Light-emitting apparatus

Abstract

To provide a light-emitting device emitting near-infrared light, in which it is difficult to recognize visible light.SOLUTION: A light-emitting device includes a light-emitting organic compound and a host material in a light-emitting layer. The maximum peak wavelength of the emission spectrum of the light-emitting device is 750 nm or more and 900 nm or less. In the light-emitting device, a luminance A and a radiation luminance B satisfy 0≤A / B≤1.SELECTED DRAWING: Figure 1

Description

Technical Field

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

[0002] Note that one aspect of the present invention is not limited to the above technical field. Examples of the technical field of one aspect of the present invention include semiconductor devices, display devices, light-emitting devices, power storage devices, storage devices, electronic devices, lighting devices, input devices (for example, touch sensors, etc.), input / output devices (for example, touch panels, etc.), their driving methods, or their manufacturing methods.

Background Art

[0003] Research and development of light-emitting devices (also referred to as organic EL devices or organic EL elements) using the organic electroluminescence (EL) phenomenon have been actively conducted. The basic configuration of an organic EL device is one in which a layer containing a light-emitting organic compound (hereinafter also referred to as a light-emitting layer) is sandwiched between a pair of electrodes. By applying a voltage to this organic EL device, light emission from the light-emitting organic compound can be obtained.

[0004] Examples of the light-emitting organic compound include compounds that can convert the triplet excited state into light emission (also referred to as 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] In addition, image sensors are used in various applications such as personal authentication, defect analysis, medical diagnosis, and security-related applications. The wavelength of the light source used in an image sensor is properly selected according to the application. In an image sensor, for example, light of various wavelengths such as short-wavelength light such as visible light and X-rays, and long-wavelength light such as near-infrared light are used.

[0006] In addition to display devices, the application of the light-emitting device as a light source for the above-described image sensor has also been studied.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] In one aspect of the present invention, one of the problems 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. In one aspect of the present invention, one of the problems is to increase the luminous efficiency of a light-emitting device that emits near-infrared light. In one aspect of the present invention, one of the problems is to increase the reliability of a light-emitting device that emits near-infrared light.

[0009] Note that the description of these problems does not prevent the existence of other problems. One aspect of the present invention does not necessarily need to solve all of these problems. It is possible to extract other problems from the description of the specification, drawings, and claims.

Means for Solving the Problems

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

[0011] One aspect of the present invention is a light-emitting device having a light-emitting organic compound and a host material in a light-emitting layer, wherein the maximum peak wavelength of the emission spectrum is 750 nm or more and 900 nm or less, and the luminance A [cd / m 2 , and the radiant luminance B [W / sr / m 2 satisfy 0 < A / B ≦ 1 [cd·sr / W].

[0012] The difference between the HOMO level and the LUMO level in 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 luminescent 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 aspect of the present invention is a light-emitting device having a luminescent organic compound and a host material in a light-emitting layer, wherein the maximum peak wavelength of the emission spectrum is 750 nm or more and 900 nm or less, the HOMO level of the host material is 0.4 eV or more higher than the HOMO level of the luminescent organic compound, and the difference between the HOMO level and the LUMO level of the host material is smaller than the difference between the HOMO level and the LUMO level of the luminescent organic compound. The difference between the HOMO level and the LUMO level in the host material is preferably 1.35 eV or more and 2.25 eV or less.

[0015] One aspect of the present invention is a light-emitting device having a light-emitting organic compound and a host material in a light-emitting layer, wherein the maximum peak wavelength of the emission spectrum is 750 nm or more and 900 nm or less, the host material has a first organic compound and a second organic compound, the HOMO level of the first organic compound is 0.4 eV or more higher than the HOMO level of the light-emitting organic compound, the HOMO level of the first organic compound is higher than the HOMO level of the second organic compound, and the difference between the HOMO level of the first organic compound and the LUMO level of the second organic compound is smaller than the difference between the HOMO level and the LUMO level of the light-emitting organic compound. It is preferable that the first organic compound and the second organic compound are 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.

[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 rising wavelength on the short-wavelength side of the maximum peak in the PL spectrum in solution of 650 nm or more.

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

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

[0020] The organometallic complex preferably has a condensed heteroaromatic ring of 2 to 5 rings. The condensed heteroaromatic ring is preferably coordinated to the metal.

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

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

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

[0024] One aspect of the present invention is an electronic device having 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 aspect of the present invention is a lighting device having the above-described light-emitting device and at least one of a housing, a cover, and a support base.

Advantages of the Invention

[0026] According to one aspect of the present invention, it is possible to provide a light-emitting device that emits near-infrared light and in which visible light emission is difficult to be visually recognized. According to one aspect of the present invention, it is possible to improve the luminous efficiency of a light-emitting device that emits near-infrared light. According to one aspect of the present invention, it is possible to improve the reliability of a light-emitting device that emits near-infrared light.

[0027] Note that the description of these effects does not prevent the existence of other effects. One aspect of the present invention does not necessarily have all of these effects. It is possible to extract other effects from the description of the specification, drawings, and claims.

Brief Description of the Drawings

[0028]

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Mode for Carrying Out the Invention

[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 those skilled in the art can easily understand that the form and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments shown below.

[0030] In the configuration of the invention described below, the same reference numerals are commonly used between different drawings for the same part or parts having the same or similar functions, and the repeated description thereof is omitted. Further, when referring to similar functions, the hatching patterns may be the same, and in some cases, no reference numerals may be attached.

[0031] In addition, the positions, sizes, ranges, etc. of each configuration shown in the drawings may not represent the actual positions, sizes, ranges, etc. for the sake of easy understanding. Therefore, the disclosed invention is not necessarily limited to the positions, sizes, ranges, etc. disclosed in the drawings.

[0032] Note that the terms "film" and "layer" can be interchanged with each other in some cases or according to the 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 according to an aspect of the present invention will be described with reference to FIG. 1.

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

[0035] In a light-emitting device according to an aspect 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 a light-emitting device according to an aspect of the present invention, the luminance A [cd / m 2 , and the radiance B [W / sr / m 2 preferably satisfy 0 ≦ A / B ≦ 1 [cd·sr / W]. Or, the luminance A [cd / m2 and the radiance B [W / sr / m 2 preferably satisfies 0 < A / B ≤ 1 [cd·sr / W].

[0037] By satisfying the above equations for luminance and radiance, it is possible to realize a light-emitting device that makes the visible light emission difficult to be visually recognized and efficiently emits near-infrared light.

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

[0039] Examples of light having a wavelength with low visual sensitivity include ultraviolet light to blue light, and red light to near-infrared light. For example, if the light emission of the host material is such light, even when the light-emitting device exhibits light emission derived from the host material, the visible light emission becomes difficult to be visually recognized. Specifically, in the light-emitting device according to one aspect of the present invention, it can also be said that 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 preferably 800 nm or less.

[0040] Here, in the case where the guest material is a substance that emits phosphorescence (phosphorescent material), the absorption band considered to most strongly contribute to the 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 (low energy side). From this, it is preferably that the emission spectrum (fluorescence spectrum and phosphorescence spectrum) of the host material largely overlaps with the absorption band on the longest wavelength side (low energy side) of the absorption spectrum of the phosphorescent material. Thereby, the transfer of excitation energy from the host material to the guest material is smoothly performed. And by converting the excitation energy of the host material into the excitation energy of the guest material, the guest material emits light efficiently.

[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 with a long wavelength, the emission of visible light (derived from the host material) is difficult to be visually recognized, and a light-emitting device that efficiently emits near-infrared light can be realized. In particular, when the emission of the host material is red light to near-infrared light, the visual sensitivity of the emission derived from the host material can be lowered, and the transfer of excitation energy from the host material to the guest material occurs efficiently, which is preferable.

[0042] The HOMO level of the host material is preferably 0.4 eV or more higher than the HOMO level of the guest material. Since the HOMO level of the host material being sufficiently higher than the HOMO level of the guest material can reduce the band gap of the host material, the emission can be made to have a long wavelength. Thereby, the visual sensitivity of the emission of the host material can be lowered. Also, 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] Note that the LUMO level and HOMO level of the 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. Even when the difference between the HOMO level and the LUMO level of the host material is small, the emission of the host material can be made to have a long wavelength. Specifically, the difference between the HOMO level and the LUMO level in the host material 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 is preferably 1.90 eV or less.

[0045] Here, when a phosphorescent material is used as the guest material, if the T1 level (the energy level of the lowest triplet excited state) of the host material is higher than that 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 (the energy level of the lowest singlet excited state) of the host material is higher than each of the T1 level of the host material and the T1 level of the guest material. In order to make the light emission of the host material be 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. That is, it is preferable that the difference between the S1 level and the T1 level of the host material is small. Since a thermally activated delayed fluorescence (TADF) material has a small difference between the S1 level and the T1 level, it can be suitably used as a host material.

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

[0047] An exciplex formed by two kinds of substances in an excited state has a function as a TADF material in which the difference between the S1 level and the T1 level is extremely small and the triplet excitation energy can be converted into singlet excitation energy.

[0048] When the host material has a first organic compound and a second organic compound, light emission derived from the exciplex formed by the first organic compound and the second organic compound is confirmed from the light-emitting device of one aspect of the present invention. Therefore, in order to make the light emission of the exciplex difficult to be visually recognized, it is preferable that the light emission of the exciplex is light with low visibility.

[0049] Here, consider the case where the energy level heights are such that the HOMO level of the second organic compound < the HOMO level of the first organic compound < the LUMO level of the second organic compound < the LUMO level of the first organic compound. At this time, in the exciplex formed by the two organic compounds, the LUMO level is derived from the second organic compound, and the HOMO level is derived from the first organic compound.

[0050] Therefore, it is preferable that the HOMO level of the first organic compound is 0.4 eV or more higher than the HOMO level of the guest material. Since 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 longer wavelength. Thereby, the visibility of the exciplex can be lowered. Also, efficient transfer of excitation energy from the exciplex to the guest material can occur, and a light-emitting device that efficiently emits near-infrared light can be realized.

[0051] Also, it is preferable that the difference between the HOMO level of the first organic compound and the LUMO level of the second organic compound is smaller than the difference between the HOMO level and the LUMO level of the guest material. Even when the difference between the HOMO level of the first organic compound and the LUMO level of the second organic compound is small, the emission of the exciplex can be made to have a longer wavelength. 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 also preferably 1.90 eV or less.

[0052] Also, it is preferable that the guest material has a low emission intensity in the visible light region. For example, thus, in the light-emitting device according to one aspect 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 for obtaining the rise wavelength in this specification and the like will be described. First, from the points on the short-wavelength side of the emission spectrum on a linear scale, tangents are drawn at each point on the curve up to the maximum point on the short-wavelength side among the maximum points of the spectrum. As the curve rises (the value on the vertical axis increases), the slope of this tangent increases. The wavelength at which the tangent drawn at the point where the slope takes the maximum value on the shortest wavelength side intersects the origin is defined as the rise wavelength. Note that the maximum points at which the value on the vertical axis is 10% or less of the maximum peak are excluded from the maximum point on the shortest wavelength side described above.

[0054] In addition, the luminescent organic compound (guest material) preferably has a rise wavelength on the short-wavelength side of the maximum peak in the photoluminescence (PL) spectrum in solution of 650 nm or more.

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

[0056] In the light-emitting device according to one aspect of the present invention, since the emission intensity of the host material or the exciplex is sufficiently low, 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. Further, 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, for example, the external quantum efficiency may be calculated using data in a predetermined wavelength range. Specifically, the external quantum efficiency may be calculated from data in the range of 600 nm or more and 1030 nm or less in wavelength.

[0057] Alternatively, waveform separation of the emission spectrum may be performed to distinguish the emission from the guest material from the emission from the host material or the exciplex, and then the external quantum efficiency may be determined. At this time, the external quantum efficiency calculated from the emission of the guest material in the light-emitting device according to one aspect of the present invention is preferably 1% or more. Or the external quantum efficiency calculated from the near-infrared emission in the light-emitting device according to one aspect of the present invention is preferably 1% or more.

[0058] A luminescent organic compound is preferable because it can enhance the luminous efficiency in a light-emitting device when emitting phosphorescence. In particular, the luminescent organic compound is preferably an organometallic complex having a metal-carbon bond. Among them, the luminescent organic compound is more preferably a cyclometalated complex. Further, the luminescent organic compound is preferably an orthometalated complex. Since these organic compounds are likely to emit phosphorescence, the luminous efficiency in a light-emitting device can be enhanced. Therefore, the light-emitting device according to one aspect of the present invention preferably emits phosphorescence.

[0059] Furthermore, an organometallic complex having a metal-carbon bond is suitable as a luminescent organic compound because it has higher luminous efficiency and higher chemical stability compared to porphyrin-based compounds and the like.

[0060] In addition, when a luminescent organic compound is used as a guest material and another organic compound is used as a host material in a light-emitting layer, if a large valley occurs in the absorption spectrum of the luminescent organic compound (a portion with low intensity occurs), depending on the value of the excitation energy of the host material, the transfer of excitation energy from the host material to the guest material does not occur smoothly, 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. Therefore, it is difficult for a large valley to occur in the absorption spectrum. Therefore, the range of values of the excitation energy of the material that can be used as the host material can be widened, and the range of selection of the host material can be widened.

[0061] In addition, the luminescent organic compound is preferably an iridium complex. For example, the luminescent organic compound is preferably a cyclometalated complex using iridium as the central metal. Since the iridium complex has higher chemical stability than a platinum complex or the like, the reliability of the light-emitting device can be enhanced by using an iridium complex as the luminescent organic compound. From the viewpoint of such stability, a cyclometalated complex of iridium is preferred, and an orthometalated complex of iridium is more preferred.

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

[0063] The light-emitting device according to one embodiment of the present invention can be formed in a film shape and is easy to be made into a large area, so it can be used as a surface light source that emits near-infrared light.

[0064] The light-emitting device according to one aspect of the present invention has light emission of visible light that is difficult to be visually recognized and can efficiently emit near-infrared light. 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, it is possible to suppress the visible light emitted from the light-emitting device from becoming noise in authentication, analysis, diagnosis, etc. using near-infrared light. Thereby, the accuracy of authentication, analysis, diagnosis, etc. can be improved. Further, in electronic devices such as security-related and military applications, imaging using near-infrared light can be performed without being noticed by people around.

[0065] [Configuration Example of Light-Emitting Device] ≪Basic Structure of Light-Emitting Device≫ Figs. 1A to 1C show an example of a light-emitting device having an EL layer between a pair of electrodes.

[0066] The light-emitting device shown in Fig. 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 a plurality of EL layers between a pair of electrodes. Fig. 1B shows a tandem-structured light-emitting device having two EL layers (EL layer 103a and EL layer 103b) between a pair of electrodes and having a charge generation layer 104 between the two EL layers. The tandem-structured light-emitting device 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 layer 103a and the EL layer 103b and injecting holes into the other when a voltage is applied to the first electrode 101 and the second electrode 102. Therefore, in Fig. 1B, when a voltage is applied so that the potential of the first electrode 101 is higher than that of 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] Note that, from the viewpoint of light extraction efficiency, the charge generation layer 104 preferably transmits near-infrared light (specifically, the transmittance of near-infrared light of the charge generation layer 104 is 40% or more). Further, the charge generation layer 104 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 the stacked structure of the EL layer 103. In the present embodiment, the case where the first electrode 101 functions as an anode and the second electrode 102 functions as a cathode will be described as an example. 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 sequentially stacked 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 stacked structure. Note that, even in the case of having a plurality of EL layers as in the tandem structure shown in FIG. 1B, the same stacked structure as the EL layer 103 shown in FIG. 1C can be applied to each EL layer. Further, when the first electrode 101 is a cathode and the second electrode 102 is an anode, the stacking order is reversed.

[0071] The light-emitting layer 113 appropriately combines a light-emitting substance and a plurality of substances, and can be configured to obtain fluorescence emission or phosphorescence emission of a desired wavelength. The EL layer 103a and the EL layer 103b shown in FIG. 1B may be configured to emit different wavelengths.

[0072] In the light-emitting device according to one aspect of the present invention, the light obtained in the EL layer may be resonated between a pair of electrodes to enhance the obtained light. For example, in FIG. 1C, by using the first electrode 101 as a reflective electrode (an electrode having reflectivity with respect to near-infrared light) and the second electrode 102 as a semi-transmissive / semi-reflective electrode (an electrode having transmissivity and reflectivity with respect to near-infrared light), a microcavity structure is formed, and the light obtained 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 having reflectivity to near-infrared light and a conductive film having translucency to near-infrared light, optical adjustment can be performed by controlling the film thickness of the translucent conductive film. Specifically, it is preferable to adjust so that the electrode distance between the first electrode 101 and the second electrode 102 is in the vicinity of mλ / 2 (where m is a natural number) with respect to the wavelength λ of the light obtained from the light-emitting layer 113.

[0074] Further, in order to amplify the desired light (wavelength: λ) obtained from the light-emitting layer 113, the optical distance from the first electrode 101 to the region (light-emitting region) where the desired light of the light-emitting layer 113 is obtained and the optical distance from the second electrode 102 to the region (light-emitting region) where the desired light of the light-emitting layer 113 is obtained are each preferably adjusted to be in the vicinity of (2m'+1)λ / 4 (where m' is a natural number). Here, the light-emitting region refers to the recombination region of holes and electrons in the light-emitting layer 113.

[0075] By performing such optical adjustment, the spectrum of the light obtained from the light-emitting layer 113 can be narrowed, and light emission 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 region in the first electrode 101 to the reflection region in the second electrode 102. However, since it is difficult to strictly determine the reflection regions in the first electrode 101 and the second electrode 102, it is assumed that any positions of the first electrode 101 and the second electrode 102 are reflection regions, and it is considered that the above-described effects can be sufficiently obtained. Further, the optical distance between the first electrode 101 and the light-emitting layer from which desired light is obtained can be strictly said to be the optical distance between the reflection region in the first electrode 101 and the light-emitting region in the light-emitting layer from which desired light is obtained. However, since it is difficult to strictly determine the reflection region in the first electrode 101 and the light-emitting region in the light-emitting layer from which desired light is obtained, it is assumed that any position of the first electrode 101 is the reflection region and any position of the light-emitting layer from which desired light is obtained is the light-emitting region, and it is considered that the above-described effects can be sufficiently obtained.

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

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

[0079] ≪Specific Structure and Fabrication Method of Light-Emitting Device≫ Next, the specific structure and manufacturing method of the light-emitting device will be described. Here, a description will be given using a light-emitting device having the single structure shown in FIG. 1C.

[0080] <The first electrode and the second electrode> As materials for forming the first electrode 101 and the second electrode 102, the following materials can be appropriately combined and used as long as the functions of the above-described both electrodes can be satisfied. For example, metals, alloys, electroconductive compounds, and mixtures thereof can be appropriately used. Specifically, indium-tin oxide (also referred to as ITO), indium-silicon-tin oxide (also referred to as ITSO), indium-zinc oxide, indium-tungsten-zinc oxide can be mentioned. 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), neodymium (Nd), and alloys containing these appropriately combined can also be used. In addition, elements belonging to Group 1 or Group 2 of the periodic table not exemplified above (for example, lithium (Li), cesium (Cs), calcium (Ca), strontium (Sr)), rare earth metals such as europium (Eu), ytterbium (Yb), and alloys containing these appropriately combined, graphene, etc. can be used.

[0081] In the case of manufacturing a light-emitting device having a microcavity structure, the first electrode 101 is formed as a reflective electrode, and the second electrode 102 is formed as a semi-transmissive / semi-reflective electrode. Therefore, a desired conductive material can be used singly or in plurality and formed by a single layer or a laminate. Note that the second electrode 102 is formed by selecting a material in the same manner as above after the EL layer 103 is formed. In addition, a sputtering method or a vacuum evaporation method can be used for manufacturing these electrodes.

[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 by vacuum deposition on the first electrode 101.

[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, into the EL layer 103, and is a layer containing a material with high hole injection properties.

[0084] As materials with high hole injection properties, transition metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide, and phthalocyanine-based compounds such as phthalocyanine (abbreviation: H2Pc) and copper phthalocyanine (abbreviation: CuPc) can be used.

[0085] As materials with high hole injection properties, 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-(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), 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1) and other aromatic amine compounds can be used.

[0086] As materials with high hole injection properties, 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. can be used. Or, polymer compounds added with acids such as poly(3,4-ethylenedioxythiophene) / poly(styrenesulfonic acid) (abbreviation: PEDOT / PSS), polyaniline / poly(styrenesulfonic acid) (PAni / PSS), etc. can also be used.

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

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

[0089] As the acceptor material used for the hole injection layer 111, metal oxides belonging to Groups 4 to 8 in the periodic table can be used. Specifically, molybdenum oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, tungsten oxide, manganese oxide, and rhenium oxide can be mentioned. Among them, molybdenum oxide is particularly preferable because it is stable in the atmosphere, 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 those 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, a compound in which an electron-withdrawing group is bonded to a condensed aromatic ring having a plurality of heteroatoms like HAT-CN is thermally stable and preferable. Further, [3]radialene derivatives having an electron-withdrawing group (especially a halogen group such as a fluoro group or a cyano group) are preferable because they have very high electron-accepting properties. Specifically, α,α’,α’’-1,2,3-cyclopropanetriylidene tris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α’,α’’-1,2,3-cyclopropanetriylidene tris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], α,α’,α’’-1,2,3-cyclopropanetriylidene tris[2,3,4,5,6-pentafluorobenzeneacetonitrile], etc. can be mentioned.

[0090] As the hole transporting material used for the hole injection layer 111 and the hole transport layer 112, a substance having a hole mobility of 10 -6 cm 2 / Vs or more is preferable. Note that, as long as it is a substance having higher hole transportability than electrons, other substances can also be used.

[0091] As the hole transporting material, hole transporting materials with high hole transporting properties such as π-electron excess type heteroaromatic compounds (for example, carbazole derivatives, thiophene derivatives, furan derivatives, etc.) and aromatic amines (compounds having an aromatic amine skeleton) are preferable.

[0092] Examples of the carbazole derivative (compound having a carbazole skeleton) include bicarbozole derivatives (for example, 3,3'-bicarbozole derivatives), aromatic amines having a carbazolyl group, and the like.

[0093] Specific examples of the bicarbozole derivative (for example, 3,3'-bicarbozole derivative) 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'-bicarbozole (abbreviation: mBPCCBP), 9-(2-naphthyl)-9'-phenyl-9H,9'H-3,3'-bicarbozole (abbreviation: βNCCP), and the like.

[0094] Examples of the aromatic amine 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-fluorene-2-amine (abbreviation: PCBBiF), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 4-phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl)amine (abbreviation: PCA1BP), 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]fluorene-2-amine (abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluorene-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), 3,6-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), 4,4',4''-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA), etc. can be mentioned.,

[0095] As the carbazole derivative, in addition to the above, 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), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), etc. can be mentioned.

[0096] Examples of the thiophene derivative (a compound having a thiophene skeleton) and the furan derivative (a compound 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), 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and compounds having a furan skeleton such as 4,4’,4’’-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II), 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II).

[0097] As the aromatic amine, specifically, 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'-bifluorene-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)amino]-9H-fluoren-7-yl}phenylamine (abbreviation: DFLADFL), 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, etc. may be mentioned.

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

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

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

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

[0102] The light-emitting device according to one aspect of the present invention has 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 the light emitted by the light-emitting organic compound is greater than 750 nm and less than or equal to 900 nm.

[0103] As the light-emitting organic compound, for example, a 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 2 O,O’)iridium(III) (abbreviation: [Ir(dmdpbq)2(dpm)]), which is an organometallic complex shown as a guest material (phosphorescent material) in the examples described later, can be used.

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

[0105] The light-emitting layer 113 can have one or more light-emitting substances.

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

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

[0108] Examples of the luminescent substance that converts singlet excitation energy into light emission 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, naphthalene derivatives, and the like.

[0109] Examples of the luminescent substance that converts 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 the phosphorescent material include organometallic complexes having a 4H-triazole skeleton, 1H-triazole skeleton, imidazole skeleton, pyrimidine skeleton, pyrazine skeleton, or pyridine skeleton (especially iridium complexes), organometallic complexes having a phenylpyridine derivative having an electron-withdrawing group as a ligand (especially iridium complexes), platinum complexes, rare earth metal complexes, and the like.

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

[0112] When the luminescent substance used in the light-emitting layer 113 is a fluorescent material, it is preferable to use an organic compound having a large energy level of the singlet excited state and a small energy level of the triplet excited state as the organic compound used in combination with the luminescent substance.

[0113] When the luminescent substance is a fluorescent material, examples of the organic compound 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 the organic compound (host material) used in combination with the fluorescent material 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-carbazole-3-amine (abbreviation: PCAPA), N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazole-3-amine (abbreviation: PCAPBA), N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazole-3-amine (abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchrysene, N,N,N',N',N'',N'',N''',N''' -octaphenyldibenz[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), CzPA, 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenz[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-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, and the like.

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

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

[0117] With such a configuration, efficient light emission using ExTET (Exciplex-Triplet Energy Transfer), which is energy transfer from the exciplex to the light-emitting substance, can be obtained. As for the combination of a plurality of organic compounds, those that are likely to form an exciplex are preferable, and it is particularly preferable to combine a compound that easily receives holes (hole transporting material) and a compound that easily receives electrons (electron transporting material). Regarding specific examples of the hole transporting material and the electron transporting material, the materials shown in this embodiment can be used. With this configuration, high efficiency, low voltage, and long life of the light-emitting device can be realized simultaneously.

[0118] Examples of organic compounds that can be used in combination with a luminescent substance when the luminescent substance is a phosphorescent material 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, phenanthroline derivatives, and the like.

[0119] Among the above, specific examples of 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-transporting properties, are the same as the specific examples of the hole-transporting materials shown above.

[0120] Specific examples of zinc- or aluminum-based metal complexes, which are organic compounds with high electron-transporting properties, include 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), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), and the like, and metal complexes having a quinoline skeleton or a benzoquinoline skeleton.

[0121] In addition, metal complexes having oxazole-based or thiazole-based 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 oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, and phenanthroline derivatives, which are organic compounds with high electron-transporting properties, 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-(dibenzothiophen-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: 2mDBTPDBq-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,Examples include quinoxaline (abbreviation: 7mDBTPDBq-II), and 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzof[h]quinoxaline (abbreviation: 6mDBTPDBq-II).

[0123] Specific examples of heterocyclic compounds having a diazine skeleton, a heterocyclic compound having a triazine skeleton, and a heterocyclic compound having a pyridine skeleton, which are organic compounds with high electron transporting 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: 4,6mCzP2Pm), 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-9H-fluoren-2-yl)-1,1’-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn), 2-[(1,1’-biphenyl)-4-yl]-4-phenyl-6-[9,9’-spirobi(9H-fluorene)-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-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), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), and the like.

[0124] As organic compounds with high electron transport properties, high-molecular 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 function of converting triplet excitation energy into singlet excitation energy by reverse intersystem crossing because the difference between the S1 level and the T1 level is small. Therefore, upconversion (reverse intersystem crossing) of triplet excitation energy into singlet excitation energy is possible with a small amount of thermal energy, and a singlet excited state can be efficiently generated. In addition, triplet excitation energy can be converted into light emission. As conditions for efficiently obtaining thermally activated delayed fluorescence, the energy difference between the S1 level and the T1 level is 0 eV or more and 0.2 eV or less, preferably 0 eV or more and 0.1 eV or less. Also, the delayed fluorescence in a TADF material refers to light emission that has a spectrum similar to that of normal fluorescence but has a significantly longer lifetime. The lifetime is 10 -6 seconds or more, preferably 10 -3 seconds or more.

[0126] As an index for the T1 level, a phosphorescence spectrum observed at a low temperature (for example, from 77 K to 10 K) can be used. As a TADF material, when a tangent is drawn at the trailing edge on the short-wavelength side of its fluorescence spectrum, the energy of the wavelength of the extrapolated line is taken as the S1 level, and a tangent is drawn at the trailing edge on the short-wavelength side of the phosphorescence spectrum, and the energy of the wavelength of the extrapolated line is taken as the T1 level, it is preferable that the difference between the S1 level and the T1 level is 0.3 eV or less, and more preferably 0.2 eV or less.

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

[0128] Examples of the TADF material include fullerenes and their derivatives, acridine derivatives such as proflavine, eosin, etc. Further, metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd), etc. are also included. Examples of the 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)), octaethylporphyrin-platinum chloride complex (abbreviation: PtCl2OEP), etc.

[0129] In addition, heterocyclic compounds having a π-electron-excessive heteroaromatic ring and a π-electron-deficient heteroaromatic ring such as 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: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), 10-phenyl-10H,10’H-spiro[acridine-9,9’-anthracene]-10’-one (abbreviation: ACRSA), etc. can be used. Note that a substance in which a π-electron-excessive heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded is particularly preferable because both the donor property of the π-electron-excessive heteroaromatic ring and the acceptor property of the π-electron-deficient heteroaromatic ring are enhanced, and the energy difference between the singlet excited state and the triplet excited state becomes small.

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

[0131] Further, the above materials can be used to form the light-emitting layer 113 by combining with a low-molecular material or a high-molecular material. In addition, for film formation, known methods (such as vapor deposition method, coating method, printing method, etc.) can be appropriately used.

[0132] In the light-emitting device shown in FIG. 1C, an electron transport layer 114 is formed on the 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 to the light-emitting layer 113 by the electron injection layer 115. Note that the electron transport layer 114 is a layer containing an electron transport material. The electron transport material used for the electron transport layer 114 is preferably a substance having an electron mobility of 1×10 -6 cm 2 / Vs or more. Note that other substances can also be used as long as they have higher electron transport properties than holes.

[0134] Examples of the electron transport material include metal complexes having a quinoline skeleton, metal complexes having a benzoquinoline skeleton, metal complexes having an oxazole skeleton, metal complexes having a thiazole skeleton, etc. In addition, high electron transport materials 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 containing nitrogen-containing heteroaromatic compounds can be used.

[0135] As specific examples of the electron transport material, the materials shown 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 a vacuum evaporation method.

[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 includes lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), lithium oxide (LiO xAlkali metals, alkaline earth metals, or their compounds such as the like can be used. Also, rare earth metal compounds such as erbium fluoride (ErF3) can be used. Further, electrides may be used for the electron injection layer 115. Examples of electrides include substances obtained by adding electrons at high concentration to a mixed oxide of calcium and aluminum. In addition, the substances constituting the above-described electron transport layer 114 can also be used.

[0138] Further, a composite material including an electron transporting material and a donor material (electron donating material) may be used for the electron injection layer 115. Since such a composite material generates electrons in an organic compound by an electron donor, it is excellent in electron injection property and electron transport property. In this case, as the organic compound, a material excellent in transporting the generated electrons is preferable. Specifically, for example, the electron transporting materials (metal complexes, heteroaromatic compounds, etc.) used for the above-described electron transport layer 114 can be used. As the electron donor, any substance that exhibits electron donating property to the organic compound may be used. Specifically, alkali metals, alkaline earth metals, and rare earth metals are preferable, and examples include lithium, cesium, magnesium, calcium, erbium, ytterbium, etc. Also, alkali metal oxides and alkaline earth metal oxides are preferable, and examples include lithium oxide, calcium oxide, barium oxide, etc. Further, Lewis bases such as magnesium oxide can also be used. Also, organic compounds such as tetrathiafulvalene (abbreviation: TTF) can be used.

[0139] <Charge Generation Layer> In the light-emitting device shown in FIG. 1B, the charge generation layer 104 has a 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 generation layer 104 may be configured to include a hole transporting material and an acceptor material (electron accepting material), or may be configured to include an electron transporting material and a donor material. By forming the charge generation layer 104 having such a configuration, it is possible to suppress an increase in the driving voltage when the EL layer is laminated.

[0141] As the hole transporting material, acceptor material, electron transporting material, and donor material, the materials described above can be used respectively.

[0142] In addition, for the production of the light emitting device shown in this embodiment, a vacuum process such as a vapor deposition method or a solution process such as a spin coating method or an inkjet method can be used. When using the vapor deposition method, physical vapor deposition methods (PVD methods) such as sputtering method, ion plating method, ion beam vapor deposition method, molecular beam epitaxy method, vacuum evaporation method, etc., and chemical vapor deposition method (CVD method) etc. can be used. In particular, for the functional layers (hole injection layer, hole transport layer, light emitting layer, electron transport layer, electron injection layer) included in the EL layer and the charge generation layer, a vapor deposition method (such as vacuum evaporation method), 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 (stencil printing) method, offset (lithography) method, flexo (letterpress printing) method, gravure method, microcontact method, etc.) and other methods can be used to form them.

[0143] The materials of the functional layers and the charge generation layer constituting the EL layer 103 are not limited to the materials described above respectively. For example, as the material of the functional layer, a polymer compound (oligomer, dendrimer, polymer, etc.), a medium molecular compound (a compound in the intermediate region between low molecular and high molecular: molecular weight 400 to 4000), an inorganic compound (quantum dot material, etc.) etc. may be used. Note that as the quantum dot material, 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. can be used.

[0144] In a light-emitting device according to one aspect of the present invention, the light emission of the host material or the exciplex formed by the host material is hardly visible. Therefore, a light-emitting device that hardly emits visible light and efficiently emits near-infrared light can be realized.

[0145] In the light-emitting device according to one aspect of the present invention, the luminance A [cd / m 2 and the radiant luminance B [W / sr / m 2 satisfy 0 ≦ A / B ≦ 1 [cd·sr / W] (or 0 < A / B ≦ 1 [cd·sr / W]). Therefore, a light-emitting device that hardly emits visible light and efficiently emits near-infrared light can be realized.

[0146] This embodiment can be appropriately combined with other embodiments. Also, in this specification, when a plurality of configuration examples are shown in one embodiment, the configuration examples can be appropriately combined.

[0147] (Embodiment 2) In this embodiment, a light-emitting device according to one aspect of the present invention will be described with reference to FIGS. 2 and 3.

[0148] The light-emitting device of this embodiment has the light-emitting device shown in Embodiment 1. Therefore, a light-emitting device that emits near-infrared light and in which the emission of visible light is hardly visible can be realized.

[0149] [Configuration Example 1 of Light-Emitting Device] FIG. 2A shows a top view of the light-emitting device, and FIGS. 2B and 2C show cross-sectional views between the dashed-dotted lines X1 - Y1 and X2 - Y2 in FIG. 2A. The light-emitting device shown in FIGS. 2A to 2C can be used, for example, in an illumination device. The light-emitting device may be any of bottom emission, top emission, and dual emission.

[0150] The light-emitting device shown in Fig. 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. As the organic EL device 450, the light-emitting device shown in Embodiment 1 can be used.

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

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

[0153] For the substrates 490a and 490b, glass, quartz, ceramic, sapphire, an organic resin, or the like can be used respectively. Using a flexible material for the substrates 490a and 490b can enhance the flexibility of the light-emitting device.

[0154] On the light-emitting surface of the light-emitting device, a light extraction structure for enhancing the light extraction efficiency, an antistatic film for suppressing dust adhesion, a water-repellent film for making it difficult for dirt to adhere, a hard coat film for suppressing the generation of scratches during use, a shock absorption layer, etc. may be arranged.

[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 oxynitride, silicon nitride, and aluminum oxide.

[0156] As the adhesive layer 407, various curable adhesives such as photocurable adhesives such as ultraviolet curable type, reaction curable adhesives, thermosetting adhesives, and anaerobic adhesives can be used. Examples of these adhesives include epoxy resin, acrylic resin, silicone resin, phenol resin, polyimide resin, imide resin, PVC (polyvinyl chloride) resin, PVB (polyvinyl butyral) resin, EVA (ethylene vinyl acetate) resin, etc. In particular, materials with low moisture permeability such as epoxy resin are preferred. Also, a two-component mixed resin may be used. Further, an adhesive sheet or the like may be used.

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

[0158] The barrier layer 490c shown in Fig. 2C includes a substrate 420, an adhesive layer 422, and a highly barrier insulating layer 424.

[0159] In the light-emitting device shown in Fig. 2C, the organic EL device 450 is disposed between the highly barrier insulating layer 424 and the barrier layer 423. Therefore, even if a resin film or the like with relatively low waterproofness is used for the substrates 420 and 490b, it is possible to suppress the entry of impurities such as water into the organic EL device and the reduction of its lifespan.

[0160] For the substrates 420 and 490b, for example, polyester resins such as polyethylene terephthalate (PET) and 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. can be used. For the substrates 420 and 490b, glass with a thickness that has flexibility may also be used.

[0161] As the highly barrier insulating layer 424, it is preferable to use an inorganic insulating film. As the inorganic insulating film, for example, a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon nitride oxide film, an aluminum oxide film, an aluminum nitride film, etc. can be used. Further, a hafnium oxide film, a 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, a neodymium oxide film, etc. may also be used. Further, two or more of the above insulating films may be laminated and used.

[0162] The barrier layer 423 preferably has at least one layer of an inorganic film. For example, a single-layer structure of an inorganic film or a laminated structure of an inorganic film and an organic film can be applied to the barrier layer 423. As the inorganic film, the above inorganic insulating film is suitable. Examples of the laminated structure include a structure in which a silicon oxynitride film, a silicon oxide film, an organic film, a silicon oxide film, and a silicon nitride film are 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 can enter the organic EL device 450 can be preferably suppressed.

[0163] The highly barrier insulating layer 424 and the organic EL device 450 can be formed directly on the flexible substrate 420. In this case, the adhesive layer 422 is unnecessary. Further, the insulating layer 424 and the organic EL device 450 can be formed on a rigid substrate via a release layer and then transferred to the substrate 420. For example, after peeling the insulating layer 424 and the organic EL device 450 from the rigid substrate by applying heat, force, laser light, etc. to the release layer, the substrate 420 may be bonded using the adhesive layer 422 to be transferred to the substrate 420. As the release layer, for example, a laminated structure of an inorganic film including a tungsten film and a silicon oxide film, an organic resin film such as polyimide, or the like can be used. When using a rigid substrate, since the insulating layer 424 can be formed by applying a high temperature as compared with a resin substrate or the like, the insulating layer 424 can be made into a dense and extremely high-barrier insulating film.

[0164] [Configuration Example 2 of Light-Emitting Device] The light-emitting device according to one aspect of the present invention can be a passive matrix type or an active matrix type. The active matrix type light-emitting device will be described with reference to FIG. 3.

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

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

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

[0168] On the first substrate 301, a routing wire 307 is provided. The routing wire 307 is electrically connected to an FPC 308 which is an external input terminal. The FPC 308 transmits external signals (such as video signals, clock signals, start signals, reset signals, etc.) and potentials to the circuit unit 303, the circuit unit 304a, and the circuit unit 304b. Also, a printed wiring board (PWB) may be attached to the FPC 308. The configurations shown in FIGS. 3A and 3B can also be referred to as a light-emitting module having a light-emitting device (or a light-emitting apparatus) and an FPC.

[0169] The pixel section 302 includes a plurality of pixels each having an organic EL device 317, a transistor 311, and a transistor 312. As the organic EL device 317, the light-emitting device shown in Embodiment 1 can be used. 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 needed.

[0170] The circuit unit 303 includes a plurality of transistors including a transistor 309, a transistor 310, etc. The circuit unit 303 may be formed of a circuit including unipolar (either N-type or P-type only) transistors, or may be formed of a CMOS circuit including N-type transistors and P-type transistors. Alternatively, it may be configured to have a driving circuit externally.

[0171] The structure of the transistors included in the light-emitting apparatus of this embodiment is not particularly limited. For example, a planar transistor, a staggered transistor, an inverse staggered transistor, etc. can be used. Also, either a top gate type or a bottom gate type transistor structure may be used. Or, gates may be provided above and below the semiconductor layer in which the channel is formed.

[0172] The crystallinity of the semiconductor material used for the transistor is not particularly limited, and any of amorphous semiconductors, semiconductors having crystallinity (microcrystalline semiconductors, polycrystalline semiconductors, single-crystalline semiconductors, or semiconductors having crystal regions in part) may be used. Using a semiconductor having crystallinity is preferable because deterioration of transistor characteristics can be suppressed.

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

[0174] The semiconductor layer preferably has, for example, indium, M (where 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 denoted as IGZO) as the semiconductor layer.

[0176] When the semiconductor layer is an In-M-Zn oxide, the sputtering target used for forming the In-M-Zn oxide preferably has an atomic ratio of In that is equal to or more than the atomic ratio of M. Examples of the atomic ratio of the metal elements of such a sputtering target 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, etc.

[0177] The transistors included in circuit unit 303, circuit units 304a and 304b, and the transistors included in pixel unit 302 may have the same structure or different structures. The structures of the plurality of transistors included in circuit unit 303, circuit units 304a and 304b may all be the same, or there may be two or more types. Similarly, the structures of the plurality of transistors included in pixel unit 302 may all be the same, or there may be two or more types.

[0178] The end portion of the first electrode 313 is covered by an insulating layer 314. Note that as 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. It is preferable that the upper end portion or the lower end portion of the insulating layer 314 has a curved surface with curvature. Thereby, the covering property of the film formed on the upper layer of the insulating layer 314 can be made good.

[0179] An EL layer 315 is provided on the first electrode 313, and a second electrode 316 is provided on the EL layer 315. The EL layer 315 includes 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 a first substrate 301, a second substrate 306, and a sealing material 305. The space 318 surrounded by the first substrate 301, the second substrate 306, and the sealing material 305 may be filled with an inert gas (such as nitrogen or argon) or an organic substance (including the sealing material 305).

[0181] As the sealing material 305, an epoxy resin or glass frit can be used. Note that it is preferable to use a material that hardly permeates moisture and oxygen as the sealing material 305. When glass frit is used as the sealing material, the first substrate 301 and the second substrate 306 are preferably glass substrates from the viewpoint of adhesiveness.

[0182] This embodiment can be appropriately combined with other embodiments.

[0183] (Embodiment 3) In this embodiment, an electronic device that can use a light-emitting device according to one aspect of the present invention will be described with reference to FIG. 4.

[0184] A light-emitting device according to one aspect of the present invention emits near-infrared light, and the emission of visible light is hardly visible. 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, it is possible to suppress visible light emitted from the light-emitting device from becoming noise in authentication, analysis, diagnosis, etc. using near-infrared light. Thereby, the accuracy of authentication, analysis, diagnosis, etc. can be improved. Also, in electronic devices for security-related and military applications, imaging using near-infrared light can be performed without being noticed by people around.

[0185] FIG. 4A is a biometric authentication device for finger veins, and includes a housing 911, a light source 912, a detection stage 913, etc. By placing a finger on the detection stage 913, the shape of the vein can be imaged. A light source 912 that emits near-infrared light is installed above the detection stage 913, and an imaging device 914 is installed below. The detection stage 913 is made of a material that transmits near-infrared light, and the near-infrared light 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 configuration of the above device can also be used for a biometric authentication device for palm veins.

[0186] The light-emitting device according to one aspect of the present invention can be used as the light source 912. The light-emitting device according to one aspect of the present invention can be installed in a curved shape and can irradiate an object with light uniformly. In particular, it is preferably a light-emitting device that emits near-infrared light having the strongest peak intensity at a wavelength of 760 nm or more and 900 nm or less. The position of the vein can be detected by receiving the light transmitted through a finger or the palm of the hand and imaging it. This function can be used for biometric authentication. Also, by combining with the global shutter method, highly accurate sensing is possible even if the subject moves.

[0187] Also, the light source 912 can have a plurality of light-emitting parts like the light-emitting parts 915, 916, and 917 shown in FIG. 4B. Each of the light-emitting parts 915, 916, and 917 may have a different wavelength of light emission, and each can also irradiate light at a different timing. Therefore, different images can be continuously captured by changing the wavelength and angle of the irradiated light, so that a plurality of images can be used for authentication to achieve high security.

[0188] FIG. 4C is a biometric authentication device for the veins on the palm of the hand, and includes a housing 921, an operation button 922, a detection unit 923, a light source 924 that emits near-infrared light, etc. By holding the hand over the detection unit 923, the shape of the veins on the palm of the hand can be recognized. Also, a password number or the like can be input using the operation button. The light source 924 is arranged around the detection unit 923 to irradiate the object (hand). Then, the reflected light from the object is incident on the detection unit 923. The light-emitting device according to one aspect of the present invention can be used as the light source 924. An imaging device 925 is arranged directly below the detection unit 923, and an image of the object (the entire image of the hand) can be captured. An optical system may be provided between the detection unit 923 and the imaging device 925. The configuration of the above device can also be used for a biometric authentication device for the veins of a finger.

[0189] FIG. 4D is a non-destructive inspection device, which includes a housing 931, an operation panel 932, a conveying mechanism 933, a monitor 934, a detection unit 935, a light source 938 that emits near-infrared light, etc. The light-emitting device according to one aspect of the present invention can be used as the light source 938. The member to be inspected 936 is conveyed directly below the detection unit 935 by the conveying mechanism 933. The member to be inspected 936 is irradiated with near-infrared light from the light source 938, and the transmitted light is imaged by an imaging device 937 provided in the detection unit 935. The captured image is displayed on the monitor 934. Then, it is conveyed to the outlet of the housing 931, and defective products are sorted and collected. By imaging using near-infrared light, defective elements such as defects and foreign matters inside the non-inspected member can be detected non-destructively and at high speed.

[0190] FIG. 4E is a mobile phone, which includes a housing 981, a display unit 982, operation buttons 983, an external connection port 984, a speaker 985, a microphone 986, a first camera 987, a second camera 988, etc. The mobile phone is provided with a touch sensor on the display unit 982. The housing 981 and the display unit 982 are flexible. Any operation such as making a call or inputting characters can be performed by touching the display unit 982 with a finger or a stylus. 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 unit 982 shown in FIG. 4E may have the light-emitting device according to one aspect of the present invention.

[0191] This embodiment can be appropriately combined with other embodiments.

Example

[0192] In this example, a light-emitting device according to one aspect of the present invention is fabricated, and the evaluation results will be described.

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

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

[0195]

Table 1

[0196]

Chem.

[0197] ≪Fabrication of Device≫ As shown in Fig. 5, for Device 1 and Comparative Device 2 shown in this example, a first electrode 801 is formed on a substrate 800, and on the first electrode 801, as an EL layer 802, a hole injection layer 811, a hole transport layer 812, a light-emitting layer 813, an electron transport layer 814, and an electron injection layer 815 are sequentially laminated, and a second electrode 803 is laminated on the electron injection layer 815.

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

[0199] Here, as a pretreatment, the surface of the substrate was washed with water, baked at 200 °C for 1 hour, and then UV ozone treatment was performed for 370 seconds. Then, the substrate was introduced into a vacuum evaporation apparatus whose internal pressure was reduced to about 1 × 10 -4 Pa, and in the heating chamber of the vacuum evaporation apparatus, vacuum baking was performed at 170 °C for 30 minutes, 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 co-evaporating 1,3,5-tris(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II) and molybdenum oxide at a weight ratio of DBT3P-II:molybdenum oxide = 2:1 after reducing the pressure in the vacuum evaporation apparatus to about 1×10 -4 Pa. The film thickness of the hole injection layer 811 was 120 nm for Device 1 and 60 nm for 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 evaporation using N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluorene-2-amine (abbreviation: PCBBiF) to a film thickness of 20 nm.

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

[0203] For Device 1, as the host materials, 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, and as the guest material (phosphorescent material), 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 2 O,O')iridium(III) (abbreviation: [Ir(dmdpbq)2(dpm)]) was used, and co-evaporation was performed so that the weight ratio was 2,8mDBtP2Bfqn:m-MTDATA:[Ir(dmdpbq)2(dpm)] = 0.7:0.3:0.1. The film thickness of the light-emitting layer 813 was 40 nm.

[0204] In Comparative Device 2, as the host materials, 2-[3’-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenz[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II) and PCBBiF were used, and as the guest material (phosphorescent material), [Ir(dmdpbq)2(dpm)] was used. Co-evaporation was performed such that the weight ratio was 2mDBTBPDBq-II:PCBBiF:[Ir(dmdpbq)2(dpm)] = 0.7:0.3:0.1. The film 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] For the electron transport layer 814 of Device 1, sequential evaporation was performed such that the film thickness of 2,8mDBtP2Bfqn was 20 nm and the film thickness of 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBphen) was 70 nm.

[0207] For the electron transport layer 814 of Comparative Device 2, sequential evaporation was performed such that the film thickness of 2mDBTBPDBq-II was 20 nm and the film thickness of NBphen was 70 nm.

[0208] Next, an electron injection layer 815 was formed on the electron transport layer 814. The electron injection layer 815 was formed by evaporation using lithium fluoride (LiF) such that the film thickness was 1 nm.

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

[0210] Through the above steps, a light-emitting device was formed on the substrate 800 with an EL layer 802 sandwiched between a pair of electrodes. Note that the hole injection layer 811, hole transport layer 812, light-emitting layer 813, electron transport layer 814, and electron injection layer 815 described in the above steps are functional layers constituting the EL layer in one aspect of the present invention. Also, in the vapor deposition process in the above-described manufacturing method, a vapor deposition method using a resistance heating method was used for all.

[0211] Also, the light-emitting device fabricated as described above is sealed with another substrate (not shown). Note that when sealing with another substrate (not shown), in a glove box under a nitrogen atmosphere, another substrate (not shown) coated with an adhesive that cures by ultraviolet light is fixed on the substrate 800, and the substrates are adhered to each other so that the adhesive adheres to the periphery of the light-emitting device formed on the substrate 800. At the time of sealing, ultraviolet light of 365 nm was irradiated at 6 J / cm 2 to cure the adhesive, and the adhesive was stabilized by heat treatment at 80 °C for 1 hour.

[0212] ≪Operating Characteristics of Light-Emitting Device≫ The operating characteristics of Device 1 and Comparative Device 2 were measured. Note that the measurement was performed at room temperature (atmosphere maintained at 25 °C).

[0213] Figures 6 and 7 show the emission spectra when a current was passed through Device 1 and Comparative Device 2 at a current density of 50 mA / cm 2 . In the emission spectrum, the range from a wavelength of 380 nm to 749 nm is the measurement result using a spectro-radiance meter (SR-UL1R, manufactured by Topcon Corporation), and the range from a wavelength of 750 nm to 1030 nm is the measurement result using a near-infrared spectro-radiance meter (SR-NIR, manufactured by Topcon Corporation). Note that Figure 7 is different from Figure 6 in that the vertical axis is in logarithmic display. Further, Figure 7 also shows a sensitivity curve based on the scotopic relative sensitivity (CIE(1951) Scotopic V’(λ)).

[0214] Also, Table 2 shows the current of 2 mA (current density 50 mA / cm 2Shows the main initial characteristic values of device 1 and comparative device 2 in ( ). Note that the radiant flux and external quantum efficiency were calculated using the radiance, assuming that the light distribution characteristics of the light-emitting device were Lambertian.

[0215]

Table 2

[0216] Here, as shown in the reference example (Fig. 13), the PL spectrum of the dichloromethane solution of [Ir(dmdpbq)2(dpm)] showed a maximum peak at 807 nm (1.54 eV). Also, the rise on the short-wavelength side of the maximum peak 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] As shown in Fig. 6, the rise wavelength on the short-wavelength side of the maximum peak in the emission spectrum of device 1 was 754 nm. The rise 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 both device 1 and comparative device 2 had a sufficiently long rise wavelength on the short-wavelength side of the maximum peak.

[0219] As shown in Fig. 7, a relatively large emission peak (peak wavelength: 523 nm) was confirmed in the visible wavelength range in the emission spectrum of the comparison device 2. By comparing with the visual sensitivity curve, it was found that the light emitted by the comparison device 2 includes light in the wavelength range with high visual sensitivity among visible light. That is, the visible light emission of the comparison device 2 is easily visible. On the other hand, compared with the comparison device 2, the spectral radiant luminance of the device 1 in the visible wavelength range was low. Also, the maximum peak wavelength in the visible wavelength range of the emission spectrum of the device 1 was 638 nm, and the emission spectrum of the device 1 had an emission peak in the wavelength range with low visual sensitivity among visible light. From this, it was found that the device 1 emits visible light in the wavelength range with low visual sensitivity and has a low emission intensity in the visible wavelength range.

[0220] As shown in Table 2, the luminance / spectral radiant luminance (the value obtained by dividing the luminance value by the spectral radiant luminance value) of the device 1 was 0.05 cd·sr / W, and the luminance / spectral radiant luminance of the comparison device 2 was 2.1 cd·sr / W. From this, it was found that the visible light emission intensity of the device 1 is extremely low compared to the near-infrared light emission intensity. Therefore, it can be said that the device 1 is a light-emitting device that emits near-infrared light and is difficult to visually recognize the visible light emission. On the other hand, it can be said that the comparison device 2 has a high visible light emission intensity compared to the near-infrared light emission intensity and the visible light is easily visible.

[0221] As shown in Table 2, the external quantum efficiency of the device 1 was 2.5%. This can be said to be a high value as the external quantum efficiency of a light-emitting device that emits mainly near-infrared light with weak visible light emission intensity. The external quantum efficiency of the device 1 was calculated from the measurement results using a near-infrared spectro-radiometer (SR-NIR, manufactured by Topcon Corporation) in the range of wavelengths from 600 nm to 1030 nm.

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

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

[0224] Hybrid film B was formed by co-evaporating 2mDBTBPDBq-II and PCBBiF on a quartz substrate at a weight ratio of 2mDBTBPDBq-II:PCBBiF = 0.7:0.3 to achieve a film thickness of 50 nm. Here, 2mDBTBPDBq-II and PCBBiF are a combination that forms 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 materials 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] Using Table 3, the HOMO levels and LUMO levels of the two host materials used in Device 1 and Hybrid Film A will be described. It can be seen that the HOMO level of m-MTDATA is higher than the HOMO levels of [Ir(dmdpbq)2(dpm)] and 2,8mDBtP2Bfqn, respectively. 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). Also, 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 the LUMO level (-3.49 eV) of [Ir(dmdpbq)2(dpm)].

[0228] Next, using Table 3, the HOMO levels and LUMO levels of the two host materials used in Comparative Device 2 and Hybrid Film B will be described. It can be seen that the HOMO level of PCBBiF is higher than the HOMO levels of [Ir(dmdpbq)2(dpm)] and 2mDBTBPDBq-II, respectively. 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). Also, 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 the LUMO level (-3.49 eV) of [Ir(dmdpbq)2(dpm)].

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

[0230] Figures 8 and 9 show the PL spectrum of Hybrid Film A and the emission spectrum of Device 1 (similar to Figures 6 and 7). Note that Figure 9 is different from Figure 8 in that the vertical axis is in logarithmic scale.

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

[0232] As shown in Fig. 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 is due to the emission from the exciplex formed by these two materials.

[0233] As shown in Fig. 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 is due to the emission from the exciplex formed by these two materials.

[0234] Since the emission peak wavelength in the visible light region of the comparative device 2 is close to the maximum peak wavelength of the PL spectrum of the mixed film B, it was shown that the visible light emission confirmed in the comparative device 2 was due to the emission from 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 visual sensitivity. Therefore, the emission from the exciplex formed by the two host materials used in the mixed film A has low visual sensitivity. Thus, device 1 is a light-emitting device in which the emission from the exciplex is difficult to be visually recognized and the visible light emission is difficult to be visually recognized.

[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)]. Also, 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)]. Thereby, the emission wavelength of the exciplex formed by these two materials can be made longer, and the visual sensitivity of the emission from the exciplex can be lowered.

[0237] As described above, it was found from this example that a light-emitting device that emits near-infrared light and is less likely to visually recognize visible light emission can be fabricated by making the light emission of the exciplex formed by two host materials be light having a low visibility wavelength.

[0238] (Reference Example) The synthesis method of 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 2 O,O’)iridium(III) (abbreviation: [Ir(dmdpbq)2(dpm)]) will be specifically described. The structure of [Ir(dmdpbq)2(dpm)] is shown below.

[0239]

Chemical formula

[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 tube. After purging the inside with nitrogen, the mixture was stirred at 90 °C for 7.5 hours. After a predetermined time elapsed, the solvent was distilled off. Then, it was purified by silica gel column chromatography using toluene as the developing solvent to obtain the target product (yellow solid, yield 3.73 g, yield 79%). The synthesis scheme of Step 1 is shown in (a-1).

[0241]

Chemical formula

[0242] The nuclear magnetic resonance spectroscopy of the yellow solid obtained in Step 1 ( 1The analysis results by 1H-NMR are shown below. It was found from the analysis results that Hdmdpbq was obtained.

[0243] The 1H NMR data of the obtained substance are shown below. 1 1H NMR data are shown below. 1 1H-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(III) chloride hydrate (IrCl3·H2O) (manufactured by Furuya Metal Co., Ltd.) were placed in a eggplant-shaped flask equipped with a reflux tube, and the inside of the flask was replaced with argon. Then, microwave (2.45 GHz, 100 W) was irradiated for 2 hours to cause a reaction. After a predetermined time elapsed, the obtained residue was suction filtered and washed with methanol to obtain the target product (black solid, yield 1.76 g, yield 81%). The synthesis scheme of Step 2 is shown in (a-2).

[0245] [Chemical formula]

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

[0247]

Chemical formula

[0248] The analysis results of the dark green solid obtained in Step 3 by nuclear magnetic resonance spectroscopy ( 1 1H-NMR) are shown below. From the analysis results, it was found that [Ir(dmdpbq)2(dpm)] was obtained.

[0249] 1 1H-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 FIGS. 12 and 13.

[0251] For the measurement of the absorption spectrum, an ultraviolet-visible spectrophotometer (V550 type manufactured by JASCO Corporation) was used. A dichloromethane solution (0.010 mmol / L) was placed in a quartz cell, and the measurement was carried out at room temperature. For the measurement of the emission spectrum, a fluorescence photometer (FS920 manufactured by Hamamatsu Photonics K.K.) was used. A deoxygenated dichloromethane solution (0.010 mmol / L) was placed in a quartz cell under a nitrogen atmosphere, sealed, and the measurement was carried out at room temperature.

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

[0253] As shown in FIG. 13, [Ir(dmdpbq)2(dpm)] showed an emission peak at 807 nm (1.54 eV), and near-infrared emission was observed from the dichloromethane solution. Also, the rise 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 portion, 303: Circuit portion, 304a: Circuit portion, 304b: Circuit portion, 305: Sealant, 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 portion, 916: Light-emitting portion, 917: Light-emitting portion, 921: Housing, 922: Operation button, 923: Detection portion, 924: Light source, 925: Imaging device, 931: Housing, 932: Operation panel, 933: Conveyor mechanism, 934: Monitor, 935: Detection unit, 936: Member to be inspected, 937: Imaging device, 938: Light source, 981: Housing, 982: Display portion, 983: Operation button, 984: External connection port, 985: Speaker, 986: Microphone, 987: Camera, 988: Camera

Claims

1. The maximum peak wavelength of the emission spectrum is 750 nm or more and 900 nm or less, 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].

2. The light-emitting device includes a light-emitting organic compound, a first organic compound, and a second organic compound, The maximum peak wavelength of the emission spectrum 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 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, The light-emitting device, wherein the light-emitting organic compound has an emission spectrum in a solution in which the rising wavelength on the short wavelength side of the maximum peak is 650 nm or more.

4. In any one of claims 1 to 3, The light emitting device, wherein the rising wavelength on the short wavelength side of the maximum peak of the emission spectrum is 650 nm or more.

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