Organic electroluminescent device and display panel

Abstract

The invention provides an organic electroluminescent device and a display panel, and relates to the technical field of display. According to the organic light-emitting device, through cooperation of a plurality of film layer materials, the light-emitting efficiency under low current can be effectively improved, and the quality of a display panel is improved.

Description

Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to an organic electroluminescent device and a display panel. Background Art

[0002] With the development of display technology, organic electroluminescent devices are increasingly widely used. The device efficiency of organic electroluminescent devices is not constant, but changes with the brightness of the device. Improving the device efficiency of organic electroluminescent devices at low brightness is of great significance for improving the display quality of display devices.

[0003] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0004] The purpose of the present disclosure is to overcome the above-mentioned deficiencies of the prior art, provide an organic electroluminescent device and a display panel, and improve the device efficiency of the organic electroluminescent device at low brightness.

[0005] According to one aspect of the present disclosure, an organic electroluminescent device is provided, the organic electroluminescent device comprising an anode, a light-emitting functional layer and a cathode which are sequentially stacked; the light-emitting functional layer comprises an organic light-emitting layer and a hole blocking layer stacked on the surface of the organic light-emitting layer; the organic light-emitting layer comprises a host material and a doping material, and the hole blocking layer comprises a hole blocking material;

[0006] wherein the HOMO energy level of the host material is at least 0.4 eV higher than the HOMO energy level of the hole blocking material;

[0007] The LUMO energy level of the host material is at least 0.1 eV lower than the LUMO energy level of the dopant material;

[0008] The LUMO energy level of the doping material is at least 0.3 eV lower than the LUMO energy level of the hole blocking material;

[0009] The optical band gap of the hole blocking material is at least 0.6 eV greater than the optical band gap of the host material;

[0010] The optical band gap of the host material is at least 0.3 eV greater than the optical band gap of the dopant material.

[0011] According to one embodiment of the present disclosure, the host material is selected from the compound represented by chemical formula (I), or a derivative of the compound represented by chemical formula (I);

[0012]

[0013] Wherein, in the compound represented by chemical formula (I), Ar1 and Ar2 are the same or different, and are independently selected from substituted or unsubstituted aryl groups having 6 to 40 carbon atoms, and substituted or unsubstituted heteroaryl groups having 12 to 20 carbon atoms; when Ar1 or Ar2 has a substituent, the substituent on Ar1 or Ar2 is independently selected from deuterium, an alkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 15 carbon atoms;

[0014] X is selected from sulfur or oxygen;

[0015] The derivative of the compound represented by chemical formula (I) is a compound formed by replacing at least one hydrogen of the compound represented by chemical formula (I), and each substituent is independently selected from deuterium, fluorine, cyano, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 15 carbon atoms, and a heteroaryl group having 12 to 20 carbon atoms.

[0016] According to one embodiment of the present disclosure, the hole blocking material is selected from the compound represented by chemical formula (II):

[0017]

[0018] Wherein, Ar3 and Ar4 are the same or different and are independently selected from an alkyl group having 1 to 40 carbon atoms and an aryl group having 6 to 60 carbon atoms; Ar3 and Ar4 may also be connected to each other to form a ring;

[0019] n is 1 or 2 or 3;

[0020] Z1, Z2, and Z3 are CH or nitrogen, and at least one of them is nitrogen.

[0021] According to one embodiment of the present disclosure, the light-emitting functional layer further includes a hole transport layer located between the organic light-emitting layer and the anode, and further includes an electron transport layer located between the hole blocking layer and the cathode;

[0022] The hole transport layer comprises a hole transport material, and the HOMO energy level of the hole transport material is not less than -5.5 eV; the electron transport layer comprises an electron transport material, and the LUMO energy level of the electron transport material is not less than -2.7 eV;

[0023] The ratio of the hole mobility of the hole transport material to the electron mobility of the electron transport material is not greater than 5.

[0024] According to one embodiment of the present disclosure, the hole transport material is selected from the compound represented by the following chemical formula (III):

[0025]

[0026]

[0027] Wherein, Ar5 and Ar6 are the same or different and are independently selected from Formula A-1, Formula A-2, and Formula A-3; and at least one of Ar5 and Ar6 is selected from one of Formula A-2 and Formula A-3;

[0028]

[0029] wherein Ar7 is selected from hydrogen, deuterium, phenyl, biphenyl;

[0030] Wherein, R1 and R2 are the same or different and are independently selected from substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, substituted or unsubstituted aryl groups having 6 to 13 carbon atoms, or R1 and R2 can be linked to form a ring through a single bond.

[0031] According to one embodiment of the present disclosure, the electron transport material is selected from the compound represented by the following chemical formula (IV):

[0032]

[0033] Wherein, Ar8, Ar9, Ar 10 ,Ar 11 are the same or different and each independently represents a substituted or unsubstituted aryl group of 6 to 30 carbon atoms, or a substituted or unsubstituted heteroaryl group of 5 to 30 carbon atoms;

[0034] When Ar8, Ar9, Ar 10 ,Ar 11 When there are substituents on the above, any two substituents are the same or different, and any one of the substituents is selected from protium, deuterium, tritium, cyano, fluorine atom, alkyl group of 1 to 20 carbon atoms, aryl group of 6 to 30 carbon atoms, heteroaryl group of 5 to 30 carbon atoms; wherein the heteroatom in the heteroaryl group is selected from one or more of oxygen atom, sulfur atom or nitrogen atom.

[0035] According to another aspect of the present disclosure, a display panel is provided, comprising a plurality of light-emitting elements; wherein at least one of the light-emitting elements is the above-mentioned organic electroluminescent device.

[0036] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0038] Figure 1 The figure is a schematic diagram of the structure of an organic electroluminescent device in one embodiment of the present disclosure. DETAILED DESCRIPTION

[0039] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in a variety of forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that the present disclosure will be comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar structures, and thus their detailed description will be omitted. In addition, the drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale.

[0040] Although relative terms such as "upper" and "lower" are used in this specification to describe the relative relationship of one component of the illustration to another component, these terms are used in this specification only for convenience, such as according to the orientation of the examples described in the drawings. It is understood that if the device of the illustration is turned upside down, the component described as "upper" will become the component "lower". When a structure is "on" other structures, it may mean that the structure is formed integrally on the other structure, or that the structure is "directly" disposed on the other structure, or that the structure is "indirectly" disposed on the other structure through another structure.

[0041] The terms "a", "an", "the", "said" and "at least one" are used to indicate the presence of one or more elements / components / etc.; the terms "including" and "having" are used to express an open-ended inclusive meaning and mean that additional elements / components / etc. may exist in addition to the listed elements / components / etc.; the terms "first", "second" and "third" etc. are used merely as labels and are not intended to limit the quantity of their objects.

[0042] In the present disclosure, the description "... independently selected from" should be understood in a broad sense, which can mean that in different groups, the specific options expressed by the same symbols do not affect each other, or in the same group, the specific options expressed by the same symbols do not affect each other. For example, " Wherein, each q' is independently 0, 1, 2 or 3, and each R" is independently selected from hydrogen, deuterium, fluorine, and chlorine. The meaning is: Formula Q-1 indicates that there are q' substituents R" on the benzene ring, and each R" can be the same or different, and the options of each R" do not affect each other; Formula Q-2 indicates that there are q' substituents R" on each benzene ring of biphenyl, and the number q' of R" substituents on the two benzene rings can be the same or different, and each R" can be the same or different, and the options of each R" do not affect each other.

[0043] In this disclosure, an unfixed bond refers to a single bond extending from the ring system. It means that one end of the linker can be connected to any feasible position in the ring system through which the linker passes, and the other end is connected to the rest of the compound molecule.

[0044] For example, as shown in the following formula (f), the naphthyl group represented by formula (f) is connected to other positions of the molecule through two non-positional connecting bonds that penetrate the bicyclic ring, and its meaning includes any possible connection method shown in formulas (f-1) to (f-10).

[0045]

[0046] For another example, as shown in the following formula (X'), the phenanthryl group represented by formula (X') is connected to other positions of the molecule through a non-positional connecting bond extending from the middle of one side of the benzene ring, and its meaning includes any possible connection method shown in formulas (X'-1) to (X'-4).

[0047]

[0048] The non-positional substituent in the present disclosure refers to a substituent connected by a single bond extending from the center of the ring system, which means that the substituent can be connected to any possible position in the ring system. For example, as shown in the following formula (Y), the substituent R' represented by formula (Y) is connected to the quinoline ring through a non-positional connecting bond, and the meaning represented by it includes any possible connection mode shown in formula (Y-1) to formula (Y-7).

[0049]

[0050] In the present disclosure, in a substituted or unsubstituted G group with M carbon atoms, the carbon number of the G group is M, and the carbon number M does not take into account the carbon number of the substituent; for example, the total number of carbon atoms in the G group with M carbon atoms substituted by methyl is M+1. Correspondingly, in a substituted or unsubstituted aryl group with M carbon atoms or a substituted or unsubstituted heteroaryl group with M carbon atoms, the carbon number M does not take into account the carbon number of the substituent, but only takes into account the carbon number of the aromatic ring or heteroaromatic ring. For example, An aromatic group having 6 carbon atoms substituted with a methyl group; It is an unsubstituted arylene group having 12 carbon atoms.

[0051] In the present disclosure, when no specific definition is otherwise provided, "hetero" means including at least one heteroatom such as B, N, O, S, Se, Si or P in one functional group and the remaining atoms are carbon, hydrogen and deuterium. The unsubstituted alkyl group may be a "saturated alkyl group" without any double bond or triple bond.

[0052] In the present disclosure, "alkyl" may include straight chain alkyl or branched chain alkyl. The alkyl may have 1 to 18 carbon atoms. In the present disclosure, a numerical range such as "1 to 18" refers to each integer in the given range; for example, "alkyl having 1 to 18 carbon atoms" refers to an alkyl having 1 carbon atom, 2 carbon atoms, 3 carbon atoms, 4 carbon atoms, 5 carbon atoms, 6 carbon atoms, 7 carbon atoms, 8 carbon atoms, 9 carbon atoms, 10 carbon atoms, 11 carbon atoms, 12 carbon atoms, 13 carbon atoms, 14 carbon atoms, 15 carbon atoms, 16 carbon atoms, 17 carbon atoms, 18 carbon atoms. In some examples, the alkyl may also be a small alkyl having 1 to 5 carbon atoms.

[0053] Optionally, the alkyl group is selected from alkyl groups having 1 to 5 carbon atoms, and specific examples include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl and pentyl.

[0054] In the present disclosure, a cycloalkyl group refers to a group derived from a saturated cyclic carbon chain structure. A cycloalkyl group may have 5 to 10 carbon atoms, and in the present disclosure, a numerical range such as "a cycloalkyl group having 5 to 10 carbon atoms" refers to each integer in a given range; for example, "a cycloalkyl group having 5 to 10 carbon atoms" refers to a cycloalkyl group having 5 carbon atoms, a cycloalkyl group having 6 carbon atoms, a cycloalkyl group having 7 carbon atoms, a cycloalkyl group having 8 carbon atoms, a cycloalkyl group having 9 carbon atoms, and a cycloalkyl group having 10 carbon atoms.

[0055] Alternatively, specific examples of cycloalkyl include, but are not limited to, cyclopentyl, cyclohexyl, adamantyl, norbornyl, and the like.

[0056] In the present disclosure, aryl refers to an optional functional group or substituent derived from an aromatic carbocyclic ring. Aryl can be a monocyclic aryl (e.g., phenyl) or a polycyclic aryl. In other words, aryl can be a monocyclic aryl, a condensed ring aryl, two or more monocyclic aryl groups connected by carbon-carbon bond conjugation, a monocyclic aryl and a condensed ring aryl connected by carbon-carbon bond conjugation, and two or more condensed ring aryl groups connected by carbon-carbon bond conjugation. That is, unless otherwise specified, two or more aromatic groups connected by carbon-carbon bond conjugation can also be regarded as aryl of the present disclosure. Among them, condensed ring aryl can, for example, include bicyclic condensed aryl (e.g., naphthyl), tricyclic condensed aryl (e.g., phenanthrenyl, fluorenyl, anthracenyl), etc. Aryl does not contain heteroatoms such as B, N, O, S, P, Se, and Si. For example, in the present disclosure, biphenyl, terphenyl, etc. are aryl. Examples of aryl groups may include, but are not limited to, phenyl, naphthyl, fluorenyl, anthracenyl, phenanthrenyl, biphenyl, terphenyl, quaterphenyl, pentphenyl, benzo[9,10]phenanthrenyl, pyrenyl, benzofluoranthenyl, In the present disclosure, biphenyl can be understood as an aryl group substituted with phenyl, or as an unsubstituted aryl group. In the present disclosure, the arylene group refers to a divalent group formed by further losing a hydrogen atom from an aryl group.

[0057] In the present disclosure, the substituted aryl group may be an aryl group in which one or more hydrogen atoms are substituted by a deuterium atom, an aryl group, a heteroaryl group, an alkyl group, a cycloalkyl group, an alkoxy group or other groups.

[0058] In the present disclosure, heteroaryl refers to a monovalent aromatic ring or a derivative thereof containing at least one heteroatom in the ring, and the heteroatom can be at least one of B, O, N, P, Si, Se and S. The heteroaryl can be a monocyclic heteroaryl or a polycyclic heteroaryl. In other words, the heteroaryl can be a single aromatic ring system or a plurality of aromatic ring systems conjugated by carbon-carbon bonds, and any aromatic ring system is an aromatic monocyclic ring or an aromatic condensed ring. For example, the heteroaryl can include thienyl, furanyl, pyrrolyl, imidazolyl, thiazolyl, oxazolyl, oxadiazolyl, triazolyl, pyridyl, bipyridyl, pyrimidyl, triazine, acridinyl, pyridazinyl, pyrazinyl, quinolyl, quinazolinyl, quinoxalinyl, phenoxazinyl, phthalazinyl, pyridopyrimidinyl, pyridopyrazinyl, pyrazinopyrazinyl, isoquinolyl, indolyl, carbazolyl, benzoxazolyl, benzimidazole The invention also includes benzothiazolyl, benzocarbazolyl, benzothienyl, dibenzothienyl, thienothiphenyl, benzofuranyl, phenanthroline, isoxazolyl, thiadiazolyl, benzothiazolyl, phenothiazinyl, silafluorenyl, dibenzofuranyl, and N-arylcarbazolyl (such as N-phenylcarbazolyl), N-heteroarylcarbazolyl (such as N-pyridylcarbazolyl), N-alkylcarbazolyl (such as N-methylcarbazolyl), etc., without limitation. Among them, thienyl, furanyl, phenanthroline, etc. are heteroaryl groups of a single aromatic ring system type, and N-arylcarbazolyl (such as N-phenylcarbazolyl) and N-heteroarylcarbazolyl are heteroaryl groups of a polycyclic system type connected by conjugation of carbon-carbon bonds.

[0059] In the present disclosure, the substituted heteroaryl group may be a heteroaryl group in which one or more hydrogen atoms are substituted by groups such as a deuterium atom, an aryl group, a heteroaryl group, an alkyl group, a cycloalkyl group, an alkoxy group, or the like.

[0060] For organic electroluminescent devices, as the current loaded on the device increases, the exciton density of the light-emitting layer increases, which will intensify the mutual quenching between excitons and excitons, causing efficiency roll-off; that is, as the brightness of the device increases, the efficiency of the device has been declining, which is called the roll-off phenomenon. For example, the commonly used green organic electroluminescent devices and red organic electroluminescent devices have this phenomenon. However, the inventors found that blue organic electroluminescent devices have different efficiency roll-off trends. From low brightness to high brightness, the efficiency first rises and then falls, that is, there is a negative efficiency roll-off at low brightness, which can be called the roll-on phenomenon. This may be because the current blue light system is a TTA luminescence mechanism (a triplet annihilation mechanism that generates a singlet exciton by colliding two triplet excitons), which requires the use of triplet excitons to generate singlet excitons and then radiate light; increasing the current, the carrier density is higher, and there are more triplet excitons that can participate in TTA, showing an increase in device efficiency; continuing to increase the current until the number of excitons reaches a certain threshold, the influence of mutual quenching between excitons is aggravated, showing a decrease in device efficiency.

[0061] Therefore, it is necessary to control the carrier transfer balance under low current and improve the carrier utilization rate. Unbalanced carrier transfer will cause the exciton recombination center to be close to the transport layer; if the energy levels of the light-emitting layer material and the transport layer material do not match, it will cause the light-emitting layer excitons to leak to the functional layer, resulting in a decrease in carrier utilization.

[0062] To this end, the present disclosure provides an organic electroluminescent device and a display panel using the organic electroluminescent device. The display panel includes at least one organic electroluminescent device provided by an embodiment of the present disclosure. Figure 1 The organic electroluminescent device comprises an anode, a light-emitting functional layer and a cathode which are stacked in sequence; the light-emitting functional layer comprises an organic light-emitting layer EML and a hole blocking layer HBL stacked on the surface of the organic light-emitting layer EML. The hole blocking layer HBL is located between the organic light-emitting layer EML and the cathode. The organic light-emitting layer EML comprises a host material and a doping material, and the hole blocking layer HBL comprises a hole blocking material.

[0063] Among them, the HOMO energy level of the main material is at least 0.4 eV higher than the HOMO energy level of the hole blocking material; the LUMO energy level of the main material is at least 0.1 eV lower than the LUMO energy level of the doping material; the LUMO energy level of the doping material is at least 0.3 eV lower than the LUMO energy level of the hole blocking material; the optical band gap of the hole blocking material is at least 0.3 eV larger than the optical band gap of the main material; the optical band gap of the main material is at least 0.3 eV larger than the optical band gap of the doping material.

[0064] In the embodiment of the present disclosure, the HOMO energy level of the hole blocking material is at least 0.4 eV deeper than the HOMO energy level of the main material, which makes it difficult for the holes injected into the organic light-emitting layer to be further injected into the hole blocking layer, and can effectively block the diffusion of holes to the hole blocking layer, which can improve the utilization rate of holes in the organic light-emitting layer. The LUMO energy level of the main material is at least 0.1 eV lower than the LUMO energy level of the doping material, which enables the electrons transmitted to the doping material to be efficiently transferred to the main material, thereby facilitating the formation of excitons on the main material, which can improve the utilization rate of carriers and the efficiency of exciton generation. The LUMO energy level of the doping material is at least 0.3 eV lower than the LUMO energy level of the hole blocking material, which greatly improves the efficiency of the hole blocking layer injecting electrons into the organic light-emitting layer. The efficiently injected electrons can push the exciton recombination center to shift to the center position of the organic light-emitting layer, avoiding the exciton recombination center of the organic light-emitting layer from being close to the hole blocking layer, which causes the excitons to easily overflow to the hole blocking layer. In this way, the embodiments of the present disclosure improve the utilization rate of carriers in the organic light-emitting layer by selecting appropriate host materials, doping materials and hole blocking materials.

[0065] In the embodiment of the present disclosure, the optical band gap of the hole blocking material is at least 0.3 eV larger than the optical band gap of the main material; the optical band gap of the main material is at least 0.3 eV larger than the optical band gap of the dopant material. The excitons generated on the main material can be efficiently transferred to the dopant material, but the excitons generated on the main material are difficult to diffuse to the hole blocking material, thereby improving the exciton utilization rate of the organic electroluminescent device. In the embodiment of the present disclosure, the LUMO energy level, HOMO energy level, and optical band gap of the main material, dopant material, and hole blocking material cooperate with each other, which can effectively improve the utilization rate of carriers and excitons of the organic light-emitting layer, thereby effectively improving the current efficiency at low current density, reducing the roll on phenomenon, and further reducing the color deviation of the display panel caused by the roll on phenomenon.

[0066] In one example, the optical band gap of the hole blocking material is at least 0.6 eV greater than the optical band gap of the host material; in this way, the exciton blocking effect of the hole blocking layer can be further improved.

[0067] In one embodiment of the present disclosure, the doping material is a blue fluorescent doping material, and thus the organic electroluminescent device is a blue organic electroluminescent device.

[0068] In one embodiment of the present disclosure, in the organic light-emitting layer, the mass proportion of the host material is not less than 98%, and correspondingly, the mass proportion of the doping material is not more than 2%.

[0069] In one embodiment of the present disclosure, the organic light emitting layer includes only a host material and a doping material.

[0070] In one embodiment of the present disclosure, the host material is a hole-type host material, that is, the hole mobility of the host material is greater than the electron mobility. In this way, the utilization rate of holes can be improved. At the same time, the hole blocking material can effectively block holes and excitons, inhibiting the diffusion of holes and excitons to the hole blocking layer; this allows the host material and the hole blocking material to cooperate with each other, further improving the utilization rate of holes and excitons.

[0071] In one embodiment of the present disclosure, the thickness of the organic light-emitting layer is between 10 nanometers and 25 nanometers. For example, the thickness of the organic light-emitting layer is 10 nanometers, 12 nanometers, 14 nanometers, 16 nanometers, 18 nanometers, 20 nanometers, 22 nanometers, 24 nanometers, or 25 nanometers.

[0072] In one embodiment of the present disclosure, the thickness of the hole blocking layer is between 1 nm and 10 nm. For example, the thickness of the hole blocking layer is 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm.

[0073] In one embodiment of the present disclosure, the host material is selected from the compound represented by chemical formula (I), or a derivative of the compound represented by chemical formula (I);

[0074]

[0075] Wherein, in the compound represented by chemical formula (I), Ar1 and Ar2 are the same or different, and are independently selected from substituted or unsubstituted aryl groups having 6 to 40 carbon atoms, and substituted or unsubstituted heteroaryl groups having 12 to 20 carbon atoms; when Ar1 or Ar2 has a substituent, the substituent on Ar1 or Ar2 is independently selected from deuterium, an alkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 15 carbon atoms;

[0076] X is selected from sulfur or oxygen;

[0077] The derivative of the compound represented by chemical formula (I) is a compound formed by replacing at least one hydrogen of the compound represented by chemical formula (I), and each substituent is independently selected from deuterium, fluorine, cyano, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 15 carbon atoms, and a heteroaryl group having 12 to 20 carbon atoms.

[0078] In this embodiment, the main material is modified by Ar1 and Ar2 to ensure efficient carrier transmission while reducing the rigidity of the parent core structure (containing anthracene parent core) and increasing the stereochemistry of the compound, which is beneficial to improving the film-forming properties of the main material, reducing defects in the organic light-emitting layer, and further beneficial to improving the fluorescence quantum efficiency.

[0079] In one example, Ar1 and Ar2 are the same or different, and are independently selected from phenyl, naphthyl, biphenyl, dibenzofuranyl, dibenzothienyl, dimethylfluorenyl, and diphenylfluorenyl.

[0080] In one example, the derivative of the compound represented by chemical formula (I) is a compound formed by replacing at least one hydrogen of the compound represented by chemical formula (I), and each substituent is independently selected from deuterium, fluorine, cyano, methyl, ethyl, isopropyl, tert-butyl, phenyl, naphthyl, anthracenyl, phenanthrenyl, biphenyl, fluorenyl, dibenzofuranyl, dibenzothiophenyl, and carbazole.

[0081] In one example, the compound represented by the chemical formula (I) is selected from the group consisting of the following compounds:

[0082]

[0083]

[0084]

[0085] In one embodiment of the present disclosure, the hole blocking material is selected from the compound represented by chemical formula (II):

[0086]

[0087] Wherein, Ar3 and Ar4 are the same or different and are independently selected from an alkyl group having 1 to 40 carbon atoms and an aryl group having 6 to 60 carbon atoms; Ar3 and Ar4 may also be connected to each other to form a ring;

[0088] n is 1 or 2 or 3;

[0089] Z1, Z2, and Z3 are CH or nitrogen, and at least one of them is nitrogen.

[0090] In this embodiment, the electron-donating group and the electron-withdrawing group of the hole-blocking material are connected by a connecting group, and the connecting group is a phenylene group or a plurality of phenylene groups connected in series. In this way, the interaction between the electron-donating group and the electron-withdrawing group is weakened, so that it has a higher energy gap and a higher triplet energy level, which can effectively inhibit the diffusion of excitons, improve the exciton utilization rate of the organic light-emitting layer, and thus help improve roll-on.

[0091] In one example, Ar3 and Ar4 are the same or different, and are independently selected from methyl, phenyl, biphenyl, and naphthyl. For example, Ar3 and Ar4 are both methyl.

[0092] In one example, Ar3 and Ar4 are connected to each other and form a fluorene group with the commonly connected carbon atom.

[0093] In one example, Ar3 and Ar4 are connected to each other, and form a saturated aliphatic ring of 5 to 10 carbon atoms with the carbon atom to which they are connected, such as cyclopentane, cyclohexane or adamantane.

[0094] In one example, the hole blocking material is selected from the group consisting of the following compounds:

[0095]

[0096]

[0097] In one embodiment of the present disclosure, the light-emitting functional layer further includes a hole transport layer HTL located between the organic light-emitting layer EML and the anode, and further includes an electron transport layer ETL located between the hole blocking layer HBL and the cathode. Wherein, the hole transport layer HTL has a hole transport material, and the HOMO energy level of the hole transport material is not less than -5.5eV. The electron transport layer ETL has an electron transport material, and the LUMO energy level of the electron transport material is not less than -2.7eV. The ratio of the hole mobility of the hole transport material to the electron mobility of the electron transport material is not greater than 5. In this way, the hole transport material and the electron transport material have suitable energy levels and higher carrier mobility, which is conducive to improving the balance of electron transport and hole transport. In this way, the balance of electrons and holes injected into the organic light-emitting layer can be improved, which makes the center of the exciton recombination zone as close as possible to the center of the organic light-emitting layer, and the exciton recombination zone can be widened, which can effectively improve the exciton utilization rate.

[0098] In one example, the electron transport layer ETL includes not only electron transport materials but also doping materials such as Liq to further adjust the electron injection efficiency of the electron transport layer ETL and further balance the electrons and holes injected into the organic light emitting layer.

[0099] In one example, when the electron transport layer ETL is formed by an evaporation process, the film formation rate ratio of the electron transport material and Liq is substantially 1:1.

[0100] In one embodiment of the present disclosure, the hole transport material is selected from the compound represented by the following chemical formula (III):

[0101]

[0102] Wherein, Ar5 and Ar6 are the same or different and are independently selected from Formula A-1, Formula A-2, and Formula A-3; and at least one of Ar5 and Ar6 is selected from one of Formula A-2 and Formula A-3;

[0103]

[0104] wherein Ar7 is selected from hydrogen, deuterium, phenyl, biphenyl;

[0105] Wherein, R1 and R2 are the same or different and are independently selected from substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, substituted or unsubstituted aryl groups having 6 to 13 carbon atoms, or R1 and R2 can be linked to form a ring through a single bond.

[0106] In this embodiment, the hole transport material has a carbazole and triarylamine structure and a large conjugated system, which makes the hole transport material have a faster hole mobility. In addition, the hole transport material has at least two large steric hindrance groups, so the molecular structure is relatively distorted, which can inhibit the π-π stacking between molecules and improve the film-forming performance of the hole transport material.

[0107] In one example, R1 and R2 are the same or different, and are independently selected from methyl and phenyl.

[0108] In one example, the hole transport material is selected from the group consisting of the following compounds:

[0109]

[0110] In one embodiment of the present disclosure, the electron transport material is selected from the compound represented by the following chemical formula (IV):

[0111]

[0112] Wherein, Ar8, Ar9, Ar 10 ,Ar 11 are the same or different and each independently represents a substituted or unsubstituted aryl group of 6 to 30 carbon atoms, or a substituted or unsubstituted heteroaryl group of 5 to 30 carbon atoms;

[0113] When Ar8, Ar9, Ar 10 ,Ar 11 When there are substituents on the above, any two substituents are the same or different, and any one of the substituents is selected from protium, deuterium, tritium, cyano, fluorine atom, alkyl group of 1 to 20 carbon atoms, aryl group of 6 to 30 carbon atoms, heteroaryl group of 5 to 30 carbon atoms; wherein the heteroatom in the heteroaryl group is selected from one or more of oxygen atom, sulfur atom or nitrogen atom.

[0114] In this embodiment, the electron transport material has a relatively twisted molecular structure, which can inhibit the π-π stacking between molecules, thereby improving the film-forming property of the electron transport material. In addition, the electron transport material has two triazine mother cores, which have a large electron mobility, which is beneficial to balancing the transmission rate of electrons and holes, and is beneficial to making the exciton recombination zone shift to the middle of the organic light-emitting layer, thereby helping to improve the exciton utilization efficiency of the organic light-emitting layer.

[0115] In one example, Ar4, Ar5, Ar6, and Ar7 are the same or different, and are independently selected from: substituted or unsubstituted phenyl, substituted or unsubstituted pyridyl, substituted or unsubstituted biphenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted anthracenyl;

[0116] When Ar4, Ar5, Ar6, Ar7 have a substituent, the substituent is selected from cyano.

[0117] In one example, the electron transport material is selected from the group consisting of the following compounds:

[0118]

[0119] In one embodiment of the present disclosure, the organic electroluminescent device further comprises a hole injection layer HIL. The hole injection layer may be selected from, but not limited to, inorganic oxides, p-type dopants of a strong electron-withdrawing system and dopants of hole transport materials, such as hexacyanohexaazatriphenylene, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), 1,2,3-tri[(cyano)(4-cyano-2,3,5,6-tetrafluorophenyl)methylene]cyclopropane, etc. Inorganic oxides include, but are not limited to, molybdenum oxide, titanium oxide, vanadium oxide, rhenium oxide, ruthenium oxide, chromium oxide, zirconium oxide, hafnium oxide, tantalum oxide, silver oxide, tungsten oxide, manganese oxide, etc.

[0120] In one embodiment of the present disclosure, the organic electroluminescent device may further include an electron blocking layer EBL. The electron blocking layer also has good hole transport properties.

[0121] In one embodiment of the present disclosure, the organic electroluminescent device may further include an EIL electron injection layer. The electron injection layer is generally an alkali metal or metal, such as LiF, Yb, Mg, Ca or their compounds. Optionally, the thickness of the electron injection layer may be between 1 and 10 nm.

[0122] Optionally, the organic electroluminescent device may be formed on a substrate. In one example, the substrate may be a transparent rigid or flexible substrate material, such as a glass material or a polyimide material.

[0123] In one embodiment of the present disclosure, the anode is a high work function electrode material, such as transparent oxide ITO, IZO; it can also be a composite electrode formed by ITO / Ag / ITO, Ag / IZO, CNT / ITO, CNT / IZO, GO / ITO, GO / IZO, etc.

[0124] As follows, a plurality of organic electroluminescent devices are prepared to verify the performance of the organic electroluminescent device provided by the present disclosure. The prepared organic electroluminescent device includes an anode, a hole injection layer, a hole transport layer, an electron blocking layer, an organic light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer and a cathode which are stacked in sequence. In each organic electroluminescent device, the thickness of the same film layer is the same, and the difference is only that the materials of some film layers are different.

[0125] In each of the prepared organic electroluminescent devices:

[0126] The material of the anode is ITO with a thickness of 150nm;

[0127] The material of the hole injection layer is the compound HATCN, and the thickness is 5nm;

[0128] The hole transport layer is made of hole transport material with a thickness of 50 nm;

[0129] The material of the electron blocking layer is the compound TCTA, with a thickness of 5 nm;

[0130] The organic light-emitting layer includes a main material and a doping material, the doping ratio of the doping material is 2wt%, and the total thickness is 20nm; the doping material is compound BD-1;

[0131] The hole blocking layer is made of hole blocking material with a thickness of 5 nm;

[0132] The electron transport layer includes 1:1 doped electron transport material and Liq, with a thickness of 30 nm;

[0133] The material of the electron injection layer is LiF, and the thickness is 1nm;

[0134] The material of the cathode is Al and the thickness is 150nm.

[0135] The organic electroluminescent devices prepared in Comparative Examples 1 to 5 are comparative devices 1 to 5; the organic electroluminescent devices prepared in Example 1 and Example 2 are verification devices 1 to 2.

[0136] The materials of each organic electroluminescent device are shown in Table 1:

[0137] Table 1: Materials of various organic electroluminescent devices

[0138]

[0139] The structural formulas of the materials used in the above-mentioned organic electroluminescent devices are as follows:

[0140]

[0141]

[0142] The current efficiency of each of the above organic electroluminescent devices was tested at different driving currents (normalized), and the results are shown in Table 2:

[0143] Table 2: Performance of comparison and test devices

[0144]

[0145] In Table 2, Roll-on is CE@10mA / cm 2 With CE@0.01mA / cm 2 The smaller the Roll-on is, the smoother the efficiency curve is, and the efficiency at low current and high current is close.

[0146] The performance of the materials of each layer of the comparative device 1 does not meet the requirements and the compatibility is poor, the device efficiency is low and the roll-on is large.

[0147] The hole transport layer in the comparative device 2 uses the compound Ref1, and the electron transport layer in the comparative device 5 uses the compound Ref4. Although the device efficiency is improved compared with the comparative device 1, the unbalanced carrier transport still leads to a large roll-on.

[0148] In comparison device 3, the main material uses compound Ref3, the carrier transport characteristics of the device are relatively balanced, and the Roll-on is improved; however, the performance of the main material is poor, and the exciton utilization rate is low, resulting in low device efficiency.

[0149] In the comparative device 4, the hole blocking layer adopts compound Ref4, the carrier transport characteristics of the device are relatively balanced, and the roll-on is improved; however, the hole blocking layer material cannot effectively inhibit the diffusion of excitons, resulting in low device efficiency.

[0150] Test device 1 and test device 2 have high device efficiency and significantly improved Roll-on. This is because the mobility and energy level matching of the materials selected for test device 1 and test device 2 make carrier transmission more balanced and broaden the exciton recombination zone; at the same time, the selection of the main material increases the exciton utilization rate and improves the device efficiency. In addition, the selection of the hole blocking layer material can better limit the leakage of excitons in the light-emitting layer to the electron transport layer, further improving the exciton utilization rate in the light-emitting layer under low current. The above effects combined can achieve high device efficiency and low Roll-on value.

[0151] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

Claims

1. An organic electroluminescent device, characterized in that: The organic electroluminescent device comprises an anode, a light-emitting functional layer and a cathode which are stacked in sequence; the light-emitting functional layer comprises an organic light-emitting layer and a hole blocking layer stacked on the surface of the organic light-emitting layer; the organic light-emitting layer comprises a main material and a doping material, and the hole blocking layer comprises a hole blocking material; wherein the HOMO energy level of the host material is at least 0.4 eV higher than the HOMO energy level of the hole blocking material; The LUMO energy level of the host material is at least 0.1 eV lower than the LUMO energy level of the dopant material; The LUMO energy level of the doping material is at least 0.3 eV lower than the LUMO energy level of the hole blocking material; The optical band gap of the hole blocking material is at least 0.3 eV greater than the optical band gap of the host material; The optical band gap of the host material is at least 0.3 eV greater than the optical band gap of the dopant material.

2. The organic electroluminescent device according to claim 1, characterized in that: The main material is selected from the compound represented by chemical formula (I), or a derivative of the compound represented by chemical formula (I); Wherein, in the compound represented by chemical formula (I), Ar1 and Ar2 are the same or different, and are independently selected from substituted or unsubstituted aryl groups having 6 to 40 carbon atoms, and substituted or unsubstituted heteroaryl groups having 12 to 20 carbon atoms; when Ar1 or Ar2 has a substituent, the substituent on Ar1 or Ar2 is independently selected from deuterium, an alkyl group having 1 to 10 carbon atoms, and an aryl group having 6 to 15 carbon atoms; X is selected from sulfur or oxygen; The derivative of the compound represented by chemical formula (I) is a compound formed by replacing at least one hydrogen of the compound represented by chemical formula (I), and each substituent is independently selected from deuterium, fluorine, cyano, an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 15 carbon atoms, and a heteroaryl group having 12 to 20 carbon atoms.

3. The organic electroluminescent device according to claim 2, characterized in that: The compound represented by the chemical formula (I) is selected from the group consisting of the following compounds:

4. The organic electroluminescent device according to claim 1, characterized in that: The hole blocking material is selected from the compound represented by chemical formula (II): Wherein, Ar3 and Ar4 are the same or different and are independently selected from an alkyl group having 1 to 40 carbon atoms and an aryl group having 6 to 60 carbon atoms; Ar3 and Ar4 may also be connected to each other to form a ring; n is 1 or 2 or 3; Z1, Z2, and Z3 are CH or nitrogen, and at least one of them is nitrogen.

5. The organic electroluminescent device according to claim 4, characterized in that: The hole blocking material is selected from the group consisting of the following compounds:

6. The organic electroluminescent device according to claim 1, characterized in that: The light-emitting functional layer further includes a hole transport layer located between the organic light-emitting layer and the anode, and an electron transport layer located between the hole blocking layer and the cathode; The hole transport layer comprises a hole transport material, and the HOMO energy level of the hole transport material is not less than -5.5 eV; the electron transport layer comprises an electron transport material, and the LUMO energy level of the electron transport material is not less than -2.7 eV; The ratio of the hole mobility of the hole transport material to the electron mobility of the electron transport material is not greater than 5.

7. The organic electroluminescent device according to claim 6, characterized in that: The hole transport material is selected from the compound represented by the following chemical formula (III): Wherein, Ar5 and Ar6 are the same or different and are independently selected from Formula A-1, Formula A-2, and Formula A-3; and at least one of Ar5 and Ar6 is selected from one of Formula A-2 and Formula A-3; wherein Ar7 is selected from hydrogen, deuterium, phenyl, biphenyl; Wherein, R1 and R2 are the same or different and are independently selected from substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, substituted or unsubstituted aryl groups having 6 to 13 carbon atoms, or R1 and R2 can be linked to form a ring through a single bond.

8. The organic electroluminescent device according to claim 6, characterized in that: The electron transport material is selected from the compound represented by the following chemical formula (IV): Wherein, Ar8, Ar9, Ar 10 ,Ar 11 are the same or different and each independently represents a substituted or unsubstituted aryl group of 6 to 30 carbon atoms, or a substituted or unsubstituted heteroaryl group of 5 to 30 carbon atoms; When Ar8, Ar9, Ar 10 ,Ar 11 When there are substituents on the above, any two substituents are the same or different, and any one of the substituents is selected from protium, deuterium, tritium, cyano, fluorine atom, alkyl group of 1 to 20 carbon atoms, aryl group of 6 to 30 carbon atoms, heteroaryl group of 5 to 30 carbon atoms; wherein the heteroatom in the heteroaryl group is selected from one or more of oxygen atom, sulfur atom or nitrogen atom.

9. The organic electroluminescent device according to claim 6, characterized in that: The hole transport material is selected from the group consisting of the following compounds: The electron transport material is selected from the group consisting of the following compounds:

10. A display panel comprising a plurality of light emitting elements; wherein: At least one of the light-emitting elements is an organic electroluminescent device according to any one of claims 1 to 9.

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