Light-emitting device, light-emitting apparatus, light-emitting module, electronic device, and lighting apparatus

Abstract

Provided is a light-emitting element which emits near-infrared light and hardly recognizable visible light. This light-emitting element has a light-emitting layer that comprises a luminescent organic compound and a host material. The light-emitting element has a spectral maximum peak in a range of 750-900 nm. In this light-emitting element, the relation between luminance A and radiance B satisfies 0≤A / B≤1.

Description

[Technical field]

[0001] One embodiment of the present invention relates to a light-emitting device, a light-emitting apparatus, a light-emitting module, an electronic device, and a lighting apparatus.

[0002] Note that one embodiment of the present invention is not limited to the above technical field. Examples of the technical field of one embodiment of the present invention include a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, an electronic device, a lighting device, an input device (e.g., a touch sensor), an input / output device (e.g., a touch panel), a driving method thereof, or a manufacturing method thereof. [Background technology]

[0003] Research and development of light-emitting devices (also called organic EL devices or organic EL elements) that utilize the organic electroluminescence (EL) phenomenon is being actively conducted. The basic structure of an organic EL device is a layer containing a light-emitting organic compound (hereinafter also referred to as the light-emitting layer) sandwiched between a pair of electrodes. By applying a voltage to this organic EL device, light can be emitted from the light-emitting organic compound.

[0004] Examples of light-emitting organic compounds include compounds that can convert a triplet excited state into light emission (also called phosphorescent compounds or phosphorescent materials). Patent Document 1 discloses an organometallic complex having iridium or the like as a central metal as a phosphorescent material.

[0005] Image sensors are also used for various purposes, such as personal authentication, defect analysis, medical diagnosis, and security. Image sensors use different wavelengths of light source depending on the purpose. Image sensors use light of various wavelengths, for example, visible light, short wavelength light such as X-rays, and long wavelength light such as near-infrared light.

[0006] In addition to applications as display devices, applications of light-emitting devices as light sources for the above-mentioned image sensors are also being considered. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2007-137872 A Summary of the Invention [Problem to be solved by the invention]

[0008] An object of one embodiment of the present invention is to provide a light-emitting device that emits near-infrared light and in which the emission of visible light is difficult to visually recognize.An object of one embodiment of the present invention is to improve the emission efficiency of a light-emitting device that emits near-infrared light.An object of one embodiment of the present invention is to improve the reliability of a light-emitting device that emits near-infrared light.

[0009] Note that the description of these problems does not preclude the existence of other problems. One embodiment of the present invention does not necessarily have to solve all of these problems. Problems other than these can be extracted from the description of the specification, drawings, and claims. [Means for solving the problem]

[0010] One embodiment of the present invention is a light-emitting device having an emission layer including a light-emitting organic compound and a host material, an emission spectrum having a maximum peak wavelength of 750 nm or more and 900 nm or less, and a luminance A [cd / m 2 ] and radiance B [W / sr / m 2 ] is a light-emitting device that satisfies 0≦A / B≦1[cd·sr / W].

[0011] One embodiment of the present invention is a light-emitting device having an emission layer including a light-emitting organic compound and a host material, an emission spectrum having a maximum peak wavelength of 750 nm or more and 900 nm or less, and a luminance A [cd / m 2 ] and radiance B [W / sr / m 2 ] means 0

[0012] ​ The difference between the HOMO level and the LUMO level of the host material is preferably 1.35 eV or more and 2.25 eV or less.

[0013] The host material preferably has a first organic compound and a second organic compound. The HOMO level of the first organic compound is preferably higher than the HOMO level of the second organic compound. The difference between the HOMO level of the first organic compound and the LUMO level of the second organic compound is preferably smaller than the difference between the HOMO level and the LUMO level of the light-emitting organic compound. The first organic compound and the second organic compound are preferably substances that form an exciplex. The difference between the HOMO level of the first organic compound and the LUMO level of the second organic compound is preferably 1.35 eV or more and 2.25 eV or less.

[0014] One embodiment of the present invention is a light-emitting device having an emission layer including a light-emitting organic compound and a host material, an emission spectrum having a maximum peak wavelength of 750 nm to 900 nm, a HOMO level of the host material being higher than the HOMO level of the light-emitting organic compound by 0.4 eV or more, and a difference between the HOMO level and the LUMO level of the host material being smaller than the difference between the HOMO level and the LUMO level of the light-emitting organic compound. The difference between the HOMO level and the LUMO level of the host material is preferably 1.35 eV to 2.25 eV.

[0015] One embodiment of the present invention is a light-emitting device having an emission layer including a light-emitting organic compound and a host material, an emission spectrum having a maximum peak wavelength of 750 nm to 900 nm, a first organic compound and a second organic compound as the host material, a HOMO level of the first organic compound being 0.4 eV or higher than a HOMO level of the light-emitting organic compound, a HOMO level of the first organic compound being higher than a HOMO level of the second organic compound, and a difference between the HOMO level of the first organic compound and the LUMO level of the second organic compound being smaller than a difference between the HOMO level and the LUMO level of the light-emitting organic compound. The first organic compound and the second organic compound are preferably substances that form an exciplex. A difference between the HOMO level of the first organic compound and the LUMO level of the second organic compound is preferably 1.35 eV to 2.25 eV.

[0016] The rising wavelength on the short wavelength side of the maximum peak in the emission spectrum is preferably 650 nm or more.

[0017] The light-emitting organic compound preferably has a PL spectrum in solution with a maximum peak having a rising wavelength of 650 nm or more on the short wavelength side.

[0018] The external quantum efficiency of the light emitting device is preferably 1% or greater.

[0019] The luminescent organic compound is preferably an organometallic complex having a metal-carbon bond.

[0020] The organometallic complex preferably has 2 to 5 condensed heteroaromatic rings, which are preferably coordinated to a metal.

[0021] The light-emitting organic compound is preferably a cyclometal complex.The light-emitting organic compound is preferably an orthometal complex.The light-emitting organic compound is preferably an iridium complex.

[0022] One embodiment of the present invention is a light-emitting device including a light-emitting device having any of the above structures and one or both of a transistor and a substrate.

[0023] One embodiment of the present invention is a light-emitting module having the above-described light-emitting device, such as a module to which a connector such as a flexible printed circuit (hereinafter, referred to as FPC) or a TCP (Tape Carrier Package) is attached, or a light-emitting module to which an integrated circuit (IC) is mounted by a COG (Chip On Glass) method or a COF (Chip On Film) method, etc. Note that the light-emitting module of one embodiment of the present invention may have only one of a connector and an IC, or may have both.

[0024] One embodiment of the present invention is an electronic device including the above-described light-emitting module and at least one of an antenna, a battery, a housing, a camera, a speaker, a microphone, and an operation button.

[0025] One embodiment of the present invention is a lighting device including the above-described light-emitting device and at least one of a housing, a cover, and a support base. Effect of the Invention

[0026] According to one embodiment of the present invention, a light-emitting device that emits near-infrared light and in which visible light emission is difficult to visually recognize can be provided. According to one embodiment of the present invention, the light-emitting efficiency of a light-emitting device that emits near-infrared light can be increased. According to one embodiment of the present invention, the reliability of a light-emitting device that emits near-infrared light can be improved.

[0027] Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all of these effects. Effects other than these can be extracted from the description in the specification, drawings, and claims. [Brief description of the drawings]

[0028] 1A to 1C are diagrams illustrating an example of a light-emitting device. Fig. 2A is a top view showing an example of a light emitting device, and Fig. 2B and Fig. 2C are cross-sectional views showing an example of the light emitting device. Fig. 3A is a top view showing an example of a light emitting device, and Fig. 3B is a cross-sectional view showing the example of the light emitting device. 4A to 4E are diagrams showing an example of an electronic device. FIG. 5 is a cross-sectional view showing a light-emitting device according to an embodiment. FIG. 6 is a diagram showing an emission spectrum of the light-emitting device of the example. FIG. 7 is a diagram showing an emission spectrum of the light-emitting device of the example. FIG. 8 is a diagram showing the emission spectra of the light-emitting device and the mixed film of the example. FIG. 9 is a diagram showing the emission spectra of the light-emitting device and the mixed film of the example. FIG. 10 is a diagram showing the emission spectra of the light-emitting device and the mixed film of the example. FIG. 11 is a diagram showing the emission spectra of the light-emitting device and the mixed film of the example. FIG. 12 is a diagram showing the absorption spectrum of [Ir(dmdpbq)2(dpm)]. FIG. 13 shows the emission spectrum of [Ir(dmdpbq)2(dpm)]. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be easily understood by those skilled in the art that the modes and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0030] In the configuration of the invention described below, the same parts or parts having similar functions are denoted by the same reference numerals in different drawings, and the repeated explanations are omitted. In addition, when referring to similar functions, the same hatch pattern may be used and no particular reference numeral may be used.

[0031] In addition, for ease of understanding, the position, size, range, etc. of each component shown in the drawings may not represent the actual position, size, range, etc. Therefore, the disclosed invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings.

[0032] In addition, the words "film" and "layer" can be interchanged depending on the case or situation. For example, the term "conductive layer" can be changed to the term "conductive film". Or, for example, the term "insulating film" can be changed to the term "insulating layer".

[0033] (Embodiment 1) In this embodiment, a light-emitting device of one embodiment of the present invention will be described with reference to FIG.

[0034] A light-emitting device according to one embodiment of the present invention includes a light-emitting organic compound (also referred to as a guest material) and a host material in a light-emitting layer.

[0035] In the light-emitting device according to one embodiment of the present invention, the maximum peak wavelength (the wavelength with the highest peak intensity) of the emission spectrum (electroluminescence (EL) spectrum) is 750 nm or more and 900 nm or less, preferably 780 nm or more, and preferably 880 nm or less.

[0036] In the light-emitting device according to one embodiment of the present invention, the luminance A [cd / m 2 ] and radiance B [W / sr / m 2 ] preferably satisfies 0≦A / B≦1 [cd sr / W]. Or, luminance A [cd / m 2 ] and radiance B [W / sr / m 2 ] means 0

[0037] ​When the luminance and radiance satisfy the above formula, a light emitting device can be realized that is difficult to visually recognize the emission of visible light and that efficiently emits near-infrared light.

[0038] In a light-emitting device using a guest material that emits near-infrared light, visible light emission originating from the host material may be visually recognized. In order to make the emission of the host material less visible, it is preferable that the emission of the host material is light having a wavelength with low luminosity.

[0039] Examples of light with low luminosity include ultraviolet to blue light and red to near-infrared light. For example, if the host material emits such light, even if the light-emitting device exhibits light emission derived from the host material, the emission of visible light is difficult to be visually recognized. Specifically, in the light-emitting device according to one embodiment of the present invention, the emission spectrum may further have a peak at 435 nm or less, or at 565 nm or more and 900 nm or less. The wavelength of the peak is preferably 600 nm or more, and more preferably 800 nm or less.

[0040] Here, when the guest material is a phosphorescent material, the absorption band that is considered to contribute most strongly to light emission is the absorption wavelength corresponding to the direct transition from the singlet ground state to the triplet excited state and its vicinity, which is the absorption band that appears on the longest wavelength side (lowest energy side). For this reason, it is preferable that the emission spectrum (fluorescence spectrum and phosphorescence spectrum) of the host material largely overlaps with the absorption band on the longest wavelength side (lowest energy side) of the absorption spectrum of the phosphorescent material. This allows the excitation energy to be transferred smoothly from the host material to the guest material. Then, the excitation energy of the host material is converted into the excitation energy of the guest material, and the guest material efficiently emits light.

[0041] Therefore, in order for the guest material to efficiently emit near-infrared light, it is preferable that the emission wavelength of the host material is long. When the emission of the host material is light of a long wavelength, the emission of visible light (derived from the host material) is difficult to visually recognize, and a light-emitting device that efficiently emits near-infrared light can be realized. In particular, it is preferable that the emission of the host material is red light to near-infrared light, since the visibility of the emission derived from the host material can be reduced and the transfer of excitation energy from the host material to the guest material occurs efficiently.

[0042] The HOMO level of the host material is preferably 0.4 eV or more higher than the HOMO level of the guest material. When the HOMO level of the host material is sufficiently higher than the HOMO level of the guest material, the band gap of the host material can be reduced, and the emission can be made to have a long wavelength. This can reduce the luminosity of the emission of the host material. In addition, the transfer of excitation energy from the host material to the guest material occurs efficiently, and a light-emitting device that efficiently emits near-infrared light can be realized.

[0043] The LUMO level and HOMO level of a material can be derived from the electrochemical properties (reduction potential and oxidation potential) of the material measured by cyclic voltammetry (CV) measurement.

[0044] The difference between the HOMO level and the LUMO level of the host material is preferably smaller than the difference between the HOMO level and the LUMO level of the guest material. The light emitted by the host material can be made longer wavelength even if the difference between the HOMO level and the LUMO level of the host material is small. Specifically, the difference between the HOMO level and the LUMO level of the host material is preferably 1.35 eV or more and 2.25 eV or less. The difference between the levels is preferably 1.55 eV or more, and is preferably 1.90 eV or less.

[0045] Here, when a phosphorescent material is used as the guest material, if the T1 level of the host material is higher than the T1 level (the energy level of the lowest triplet excited state) of the guest material, the luminous efficiency of the light-emitting device can be increased. On the other hand, the host material can convert singlet excitation energy into light emission. The S1 level of the host material (the energy level of the lowest singlet excited state) is higher than the T1 level of the host material and the T1 level of the guest material. In order to make the emission of the host material red light to near infrared light, it is preferable that the difference between the T1 level of the guest material and the S1 level of the host material is small. In other words, it is preferable that the difference between the S1 level and the T1 level of the host material is small. A thermally activated delayed fluorescence (TADF) material can be suitably used as a host material because the difference between the S1 level and the T1 level is small.

[0046] Alternatively, a first organic compound and a second organic compound may be used as a host material to form an exciplex. The first organic compound and the second organic compound are a combination that forms an exciplex. In this case, the host material can be said to be a mixed material of the first organic compound and the second organic compound. By using the first organic compound and the second organic compound as the host material, an exciplex is formed in a light-emitting device when a voltage is applied between a pair of electrodes.

[0047] Excitplexes, which form excited states with two types of substances, have an extremely small difference between the S1 and T1 levels and function as TADF materials that can convert triplet excitation energy into singlet excitation energy.

[0048] When the host material contains a first organic compound and a second organic compound, light emission originating from an exciplex formed by the first organic compound and the second organic compound is observed in the light-emitting device of one embodiment of the present invention. Therefore, in order to make the light emission from the exciplex less visible, it is preferable that the light emission from the exciplex has low luminosity.

[0049] Here, consider a case where the heights of the energy levels are as follows: HOMO level of the second organic compound < HOMO level of the first organic compound < LUMO level of the second organic compound < LUMO level of the first organic compound. In this case, in an exciplex formed by two organic compounds, the LUMO level originates from the second organic compound, and the HOMO level originates from the first organic compound.

[0050] Therefore, the HOMO level of the first organic compound is preferably 0.4 eV or more higher than the HOMO level of the guest material. When the HOMO level of the first organic compound is sufficiently higher than the HOMO level of the guest material, the emission of the exciplex can be made to have a long wavelength. This makes it possible to reduce the luminosity of the exciplex. In addition, the transfer of excitation energy from the exciplex to the guest material occurs efficiently, and a light-emitting device that efficiently emits near-infrared light can be realized.

[0051] In addition, the difference between the HOMO level of the first organic compound and the LUMO level of the second organic compound is preferably smaller than the difference between the HOMO level and the LUMO level of the guest material. The emission of the exciplex can be made to have a long wavelength even when the difference between the HOMO level of the first organic compound and the LUMO level of the second organic compound is small. Specifically, the difference between the HOMO level of the first organic compound and the LUMO level of the second organic compound is preferably 1.35 eV or more and 2.25 eV or less. The difference in the levels is preferably 1.55 eV or more, and preferably 1.90 eV or less.

[0052] In addition, the guest material preferably has a low emission intensity in the visible light region. For example, in the light-emitting device according to one embodiment of the present invention, the rising wavelength on the short wavelength side of the maximum peak in the emission spectrum is preferably 650 nm or more.

[0053] The method of determining the rising wavelength in this specification etc. will be described. First, tangents are drawn at each point on the curve, starting from the point on the short wavelength side of the emission spectrum on the linear scale, to the maximum point on the shortest wavelength side among the maximum points of the spectrum. The slope of this tangent increases as the curve rises (the value on the vertical axis increases). The wavelength at which the tangent drawn at the point on the shortest wavelength side where this slope has a maximum value intersects with the origin is defined as the rising wavelength. Note that maximum points where the value on the vertical axis is 10% or less of the maximum peak are excluded from the maximum points on the shortest wavelength side mentioned above.

[0054] Moreover, the light-emitting organic compound (guest material) preferably has a photoluminescence (PL) spectrum in solution with a rising wavelength of 650 nm or more on the short wavelength side of the maximum peak.

[0055] The external quantum efficiency of the light-emitting device according to one embodiment of the present invention is preferably 1% or more.

[0056] In the light-emitting device according to one embodiment of the present invention, the emission intensity of the host material or the exciplex is sufficiently low, so that the external quantum efficiency can be regarded as the external quantum efficiency calculated from the emission of the guest material in the light-emitting device, or the external quantum efficiency calculated from the near-infrared emission in the light-emitting device. In addition, in order to calculate the external quantum efficiency from the emission of the guest material or the near-infrared emission in the light-emitting device, the external quantum efficiency may be calculated, for example, using data in a predetermined wavelength range. Specifically, the external quantum efficiency may be calculated from data in a wavelength range of 600 nm to 1030 nm.

[0057] Alternatively, the external quantum efficiency may be calculated after performing waveform separation of the emission spectrum to distinguish the emission originating from the guest material from the emission originating from the host material or the exciplex. In this case, the external quantum efficiency calculated from the emission originating from the guest material in the light-emitting device of one embodiment of the present invention is preferably 1% or more. Alternatively, the external quantum efficiency calculated from the near-infrared emission in the light-emitting device of one embodiment of the present invention is preferably 1% or more.

[0058] A light-emitting organic compound is preferable because it can increase the light-emitting efficiency of a light-emitting device when it emits phosphorescence. In particular, the light-emitting organic compound is preferably an organometallic complex having a metal-carbon bond. Among them, the light-emitting organic compound is more preferably a cyclometal complex. Furthermore, the light-emitting organic compound is preferably an orthometal complex. These organic compounds are easy to emit phosphorescence, and therefore can increase the light-emitting efficiency of a light-emitting device. Therefore, it is preferable that the light-emitting device of one embodiment of the present invention emits phosphorescence.

[0059] Furthermore, organometallic complexes having a metal-carbon bond have higher luminous efficiency and higher chemical stability than porphyrin-based compounds, and are therefore suitable as luminescent organic compounds.

[0060] In addition, when a light-emitting organic compound is used as a guest material in the light-emitting layer and another organic compound is used as a host material, if a large valley occurs in the absorption spectrum of the light-emitting organic compound (a low-intensity portion occurs), depending on the value of the excitation energy of the host material, the excitation energy does not move smoothly from the host material to the guest material, and the energy transfer efficiency decreases. Here, in the absorption spectrum of an organometallic complex having a metal-carbon bond, many absorption bands overlap, such as an absorption band derived from a triplet MLCT (Metal to Ligand Charge Transfer) transition, an absorption band derived from a singlet MLCT transition, and an absorption band derived from a triplet π-π* transition, so that a large valley is unlikely to occur in the absorption spectrum. Therefore, the range of excitation energy values ​​of materials that can be used as a host material can be widened, and the range of host materials to be selected can be expanded.

[0061] In addition, the light-emitting organic compound is preferably an iridium complex. For example, the light-emitting organic compound is preferably a cyclometal complex using iridium as the central metal. Since the iridium complex has higher chemical stability than platinum complexes, the reliability of the light-emitting device can be improved by using an iridium complex as the light-emitting organic compound. From the viewpoint of such stability, a cyclometal complex of iridium is preferable, and an orthometal complex of iridium is more preferable.

[0062] In addition, from the viewpoint of obtaining near-infrared emission, the ligand in the above-mentioned organometallic complex preferably has a structure in which a fused heteroaromatic ring having 2 to 5 rings is coordinated to a metal. The fused heteroaromatic ring preferably has 3 or more rings. In addition, the fused heteroaromatic ring preferably has 4 or less rings. The more rings the fused heteroaromatic ring has, the lower the LUMO level can be, and the longer the emission wavelength of the organometallic complex can be. In addition, the fewer the fused heteroaromatic rings, the higher the sublimability can be. Therefore, by adopting a fused heteroaromatic ring having 2 to 5 rings, the LUMO level of the ligand is appropriately lowered, and the emission wavelength of the organometallic complex derived from the (triplet) MLCT transition can be extended to the near infrared while maintaining high sublimability. In addition, the more the number of nitrogen atoms (N) the fused heteroaromatic ring has, the lower the LUMO level can be. Therefore, the number of nitrogen atoms (N) in the condensed heteroaromatic ring is preferably two or more, and particularly preferably two.

[0063] The light-emitting device of one embodiment of the present invention can be formed into a film and can be easily increased in area; therefore, the light-emitting device can be used as a surface light source that emits near-infrared light.

[0064] A light-emitting device according to one embodiment of the present invention is capable of efficiently emitting near-infrared light while making visible light emission difficult to be visually recognized. By using such a light-emitting device, an electronic device that performs authentication, analysis, diagnosis, etc. using near-infrared light can be realized. In the electronic device, the visible light emitted by the light-emitting device can be prevented from becoming noise in authentication, analysis, diagnosis, etc. using near-infrared light. This can improve the accuracy of authentication, analysis, diagnosis, etc. Furthermore, in electronic devices for security-related or military applications, imaging using near-infrared light can be performed without being noticed by people in the vicinity.

[0065] [Example of light-emitting device configuration] <Basic structure of light-emitting devices> 1A to 1C show an example of a light-emitting device having an EL layer between a pair of electrodes.

[0066] 1A has a structure (single structure) in which an EL layer 103 is sandwiched between a first electrode 101 and a second electrode 102. The EL layer 103 has at least a light-emitting layer.

[0067] The light-emitting device may have multiple EL layers between a pair of electrodes. Fig. 1B shows a light-emitting device with a tandem structure having two EL layers (EL layer 103a and EL layer 103b) between a pair of electrodes and a charge generating layer 104 between the two EL layers. The light-emitting device with the tandem structure can be driven at a low voltage and can reduce power consumption.

[0068] The charge generation layer 104 has a function of injecting electrons into one of the EL layers 103a and 103b and injecting holes into the other when a voltage is applied between the first electrode 101 and the second electrode 102. Therefore, in Fig. 1B, when a voltage is applied to the first electrode 101 so that the first electrode 101 has a higher potential than the second electrode 102, electrons are injected from the charge generation layer 104 into the EL layer 103a and holes are injected into the EL layer 103b.

[0069] From the viewpoint of light extraction efficiency, the charge generation layer 104 preferably transmits near-infrared light (specifically, the transmittance of the charge generation layer 104 for near-infrared light is 40% or more). The charge generation layer 104 also functions even if it has a lower conductivity than the first electrode 101 and the second electrode 102.

[0070] FIG. 1C shows an example of a laminated structure of the EL layer 103. In this embodiment, the first electrode 101 functions as an anode, and the second electrode 102 functions as a cathode. The EL layer 103 has a structure in which a hole injection layer 111, a hole transport layer 112, a light-emitting layer 113, an electron transport layer 114, and an electron injection layer 115 are laminated in this order on the first electrode 101. The hole injection layer 111, the hole transport layer 112, the light-emitting layer 113, the electron transport layer 114, and the electron injection layer 115 may each have a single-layer structure or a laminated structure. Even in the case of having a plurality of EL layers as in the tandem structure shown in FIG. 1B, the same laminated structure as the EL layer 103 shown in FIG. 1C can be applied to each EL layer. In addition, when the first electrode 101 is a cathode and the second electrode 102 is an anode, the laminated order is reversed.

[0071] The light-emitting layer 113 may have a light-emitting substance or a combination of a plurality of substances, and may have a structure capable of emitting fluorescent or phosphorescent light of a desired wavelength. The EL layer 103a and the EL layer 103b shown in FIG. 1B may have a structure that emits light of different wavelengths.

[0072] In the light-emitting device according to one embodiment of the present invention, the light emitted from the EL layer may be resonated between a pair of electrodes to enhance the light emission. For example, in FIG. 1C, the first electrode 101 is a reflective electrode (an electrode having reflectivity to near-infrared light) and the second electrode 102 is a semi-transmissive / semi-reflective electrode (an electrode having transmittance and reflectivity to near-infrared light), thereby forming a micro-optical resonator (microcavity) structure, and the light emitted from the EL layer 103 can be enhanced.

[0073] In addition, when the first electrode 101 of the light-emitting device is a reflective electrode having a laminated structure of a conductive film reflective to near-infrared light and a conductive film transmissive to near-infrared light, optical adjustment can be performed by controlling the film thickness of the transmissive conductive film. Specifically, it is preferable to adjust the inter-electrode distance between the first electrode 101 and the second electrode 102 to be approximately mλ / 2 (where m is a natural number) for the wavelength λ of light obtained from the light-emitting layer 113.

[0074] In order to amplify the desired light (wavelength: λ) obtained from the light-emitting layer 113, it is preferable to adjust the optical distance from the first electrode 101 to the region (light-emitting region) in the light-emitting layer 113 where the desired light is obtained, and the optical distance from the second electrode 102 to the region (light-emitting region) in the light-emitting layer 113 where the desired light is obtained, to be approximately (2m'+1)λ / 4 (where m' is a natural number). Note that the light-emitting region here refers to the recombination region of holes and electrons in the light-emitting layer 113.

[0075] By carrying out such optical adjustment, the spectrum of the light obtained from the light emitting layer 113 can be narrowed, and light of a desired wavelength can be obtained.

[0076] However, in the above case, the optical distance between the first electrode 101 and the second electrode 102 can be strictly said to be the total thickness from the reflection area in the first electrode 101 to the reflection area in the second electrode 102. However, since it is difficult to strictly determine the reflection area in the first electrode 101 or the second electrode 102, it is assumed that the above-mentioned effect can be sufficiently obtained by assuming any position of the first electrode 101 or the second electrode 102 as the reflection area. Furthermore, the optical distance between the first electrode 101 and the light-emitting layer from which the desired light is obtained can be strictly said to be the optical distance between the reflection area in the first electrode 101 and the light-emitting area in the light-emitting layer from which the desired light is obtained. However, since it is difficult to strictly determine the reflection area in the first electrode 101 or the light-emitting area in the light-emitting layer from which the desired light is obtained, it is assumed that the above-mentioned effect can be sufficiently obtained by assuming any position of the first electrode 101 as the reflection area and any position of the light-emitting layer from which the desired light is obtained as the light-emitting area.

[0077] At least one of the first electrode 101 and the second electrode 102 is an electrode having translucency to near-infrared light. The electrode having translucency to near-infrared light has a transmittance to near-infrared light of 40% or more. When the electrode having translucency to near-infrared light is the semi-transmissive / semi-reflective electrode, the electrode has a reflectance to near-infrared light of 20% or more, preferably 40% or more, and may be less than 100%, preferably 95% or less, and may be 80% or less or 70% or less. For example, the electrode has a reflectance to near-infrared light of 20% or more and 80% or less, preferably 40% or more and 70% or less. The resistivity of the electrode is 1×10 -2 Ωcm or less is preferable.

[0078] When the first electrode 101 or the second electrode 102 is a reflective electrode, the reflectance of the reflective electrode to near infrared light is set to 40% or more and 100% or less, preferably 70% or more and 100% or less. The resistivity of this electrode is 1×10 -2 Ωcm or less is preferable.

[0079] <Specific structure and manufacturing method of light-emitting device> Next, a specific structure and a manufacturing method of the light-emitting device will be described, using a light-emitting device having a single structure shown in FIG. 1C.

[0080] <First Electrode and Second Electrode> As the material for forming the first electrode 101 and the second electrode 102, the following materials can be used in appropriate combination as long as the above-mentioned functions of both electrodes are satisfied. For example, metals, alloys, electrically conductive compounds, and mixtures thereof can be used appropriately. Specific examples include In-Sn oxide (also called ITO), In-Si-Sn oxide (also called ITSO), In-Zn oxide, and In-W-Zn oxide. In addition, metals such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), and neodymium (Nd), and alloys containing these in appropriate combinations can also be used. In addition, elements belonging to Group 1 or 2 of the periodic table not exemplified above (e.g., lithium (Li), cesium (Cs), calcium (Ca), strontium (Sr)), rare earth metals such as europium (Eu) and ytterbium (Yb), alloys containing appropriate combinations of these, graphene, etc. can be used.

[0081] When a light-emitting device having a microcavity structure is manufactured, the first electrode 101 is formed as a reflective electrode, and the second electrode 102 is formed as a semi-transmissive and semi-reflective electrode. Therefore, a single or multiple desired conductive materials can be used to form a single layer or a laminated layer. The second electrode 102 is formed by selecting a material in the same manner as above after the EL layer 103 is formed. These electrodes can be manufactured by sputtering or vacuum deposition.

[0082] In the light-emitting device shown in FIG. 1C, when the first electrode 101 is an anode, a hole injection layer 111 and a hole transport layer 112 are sequentially formed on the first electrode 101 by vacuum deposition.

[0083] <Hole injection layer and hole transport layer> The hole injection layer 111 is a layer that injects holes from the first electrode 101, which is an anode, to the EL layer 103, and is a layer that contains a material with high hole injection properties.

[0084] Examples of materials with high hole injection properties include transition metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide, and phthalocyanine compounds such as phthalocyanine (abbreviation: HPc) and copper phthalocyanine (abbreviation: CuPc).

[0085] Materials with high hole injection properties include 4,4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), 1,3,5-tris[N- Aromatic amine compounds such as (4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B), 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), and 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1) can be used.

[0086] Examples of materials with high hole injection properties include poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl) methacrylamide] (abbreviation: PTPDMA), poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: Poly-TPD), etc. Alternatively, polymer compounds to which acids have been added, such as poly(3,4-ethylenedioxythiophene) / poly(styrenesulfonic acid) (abbreviation: PEDOT / PSS) and polyaniline / poly(styrenesulfonic acid) (PAni / PSS), etc., can also be used.

[0087] A composite material containing a hole transport material and an acceptor material (electron accepting material) can also be used as a material with high hole injection properties. In this case, electrons are extracted from the hole transport material by the acceptor material, generating holes in the hole injection layer 111, and the holes are injected into the light emitting layer 113 via the hole transport layer 112. Note that the hole injection layer 111 may be formed as a single layer made of a composite material containing a hole transport material and an acceptor material, or may be formed by laminating the hole transport material and the acceptor material in separate layers.

[0088] The hole transport layer 112 is a layer that transports holes injected from the first electrode 101 by the hole injection layer 111 to the light emitting layer 113. The hole transport layer 112 is a layer that contains a hole transport material. It is particularly preferable to use a hole transport material used for the hole transport layer 112 that has a HOMO level that is the same as or close to the HOMO level of the hole injection layer 111.

[0089] As an acceptor material used for the hole injection layer 111, an oxide of a metal belonging to Groups 4 to 8 of the periodic table can be used. Specific examples include molybdenum oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, tungsten oxide, manganese oxide, and rhenium oxide. Among them, molybdenum oxide is particularly preferable because it is stable in the air, has low hygroscopicity, and is easy to handle. In addition, organic acceptors such as quinodimethane derivatives, chloranil derivatives, and hexaazatriphenylene derivatives can be used. Examples of compounds having an electron-withdrawing group (halogen group or cyano group) include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ), etc. In particular, compounds in which an electron-withdrawing group is bonded to a condensed aromatic ring having multiple heteroatoms, such as HAT-CN, are thermally stable and preferable. In addition, radialene derivatives having an electron-withdrawing group (especially a halogen group such as a fluoro group or a cyano group)[3] are preferred because they have very high electron-accepting properties. Specific examples include α,α',α''-1,2,3-cyclopropane triylidene tris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclopropane triylidene tris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α',α''-1,2,3-cyclopropane triylidene tris[2,3,4,5,6-pentafluorobenzeneacetonitrile].

[0090] The hole transport material used in the hole injection layer 111 and the hole transport layer 112 is 10 -6 cm 2 A substance having a hole mobility of / Vs or more is preferable. Note that other substances can also be used as long as they have a higher hole transporting property than an electron transporting property.

[0091] As the hole transporting material, a material having high hole transporting properties, such as a π-electron-rich heteroaromatic compound (eg, a carbazole derivative, a thiophene derivative, a furan derivative, etc.) or an aromatic amine (a compound having an aromatic amine skeleton), is preferable.

[0092] Examples of carbazole derivatives (compounds having a carbazole skeleton) include bicarbazole derivatives (for example, 3,3'-bicarbazole derivatives) and aromatic amines having a carbazolyl group.

[0093] Specific examples of bicarbazole derivatives (e.g., 3,3'-bicarbazole derivatives) include 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 9,9'-bis(1,1'-biphenyl-4-yl)-3,3'-bi-9H-carbazole, 9,9'-bis(1,1'-biphenyl-3-yl)-3,3'-bi-9H-carbazole, 9-(1,1'-biphenyl-3-yl)-9'-(1,1'-biphenyl-4-yl)-9H,9'H-3,3'-bicarbazole (abbreviation: mBPCCBP), and 9-(2-naphthyl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviation: βNCCP).

[0094] Specific examples of aromatic amines having a carbazolyl group include 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine (abbreviation: PCBiF), N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-yl, and N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-yl]. PCBBiF, 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (PCBNBB), 4-phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl)triphenylamine (PCBBi1BP), N,N'-bis(9-phenylcarbazol-3-yl)-N,N'-diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N,N',N''-triphenyl-N,N',N''-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine (abbreviation: PCA3B), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF), PCzPCA1, PCzPCA2, PCzPCN1, 3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA2), 3,Examples of such compounds include 6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole (abbreviation: PCzTPN2), 2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), N-[4-(9H-carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline (abbreviation: YGA1BP), N,N'-bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F), and 4,4',4''-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA).

[0095] In addition to the above, examples of the carbazole derivative include 3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), and 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA).

[0096] Specific examples of thiophene derivatives (compounds having a thiophene skeleton) and furan derivatives (compounds having a furan skeleton) include compounds having a thiophene skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II).

[0097] Specific examples of aromatic amines include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: :BSPB), 4-phenyl-4'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(9,9-dimethyl-9H-fluoren-2-yl) N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine (abbreviation: DPNF), 2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPASF), 2,7-bis[N-(4-diphenylaminophenyl)- N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPA2SF), 4,4',4''-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1'-TNATA), TDATA, m-MTDATA, N,N'-di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), DPAB, DNTPD, DPA3B, and the like.

[0098] As the hole transporting material, polymer compounds such as PVK, PVTPA, PTPDMA, and Poly-TPD can also be used.

[0099] The hole transporting material is not limited to the above, and various known materials can be used for the hole injection layer 111 and the hole transport layer 112 either alone or in combination.

[0100] In the light-emitting device shown in FIG. 1C, a light-emitting layer 113 is formed on a hole-transporting layer 112 by vacuum deposition.

[0101] <Light-emitting layer> The light-emitting layer 113 is a layer containing a light-emitting substance.

[0102] A light-emitting device according to one embodiment of the present invention includes a light-emitting organic compound as a light-emitting substance. The light-emitting organic compound emits near-infrared light. Specifically, the maximum peak wavelength of light emitted by the light-emitting organic compound is greater than 750 nm and less than or equal to 900 nm.

[0103] As an example of a light-emitting organic compound, there is used bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-2-benzo[g]quinoxalinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ), which is an organometallic complex shown as a guest material (phosphorescent material) in the examples described later. 2 O,O') iridium(III) (abbreviation: [Ir(dmdpbq)2(dpm)]) can be used.

[0104] Furthermore, as a light-emitting organic compound, for example, tetraphenyltetrabenzoporphyrin platinum (II) can be used.

[0105] Light-emitting layer 113 can have one or more light-emitting materials.

[0106] The light-emitting layer 113 contains one or more organic compounds (host materials) in addition to a light-emitting substance (guest material). As the one or more organic compounds, one or both of a hole-transporting material and an electron-transporting material described in this embodiment can be used. As the one or more organic compounds, a bipolar material may be used.

[0107] There is no particular limitation on the light-emitting substance that can be used for the light-emitting layer 113, and a light-emitting substance that converts singlet excitation energy into light emission in the near-infrared light region, or a light-emitting substance that converts triplet excitation energy into light emission in the near-infrared light region can be used.

[0108] Examples of luminescent substances that convert singlet excitation energy into luminescence include substances that emit fluorescence (fluorescent materials), such as pyrene derivatives, anthracene derivatives, triphenylene derivatives, fluorene derivatives, carbazole derivatives, dibenzothiophene derivatives, dibenzofuran derivatives, dibenzoquinoxaline derivatives, quinoxaline derivatives, pyridine derivatives, pyrimidine derivatives, phenanthrene derivatives, and naphthalene derivatives.

[0109] Examples of light-emitting substances that convert triplet excitation energy into light emission include substances that emit phosphorescence (phosphorescent materials) and TADF materials that exhibit thermally activated delayed fluorescence.

[0110] Examples of phosphorescent materials include organometallic complexes (particularly iridium complexes) having a 4H-triazole skeleton, 1H-triazole skeleton, imidazole skeleton, pyrimidine skeleton, pyrazine skeleton, or pyridine skeleton, organometallic complexes (particularly iridium complexes) having a phenylpyridine derivative having an electron-withdrawing group as a ligand, platinum complexes, and rare earth metal complexes.

[0111] As the host material used in the light-emitting layer 113, one or more substances having a larger energy gap than the energy gap of the light-emitting substance can be selected and used.

[0112] When the light-emitting substance used in the light-emitting layer 113 is a fluorescent material, an organic compound used in combination with the light-emitting substance is preferably an organic compound having a high energy level in a singlet excited state and a low energy level in a triplet excited state.

[0113] When the luminescent substance is a fluorescent material, examples of organic compounds that can be used in combination with the luminescent substance include condensed polycyclic aromatic compounds such as anthracene derivatives, tetracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives, and dibenzo[g,p]chrysene derivatives.

[0114] Specific examples of organic compounds (host materials) used in combination with fluorescent materials include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: DPCzPA), PCPN, 9,10-diphenylanthracene (abbreviation: DPAnth), N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole-3-amine (abbreviation: CzA1PA ), 4-(10-phenyl-9-anthryl)triphenylamine (abbreviation: DPhPA), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine (abbreviation: PCAPBA), N-(9,10-di phenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchrysene, N,N,N',N',N'',N'',N''',N'''-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), CzPA, 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl 1,2-diphenyl-4'-benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4'-yl}anthracene (abbreviation: FLPPA), 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 9,9'-bianthryl (abbreviation: BANT), 9,9'-(stilbene-3,3'-diyl)diphenanthrene (abbreviation: DPNS), 9,9'-(stilbene-4,4'-diyl)diphenanthrene (abbreviation: DPNS2), 1,3,5-tri(1-pyrenyl)benzene (abbreviation: TPB3), 5,12-diphenyltetracene, 5,12-bis(biphenyl-2-yl)tetracene, etc.

[0115] When the light-emitting substance is a phosphorescent material, an organic compound having a triplet excitation energy (energy difference between the ground state and the triplet excited state) larger than the triplet excitation energy of the light-emitting substance may be selected as the organic compound to be used in combination with the light-emitting substance.

[0116] When multiple organic compounds (e.g., a first host material and a second host material) are used in combination with a light-emitting substance to form an exciplex, it is preferable to use these multiple organic compounds in combination with a phosphorescent material (particularly an organometallic complex).

[0117] With this structure, light emission using ExTET (Exciplex-Triplet Energy Transfer), which is an energy transfer from an exciplex to a light-emitting substance, can be efficiently obtained. Note that a combination of a plurality of organic compounds is preferably one that easily forms an exciplex, and it is particularly preferable to combine a compound that easily receives holes (hole transporting material) with a compound that easily receives electrons (electron transporting material). Note that the materials shown in this embodiment can be used as specific examples of the hole transporting material and the electron transporting material. With this structure, high efficiency, low voltage, and long life of the light-emitting device can be simultaneously achieved.

[0118] When the luminescent substance is a phosphorescent material, examples of organic compounds that can be used in combination with the luminescent substance include aromatic amines, carbazole derivatives, dibenzothiophene derivatives, dibenzofuran derivatives, zinc- or aluminum-based metal complexes, oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, pyrimidine derivatives, triazine derivatives, pyridine derivatives, bipyridine derivatives, and phenanthroline derivatives.

[0119] Among the above, specific examples of the aromatic amines (compounds having an aromatic amine skeleton), carbazole derivatives, dibenzothiophene derivatives (thiophene derivatives), and dibenzofuran derivatives (furan derivatives), which are organic compounds with high hole-transport properties, are the same as the specific examples of the hole-transport materials shown above.

[0120] Specific examples of zinc- or aluminum-based metal complexes, which are organic compounds with high electron transport properties, include metal complexes having a quinoline skeleton or a benzoquinoline skeleton, such as tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), and bis(8-quinolinolato)zinc(II) (abbreviation: Znq).

[0121] In addition, metal complexes having oxazole or thiazole ligands, such as bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO) and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), can also be used.

[0122] Specific examples of organic compounds with high electron transport properties, such as oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, and phenanthroline derivatives, include 2-(4-biphenylyl)5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1, 3,4-Oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: p-EtTAZ), 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(diphenyl) Benzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs), bathophenanthroline (abbreviation: Bphen), bathocuproine (abbreviation: BCP), 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBphen), 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBT PDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), and 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II).

[0123] Specific examples of heterocyclic compounds having a diazine skeleton, a triazine skeleton, and a pyridine skeleton, which are organic compounds with high electron transport properties, include 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), and 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II). 4,6mCzP2Pm), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), 2-[3'-(9,9-dimethyl mFBPTzn), 2-[(1,1'-biphenyl)-4-yl]-4-phenyl-6-[9,9'-spirobi(9H-fluoren)-2-yl]-1,3,5-triazine (abbreviation: BP-SFTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl- Examples of such compounds include 1,3,5-triazine (abbreviation: mBnfBPTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn-02), 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB).

[0124] As organic compounds with high electron transport properties, polymer compounds such as poly(2,5-pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), and poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)] (abbreviation: PF-BPy) can also be used.

[0125] A TADF material is a material that has a small difference between the S1 level and the T1 level and has the function of converting energy from triplet excitation energy to singlet excitation energy by reverse intersystem crossing. Therefore, triplet excitation energy can be upconverted to singlet excitation energy by a small amount of thermal energy (reverse intersystem crossing), and a singlet excited state can be efficiently generated. In addition, triplet excitation energy can be converted into light emission. Conditions for efficiently obtaining thermally activated delayed fluorescence include an energy difference between the S1 level and the T1 level of 0 eV or more and 0.2 eV or less, preferably 0 eV or more and 0.1 eV or less. In addition, delayed fluorescence in a TADF material refers to light emission that has a spectrum similar to that of normal fluorescence but has a significantly long lifespan. The lifespan is approximately 10 -6 seconds or more, preferably 10 -3 More than seconds.

[0126] As an index of the T1 level, a phosphorescence spectrum observed at low temperatures (for example, 77 K to 10 K) may be used. For a TADF material, when a tangent line is drawn at the base of the short wavelength side of the fluorescence spectrum, and the energy of the wavelength of the extrapolated line is defined as the S1 level, and a tangent line is drawn at the base of the short wavelength side of the phosphorescence spectrum, and the energy of the wavelength of the extrapolated line is defined as the T1 level, the difference between the S1 level and the T1 level is preferably 0.3 eV or less, and more preferably 0.2 eV or less.

[0127] The TADF material may be used as a guest material or as a host material.

[0128] Examples of TADF materials include fullerene and its derivatives, acridine derivatives such as proflavine, eosin, etc. Also included are metal-containing porphyrins including magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), palladium (Pd), etc. Examples of metal-containing porphyrins include protoporphyrin-tin fluoride complex (abbreviation: SnF2(Proto IX)), mesoporphyrin-tin fluoride complex (abbreviation: SnF2(Meso IX)), hematoporphyrin-tin fluoride complex (abbreviation: SnF2(Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complex (abbreviation: SnF2(Copro III-4Me)), octaethylporphyrin-tin fluoride complex (abbreviation: SnF2(OEP)), etioporphyrin-tin fluoride complex (abbreviation: SnF2(Etio I)), and octaethylporphyrin-platinum chloride complex (abbreviation: PtCl2OEP).

[0129] Other examples include 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), PCCzPTzn, 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation Heterocyclic compounds having a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring, such as bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS) and 10-phenyl-10H,10'H-spiro[acridine-9,9'-anthracene]-10'-one (abbreviation: ACRSA), can be used. Note that a substance in which a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring are directly bonded is particularly preferred because the donor property of the π-electron rich heteroaromatic ring and the acceptor property of the π-electron deficient heteroaromatic ring are both strong, and the energy difference between the singlet excited state and the triplet excited state is small.

[0130] In addition, when a TADF material is used, it can be used in combination with other organic compounds, particularly with the host material, hole transport material, and electron transport material described above.

[0131] Moreover, the above-mentioned materials can be used in combination with low molecular weight materials or high molecular weight materials to form the light emitting layer 113. Moreover, for film formation, a known method (such as a vapor deposition method, a coating method, or a printing method) can be appropriately used.

[0132] In the light-emitting device shown in FIG. 1C, an electron-transporting layer 114 is formed on light-emitting layer 113 .

[0133] <Electron transport layer> The electron transport layer 114 is a layer that transports electrons injected from the second electrode 102 by the electron injection layer 115 to the light-emitting layer 113. The electron transport layer 114 is a layer that contains an electron transport material. The electron transport material used for the electron transport layer 114 has a concentration of 1×10 -6 cm 2 A substance having an electron mobility of 1 / Vs or more is preferable. Note that other substances can also be used as long as they have a higher electron transporting property than a hole transporting property.

[0134] Examples of the electron-transporting material that can be used include metal complexes having a quinoline skeleton, metal complexes having a benzoquinoline skeleton, metal complexes having an oxazole skeleton, and metal complexes having a thiazole skeleton, as well as materials with high electron-transporting properties, such as oxadiazole derivatives, triazole derivatives, imidazole derivatives, oxazole derivatives, thiazole derivatives, phenanthroline derivatives, quinoline derivatives having a quinoline ligand, benzoquinoline derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, pyridine derivatives, bipyridine derivatives, pyrimidine derivatives, and other π-electron-deficient heteroaromatic compounds including nitrogen-containing heteroaromatic compounds.

[0135] As specific examples of the electron transporting material, the materials listed above can be used.

[0136] Next, in the light-emitting device shown in FIG. 1C, an electron injection layer 115 is formed on the electron transport layer 114 by vacuum deposition.

[0137] <Electron injection layer> The electron injection layer 115 is a layer containing a substance with high electron injection properties. The electron injection layer 115 may contain any of a variety of materials, including lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), lithium oxide (LiO x) or an alkaline earth metal, or a compound thereof, can be used. Also, a rare earth metal compound, such as erbium fluoride (ErF3), can be used. Also, an electride can be used for the electron injection layer 115. For example, an electride can be a substance in which a high concentration of electrons is added to a mixed oxide of calcium and aluminum. Note that the above-mentioned substance constituting the electron transport layer 114 can also be used.

[0138] In addition, a composite material containing an electron transporting material and a donor material (electron donor material) may be used for the electron injection layer 115. Such a composite material has excellent electron injection and transport properties because electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material that is excellent in transporting the generated electrons, and specifically, for example, the above-mentioned electron transporting material (metal complex, heteroaromatic compound, etc.) used for the electron transport layer 114 can be used. As the electron donor, any substance that exhibits electron donating properties to the organic compound may be used. Specifically, alkali metals, alkaline earth metals, and rare earth metals are preferable, and examples thereof include lithium, cesium, magnesium, calcium, erbium, and ytterbium. In addition, alkali metal oxides and alkaline earth metal oxides are preferable, and examples thereof include lithium oxide, calcium oxide, and barium oxide. In addition, a Lewis base such as magnesium oxide can also be used. In addition, an organic compound such as tetrathiafulvalene (abbreviation: TTF) can also be used.

[0139] <Charge generation layer> In the light-emitting device shown in FIG. 1B, the charge generation layer 104 has the function of injecting electrons into the EL layer 103a and injecting holes into the EL layer 103b when a voltage is applied between the first electrode 101 (anode) and the second electrode 102 (cathode).

[0140] The charge generating layer 104 may be configured to contain a hole transport material and an acceptor material (electron accepting material), or may be configured to contain an electron transport material and a donor material. By forming the charge generating layer 104 with such a configuration, it is possible to suppress an increase in driving voltage when an EL layer is laminated.

[0141] The hole transporting material, the acceptor material, the electron transporting material, and the donor material may each be the materials described above.

[0142] In addition, a vacuum process such as a deposition method, or a solution process such as a spin coating method or an inkjet method can be used to manufacture the light-emitting device shown in this embodiment. When a deposition method is used, a physical deposition method (PVD method) such as a sputtering method, an ion plating method, an ion beam deposition method, a molecular beam deposition method, or a vacuum deposition method, or a chemical deposition method (CVD method) can be used. In particular, the functional layers (hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer) and the charge generation layer included in the EL layer can be formed by a deposition method (vacuum deposition method, etc.), a coating method (dip coating method, die coating method, bar coating method, spin coating method, spray coating method, etc.), a printing method (inkjet method, screen (screen printing) method, offset (lithographic printing) method, flexo (relief printing) method, gravure method, microcontact method, etc.), or the like.

[0143] The materials of the functional layer and the charge generating layer constituting the EL layer 103 are not limited to the above-mentioned materials. For example, the material of the functional layer may be a polymer compound (oligomer, dendrimer, polymer, etc.), a medium molecular compound (a compound in the intermediate range between a low molecular weight and a high molecular weight: molecular weight 400 to 4000), an inorganic compound (quantum dot material, etc.), etc. may be used. Note that the quantum dot material may be a colloidal quantum dot material, an alloy type quantum dot material, a core-shell type quantum dot material, a core type quantum dot material, etc.

[0144] In the light-emitting device according to one embodiment of the present invention, light emission from a host material or an exciplex formed by the host material is difficult to be visually recognized, and therefore a light-emitting device in which visible light emission is difficult to be visually recognized and which efficiently emits near-infrared light can be realized.

[0145] In the light-emitting device according to one embodiment of the present invention, the luminance A [cd / m 2 ] and radiance B [W / sr / m 2 ] means 0≦A / B≦1[cd sr / W] (or 0

[0146] This embodiment mode can be combined with other embodiment modes as appropriate. In addition, in the case where a plurality of configuration examples are shown in one embodiment mode in this specification, the configuration examples can be combined as appropriate.

[0147] (Embodiment 2) In this embodiment, a light-emitting device of one embodiment of the present invention will be described with reference to FIGS.

[0148] The light emitting device of this embodiment has the light emitting device shown in Embodiment 1. Therefore, it is possible to realize a light emitting device that emits near infrared light and whose emission of visible light is difficult to visually recognize.

[0149] [Light emitting device configuration example 1] Fig. 2A shows a top view of the light emitting device, and Fig. 2B and Fig. 2C show cross-sectional views between dashed lines X1-Y1 and X2-Y2 in Fig. 2A. The light emitting device shown in Fig. 2A to Fig. 2C can be used, for example, in a lighting device. The light emitting device may be any of bottom emission, top emission, and dual emission.

[0150] ​2B includes a substrate 490a, a substrate 490b, a conductive layer 406, a conductive layer 416, an insulating layer 405, an organic EL device 450 (a first electrode 401, an EL layer 402, and a second electrode 403), and an adhesive layer 407. The light-emitting device described in Embodiment 1 can be used for the organic EL device 450.

[0151] Organic EL device 450 has a first electrode 401 on a substrate 490a, an EL layer 402 on the first electrode 401, and a second electrode 403 on the EL layer 402. Organic EL device 450 is encapsulated by substrate 490a, adhesive layer 407, and substrate 490b.

[0152] The ends of the first electrode 401, the conductive layer 406, and the conductive layer 416 are covered with an insulating layer 405. The conductive layer 406 is electrically connected to the first electrode 401, and the conductive layer 416 is electrically connected to the second electrode 403. The conductive layer 406 covered with the insulating layer 405 via the first electrode 401 functions as an auxiliary wiring and is electrically connected to the first electrode 401. Having an auxiliary wiring electrically connected to the electrode of the organic EL device 450 is preferable because it can suppress a voltage drop caused by the resistance of the electrode. The conductive layer 406 may be provided on the first electrode 401. Also, an auxiliary wiring electrically connected to the second electrode 403 may be provided on the insulating layer 405 or the like.

[0153] The substrate 490a and the substrate 490b can each be made of glass, quartz, ceramic, sapphire, organic resin, etc. When the substrate 490a and the substrate 490b are made of a flexible material, the flexibility of the light-emitting device can be increased.

[0154] The light-emitting surface of the light-emitting device may be provided with a light extraction structure to increase the light extraction efficiency, an antistatic film to suppress the adhesion of dust, a water-repellent film to prevent the adhesion of dirt, a hard coat film to suppress the occurrence of scratches during use, an impact absorbing layer, etc.

[0155] Examples of insulating materials that can be used for the insulating layer 405 include resins such as acrylic resin and epoxy resin, and inorganic insulating materials such as silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, and aluminum oxide.

[0156] For the adhesive layer 407, various curing adhesives such as a photo-curing adhesive such as an ultraviolet curing adhesive, a reaction curing adhesive, a heat curing adhesive, and an anaerobic adhesive can be used. Examples of such adhesives include epoxy resin, acrylic resin, silicone resin, phenolic resin, polyimide resin, imide resin, PVC (polyvinyl chloride) resin, PVB (polyvinyl butyral) resin, and EVA (ethylene vinyl acetate) resin. In particular, a material with low moisture permeability such as epoxy resin is preferable. A two-liquid mixed resin may also be used. An adhesive sheet or the like may also be used.

[0157] The light emitting device shown in FIG. 2C includes barrier layer 490c, conductive layer 406, conductive layer 416, insulating layer 405, organic EL device 450, adhesive layer 407, barrier layer 423, and substrate 490b.

[0158] Barrier layer 490c shown in FIG. 2C includes substrate 420, adhesion layer 422, and high barrier insulating layer 424.

[0159] 2C, organic EL device 450 is disposed between insulating layer 424 with high barrier properties and barrier layer 423. Therefore, even if a resin film with relatively low waterproof properties is used for substrate 420 and substrate 490b, it is possible to prevent impurities such as water from entering the organic EL device and shortening its lifespan.

[0160] For the substrate 420 and the substrate 490b, for example, polyester resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), polyacrylonitrile resin, acrylic resin, polyimide resin, polymethyl methacrylate resin, polycarbonate (PC) resin, polyethersulfone (PES) resin, polyamide resin (nylon, aramid, etc.), polysiloxane resin, cycloolefin resin, polystyrene resin, polyamideimide resin, polyurethane resin, polyvinyl chloride resin, polyvinylidene chloride resin, polypropylene resin, polytetrafluoroethylene (PTFE) resin, ABS resin, cellulose nanofiber, etc. For the substrate 420 and the substrate 490b, glass having a thickness sufficient to provide flexibility may be used.

[0161] The insulating layer 424 having high barrier properties is preferably an inorganic insulating film. Examples of the inorganic insulating film that can be used include a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon nitride oxide film, an aluminum oxide film, and an aluminum nitride film. A hafnium oxide film, an yttrium oxide film, a zirconium oxide film, a gallium oxide film, a tantalum oxide film, a magnesium oxide film, a lanthanum oxide film, a cerium oxide film, and a neodymium oxide film may also be used. Two or more of the above insulating films may be stacked.

[0162] The barrier layer 423 preferably has at least one inorganic film. For example, the barrier layer 423 may have a single layer structure of an inorganic film or a laminated structure of an inorganic film and an organic film. The inorganic insulating film is suitable as the inorganic film. The laminated structure may be, for example, a silicon oxynitride film, a silicon oxide film, an organic film, a silicon oxide film, and a silicon nitride film formed in this order. By forming the barrier layer into a laminated structure of an inorganic film and an organic film, impurities (typically, hydrogen, water, etc.) that may enter the organic EL device 450 can be suitably suppressed.

[0163] The insulating layer 424 and the organic EL device 450 having high barrier properties can be formed directly on the substrate 420 having flexibility. In this case, the adhesive layer 422 is not necessary. The insulating layer 424 and the organic EL device 450 can be formed on a hard substrate via a peeling layer and then transferred to the substrate 420. For example, the insulating layer 424 and the organic EL device 450 may be peeled off from the hard substrate by applying heat, force, laser light, or the like to the peeling layer, and then transferred to the substrate 420 by bonding the substrate 420 using the adhesive layer 422. As the peeling layer, for example, a laminated structure of inorganic films including a tungsten film and a silicon oxide film, an organic resin film such as polyimide, or the like can be used. When a hard substrate is used, the insulating layer 424 can be formed at a high temperature compared to a resin substrate, and therefore the insulating layer 424 can be made into a dense insulating film having extremely high barrier properties.

[0164] [Light-emitting device configuration example 2] The light-emitting device of one embodiment of the present invention can be a passive matrix type or an active matrix type. An active matrix type light-emitting device will be described with reference to FIG.

[0165] Fig. 3A shows a top view of the light emitting device, and Fig. 3B is a cross-sectional view taken along dashed line AA' shown in Fig. 3A.

[0166] The active matrix light emitting device shown in FIG. 3A and FIG. 3B includes a pixel portion 302, a circuit portion 303, a circuit portion 304a, and a circuit portion 304b.

[0167] Each of the circuit portion 303, the circuit portion 304a, and the circuit portion 304b can function as a scanning line driver circuit (gate driver) or a signal line driver circuit (source driver), or may be a circuit that electrically connects an external gate driver or source driver to the pixel portion 302.

[0168] A lead wiring 307 is provided on the first substrate 301. The lead wiring 307 is electrically connected to an FPC 308, which is an external input terminal. The FPC 308 transmits signals (e.g., video signals, clock signals, start signals, reset signals, etc.) and potentials from the outside to the circuit portion 303, the circuit portion 304a, and the circuit portion 304b. A printed wiring board (PWB) may be attached to the FPC 308. The configuration shown in FIGS. 3A and 3B can also be called a light-emitting module having a light-emitting device (or a light-emitting apparatus) and an FPC.

[0169] The pixel portion 302 includes a plurality of pixels each including an organic EL device 317, a transistor 311, and a transistor 312. The light-emitting device described in Embodiment 1 can be used for the organic EL device 317. The transistor 312 is electrically connected to a first electrode 313 of the organic EL device 317. The transistor 311 functions as a switching transistor. The transistor 312 functions as a current control transistor. Note that the number of transistors included in each pixel is not particularly limited and can be appropriately provided as necessary.

[0170] The circuit portion 303 has a plurality of transistors including a transistor 309 and a transistor 310. The circuit portion 303 may be formed of a circuit including transistors of the same polarity (either N-type or P-type), or may be formed of a CMOS circuit including an N-type transistor and a P-type transistor. The circuit portion 303 may also be configured to have an external driver circuit.

[0171] The structure of the transistor included in the light-emitting device of this embodiment is not particularly limited. For example, a planar transistor, a staggered transistor, an inverted staggered transistor, or the like can be used. In addition, either a top-gate type or a bottom-gate type transistor structure may be used. Alternatively, gates may be provided above and below a semiconductor layer in which a channel is formed.

[0172] The crystallinity of a semiconductor material used in a transistor is not particularly limited, and any of an amorphous semiconductor and a crystalline semiconductor (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor partially having a crystalline region) may be used. The use of a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0173] The semiconductor layer of the transistor preferably contains a metal oxide (also referred to as an oxide semiconductor). Alternatively, the semiconductor layer of the transistor may contain silicon. Examples of silicon include amorphous silicon and crystalline silicon (such as low-temperature polysilicon and single crystal silicon).

[0174] The semiconductor layer preferably contains, for example, indium, M (M is one or more selected from gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium), and zinc. In particular, M is preferably one or more selected from aluminum, gallium, yttrium, and tin.

[0175] In particular, it is preferable to use an oxide containing indium (In), gallium (Ga), and zinc (Zn) (also referred to as IGZO) as the semiconductor layer.

[0176] When the semiconductor layer is an In-M-Zn oxide, the sputtering target used to deposit the In-M-Zn oxide preferably has an atomic ratio of In equal to or greater than the atomic ratio of M. Examples of atomic ratios of metal elements in such sputtering targets include In:M:Zn=1:1:1, In:M:Zn=1:1:1.2, In:M:Zn=2:1:3, In:M:Zn=3:1:2, In:M:Zn=4:2:3, In:M:Zn=4:2:4.1, In:M:Zn=5:1:6, In:M:Zn=5:1:7, In:M:Zn=5:1:8, In:M:Zn=6:1:6, In:M:Zn=5:2:5, and the like.

[0177] The transistors included in the circuit portion 303, the circuit portion 304a, and the circuit portion 304b may have the same structure or may have different structures from the transistors included in the pixel portion 302. The transistors included in the circuit portion 303, the circuit portion 304a, and the circuit portion 304b may all have the same structure or may have two or more types. Similarly, the transistors included in the pixel portion 302 may all have the same structure or may have two or more types.

[0178] An end of the first electrode 313 is covered with an insulating layer 314. For the insulating layer 314, an organic compound such as a negative photosensitive resin or a positive photosensitive resin (acrylic resin) or an inorganic compound such as silicon oxide, silicon oxynitride, or silicon nitride can be used. The upper end or lower end of the insulating layer 314 preferably has a curved surface having a curvature. This can improve the coverage of the film formed on the insulating layer 314.

[0179] An EL layer 315 is provided over the first electrode 313, and a second electrode 316 is provided over the EL layer 315. The EL layer 315 has a light-emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, a charge generation layer, and the like.

[0180] The plurality of transistors and the plurality of organic EL devices 317 are sealed by the first substrate 301, the second substrate 306, and the sealant 305. A space 318 surrounded by the first substrate 301, the second substrate 306, and the sealant 305 may be filled with an inert gas (nitrogen, argon, etc.) or an organic substance (including the sealant 305).

[0181] An epoxy resin or glass frit can be used for the sealant 305. Note that it is preferable to use a material that is as impermeable to moisture and oxygen as possible for the sealant 305. When glass frit is used as the sealant, it is preferable that the first substrate 301 and the second substrate 306 are glass substrates in terms of adhesiveness.

[0182] This embodiment mode can be combined with other embodiment modes as appropriate.

[0183] (Embodiment 3) In this embodiment, electronic devices in which the light-emitting device of one embodiment of the present invention can be used will be described with reference to FIGS.

[0184] A light-emitting device according to one embodiment of the present invention emits near-infrared light and is difficult to visually recognize as emitting visible light. Using such a light-emitting device, an electronic device that performs authentication, analysis, diagnosis, and the like using near-infrared light can be realized. In the electronic device, the visible light emitted by the light-emitting device can be prevented from becoming noise in authentication, analysis, diagnosis, and the like using near-infrared light. This can improve the accuracy of authentication, analysis, diagnosis, and the like. Furthermore, in electronic devices for security-related or military applications, imaging using near-infrared light can be performed without being noticed by people in the vicinity.

[0185] FIG. 4A shows a biometric authentication device for finger veins, and includes a housing 911, a light source 912, a detection stage 913, and the like. By placing a finger on the detection stage 913, the shape of the veins can be imaged. A light source 912 that emits near-infrared light is provided on the upper part of the detection stage 913, and an imaging device 914 is provided on the lower part. The detection stage 913 is made of a material that transmits near-infrared light, and the near-infrared light that is irradiated from the light source 912 and transmitted through the finger can be imaged by the imaging device 914. An optical system may be provided between the detection stage 913 and the imaging device 914. The above-mentioned device configuration can also be used in a biometric authentication device for palm veins.

[0186] The light-emitting device according to one embodiment of the present invention can be used for the light source 912. The light-emitting device according to one embodiment of the present invention can be installed in a curved shape and can irradiate light uniformly to an object. In particular, the light-emitting device is preferably a light-emitting device that emits near-infrared light having the strongest peak intensity in a wavelength range of 760 nm to 900 nm. The position of veins can be detected by receiving light that has passed through a finger, a palm, or the like and imaging it. This function can be used for biometric authentication. Furthermore, by combining the light-emitting device with a global shutter system, highly accurate sensing is possible even if the object moves.

[0187] Furthermore, the light source 912 can have a plurality of light emitting units, such as light emitting units 915, 916, and 917 shown in Fig. 4B. Each of the light emitting units 915, 916, and 917 may emit light at a different wavelength, and each can also irradiate light at a different timing. Therefore, by changing the wavelength and angle of the irradiated light, different images can be captured continuously, and therefore multiple images can be used for authentication, thereby achieving high security.

[0188] FIG. 4C shows a biometric authentication device for palm veins, which includes a housing 921, an operation button 922, a detection unit 923, a light source 924 that emits near-infrared light, and the like. The shape of the veins in the palm can be recognized by holding the hand over the detection unit 923. A personal identification number or the like can also be input using the operation button. A light source 924 is disposed around the detection unit 923 and irradiates an object (hand). Then, reflected light from the object is incident on the detection unit 923. A light-emitting device according to one embodiment of the present invention can be used for the light source 924. An imaging device 925 is disposed directly below the detection unit 923 and can capture an image of the object (the entire image of the hand). Note that an optical system may be provided between the detection unit 923 and the imaging device 925. The above-described device configuration can also be used for a biometric authentication device for finger veins.

[0189] FIG. 4D shows a non-destructive inspection device, which includes a housing 931, an operation panel 932, a transport mechanism 933, a monitor 934, a detection unit 935, a light source 938 that emits near-infrared light, and the like. The light-emitting device according to one embodiment of the present invention can be used as the light source 938. A member to be inspected 936 is transported by the transport mechanism 933 to a position directly below the detection unit 935. The member to be inspected 936 is irradiated with near-infrared light from the light source 938, and the transmitted light is captured by an imaging device 937 provided in the detection unit 935. The captured image is displayed on the monitor 934. The member is then transported to the exit of the housing 931, where defective products are separated and collected. By capturing images using near-infrared light, defective elements such as defects and foreign bodies inside the member to be inspected can be detected non-destructively and at high speed.

[0190] FIG. 4E illustrates a mobile phone, which includes a housing 981, a display portion 982, operation buttons 983, an external connection port 984, a speaker 985, a microphone 986, a first camera 987, a second camera 988, and the like. The mobile phone includes a touch sensor in the display portion 982. The housing 981 and the display portion 982 are flexible. Any operation, such as making a call or inputting characters, can be performed by touching the display portion 982 with a finger, a stylus, or the like. The first camera 987 can acquire a visible light image, and the second camera 988 can acquire an infrared light image (near-infrared light image). The mobile phone or the display portion 982 illustrated in FIG. 4E may include a light-emitting device of one embodiment of the present invention.

[0191] This embodiment mode can be combined with other embodiment modes as appropriate. EXAMPLES

[0192] In this example, a light-emitting device according to one embodiment of the present invention was manufactured and evaluated, and the results are described.

[0193] In this example, a device 1 to which one embodiment of the present invention is applied and a comparative device 2 for comparison were fabricated as light-emitting devices, and the results of evaluation thereof will be described.

[0194] The structures of Device 1 and Comparative Device 2 used in this example are shown in Fig. 5, and their specific configurations are shown in Table 1. The chemical formulas of the materials used in this example are shown below.

[0195] [Table 1]

[0196] [ka]

[0197] <Device Creation> As shown in FIG. 5 , device 1 and comparative device 2 shown in this embodiment have a structure in which a first electrode 801 is formed on a substrate 800, and an EL layer 802 is formed by sequentially stacking a hole injection layer 811, a hole transport layer 812, an emitting layer 813, an electron transport layer 814, and an electron injection layer 815 on the first electrode 801, and a second electrode 803 is stacked on the electron injection layer 815.

[0198] First, a first electrode 801 was formed on a substrate 800. The electrode area was 4 mm 2 The dimensions of the first electrode 801 were (2 mm×2 mm). A glass substrate was used as the substrate 800. The first electrode 801 was formed by depositing indium tin oxide containing silicon oxide (ITSO) by a sputtering method. The thickness of the first electrode 801 was 70 nm in the device 1 and 110 nm in the comparative device 2. In this example, the first electrode 801 functions as an anode.

[0199] As a pretreatment, the surface of the substrate was washed with water, baked at 200°C for 1 hour, and then subjected to UV ozone treatment for 370 seconds. -4 The substrate was introduced into a vacuum deposition apparatus whose inside had been reduced in pressure to about Pa, and vacuum baking was carried out at 170° C. for 30 minutes in a heating chamber in the vacuum deposition apparatus, and then the substrate was allowed to cool for about 30 minutes.

[0200] Next, a hole injection layer 811 was formed on the first electrode 801. The hole injection layer 811 was formed by evaporating 1×10 -4 After reducing the pressure to about Pa, 1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) and molybdenum oxide were co-evaporated in a weight ratio of DBT3P-II:molybdenum oxide = 2:1 to form the hole injection layer 811. The thickness of the hole injection layer 811 was 120 nm in the device 1 and 60 nm in the comparative device 2.

[0201] Next, a hole transport layer 812 was formed on the hole injection layer 811. The hole transport layer 812 was formed by depositing N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) to a thickness of 20 nm.

[0202] Next, the light-emitting layer 813 was formed on the hole-transporting layer 812 .

[0203] In device 1, 2,8-bis[3-(dibenzothiophen-4-yl)phenyl]benzofuro[2,3-b]quinoxaline (abbreviation: 2,8mDBtP2Bfqn) and 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: m-MTDATA) were used as host materials, and bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-2-benzo[g]quinoxalinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κC) was used as guest material (phosphorescent material). 2 O,O') Iridium (III) (abbreviation: [Ir(dmdpbq)2(dpm)]) was used and co-deposited in a weight ratio of 2,8mDBtP2Bfqn:m-MTDATA:[Ir(dmdpbq)2(dpm)]=0.7:0.3:0.1. The thickness of the light-emitting layer 813 was 40 nm.

[0204] In the comparative device 2, 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II) and PCBBiF were used as the host material, and [Ir(dmdpbq)2(dpm)] was used as the guest material (phosphorescent material), and they were co-deposited in a weight ratio of 2mDBTBPDBq-II:PCBBiF:[Ir(dmdpbq)2(dpm)]=0.7:0.3:0.1. The thickness of the light-emitting layer 813 was 40 nm.

[0205] Next, an electron transport layer 814 was formed on the light emitting layer 813 .

[0206] Electron transport layer 814 of device 1 was formed by sequentially depositing 2,8mDBtP2Bfqn to a thickness of 20 nm and 2,9-bis(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBphen) to a thickness of 70 nm.

[0207] The electron transport layer 814 of the comparative device 2 was formed by successively depositing 2mDBTBPDBq-II to a thickness of 20 nm and NBphen to a thickness of 70 nm.

[0208] Next, the electron injection layer 815 was formed on the electron transport layer 814. The electron injection layer 815 was formed by vapor deposition using lithium fluoride (LiF) so as to have a film thickness of 1 nm.

[0209] Next, a second electrode 803 was formed on the electron injection layer 815. The second electrode 803 was formed by vapor deposition of aluminum so as to have a film thickness of 200 nm. In this example, the second electrode 803 functions as a cathode.

[0210] Through the above steps, a light-emitting device including an EL layer 802 sandwiched between a pair of electrodes was formed on a substrate 800. Note that the hole injection layer 811, the hole transport layer 812, the light-emitting layer 813, the electron transport layer 814, and the electron injection layer 815 described in the above steps are functional layers that constitute the EL layer in one embodiment of the present invention. In addition, in all of the deposition steps in the above-described manufacturing method, deposition by resistance heating was used.

[0211] The light-emitting device fabricated as described above is sealed with another substrate (not shown). When sealing is performed using another substrate (not shown), another substrate (not shown) coated with an adhesive that is hardened by ultraviolet light is fixed on the substrate 800 in a glove box with a nitrogen atmosphere, and the substrates are bonded together so that the adhesive adheres to the periphery of the light-emitting device formed on the substrate 800. During sealing, 365 nm ultraviolet light is applied at 6 J / cm. 2 The adhesive was solidified by irradiation and then stabilized by heat treatment at 80°C for 1 hour.

[0212] <Operation characteristics of light-emitting devices> The operating characteristics of Device 1 and Comparative Device 2 were measured. The measurements were carried out at room temperature (an atmosphere maintained at 25° C.).

[0213] Figures 6 and 7 show the current density of 50 mA / cm for Device 1 and Comparative Device 2. 2 7 shows the emission spectrum when a current is applied at a current density of 1000 . In the emission spectrum, the wavelength range of 380 nm to 749 nm is the result of measurement using a spectroradiometer (SR-UL1R, manufactured by Topcon Corporation), and the wavelength range of 750 nm to 1030 nm is the result of measurement using a near-infrared spectroradiometer (SR-NIR, manufactured by Topcon Corporation). Note that FIG. 7 differs from FIG. 6 in that the vertical axis is expressed logarithmically. Furthermore, FIG. 7 also shows a luminosity curve based on the scotopic luminosity (CIE (1951) Scotopic V'(λ)).

[0214] Also, Table 2 shows the current of 2 mA (current density of 50 mA / cm 2) are shown the main initial characteristic values ​​of Device 1 and Comparative Device 2. Note that the radiant flux and external quantum efficiency were calculated using radiance, assuming that the light distribution characteristic of the light-emitting device is a Lambertian type.

[0215] [Table 2]

[0216] As shown in the reference example (FIG. 13), the PL spectrum of [Ir(dmdpbq)2(dpm)] in dichloromethane solution showed a maximum peak at 807 nm (1.54 eV). The rise of the maximum peak on the short wavelength side was at 754 nm (1.64 eV).

[0217] As shown in FIG. 6, the maximum peak wavelength of the emission spectrum of Device 1 was 801 nm, and the maximum peak wavelength of the emission spectrum of Comparative Device 2 was 793 nm. It was found that both devices emitted near-infrared light originating from [Ir(dmdpbq)2(dpm)] contained in the light-emitting layer 813.

[0218] 6, the rising wavelength on the short wavelength side of the maximum peak in the emission spectrum of Device 1 was 754 nm. The rising wavelength on the short wavelength side of the maximum peak in the emission spectrum of Comparative Device 2 was 751 nm. It was found that the rising wavelengths on the short wavelength side of the maximum peak in both Device 1 and Comparative Device 2 were sufficiently long.

[0219] As shown in FIG. 7, the emission spectrum of the comparative device 2 was confirmed to have a relatively large emission peak (peak wavelength 523 nm) in the wavelength range of visible light. By comparing with the luminosity curve, it was found that the light emitted by the comparative device 2 contains light in a wavelength range with high luminosity among visible light. In other words, the emission of visible light is easily recognized in the comparative device 2. On the other hand, the spectral radiance in the wavelength range of visible light of the device 1 was lower than that of the comparative device 2. In addition, the maximum peak wavelength in the wavelength range of visible light of the emission spectrum of the device 1 was 638 nm, and the emission spectrum of the device 1 had an emission peak in a wavelength range with low luminosity among visible light. From this, it was found that the device 1 emits visible light in a wavelength range with low luminosity and has low emission intensity in the wavelength range of visible light.

[0220] As shown in Table 2, the luminance / radiance (luminance divided by radiance) of Device 1 was 0.05 cd sr / W, and the luminance / radiance of Comparative Device 2 was 2.1 cd sr / W. This shows that Device 1 has an extremely low visible light emission intensity compared to the near-infrared light emission intensity. Therefore, Device 1 can be said to be a light-emitting device that emits near-infrared light, but the visible light emission is difficult to recognize. On the other hand, Comparative Device 2 has a high visible light emission intensity compared to the near-infrared light emission intensity, and the visible light is easily recognized.

[0221] As shown in Table 2, the external quantum efficiency of Device 1 was 2.5%. This is a high value for the external quantum efficiency of a light-emitting device that has a weak emission intensity of visible light and mainly emits near-infrared light. The external quantum efficiency of Device 1 was calculated from the results of measurements using a near-infrared spectroradiometer (SR-NIR, manufactured by Topcon Corporation) with a wavelength range of 600 nm to 1030 nm.

[0222] In addition, a mixed film A of two host materials used in the device 1 and a mixed film B of two host materials used in the comparative device 2 were each prepared, and their emission spectra (PL spectra) were measured.

[0223] Mixture film A was formed on a quartz substrate by co-evaporation of 2,8mDBtP2Bfqn and m-MTDATA in a ratio of 2,8mDBtP2Bfqn:m-MTDATA = 0.7:0.3 (weight ratio) to a thickness of 50 nm. Here, 2,8mDBtP2Bfqn and m-MTDATA are a combination that forms an exciplex.

[0224] Mixture film B was formed on a quartz substrate by co-evaporation of 2mDBTBPDBq-II and PCBBiF at a weight ratio of 2mDBTBPDBq-II:PCBBiF=0.7:0.3 to a thickness of 50 nm. Here, 2mDBTBPDBq-II and PCBBiF are a combination that form an exciplex.

[0225] The HOMO and LUMO levels of each host material are shown in Table 3. The HOMO and LUMO levels were derived from the electrochemical properties (reduction potential and oxidation potential) of the material measured by cyclic voltammetry (CV). Table 3 also shows the HOMO and LUMO levels of the guest materials used in Device 1 and Comparative Device 2.

[0226] [Table 3]

[0227] Table 3 describes the HOMO and LUMO levels of the two host materials used in device 1 and mixed film A. It can be seen that the HOMO level of m-MTDATA is higher than the HOMO level of [Ir(dmdpbq)2(dpm)] and the HOMO level of 2,8mDBtP2Bfqn. Specifically, the HOMO level of m-MTDATA (-4.98 eV) is 0.56 eV higher than the HOMO level of [Ir(dmdpbq)2(dpm)] (-5.54 eV). In addition, the difference between the HOMO level of m-MTDATA (-4.98 eV) and the LUMO level of 2,8mDBtP2Bfqn (-3.31 eV) is 1.67 eV, which is smaller than the difference (2.05 eV) between the HOMO level (-5.54 eV) and LUMO level (-3.49 eV) of [Ir(dmdpbq)2(dpm)].

[0228] Next, the HOMO and LUMO levels of the two host materials used in the comparative device 2 and the mixed film B are described with reference to Table 3. It can be seen that the HOMO level of PCBBiF is higher than the HOMO level of [Ir(dmdpbq)2(dpm)] and the HOMO level of 2mDBTBPDBq-II. Specifically, the HOMO level of PCBBiF (-5.36 eV) is 0.18 eV higher than the HOMO level of [Ir(dmdpbq)2(dpm)] (-5.54 eV). In addition, the difference between the HOMO level of PCBBiF (-5.36 eV) and the LUMO level of 2mDBTBPDBq-II (-2.94 eV) is 2.42 eV, which is larger than the difference (2.05 eV) between the HOMO level (-5.54 eV) and LUMO level (-3.49 eV) of [Ir(dmdpbq)2(dpm)].

[0229] The PL spectrum was measured at room temperature using a fluorometer (FS920, manufactured by Hamamatsu Photonics K.K.).

[0230] Figures 8 and 9 show the PL spectrum of the mixed film A and the emission spectrum (similar to Figures 6 and 7) of the device 1. Note that Figure 9 differs from Figure 8 in that the vertical axis is logarithmic.

[0231] 10 and 11 show the PL spectrum of the mixed film B and the emission spectrum (similar to FIG. 6) of the comparative device 2. Note that FIG. 11 differs from FIG. 10 in that the vertical axis is logarithmic.

[0232] As shown in Figure 8, the maximum peak wavelength of the PL spectrum of the mixed film A was 678 nm. From the difference between the HOMO level of m-MTDATA and the LUMO level of 2,8mDBtP2Bfqn, it can be said that the emission of the mixed film A originates from the exciplex formed by these two materials.

[0233] As shown in Figure 10, the maximum peak wavelength of the PL spectrum of the mixed film B was 516 nm. From the difference between the HOMO level of PCBBiF and the LUMO level of 2mDBTBPDBq-II, it can be said that the emission of the mixed film B originates from the exciplex formed by these two materials.

[0234] The emission peak wavelength in the visible light region of Comparative Device 2 was close to the maximum peak wavelength of the PL spectrum of Mixed Film B, indicating that the visible light emission observed in Comparative Device 2 was due to the exciplex formed by the two host materials.

[0235] The maximum peak wavelength of the PL spectrum of the mixed film A is included in the wavelength range with low luminosity. Therefore, the luminescence originating from the exciplex formed by the two host materials used in the mixed film A has low luminosity. Therefore, the device 1 is a light-emitting device in which the luminescence originating from the exciplex is difficult to visually recognize, and the luminescence of visible light is difficult to visually recognize.

[0236] As described above, the HOMO level of m-MTDATA used in the mixed film A is 0.56 eV higher than the HOMO level of [Ir(dmdpbq)2(dpm)]. In addition, the difference between the HOMO level of m-MTDATA and the LUMO level of 2,8mDBtP2Bfqn is smaller than the difference between the HOMO level and the LUMO level of [Ir(dmdpbq)2(dpm)]. This allows the emission wavelength of the exciplex formed by these two materials to be longer, and the luminosity of the emission derived from the exciplex to be reduced.

[0237] As described above, this example shows that by controlling the emission of the exciplex formed from two host materials to be light having a wavelength with low visual sensitivity, it is possible to fabricate a light-emitting device that emits near-infrared light and whose visible light emission is difficult to visually recognize.

[0238] (Reference example) The bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-2-benzo[g]quinoxalinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ) used in the above examples 2 The synthesis method for (O,O') iridium(III) (abbreviation: [Ir(dmdpbq)2(dpm)]) is specifically described. The structure of [Ir(dmdpbq)2(dpm)] is shown below.

[0239] [ka]

[0240] <Step 1: Synthesis of 2,3-bis-(3,5-dimethylphenyl)-2-benzo[g]quinoxaline (abbreviation: Hdmdpbq)> First, in step 1, Hdmdpbq was synthesized. 3.20 g of 3,3',5,5'-tetramethylbenzyl, 1.97 g of 2,3-diaminonaphthalene, and 60 mL of ethanol were placed in a three-necked flask equipped with a reflux condenser, and the inside of the flask was replaced with nitrogen, and then the mixture was stirred at 90°C for 7.5 hours. After a predetermined time had passed, the solvent was distilled off. The product was then purified by silica gel column chromatography using toluene as a developing solvent to obtain the target product (yellow solid, yield 3.73 g, 79%). The synthesis scheme of step 1 is shown in (a-1).

[0241] [ka]

[0242] Nuclear magnetic resonance spectroscopy of the yellow solid obtained in step 1 ( 1The results of the analysis by H-NMR are shown below. The analysis results showed that Hdmdpbq was obtained.

[0243] The obtained material 1 The 1 H NMR data is shown below. 1 H-NMR.δ(CD2Cl2):2.28(s,12H),7.01(s,2H),7.16(s,4H),7.56-7.58(m,2H),8.11-8.13(m,2H),8.74(s,2H).

[0244] <Step 2: Synthesis of di-μ-chloro-tetrakis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-2-benzo[g]quinoxalinyl-κN]phenyl-κC}diiridium(III) (abbreviation: [Ir(dmdpbq)2Cl]2)> Next, in step 2, [Ir(dmdpbq)2Cl]2 was synthesized. 15 mL of 2-ethoxyethanol, 5 mL of water, 1.81 g of Hdmdpbq obtained in step 1, and 0.66 g of iridium chloride hydrate (IrCl3·H2O) (Furuya Metal Co., Ltd.) were placed in a recovery flask equipped with a reflux condenser, and the atmosphere in the flask was replaced with argon. After that, the mixture was irradiated with microwaves (2.45 GHz, 100 W) for 2 hours to cause a reaction. After the specified time had passed, the resulting residue was suction filtered and washed with methanol to obtain the target product (black solid, yield 1.76 g, 81%). The synthesis scheme of step 2 is shown in (a-2).

[0245] [ka]

[0246] <Step 3: Synthesis of [Ir(dmdpbq)2(dpm)]> In step 3, [Ir(dmdpbq)2(dpm)] was synthesized. 20 mL of 2-ethoxyethanol, 1.75 g of [Ir(dmdpbq)2Cl]2 obtained in step 2, 0.50 g of dipivaloylmethane (abbreviation: Hdpm), and 0.95 g of sodium carbonate were placed in a recovery flask equipped with a reflux tube, and the atmosphere in the flask was replaced with argon. Then, microwaves (2.45 GHz, 100 W) were irradiated for 3 hours. The residue obtained was suction filtered with methanol, and then washed with water and methanol. The obtained solid was purified by silica gel column chromatography using dichloromethane as a developing solvent, and then recrystallized with a mixed solvent of dichloromethane and methanol to obtain the target product (dark green solid, yield 0.42 g, 21% yield). 0.41 g of the obtained dark green solid was purified by sublimation using a train sublimation method. The conditions for the sublimation purification were as follows: the dark green solid was heated at 300°C under a pressure of 2.7 Pa and argon gas at a flow rate of 10.5 mL / min. After the sublimation purification, a dark green solid was obtained in a yield of 78%. The synthesis scheme for step 3 is shown in (a-3).

[0247] [ka]

[0248] Nuclear magnetic resonance spectroscopy of the dark green solid obtained in step 3 ( 1 The results of the analysis by H-NMR are shown below. The analysis results showed that [Ir(dmdpbq)2(dpm)] was obtained.

[0249] 1 H-NMR.δ(CD2Cl2):0.75(s,18H),0.97(s,6H),2.01(s,6H),2.52(s,12H),4.86(s,1H),6.39(s,2H),7.15 (s,2H),7.31(s,2H),7.44-7.51(m,4H),7.80(d,2H),7.86(s,4H),8.04(d,2H),8.42(s,2H),8.58(s,2H).

[0250] Next, the results of measuring the ultraviolet-visible absorption spectrum (hereinafter simply referred to as the “absorption spectrum”) and the emission spectrum (PL spectrum) of a dichloromethane solution of [Ir(dmdpbq)2(dpm)] are shown in FIG. 12 and FIG. 13.

[0251] The absorption spectrum was measured using an ultraviolet-visible spectrophotometer (V550, manufactured by JASCO Corporation) by placing a dichloromethane solution (0.010 mmol / L) in a quartz cell and measuring at room temperature. The emission spectrum was measured using a fluorometer (FS920, manufactured by Hamamatsu Photonics Corporation) by placing a deoxygenated dichloromethane solution (0.010 mmol / L) in a quartz cell under a nitrogen atmosphere, sealing it, and measuring at room temperature.

[0252] The absorption spectrum shown in FIG. 12 is the result of subtracting the absorption spectrum measured by putting only dichloromethane in a quartz cell from the absorption spectrum measured by putting a dichloromethane solution (0.010 mmol / L) in a quartz cell.

[0253] As shown in Figure 13, [Ir(dmdpbq)2(dpm)] exhibited an emission peak at 807 nm (1.54 eV), and near-infrared emission was observed from the dichloromethane solution. The onset of the emission peak was at 754 nm (1.64 eV). [Explanation of symbols]

[0254] 101: first electrode, 102: second electrode, 103: EL layer, 103a: EL layer, 103b: EL layer, 104: charge generation layer, 111: hole injection layer, 112: hole transport layer, 113: light emitting layer, 114: electron transport layer, 115: electron injection layer, 301: substrate, 302: pixel section, 303: circuit section, 304a: circuit section, 304b: circuit section, 305: seal material, 306: substrate, 307: wiring, 308: FPC, 309: transistor 310: transistor, 311: transistor, 312: transistor, 313: first electrode, 314: insulating layer, 315: EL layer, 316: second electrode, 317: organic EL device, 318: space, 401: first electrode, 402: EL layer, 403: second electrode, 405: insulating layer, 406: conductive layer, 407: adhesive layer, 416: conductive layer, 420: substrate, 422: adhesive layer, 423: barrier layer, 424: Insulating layer, 450: organic EL device, 490a: substrate, 490b: substrate, 490c: barrier layer, 800: substrate, 801: first electrode, 802: EL layer, 803: second electrode, 811: hole injection layer, 812: hole transport layer, 813: light emitting layer, 814: electron transport layer, 815: electron injection layer, 911: housing, 912: light source, 913: detection stage, 914: imaging device, 915: light emitting section, 916: light emitting section, 917: light emitting section, 921: housing, 922: operation button, 923: detection section, 924: light source, 925: imaging device, 931: housing, 932: operation panel, 933: transport mechanism, 934: monitor, 935: detection unit, 936: inspected member, 937: imaging device, 938: light source, 981: housing, 982: display section, 983: operation button, 984: external connection port, 985: speaker, 986: microphone, 987: camera, 988: camera

Claims

1. a light-emitting device having a light-emitting layer, the light-emitting layer comprises a light-emitting organic compound and a host material; the maximum peak wavelength of the emission spectrum of the light-emitting device is 750 nm or more and 900 nm or less; Luminance A [cd / m ２ ] and radiance B [W / sr / m ２ ] satisfies 0 < A / B ≦ 1 [cd sr / W], A light-emitting device, wherein the difference between the HOMO level and the LUMO level of the host material is 1.35 eV or more and 2.25 eV or less.

2. a light-emitting device having a light-emitting layer, the light-emitting layer comprises a light-emitting organic compound and a host material; the maximum peak wavelength of the emission spectrum of the light-emitting device is 750 nm or more and 900 nm or less; Luminance A [cd / m ２ ] and radiance B [W / sr / m ２ ] satisfies 0 < A / B ≦ 1 [cd sr / W], the host material comprises a first organic compound and a second organic compound; the first organic compound and the second organic compound are a combination that forms an exciplex, a HOMO level of the first organic compound is higher than a HOMO level of the second organic compound; a difference between a HOMO level of the first organic compound and a LUMO level of the second organic compound is smaller than a difference between a HOMO level and a LUMO level of the light-emitting organic compound.

3. In claim 2, A light-emitting device, wherein a difference between a HOMO level of the first organic compound and a LUMO level of the second organic compound is 1.35 eV or more and 2.25 eV or less.

4. a light-emitting device having a light-emitting layer, the light-emitting layer comprises a light-emitting organic compound and a host material; the maximum peak wavelength of the emission spectrum of the light-emitting device is 750 nm or more and 900 nm or less; the HOMO level of the host material is higher than the HOMO level of the light-emitting organic compound by 0.4 eV or more; A light-emitting device, wherein the difference between the HOMO and LUMO levels of the host material is smaller than the difference between the HOMO and LUMO levels of the light-emitting organic compound.

5. In claim 4, A light-emitting device, wherein the difference between the HOMO level and the LUMO level of the host material is 1.35 eV or more and 2.25 eV or less.

6. a light-emitting device having a light-emitting layer, the light-emitting layer comprises a light-emitting organic compound and a host material; the maximum peak wavelength of the emission spectrum of the light-emitting device is 750 nm or more and 900 nm or less; the host material comprises a first organic compound and a second organic compound; the first organic compound and the second organic compound are a combination that forms an exciplex, the HOMO level of the first organic compound is higher than the HOMO level of the light-emitting organic compound by 0.4 eV or more; a HOMO level of the first organic compound is higher than a HOMO level of the second organic compound; a difference between a HOMO level of the first organic compound and a LUMO level of the second organic compound is smaller than a difference between a HOMO level and a LUMO level of the light-emitting organic compound.

7. In claim 6, A light-emitting device, wherein a difference between a HOMO level of the first organic compound and a LUMO level of the second organic compound is 1.35 eV or more and 2.25 eV or less.

8. In any one of claims 1 to 7, The rising wavelength on the short wavelength side of the maximum peak in the emission spectrum is 650 nm or more. Light emitting device.

9. In any one of claims 1 to 8, A light-emitting device, wherein the light-emitting organic compound has an emission spectrum in a solution having a rising wavelength on the short wavelength side of a maximum peak of 650 nm or more.

10. In any one of claims 1 to 9, A light emitting device having an external quantum efficiency of 1% or greater.

11. In any one of claims 1 to 10, A light-emitting device, wherein the luminescent organic compound is an organometallic complex having a metal-carbon bond.

12. In claim 11, The organometallic complex has 2 to 5 condensed heteroaromatic rings, The fused heteroaromatic ring is coordinated to the metal.

13. In any one of claims 1 to 12, A light-emitting device, wherein the light-emitting organic compound is a cyclometal complex.

14. A light emitting device according to any one of claims 1 to 13, A light emitting device comprising: a transistor and / or a substrate.

15. A light emitting device according to claim 14; A light emitting module having a connector and / or an integrated circuit.

16. A light emitting module according to claim 15; An electronic device having at least one of an antenna, a battery, a housing, a camera, a speaker, a microphone, and an operation button.

17. A light emitting device according to claim 14; A lighting device having at least one of a housing, a cover, and a support base.

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