the infrared sensor of this embodiment.

[0012] Figure 2 This is a partial cross-sectional view of the infrared sensor of this embodiment.

[0013] Figure 3 is a schematic diagram of the quantum dot in this embodiment.

[0014] Figure 4 shows the energy level diagram when using quantum dots with a core-shell structure.

[0015] Figure 5 This is the synthesis process of ZnO.

[0016] Figure 6 This is the synthesis process of MgZnO.

[0017] Figure 7 This is the synthesis process of SnOx.

[0018] Figure 8 This is the synthesis process for NiOx.

[0019] Figure 9 This is the synthesis process of MnOx.

[0020] Figure 10A This is a graph representing the UV spectrum. Figure 10B It is a graph representing the band gap energy.

[0021] Figure 11 This is the synthesis process of NiO.

[0022] Figure 12 This is the XRD pattern of NiO.

[0023] Figure 13 This represents the UV spectrum of NiO.

[0024] Figure 14 This is a curve representing the band gap energy of NiO (Tauc plot).

[0025] Figure 15 This is the XANES spectrum used in Ni valence evaluation.

[0026] Figure 16 It is a graph showing the relationship between particle size and scattering intensity distribution in Examples 1 to 3. Detailed Implementation

[0027] Hereinafter, one embodiment of the present invention (hereinafter referred to as "Embodiment") will be described in detail. Furthermore, the present invention is not limited to the following embodiment, and various modifications can be made within its scope.

[0028] Figure 1 This is a perspective view of an infrared camera device equipped with the infrared sensor of this embodiment. Figure 1 As shown, the infrared camera device 100 is configured with an infrared sensor 101 and a circuit board 102.

[0029] like Figure 1 As shown, the infrared sensor 101 is flip-chip bonded to the circuit board 102 via multiple bumps 104.

[0030] For example, the infrared sensor 101 has a QDIP (Quantum Dot Infrared Photodetector) array with multiple pixels arranged in a row. Bumps 104 are provided on each pixel. Furthermore, in this embodiment, the number of pixels is not limited.

[0031] Figure 1 The surface 101a of the infrared sensor 101 shown is the light-receiving surface. If infrared light is shone from the direction of the arrow, the charge carriers in the quantum dots sealed in the infrared sensor 101 are excited, and the infrared light is detected as a photocurrent on the circuit board 102 side.

[0032] According to this embodiment, an image sensor capable of detecting infrared light can be realized. The application of the infrared camera device 100 of this embodiment is not limited; for example, it can be used in night vision devices, heat source detection devices, security devices, and medical equipment.

[0033] Figure 2 This is a partial cross-sectional view showing an example of the infrared sensor (photoelectric conversion element) of this embodiment. Figure 2 The infrared sensor 101 shown includes a first conductive layer 41 serving as a cathode and a second conductive layer 42 serving as an anode. An electron transport layer 43, a light absorption layer 44, and a hole transport layer 45 are provided between the first conductive layer 41 and the second conductive layer 42. For example, the first conductive layer 41 is formed on a glass substrate 46. An electron extraction layer may also be provided.

[0034] In this embodiment, the electron transport layer 43 preferably comprises at least one of ZnO, MgZnO, or SnO. Additionally, the hole transport layer 45 (or hole extraction layer) preferably comprises at least one of NiO or MoO.

[0035] Furthermore, in this embodiment, it is preferable that the oxygen defects of the metal oxide constituting the electron transport layer 43 and the hole transport layer 45 (or hole extraction layer) are smaller than those of the bulk material. That is, a stoichiometric composition is preferred. According to the metal oxide synthesis process of this embodiment, oxygen defects can be suppressed.

[0036] "Bulk material" refers to a block containing the metal oxide, regardless of size or shape.

[0037] In this embodiment, the light absorption layer 44 is a layer that absorbs light incident on the infrared sensor 101 and generates electrons and holes.

[0038] The light-absorbing layer 44 contains quantum dots. Multiple quantum dots are dispersed within the light-absorbing layer 44.

[0039] The quantum dots are preferably spherical. Here, "spherical" is not limited to round, but refers to a sphericity of 0.7 or higher, preferably 0.8 or higher, and more preferably 0.9 or higher. The sphericity can be measured, for example, by image processing using an electron microscope, and by calculating 4π × (area) ÷ (perimeter) based on the observed area and perimeter of the quantum dots. 2 Calculate the sphericity. Alternatively, if the aspect ratio of the major axis to the minor axis of the observed quantum dot is 1.5 or less, preferably 1.2 or less, and more preferably 1.3 or less, it is defined as "spherical".

[0040] In this embodiment, quantum dots can be formed by liquid-phase synthesis. The quantum dots in this embodiment are preferably spherical as described above, but are not limited to this. Quantum dots synthesized by liquid-phase synthesis are spherical as described above, but they may also be formed in shapes other than spherical. Examples of shapes other than spherical include rod-shaped and dendritic shapes.

[0041] For example, in this embodiment, a resin composition in which multiple spherical quantum dots are dispersed in a resin can be used to form the light-absorbing layer 44. Here, the dispersing resin for the quantum dots is not particularly limited, and examples include polypropylene, polyethylene, polystyrene, AS resin, ABS resin, methacrylic resin, polyvinyl chloride, polyacetal, polyamide, polycarbonate, modified polyphenylene ether, polybutylene terephthalate, polyethylene terephthalate, polysulfone, polyethersulfone, polyphenylene sulfide, polyamide-imide, polymethylpentene, liquid crystal polymer, epoxy resin, phenolic resin, urea resin, melamine resin, epoxy resin, diallyl phthalate resin, unsaturated polyester resin, polyimide, polyurethane, silicone resin, cyclic olefin polymer (COP), cyclic olefin copolymer (COC), vinyl alcohol, polymethylpentene, polyvinylidene fluoride, etc.

[0042] Alternatively, in this embodiment, inkjet coating can be performed while the multiple spherical quantum dots are dissolved in a solvent. In this case, the dried quantum dot layer consists of approximately spherical quantum dots, but some solvent components may remain in the quantum dot layer.

[0043] Quantum dots have an emission wavelength of approximately 800 nm to 1600 nm. Preferably, quantum dots with such emission wavelengths include at least one of PbS, PbSe, CdHgTe, Ag₂S, Ag₂Se, Ag₂Te, AgInSe₂, AgInTe₂, CuInSe₂, CuInTe₂, and InAs. Ag₂S does not comply with the RoHS directive. Regarding PbS, a paper was published in WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim. ADVANCED MATERIALS 2003, 15. NO. 21 November 4. Regarding Ag₂S, a paper was published in ACS NANO VOL. 6 NO. 5 P3695-3702 (2012).

[0044] In this embodiment, PbS or Ag2S is preferably used as the quantum dot. Furthermore, by using Ag2S, Ag2Se, Ag2Te, AgInSe2, or AgInTe2 as the quantum dot, the fluorescence half-width in the near-infrared region can be narrowed, enabling the display of high-brightness near-infrared fluorescence.

[0045] In this embodiment, multiple quantum dots can be set as one type, or as two or more types. That is, multiple quantum dots can be made from all the same type of quantum dots, or different types of quantum dots can be used.

[0046] In this embodiment, the quantum dots are, for example, nanoparticles with a particle size of several nm to tens of nm.

[0047] like Figure 3A As shown, preferably, a plurality of organic ligands 21 are coordinated on the surface of the quantum dot 20. This suppresses the aggregation of the quantum dots 20 and allows them to exhibit the desired optical properties. The ligands that can be used for the reaction are not particularly limited; for example, the following ligands can be cited as representative ligands.

[0048] (1) Aliphatic primary amine series Oleamine: C 18 H 35 NH2, stearyl (octadecyl)amine: C 18 H 37 NH2, dodecyl (lauryl)amine: C 12 H 25 NH2, decylamine: C 10 H 21 NH2, Octylamine: C8H 17 NH2 (2) Fatty acid system Oleic acid: C 17 H33 COOH, stearic acid: C 17 H 35 COOH, palmitic acid: C 15 H 31 COOH, myristic acid: C 13 H 27 COOH, Lauric acid: C 11 H 23 COOH, Decanoic acid: C9H 19 COOH, Caprylic acid: C7H 15 COOH (3) Thiol series Octadecanthiol: C 18 H 37 SH, hexadecylthiol: C 16 H 33 SH, tetradecylthiol: C 14 H 29 SH, dodecylthiol: C 12 H 25 SH, decanethiol: C 10 H 21 SH, Octanethiol: C8H 17 SH (4) Phosphine series Trioctylphosphine: (C8H) 17 3P, triphenylphosphine: (C6H5)3P, tributylphosphine: (C4H9)3P (5) Phosphine oxide series Trioctylphosphine oxide: (C8H) 17 3P=O, Triphenylphosphine oxide: (C6H5)3P=O, Tributylphosphine oxide: (C4H9)3P=O In addition, in this embodiment, a short ligand is preferably used as the organic ligand 21. Although not limited, 3-mercaptopropionic acid (MPA) can be used as the organic ligand 21.

[0049] The ligands of the quantum dots 20 contained in the quantum dot layer are preferably shorter than those of the quantum dots 20 formed by liquid-phase synthesis.

[0050] Thus, by using short ligands in the ligands of the quantum dots 20 contained in the quantum dot layer, the roughness of the quantum dot layer can be reduced, and the extraction efficiency of electrons and holes can be improved. On the other hand, by using long ligands in the ligands when forming quantum dots 20 using liquid-phase synthesis, the dispersibility and film-forming properties can be improved.

[0051] Alternatively, after synthesizing the quantum dots 20 with long ligands via liquid-phase synthesis, the composition containing the quantum dots 20 can be replaced with short ligands (e.g., 3-mercaptopropionic acid) before or after coating.

[0052] In addition, such as Figure 3B As shown, quantum dot 20 can also be a core-shell structure having a core 20a and a shell 20b covering the surface of the core 20a. For example... Figure 3B As shown, preferably, a plurality of organic ligands 21 are coordinated on the surface of the quantum dot 20. Regarding the organic ligands 21, as described above. Figure 3B The core 20a of the quantum dot 20 shown is Figure 3A The nanoparticles shown. Therefore, the core 20a is formed, for example, from the material of the quantum dot 20 listed above.

[0053] Alternatively, the shell 20b can also be in a state of solid solution dissolved on the surface of the core 20a. Figure 3B In the diagram, the boundary between the core 20a and the shell 20b is shown by a dashed line. However, this means that the boundary between the core 20a and the shell 20b may or may not be confirmed by analysis; either case is acceptable. Furthermore, although not shown, it is preferable to have a buffer layer between the core 20a and the shell 20b. The buffer layer is a region where at least some or all of the elements constituting the core 20a are mixed with at least some or all of the elements constituting the shell 20b.

[0054] In this embodiment, the structure is formed by coating spherical quantum dots. For example, since quantum dots (especially spherical quantum dots) formed by liquid-phase synthesis are used, it has excellent sensitivity in all aspects. For example, compared with quantum dots that have undergone micro-processing, the sensitivity deviation can be reduced.

[0055] Furthermore, in this embodiment, the quantum dots preferably include at least one of PbS, PbSe, CdHgTe, Ag2S, Ag2Se, Ag2Te, AgInSe2, AgInTe2, CuInSe2, CuInTe2, and InAs. These have emission wavelengths of 800 nm to 1600 nm and are preferably suitable for use in infrared sensors.

[0056] When the quantum dot used in this embodiment has a core-shell structure, it becomes Figures 4A-4D Any energy level diagram in the [concept]. In the case of a light-emitting element, the shell of the core-shell structure is important in terms of enhancing the quantum confinement effect. In particular, [the following is preferred]. Figure 4A The type I structure shown has a higher LUMO energy in the shell than in the nucleus, and a lower HOMO energy in the shell than in the nucleus.

[0057] On the other hand, when used as a photoelectric conversion element in this embodiment, a type II structure is preferred for easy extraction of charge carriers (electrons and holes). Generally, hole mobility is lower than electron mobility, so type II (1) or (3) is preferred. Furthermore, when used as a photoelectric conversion element, quantum dots with a ligand-based core structure and no core-shell structure can also be used. In type II (1), the LUMO energy of the shell is lower than that of the core LUMO, and the HOMO energy of the shell is higher than that of the core HOMO. In type II (3), the LUMO energy of the shell is higher than that of the core LUMO, and the HOMO energy of the shell is higher than that of the core HOMO.

[0058] In this embodiment, the thickness of the light absorption layer is preferably 5 nm or more and 50 nm or less.

[0059] (Electron transport layer 43) The electron transport layer 43 is composed of an inorganic or organic material capable of transporting electrons. In this embodiment, the electron transport layer 43 comprises at least one of ZnO, MgZnO, or SnO. Two or more of these materials may also be selected. The electron transport layer 43 is particularly preferably composed of ZnO. X Nanoparticles are formed. Alternatively, Li, Mg, Al, Mn, etc., can be doped into the metal oxide. X is not limited, but is approximately 0.8 to 1.2, although the absence of oxygen defects is preferred.

[0060] Like the light absorption layer 44, the electron transport layer 43 can be formed by printing methods such as inkjet printing or by existing thin film technologies such as vacuum evaporation.

[0061] (Hole transport layer 45 or hole extraction layer) The hole transport layer 45 is composed of an inorganic or organic material that functions to transport holes. In this embodiment, the hole transport layer 45 or the hole extraction layer preferably contains at least one of NiO or MoO. Alternatively, Al2O3 or the like may be mixed into NiO, for example, in the hole transport layer 45 or the hole extraction layer. Furthermore, Li, Mg, Al, or the like may be doped into the metal oxide. Preferably, no oxygen vacancies are generated in the metal oxide constituting the hole transport layer 45 or the hole extraction layer.

[0062] The method for manufacturing an infrared sensor according to this embodiment includes: a step of forming spherical quantum dots by liquid-phase synthesis; and a step of forming a light-absorbing layer by coating a resin composition containing quantum dots.

[0063] In this embodiment, as a liquid-phase synthesis method, the element sources constituting the quantum dots can be dissolved in a solvent, and the precursor solution containing each element can be reacted using, for example, a microreactor to synthesize quantum dot particles containing the specified elements. Thus, spherical quantum dots can be obtained.

[0064] To improve the dispersion of quantum dots, long-chain ligands are preferred. Therefore, quantum dots with long-chain ligands are preferred during coating, but in device fabrication, short-chain ligands are preferred to improve the extraction efficiency of charge carriers (electrons and holes). Although not limited, short-chain ligands with 2 to 5 carbon atoms (preferably 2 to 3) can be used, for example, 3-mercaptopropionic acid.

[0065] In this embodiment, after synthesizing quantum dots using a liquid-phase synthesis method, the ligands of the quantum dots can be replaced with shorter ligands. For example, a spin coater can be used to coat a composition containing quantum dots (containing quantum dots and a solvent). Since long-chain ligands have better dispersibility, a film with good roughness can be formed; however, with long-chain ligands, carrier extraction becomes unfavorable. Therefore, for example, after coating, the short-chain ligands are detached from the coating film. Thus, the long-chain ligands are naturally replaced with short-chain ligands, and then washing is performed to remove the long-chain ligands. Alternatively, after synthesizing quantum dots using a liquid-phase synthesis method, the long-chain ligands can be replaced with short-chain ligands before coating, and then the composition containing quantum dots (which may also be a resin composition) can be coated.

[0066] In this embodiment, the electron transport layer 43 is formed by ZnO, MgZnO, or SnO. The synthesis process of these metal oxides will be described below.

[0067] Figure 5 This is the synthesis process of ZnO. For example... Figure 5 As shown, Zn(OAc)2·2H2O (6.22 g, 28.3 mmol) and 0.5 wt% hydrated methanol (198.8 g, 251 ml) were mixed in a flask, and the temperature was raised to 60 °C.

[0068] Next, KOH / 0.5wt% hydrated methanol was added to the flask at a rate of 13 ml per minute, and this addition was continued for 10 minutes. Then, the temperature was maintained at 60°C for 2 hours.

[0069] Next, after cooling, the mixture was transferred to two centrifuge tubes and centrifuged at 7000 pm for 5 minutes. Then, the supernatant was drained from each tube, and the mixture was sonicated before being centrifuged again at 7000 pm for 5 minutes. This process of draining the supernatant, sonicating, and centrifuging was repeated once more.

[0070] Next, drain the supernatant and proceed with the ultrasonic process. Between draining the supernatant and the ultrasonic process, add 5 ml of ethanol and 0.5 ml of aminoethanol to each centrifuge tube. Then, store in the dark overnight.

[0071] Next, transfer the contents to two other centrifuge tubes and add approximately 35-40 ml of ethyl acetate to each tube. Centrifuge at 5500 pm for 5 minutes. Then, drain the supernatant from each centrifuge tube and transfer the contents to a G-BOX container for dispersion using a vortex mixer.

[0072] Next, the sample was transferred through a 0.54 μm filter to a 50 ml tube, from which 0.7 ml was aliquoted, and the remainder was stored in a G-BOX. The aliquoted 0.7 ml was used for concentration determination, and the concentration and dilution ratio were calculated. Based on this calculation, the G-BOX was adjusted with dehydrated ethanol to achieve the calculated dilution ratio. The completed G-BOX was then stored. 1.6 ml was aliquoted from this completed G-BOX for DLS, UV, PL, and concentration analysis.

[0073] Figure 6 This is the synthesis process of MgZnO. For example... Figure 6 As shown, first, anhydrous ethanol (30 mL) was prepared, and Zn(OAc)₂·2H₂O (560 mg, 2.55 mmol) and Mg(OAc)₂·4H₂O (96.5 mg, 0.45 mmol) were added to it. The mixture was stirred at room temperature for 30 minutes. Next, KOH (309 mg, 5.5 mmol) / anhydrous ethanol (20 mL) was added. The mixture was then stirred at room temperature for 1 hour. Next, hexane (80 mL) was added. The mixture became cloudy and white. Ethanolamine (1 mL) was added to the mixture until dissolved, and hexane was further added to precipitate the solid, which was then dispersed with ethanol. This yielded MgZnO with a particle size of approximately 4.2 nm. The band gap energy E of MgZnO is... g It is 3.79 eV.

[0074] Figure 7 This is the synthesis process for SnOx. For example... Figure 7 As shown, prepare ethylene glycol (100 mL), and mix it with SnCl4·5H2O (11.57 g, 0.33 mol), acetic acid (10 mL), and 30% tetramethylammonium hydroxide aqueous solution (25 mL). Stir at 50°C for 30 minutes. Then, raise the temperature to 160°C and stir for 4 hours.

[0075] Next, wash with ethanol-ethyl acetate, and add 2 ml of ethanolamine to disperse it in ethanol.

[0076] In this embodiment, the hole transport layer 45 or the hole extraction layer is formed of NiO or MoO. The synthesis process of these metal oxides will be described below.

[0077] Figure 8 This is the synthesis process for NiOx. For example... Figure 8 As shown, 100 mL of DMSO was prepared, and Ni(NO3)2·6H2O (10 mmol) and KOH (673 mg, 12 mmol) / 100 mL of anhydrous ethanol were mixed into it. The mixture was stirred at room temperature for 30 minutes. Next, after washing with ethanol, 150 mL of DMSO was mixed in and stirred at 160 °C for 4 hours. Then, the mixture was washed with ethanol-ethyl acetate, and 0.2 mL of ethanolamine was added to disperse it in ethanol. A dark gray precipitate was obtained.

[0078] Figure 9 This is the synthesis procedure for MoOx. In a sealed tube, 1-octadecene and octanoic acid (total volume 60 mL, 1-octadecene:octanoic acid volume ratio = 1:9), MoO2(acac)2 (244.62 mg, 0.75 mmol), and acetic acid (10 mL) are mixed and stirred at 50°C for 30 minutes. Next, the temperature is raised to 180°C and stirred for 40 minutes. Then, n-octane (250 mL) is added, yielding a deep blue precipitate. This precipitate is then dispersed in ethanol.

[0079] According to the synthesis process of this embodiment, metal oxides that do not produce oxidation defects can be obtained. Moreover, by using the electron transport layer and hole transport layer of this embodiment, the absorption edge in the infrared region can be effectively increased dramatically.

[0080] Figure 10A This is a graph representing the UV spectrum. Figure 10B This is a curve representing the band gap energy (Tauc plot). In the experiment, the Mg doping amount of MgZnO was varied. Furthermore, the MgZnO used in the experiment was freshly synthesized MgZnO dispersed in DEGME. As shown in Figure 10, the band gap energy E increases with increasing Mg doping amount. g Increase.

[0081] Figure 11 This is the synthesis process for NiO. Additionally, it shows the synthesis process for NiO. Figure 8 Different synthesis processes. That is, such as Figure 11As shown, Ni(NO3)2·6H2O, dimethyl sulfoxide, and KOH / anhydrous ethanol solution were mixed and stirred at room temperature for 30 minutes. This yielded a green precipitate. This precipitate was mixed with DMSO and kept at 160°C for 3 hours, followed by washing with ethanol / ethyl acetate. Then, ethanolamine was added to disperse it in ethanol.

[0082] Figure 12 This is the XRD pattern of NiO. The NiO used in the experiment was obtained through... Figure 11 It is obtained through a synthetic process. For example... Figure 12 NiO was observed. On the other hand, Ni was not observed, indicating that appropriate synthesis was carried out.

[0083] Figure 13 Indicates the UV spectrum of NiO, Figure 14 It is a curve representing the band gap energy (Tauc plot).

[0084] like Figure 14 As shown, the slope of the Tauc plot of the absorbing edge is greater than that of the bulk material. This indicates that the absorbing edge can be significantly increased. Furthermore, as... Figure 14 As shown, when using nanoparticles, the Tauc plot exhibits a smaller tail and a more rapid ascent compared to the bulk material. In this embodiment, all electron transport materials are semiconductors; therefore, among all electron transport materials, the slope of the Tauc plot is greater than that of the bulk material.

[0085] In addition, such as Figure 14 As shown, within regions A and B enclosed by the tangent representing the slope, the plotted curve, and the horizontal axis, region A of the nanoparticles is smaller than region B of the bulk material. The smaller this region, the fewer oxygen vacancies, thus proving that the oxygen vacancies in the nanoparticles are smaller than those in the bulk material.

[0086] <Regarding the Ni valence of NiO> Using standard samples with known valences (NiO: divalent, LiNiO2: trivalent), a standard curve was constructed to plot the rising position of the XANES spectrum and the valence of Ni. In the experiment, BL08W was used as the beamline, and transmission method was employed for the determination.

[0087] Next, the Ni valence was evaluated using the XANES spectrum of NiO synthesized by the method described in this embodiment. The experimental results are shown below. Figure 15 .

[0088] like Figure 15As shown, the XANES spectrum shifts due to the change in valence. Furthermore, it is known that since the XANES spectrum of the embodiment exists between the divalent NiO and trivalent LiNiO2, the Ni valence of the NiO in the embodiment is between 2 and 3. Because it is closer to the divalent NiO side, the Ni valence of the embodiment is greater than 2 and less than 2.5, preferably 2.1 or higher and 2.4 or lower. Additionally, in Figure 15 In the embodiment, the Ni valence is predicted to be around 2.2. This proves that NiO in this embodiment is a hole carrier.

[0089] Furthermore, the polydispersity index of the metal oxide dispersion used in the electron transport layer of this embodiment is less than 0.1 during DLS measurement. Dynamic light scattering (DLS) is suitable for nanoparticles dispersed in a liquid. DLS measurement is a method for calculating particle size by measuring the diffusion rate of nanoparticles moving due to Brownian motion.

[0090] To represent the width of the particle size distribution, the polydispersity index (PDI) is used. In the experiment, ZnO particles were fabricated as a metal oxide used in the electron transport layer. Figure 16 Table 2 shows the relationship between particle size and scattering intensity distribution in each embodiment. As shown in Table 2, the polydispersity index is less than 0.1 in Examples 1 to 3. Therefore, it can be seen that all particles measured in each embodiment have approximately the same particle size.

[0091] Metal oxides such as ZnO or NiO exist in the infrared sensor in the form of a film. In this embodiment, the polydispersity index is made less than 0.1 as described above to improve dispersibility, but the performance of the film can be defined by the surface roughness after film formation.

[0092] That is, the surface roughness Ra (arithmetic mean roughness) of the film is preferably less than 1.0 nm. The surface roughness (Ra) can be analyzed by AFM measurement or the like.

[0093] Industrial availability According to the present invention, infrared light detection is possible. The infrared sensor of the present invention can be applied to night vision devices, heat source detection devices, security devices, medical equipment, etc.

[0094] This application is based on Japan Patent Application No. 2023-170555, filed on September 29, 2023. Its entire contents are contained herein.

Claims

1. An infrared sensor, characterized in that, It is an infrared sensor with an electron transport layer, a light absorption layer, and a hole transport layer. The light-absorbing layer contains quantum dots. The electron transport layer comprises at least one of ZnO, MgZnO, or SnO. The hole transport layer or hole extraction layer comprises at least one of NiO or MoO.

2. The infrared sensor according to claim 1, characterized in that, The oxygen defects in the metal oxides constituting the electron transport layer and the hole transport layer are smaller than those in the bulk material.

3. The infrared sensor according to claim 1, characterized in that, The quantum dots contain organic ligands on their surface, the organic ligands being 3-mercaptopropionic acid.

4. The infrared sensor according to claim 1, characterized in that, The quantum dot contains ligands on its surface, and the ligands have 2 or more but less than 5 carbon atoms.

5. A nanoparticle material, characterized in that, The material used in the electronic transmission layer constituting the infrared sensor of claim 1 has a slope greater than that of the bulk material when the absorption edge is plotted using the Tauc method.

6. The dispersion of the material according to claim 5, characterized in that, The polydispersity index during DLS measurement was less than 0.

1.

7. The method for manufacturing the infrared sensor according to claim 1, characterized in that, In the process of forming the light-absorbing layer, ligands are exchanged after coating the composition containing the quantum dots.

8. The method for manufacturing a display device according to claim 7, characterized in that, When synthesizing the quantum dots by liquid-phase synthesis, the quantum dots with ligand lengths are synthesized and then replaced with shorter ligands before or after coating the composition containing the quantum dots.

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