Patent Application
20220407026
This application claims priority to Chinese Patent Application No. CN 202110592096.5 filed on May 28, 2021 and Chinese Patent Application No. CN 202210355382.4 filed on Apr. 7, 2022, the disclosure of which are incorporated herein by reference in their entireties.
The present disclosure relates to an organic electroluminescent device and a display assembly including the organic electroluminescent device.
Organic electroluminescent devices (such as organic light-emitting diodes (OLEDs)) have been developed for nearly three decades from a double organic layer structure originally reported by Tang and Van Slyke of Eastman Kodak (Applied Physics Letters, 1987, 51 (12): 913-915) to a structure having 6 to 7 function layers, which is widely commercialized at present. The introduction of various function layers greatly improves the transport performance of carriers, and materials of different function layers may be selected to control the balance of carriers, thus greatly improving device performance. However, the introduction of more function layers and materials thereof requires more process steps and more vacuum chambers, which inevitably increases a production cost. Additionally, more interfaces result from more function layers, and an interface is generally a weak link in a carrier transporting process due to the existence of defects, which often affects the device performance (Jiang Y, Zhou D Y, Dong S C, et al. 19-2: Sid Symposium Digest of Technical Papers, 2019) (H. Yamamoto et al., 52.3, 758•SID 2014 DIGEST). Therefore, if the device structure can be simplified and the number of film layers and/or materials can be reduced on the premise that the device performance is basically maintained, the production cost can be effectively reduced.
The currently commercialized device structure includes a cathode, an anode and a series of organic function layers arranged between the cathode and anode, where the organic function layers include a hole injection layer (HIL), a hole transporting layer (HTL), an electron blocking layer (EBL), an emissive layer (EML), a hole blocking layer (HBL), an electron transporting layer (ETL) and an electron injection layer (EIL), etc. The HIL is generally made of a hole transporting material (HTM) doped with a low proportion of conductive p-type doping material (PD), where a doping ratio is generally from 1% to 3%. The HTL is generally made of the HTM used in the HIL. The emissive layer is generally made of at least one host material and at least one light-emitting material. Some emissive layers may adopt a dual-host architecture, and an emissive layer emitting yellow or white light may adopt a dual-light-emitting material architecture. Generally speaking, the host material in the emissive layer has a deeper HOMO energy level than the HTM so that holes face a relatively high potential barrier if they travel directly from the HTL to the EML. To solve this problem, the EBL (also known as a prime layer or a second hole transporting layer) is introduced, which has a HOMO energy level between those of the HTM and the host material. To simplify the device structure, a feasible idea is to combine the HTL and the EBL into one layer and use an HTM with a deep energy level to connect the HIL and the EML. This results in the problem that the HTM with a deep energy level needs to be doped with a PD material with a deeper LUMO energy level such that the HTM has a good hole injection ability. However, the currently commercialized PD material has a LUMO energy level of −5.05 eV and cannot be effectively used as the p-type doping material for the HTM with a deep energy level.
CN201911209540X is a previous application of the applicant and discloses that a PD material with a relatively deep LUMO energy level is doped into a hole transporting material (HTM) with a relatively deep HOMO energy level, which are co-deposited as a hole injection layer (HIL) used in a bottom-emitting device emitting blue light. Due to better matched energy levels and reduced film layers and materials, the device has a reduced voltage and a prolonged lifetime and the process is simplified. However, this application adopts a bottom-emitting device, and the cathode, anode and electron injection layer thereof are all different from those of a top-emitting device, which brings about a difference in carrier distribution in the system of the device. CN2021101318064 is a previous application of the applicant and discloses an embodiment in which simple structures are vertically stacked to form a device with stacked layers, and the device obtains good performance. In this application, multiple light-emitting units are arranged in a physical form of being vertically stacked so that the circuit has a series characteristic. Such OLEDs are referred to as stacked OLEDs (in terms of the physical form) or series OLEDs (in terms of a circuit connection). However, the structure of the top-emitting device is optimized in neither of the above applications. When the structure of the top-emitting device is optimized, the HTM has a larger thickness and the performance, especially electrical performance, of other relevant function layers must be comprehensively investigated to meet the requirement of the device for a low voltage, which is not mentioned in the above applications.
At present, the most commonly used device structure in display applications is the top-emitting device. Generally, thicker HTL and EBL are used so as to adjust a microcavity effect and achieve a target color. For example, the total thickness of the HTL and the EBL in the top-emitting device emitting red or green light is generally around 180-190 nm. If the HTM with a deep HOMO energy level is used in such a thick film layer, the voltage will rise sharply with certainty so that the device performance is seriously affected. Additionally, the cathode, anode and electron injection layer of the top-emitting device all use different materials from those of the bottom-emitting device. For example, a conventional bottom-emitting device uses Liq with a thickness of 1-2 nm as the EIL and Al (opaque) with a thickness of above 100 nm as the cathode; and the top-emitting device generally uses Yb with a thickness of 1-2 nm as the EIL and a Mg—Ag alloy (translucent, a ratio of Mg:Ag generally being 1:9) with a thickness of 10-15 nm as the cathode. In this manner, the bottom-emitting device and the top-emitting device have different electron injection situations so that the whole device systems have different carrier balance situations. Differences lie in not only the cathodes but also the anodes. Though ITO anodes are used in both the bottom-emitting device and the top-emitting device, the ITO layer used for hole injection in the top-emitting device is generally very thin and typically has a thickness of 5-20 nm while the ITO layer in the bottom-emitting device typically has a thickness of 80-120 nm. ITO layers with different thicknesses have different surface roughness, which also affects hole injection. Moreover, the ITO anodes in the top-emitting device and the bottom-emitting device are generally prepared by different processes so that a deviation is introduced into the work function of ITO, which further affects hole injection. Therefore, the practice of simple structures in the top-emitting device requires re-optimization and selection of materials.
Additionally, the HIL in a conventional top-emitting device is generally in the form of an HTM doped with a PD material and typically has a thickness of 10 nm and a conductivity of 1×10−3 S/m to ensure a good hole injection ability, and accordingly the selected HTM has a relatively shallow HOMO energy level which is generally around −5.1 eV. The commonly used host material in the emissive layer has a HOMO energy level of about −5.4 eV and lower so that an energy level difference of greater than about 0.3 eV is formed between the HTM and the host material, which affects hole transport. Though sufficient holes are injected from the anode to the HIL, the transport of holes from the HIL to the EML is limited by a high potential barrier so that the EBL needs to be added for potential barrier transition, which increases the production cost and complexity and generally affects the device performance to a certain degree. On the other hand, a large number of holes are injected from the HIL to the HTL and further transported to the EBL or EML. However, due to a relatively high potential barrier at the interface, holes accumulate at the interface, resulting in excessive holes, which also affects the device performance. In the present disclosure, researches show that an HTM with a relatively deep HOMO energy level is selected in the device to match the energy level of the host material and disposed between the HIL and the EML to reduce the potential barrier and reduce film layers, which can reduce the production cost and improve the device performance. Meanwhile, a PD material with a deep energy level is doped into the HTM to ensure good hole injection. In this case, the conductivity may be reduced to 1×10−4 S/m. However, since the HTM doped with PD can better match the hole transporting layer and avoid the excess and accumulation of holes, the voltage can be reduced and the lifetime can be prolonged in the case where the efficiency is basically unchanged. In fact, lower conductivity is conducive to reducing the risk of crosstalk between pixels in the device.
The present disclosure aims to provide an organic electroluminescent device to solve at least part of the above problems.
According to an embodiment of the present disclosure, an organic electroluminescent device is disclosed. The organic electroluminescent device comprises:
a substrate;
a first electrode disposed on the substrate;
a second electrode disposed over the first electrode; and
an organic layer disposed between the first electrode and the second electrode;
wherein the first electrode is a material with high reflectivity or a combination of materials with high reflectivity, and the second electrode is a translucent or transparent material or a combination of translucent or transparent materials;
the organic layer comprises a first organic layer, a second organic layer and a third organic layer;
the first organic layer comprises a first organic material and a second organic material;
the second organic layer is made of the second organic material and has a thickness of greater than 80 nm;
the third organic layer is a light-emitting layer comprising at least one light-emitting material and at least one host material;
the first organic layer has a conductivity of greater than 1×10−4 S/m and less than 1×10−2 S/m;
an energy level difference between a HOMO energy level of the second organic material and a HOMO energy level of the at least one host material is less than 0.27 eV;
one side of the first organic layer is in direct contact with the first electrode, and the other side of the first organic layer is in direct contact with the second organic layer.
According to an embodiment of the present disclosure, a first organic electroluminescent device is disclosed. The first organic electroluminescent device comprises:
a substrate;
a first electrode disposed on the substrate;
a second electrode disposed over the first electrode; and
an organic layer disposed between the first electrode and the second electrode;
wherein the first electrode is a material with high reflectivity or a combination of materials with high reflectivity, and the second electrode is a translucent or transparent material or a combination of translucent or transparent materials;
the organic layer comprises a first organic layer, a second organic layer and a third organic layer;
the first organic layer comprises a first organic material and a second organic material;
the second organic layer is made of the second organic material and has a first thickness;
the third organic layer is a light-emitting layer comprising at least one light-emitting material and at least one host material;
the first organic layer has a conductivity of greater than 1×10−4 S/m and less than 1×10−2 S/m;
an energy level difference between a HOMO energy level of the second organic material and a HOMO energy level of the at least one host material is less than 0.27 eV;
a voltage of the first organic electroluminescent device is not higher than 110% of a voltage of a second organic electroluminescent device at the same current density, wherein the second organic electroluminescent device has the same device structure as the first organic electroluminescent device except the following differences:
(1) the first organic layer comprises the first organic material and a third organic material, wherein the third organic material is different from the second organic material;
(2) the second organic layer is made of the third organic material;
(3) a fourth organic layer is comprised between the second organic layer and the third organic layer, wherein the fourth organic layer is made of the second organic material;
wherein a total thickness of the second organic layer and the fourth organic layer in the second organic electroluminescent device is 90% to 110% of the first thickness in the first organic electroluminescent device.
According to another embodiment of the present disclosure, a display assembly is further disclosed. The display assembly comprises the preceding organic electroluminescent device.
According to another embodiment of the present disclosure, a display assembly is further disclosed. The display assembly comprises the preceding first organic electroluminescent device.
The present disclosure discloses an organic electroluminescent device which is an organic electroluminescent device with top emission. The organic electroluminescent device achieves good device performance, such as a reduced device voltage and a prolonged lifetime, by optimizing electrical performance of function layers, such as conductivity of a hole injection layer and an energy level difference between a hole transporting material and a host material in a light-emitting layer.
An OLED device generally includes an anode layer, a hole injection layer (HIL), a hole transporting layer (HTL), an electron blocking layer (EBL), an emissive layer (EML), a hole blocking layer (HBL), an electron transporting layer (ETL), an electron injection layer (EIL), a cathode layer and a capping layer. There are more examples for each of these layers. For example, a flexible and transparent substrate-anode combination is disclosed in U.S. Pat. No. 5,844,363, which is incorporated by reference in its entirety. An example of p-doped hole transporting layers is m-MTDATA doped with F4-TCNQ at a molar ratio of 50:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980 which is incorporated by reference in its entirety. Examples of host materials are described in U.S. Pat. No. 6,360,562 issued to Thompson et al., which is incorporated by reference in its entirety. An example of n-doped electron transporting layers is BPhen doped with Li at a molar ratio of 1:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980 which is incorporated by reference in its entirety. U.S. Pat. Nos. 5,703,436 and 5,707,745, both which are incorporated by reference in their entireties, disclose examples of cathodes, including composite cathodes having a thin metal layer such as Mg:Ag and an overlying transparent, conductive, sputter-deposited ITO layer. The principle and use of blocking layers are described in detail in U.S. Pat. No. 6,097,147 and U.S. Patent Application Publication No. 2003/0230980, both which are incorporated by reference in their entireties. U.S. Patent Application Publication No. 2004/0174116 which is incorporated by reference in its entirety provides examples of injection layers. The description about protective layers can be found in U.S. Patent Application Publication No. 2004/0174116 which is incorporated by reference in its entirety.
The above-mentioned layered structure is provided via non-limiting embodiments. The function of the OLED can be implemented by combining the various layers described above, or some layers can be omitted. The OLED can also include other layers that are not explicitly described herein. In each layer, a single material or a mixture of multiple materials can be used to achieve the best performance. Any functional layer can include several sub-layers. For example, the light-emitting layer can have two different layers of light-emitting materials to achieve a desired light-emitting spectrum.
In an embodiment, the OLED can be described as an OLED having an “organic layer” disposed between the cathode and the anode. This organic layer can include one or more layers.
The device fabricated in accordance with embodiments of the present disclosure can be incorporated into a wide variety of consumer products that have one or more of the electronic component modules (or units) of this device. Some examples of such consumer products include flat panel displays, monitors, medical monitors, televisions, billboards, lights for indoor or outdoor lighting and/or signaling, head-up displays, fully or partially transparent displays, flexible displays, smart phones, tablets, phablets, wearable devices, smart watches, laptop computers, digital cameras, camcorders, viewfinders, micro-displays, 3-D displays, vehicles displays, and vehicle tail lights.
The materials and structures described herein can also be used in other organic electronic devices listed above.
As used herein, “top” means being located furthest away from the substrate while “bottom” means being located closest to the substrate. In a case where a first layer is described as “being disposed over” a second layer, the first layer is disposed further away from the substrate. There may be other layers between the first and second layers, unless it is specified that the first layer is “in contact with” the second layer. For example, a cathode can still be described as “being disposed over” an anode, even though there are various organic layers between the cathode and the anode.
“Solution processible”, as used herein, means that capable of being dissolved, dispersed or transported in a liquid medium in the form of a solution or suspension and/or deposited from a liquid medium.
The work function of the metal herein refers to the minimum amount of energy required to move an electron from the interior to the surface of an object. All “work functions of the metal” herein are expressed as negative values, that is, the smaller the numerical value (i.e., the larger the absolute value), the larger amount of energy required to pull the electron to the vacuum level. For example, “the work function of the metal is less than −5 eV” means that the amount of energy required to pull the electron to the vacuum level is greater than 5 eV.
Herein, the numerical values of a highest occupied molecular orbital (HOMO) energy level and a lowest occupied molecular orbital (LUMO) energy level are measured through electrochemical cyclic voltammetry, which is the most commonly used method of measuring energy levels of organic materials. The test is conducted using an electrochemical workstation modelled CorrTest CS120 produced by Wuhan Corrtest Instruments Corp., Ltd and using a three-electrode working system where: a platinum disk electrode serves as a working electrode, a Ag/AgNO3 electrode serves as a reference electrode, and a platinum wire electrode serves as an auxiliary electrode. Anhydrous DCM is used as a solvent, 0.1 mol/L tetrabutylammonium hexafluorophosphate is used as a supporting electrolyte, a compound to be tested is prepared into a solution of 10−3 mol/L, and nitrogen is introduced into the solution for 10 min for oxygen removal before the test. The parameters of the instrument are set as follows: a scan rate of 100 mV/s, a potential interval of 0.5 mV and a test window of −1 V to 1 V. Herein, all “HOMO energy levels” and “LUMO energy levels” are expressed as negative values, and the smaller the numerical value (i.e., the larger the absolute value), the deeper the energy level. In the present application, the expression that the energy level is smaller than a certain number means that the numerical value of the energy level is smaller than this number, i.e., is more negative. For example, in the present application, the expression that “the LUMO energy level of the first organic material is less than −5.1 eV” means that the numerical value of the LUMO energy level of the first organic material is more negative than −5.1, for example, the LUMO energy level of the first organic material is −5.11 eV. Herein, a difference between HOMO energy levels of an HTM and a host material is defined as HOMOHTM-HOMOHOST. Since the host material generally has a deeper HOMO energy level, the difference is generally positive. Herein, a difference between the HOMO energy level of the HTM and a LUMO energy level of a PD material is defined as LUMOPD-HOMOHTM, and the difference may be positive or negative.
Definition of Terms of Substituents
Halogen or halide—as used herein includes fluorine, chlorine, bromine, and iodine.
Alkyl—as used herein includes both straight and branched chain alkyl groups. Alkyl may be alkyl having 1 to 20 carbon atoms, preferably alkyl having 1 to 12 carbon atoms, and more preferably alkyl having 1 to 6 carbon atoms. Examples of alkyl groups include a methyl group, an ethyl group, a propyl group, an isopropyl group, a n-butyl group, an s-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, a neopentyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 1-pentylhexyl group, a 1-butylpentyl group, a 1-heptyloctyl group, and a 3-methylpentyl group. Of the above, preferred are a methyl group, an ethyl group, a propyl group, an isopropyl group, a n-butyl group, an s-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, a neopentyl group, and an n-hexyl group. Additionally, the alkyl group may be optionally substituted.
Cycloalkyl—as used herein includes cyclic alkyl groups. The cycloalkyl groups may be those having 3 to 20 ring carbon atoms, preferably those having 4 to 10 carbon atoms. Examples of cycloalkyl include cyclobutyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, 4,4-dimethylcylcohexyl, 1-adamantyl, 2-adamantyl, 1-norbornyl, 2-norbornyl, and the like. Of the above, preferred are cyclopentyl, cyclohexyl, 4-methylcyclohexyl, and 4,4-dimethylcylcohexyl. Additionally, the cycloalkyl group may be optionally substituted.
Heteroalkyl—as used herein, includes a group formed by replacing one or more carbons in an alkyl chain with a hetero-atom(s) selected from the group consisting of a nitrogen atom, an oxygen atom, a sulfur atom, a selenium atom, a phosphorus atom, a silicon atom, a germanium atom, and a boron atom. Heteroalkyl may be those having 1 to 20 carbon atoms, preferably those having 1 to 10 carbon atoms, and more preferably those having 1 to 6 carbon atoms. Examples of heteroalkyl include methoxymethyl, ethoxymethyl, ethoxyethyl, methylthiomethyl, ethylthiomethyl, ethylthioethyl, methoxymethoxymethyl, ethoxymethoxymethyl, ethoxyethoxyethyl, hydroxymethyl, hydroxyethyl, hydroxypropyl, mercaptomethyl, mercaptoethyl, mercaptopropyl, aminomethyl, aminoethyl, aminopropyl, dimethylaminomethyl, trimethylgermanylmethyl, trimethylgermanylethyl, trimethylgermanylisopropyl, dimethylethylgermanylmethyl, dimethylisopropylgermanylmethyl, tert-butyldimethylgermanylmethyl, triethylgermanylmethyl, triethylgermanylethyl, triisopropylgermanylmethyl, triisopropylgermanylethyl, trimethylsilylmethyl, trimethylsilylethyl, trimethylsilylisopropyl, triisopropylsilylmethyl, and triisopropylsilylethyl. Additionally, the heteroalkyl group may be optionally substituted.
Alkenyl—as used herein includes straight chain, branched chain, and cyclic alkene groups. Alkenyl may be those having 2 to 20 carbon atoms, preferably those having 2 to 10 carbon atoms. Examples of alkenyl include vinyl, propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1,3-butandienyl, 1-methylvinyl, styryl, 2,2-diphenylvinyl, 1,2-diphenylvinyl, 1-methylallyl, 1,1-dimethylallyl, 2-methylallyl, 1-phenylallyl, 2-phenylallyl, 3-phenylallyl, 3,3-diphenylallyl, 1,2-dimethylallyl, 1-phenyl-1-butenyl, 3-phenyl-1-butenyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, cycloheptenyl, cycloheptatrienyl, cyclooctenyl, cyclooctatetraenyl, and norbornenyl. Additionally, the alkenyl group may be optionally substituted.
Alkynyl—as used herein includes straight chain alkynyl groups. Alkynyl may be those having 2 to 20 carbon atoms, preferably those having 2 to 10 carbon atoms. Examples of alkynyl groups include ethynyl, propynyl, propargyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3,3-dimethyl-1-butynyl, 3-ethyl-3-methyl-1-pentynyl, 3,3-diisopropyl-1-pentynyl, phenylethynyl, and phenylpropynyl, etc. Of the above, preferred are ethynyl, propynyl, propargyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, and phenylethynyl. Additionally, the alkynyl group may be optionally substituted.
Aryl or an aromatic group—as used herein includes non-condensed and condensed systems. Aryl may be those having 6 to 30 carbon atoms, preferably those having 6 to 20 carbon atoms, and more preferably those having 6 to 12 carbon atoms. Examples of aryl groups include phenyl, biphenyl, terphenyl, triphenylene, tetraphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene, preferably phenyl, biphenyl, terphenyl, triphenylene, fluorene, and naphthalene. Examples of non-condensed aryl groups include phenyl, biphenyl-2-yl, biphenyl-3-yl, biphenyl-4-yl, p-terphenyl-4-yl, p-terphenyl-3-yl, p-terphenyl-2-yl, m-terphenyl-4-yl, m-terphenyl-3-yl, m-terphenyl-2-yl, o-tolyl, m-tolyl, p-tolyl, p-(2-phenylpropyl)phenyl, 4′-methylbiphenylyl, 4″-t-butyl-p-terphenyl-4-yl, o-cumenyl, m-cumenyl, p-cumenyl, 2,3-xylyl, 3,4-xylyl, 2,5-xylyl, mesityl, and m-quarterphenyl. Additionally, the aryl group may be optionally substituted.
Heterocyclic group or heterocycle—as used herein includes non-aromatic cyclic groups. Non-aromatic heterocyclic groups includes saturated heterocyclic groups having 3 to 20 ring atoms and unsaturated non-aromatic heterocyclic groups having 3 to 20 ring atoms, where at least one ring atom is selected from the group consisting of a nitrogen atom, an oxygen atom, a sulfur atom, a selenium atom, a silicon atom, a phosphorus atom, a germanium atom, and a boron atom. Preferred non-aromatic heterocyclic groups are those having 3 to 7 ring atoms, each of which includes at least one hetero-atom such as nitrogen, oxygen, silicon, or sulfur. Examples of non-aromatic heterocyclic groups include oxiranyl, oxetanyl, tetrahydrofuranyl, tetrahydropyranyl, dioxolanyl, dioxanyl, aziridinyl, dihydropyrrolyl, tetrahydropyrrolyl, piperidinyl, oxazolidinyl, morpholinyl, piperazinyl, oxepinyl, thiepinyl, azepinyl, and tetrahydrosilolyl. Additionally, the heterocyclic group may be optionally substituted.
Heteroaryl—as used herein, includes non-condensed and condensed hetero-aromatic groups having 1 to 5 hetero-atoms, where at least one hetero-atom is selected from the group consisting of a nitrogen atom, an oxygen atom, a sulfur atom, a selenium atom, a silicon atom, a phosphorus atom, a germanium atom, and a boron atom. A hetero-aromatic group is also referred to as heteroaryl. Heteroaryl may be those having 3 to 30 carbon atoms, preferably those having 3 to 20 carbon atoms, and more preferably those having 3 to 12 carbon atoms. Suitable heteroaryl groups include dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridoindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine, preferably dibenzothiophene, dibenzofuran, dibenzoselenophene, carbazole, indolocarbazole, imidazole, pyridine, triazine, benzimidazole, 1,2-azaborine, 1,3-azaborine, 1,4-azaborine, borazine, and aza-analogs thereof. Additionally, the heteroaryl group may be optionally substituted.
Alkoxy—as used herein, is represented by —O-alkyl, —O-cycloalkyl, —O-heteroalkyl, or —O-heterocyclic group. Examples and preferred examples of alkyl, cycloalkyl, heteroalkyl, and heterocyclic groups are the same as those described above. Alkoxy groups may be those having 1 to 20 carbon atoms, preferably those having 1 to 6 carbon atoms. Examples of alkoxy groups include methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, cyclopropyloxy, cyclobutyloxy, cyclopentyloxy, cyclohexyloxy, tetrahydrofuranyloxy, tetrahydropyranyloxy, methoxypropyloxy, ethoxyethyloxy, methoxymethyloxy, and ethoxymethyloxy. Additionally, the alkoxy group may be optionally substituted.
Aryloxy—as used herein, is represented by —O-aryl or —O-heteroaryl. Examples and preferred examples of aryl and heteroaryl are the same as those described above. Aryloxy groups may be those having 6 to 30 carbon atoms, preferably those having 6 to 20 carbon atoms. Examples of aryloxy groups include phenoxy and biphenyloxy. Additionally, the aryloxy group may be optionally substituted.
Arylalkyl—as used herein, contemplates alkyl substituted with an aryl group. Arylalkyl may be those having 7 to 30 carbon atoms, preferably those having 7 to 20 carbon atoms, and more preferably those having 7 to 13 carbon atoms. Examples of arylalkyl groups include benzyl, 1-phenylethyl, 2-phenylethyl, 1-phenylisopropyl, 2-phenylisopropyl, phenyl-t-butyl, alpha-naphthylmethyl, 1-alpha-naphthylethyl, 2-alpha-naphthylethyl, 1-alpha-naphthylisopropyl, 2-alpha-naphthylisopropyl, beta-naphthylmethyl, 1-beta-naphthylethyl, 2-beta-naphthylethyl, 1-beta-naphthylisopropyl, 2-beta-naphthylisopropyl, p-methylbenzyl, m-methylbenzyl, o-methylbenzyl, p-chlorobenzyl, m-chlorobenzyl, o-chlorobenzyl, p-bromobenzyl, m-bromobenzyl, o-bromobenzyl, p-iodobenzyl, m-iodobenzyl, o-iodobenzyl, p-hydroxybenzyl, m-hydroxybenzyl, o-hydroxybenzyl, p-aminobenzyl, m-aminobenzyl, o-aminobenzyl, p-nitrobenzyl, m-nitrobenzyl, o-nitrobenzyl, p-cyanobenzyl, m-cyanobenzyl, o-cyanobenzyl, 1-hydroxy-2-phenylisopropyl, and 1-chloro-2-phenylisopropyl. Of the above, preferred are benzyl, p-cyanobenzyl, m-cyanobenzyl, o-cyanobenzyl, 1-phenylethyl, 2-phenylethyl, 1-phenylisopropyl, and 2-phenylisopropyl. Additionally, the arylalkyl group may be optionally substituted.
Alkylsilyl—as used herein, contemplates a silyl group substituted with an alkyl group. Alkylsilyl groups may be those having 3 to 20 carbon atoms, preferably those having 3 to 10 carbon atoms. Examples of alkylsilyl groups include trimethylsilyl, triethylsilyl, methyldiethylsilyl, ethyldimethylsilyl, tripropylsilyl, tributylsilyl, triisopropylsilyl, methyldiisopropylsilyl, dimethylisopropylsilyl, tri-t-butylsilyl, triisobutylsilyl, dimethyl t-butylsilyl, and methyldi-t-butylsilyl. Additionally, the alkylsilyl group may be optionally substituted.
Arylsilyl—as used herein, contemplates a silyl group substituted with an aryl group. Arylsilyl groups may be those having 6 to 30 carbon atoms, preferably those having 8 to 20 carbon atoms. Examples of arylsilyl groups include triphenylsilyl, phenyldibiphenylylsilyl, diphenylbiphenylsilyl, phenyldiethylsilyl, diphenylethylsilyl, phenyldimethylsilyl, diphenylmethylsilyl, phenyldiisopropylsilyl, diphenylisopropylsilyl, diphenylbutylsilyl, diphenylisobutylsilyl, diphenyl t-butylsilyl. Additionally, the arylsilyl group may be optionally substituted.
Alkylgermanyl—as used herein contemplates a germanyl group substituted with an alkyl group. The alkylgermanyl may be those having 3 to 20 carbon atoms, preferably those having 3 to 10 carbon atoms. Examples of alkylgermanyl include trimethylgermanyl, triethylgermanyl, methyldiethylgermanyl, ethyldimethylgermanyl, tripropylgermanyl, tributylgermanyl, triisopropylgermanyl, methyldiisopropylgermanyl, dimethylisopropylgermanyl, tri-t-butylgermanyl, triisobutylgermanyl, dimethyl-t-butylgermanyl, and methyldi-t-butylgermanyl. Additionally, the alkylgermanyl group may be optionally substituted.
Arylgermanyl—as used herein contemplates a germanyl group substituted with at least one aryl group or heteroaryl group. Arylgermanyl may be those having 6 to 30 carbon atoms, preferably those having 8 to 20 carbon atoms. Examples of arylgermanyl include triphenylgermanyl, phenyldibiphenylylgermanyl, diphenylbiphenylgermanyl, phenyldiethylgermanyl, diphenylethylgermanyl, phenyldimethylgermanyl, diphenylmethylgermanyl, phenyldiisopropylgermanyl, diphenylisopropylgermanyl, diphenylbutylgermanyl, diphenylisobutylgermanyl, and diphenyl-t-butylgermanyl. Additionally, the arylgermanyl group may be optionally substituted.
The term “aza” in azadibenzofuran, azadibenzothiophene, etc. means that one or more of C—H groups in the respective aromatic fragment are replaced with a nitrogen atom. For example, azatriphenylene encompasses dibenzo[f,h]quinoxaline, dibenzo[f,h]quinoline and other analogs with two or more nitrogens in the ring system. One of ordinary skill in the art can readily envision other nitrogen analogs of the aza-derivatives described above, and all such analogs are intended to be encompassed by the term as set forth herein.
In the present disclosure, unless otherwise defined, when any term of the group consisting of substituted alkyl, substituted cycloalkyl, substituted heteroalkyl, a substituted heterocyclic group, substituted arylalkyl, substituted alkoxy, substituted aryloxy, substituted alkenyl, substituted alkynyl, substituted aryl, substituted heteroaryl, substituted alkylsilyl, substituted arylsilyl, substituted alkylgermanyl, substituted arylgermanyl, substituted amino, substituted acyl, substituted carbonyl, a substituted carboxylic acid group, a substituted ester group, substituted sulfinyl, substituted sulfonyl, and substituted phosphino is used, it means that any group of alkyl, cycloalkyl, heteroalkyl, a heterocyclic group, arylalkyl, alkoxy, aryloxy, alkenyl, alkynyl, aryl, heteroaryl, alkylsilyl, arylsilyl, alkylgermanyl, arylgermanyl, amino, acyl, carbonyl, a carboxylic acid group, an ester group, sulfinyl, sulfonyl, and phosphino may be substituted with one or more moieties selected from the group consisting of deuterium, halogen, unsubstituted alkyl having 1 to 20 carbon atoms, unsubstituted cycloalkyl having 3 to 20 ring carbon atoms, unsubstituted heteroalkyl having 1 to 20 carbon atoms, an unsubstituted heterocyclic group having 3 to 20 ring atoms, unsubstituted arylalkyl having 7 to 30 carbon atoms, unsubstituted alkoxy having 1 to 20 carbon atoms, unsubstituted aryloxy having 6 to 30 carbon atoms, unsubstituted alkenyl having 2 to 20 carbon atoms, unsubstituted alkynyl having 2 to 20 carbon atoms, unsubstituted aryl having 6 to 30 carbon atoms, unsubstituted heteroaryl having 3 to 30 carbon atoms, unsubstituted alkylsilyl having 3 to 20 carbon atoms, unsubstituted arylsilyl group having 6 to 20 carbon atoms, unsubstituted alkylgermanyl having 3 to 20 carbon atoms, unsubstituted arylgermanyl having 6 to 20 carbon atoms, unsubstituted amino having 0 to 20 carbon atoms, an acyl group, a carbonyl group, a carboxylic acid group, an ester group, a cyano group, an isocyano group, a sulfanyl group, a sulfinyl group, a sulfonyl group, a phosphino group, and combinations thereof.
It is to be understood that when a molecular fragment is described as being a substituent or otherwise attached to another moiety, its name may be written as if it was a fragment (e.g. phenyl, phenylene, naphthyl, dibenzofuryl) or as if it was the whole molecule (e.g. benzene, naphthalene, dibenzofuran). As used herein, these different ways of designating a substituent or an attached fragment are considered to be equivalent.
In the compounds mentioned in the present disclosure, hydrogen atoms may be partially or fully replaced by deuterium. Other atoms such as carbon and nitrogen may also be replaced by their other stable isotopes. The replacement by other stable isotopes in the compounds may be preferred due to its enhancements of device efficiency and stability.
In the compounds mentioned in the present disclosure, multiple substitutions refer to a range that includes a di-substitution, up to the maximum available substitutions. When a substituent in the compounds mentioned in the present disclosure represents multiple substitutions (including di-, tri-, and tetra-substitutions, etc.), it means that the substituent may be present at multiple available substitution positions on the structure linked to the substituent, where substituents present at the multiple available substitution positions may have the same structure or different structures.
In the compounds mentioned in the present disclosure, adjacent substituents in the compounds cannot be joined to form a ring unless otherwise explicitly defined, for example, adjacent substituents can be optionally joined to form a ring. In the compounds mentioned in the present disclosure, the expression that adjacent substituents can be optionally joined to form a ring includes the case where adjacent substituents may be joined to form a ring and the case where adjacent substituents are not joined to form a ring. When adjacent substituents can be optionally joined to form a ring, the ring formed may be monocyclic or polycyclic (including spirocyclic, endocyclic, and fusedcyclic, etc.) as well as alicyclic, heteroalicyclic, aromatic, or heteroaromatic. In such expression, adjacent substituents may refer to substituents bonded to the same atom, substituents bonded to carbon atoms which are directly bonded to each other, or substituents bonded to carbon atoms which are more distant from each other. Preferably, adjacent substituents refer to substituents bonded to the same carbon atom and substituents bonded to carbon atoms which are directly bonded to each other.
The expression that adjacent substituents can be optionally joined to form a ring is also intended to mean that two substituents bonded to the same carbon atom are joined to each other via a chemical bond to form a ring, which can be exemplified by the following formula:
The expression that adjacent substituents can be optionally joined to form a ring is also intended to mean that two substituents bonded to carbon atoms which are directly bonded to each other are joined to each other via a chemical bond to form a ring, which can be exemplified by the following formula:
The expression that adjacent substituents can be optionally joined to form a ring is also intended to mean that two substituents bonded to further distant carbon atoms are joined to each other via a chemical bond to form a ring, which can be exemplified by the following formula:
Furthermore, the expression that adjacent substituents can be optionally joined to form a ring is also intended to mean that, in the case where one of two adjacent substituents bonded to carbon atoms which are directly bonded to each other represents hydrogen, the second substituent is bonded at a position where the hydrogen atom is bonded, thereby forming a ring. This is exemplified by the following formula:
According to an embodiment of the present disclosure, an organic electroluminescent device is disclosed. The organic electroluminescent device comprises:
a substrate;
a first electrode disposed on the substrate;
a second electrode disposed over the first electrode; and
an organic layer disposed between the first electrode and the second electrode;
wherein the first electrode is a material with high reflectivity or a combination of materials with high reflectivity, and the second electrode is a translucent or transparent material or a combination of translucent or transparent materials;
the organic layer comprises a first organic layer, a second organic layer and a third organic layer;
the first organic layer comprises a first organic material and a second organic material;
the second organic layer is made of the second organic material and has a thickness of greater than 80 nm;
the third organic layer is a light-emitting layer comprising at least one light-emitting material and at least one host material;
the first organic layer has a conductivity of greater than 1×10−4 S/m and less than 1×10−2 S/m;
an energy level difference between a HOMO energy level of the second organic material and a HOMO energy level of the at least one host material is less than 0.27 eV; and
one side of the first organic layer is in direct contact with the first electrode, and the other side of the first organic layer is in direct contact with the second organic layer.
According to an embodiment of the present disclosure, a LUMO energy level of the first organic material is less than −5.1 eV.
According to an embodiment of the present disclosure, the HOMO energy level of the second organic material is less than −5.25 eV.
According to an embodiment of the present disclosure, the second organic layer is in direct contact with the third organic layer.
According to an embodiment of the present disclosure, the first electrode is selected from the group consisting of Ag, Ti, Cr, Pt, Ni, TiN and combinations thereof with ITO and/or MoOx.
According to an embodiment of the present disclosure, the second electrode is selected from a Mg—Ag alloy, MoOx, Yb, Ca, ITO, IZO or a combination thereof.
According to an embodiment of the present disclosure, the energy level difference between the HOMO energy level of the second organic material and the HOMO energy level of the at least one host material is less than or equal to 0.26 eV.
According to an embodiment of the present disclosure, the energy level difference between the HOMO energy level of the second organic material and the HOMO energy level of the at least one host material is less than 0.25 eV.
According to an embodiment of the present disclosure, the energy level difference between the HOMO energy level of the second organic material and the HOMO energy level of the at least one host material is less than 0.2 eV.
According to an embodiment of the present disclosure, an energy level difference between the HOMO energy level of the second organic material and the LUMO energy level of the first organic material is less than 0.23 eV.
According to an embodiment of the present disclosure, the energy level difference between the HOMO energy level of the second organic material and the LUMO energy level of the first organic material is less than 0.2 eV.
According to an embodiment of the present disclosure, the energy level difference between the HOMO energy level of the second organic material and the LUMO energy level of the first organic material is less than or equal to 0.1 eV.
According to an embodiment of the present disclosure, the device further comprises an electron injection layer, where the electron injection layer is disposed between the third organic layer and the second electrode.
According to an embodiment of the present disclosure, the electron injection layer comprises the group consisting of Yb, Liq, LiF and combinations thereof.
According to an embodiment of the present disclosure, the second organic layer has a thickness of greater than or equal to 100 nm.
According to an embodiment of the present disclosure, the second organic layer has a thickness of greater than or equal to 120 nm.
According to an embodiment of the present disclosure, the second organic layer has a thickness of greater than 125 nm.
According to an embodiment of the present disclosure, the second organic layer has a thickness of greater than 150 nm.
According to an embodiment of the present disclosure, the first organic layer has a conductivity of greater than 2×10−4 S/m and less than 8×10−3 S/m.
According to an embodiment of the present disclosure, the first organic material has a structure represented by Formula 1:
wherein in Formula 1,
X and Y are, at each occurrence identically or differently, selected from NR′, CR″R′″, O, S or Se;
Z1 and Z2 are, at each occurrence identically or differently, selected from O, S or Se;
R, R′, R″ and R′″ are, at each occurrence identically or differently, selected from the group consisting of: hydrogen, deuterium, halogen, substituted or unsubstituted alkyl having 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl having 3 to 20 ring carbon atoms, substituted or unsubstituted heteroalkyl having 1 to 20 carbon atoms, a substituted or unsubstituted heterocyclic group having 3 to 20 ring atoms, substituted or unsubstituted arylalkyl having 7 to 30 carbon atoms, substituted or unsubstituted alkoxy having 1 to 20 carbon atoms, substituted or unsubstituted aryloxy having 6 to 30 carbon atoms, substituted or unsubstituted alkenyl having 2 to 20 carbon atoms, substituted or unsubstituted alkynyl having 2 to 20 carbon atoms, substituted or unsubstituted aryl having 6 to 30 carbon atoms, substituted or unsubstituted heteroaryl having 3 to 30 carbon atoms, substituted or unsubstituted alkylsilyl having 3 to 20 carbon atoms, substituted or unsubstituted arylsilyl having 6 to 20 carbon atoms, substituted or unsubstituted alkylgermanyl having 3 to 20 carbon atoms, substituted or unsubstituted arylgermanyl having 6 to 20 carbon atoms, substituted or unsubstituted amino having 0 to 20 carbon atoms, an acyl group, a carbonyl group, a carboxylic acid group, an ester group, a cyano group, an isocyano group, a hydroxyl group, a sulfanyl group, a sulfinyl group, a sulfonyl group, a phosphino group and combinations thereof;
each R may be the same or different, and at least one of R, R′, R″ and R′″ is a group having at least one electron withdrawing group; and
in Formula 1, adjacent substituents can be optionally joined to form a ring.
According to an embodiment of the present disclosure, the second organic material has a structure represented by Formula 2:
wherein in Formula 2,
X1 to X8 are, at each occurrence identically or differently, selected from CR1 or N;
L is, at each occurrence identically or differently, selected from substituted or unsubstituted arylene having 6 to 30 carbon atoms, substituted or unsubstituted heteroarylene having 3 to 30 carbon atoms or a combination thereof;
Ar1 and Ar2 are, at each occurrence identically or differently, selected from substituted or unsubstituted aryl having 6 to 30 carbon atoms or substituted or unsubstituted heteroaryl having 3 to 30 carbon atoms;
R1 is, at each occurrence identically or differently, selected from the group consisting of: hydrogen, deuterium, halogen, substituted or unsubstituted alkyl having 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl having 3 to 20 ring carbon atoms, substituted or unsubstituted heteroalkyl having 1 to 20 carbon atoms, a substituted or unsubstituted heterocyclic group having 3 to 20 ring atoms, substituted or unsubstituted arylalkyl having 7 to 30 carbon atoms, substituted or unsubstituted alkoxy having 1 to 20 carbon atoms, substituted or unsubstituted aryloxy having 6 to 30 carbon atoms, substituted or unsubstituted alkenyl having 2 to 20 carbon atoms, substituted or unsubstituted alkynyl having 2 to 20 carbon atoms, substituted or unsubstituted aryl having 6 to 30 carbon atoms, substituted or unsubstituted heteroaryl having 3 to 30 carbon atoms, substituted or unsubstituted alkylsilyl having 3 to 20 carbon atoms, substituted or unsubstituted arylsilyl having 6 to 20 carbon atoms, substituted or unsubstituted alkylgermanyl having 3 to 20 carbon atoms, substituted or unsubstituted arylgermanyl having 6 to 20 carbon atoms, substituted or unsubstituted amino having 0 to 20 carbon atoms, an acyl group, a carbonyl group, a carboxylic acid group, an ester group, a cyano group, an isocyano group, a hydroxyl group, a sulfanyl group, a sulfinyl group, a sulfonyl group, a phosphino group and combinations thereof; and
in Formula 2, adjacent substituents can be optionally joined to form a ring.
According to an embodiment of the present disclosure, in Formula 1, X and Y are, at each occurrence identically or differently, selected from CR″R′″ or NR′, and at least one of R′, R″ and R′″ is/are a group having at least one electron withdrawing group; preferably, R, R′, R″ and R′″ each are a group having at least one electron withdrawing group.
According to an embodiment of the present disclosure, in Formula 1, X and Y are, at each occurrence identically or differently, selected from O, S or Se, and at least one R is a group having at least one electron withdrawing group; preferably, each R is a group having at least one electron withdrawing group.
According to an embodiment of the present disclosure, in Formula 1, a Hammett constant of the electron withdrawing group is ≥0.05, preferably ≥0.3, and more preferably ≥0.5.
According to an embodiment of the present disclosure, in Formula 1, the electron withdrawing group is selected from the group consisting of: halogen, a nitroso group, a nitro group, an acyl group, a carbonyl group, a carboxylic acid group, an ester group, a cyano group, an isocyano group, SCN, OCN, SF5, a boryl group, a sulfinyl group, a sulfonyl group, a phosphoroso group, an aza-aromatic ring group and any one of the following groups substituted by one or more of halogen, a nitroso group, a nitro group, an acyl group, a carbonyl group, a carboxylic acid group, an ester group, a cyano group, an isocyano group, SCN, OCN, SF5, a boryl group, a sulfinyl group, a sulfonyl group, a phosphoroso group and an aza-aromatic ring group: alkyl having 1 to 20 carbon atoms, cycloalkyl having 3 to 20 ring carbon atoms, heteroalkyl having 1 to 20 carbon atoms, arylalkyl having 7 to 30 carbon atoms, alkoxy having 1 to 20 carbon atoms, aryloxy having 6 to 30 carbon atoms, alkenyl having 2 to 20 carbon atoms, alkynyl having 2 to 20 carbon atoms, aryl having 6 to 30 carbon atoms, heteroaryl having 3 to 30 carbon atoms, alkylsilyl having 3 to 20 carbon atoms, arylsilyl having 6 to 20 carbon atoms and combinations thereof.
According to an embodiment of the present disclosure, in Formula 1, the electron withdrawing group is selected from the group consisting of: F, CF3, OCF3, SF5, SO2CF3, cyano, isocyano, SCN, OCN, pyrimidinyl, triazinyl and combinations thereof.
According to an embodiment of the present disclosure, in Formula 1, X and Y are, at each occurrence identically or differently, selected from the group consisting of the following structures:
wherein R2 is, at each occurrence identically or differently, selected from the group consisting of: hydrogen, deuterium, halogen, a nitroso group, a nitro group, an acyl group, a carbonyl group, a carboxylic acid group, an ester group, a cyano group, an isocyano group, SCN, OCN, SF5, a boryl group, a sulfinyl group, a sulfonyl group, a phosphoroso group, substituted or unsubstituted alkyl having 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl having 3 to 20 ring carbon atoms, substituted or unsubstituted heteroalkyl having 1 to 20 carbon atoms, substituted or unsubstituted arylalkyl having 7 to 30 carbon atoms, substituted or unsubstituted alkoxy having 1 to 20 carbon atoms, substituted or unsubstituted aryloxy having 6 to 30 carbon atoms, substituted or unsubstituted alkenyl having 2 to 20 carbon atoms, substituted or unsubstituted alkynyl having 2 to 20 carbon atoms, substituted or unsubstituted aryl having 6 to 30 carbon atoms, substituted or unsubstituted heteroaryl having 3 to 30 carbon atoms, substituted or unsubstituted alkylsilyl having 3 to 20 carbon atoms, substituted or unsubstituted arylsilyl having 6 to 20 carbon atoms and combinations thereof;
preferably, R2 is, at each occurrence identically or differently, selected from the group consisting of: F, CF3, OCF3, SF5, SO2CF3, cyano, isocyano, SCN, OCN, pentafluorophenyl, 4-cyanotetrafluorophenyl, tetrafluoropyridyl, pyrimidinyl, triazinyl and combinations thereof;
wherein V and W are, at each occurrence identically or differently, selected from CRvRw, NR, O, S or Se;
wherein Ar is, at each occurrence identically or differently, selected from substituted or unsubstituted aryl having 6 to 30 carbon atoms or substituted or unsubstituted heteroaryl having 3 to 30 carbon atoms;
wherein A, Ra, Rb, Re, Rd, Re, Rf, Rg, Rh, Rv and Rw are, at each occurrence identically or differently, selected from the group consisting of: hydrogen, deuterium, halogen, a nitroso group, a nitro group, an acyl group, a carbonyl group, a carboxylic acid group, an ester group, a cyano group, an isocyano group, SCN, OCN, SF5, a boryl group, a sulfinyl group, a sulfonyl group, a phosphoroso group, substituted or unsubstituted alkyl having 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl having 3 to 20 ring carbon atoms, substituted or unsubstituted heteroalkyl having 1 to 20 carbon atoms, substituted or unsubstituted arylalkyl having 7 to 30 carbon atoms, substituted or unsubstituted alkoxy having 1 to 20 carbon atoms, substituted or unsubstituted aryloxy having 6 to 30 carbon atoms, substituted or unsubstituted alkenyl having 2 to 20 carbon atoms, substituted or unsubstituted alkynyl having 2 to 20 carbon atoms, substituted or unsubstituted aryl having 6 to 30 carbon atoms, substituted or unsubstituted heteroaryl having 3 to 30 carbon atoms, substituted or unsubstituted alkylsilyl having 3 to 20 carbon atoms, substituted or unsubstituted arylsilyl having 6 to 20 carbon atoms and combinations thereof;
wherein A is a group having at least one electron withdrawing group, and for any one of the structures, when one or more of Ra, Rb, Rc, Rd, Re, Rf, Rg, Rh, Rv and Rw are present, at least one of Ra, Rb, Rc, Rd, Re, Rf, Rg, Rh, Rv and Rw is a group having at least one electron withdrawing group; preferably, the group having at least one electron withdrawing group is selected from the group consisting of: F, CF3, OCF3, SF5, SO2CF3, cyano, isocyano, SCN, OCN, pentafluorophenyl, 4-cyanotetrafluorophenyl, tetrafluoropyridyl, pyrimidinyl, triazinyl and combinations thereof; and
wherein “*” represents a position where X and Y are joined to a dehydrobenzodioxazole ring, a dehydrobenzodithiazole ring or a dehydrobenzodiselenazole ring in Formula 1.
According to an embodiment of the present disclosure, in Formula 1, X and Y are, at each occurrence identically or differently, selected from the group consisting of the following structures:
wherein “*” represents a position where X or Y is joined to a dehydrobenzodioxazole ring, a dehydrobenzodithiazole ring or a dehydrobenzodiselenazole ring in Formula 1.
According to an embodiment of the present disclosure, in Formula 1, R is, at each occurrence identically or differently, selected from the group consisting of: hydrogen, deuterium, halogen, a nitroso group, a nitro group, an acyl group, a carbonyl group, a carboxylic acid group, an ester group, a cyano group, an isocyano group, SCN, OCN, SF5, a boryl group, a sulfinyl group, a sulfonyl group, a phosphoroso group, unsubstituted alkyl having 1 to 20 carbon atoms, unsubstituted cycloalkyl having 3 to 20 ring carbon atoms, unsubstituted alkoxy having 1 to 20 carbon atoms, unsubstituted alkenyl having 2 to 20 carbon atoms, unsubstituted aryl having 6 to 30 carbon atoms, unsubstituted heteroaryl having 3 to 30 carbon atoms and any one of the following groups substituted by one or more of halogen, a nitroso group, a nitro group, an acyl group, a carbonyl group, a carboxylic acid group, an ester group, a cyano group, an isocyano group, SCN, OCN, SF5, a boryl group, a sulfinyl group, a sulfonyl group and a phosphoroso group: alkyl having 1 to 20 carbon atoms, cycloalkyl having 3 to 20 ring carbon atoms, alkoxy having 1 to 20 carbon atoms, alkenyl having 2 to 20 carbon atoms, aryl having 6 to 30 carbon atoms, heteroaryl having 3 to 30 carbon atoms and combinations thereof.
According to an embodiment of the present disclosure, in Formula 1, R is, at each occurrence identically or differently, selected from the group consisting of: hydrogen, deuterium, methyl, isopropyl, NO2, SO2CH3, SCF3, C2F5, OC2F5, OCH3, diphenylmethylsilyl, phenyl, methoxyphenyl, p-methylphenyl, 2,6-diisopropylphenyl, biphenyl, polyfluorophenyl, difluoropyridyl, nitrophenyl, dimethylthiazolyl, vinyl substituted by one or more of CN or CF3, acetenyl substituted by one of CN or CF3, dimethylphosphoroso, diphenylphosphoroso, F, CF3, OCF3, SF5, SO2CF3, cyano, isocyano, SCN, OCN, trifluoromethylphenyl, trifluoromethoxyphenyl, bis(trifluoromethyl)phenyl, bis(trifluoromethoxy)phenyl, 4-cyanotetrafluorophenyl, phenyl or biphenyl substituted by one or more of F, CN or CF3, tetrafluoropyridyl, pyrimidinyl, triazinyl, diphenylboryl, oxaboraanthryl and combinations thereof.
According to an embodiment of the present disclosure, in Formula 1, X and Y each are
According to an embodiment of the present disclosure, in Formula 1, R is, at each occurrence identically or differently, selected from the group consisting of the following structures:
wherein “” represents a position where the group R is joined to a dehydrobenzodioxazole ring, a dehydrobenzodithiazole ring or a dehydrobenzodiselenazole in Formula 1.
According to an embodiment of the present disclosure, two R in one compound represented by Formula 1 are the same.
According to an embodiment of the present disclosure, the compound of Formula 1 has a structure represented by Formula 3:
wherein in Formula 3, two Z have the same structure, two R have the same structure or different structures, and Z, X, Y and R are respectively and correspondingly selected from atoms or groups shown in the following table;
wherein the compound having the structure of Formula 3 is selected from the group consisting of the following compounds:
According to an embodiment of the present disclosure, in Formula 2, L is selected from substituted or unsubstituted phenylene, substituted or unsubstituted biphenylene, substituted or unsubstituted terphenylene, substituted or unsubstituted naphthylene, substituted or unsubstituted fluorenylidene, substituted or unsubstituted silafluorenylidene, substituted or unsubstituted carbazolylene, substituted or unsubstituted dibenzofurylene, substituted or unsubstituted dibenzothienylene, substituted or unsubstituted dibenzoselenophenylene, substituted or unsubstituted phenanthrylene, substituted or unsubstituted triphenylenylene, substituted or unsubstituted pyridylene, substituted or unsubstituted spirobifluorenylidene, substituted or unsubstituted anthrylene, substituted or unsubstituted pyrenylene or a combination thereof; preferably, L is selected from substituted or unsubstituted phenylene or substituted or unsubstituted biphenylene; more preferably, L is phenylene or biphenylene.
According to an embodiment of the present disclosure, in Formula 2, R1 is selected from hydrogen, deuterium, halogen, substituted or unsubstituted alkyl having 1 to 20 carbon atoms, substituted or unsubstituted cycloalkyl having 3 to 20 ring carbon atoms, substituted or unsubstituted aryl having 6 to 30 carbon atoms or substituted or unsubstituted heteroaryl having 3 to 30 carbon atoms; preferably, R1 is selected from hydrogen, deuterium, substituted or unsubstituted aryl having 6 to 30 carbon atoms or substituted or unsubstituted heteroaryl having 3 to 30 carbon atoms.
According to an embodiment of the present disclosure, in Formula 2, Ar1 and Ar2 are selected from substituted or unsubstituted aryl having 6 to 20 carbon atoms or substituted or unsubstituted heteroaryl having 3 to 20 carbon atoms; preferably, Ar1 and Ar2 are selected from phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, dibenzothienyl, spirobifluorenyl, pyridyl or pyrimidinyl.
According to an embodiment of the present disclosure, the compound having the structure of Formula 2 is selected from the group consisting of the following compounds:
According to an embodiment of the present disclosure, a display assembly is further disclosed. The display assembly includes the organic electroluminescent device according to any one of the preceding embodiments.
According to another embodiment of the present disclosure, a first organic electroluminescent device is disclosed. The first organic electroluminescent device comprises: a substrate;
a first electrode disposed on the substrate;
a second electrode disposed over the first electrode; and
an organic layer disposed between the first electrode and the second electrode;
wherein the first electrode is a material with high reflectivity or a combination of materials with high reflectivity, and the second electrode is a translucent or transparent material or a combination of translucent or transparent materials;
the organic layer comprises a first organic layer, a second organic layer and a third organic layer;
the first organic layer comprises a first organic material and a second organic material;
the second organic layer is made of the second organic material and has a first thickness;
the third organic layer is a light-emitting layer comprising at least one light-emitting material and at least one host material;
the first organic layer has a conductivity of greater than 1×10−4 S/m and less than 1×10−2 S/m;
an energy level difference between a HOMO energy level of the second organic material and a HOMO energy level of the at least one host material is less than 0.27 eV;
a voltage of the first organic electroluminescent device is not higher than 110% of a voltage of a second organic electroluminescent device at the same current density, wherein the second organic electroluminescent device has the same device structure as the first organic electroluminescent device except the following differences:
(1) the first organic layer comprises the first organic material and a third organic material, wherein the third organic material is different from the second organic material;
(2) the second organic layer is made of the third organic material;
(3) a fourth organic layer is comprised between the second organic layer and the third organic layer, wherein the fourth organic layer is made of the second organic material;
wherein a total thickness of the second organic layer and the fourth organic layer in the second organic electroluminescent device is 90% to 110% of the first thickness in the first organic electroluminescent device.
According to an embodiment of the present disclosure, the voltage of the first organic electroluminescent device is not higher than the voltage of the second organic electroluminescent device at the same current density.
According to an embodiment of the present disclosure, the HOMO energy level of the second organic material in the first organic electroluminescent device is less than a HOMO energy level of the third organic material in the second organic electroluminescent device.
According to an embodiment of the present disclosure, the HOMO energy level of the second organic material in the first organic electroluminescent device is less than −5.25 eV.
According to an embodiment of the present disclosure, a LUMO energy level of the first organic material in the first organic electroluminescent device is less than −5.1 eV.
According to an embodiment of the present disclosure, an energy level difference between the HOMO energy level of the second organic material and the LUMO energy level of the first organic material is less than 0.23 eV.
According to an embodiment of the present disclosure, the energy level difference between the HOMO energy level of the second organic material and the LUMO energy level of the first organic material is less than 0.2 eV.
According to an embodiment of the present disclosure, the energy level difference between the HOMO energy level of the second organic material and the LUMO energy level of the first organic material is less than or equal to 0.1 eV.
According to an embodiment of the present disclosure, the second organic layer in the first organic electroluminescent device has a thickness of greater than 80 nm.
According to an embodiment of the present disclosure, the second organic layer in the first organic electroluminescent device has a thickness of greater than 125 nm.
According to an embodiment of the present disclosure, the second organic layer in the first organic electroluminescent device has a thickness of greater than or equal to 100 nm.
According to an embodiment of the present disclosure, the second organic layer in the first organic electroluminescent device has a thickness of greater than or equal to 120 nm.
According to an embodiment of the present disclosure, the second organic layer in the first organic electroluminescent device has a thickness of greater than 150 nm.
According to an embodiment of the present disclosure, a display assembly is further disclosed. The display assembly includes the first organic electroluminescent device according to any one of the preceding embodiments.
The structural diagram of a typical top-emitting OLED device is shown in
In the present disclosure, the electrochemical properties of all compounds are measured through cyclic voltammetry (CV). The test is conducted using an electrochemical workstation modelled CorrTest CS120 produced by Wuhan Corrtest Instruments Corp., Ltd and using a three-electrode working system where: a platinum disk electrode serves as a working electrode, a Ag/AgNO3 electrode serves as a reference electrode, and a platinum wire electrode serves as an auxiliary electrode. Anhydrous DCM is used as a solvent, 0.1 mol/L tetrabutylammonium hexafluorophosphate is used as a supporting electrolyte, a compound to be tested is prepared into a solution of 10−3 mol/L, and nitrogen is introduced into the solution for 10 min for oxygen removal before the test. The parameters of the instrument are set as follows: a scan rate of 100 mV/s, a potential interval of 0.5 mV and a test window of −1 V to 1 V. The HOMO energy levels of some hole transporting materials (HTMs) and some host materials measured by the above test method are listed in Table 1, and the LUMO energy levels of some PD materials measured by the above test method are listed in Table 2.
Compound HT1, H-176, Compound 70, Compound 72, Compound 56, Compound HT, Compound RH1, Compound RH2 and Compound BH have the following structural formulas:
Though matching the energy levels of the HTM and the PD material is the first step to ensure effective hole injection, the doping ratio of the PD material also affects the hole injection ability. The hole injection ability of the hole injection layer can be quantitatively analyzed by measuring the conductivity of the hole injection layer. Generally, within a certain range, the higher the doping ratio of the PD material, the higher the conductivity, that is, the stronger the hole injection ability. If the conductivity is too low, insufficient hole injection will lead to an increase in voltage, and the recombination region in the EML will move towards the anode, which may also lead to a decrease in lifetime. On the contrary, if the conductivity is too high, excessive hole injection will lead to a decrease in efficiency, which is obvious especially in an electron-deficient system. Moreover, in display applications, too high a conductivity of the HIL will also bring about the problem of lateral crosstalk between pixels. Therefore, the conductivity of the HIL should be within a certain range, for example, 1×10−4 to 1×10−2 S/m, preferably, 2×10−4 to 8×10−3 S/m.
The conductivity is measured by the following method: the to-be-tested samples of the HTM and the PD material are co-deposited through evaporation on a test substrate pre-prepared with an aluminum electrode at a certain doping ratio (the PD material in Table 2 is doped with the HTM in Table 1 at a weight ratio of 3%, 2% and 1%) at a vacuum degree of 10−6 torr to form a to-be-tested region with a thickness of 100 nm, a length of 6 mm and a width of 1 mm, a voltage is applied to the electrode and a current is measured to obtain a resistance value of the region, and then the conductivity of the film layer is calculated according to the Ohm's law and geometric dimensions. It is to be noted that even if the HTM and the PD material are kept unchanged, that is, their energy level difference remains unchanged, the hole injection capability can be adjusted to a certain extent by adjusting the doping ratio. On the other hand, if the difference between the energy levels of the HTM and the PD material is too large, the hole injection ability is adjusted by the doping ratio to a very limited extent. The measurement results of the conductivities of some HTMs with different proportions of PD measured by the above conductivity test method are listed in Table 3.
Hereinafter, the present disclosure is described in more detail with reference to the following examples. The compounds used in the following examples can be easily obtained by those skilled in the art, so synthesis methods of these compounds will not be repeated here. For example, the synthesis methods are available from the Chinese patent application CN112745333A, which is incorporated by reference in its entirety. Apparently, the following examples are only for the purpose of illustration and not intended to limit the scope of the present disclosure. Based on the following examples, those skilled in the art can obtain other examples of the present disclosure by conducting improvements on these examples.
Firstly, a 0.7 mm thick glass substrate was pre-patterned with indium tin oxide (ITO) 75 Å/Ag 1500 Å/ITO 150 Å for use as an anode 201, where 150 Å ITO deposited on Ag had a hole injection function. Then, the substrate was dried in a glovebox to remove moisture, mounted on a holder and transferred into a vacuum chamber. Organic layers specified below were sequentially deposited through vacuum thermal evaporation on the anode layer at a rate of 0.01-10 Å/s and at a vacuum degree of about 10−6 torr. Compound H-176 and Compound 70 (98:2, 100 Å) were co-deposited for use as a hole injection layer (HIL) 202. Compound H-176 (1900 Å) was deposited for use as a hole transporting layer (HTL) 203 and a microcavity length adjustment layer. Compound RH1 and Compound RD (98:2, 400 Å) were co-deposited on the HTL for use as an emissive layer (EML) 204. Compound HB (50 Å) was deposited for use as a hole blocking layer (HBL) 205. Compound ET and Liq (40:60, 350 Å) were co-deposited for use as an electron transporting layer (ETL) 206. A metal Yb (10 Å) was deposited for use as an electron injection layer (EIL) 207. Metals Ag and Mg (9:1, 140 Å) were co-deposited for use as a cathode 208. Finally, Material CPL (650 Å) was deposited for use as a capping layer 209 (the CPL material has a refractive index of about 1.68 at 620 nm, and the refractive index is obtained by testing a 30 nm thick CPL material deposited on a silicon wafer using an ES01 ellipsometer from BEIJING ELLITOP). The device was transferred back to the glovebox and encapsulated with a glass lid to complete the device.
This comparative example adopted the same preparation method as Example 1, except that Compound HT1 and Compound 70 (98:2, 100 Å) were co-deposited for use as a hole injection layer (HIL) 102, Compound HT1 (1200 Å) was deposited for use as a hole transporting layer (HTL) 103, and Compound H-176 (700 Å) was deposited for use as an electron blocking layer (EBL) 104 and a microcavity length adjustment layer.
This comparative example adopted the same preparation method as Example 1, except that Compound H-176 and Compound HT (98:2, 100 Å) were co-deposited for use as a hole injection layer (HIL) 202.
Detailed structures and thicknesses of part of layers of the devices are shown in Table 5. A layer using more than one material is obtained by doping different compounds at their weight ratio as recorded.
Compounds RD, HB, ET and Liq have the following structural formulas:
The device performance of Example 1 and Comparative Examples 1-1 and 1-2 is shown in Table 6. The color coordinates, voltage and current efficiency were measured at a current density of 10 mA/cm2, and the device lifetime (LT97) was the measured time taken for the device to decay to 97% of its initial brightness at 80 mA/cm2.
The device in Example 1 uses Compound 70 with a LUMO energy level of −5.17 eV as the conductive p-type doping material which is doped into Compound H-176 with a HOMO energy level of −5.27 eV for use as the material of the hole injection layer. It can be seen from Table 4 that the energy level difference between the HOMO energy level of the HTM and the LUMO energy level of the PD is 0.1 eV. It can be seen from Table 3 that at a doping proportion of 2%, the conductivity of the hole injection layer is 4.6×10−4 S/m, which is greater than 1×10−4 S/m, indicating good hole injection from the anode to the organic layer. It is to be noted that it can be seen from Table 3 that if the doping proportion of Compound 70 is reduced to, for example, 1%, the conductivity can be reduced; on the contrary, if the doping proportion of Compound 70 is increased to 3%, the conductivity can be improved. Comparative Example 1-1 is a red light device structure commonly used in the industry, and it can be seen from the device data that the device has relatively high red light device performance in the industry. Compared with Comparative Example 1-1, Example 1 has slightly improved efficiency, a slightly prolonged lifetime and a voltage reduced by 0.4 V on the premise of ensuring its color. As can be seen from Table 3, the HIL used in Comparative Example 1-1 has a conductivity of 40.4×10−4 S/m and has better hole injection than that in Example 1. However, Comparative Example 1-1 has a higher voltage than Example 1. As can be seen from Table 4, the energy level difference between the HOMO energy level of the HTM (H-176) in the HIL in Example 1 and the HOMO energy level of the host material RH1 for red light is 0.12 eV, while the energy level difference between the HOMO energy level of the HTM (HT1) in the HIL in Comparative Example 1-1 and the HOMO energy level of RH1 is 0.30 eV. This indicates that a decrease of the energy level difference between the HOMO energy levels of the HTM and the host material in the emissive layer has a decisive effect on the voltage of the device; secondly, a decrease of the number of function layers can also reduce the number of defects caused by an interface, which is also helpful for reducing the voltage.
The hole injection layer in Comparative Example 1-2 uses Compound HT for p-doping and H-176 as the HTM. It can be seen from Table 3 that the conductivity of the hole injection layer is 1×10−4 S/m, which is lower than that in Example 1 so that it can be seen that the hole injection layer has a worse hole injection ability than the HIL in Example 1. Similarly, the hole injection ability can be embodied by the energy level difference. Comparative Example 1-2 uses Compound HT with a LUMO energy level of −5.04 eV as the conductive p-type doping material which is doped into Compound H-176 with a HOMO energy level of −5.27 eV for use as the material of the hole injection layer. It can be seen from Table 4 that the energy level difference between the HOMO energy level of the HTM and the LUMO energy level of the PD is 0.23 eV, which is higher than 0.1 eV in Example 1 so that the hole injection layer has a worse hole injection ability than the HIL in Example 1 at the same doping ratio. Therefore, Comparative Example 1-2 has a voltage as high as 8.5 V and a lifetime reduced by 45% though it can maintain basically the same current efficiency as Example 1. Here, the energy level difference between the HOMO energy levels of the HTM (H-176) in Comparative Example 1-2 and the host material RH1 for red light is 0.12 eV, which is the same as that in Example 1, and the difference only lies in that under the same doping concentration, the hole injection layers have different conductivities.
As can be seen from the comparison of the above example and comparative examples, the energy level difference between the HOMO energy levels of the HTM and the host material in the emissive layer and the conductivity of the hole injection layer both have important effects on the device performance, especially the voltage and lifetime of the device. Example 1 which satisfies both the conductivity and the energy level difference in the present application can further reduce the device voltage and prolong the device lifetime when the CIE and the efficiency are basically unchanged.
This example adopted the same preparation method as Example 1, except that Compound RH2 and Compound RD (98:2, 400 Å) were co-deposited for use as an emissive layer (EML) 204.
This comparative example adopted the same preparation method as Comparative Example 1-1, except that Compound RH2 and Compound RD (98:2, 400 Å) were co-deposited for use as an emissive layer (EML) 105.
This comparative example adopted the same preparation method as Example 2, except that Compound H-176 and Compound HT (98:2, 100 Å) were co-deposited for use as a hole injection layer (HIL) 202.
Detailed structures and thicknesses of part of layers of the devices are shown in Table 7. A layer using more than one material is obtained by doping different compounds at their weight ratio as recorded.
The device performance of Example 2 and Comparative Examples 2-1 and 2-2 is shown in Table 8. The color coordinates, voltage and current efficiency were measured at a current density of 10 mA/cm2, and the device lifetime (LT97) was the measured time taken for the device to decay to 97% of its initial brightness at 80 mA/cm2.
The hole injection layer of the device in Example 2 is the same as that in Example 1 and has good hole injection from the anode to the organic layer. Comparative Example 2-1 is a red light device structure commonly used in the industry, and it can be seen from the device data that the device has relatively high red light device performance in the industry. Compared with Comparative Example 2-1, Example 2 has a voltage reduced by 0.5 V, a lifetime prolonged by 27% and comparable device efficiency on the premise of ensuring its color. This is because the energy level difference between the HOMO energy levels of the HTM (H-176) in Example 2 and the host material RH2 for red light has an absolute value of 0.09 eV, while the difference is 0.27 eV in Comparative Example 2-1. A smaller potential barrier results in a decrease in voltage and also ensures that holes can be effectively transported to the emissive layer.
Similar to that in Comparative Example 1-2, the hole injection layer in Comparative Example 2-2 uses Compound HT for p-doping and H-176 as the HTM. It can be seen from Table 3 that the conductivity of the hole injection layer is 1×10−4 S/m, which is lower than that in Example 2 so that it can be seen that the hole injection layer has a worse hole injection ability than the HIL in Example 2. Similarly, the hole injection ability can be embodied by the energy level difference. Comparative Example 2-2 uses Compound HT with a LUMO energy level of −5.04 eV as the conductive p-type doping material which is doped into Compound H-176 with a HOMO energy level of −5.27 eV for use as the material of the hole injection layer. It can be seen from Table 4 that the energy level difference between the HOMO energy level of the HTM and the LUMO energy level of the PD is 0.23 eV, which is higher than 0.1 eV in Example 2. Therefore, Comparative Example 2-2 has a voltage as high as 7.3 V and a lifetime reduced by 44% relative to the lifetime in Example 2 though it can maintain basically the same current efficiency as Example 2. Here, the energy level difference between the HOMO energy levels of the HTM (H-176) in Comparative Example 2-2 and the host material RH2 for red light has an absolute value of 0.09 eV, which is the same as that in Example 2, and the difference only lies in that the hole injection layers have different conductivities.
As can be seen from the comparison of the above example and comparative examples, the energy level difference between the HOMO energy levels of the HTM and the host material in the emissive layer and the conductivity of the hole injection layer both have important effects on the device performance, especially the voltage and lifetime of the device. Example 2 which satisfies both the conductivity and the energy level difference in the present application can further reduce the device voltage and prolong the device lifetime when the CIE and the efficiency are basically unchanged.
Firstly, a 0.7 mm thick glass substrate was pre-patterned with indium tin oxide (ITO) 75 Å/Ag 1500 Å/ITO 150 Å for use as an anode 201, where 150 Å ITO deposited on Ag had a hole injection function. Then, the substrate was dried in a glovebox to remove moisture, mounted on a holder and transferred into a vacuum chamber. Organic layers specified below were sequentially deposited through vacuum thermal evaporation on the anode layer at a rate of 0.01-10 Å/s and at a vacuum degree of about 10−6 torr. Compound H-176 and Compound 70 (98:2, 100 Å) were co-deposited for use as a hole injection layer (HIL) 202. Compound H-176 (1210 Å) was deposited for use as a hole transporting layer (HTL) 203 and a microcavity length adjustment layer. Compound BH and Compound BD (98:2, 200 Å) were co-deposited on the HTL for use as an emissive layer (EML) 204. Compound HB2 (50 Å) was deposited for use as a hole blocking layer (HBL) 205. Compound ET and Liq (40:60, 300 Å) were co-deposited for use as an electron transporting layer (ETL) 206. A metal Yb (10 Å) was deposited for use as an electron injection layer (EIL) 207. Metals Ag and Mg (9:1, 140 Å) were co-deposited for use as a cathode 208. Finally, Material CPL (650 Å) was deposited for use as a capping layer 209 (the CPL material has a refractive index of about 1.68 at 620 nm, and a 30 nm thick CPL material deposited on a silicon wafer was tested using an ES01 ellipsometer from BEIJING ELLITOP to obtain the refractive index). The device was transferred back to the glovebox and encapsulated with a glass lid to complete the device.
This example adopted the same preparation method as Example 3-1, except that Compound H-176 and Compound 72 (96:4, 100 Å) were co-deposited for use as a hole injection layer (HIL), and Compound H-176 (1210 Å) was deposited for use as a hole transporting layer (HTL) and a microcavity length adjustment layer.
This comparative example adopted the same preparation method as Example 3-1, except that Compound HT1 and Compound 70 (98:2, 100 Å) were co-deposited for use as a hole injection layer (HIL) 102, Compound HT1 (1160 Å) was deposited for use as a hole transporting layer (HTL) and a microcavity length adjustment layer, and Compound H-176 (50 Å) was deposited for use as an electron blocking layer (EBL) 104.
This comparative example adopted the same preparation method as Example 3-1, except that Compound H-176 and Compound HT (98:2, 100 Å) were co-deposited for use as a hole injection layer (HIL).
This comparative example adopted the same preparation method as Example 3-2, except that Compound HT1 and Compound 72 (98:2, 100 Å) were co-deposited for use as a hole injection layer (HIL), Compound HT1 (1160 Å) was deposited for use as a hole transporting layer (HTL) and a microcavity length adjustment layer, and Compound H-176 (50 Å) was deposited for use as an electron blocking layer (EBL).
Detailed structures and thicknesses of part of layers of the devices are shown in Table 9. A layer using more than one material is obtained by doping different compounds at their weight ratio as recorded.
The structures of the new materials used in the devices are shown as follows:
It is worth noting that, as is well-known in the industry, for the efficiency of a blue light device in a display panel, the industry generally needs to consider the color factor of the blue light device, that is, adopts CE/CIEy.
The hole injection layer of the device in Example 3-1 is the same as those in Examples 1 and 2 and has good hole injection from the anode to the organic layer. Comparative Example 3-1 is a blue light device structure commonly used in the industry. Compared with Comparative Example 3-1, Example 3-1 has a lifetime increased 5 times and efficiency CE/CIEy improved by 9% from 157 to 171 on the premise of ensuring the same color, and Example 3-1 has better overall performance than Comparative Example 3-1 although the voltage of Example 3-1 is increased by 0.2 V. It is to be noted that the energy level difference between the HOMO energy levels of the HTM (H-176) in Example 3-1 and the host material BH for blue light has an absolute value of 0.26 eV, while the difference is 0.44 eV in Comparative Example 3-1. In Comparative Example 3-1, holes will face a relatively high potential barrier if they directly travel from the HTL to the EML, so the commonly used commercially available device structure is used, where the EBL is added to the device for barrier buffering. The voltage of a device without the EBL is at least 0.5 V higher than the voltage of Comparative Example 3-1, and the device has the greatly reduced efficiency and lifetime. With the greatly improved efficiency and lifetime of the device, Example 3-1 has a voltage comparable to that of Comparative Example 3-1 and increased by only 0.2 V, indicating that the device in Example 3-1 can ensure that holes are effectively transported to the emissive layer.
Similar to those in Comparative Examples 1-2 and 2-2, the hole injection layer in Comparative Example 3-2 uses Compound HT for p-doping and H-176 as the HTM. It can be seen from Table 3 that the conductivity of the hole injection layer is 1×10−4 S/m, which is lower than that in Example 3-1 so that it can be seen that the hole injection layer has a worse hole injection ability than the HIL in Example 3-1. Similarly, the hole injection ability can be embodied by the energy level difference. Comparative Example 3-2 uses Compound HT with a LUMO energy level of −5.04 eV as the conductive p-type doping material which is doped into Compound H-176 with a HOMO energy level of −5.27 eV for use as the material of the hole injection layer. It can be seen from Table 4 that the energy level difference between the HOMO energy level of the HTM and the LUMO energy level of the PD is 0.23 eV, which is higher than 0.1 eV in Example 3-1. Therefore, the voltage of Comparative Example 3-2 is as high as 6.5 V, its efficiency CE/CIEy is only 163, and its lifetime is only 2 h. Compared with Comparative Example 3-2, Example 3-1 has a voltage reduced by 2.4 V, efficiency CE/CIEy improved by 5% and a lifetime increased 25 times. Here, the energy level difference between the HOMO energy levels of the HTM (H-176) in Comparative Example 3-2 and the host material BH for blue light has an absolute value of 0.26 eV, which is the same as that in Example 3-1, and the difference only lies in that the hole injection layers have different conductivities.
On the basis of Example 3-1, Example 3-2 mainly replaces the PD material in the HIL with Compound 72 and can achieve the same excellent device performance as Example 3-1 in the same blue light device. Similar to the comparison between Example 3-1 and Comparative Example 3-1, Example 3-2 has great advantages in terms of efficiency CE/CIEy and lifetime compared with Comparative Example 3-3. Comparative Example 3-3 also adopts the commonly used commercially available device structure. With the greatly improved efficiency and lifetime of the device, Example 3-2 has a voltage comparable to that of Comparative Example 3-3 and increased by only 0.2 V, indicating that the device in Example 3-2 can ensure that holes are effectively transported to the emissive layer.
As can be seen from the comparison of the above examples and comparative examples, the energy level difference between the HOMO energy levels of the HTM and the host material in the emissive layer and the conductivity of the hole injection layer both have important effects on the device performance, especially the voltage, efficiency and lifetime of the device. Examples 3-1 and 3-2 which satisfy both the conductivity and the energy level difference in the present application can further improve the efficiency and prolong the device lifetime when the CIE are basically unchanged.
To sum up, the organic electroluminescent device with top emission in the present application achieves good device performance, especially a reduced device voltage and a prolonged lifetime, by matching and optimizing the electrical properties of organic function layers, such as the conductivity of the HIL and the energy level difference between the HTM and the host material in the emissive layer.
It should be understood that various embodiments described herein are merely examples and not intended to limit the scope of the present disclosure. Therefore, it is apparent to the persons skilled in the art that the present disclosure as claimed may include variations from specific embodiments and preferred embodiments described herein. Many of materials and structures described herein may be substituted with other materials and structures without departing from the spirit of the present disclosure. It should be understood that various theories as to why the present disclosure works are not intended to be limitative.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202110592096.5 | May 2021 | CN | national |
| 202210355382.4 | Apr 2022 | CN | national |
