Tandem organic electroluminescent device

Abstract

The present invention relates to an organic electroluminescent device in the technical field of electro-optical display devices, and provides an organic electroluminescent device having a tandem structure formed by adopting a specific connection layer arrangement between adjacent light-emitting units in the device. The device includes an anode, a cathode, at least two electroluminescent units arranged between the anode and the cathode, and a connection layer arranged between adjacent electroluminescent units, the connection layer being a multi-layer structure including an n-type doped layer, a p-type doped layer, and a separator made of an electron transport material arranged therebetween. The separator made of such an electron transport material can effectively prevent the n-type dopant in the n-type doped layer from diffusing into the other p-type doped layer, effectively improving the problems of increased driving voltage and aging of the device caused by the diffusion of the n-type dopant, and significantly improving the life and stability of the tandem organic electroluminescent device.

Description

[Technical Field]

[0001] The present invention relates to an organic electroluminescent device in the field of electro-optical displays, and more particularly to an organic electroluminescent device employing a specific connecting layer arrangement between adjacent light-emitting units within the device to form a tandem structure. [Background technology]

[0002] Organic light-emitting diodes (OLEDs), which are organic light-emitting devices, mainly consist of a cathode, an anode, and an emitting unit disposed between the two electrodes, with the emitting unit primarily made of organic semiconductor materials. As a field-injection type light-emitting device, when voltage is applied to the electrodes of the OLED device, holes and the anode inject into the organic functional layer, electrons are injected from the cathode into the organic functional layer, and the electrons and holes recombine in the emitting layer to form excitons, ultimately emitting light. OLED devices have many advantages, such as low power consumption, wide viewing angles, and foldability, making them suitable for a wide range of applications in the fields of solid-state display and lighting technology.

[0003] Tandem-structured OLED devices have attracted widespread attention in recent years. Their light-emitting principle is similar to that of conventional single-layer OLED devices. However, tandem OLED devices differ in that they consist of multiple light-emitting units connected in series via connecting layers that function like electrodes. This allows them to generate carrier pairs under external electric field driving and then separate the generated carriers for injection into adjacent light-emitting units. This tandem device structure allows each light-emitting unit to generate a photon for each electron or hole injection, achieving radiative emission. Therefore, a tandem OLED device with N light-emitting units can achieve approximately N times the current efficiency of a single-layer OLED device. To achieve the same brightness, the current density required for a tandem OLED device is significantly reduced, thereby improving the efficiency roll-off and lifetime issues of OLED devices.

[0004] Currently, the interconnect layer structure commonly used in typical tandem OLED devices is an n-doped layer / p-doped layer. The small energy difference between the LUMO level of the n-doped layer and the HOMO level of the p-doped layer allows for efficient carrier generation at low drive voltages. The dopants in the n-doped layer are typically alkali or alkaline earth metals with low work functions (WF < 3.0 eV), such as lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), and calcium (Ca). However, these alkali and alkaline earth n-dopants tend to diffuse into the p-doped layer under external electric fields, resulting in increased drive voltages during device operation, significantly reduced device life, and significant impacts on device efficiency and stability.

[0005] Patent Document 1: Kodak Company's Patent CN100544020A proposes a tandem OLED device in which an intermediate connecting element disposed between adjacent electroluminescent units is designed, and this connecting element includes an n-type doped organic layer, a p-doped organic layer, and an interface layer, where the interface layer mainly functions to prevent possible interdiffusion between the n-type dopant organic layer and the electron-accepting layer material. In this patent, the interfacial layer is a metal compound or metal, and specifically, the interfacial layer can be selected from high work function metals including Ti, Zr, Ti, Nb, Ta, Cr, Mo, W, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Al, In, Sn, or alloys thereof, and stoichiometric or non-stoichiometric oxides, stoichiometric or non-stoichiometric sulfides, stoichiometric or non-stoichiometric tellurides, stoichiometric or non-stoichiometric nitrides, stoichiometric or non-stoichiometric carbides of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, tungsten, manganese, iron, ruthenium, rhodium, iridium, nickel, palladium, platinum, copper, silicon, germanium, or combinations thereof. For this reason, the above connecting layers are all made of inorganic materials, and the deposition temperature is generally high, and the thickness must be precisely controlled to ensure high transmittance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Chinese Patent 100544020A DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a new connecting layer for a tandem OLED device to solve the problems existing in the prior art. Specifically, the connecting layer in a conventional tandem OLED device is an n-type doped layer / p-type doped layer, and during device operation, the metallic n-type dopant is likely to diffuse into the p-type doped layer and the adjacent light-emitting layer, resulting in an increase in the device's driving voltage and a decrease in luminous efficiency.

[0008] A separator structure consisting of a nitrogen-containing heterocyclic electron transport material with excellent electron transport properties is introduced between the n-type doped layer and the p-type doped layer of a tandem OLED device. Both of these materials are organic semiconductor materials, have low deposition temperatures, and have high transmittance in the visible light region. Such electron transport materials have strong interactions with metal-based n-type dopants such as alkali metals, alkaline earth metals, and partial transition metals, which helps to suppress the diffusion of such metal-based n-type dopants into the p-type doped layer, and further effectively improves the increase in driving voltage during device operation and extends the device's lifespan.

[0009] Specifically, the present invention provides a tandem organic electroluminescent device comprising an anode, a cathode, at least two electroluminescent units disposed between the anode and the cathode, and a connecting layer disposed between adjacent electroluminescent units, each of the electroluminescent units comprising at least one electron transport layer and one organic light-emitting layer, wherein the connecting layer has a multi-layer structure including an n-type doped layer, a p-type doped layer, and a separator therebetween.

[0010] The p-type doped layer is composed of a p-type doping host material using a hole-transporting organic substance and a p-type dopant. In the p-type doped layer, the p-type doping host material uses a hole-transporting organic substance, and specifically can be selected from the following compounds:

[0011] [ka] TIFF0007752434000002.tif185166

[0012] The p-type dopants used in the p-type doped layer mainly include MoO3, WO3, V2O5, MoO2, and Co3O4, and the organic semiconductor materials with strong electron-withdrawing ability include CN6-CP, DDQ, HATCN, and C 60 F 36 , F4TCNQ, F2HCNQ, F6TCNNQ, TECTFCNBN or a mixture of several metal oxides with high work function, and the molecular structure of the p-type dopant is specifically as follows:

[0013] [ka]

[0014] The doping ratio of the p-type dopant in the p-type doped layer is 0.2 wt% to 30 wt%, preferably 0.5 wt% to 10 wt%.

[0015] The n-type doped layer is composed of an n-type doping host material using an electron transporting organic material and an n-type dopant using an alkali metal, alkaline earth metal or transition metal.

[0016] The n-type dopant is an alkali metal, alkaline earth metal, or transition metal, and is preferably selected from one or a mixture of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, gold, silver, copper, iron, nickel, platinum, palladium, ruthenium, and ytterbium, and most preferably selected from lithium, silver, and cesium. In the n-type doped layer, the n-type doping host is an electron transporting organic material, which can be specifically selected from the following compounds:

[0017] [ka] TIFF0007752434000005.tif248166TIFF0007752434000006.tif242166TIFF0007752434000007.tif45166

[0018] The separator is an organic material having electron transport properties different from those of the n-type doping host material. In this specification, the separator is mainly made of an electron transport material having excellent electron transport properties and a nitrogen-containing heterocycle in its molecular structure, and has a strong interaction with various metal n-type dopants. Such an electron transport material has a structure represented by the following formula (1) or (2):

[0019] [ka] In formula (1), the bridging group Q is one selected from the following substituted or unsubstituted groups, which means that it is substituted with one or a combination of two selected from the group consisting of deuterium, tritium, cyano group, halogen, C1 to C10 alkyl group, C3 to C10 cycloalkyl group, silicon group, C6 to C30 arylamino group, C6 to C30 aryl group, and C2 to C30 heteroaryl group, where is the bonding position between R1 and the bridging group Q, and is the bonding position between R2 and the bridging group Q.

[0020] [ka] TIFF0007752434000010.tif102166

[0021] In formula (1), R1 and R2 are each independently one selected from substituted or unsubstituted C3 to C60 heteroaryl groups, the heteroaryl group containing at least one nitrogen atom, and the substitution in the substituted heteroaryl group means substitution with one or a combination of two selected from deuterium, tritium, cyano, halogen, C1 to C10 alkyl, C3 to C10 cycloalkyl, silicon, C6 to C30 arylamino, C6 to C30 aryl, and C2 to C30 heteroaryl groups, and these substituents may or may not independently bond to the heteroaromatic ring to which they are linked to form a ring.

[0022] Preferably, R1 and R2 each independently represent a substituted or unsubstituted pyridyl group, pyrimidyl group, triazinyl group, quinolinyl group, isoquinolinyl group, quinoxalinyl group, quinazolinyl group, benzimidazolyl group, naphthimidazolyl group, phenanthrolyl group, benzothiazolyl group, benzoxazolyl group, phenazine, dibenzophenazine, oxadiazolyl group, thiadiazolyl group, triazazolyl group, oxadiazolyl group, an and a thiaquinonyl group, and the substitution in the substituted or unsubstituted R1 and R2 means substitution with one or a combination of two selected from halogen, a C1-C10 alkyl group, a C3-C10 cycloalkyl group, a C6-C30 arylamino group, a C6-C30 aryl group, and a C2-C30 heteroaryl group, and these substituents may or may not independently form a ring with the aromatic ring or heteroaromatic ring to which they are linked.

[0023] In formula (2), when n is 2, 3 or 4, Q is one selected from the following substituted or unsubstituted groups:

[0024] [ka]

[0025] In formula (2), R1 and R2 are each independently one selected from the group consisting of a C1-C30 aliphatic hydrocarbyloxy group, a C2-C30 aliphatic hydrocarbylamino group, a C3-C20 cyclic aliphatic hydrocarbylamino group, a substituted or unsubstituted C6-C30 arylamino group, a substituted or unsubstituted C3-C30 heteroarylamino group, a substituted or unsubstituted C6-C60 aryl group, and a substituted or unsubstituted C3-C60 heteroaryl group. When R1 and R2 each have a substituent, the substituent is one or a combination of two selected from the group consisting of deuterium, halogen, a C1-C30 linear alkyl group, a C3-C30 cycloalkyl group, a cyano group, a nitro group, a C1-C6 alkoxy group, a C1-C6 thioalkoxy group, a C6-C30 aryl group, and a C3-C60 heteroaryl group. Preferably, R1 and R2 in formula (1) are each independently one selected from the group consisting of substituted or unsubstituted groups:

[0026] [ka] TIFF0007752434000013.tif204166

[0027] The R1 and R2 are each independently one selected from the following substituted or unsubstituted groups:

[0028] Methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, 2-methylbutyl group, n-pentyl group, sec-pentyl group, cyclopentyl group, neopentyl group, n-hexyl group, cyclohexyl group, neohexyl group, n-heptyl group, cycloheptyl group, n-octyl group, cyclooctyl group, 2-ethylhexyl group, trifluoromethyl group, pentafluoroethyl group, 2,2,2-trifluoroethyl group, dimethylamino group, cyclopropyleneimino group, Tetrahydropyrrolyl group, piperidyl group, cyclohexyleneimino group, cycloheptyleneimino group, cyclooctylideneimino group, methoxy group, ethoxy group, propoxy group, butoxy group, phenyl group, naphthyl group, anthracenyl group, benzanthracenyl group, phenanthrenyl group, triphenylenyl group, pyrenyl group, chrysenyl group, perylenyl group, fluoranthenyl group, naphthacenyl group, pentaphenyl group, benzopyrenyl group, biphenyl group, diphenyl group, terphenyl group, triphenyl group, quaterphenyl group, fluoranthenyl group, naphthacenyl group, pentaphenyl group, benzopyrenyl group, biphenyl group, diphenyl group, terphenyl group, triphenyl group, quaterphenyl group, fluoranthrenyl group, an indenyl group, a spirobifluorenyl group, a dihydrophenanthrenyl group, a dihydropyrenyl group, a tetrahydropyrenyl group, a cis- or trans-indenofluorenyl group, a triaindenyl group, an isotriaindenyl group, a spirotriaindenyl group, a spiroisotrindenyl group, a furanyl group, a benzofuranyl group, an isobenzofuranyl group, a dibenzofuranyl group, a thienyl group, a benzothienyl group, an isobenzothienyl group, a dibenzothienyl group, a pyrrolyl group, an isoindolinyl group, a carbazolyl group, a tert-butylcarbazolyl group, Indenocarbazolyl group, pyridinyl group, quinolinyl group, isoquinolinyl group, acridinyl group, phenanthrenyl group, phenylsulfhydryl group, phenylsulfonyl group, phenyl group, diphenylphosphinoxyl group, naphthylsulfhydryl group, naphthylsulfonyl group, naphthyl group, dinaphthylphosphinoxyl group, anthracenylsulfhydryl group, anthracenylsulfonyl group, anthracenyl group, dianthracenylphosphinoxyl group, benzo-5,6-quinolinyl group, benzo-6,7-quinolinyl group, benzo-7,8-quinolinyl group, pyrazolyl group, indazolyl group, imidazolyl group, benzimidazolyl group, naphthimidazolyl group, phenanthroiimidazolyl group, pyridimidazolyl group, pyrazinoimidazolyl group, quinoxanoimidazolyl group, oxazolyl group, benzoxazolyl group, naphthoxazolyl group, anthraxazolyl group, 1,2-thiazolyl group, 1,3-thiazolyl group, benzothiazolyl group, pyridazinyl group, benzopyridazinyl group, pyrimidinyl group, benzopyrimidinyl group, quinoxalinyl group, 1,5-diazaanthracenyl group, 2,7-diazapyrenyl group, 2,3-diazapyrenyl group, 1,6-diazapyrenyl group, 1,8-diazapyrenyl group, 4,5-diaza Pyrenyl group, 4,5,9,10-tetraazadinylperylenyl group, pyrazinyl group, phenazinyl group, phenothiazinyl group, naphthyridinyl group, azacarbazolyl group, benzocarbolinyl group, phenanthronyl group, 1,2,3-triazolyl group, 1,2,4-triazolyl group, benzotriazolyl group, 1,2,3-oxadiazolyl group, 1,2,3-thiadiazolyl group, 1,2,4-thiadiazolyl group, 1,2,5-thiadiazolyl group, 1,3,4-thiadiazolyl group, 1,3,5-triazinyl group, 1,2,4-triazinyl group, 1,2,3-triazinyl group, tetrazolyl group, 1,2,4,5-tetrazinyl group, 1,2,3,4-tetrazinyl group, 1,2,3,5 -One of a tetrazinyl group, a purinyl group, a pteridinyl group, an indolizinyl group, a benzothiadiazolyl group, a 1,5,7-triazabicyclo[4.4.0]dec-5-enyl group, and a 4-methoxyphenyl group, or a combination of two or more of these.

[0029] Preferably, the bridging group Q in formula (1) is one selected from the following groups:

[0030] [ka]

[0031] It is preferable that R1 and R2 are each independently one selected from the following substituted or unsubstituted groups:

[0032] [ka]

[0033] The bridging group Q in formula (2) is preferably one selected from the following groups:

[0034] [ka] TIFF0007752434000017.tif147166

[0035] It is preferable that R1 and R2 are each independently one selected from the following substituted or unsubstituted groups:

[0036] [ka]

[0037] In the organic electroluminescent device of the present invention, the electron transporting organic material used in the separator is most preferably at least one selected from the following specific compounds.

[0038] [ka] TIFF0007752434000020.tif235166TIFF0007752434000021.tif235166TIFF00077524340000 22.tif229166TIFF0007752434000023.tif216166TIFF0007752434000024.tif216166TIFF000 7752434000025.tif242166TIFF0007752434000026.tif223166TIFF0007752434000027.tif2 35166TIFF0007752434000028.tif216166TIFF0007752434000029.tif216166TIFF0007752434 000030.tif216166TIFF0007752434000031.tif223166TIFF0007752434000032.tif210166TI FF0007752434000033.tif248166TIFF0007752434000034.tif216166TIFF0007752434000035. tif248166TIFF0007752434000036.tif248166TIFF0007752434000037.tif235166TIFF000775 2434000038.tif248166TIFF0007752434000039.tif242166TIFF0007752434000040.tif51166

[0039] In the tandem organic electroluminescent device of the present invention, the separator has a total thickness of 0.1 nm to 10 nm, more preferably 0.3 nm to 5 nm, and even more preferably 0.5 nm to 1 nm. In the tandem organic electroluminescent device of the present invention, the number of electroluminescent units is 2 to 6, and preferably the number of electroluminescent units is 2 to 4. In the tandem organic electroluminescent device of the present invention, the light-emitting unit further includes at least one layer selected from the group consisting of a hole injection layer, a hole transport layer, and an electron blocking layer.

[0040] In this specification, the "substituted or unsubstituted" group may be substituted with one substituent or with multiple substituents, and when there are multiple substituents, the substituents may be selected from different substituents. When the same expression is used in the present invention, it has the same meaning, and the selection range of the substituent is the same as described above, so the description will be omitted. In this specification, the term "independently" means that when there are multiple subjects, they may be the same or different from one another.

[0041] In this specification, unless otherwise specified, both aryl groups and heteroaryl groups include monocyclic and fused ring groups. The monocyclic aryl group contains one or at least two phenyl groups in the molecule. When the molecule contains at least two phenyl groups, the phenyl groups are independently linked by a single bond, such as a phenyl group, a biphenyl group, or a terphenyl group. The fused-ring aryl group contains at least two benzene rings in the molecule, where the benzene rings are not independent of each other but are fused at a common ring edge, such as a naphthyl group or an anthracenyl group. The monocyclic heteroaryl group contains at least one heteroaryl group in the molecule. When the molecule contains one heteroaryl group and another group (e.g., an aryl group, a heteroaryl group, an alkyl group, etc.), the heteroaryl group and the other group are independently linked by a single bond, such as pyridine, furan, or thiophene. The fused-ring heteroaryl group is a group in which at least one phenyl group and at least one heteroaryl group are fused together, or a group in which at least two types of heteroaromatic rings are fused together, such as quinoline, isoquinoline, benzofuran, dibenzofuran, benzothiophene, and dibenzothiophene.

[0042] The tandem OLED device proposed in this invention employs a novel connecting layer structure in which a separator made of a vacuum-deposited electron-transporting material is introduced between an n-type doped layer and a p-type doped layer. This electron-transporting material has the general structural formula shown in formula (1), where the Q group is mainly a π-conjugated group that can connect two acceptor groups, further expanding the conjugated system, improving the transport performance of the separator material and advantageously achieving low driving voltage. In the formula, both R1 and R2 are electron acceptors, and a typical feature is that the molecule contains a nitrogen-containing heterocycle, and the nitrogen atom of such a heterocycle is sp 2 sp hybrids with such lone pairs 2 The strong interaction between the hybrid nitrogen atom and various metal n-type dopants exists. Therefore, introducing an electron transport material having the structure of general formula (1) as a separator between the n-type doped layer and the p-type doped layer can effectively suppress the diffusion and migration of the metal n-type dopant into the p-type doped layer, and further effectively improve the voltage rise during operation of the tandem organic electroluminescent device, thereby improving the life and stability of the tandem OLED device.

[0043] The tandem OLED device employing the connecting layer structure of the present invention has many advantages, such as low driving voltage, high device efficiency, and long operating life, and can meet the current needs of the display and lighting fields. In addition, the raw materials required for the preparation of the compound of the present invention are easily available, and the synthesis process, post-treatment and purification process are simple and reliable, and the preparation process is compatible with conventional manufacturing processes, making it suitable for scientific research and industrial production.

[0044] The design and adjustment of the bonding pattern at the 2- and 9-positions of the o-phenanthroline skeleton of the compound of formula (2) of the present invention is one of the core innovations of the present invention. On the one hand, the o-phenanthroline skeleton is bonded to the bridging group Q via the 2-position, and the nitrogen atom at the 1-position of the o-phenanthroline skeleton can form an intramolecular hydrogen bond with the adjacent hydrogen atom on the bridging group, contributing to improving the sublimability of the material and improving the material stability during deposition and device stability. On the other hand, the 9-position of the o-phenanthroline skeleton is a hydrogen atom, which reduces steric hindrance when the o-phenanthroline skeleton coordinates with transition metals, contributing to better coordination performance.

[0045] The second particularly innovative feature of the compound of formula (2) of the present invention is that R1 and R2 are designed as electron-donating substituents, which significantly increases the electron cloud density and electrostatic potential near the nitrogen atom in the phenanthroline skeleton, contributing to improved coordination ability and achieving superior electron injection performance. As a result, compounds of general formula (2) of the present invention combine excellent coordination ability and stability and can be used as high-performance electron injection materials and in the production of OLED devices.

[0046] [ka] [Brief explanation of the drawings]

[0047] [Figure 1] FIG. 1 is a structural schematic diagram of a tandem organic electroluminescent device having N light-emitting units and N-1 connection layers, which is fabricated in an embodiment of the organic electroluminescent device of the present invention.

[0048] In FIG. 1(a), the device includes an anode, a cathode, N light-emitting units arranged between the two electrodes, and a connecting layer arranged between each pair of adjacent light-emitting units. Each connecting layer has a laminated structure, specifically, includes an N-type doped layer, a P-type doped layer, and a separator arranged between the two. DETAILED DESCRIPTION OF THE INVENTION

[0049] Hereinafter, specific methods for producing the compound of formula (2) of the present invention will be described in detail with reference to synthesis examples, but the production methods of the present invention are not limited to these synthesis examples.

[0050] The various chemicals used in this invention, such as petroleum ether, methylene chloride, ethyl acetate, ethanol, toluene, sodium carbonate, and other basic chemicals, were all purchased from Shanghai Titan Technology Co., Ltd. The mass spectrometer used to identify the following compounds was a ZAB-HS mass spectrometer (Micromass, UK).

[0051] The synthesis method for the compound of the present invention is briefly described below. First, commercially available 4,7-dichloro-o-phenanthroline was used as a starting material, and the 4,7-positions of the o-phenanthroline were substituted or modified by Suzuki coupling. Next, the 2-position of the o-phenanthroline-based skeleton was chlorinated by multi-step transformation. Finally, multiple o-phenanthroline-based skeletons were linked to bridging groups by Suzuki coupling to obtain the target compound. For target compounds in which the 4,7-positions of o-phenanthroline are directly linked to heteroatoms (e.g., O, N, S), the 4,7-dichloro-o-phenanthroline can be modified by base-catalyzed nucleophilic substitution (as shown in Representative Synthesis Route 2), and the target compound can be obtained by a similar procedure. Synthesis Examples

[0052] Representative synthetic route 1

[0053] [ka]

[0054] Representative synthetic route 2

[0055] [ka]

[0056] More specifically, methods for synthesizing representative compounds of the present invention are shown below. Synthesis Example 1 Synthesis of compound L91

[0057] [ka]

[0058] In Example 1, L91-1 (2.80 g, 8.48 mmol) and L91-2 (4.65 g, 19.17 mmol) were added to a 500 mL round-bottom flask, and a mixture of toluene (150 mL), ethanol (50 mL), and deionized water (100 mL) was added. The catalysts, Na2CO3 (6.12 g, 57.78 mmol) and Pd(PPh3)4 (1.08 g, 0.933 mmol), were added. The reaction mixture was refluxed under nitrogen for 36 hours. After cooling, the reaction mixture was filtered. The filter cake was washed with saturated brine and then ethanol, and further treated by conventional methods to obtain the final product, L91 (2.83 g, 68% yield). The theoretical mass spectrometry value [L91 + H] was 491.22, and the MALDI-TOF-MS result was m / z 491.31 [L91 + H]. Elemental analysis results: Theoretical values: C 83.24%, H 5.34%, N 11.42%. Experimental values: C 83.06%, H 5.02%, N 11.92%.

[0059] Synthesis Example 2 Synthesis of compound L92

[0060] [ka]

[0061] First, product L92-2 was obtained from L92-1 by Suzuki cross-coupling according to the above scheme. This product L92-2 was then sequentially treated according to the above scheme to obtain product L92-4. L92-4 (6.46 g, 17.60 mmol), E1-1 (2.64 g, 8.00 mmol), and the catalysts Na2CO3 (6.12 g, 57.78 mmol) and Pd(PPh3)4 (1.08 g, 0.933 mmol) were added to a 500 mL round-bottom flask in a mixture of toluene (150 mL), ethanol (50 mL), and deionized water (100 mL). The mixture was heated under reflux for 36 h, cooled, and filtered. The filter cake was washed several times with ethanol and a dichloromethane / methanol mixture, and further treated by conventional methods to obtain the final product L92 (3.22 g, 54% yield). Mass spectrometry theoretical value [L92+H]: 739.29, MALDI-TOF-MS result: m / z: 739.43 [L92+H]. Elemental analysis results: theoretical value: C 87.78%, H 4.64%, N 7.58%. Experimental value: C 87.67%, H 4.68%, N 7.65%.

[0062] Synthesis Example 3 Synthesis of compound L93

[0063] [ka]

[0064] This example is essentially the same as Synthesis Example 1, except that L91-2 is replaced with an equivalent molar amount (mol) of L93-1. Target compound L93 (5.02 g, 63% yield). Mass analysis theoretical value [L93 + H]: 939.35, MALDI-TOF-MS result: m / z: 939.43 [L93 + H]. Elemental analysis results: theoretical value: C 89.53%, H 4.50%, N 5.97%. Experimental value: C 89.43%, H 4.55%, N 6.02%.

[0065] Synthesis Example 4 Synthesis of compound L94

[0066] [ka]

[0067] This example is essentially the same as Synthesis Example 1, except that L91-2 is replaced with an equivalent molar amount (mol) of L94-1. Target compound L9-4 (4.14 g, 52% yield) was obtained. Mass analysis theoretical value [L94 + H]: 939.35, MALDI-TOF-MS result: m / z: 939.56 [L94 + H]. Elemental analysis results: theoretical value: C 89.53%, H 4.50%, N 5.97%. Experimental value: C 89.51%, H 4.54%, N 5.95%.

[0068] Synthesis Example 5 Synthesis of compound L95

[0069] [ka]

[0070] This example is essentially the same as Synthesis Example 1, except that L91-2 is replaced with an equivalent molar amount (mol) of L95-1. Target compound L95 (2.26 g, 48% yield). Mass analysis theoretical value [L95 + H]: 555.21, MALDI-TOF-MS result: m / z: 555.33 [L95 + H]. Elemental analysis results: theoretical values: C 73.63%, H 4.73%, N 10.10%, O 11.54%. Experimental values: C 73.67%, H 4.72%, N 10.13%, O 11.48%.

[0071] Synthesis Example 6 Synthesis of compound L97

[0072] [ka]

[0073] This example is essentially the same as Synthesis Example 1, except that L91-2 is replaced with an equivalent molar amount (mol) of L97-1. Target compound L97 (3.32 g, 55% yield). Mass analysis theoretical value [L97 + H]: 711.39, MALDI-TOF-MS result: m / z: 711.49 [L97 + H]. Elemental analysis results: theoretical value: C 77.72%, H 6.52%, N 15.76%. Experimental value: C 77.79%, H 6.48%, N 15.73%.

[0074] Synthesis Example 7 Synthesis of compound L103

[0075] [ka]

[0076] This example is basically the same as Synthesis Example 1, except that L91-1 is replaced with an equivalent molar amount (mol) of L103-1. Target compound L103 (1.75 g, 42% yield). Mass analysis theoretical value [L103 + H]: 491.22, MALDI-TOF-MS result: m / z: 491.25 [L103 + H]. Elemental analysis results: theoretical value: C 83.24%, H 5.34%, N 11.42%. Experimental value: C 82.95%, H 5.21%, N 11.84%.

[0077] Synthesis Example 8 Synthesis of compound L104

[0078] [ka]

[0079] This example is essentially the same as Synthesis Example 7, except that L91-2 is replaced with an equivalent molar amount (mol) of L92-4. Target compound L104 (2.94 g, 47% yield) was obtained. Mass analysis theoretical value [L104 + H]: 739.29; MALDI-TOF-MS result: m / z: 739.36 [L104 + H]. Elemental analysis results: theoretical value: C 87.78%, H 4.64%, N 7.58%. Experimental value: C 87.77%, H 4.62%, N 7.61%.

[0080] Synthesis Example 9 Synthesis of compound L105

[0081] [ka]

[0082] This example is essentially the same as Synthesis Example 7, except that L91-2 is replaced with an equivalent molar amount (mol) of L93-1. Target compound L105 (3.50 g, 44% yield) was obtained. Mass analysis theoretical value [L105 + H]: 939.35, MALDI-TOF-MS result: m / z: 939.48 [L105 + H]. Elemental analysis results: theoretical value: C 89.53%, H 4.50%, N 5.97%. Experimental value: C 89.55%, H 4.45%, N 5.94%.

[0083] Synthesis Example 10 Synthesis of compound L106

[0084] [ka]

[0085] This example is essentially the same as Synthesis Example 7, except that L91-2 is replaced with an equivalent molar amount (mol) of L94-1. Target compound L106 (3.26 g, 41% yield) was obtained. Mass analysis theoretical value [L106 + H]: 939.35, MALDI-TOF-MS result: m / z: 939.45 [L106 + H]. Elemental analysis results: theoretical value: C 89.53%, H 4.50%, N 5.97%. Experimental value: C 89.59%, H 4.48%, N 5.93%.

[0086] Synthesis Example 11 Synthesis of compound L107

[0087] [ka]

[0088] This example is essentially the same as Synthesis Example 7, except that L91-2 is replaced with an equivalent molar amount (mol) of L95-1. Target compound L107 (1.69 g, 36% yield) was obtained. Mass analysis theoretical value [L107 + H]: 555.21, MALDI-TOF-MS result: m / z: 555.36 [L107 + H]. Elemental analysis results: theoretical values: C 73.63%, H 4.73%, N 10.10%, O 11.54%. Experimental values: C 73.61%, H 4.76%, N 10.05%, O 11.58%.

[0089] Synthesis Example 12 Synthesis of compound L109

[0090] [ka]

[0091] This example is essentially the same as Synthesis Example 7, except that L91-2 is replaced with an equivalent molar amount (mol) of L97-1. Target compound L109 (2.95 g, 49% yield) was obtained. Mass analysis theoretical value [L109 + H]: 711.39; MALDI-TOF-MS result: m / z: 711.50 [L109 + H]. Elemental analysis results: theoretical values: C 77.72%, H 6.52%, N 15.76%. Experimental values: C 77.74%, H 6.53%, N 15.73%.

[0092] Synthesis Example 13 Synthesis of compound L139

[0093] [ka]

[0094] This example is essentially the same as Synthesis Example 7, except that L103-1 is replaced with an equivalent molar amount (mol) of L139-2. Target compound L139 (2.45 g, 51% yield). Mass analysis: Theoretical value (L139 + H): 567.25; MALDI-TOF-MS result: m / z: 567.32 [L139 + H]. Elemental analysis: Theoretical value: C 84.78%, H 5.34%, N 9.89%. Experimental value: C 84.69%, H 5.36%, N 9.95%.

[0095] Synthesis Example 14 Synthesis of compound L140

[0096] [ka]

[0097] This example is essentially the same as Synthesis Example 8, except that L103-1 is replaced with an equivalent molar amount (mol) of L139-2. Target compound L140 (2.90 g, 42% yield) was obtained. Mass analysis theoretical value [L140 + H]: 815.32; MALDI-TOF-MS result: m / z: 815.52 [L140 + H]. Elemental analysis results: theoretical value: C 88.43%, H 4.70%, N 6.87%. Experimental value: C 88.40%, H 4.73%, N 6.87%.

[0098] Synthesis Example 15 Synthesis of compound L141

[0099] [ka]

[0100] This example is essentially the same as Synthesis Example 9, except that L103-1 is replaced with an equivalent molar amount (mol) of L139-2. Target compound L141 (3.53 g, 41% yield). Mass analysis theoretical value [L141 + H]: 1015.38, MALDI-TOF-MS result: m / z: 1015.46 [L141 + H]. Elemental analysis results: theoretical value: C 89.91%, H 4.57%, N 5.52%. Experimental value: C 89.88%, H 4.55%, N 5.57%.

[0101] Synthesis Example 16 Synthesis of compound L142

[0102] [ka]

[0103] This example is essentially the same as Synthesis Example 10, except that L103-1 is replaced with an equivalent molar amount (mol) of L139-2. Target compound L142 (3.27 g, 38% yield). Mass analysis theoretical value [L142 + H]: 1015.38, MALDI-TOF-MS result: m / z: 1015.49 [L142 + H]. Elemental analysis results: theoretical value: C 89.91%, H 4.57%, N 5.52%. Experimental value: C 89.94%, H 4.58%, N 5.48%.

[0104] Synthesis Example 17 Synthesis of compound L203

[0105] [ka]

[0106] L203-2 (2.74 g, 6.00 mmol) and L91-2 (4.81 g, 19.80 mmol) were added to a 500 mL round-bottom flask, and the resulting mixture was stirred in a solvent mixture of toluene (150 mL), ethanol (50 mL), and deionized water (100 mL). The catalysts were Na2CO3 (6.30 g, 59.4 mmol) and Pd(PPh3). 4( The reaction mixture was heated under reflux for 36 hours under a nitrogen atmosphere. The reaction mixture was cooled and filtered. The filter cake was washed with saturated brine and ethanol, and further treated by conventional methods to obtain the final product L203 (1.97 g, 47% yield). Mass spectrometry (calculated) [L203 + H]: 697.22; MALDI-TOF-MS (m / z) = 697.33 [L203 + H]. Elemental analysis (calculated) = 82.73%, 5.21%, 12.06%; experimental (calculated) = 82.38%, 4.92%, 12.70%.

[0107] Synthesis Example 18 Synthesis of compound L215

[0108] [ka]

[0109] L215-2 (2.83 g, 4.00 mmol) and L91-2 (4.26 g, 17.60 mmol) were added to a 500 mL round-bottom flask. The mixture was heated under reflux for 36 h in a mixture of toluene (150 mL), ethanol (50 mL), and deionized water (100 mL). The catalysts, Na2CO3 (5.60 g, 52.80 mmol) and Pd(PPh3)4 (1.02 g, 0.88 mmol), were added. The reaction mixture was cooled and filtered. The filter cake was washed with saturated brine and ethanol, and further processed by conventional methods to give the final product, L215 (1.60 g, 39% yield). MS theoretical value [L215 + H]: 1027.42; MALDI-TOF-MS result: m / z: 1027.89 [L215 + H]. Elemental analysis results: Theoretical values: C 84.19%, H 4.91%, N 10.90%. Experimental values: C 83.66%, H 5.38%, N 10.96%.

[0110] Synthesis Examples 19-26 The synthesis of specific compounds is illustrated in Table 1 below.

[0111] [Table 1] TIFF0007752434000063.tif64166

[0112] Hereinafter, the technical features and advantages of the present invention will be demonstrated and verified by measuring the performance and properties of the device based on the effect of applying the connecting layer described in the present invention to a tandem organic electroluminescent device.

[0113] A tandem OLED device includes an anode, a cathode, and an organic material layer disposed between the two electrodes. The organic material can be divided into multiple regions. For example, the organic material layer may include a hole transport region, an emissive layer, and an electron transport region.

[0114] In a specific embodiment, a substrate may be used under the first electrode or over the second electrode. The substrate may be a glass or polymer material with excellent mechanical strength, thermal stability, water repellency, and transparency. The display substrate may also have a thin film transistor (TFT).

[0115] The first electrode can be formed by sputtering or evaporating a material for the first electrode onto the substrate. When the first electrode is used as an anode, transparent conductive oxide materials such as indium tin oxide (ITO), indium zinc oxide (IZO), tin dioxide (SnO), zinc oxide (ZnO), and any combination thereof can be used. When the first electrode is used as a cathode, metals or alloys such as magnesium (Mg), silver (Ag), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag), and any combination thereof can be used.

[0116] The organic material layer can be formed on the electrode by methods such as vacuum thermal evaporation, spin coating, printing, etc. The compound used as the organic layer may be an organic small molecule, an organic large molecule and a polymer, or a combination thereof.

[0117] The hole transport region is located between the anode and the light-emitting layer. The hole transport region may be a single-layer hole transport region (HTL) including a single hole transport layer made of only one type of compound or a single hole transport layer made of multiple types of compounds. The hole transport region may also be a multilayer structure including at least one layer selected from the group consisting of a hole injection layer (HIL), a hole transport layer (HTL), and an electron blocking layer (EBL).

[0118] Examples of materials that can be used for the hole transport region include, but are not limited to, phthalocyanine derivatives such as CuPc, polyphenylene vinylene, polyaniline / dodecylbenzenesulfonic acid (PANI / DBSA), poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate) (PEDOT / PSS), polyaniline / camphorsulfonic acid (PANI / CSA), polyaniline / poly(4-styrenesulfonate) (PANI / PSS), conductive polymers such as aromatic amine derivatives, or polymers containing conductive dopants. The hole injection layer is disposed between the anode and the hole transport layer, and may be a single compound material or a combination of multiple compounds.

[0119] The light-emitting layer contains a light-emitting dye (i.e., a dopant) capable of emitting light of different wavelength spectrums, and may also contain a host material. Depending on the technology, different materials can be used for the light-emitting layer, such as fluorescent electroluminescent materials, phosphorescent electroluminescent materials, and thermally activated delayed fluorescent materials. Tandem OLED devices may use a single light-emitting technology or a combination of multiple different light-emitting technologies. These different light-emitting materials may emit the same color or different colors.

[0120] The OLED organic material layer further includes an electron transport region. The electron transport region may be a single-layer electron transport layer (ETL), i.e., a single-layer electron transport layer made of only a single compound, or a single-layer electron transport region made of a single electron transport layer containing several compounds. The electron transport region may also have a multi-layer structure including at least one of an electron injection layer (EIL), an electron transport layer (ETL), and a hole blocking layer (HBL).

[0121] In the tandem OLED device of the present invention, each light-emitting unit comprises a hole-transporting region, a light-emitting layer, and an electron-transporting region. The light-emitting units are connected in series via a connecting layer. The light-emitting units may be single-color light-emitting units that emit light of a single color, such as red, green, or blue, or may be single color light-emitting layers that can simultaneously emit light of different colors, such as red, green, and blue.

[0122] The connecting layer in the tandem OLED device of the present invention is as shown in Figure 1, where the first light-emitting unit is formed on the anode of the device, the connecting layer 1 of the device is formed between the first light-emitting unit and the second light-emitting unit, the connecting layer including an n-type doped layer, a p-type doped layer and a separator therebetween, and the connecting layer 2, the third light-emitting unit is formed on the second light-emitting unit, and N-1 connecting layers may be formed correspondingly according to the device structure design until the Nth light-emitting unit is formed, and finally the cathode of the device is formed.

[0123] The n-type doped layer is primarily composed of a doping host and an n-type dopant. The doping host is primarily an electron transport material, and the n-type dopant is primarily composed of alkali metals, alkaline earth metals, and partial transition metals, including lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca), gold (Au), silver (Ag), copper (Cu), iron (Fe), nickel (Ni), platinum (Pt), palladium (Pd), ruthenium (Ru), and ytterbium (Yb). In Figure 1, the doping ratio of the metal n-type dopant in the n-type doped layer is 0.2 wt% to 30 wt%, with a preferred doping ratio of 0.5 wt% to 10 wt%.

[0124] The p-type doped layer is composed of a p-type doping host material mainly using an organic material having hole transport properties, and a p-type dopant using a metal oxide having a high work function or an organic semiconductor material having high electron-withdrawing properties, and examples of the p-type dopant include MoO3, WO3, V2O5, MoO2, Co3O4, CN6-CP, DDQ, HATCN, and C 60 F36 , F4TCNQ, F4-R-TCNQ, F3-R-TCNQ, F2HCNQ, F6TCNNQ, and TECTFCNBN, or a mixture of two or more thereof.

[0125] The separator between the n-type doped layer and the p-type doped layer is mainly made of an electron transport material and has a total thickness of 0.1 nm to 10 nm, more preferably 0.3 nm to 5 nm. The organic material having electron transport properties used in the separator has a structure represented by the following formula (1) or formula (2).

[0126] [ka]

[0127] The manufacturing process of the organic electroluminescent device in the embodiment of the present invention is as follows.

[0128] Specifically, the tandem OLED device used in this experiment is a dual-emissive device with one connecting layer. The device fabrication process involves ultrasonically treating a glass plate coated with an ITO transparent conductive layer in a commercial cleaner, cleaning in deionized water, ultrasonically removing oil in an acetone:ethanol mixed solvent, baking in a clean environment until all moisture is removed, cleaning with ultraviolet light and ozone, and bombarding the surface with a low-energy positive ion beam.

[0129] The glass substrate with the anode was placed in a vacuum chamber and 1×10 -5 ~5×10 -4 The pressure is evacuated to Pa, and HATCN is vacuum-deposited onto the anode layer as a hole injection layer at a deposition rate of 0.05 nm / s to a deposition film thickness of 5 to 10 nm. As the hole transport layer of the device, NPB is vacuum-deposited on the hole injection layer at a deposition rate of 0.1 nm / s and a total deposition thickness of 30 to 50 nm.

[0130] The light-emitting layer of the device was vacuum-deposited on the hole-injection layer. The light-emitting layer of the present invention contained a host material Be(bq)2 and a phosphorescent dye Ir(mphmq)2(tmd). The doping was performed by multi-source co-evaporation, with the rate and doping concentration adjusted using a high- and low-crystal oscillator. The deposition rate of the host material was adjusted to 0.1 nm / s, and the dye deposition rate in the light-emitting layer was adjusted to 1% to 5% of the host deposition rate, achieving a desired doping ratio. The total thickness of the deposited light-emitting layer was 20 to 50 nm. DPPyA as an electron transport layer material is vacuum-deposited on the light-emitting layer at a deposition rate of 0.1 nm / s to a total deposition thickness of 20 to 60 nm.

[0131] A connecting layer is vacuum-deposited on the electron transport layer (ETL) to a total thickness of 20-60 nm. The n-type dopant layer is 10 nm thick, the doping host is Bphen, the n-type dopant is an alkali metal or transition metal such as Li, Cs, or Ag, and the doping ratio is 10%. The separator is 0-10 nm thick depending on the experimental needs. The p-type doped layer is 20 nm thick, the doping host is NPB, the p-type dopant is TECTFCNBN, and the doping ratio is 3%.

[0132] Then, a hole transport layer of 30 to 50 nm NPB, an emitting layer with a total thickness of 20 to 50 nm, an electron transport layer of 20 to 60 nm, an electron injection layer of 1 nm LiF, and a cathode of 150 nm Al were sequentially evaporated to fabricate a tandem OLED device with a dual emitting layer.

[0133] Table 2 below lists the organic compounds and their structural formulas used in the tandem OLED devices fabricated in the examples of the present invention.

[0134] [Table 2]

[0135] Device Example 1

[0136] A glass plate coated with an ITO transparent conductive layer was ultrasonically degreased with a commercial cleaner, washed with deionized water, ultrasonically degreased with an acetone:ethanol mixed solvent, baked in a clean environment until all moisture was removed, cleaned with ultraviolet light and ozone, and bombarded with a low-energy positive ion beam.

[0137] The glass substrate with the anode was placed in a vacuum chamber and 1×10 -5 ~5×10 -4 The pressure was evacuated to Pa, and HATCN was vacuum-deposited onto the anode layer as a hole injection layer at a deposition rate of 0.05 nm / s to a deposition thickness of 5 nm. On the hole injection layer, NPB was vacuum-deposited as a hole transport layer of the device at a deposition rate of 0.1 nm / s to a total deposition thickness of 35 nm.

[0138] The device's emissive layer was vacuum-deposited on the hole-injection layer. The emissive layer of the present invention contained a host material Be(bq)2 and a phosphorescent dye Ir(mphmq)2(tmd). The doping was performed by multi-source co-evaporation, with the rate and doping concentration adjusted using a high-low quartz crystal probe. The deposition rates of the host materials were all 0.1 nm / s, and the dye deposition rate in the emissive layer was 5% of the host deposition rate, achieving the desired doping ratio. The total thickness of the deposited emissive layer was 24 nm. DPPyA, a material for the electron transport layer of the device, was vacuum-deposited on the light-emitting layer at a deposition rate of 0.1 nm / s to a total deposited film thickness of 40 nm.

[0139] An n-type doped layer was deposited on the electron transport layer (ETL), and a connecting layer was vacuum-deposited on the ETL to a total thickness of 20 nm. The n-type doped layer was 10 nm thick, with a doping host of Bphen and an n-type dopant of Li at a doping ratio of 10%. A p-type doped layer was then deposited, with a doping host of NPB and a p-type dopant of TECTFCNBN at a doping ratio of 3%.

[0140] Then, a 50-nm NPB hole-transporting layer, a 24-nm-thick emissive layer with a 5% Be(bq)2:Ir(mphmq)2(tmd) doping ratio, a 40-nm DPPyA electron-transporting layer, a 1-nm LiF electron-injecting layer, and a 150-nm Al cathode were sequentially evaporated to fabricate a dual-emissive layer tandem OLED device.

[0141] It has the following structure: ITO / HATCN(5nm) / NPB(35nm) / Be(bq)2:Ir(mphmq)2(tmd)(5%, 24nm) / DPPyA(40nm) / Bphen:Li(10%, 10nm) / NPB :TECTFCNBN(3%, 10nm) / NPB(35nm) / Be(bq)2:Ir(mphmq)2(tmd)(5%, 24nm) / DPPyA(40nm) / LiF(1nm) / Al(150nm)

[0142] Device Example 2

[0143] The fabrication method was the same as in Example 1, except for the introduction of a 0.1 nm L12 separator between the n-doped and p-doped layers. The corresponding tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Li (10%, 10 nm) / L12 (0.1 nm) / NPB:TECTFCNBN (3%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0144] Device Example 3: Same manufacturing method as in Example 2, except for the introduction of a 0.3 nm L12 separator between the n-type doped layer and the p-type doped layer. Device Example 4: Same fabrication method as in Example 2, except for the introduction of a 0.5 nm L12 separator between the n-type and p-type doped layers. Device Example 5: Same manufacturing method as in Example 2, except for the introduction of a 1 nm L12 separator between the n-type doped layer and the p-type doped layer. Device Example 6: Same fabrication method as in Example 2, except for the introduction of a 3 nm L12 separator between the n-type doped layer and the p-type doped layer. Device Example 7: Same fabrication method as in Example 2, except for the introduction of a 5 nm L12 separator between the n-type and p-type doped layers. Device Example 8: Same fabrication method as in Example 2, except for the introduction of a 7 nm L12 separator between the n-type and p-type doped layers. Device Example 9: Same fabrication method as Example 2, except for the introduction of a 10 nm L12 separator between the n-type and p-type doped layers.

[0145] Device Example 10 The manufacturing method is the same as in Example 1, except that the p-type dopant used is MoO, the p-type doped layer is 10 nm thick, and the p-type dopant content is 10%. The corresponding tandem OLED device structure is ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Li (10%, 10 nm) / NPB:MoO3 (10%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0146] Device Example 11

[0147] The fabrication method was the same as in Example 10, except for the introduction of a 0.1 nm L12 separator between the n-type and p-type doped layers. The corresponding tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Li (10%, 10 nm) / L12 (0.1 nm) / NPB:MoO3 (10%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0148] Device Example 12 The manufacturing method is the same as that of Example 10, except that a 0.3 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 13 The manufacturing method is the same as that of Example 10, except that a 0.5 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 14 The manufacturing method is the same as that of Example 10, except that a 1 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 15 The manufacturing method is the same as that of Example 10, except that a 3 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 16 The manufacturing method is the same as that of Example 10, except that a 5 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 17 The manufacturing method is the same as that of Example 10, except that a 7 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer.

[0149] Device Example 18 The manufacturing method is the same as that of Example 10, except that a 10 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer.

[0150] The performance data of the tandem OLED devices of the present invention using L12 as a separator, which were produced in the above Device Examples 1 to 18, are summarized in Table 3 below.

[0151] [Table 3]

[0152] Device Example 19

[0153] The fabrication method was the same as in Example 1, except that the n-type dopant used was Cs, the thickness of the n-type doped layer was 10 nm, and the proportion of n-type dopant was 10%. The corresponding tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Cs (10%, 10 nm) / NPB:TECTFCNBN (3%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0154] Device Example 20

[0155] The fabrication method was the same as in Example 19, except for the introduction of a 0.1 nm L12 separator between the n-type and p-type doped layers. The corresponding tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Cs (10%, 10 nm) / L12 (0.1 nm) / NPB:TECTFCNBN (3%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0156] Device Example 21

[0157] The manufacturing method was the same as in Example 19, except that a 0.3 nm L12 separator was introduced between the n-type doped layer and the p-type doped layer. Device Example 22 The manufacturing method is the same as that of Example 19, except that a 0.5 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 23 The manufacturing method is the same as that of Example 19, except that a 1 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 24 The manufacturing method is the same as that of Example 19, except that a 3 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 25 The manufacturing method is the same as that of Example 19, except that a 5 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 26 The manufacturing method is the same as that of Example 19, except that a 7 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 27 The manufacturing method is the same as that of Example 19, except that a 10 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer.

[0158] Device Example 28

[0159] The fabrication method was the same as in Example 19, except that the p-type dopant used was MoO, the thickness of the p-type doped layer was 10 nm, and the proportion of p-type dopant was 10%. The corresponding tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Cs (10%, 10 nm) / NPB:MoO3 (10%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0160] Device Example 29

[0161] Example 28 The fabrication method is the same as in

[10] , except for the introduction of a 0.1 nm L12 separator between the n-doped and p-doped layers. The corresponding tandem OLED device structure is ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Cs (10%, 10 nm) / L12 (0.1 nm) / NPB:MoO3 (10%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0162] Device Example 30 Example 28 The manufacturing method is the same as that of , except that a 0.3 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 31 Example 28 The manufacturing method is the same as that of , except that a 0.5 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 32 Example 28 The manufacturing method is the same as that of , except that a 1 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 33 Example 2 8 The manufacturing method is the same as that of , except that a 3 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 34 Example 28 The manufacturing method is the same as that of , except that a 5 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 35 Example 28The manufacturing method is the same as that of , except that a 7 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 36 Example 28 The manufacturing method is the same as that of , except that a 10 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer.

[0163] Table 4 below shows the performance data of the tandem OLED devices of the present invention using L12 as a separator, which were produced in the above device examples 19 to 36.

[0164] [Table 4]

[0165] Device Example 37

[0166] The fabrication method was the same as in Example 1, except that the n-type dopant used was Ag, the thickness of the n-type doped layer was 10 nm, and the proportion of n-type dopant was 10%. The corresponding tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Ag (10%, 10 nm) / NPB:TECTFCNBN (3%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0167] Device Example 38

[0168] Example 37The fabrication method is the same as in

[10] , except for the introduction of a 0.1 nm L12 separator between the n-doped and p-doped layers. The corresponding tandem OLED device structure is ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Ag (10%, 10 nm) / L12 (0.1 nm) / NPB:TECTFCNBN (3%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0169] Device Example 39 Example 37 The manufacturing method is the same as that of , except that a 0.3 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 40 Example 37 The manufacturing method is the same as that of , except that a 0.5 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 41 Example 37 The manufacturing method is the same as that of , except that a 1 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 42 Example 37 The manufacturing method is the same as that of , except that a 3 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 43 Example 37 The manufacturing method is the same as that of , except that a 5 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 44 Example 37 The manufacturing method is the same as that of , except that a 7 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 45 Example 37The manufacturing method is the same as that of , except that a 10 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer.

[0170] Device Example 46

[0171] Example 37 The fabrication method is the same as in (1), except that the p-dopant used is MoO3, the thickness of the p-doped layer is 10 nm, and the p-dopant content is 10%. The corresponding tandem OLED device structure is ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Ag (10%, 10 nm) / NPB:MoO3 (10%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0172] Device Example 47

[0173] Example 46 The fabrication method is the same as in

[10] , except for the introduction of a 0.1 nm L12 separator between the n-doped and p-doped layers. The tandem OLED device structure is ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Cs (10%, 10 nm) / L12 (0.1 nm) / NPB:MoO3 (10%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0174] Device Example 48 Example 46 The manufacturing method is the same as that of , except that a 0.3 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 49 Example 46The manufacturing method is the same as that of , except that a 0.5 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 50 Example 46 The manufacturing method is the same as that of , except that a 1 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 51 Example 46 The manufacturing method is the same as that of , except that a 3 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 52 Example 46 The manufacturing method is the same as that of , except that a 5 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 53 Example 46 The manufacturing method is the same as that of , except that a 7 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 54 Example 46 The manufacturing method is the same as that of , except that a 10 nm L12 separator is introduced between the n-type doped layer and the p-type doped layer.

[0175] The performance data of the tandem OLED devices of the present invention using L12 as a separator, which were produced in the above device examples 37 to 54, are summarized in Table 5 below.

[0176] [Table 5]

[0177] Element Example 55

[0178] The fabrication method was the same as in Example 1, except that the tandem device had three light-emitting units and two connecting layers. The corresponding tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Li (10%, 10 nm) / NPB:TECTFCNBN (3%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0179] Device Example 56

[0180] The fabrication method was the same as in Example 55, except that 0.5 nm of L12 was introduced as a separator in both of the two connecting layers of this tandem device. The corresponding tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Li (10%, 10 nm) / L12 (0.5 nm) / NPB:TECTFCNBN (3%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0181] Device Example 57

[0182] The fabrication method was the same as in Example 55, except that 1 nm of L12 was incorporated as a separator into both connecting layers of this tandem device. The corresponding tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Li (10%, 10 nm) / L12 (1 nm) / NPB:TECTFCNBN (3%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0183] Device Example 58

[0184] The fabrication method was the same as in Example 1, except that this tandem device had four light-emitting units and three connecting layers. The corresponding tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Li (10%, 10 nm) / NPB:TECTFCNBN (3%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0185] Device Example 59

[0186] The fabrication method was the same as in Example 58, except that 0.5 nm of L12 was introduced as a separator into both the connecting layers of this tandem device and the connecting layer 3. The corresponding tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Li (10%, 10 nm) / L12 (0.5 nm) / NPB:TECTFCNBN (3%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0187] Device Example 60

[0188] The fabrication method was the same as in Example 58, except that 1 nm of L12 was introduced as a separator into each of the three connecting layers of this tandem device. The corresponding tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Li (10%, 10 nm) / L12 (1 nm) / NPB:TECTFCNBN (3%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0189] Table 6 below shows the performance data of the tandem OLED devices of the present invention which were prepared in the above device Examples 55 to 60 and which used L12 as a separator and had different numbers of light-emitting units.

[0190] [Table 6]

[0191] Device Example 61 The fabrication method was the same as in Example 2, except for the introduction of a 0.5 nm L1 separator between the n-type and p-type doped layers. The tandem OLED device structure was ITO / HATCN (5 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / Bphen:Li (10%, 10 nm) / L12 (0.1 nm) / NPB:TECTFCNBN (3%, 10 nm) / NPB (35 nm) / Be(bq)2:Ir(mphmq)2(tmd) (5%, 24 nm) / DPPyA (40 nm) / LiF (1 nm) / Al (150 nm).

[0192] Device Example 62 The manufacturing method is the same as that of Example 2, except that a 1 nm L1 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 63 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L2 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 64 The manufacturing method is the same as that of Example 2, except that a 1 nm L2 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 65 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L3 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 66 The manufacturing method is the same as that of Example 2, except that a 1 nm L3 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 67 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L4 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 68 The manufacturing method is the same as that of Example 2, except that a 1 nm L4 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 69 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L5 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 70 The manufacturing method is the same as that of Example 2, except that a 1 nm L5 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 71 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L6 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 72 The manufacturing method is the same as that of Example 2, except that a 1 nm L6 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 73 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L7 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 74 The manufacturing method is the same as that of Example 2, except that a 1 nm L7 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 75 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L8 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 76 The manufacturing method is the same as that of Example 2, except that a 1 nm L8 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 77 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L11 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 78 The manufacturing method is the same as that of Example 2, except that a 1 nm L11 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 79 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L13 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 80 The manufacturing method is the same as that of Example 2, except that a 1 nm L13 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 81 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L14 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 82 The manufacturing method is the same as that of Example 2, except that a 1 nm L14 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 83 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L19 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 84 The manufacturing method is the same as that of Example 2, except that a 1 nm L19 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 85 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L20 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 86 The manufacturing method is the same as that of Example 2, except that a 1 nm L20 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 87 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L21 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 88 The manufacturing method is the same as that of Example 2, except that a 1 nm L21 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 89 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L22 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 90 The manufacturing method is the same as that of Example 2, except that a 1 nm L22 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 91 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L25 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 92 The manufacturing method is the same as that of Example 2, except that a 1 nm L25 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 93 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L26 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 94 The manufacturing method is the same as that of Example 2, except that a 1 nm L26 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 95 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L27 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 96 The manufacturing method is the same as that of Example 2, except that a 1 nm L27 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 97 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L28 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 98 The manufacturing method is the same as that of Example 2, except that a 1 nm L28 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 99 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L29 separator is introduced between the n-type doped layer and the p-type doped layer. Device Example 100 The manufacturing method is the same as that of Example 2, except that a 1 nm L29 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 101 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L31 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 102 The manufacturing method is the same as that of Example 2, except that a 1 nm L31 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 103 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L32 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 104 The manufacturing method is the same as that of Example 2, except that a 1 nm L32 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 105 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L33 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 106 The manufacturing method is the same as that of Example 2, except that a 1 nm L33 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 107 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L35 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 108 The manufacturing method is the same as that of Example 2, except that a 1 nm L35 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 109 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L37 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 110 The manufacturing method is the same as that of Example 2, except that a 1 nm L37 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 111 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L43 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 112 The manufacturing method is the same as that of Example 2, except that a 1 nm L43 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 113 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L49 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 114 The manufacturing method is the same as that of Example 2, except that a 1 nm L49 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 115 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L57 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 116 The manufacturing method is the same as that of Example 2, except that a 1 nm L57 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 117 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L75 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 118 The manufacturing method is the same as that of Example 2, except that a 1 nm L75 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 119 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L79 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 120 The manufacturing method is the same as that of Example 2, except that a 1 nm L79 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 121 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L103 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 122 The manufacturing method is the same as that of Example 2, except that a 1 nm L103 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 123 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L107 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 124 The manufacturing method is the same as that of Example 2, except that a 1 nm L107 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 125 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L109 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 126 The manufacturing method is the same as that of Example 2, except that a 1 nm L109 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 127 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L175 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 128 The manufacturing method is the same as that of Example 2, except that a 1 nm L175 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 129 The manufacturing method is the same as in Example 2, except that a 0.5 nm L179 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 130 The manufacturing method is the same as in Example 2, except that a 1 nm L179 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 131 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L181 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 132 The manufacturing method is the same as that of Example 2, except that a 1 nm L181 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 133 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L195 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 134 The manufacturing method is the same as in Example 2, except that a 1 nm L195 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 135 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L2O3 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 136 The manufacturing method is the same as that of Example 2, except that a 1 nm L2O3 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 137 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L207 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 138 The manufacturing method is the same as that of Example 2, except that a 1 nm L207 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 139 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L209 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 140 The manufacturing method is the same as that of Example 2, except that a 1 nm L209 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 141 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L215 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 142 The manufacturing method is the same as that of Example 2, except that a 1 nm L215 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 143 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L219 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 144 The manufacturing method is the same as in Example 2, except that a 1 nm L219 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 145 The manufacturing method is the same as that of Example 2, except that a 0.5 nm L221 separator is introduced between the n-type doped layer and the p-type doped layer. Element Example 146 The manufacturing method is the same as that of Example 2, except that a 1 nm L221 separator is introduced between the n-type doped layer and the p-type doped layer.

[0193] The performance data of the tandem OLED devices of the present invention using the representative compounds of the present invention produced in the above device Examples 61 to 146 as separators are summarized in Table 7 below.

[0194] [Table 7] TIFF0007752434000071.tif223166

[0195] Comparing Examples 1-9 with Examples 37-45, it can be seen that, when the other materials in the tandem organic electroluminescent device structure are the same, the introduction of a 0.1-10 nm thick separator into the connecting layer reduces the voltage rise after 24 hours of operation, significantly improves device stability, and correspondingly improves device lifespan. This is presumably because, during deposition and device operation, the metal-based n-type dopant migrates or diffuses into the p-type dopant or emissive layer, causing aging of the connecting layer and exciton quenching in the emissive layer, thereby reducing device efficiency and lifespan. When introducing a separator to improve device lifespan, the optimal thickness is generally approximately 0.1-10 nm.

[0196] Comparing Examples 1 to 9, 19 to 27, and 41 to 50, it can be seen that the type of n-type dopant significantly affects the lifetime of tandem OLED devices. The simple trend of silver > lithium > cesium from the viewpoint of lifetime is primarily due to the strong coordination effect between silver and Bphen for the same doping host, resulting in the strongest interaction. Electrostatic interactions primarily exist between lithium, cesium, and Bphen. Because the radius of cesium is much larger than that of lithium, the interaction between lithium and Bphen is stronger than that of cesium for the +1 ion formed by these two. Therefore, the order of the interaction strength between these three metal n-type dopants and Bphen is silver stronger than lithium, which in turn is lithium stronger than cesium. Therefore, tandem OLED devices using silver as the n-type dopant have a longer lifetime than OLED devices using cesium. At the same time, the separator introduced has a certain blocking effect on the migration of all three metals, so the separator of the present invention has the same life-improving effect on tandem OLED devices using different n-type dopants.

[0197] Comparing Examples 1 to 9 with Examples 10 to 18, and Examples 19 to 27 with Examples 28 to 36, Examples 37 to 45, and Examples 46 to 54, it can be seen that the separator of the present invention can improve the stability of tandem OLED devices, whether they use an organic semiconductor p-type dopant such as TECTFCNBN or an inorganic semiconductor p-type dopant such as MoO, and shows similar effects. This is because the migration and diffusion of metal n-type dopants are factors that cause a decrease in lifespan and an increase in voltage during aging of tandem OLED devices. Therefore, the introduction of a separator helps improve the performance of tandem OLED devices that use metal n-type dopants and different types of p-type dopants.

[0198] In Examples 1, 4, 5, and 61-120, nearly 30 different separator materials were used. Devices using L12 as a separator demonstrated superior device performance compared to L14, specifically, smaller changes in device drive voltage and longer lifetimes. The peripheral electron acceptor groups of L12 and L14 are o-phenanthroline and 2-phenyl-o-phenanthroline, respectively. The peripheral phenyl groups are presumably responsible for not only lowering the electrostatic potential of the nitrogen atom but also for causing steric hindrance and inhibiting interaction with metals. Therefore, L12 has a stronger ability to block the migration or diffusion of metal-based n-type dopants than L14, and thus tandem OLED devices using separators based on L12 have superior lifetimes. Furthermore, while Examples 61 to 82 primarily used separator materials containing bis-o-phenanthroline groups, Examples 85 to 94 primarily used separator materials containing triazine and pyridine groups. The o-phenanthroline-based materials in tandem OLED devices were found to be more effective at preventing metal ion migration than materials such as L19 and L20. This is likely due to the large electrostatic potential near the nitrogen atom of the o-phenanthroline group, which has a strong interaction with the metal n-type dopant, making them advantageous for suppressing metal diffusion and migration. Furthermore, in Examples 61 to 120, a comparison of the performance of tandem devices using separators with thicknesses of 0.5 nm and 1 nm revealed that tandem OLED devices using 0.5 nm separators had lower tandem resistance and therefore lower device drive voltages. However, the tandem OLED device with a separator thickness of 1 nm is superior to the tandem OLED device with a separator thickness of 0.5 nm in both lifetime and voltage stability, which indicates that using a thicker separator contributes to further suppressing the diffusion of metallic n-type dopants, and further reflects the impact of the separator according to the present invention on device performance.The separator materials used in Examples 95 to 120 have a phenylpyridine group on one side and an o-phenanthroline group on the other side, and bridging groups such as naphthalene, substituted and unsubstituted anthracene, etc. Such large π-conjugated groups are advantageous for the formation of strong π-π stacking to enhance electron mobility, while such large π-conjugated bridging groups extend the conjugation of molecules and contribute to increasing the stability of negatively charged molecules, so that tandem OLED devices based on such separator materials exhibit better stability.

[0199] Examples 121-126 use L103, L107, and L109 as separator materials. Compared to Examples 4 and 5, these materials are substituted at the 4th and 7th positions of the o-phenanthroline with methyl, methoxy, and tetrahydropyrrolyl groups, respectively. The inventors found that when the separator thickness was 0.5 nm, device performance using L103, L107, and L109 as separators was superior to that of L12, specifically exhibiting longer lifetimes and smaller changes in drive voltage, but the opposite was true when the separator thickness was 1 nm. This is presumably because the introduction of electron-donating substituents in L103, L107, and L109 increases the electrostatic potential near the nitrogen atom of the o-phenanthroline group, and its spatial distribution favors the material's adoption of a U conformation. This further increases the electrostatic potential of the coordination center, favoring bonding with metals and therefore better preventing the migration or diffusion of metallic n-type dopants. However, the introduction of these non-conjugated substituents increases the intermolecular distance, which is unfavorable for electron transport, and therefore good performance is only observed when the film is thin, and the performance deteriorates when the film is thicker.

[0200] Examples 127-146 used 10 different separator materials. Compared to Examples 121-126, these materials used different crosslinking groups. Some used larger π-conjugated pyrenyl groups (Examples 127-132, Examples 141-146), others used nitrogen-containing pyridine groups (Examples 133 and 134), and still others increased the number of o-phenanthrolines bonded to the crosslinking groups (Examples 135-146). The use of larger π-conjugated groups is advantageous for improving electron mobility and molecular stability. The use of nitrogen-containing groups or increasing the number of o-phenanthrolines bonded to the crosslinking groups increases the number of ligands, which is advantageous for the interaction between the material and the metal. This improves the ability to suppress metal migration and diffusion, resulting in better device characteristics. These results demonstrate that separators constructed from nitrogen-containing heterocyclic electron-transporting materials have a strong interaction with metal n-type dopants and contribute to suppressing the migration and diffusion of metals, which is advantageous for improving the exciton utilization rate and the efficiency and lifetime of OLED devices.

[0201] In Examples 55 to 60, the effect of the separator on tandem OLEDs with 3 and 4 light-emitting units was mainly verified. It was found that the introduction of 1 nm of L12 as a separator for tandem OLED elements containing 3 and 4 light-emitting units similarly suppressed the migration and diffusion of metals in the n-type doped layer and improved the stability of the organic electroluminescent elements.

[0202] As described above, the design measures of the connecting layer of the new tandem OLED device proposed in the present invention, i.e., n-type doped layer / separator / p-type doped layer, contribute to suppressing the diffusion and migration of metallic n-type dopants in the tandem OLED device, improving the stability of the connecting layer, and reducing exciton quenching in the emitting layer, and can be applied to the tandem OLED device, thereby contributing to achieving a longer lifespan and lower voltage rise during device operation.

[0203] The above examples are merely illustrative and are not intended to limit the scope of the present invention. Based on the concept of the present invention, those skilled in the art can make various modifications and improvements, and can also make other different changes or modifications based on the above description, and obvious changes or modifications resulting from these are also within the scope of protection of the present invention.

Claims

1. A tandem organic electroluminescent device comprising an anode, a cathode, at least two electroluminescent units disposed between the anode and the cathode, and a connecting layer disposed between adjacent electroluminescent units, each of the electroluminescent units having at least one electron transport layer and one organic light-emitting layer, wherein the connecting layer has a multi-layer structure including an n-type doped layer, a p-type doped layer, and a separator disposed therebetween; the n-type doped layer comprises an n-type doping host material using an organic material having electron transport properties, and an n-type dopant using an alkali metal, an alkaline earth metal, or a transition metal; the p-type doped layer comprises a p-type doping host material using an organic material having hole transport properties, and a p-type dopant using a metal oxide having a high work function or an organic semiconductor material having high electron-withdrawing properties; the separator is made of an organic material having electron transport properties different from those of the n-type doping host material, The organic material having electron transport properties used in the separator is represented by the following formula (2): 【Chemistry 1-1】 (In formula (2), when n is 2, 3, or 4, Q is one selected from the following substituted or unsubstituted groups.) 【Chemistry 3】 (In formula (2), R1 and R2 are each independently selected from one of a C1-C30 aliphatic chain hydrocarbyloxy group, a C2-C30 aliphatic chain hydrocarbylamino group, a C3-C20 cyclic aliphatic chain hydrocarbylamino group, a substituted or unsubstituted C6-C30 arylamino group, a substituted or unsubstituted C3-C30 heteroarylamino group, a substituted or unsubstituted C6-C60 aryl group, and a substituted or unsubstituted C3-C60 heteroaryl group; and when R1 and R2 have substituents, the substituents are one or a combination of two selected from the group consisting of deuterium, halogen, a C1-C30 linear alkyl group, a C3-C30 cycloalkyl group, a cyano group, a nitro group, a C1-C6 alkoxy group, a C1-C6 thioalkoxy group, a C6-C30 aryl group, and a C3-C60 heteroaryl group.) It has a structure represented by either A tandem organic electroluminescent device characterized by:

2. The electroluminescent unit further includes at least one layer selected from the group consisting of a hole injection layer, a hole transport layer, and an electron blocking layer. The tandem organic electroluminescent device according to claim 1 .

3. In the n-type doped layer, the doping ratio of the n-type dopant is 0.2 wt % to 30 wt %; The n-type dopant is one or a mixture of several selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, gold, silver, copper, iron, nickel, platinum, palladium, ruthenium, and ytterbium. The tandem organic electroluminescent device according to claim 1 .

4. In the p-type doped layer, the doping ratio of the p-type dopant is 0.2 wt % to 30 wt %; The p-type dopant is MoO ３ , W.O. ３ , V ２ O ５ , MoO ２ , Co ３ O ４ ,CN6-CP,DDQ,HATCN,C ６０ F ３６ , F4TCNQ, F2HCNQ, F6TCCNNQ, TECTFCNBN or a mixture of several thereof is used. The tandem organic electroluminescent device according to claim 1 .

5. The total thickness of the separator is 0.1 nm to 10 nm. The tandem organic electroluminescent device according to claim 1 .

6. The organic material having electron transport properties used in the separator is the following compound: 【Chemistry 8-2】 【change】 【change】 【change】 【change】 【change】 【change】 【change】 【change】 【change】 【change】 【change】 【change】 【change】 Selected from The tandem organic electroluminescent device according to claim 1 .

7. The number of the electroluminescent units is 2 to 6. The tandem organic electroluminescent device according to claim 1 or 6.

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