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

Abstract

A novel light-emitting device is provided. Additionally, a light-emitting device with good luminous efficiency is provided. Furthermore, a light-emitting device with good lifetime is provided. Additionally, a light-emitting device with low driving voltage is provided. A light-emitting device is provided, comprising an anode, a cathode, and an EL layer located between the anode and the cathode, wherein the EL layer comprises a light-emitting layer and an electron transport layer, the electron transport layer being located between the light-emitting layer and the cathode, the electron transport layer comprising an electron transport material, the electron transport material being an organic compound comprising a first backbone, a second backbone, and a third backbone, the first backbone having the function of transporting electrons, the second backbone having the function of receiving holes, and the third backbone comprising a single-ring π-electron-deficient heteroaromatic ring.

Description

[Technical Field] One embodiment of the present invention relates to a light-emitting device, a light-emitting element, a display module, a lighting module, a display device, a light-emitting device, an electronic device, and a lighting device. Note that one embodiment of the present invention is not limited to the above-described technical fields. The technical field of one embodiment of the invention disclosed in this specification relates to an object, method, or manufacturing method. Alternatively, one embodiment of the present invention relates to a process, machine, manufacture, or composition of matter. Therefore, more specifically, as examples of the technical field of one embodiment of the present invention disclosed in this specification, examples include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, lighting devices, energy storage devices, memory devices, imaging devices, their driving methods, or their manufacturing methods. [Previous Technology] In recent years, the practical application of light-emitting devices (organic EL elements) that utilize organic compounds and electroluminescence (EL) has been very active. In the basic structure of these light-emitting devices, an organic compound layer (EL layer) containing luminescent material is sandwiched between a pair of electrodes. By applying a voltage to the device and injecting carriers, light emission from the luminescent material can be obtained using the recombination energy of these carriers. Because these light-emitting devices are self-emissive, they offer advantages over liquid crystal displays (LCDs) in terms of higher visibility and the elimination of the need for a backlight when used in display pixels. Therefore, these devices are suitable for flat panel display components. Furthermore, displays using these devices can be manufactured to be thin and lightweight, which is a significant advantage. Moreover, extremely high-speed response is also a characteristic of these devices. Furthermore, because the light-emitting layers of these light-emitting devices can be continuously formed in two dimensions, surface light emission can be achieved. This characteristic is difficult to obtain in point light sources such as incandescent lamps or LEDs, or in line light sources such as fluorescent lamps, making these light-emitting devices highly valuable as surface light sources applicable to lighting and other applications. As mentioned above, although displays or lighting devices using light-emitting devices are suitable for a wide variety of electronic devices, research and development of light-emitting devices with better efficiency and lifespan are becoming increasingly active. Patent document 1 discloses a structure in which a hole transport material is disposed between a hole transport layer in contact with a hole injection layer and a light emission layer, and the HOMO energy level is between the HOMO energy level of the hole injection layer and the HOMO energy level of the host material. The characteristics of light-emitting devices have been significantly improved, but they are still insufficient to meet the high requirements for various characteristics such as efficiency and durability. [Patent Document 1] International Publication No. 2011 / 065136 [Summary of the Invention] Therefore, one objective of this invention is to provide a novel light-emitting device. Another objective of this invention is to provide a light-emitting device with good luminous efficiency. Another objective of this invention is to provide a light-emitting device with good lifetime. Another objective of this invention is to provide a light-emitting device with low driving voltage. A third objective of this invention is to provide a novel compound. Furthermore, another objective of this invention is to provide a highly reliable light-emitting device, electronic device, and display device. Additionally, another objective of this invention is to provide a low-power light-emitting device, electronic device, and display device. An embodiment of the present invention can achieve any of the above objectives. One embodiment of the present invention is a light-emitting device, comprising: an anode; a cathode; and an EL layer located between the anode and the cathode, wherein the EL layer includes a light-emitting layer and an electron transport layer, the electron transport layer being located between the light-emitting layer and the cathode, the electron transport layer including an electron transport material, the electron transport material being an organic compound comprising a first backbone, a second backbone and a third backbone, the first backbone having the function of transporting electrons, the second backbone having the function of receiving holes, and the third backbone comprising a single-ring π-electron-deficient heteroaromatic ring. Another embodiment of the present invention is a light-emitting device, comprising: an anode; a cathode; and an EL layer located between the anode and the cathode, wherein the EL layer comprises a light-emitting layer and an electron transport layer, the electron transport layer comprises an electron transport material, the electron transport material being an organic compound comprising a first skeleton, a second skeleton and a third skeleton, the first skeleton having the function of transporting electrons, the second skeleton having the function of receiving holes, the second skeleton comprising two or more fused aromatic hydrocarbon rings, and the third skeleton comprising a single-ring π-electron-deficient heteroaromatic ring. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the second framework comprises three or more fused aromatic hydrocarbon rings. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the second backbone is a tricyclic or tetracyclic fused aromatic hydrocarbon ring. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the number of carbon atoms forming the ring in the second framework is 14 or more. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the fused aromatic hydrocarbon ring is composed of only six-membered rings. In addition, another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the second skeleton includes any one of anthracene ring, phenanthrene ring, benzo[a]pyrene ring, tetraphenyl ring, α ring, β-triphenyl ring, and pyrene ring. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the second framework is an anthracene ring. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the electron transport layer further comprises a metal, a metal salt, a metal oxide, or an organometallic salt. Another embodiment of the present invention is a light-emitting device, comprising: an anode; a cathode; and an EL layer located between the anode and the cathode, wherein the EL layer includes a hole injection layer, a light-emitting layer, and an electron transport layer. The hole injection layer is located between the anode and the light-emitting layer, and the electron transport layer is located between the light-emitting layer and the cathode. The hole injection layer includes a hole transport material and an acceptor material. The electron transport layer includes an electron transport material and a metal, a metal salt, a metal oxide, or an organometallic salt. The hole transport material is an organic compound having hole transport properties and a HOMO energy level above -5.7 eV and below -5.4 eV. The acceptor material is a substance that exhibits electron accepting properties to the hole transport material. The electron transport material is an organic compound comprising a first framework, a second framework, and a third framework. The first framework has the function of transporting electrons, the second framework has the function of receiving holes, and the third framework comprises a single-ring π-electron-deficient heteroaromatic ring. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the second backbone is a fused aromatic hydrocarbon ring with two or more rings and less than four rings. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the second backbone is a tricyclic or tetracyclic fused aromatic hydrocarbon ring. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the second skeleton includes any one of a naphthalene ring, a fumonis ring, an anthracene ring, a phenanthrene ring, a tetraphenyl ring, a cyclopentadiene ring, a triphenyl ring, and a pyrene ring. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the number of carbon atoms forming the ring in the second framework is 14 or more. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the fused aromatic hydrocarbon ring is composed of only six-membered rings. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the second framework is an anthracene ring. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the acceptor material is an organic compound. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the metal, metal salt, metal oxide, or organometal salt is a metal complex containing an alkali metal or an alkaline earth metal. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the metal, metal salt, metal oxide, or organometal salt is a metal complex having ligands containing nitrogen and oxygen and alkali metals or alkaline earth metals. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the metal, metal salt, metal oxide, or organometal salt is a metal complex comprising a ligand having an 8-hydroxyquinoline structure and a monovalent metal ion. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the metal, metal salt, metal oxide, or organometal salt is a lithium complex comprising a ligand having an 8-hydroxyquinoline structure. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the first skeleton and the third skeleton in the electron transport material are bonded by the second skeleton. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the LUMO in the electron transport material is mainly distributed in the first framework. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the first framework comprises a nitrogen-containing fused aromatic ring or a triazine ring. In addition, another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the first framework contains two or more nitrogen atoms. In addition, another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the first framework is a framework comprising any one of a quinoline ring, a dibenzo[h,g]quinoline ring, a triazine ring, and a benzofuranopyrimidine ring. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the first framework is a framework including a quinoline ring. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the HOMO in the electron transport material is mainly distributed in the second framework. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the third framework comprises a heteroaromatic ring with a six-membered ring having nitrogen atoms. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the third backbone is any one of a pyridine ring, a pyrimidine ring, a pyrazine ring, and a triazine ring. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the third framework is bonded to the second framework such that nitrogen is located at the β-position of the carbon bonded to the second framework. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the third backbone is a pyridine ring substituted at the third position, a pyrimidine ring substituted at the fifth position, or a pyrazine ring. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the electron transport layer is in contact with the cathode. Another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the light-emitting layer has a host material and a light-emitting material, and the light-emitting material emits blue fluorescence. Another embodiment of the present invention is an electronic device, including: a light-emitting device described in any of the above; and a sensor, an operation button, a speaker, or a microphone. Another embodiment of the present invention is a light-emitting device, comprising: the light-emitting device described in any of the above; and a transistor or substrate. Another embodiment of the present invention is a lighting device, comprising: a light-emitting device described in any of the above; and a housing. Another embodiment of the present invention is a compound comprising a first backbone, a second backbone and a third backbone and used as an electron transport layer, wherein the first backbone has the function of transporting electrons, the second backbone has the function of receiving holes, and the third backbone comprises a monocyclic π-electron-deficient heteroaromatic ring. In this specification, a light-emitting device includes an image display device that uses a light-emitting element. Additionally, a light-emitting device sometimes includes modules such as those with connectors such as anisotropic conductive films or TCP (Tape Carrier Package) mounted on the light-emitting element; modules with printed circuit boards at the ends of the TCP; or modules where an IC (integrated circuit) is directly mounted on the light-emitting element using COG (Chip On Glass) bonding. Furthermore, lighting equipment sometimes includes a light-emitting device. One embodiment of the present invention provides a novel light-emitting device. Another embodiment of the present invention provides a light-emitting device with good lifespan. Furthermore, another embodiment of the present invention provides a light-emitting device with good luminous efficiency. Furthermore, another embodiment of the present invention can provide a highly reliable light-emitting device, electronic device, and display device. Additionally, another embodiment of the present invention can provide a low-power light-emitting device, electronic device, and display device. Note that the description of these effects does not preclude the existence of other effects. Furthermore, one embodiment of the present invention does not necessarily require all of the aforementioned effects. Additionally, effects other than these are obvious from the description in the specification, drawings, claims, etc., and can be derived from those descriptions.

Implementation Method

Claims

1. A light-emitting device, comprising: anode; cathode; and an EL layer located between the anode and the cathode, wherein the EL layer includes a light-emitting layer and an electron transport layer, the electron transport layer being located between the light-emitting layer and the cathode, the electron transport layer including an electron transport material, the electron transport material being an organic compound including a first skeleton, a second skeleton and a third skeleton, the first skeleton and the third skeleton being bonded by the second skeleton, the first skeleton being a quinoline ring, a dibenzo[h,g]quinoline ring, a benzofuran[2,3-b]pyrazine ring. The first skeleton is any one of the following: naphtho[1',2':4,5]furano[2,3-b]pyrazine ring, wherein when the first skeleton is naphtho[1',2':4,5]furano[2,3-b]pyrazine ring, the electron transport material is 9-{4-[10-(3-pyridyl)-9-anthrayl]phenyl}naphtho[1',2':4,5]furano[2,3-b]pyrazine, the second skeleton includes any one of anthracene ring, phenanthrene ring, benzo[a]pyridine ring, tetraphenyl ring, ring, cyclo[a]pyridine ring, and pyrene ring, and the third skeleton is any one of pyridine ring, pyrimidine ring, pyrazine ring, and triazine ring.

2. A light-emitting device, comprising: anode; cathode; and an EL layer located between the anode and the cathode, wherein the EL layer includes a light-emitting layer and an electron transport layer, the electron transport layer being located between the light-emitting layer and the cathode, the electron transport layer including an electron transport material, the electron transport material being an organic compound including a first backbone, a second backbone and a third backbone, the first backbone and the third backbone being bonded by the second backbone, the first backbone being a quinoline ring, a dibenzo[h,g]quinoline ring, a benzofuranopyrimidine ring and naphthalene. The first skeleton is a 9-{4-[10-(3-pyridyl)-9-anthrayl]phenyl}naphtho[1',2':4,5]furano[2,3-b]pyrazine ring, the second skeleton comprises an anthracene ring, and the third skeleton is a pyridine ring.

3. The light-emitting device of claim 1 or 2, wherein the electron transport layer further comprises a metal, a metal salt, a metal oxide, or an organometallic salt.

4. A light-emitting device, comprising: anode; cathode; The EL layer is located between the anode and the cathode, wherein the EL layer includes a hole injection layer, a light-emitting layer, and an electron transport layer. The hole injection layer is located between the anode and the light-emitting layer, and the electron transport layer is located between the light-emitting layer and the cathode. The hole injection layer includes a hole transport material and an acceptor material. The electron transport layer includes an electron transport material and a metal, metal salt, metal oxide, or organometallic salt. The hole transport material is an organic compound with hole transport properties and a HOMO energy level above -5.7 eV and below -5.4 eV. The acceptor material is an organic compound with a cyano or halogen group. The electron transport material is an organic compound including a first backbone, a second backbone, and a third backbone. The first backbone and the third backbone are connected by... The second skeletal bond is formed by the first skeletal bond being any one of a quinoline ring, a dibenzo[h,g]quinoline ring, a benzofuran[2,3-b]pyrazine ring, and a naphtho[1',2':4,5]furan[2,3-b]pyrazine ring. When the first skeletal bond is the naphtho[1',2':4,5]furan[2,3-b]pyrazine ring, the electron transport material is 9-{4-[10-(3-pyridyl)-9-anthrayl]phenyl}naphtho[1',2':4,5]furan[2,3-b]pyrazine. The second skeletal bond includes any one of anthracene ring, a phenanthrene ring, a benzo[2,3-b]furan ring, a tetraphenyl ring, a ring, a triphenyl ring, and a pyrene ring. The third skeletal bond is any one of a pyridine ring, a pyrimidine ring, a pyrazine ring, and a triazine ring.

5. The light-emitting device of claim 4, wherein the metal, the metal salt, the metal oxide or the organometal salt is a metal complex containing an alkali metal or an alkaline earth metal.

6. The light-emitting device of claim 4, wherein the metal, the metal salt, the metal oxide or the organometal salt is a metal complex having ligands containing nitrogen and oxygen and an alkali metal or alkaline earth metal.

7. The light-emitting device of claim 4, wherein the metal, the metal salt, the metal oxide, or the organometal salt is a metal complex comprising a monovalent metal ion and a ligand having an 8-hydroxyquinoline structure.

8. The light-emitting device of claim 4, wherein the metal, the metal salt, the metal oxide, or the organometal salt is a lithium complex comprising a ligand having an 8-hydroxyquinoline structure.

9. A light-emitting device according to any one of claims 1, 2 and 4, wherein the LUMO of the electron transport material is mainly distributed in the first skeleton.

10. A light-emitting device according to any one of claims 1, 2 and 4, wherein the HOMO of the electron transport material is mainly distributed in the second skeleton.

11. A light-emitting device as claimed in any of claims 1, 2 and 4, wherein the third framework is bonded to the second framework such that nitrogen in the third framework is located at the β-position of carbon bonded to the second framework.

12. The light-emitting device as claimed in claim 1 or 4, wherein the third backbone is a pyridine ring substituted at position 3.

13. A light-emitting device according to any one of claims 1, 2 and 4, wherein the electron transport layer is in contact with the cathode.

14. A light-emitting device according to any one of claims 1, 2 and 4, wherein the light-emitting layer comprises a host material and a light-emitting material, and the light-emitting material emits blue fluorescence.

15. A compound used in an electron transport layer, comprising: First skeleton; Second skeleton; And a third skeleton, wherein the first skeleton and the third skeleton are bonded by the second skeleton, the first skeleton being the skeleton of any one of a quinoline ring, a dibenzo[h,g]quinoline ring, a benzofuran[2,3-b]pyrazine ring, and a naphtho[1',2':4,5]furan[2,3-b]pyrazine ring, wherein when the first skeleton is the naphtho[1',2':4,5]furan[2,3-b]pyrazine ring, the compound used for the electron transport layer is 9-{4-[10-(3-pyridyl)-9-anthrayl]phenyl}naphtho[1',2':4,5]furan[2,3-b]pyrazine, the second skeleton comprising an anthracene ring, and the third skeleton being a pyridine ring.

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