Laminated organic light-emitting device and application thereof

Abstract

The invention provides a laminated organic light-emitting device and application thereof. The laminated organic light-emitting device comprises a first electrode, a first light-emitting unit, a connecting layer, a second light-emitting unit and a second electrode which are sequentially arranged, the first light-emitting unit comprises a hole injection layer A, a hole transmission layer A, a light-emitting layer A and a hole blocking layer A which are arranged in sequence; the hole barrier layer A is laminated with the connecting layer; the second light-emitting unit comprises an electron injection layer B, an electron transport layer B, a hole blocking layer B, a light-emitting layer B and a hole transport layer B which are arranged in sequence; and the hole transport layer B is laminated with the connecting layer. According to the laminated organic light-emitting device, through the specific structural design, the voltage of the laminated organic light-emitting device can be effectively reduced, and meanwhile it can be guaranteed that the laminated organic light-emitting device has equivalent or higher efficiency and service life.

Description

Technical Field

[0001] The invention belongs to the technical field of luminescent materials, and in particular relates to a laminated organic luminescent device and applications thereof. Background Art

[0002] As a new generation of display technology, organic electroluminescent materials (OLEDs) have the advantages of ultra-thinness, self-luminescence, wide viewing angle, fast response, high luminous efficiency, good temperature adaptability, simple production process, low driving voltage and low energy consumption. They have been widely used in flat panel displays, flexible displays, solid-state lighting and automotive displays.

[0003] According to the luminescence mechanism, organic electroluminescent materials can be divided into electrofluorescence and electrophosphorescence. Fluorescence is the radiative decay transition of singlet excitons, while phosphorescence is the light emitted by triplet excitons when they decay to the ground state. According to the spin quantum statistics theory, the probability ratio of singlet excitons and triplet excitons is 1:3. The internal quantum efficiency of fluorescent materials does not exceed 25%, and the external quantum efficiency is generally less than 5%; the internal quantum efficiency of electrophosphorescent materials theoretically reaches 100%, and the external quantum efficiency can reach 20%. In 1998, Professor Ma Yuguang of Jilin University in my country and Professor Forrest of Princeton University in the United States reported the use of osmium complexes and platinum complexes as dyes doped into the light-emitting layer, and successfully obtained and explained the phenomenon of phosphorescent electroluminescence for the first time, and pioneered the application of the prepared phosphorescent materials to electroluminescent devices.

[0004] Organic light-emitting devices can form a variety of structures, and tandem organic light-emitting devices are one of them. In a tandem device, light-emitting units containing a light-emitting layer are stacked between the anode and the cathode. There is a charge generation layer between adjacent light-emitting parts for the generation and movement of charges, and the charge generation layer requires low driving voltage and high efficiency. However, the current charge generation layer material selectivity of tandem organic light-emitting devices is relatively limited, and there are problems such as high driving voltage and low efficiency. The main reasons are problems with the material itself and poor matching of energy levels of adjacent layers.

[0005] Therefore, developing a stacked organic light-emitting device with low voltage and high efficiency is an urgent problem to be solved in the field. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a stacked organic light-emitting device and a display device comprising the same. The stacked organic light-emitting device can effectively reduce the voltage of the stacked organic light-emitting device through a specific structural design, and at the same time, can also ensure that the stacked organic light-emitting device has equivalent or higher efficiency and lifespan.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a stacked organic light-emitting device, comprising a first electrode, a first light-emitting unit, a connecting layer, a second light-emitting unit and a second electrode arranged in sequence; the first light-emitting unit comprises a hole injection layer A, a hole transport layer A, a light-emitting layer A and a hole blocking layer A arranged in sequence; the hole blocking layer A is stacked with the connecting layer; the second light-emitting unit comprises an electron injection layer B, an electron transport layer B, a hole blocking layer B, a light-emitting layer B and a hole transport layer B arranged in sequence; the hole transport layer B is stacked with the connecting layer.

[0009] In the present invention, the stacked organic light-emitting device does not adopt the traditional stacked organic light-emitting device structure. Through a specific structural design, that is, the electron transport layer in the first light-emitting unit is removed, so that the hole blocking layer and the connecting layer in the first light-emitting unit are stacked, it is beneficial to reduce the voltage of the stacked organic light-emitting device and improve the efficiency and life of the stacked organic light-emitting device.

[0010] In some embodiments of the present invention, the connection layer includes a first N-type charge generation layer and a first P-type charge generation layer stacked in sequence, and the first P-type charge generation layer is stacked with the second light emitting unit.

[0011] In some embodiments of the present invention, the LUMO energy level of the first N-type charge generation layer and the LUMO energy level of the hole blocking layer A are each independently -3 to -2 eV, for example, -3 eV, -2.9 eV, -2.8 eV, -2.7 eV, -2.6 eV, -2.5 eV, -2.4 eV, -2.3 eV, -2.2 eV, -2.1 eV, -2 eV, etc.

[0012] In some embodiments of the present invention, the LUMO energy level difference between the first N-type charge generation layer and the hole blocking layer A is ≤0.5eV, for example, it can be 0.05eV, 0.06eV, 0.08eV, 0.1eV, 0.12eV, 0.14eV, 0.16eV, 0.18eV, 0.2eV, 0.22eV, 0.24eV, 0.26eV, 0.28eV, 0.3eV, 0.32eV, 0.34eV, 0.36eV, 0.38eV, 0.4eV, 0.42eV, 0.44eV, 0.46eV, 0.48eV, 0.5eV, etc.

[0013] In the present invention, on the basis of designing the device structure, that is, after removing the electron transport layer in the first light-emitting unit, a first N-type charge generation layer with a shallower LUMO energy level and a hole blocking layer A with a shallower LUMO energy level are further adopted, and the LUMO energy level difference between the two is controlled within the above-mentioned range, which can help reduce the voltage of the stacked organic light-emitting device.

[0014] In the present invention, the material of the first N-type charge generation layer includes a main material and a doping material, the mass ratio of the main material and the doping material is (95-99):(1-5), and the total amount of the two is 100%; the main material includes a phenanthroline compound, and the doping material includes metal Li or metal Yb.

[0015] In the present invention, the material of the first P-type charge generation layer includes a mixture of a hole transport layer material and PD in a mass ratio of (90-99):(1-10).

[0016] In the present invention, the thickness of the first N-type charge generation layer and the first P-type charge generation layer are independently 5 to 40 nm.

[0017] In the present invention, the material of the hole injection layer A comprises a mixture of a hole transport layer material and PD in a mass ratio of (95-99):(1-5).

[0018] In the present invention, the thickness of the hole injection layer A is 5 to 30 nm.

[0019] In the present invention, the materials of the hole transport layer A and the hole transport layer B are independently selected from the hole transport layer materials commonly used in the art, or the novel hole transport layer materials disclosed in patents and literatures, illustratively, including but not limited to N-phenylcarbazole, polyvinylcarbazole, 4,4-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (α-NPD), N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-biphenyl]-4,4′-diamine (TPD), 4,4′,4″-tri(carbazole-9-yl)triphenylamine (TCTA), 1,1-bis[4-[N,N-di-p-toluamino]phenyl]cyclohexane (TAPC), etc.

[0020] In the present invention, the thickness of the hole transport layer A and the hole transport layer B are independently 20 to 60 nm.

[0021] In the present invention, the light-emitting layer A and the light-emitting layer B each independently include a main material and a doping material, and the mass ratio of the main material to the doping material is (90-99): (1-10), and the main material includes but is not limited to 3-tert-butyl-9,10-di(2-naphthalene)anthracene (TBADN), 4,4',4"-tri(carbazole-9-yl)triphenylamine (TCTA), 4,4'-di(9-carbazole)biphenyl (CBP), poly(n-vinylcarbazole) (PVK), 9,10-di(naphthalene-2-yl)anthracene (ADN), distyrylarylene (DSA), bis(2-(2-hydroxyphenyl) ) benzothiazole) zinc (Zn(BTZ)2), etc.; the doping material includes a red light-emitting dopant, a blue light-emitting dopant or a green light-emitting dopant; the red light-emitting dopant includes but is not limited to PtOEP, Ir(piq)3, Btp2Ir(acac), etc.; the blue light-emitting agent includes but is not limited to 4,4′-bis(4-diphenylaminophenylvinyl)biphenyl (DPAVBi), 2,5,8,11-tetra-tert-butylperylene (TBPe), etc.; the green light-emitting dopant includes but is not limited to Ir(ppy)3, Ir(ppy)2(acac), Ir(mppy)3, etc.

[0022] In the present invention, the material of the electron injection layer B can be selected from commonly used electron injection layer materials in the art, or new electron injection layer materials disclosed in patents and literatures, illustratively including but not limited to metallic lithium, lithium fluoride or 8-hydroxyquinoline lithium.

[0023] In the present invention, the thickness of the electron injection layer B is 0.1-10 nm.

[0024] In the present invention, the material of the electron transport layer B is selected from the commonly used electron transport layer materials in the art, or the new electron transport layer materials disclosed in patents and literature, and illustratively include but are not limited to tris(8-hydroxyquinoline)aluminum (Alq3), tri(α-naphthyl)aluminum (Almq3), di(2,4-dichlorophenyl)acridine (DVPBi), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), triphenylaminotriazole (TAZ), 4,7-diphenyl-1,10-phenanthroline (Bphen), 2-(4-biphenyl)-5-(4-tert-butyl)phenyl-1,3,4-oxadiazole (PBD), polystyrene butadiene copolymer (PPBD), 2,5-di(1-naphthyl)-1,3,4-oxadiazole (BND), polypyrene (PV), polyether ketone (OXD), etc.

[0025] In the present invention, the thickness of the electron transport layer B is 10 to 80 nm.

[0026] In the present invention, the materials of the hole blocking layer A and the hole blocking layer B independently include at least one of 2-(4-biphenyl)-5-(4-tert-butyl)phenyl-1,3,4-oxadiazole (PBD), 8-hydroxyquinoline aluminum (Alq3), 2,5-di(1-naphthyl)-1,3,4-oxadiazole (BND), 4,7-diphenyl-1,10-phenanthroline (Bphen), 1,2,4-triazole derivatives (such as TAZ), N-arylbenzimidazole (such as TPBi) or quinoxaline derivatives (such as TPQ).

[0027] In the present invention, the thickness of the hole blocking layer A and the hole blocking layer B are independently 3 to 10 nm.

[0028] In some embodiments of the present invention, the second light-emitting unit includes an electron injection layer C, a charge generation layer, a hole blocking layer C, a light-emitting layer C and a hole transport layer C arranged in sequence; the hole transport layer C is stacked with a connecting layer.

[0029] In the present invention, in the second light-emitting unit, the charge generation layer is used to replace the electron transport layer, which can reduce the resistance of the device, thereby reducing the voltage of the stacked organic light-emitting device, and the stacked organic light-emitting device has equivalent or higher luminous efficiency and service life.

[0030] In the present invention, the electron transport layer is removed from the first light-emitting unit, and a first N-type charge generation layer with a shallower LUMO energy level and a hole blocking layer A with a shallower LUMO energy level are adopted, and the LUMO energy level difference between the two is controlled within a specific range; at the same time, in the second light-emitting unit, a charge generation layer is adopted to replace the electron transport layer, and the obtained stacked organic light-emitting device has a lower voltage and a higher efficiency.

[0031] In some embodiments of the present invention, the charge generation layer includes a second N-type charge generation layer and a second P-type charge generation layer stacked in sequence, and the second P-type charge generation layer is stacked with an electron injection layer C.

[0032] In some embodiments of the present invention, the LUMO energy levels of the second N-type charge generation layer and the hole blocking layer C are independently -3.2 to -1.8 eV, for example, -3.2 eV, -3.1 eV, -3 eV, -2.9 eV, -2.8 eV, -2.7 eV, -2.6 eV, -2.5 eV, -2.4 eV, -2.3 eV, -2.2 eV, -2.1 eV, -2 eV, -1.9 eV, -1.8 eV, etc.

[0033] In some embodiments of the present invention, the LUMO energy level difference between the second N-type charge generation layer and the hole blocking layer C is ≤0.5eV, for example, it can be 0.05eV, 0.06eV, 0.08eV, 0.1eV, 0.12eV, 0.14eV, 0.16eV, 0.18eV, 0.2eV, 0.22eV, 0.24eV, 0.26eV, 0.28eV, 0.3eV, 0.32eV, 0.34eV, 0.36eV, 0.38eV, 0.4eV, 0.42eV, 0.44eV, 0.46eV, 0.48eV, 0.5eV, etc., preferably ≤0.3eV.

[0034] In the present invention, when the charge generation layer is used to replace the electron transport layer in the second light-emitting unit, the LUMO energy levels of the second N-type charge generation layer and the hole blocking layer C are further controlled to be independently within the above range. At the same time, the LUMO energy level difference between the two is within the above range, which can further reduce the voltage of the stacked organic light-emitting device.

[0035] In the present invention, the material of the second N-type charge generation layer is selected from the same range as that of the first N-type charge generation layer; and the material of the hole blocking layer C is selected from the same range as that of the hole blocking layer A.

[0036] In the present invention, the material of the second P-type charge generation layer is selected from the same range as that of the first P-type charge generation layer.

[0037] In the present invention, the material and thickness of the electron injection layer C are selected from the same range as the electron injection layer B, and the two are the same or different; the material and thickness of the light-emitting layer C are selected from the same range as the light-emitting layer A and the light-emitting layer B, and the three are the same or different; the material and thickness of the hole transport layer C are selected from the same range as the hole transport layer A and the hole transport layer B, and the three are the same or different.

[0038] In the present invention, the first electrode is an anode, the anode comprises a conductive glass substrate, and the conductive glass substrate comprises at least one of indium tin oxide (ITO) conductive glass, indium zinc oxide (IZO) conductive glass or aluminum-doped zinc oxide (AZO) conductive glass.

[0039] In the present invention, the second electrode is a cathode, including a metal cathode; the material of the metal cathode includes at least one of Mg, Ag, and Al.

[0040] In some embodiments of the present invention, in the first light-emitting unit and the second light-emitting unit, a light-emitting auxiliary layer is independently disposed between the light-emitting layer and the hole transport layer.

[0041] In the present invention, the material of the light-emitting auxiliary layer includes but is not limited to aromatic amine compounds; the thickness of the light-emitting auxiliary layer is 2 to 100 nm.

[0042] In some embodiments of the present invention, a covering layer is further disposed on a side of the second electrode away from the second light-emitting unit.

[0043] In the present invention, the material of the covering layer includes but is not limited to at least one of triarylamine compounds, cyclic urea compounds, acyl structure compounds, dibenzothiophene compounds, dibenzofuran compounds, and carbazole compounds.

[0044] In the present invention, the thickness of the covering layer is 10 to 150 nm.

[0045] In a second aspect, the present invention provides a stacked organic light-emitting device, comprising a first electrode, a first light-emitting unit, a connecting layer, a second light-emitting unit and a second electrode arranged in sequence; the first light-emitting unit comprises a hole injection layer D, a hole transport layer D, a light-emitting layer D, a hole blocking layer D and an electron transport layer D arranged in sequence; the electron transport layer D is stacked with the connecting layer; the second light-emitting unit comprises an electron injection layer E, a charge generation layer, a hole blocking layer E, a light-emitting layer E and a hole transport layer E arranged in sequence; the hole transport layer E is stacked with the connecting layer.

[0046] In the present invention, the stacked organic light-emitting device provided in the second aspect can reduce the resistance of the device through a specific structural design, that is, a charge generation layer is used in the second light-emitting unit to replace the electron transport layer, thereby reducing the voltage of the stacked organic light-emitting device, and the stacked organic light-emitting device has equivalent or higher luminous efficiency and service life.

[0047] In the present invention, in the stacked organic light-emitting device provided in the second aspect, the first electrode is an anode, the anode includes a conductive glass substrate, the conductive glass substrate includes at least one of indium tin oxide (ITO) conductive glass, indium zinc oxide (IZO) conductive glass or aluminum-doped zinc oxide (AZO) conductive glass; the second electrode is a cathode, including a metal cathode; the material of the metal cathode includes at least one of Mg, Ag, Al, and Li; the thickness of the second electrode is 10 to 400 nm.

[0048] In the second aspect of the present invention, the stacked organic light-emitting device provided, the material of the hole injection layer D includes a mixture of hole transport layer material and PD in a mass ratio of (95-99):(1-5); the thickness of the hole injection layer D is 5-30nm.

[0049] In the present invention, in the stacked organic light-emitting device provided in the second aspect, the hole transport layer D and the hole transport layer E materials are independently selected from the hole transport layer materials commonly used in the art, illustratively, including but not limited to N-phenylcarbazole, polyvinylcarbazole, 4,4-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (α-NPD), N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-biphenyl]-4,4′-diamine (TPD), 4,4′,4″-tri(carbazole-9-yl)triphenylamine (TCTA), 1,1-bis[4-[N,N-di-p-toluylamino]phenyl]cyclohexane (TAPC), etc. The thickness of the hole transport layer D and the hole transport layer E are independently 20 to 60 nm.

[0050] In the present invention, in the stacked organic light-emitting device provided in the second aspect, the materials of the light-emitting layer D and the light-emitting layer E each independently include a main material and a doping material, and the types of the main material and the doping material and the mass ratio thereof are selected from the same range as that of the light-emitting layer A or the light-emitting layer B.

[0051] In the present invention, in the second aspect of the stacked organic light-emitting device, the materials of the hole blocking layer D and the hole blocking layer E independently include at least one of 2-(4-biphenyl)-5-(4-tert-butyl)phenyl-1,3,4-oxadiazole (PBD), 8-hydroxyquinoline aluminum (Alq3), 2,5-di(1-naphthyl)-1,3,4-oxadiazole (BND), 4,7-diphenyl-1,10-phenanthroline (Bphen), 1,2,4-triazole derivatives (such as TAZ), N-arylbenzimidazole (such as TPBi) or quinoxaline derivatives (such as TPQ). The thickness of the hole blocking layer D is 3 to 10 nm.

[0052] In the present invention, in the stacked organic light-emitting device provided in the second aspect, the material of the electron transport layer D is selected from the commonly used electron transport layer materials in the art, exemplarily including but not limited to tris(8-hydroxyquinoline)aluminum (Alq3), tris(α-naphthyl)aluminum (Almq3), di(2,4-dichlorophenyl)acridine (DVPBi), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), triphenylamine triazole (TAZ), 4,7-diphenyl-1,10-phenanthroline (Bphen), 2-(4-biphenyl)-5-(4-tert-butyl)phenyl-1,3,4-oxadiazole (PBD), polystyrene butadiene copolymer (PPBD), 2,5-di(1-naphthyl)-1,3,4-oxadiazole (BND), polypyrene (PV), polyether ketone (OXD), etc. The thickness of the electron transport layer D is 10 to 80 nm.

[0053] In the second aspect of the present invention, the stacked organic light-emitting device provided, the electron injection layer E material can be selected from commonly used electron injection layer materials in the art, illustratively including but not limited to metallic lithium, lithium fluoride or 8-hydroxyquinoline lithium, etc. The thickness of the electron injection layer E is 0.1 to 10 nm.

[0054] In some embodiments of the present invention, the stacked organic light-emitting device provided in the second aspect, the charge generation layer includes a second N-type charge generation layer and a second P-type charge generation layer stacked in sequence, and the second P-type charge generation layer is stacked with an electron injection layer E.

[0055] In some embodiments of the present invention, in the stacked organic light-emitting device provided in the second aspect, the LUMO energy levels of the second N-type charge generation layer and the hole blocking layer E are independently -3 to -2 eV, for example, -3 eV, -2.9 eV, -2.8 eV, -2.7 eV, -2.6 eV, -2.5 eV, -2.4 eV, -2.3 eV, -2.2 eV, -2.1 eV, -2 eV, etc.

[0056] In some embodiments of the present invention, the LUMO energy level difference between the second N-type charge generation layer and the hole blocking layer E is ≤0.5eV, for example, it can be 0.05eV, 0.06eV, 0.08eV, 0.1eV, 0.12eV, 0.14eV, 0.16eV, 0.18eV, 0.2eV, 0.22eV, 0.24eV, 0.26eV, 0.28eV, 0.3eV, 0.32eV, 0.34eV, 0.36eV, 0.38eV, 0.4eV, 0.42eV, 0.44eV, 0.46eV, 0.48eV, 0.5eV, etc., preferably ≤0.3eV.

[0057] In the present invention, when the second light-emitting unit adopts a charge generation layer to replace the electron transport layer, the LUMO energy levels of the second N-type charge generation layer and the hole blocking layer E are further controlled to be independently within the above range. At the same time, the LUMO energy level difference between the two is within the above range, which can further reduce the voltage of the stacked organic light-emitting device and improve the efficiency and life of the stacked organic light-emitting device.

[0058] In the present invention, the second aspect provides a stacked organic light-emitting device, wherein the material of the second N-type charge generating layer includes a main material and a doping material, the mass ratio of the main material to the doping material is (95-99):(1-5), and the total amount of the two is 100%; the main material includes a phenanthroline compound, and the doping material includes metal Li or metal Yb.

[0059] In the second aspect of the present invention, in the stacked organic light-emitting device provided, the material of the second P-type charge generation layer comprises a mixture of a hole transport layer material and PD in a mass ratio of (90-99):(1-10).

[0060] In some embodiments of the present invention, the first light-emitting unit includes a hole injection layer F, a hole transport layer F, a light-emitting layer F and a hole blocking layer F which are arranged in sequence; the hole blocking layer F is stacked with a connecting layer.

[0061] In the stacked organic light-emitting device provided in the second aspect of the present invention, the material and thickness of the hole injection layer F are selected from the same range as those of the hole injection layer D, and the two are the same or different.

[0062] In the stacked organic light-emitting device provided in the second aspect of the present invention, the material and thickness of the hole transport layer F are selected from the same range as those of the hole transport layer D, and the two are the same or different.

[0063] In the stacked organic light-emitting device provided in the second aspect of the present invention, the material and thickness of the light-emitting layer F are selected from the same range as those of the light-emitting layer D, and the two are the same or different.

[0064] In some embodiments of the present invention, the connection layer includes a first N-type charge generation layer and a first P-type charge generation layer stacked in sequence, and the first P-type charge generation layer is stacked with the second light emitting unit.

[0065] In the present invention, in the stacked organic light-emitting device provided in the second aspect, when the first light-emitting unit is selected from a hole injection layer D, a hole transport layer D, a light-emitting layer D, a hole blocking layer D and an electron transport layer D arranged in sequence, the material of the first N-type charge generation layer of the connecting layer is selected from the same range as that of the second N-type charge generation layer; and the first P-type charge generation layer is selected from the same range as that of the second P-type charge generation layer.

[0066] In the present invention, in the stacked organic light-emitting device provided in the second aspect, when the first light-emitting unit is selected from a hole injection layer F, a hole transport layer F, a light-emitting layer F and a hole blocking layer F arranged in sequence, the material and thickness of the first N-type charge generation layer are selected from the same range as the second N-type charge generation layer, and the two are the same or different; the first P-type charge generation layer is selected from the same range as the second P-type charge generation layer, and the two are the same or different.

[0067] In the stacked organic light-emitting device provided in the second aspect of the present invention, the material and thickness of the hole blocking layer F are selected from the same range as those of the hole blocking layer E, and the two are the same or different.

[0068] In some embodiments of the present invention, the LUMO energy levels of the first N-type charge generation layer and the hole blocking layer F are independently -3.2 to -1.8 eV, for example, -3.2 eV, -3.1 eV, -3 eV, -2.9 eV, -2.8 eV, -2.7 eV, -2.6 eV, -2.5 eV, -2.4 eV, -2.3 eV, -2.2 eV, -2.1 eV, -2 eV, -1.9 eV, -1.8 eV, etc.

[0069] In some embodiments of the present invention, the LUMO energy level difference between the first N-type charge generation layer and the hole blocking layer F is ≤0.5eV, for example, it can be 0.05eV, 0.06eV, 0.08eV, 0.1eV, 0.12eV, 0.14eV, 0.16eV, 0.18eV, 0.2eV, 0.22eV, 0.24eV, 0.26eV, 0.28eV, 0.3eV, 0.32eV, 0.34eV, 0.36eV, 0.38eV, 0.4eV, 0.42eV, 0.44eV, 0.46eV, 0.48eV, 0.5eV, etc., preferably ≤0.3eV.

[0070] In the present invention, the stacked organic light-emitting device provided in the second aspect can further reduce the voltage of the stacked organic light-emitting device by arranging a charge generation layer between the electron injection layer E and the hole blocking layer E in the second light-emitting unit, and at the same time, removing the electron transport layer of the first light-emitting unit, directly stacking the hole blocking layer F with the connecting layer, and controlling the first N-type charge generation layer and the hole blocking layer F to have a shallower LUMO energy level, and controlling the LUMO energy level difference between the two within a specific range.

[0071] In some embodiments of the present invention, in the first light-emitting unit and the second light-emitting unit, a light-emitting auxiliary layer is independently disposed between the light-emitting layer and the hole transport layer.

[0072] In the second aspect of the present invention, the laminated organic light-emitting device provided, the material of the light-emitting auxiliary layer includes but is not limited to at least one of triphenylamine compounds. The thickness of the light-emitting auxiliary layer is 2 to 100 nm.

[0073] In some embodiments of the present invention, a covering layer is further disposed on a side of the second electrode away from the second light-emitting unit.

[0074] In the second aspect of the present invention, the laminated organic light-emitting device provided, the material of the cover layer includes but is not limited to at least one of triarylamine compounds, cyclic urea compounds, acyl structure compounds, dibenzothiophene compounds, dibenzofuran compounds, and carbazole compounds. The thickness of the cover layer is 10 to 150 nm.

[0075] In the present invention, the preparation method of the stacked organic light-emitting device provided in the first aspect and the stacked organic light-emitting device provided in the second aspect can both be prepared by conventional methods in the art, including but not limited to evaporation. Exemplarily, the preparation method includes sequentially evaporating a first light-emitting unit, a connecting layer, a second light-emitting unit, and a second electrode on the surface of a first electrode to obtain the stacked organic light-emitting device.

[0076] In the present invention, before use, the first electrode comprises the steps of ultrasonically cleaning with detergent, deionized water, acetone, ethanol and isopropanol for 10 to 20 minutes respectively.

[0077] In a third aspect, the present invention provides a display device, comprising the stacked organic light emitting device according to the first aspect and / or the stacked organic light emitting device according to the second aspect.

[0078] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0079] Compared with the prior art, the present invention has the following beneficial effects:

[0080] The stacked organic light-emitting device provided by the present invention can effectively reduce the voltage of the stacked organic light-emitting device through a specific structural design, that is, removing the electron transport layer in the first light-emitting unit and / or replacing the electron transport layer in the second light-emitting unit with a charge generation layer. At the same time, it can also ensure that the stacked organic light-emitting device has equivalent or higher efficiency and lifespan. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 A schematic diagram of the structure of a stacked organic light-emitting device provided in Example 1 of the present invention;

[0082] Among them, 101-covering layer; 102-cathode; 103-electron injection layer; 104-second electron transport layer; 105-second hole blocking layer; 106-second light-emitting layer; 107-second light-emitting auxiliary layer; 108-second hole transport layer; 109-P-type charge generation layer; 110-N-type charge generation layer; 111-first hole blocking layer; 112-first light-emitting layer; 113-first light-emitting auxiliary layer; 114-first hole transport layer; 115-hole injection layer; 116-anode.

[0083] Figure 2 A schematic diagram of the structure of a stacked organic light-emitting device provided in Example 2 of the present invention;

[0084] Among them, 201-covering layer; 202-cathode; 203-electron injection layer; 204-second P-type charge generation layer; 205-second N-type charge generation layer; 206-second hole blocking layer; 207-second light-emitting layer; 208-second light-emitting auxiliary layer; 209-second hole transport layer; 210-first P-type charge generation layer; 211-first N-type charge generation layer; 212-first electron transport layer; 213-first hole blocking layer; 214-first light-emitting layer; 215-first light-emitting auxiliary layer; 216-first hole transport layer; 217-hole injection layer; 218-anode.

[0085] Figure 3 A schematic diagram of the structure of a stacked organic light-emitting device provided in Example 3 of the present invention;

[0086] Among them, 301-covering layer; 302-cathode; 303-electron injection layer; 304-second P-type charge generation layer; 305-second N-type charge generation layer; 306-second hole blocking layer; 307-second light-emitting layer; 308-second light-emitting auxiliary layer; 309-second hole transport layer; 310-first P-type charge generation layer; 311-first N-type charge generation layer; 312-first hole blocking layer; 313-first light-emitting layer; 314-first light-emitting auxiliary layer; 315-first hole transport layer; 316-hole injection layer; 317-anode. DETAILED DESCRIPTION

[0087] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0088] Example 1

[0089] This embodiment provides a stacked organic light emitting device, the structural schematic diagram of which is shown in FIG. Figure 1As shown, it includes a capping layer 101 (material: CBP; thickness: 70nm), a cathode 102 (material: Ag; thickness: 12nm), an electron injection layer 103 (material: 8-hydroxyquinoline lithium; thickness: 1.5nm), a second electron transport layer 104 (material: Alq3; thickness: 30nm), a second hole blocking layer 105 (material: PBD; thickness: 5nm), a second light-emitting layer 106 (material: TBADN:Ir(piq)3 mass ratio = 97:3; thickness: 45nm), a second light-emitting auxiliary layer 107 (material: selected from the compound HT47 disclosed in CN108821985A; thickness: 50nm), a second hole transport layer 108 (material: α-NPD; thickness: 50nm), a P-type charge generation layer 109 (material: α-NPD:PD mass ratio = 9 2:8; thickness: 10nm), an N-type charge generation layer 110 (material: Yb:4,7-diphenyl-1,10-phenanthroline mass ratio = 3:97; thickness: 20nm;), a first hole blocking layer 111 (material: 4,7-diphenyl-1,10-phenanthroline; thickness: 5nm;), a first light-emitting layer 112 (material: TBADN:Ir(piq)3 mass ratio = 97:3; thickness: 45nm), a first light-emitting auxiliary layer 113 (material: compound HT47 selected from CN108821985A disclosed; thickness: 20nm), a first hole transport layer 114 (material: TPD; thickness: 25nm), a hole injection layer 115 (material: TPD:PD mass ratio = 98:2; thickness: 10nm) and an anode 116 (material: ITO conductive glass; thickness: 14nm).

[0090] This embodiment provides a method for preparing a stacked organic light-emitting device, which specifically includes the following steps:

[0091] The ITO conductive glass is subjected to photolithography treatment, and is ultrasonically cleaned with detergent, deionized water, acetone, ethanol, and isopropanol for 15 minutes respectively, and then the ITO conductive glass is treated with oxygen plasma for 5 minutes at a power of 30W. Then, a hole injection layer material, a first hole transport layer material, a first light-emitting auxiliary layer material, a first light-emitting layer material, a first hole blocking layer material, an N-type charge generation layer material, a P-type charge generation layer material, a second hole transport layer material, a second light-emitting auxiliary layer material, a second light-emitting layer material, a second hole blocking layer material, a second electron transport layer material, an electron injection layer material, a cathode material, and a covering layer material are sequentially evaporated on the surface of the treated ITO conductive glass to obtain the stacked organic light-emitting device.

[0092] Example 2

[0093] This embodiment provides a stacked organic light emitting device, the structural schematic diagram of which is shown in FIG. Figure 2As shown, it includes a capping layer 201 (material: CBP; thickness: 70nm), a cathode 202 (material: Ag; thickness: 12nm), an electron injection layer 203 (material: 8-hydroxyquinoline lithium; thickness: 1.5nm), a second P-type charge generation layer 204 (material: α-NPD:PD mass ratio = 92:8; thickness: 10nm), a second N-type charge generation layer 205 (material: Yb:4,7-diphenyl-1,10-phenanthroline mass ratio = 3: 97; thickness: 20nm), a second hole blocking layer 206 (material: 4,7-diphenyl-1,10-phenanthroline; thickness: 5nm), a second light-emitting layer 207 (material: TBADN:Ir(piq)3 mass ratio = 97:3; thickness: 45nm), a second light-emitting auxiliary layer 208 (material: selected from the compound HT47 disclosed in CN108821985A; thickness: 50nm), a second hole transport layer 209 (material: α-NPD; thickness: 5 0nm), a first P-type charge generation layer 210 (material: α-NPD:PD mass ratio = 92:8; thickness: 10nm), a first N-type charge generation layer 211 (material: Yb:4,7-diphenyl-1,10-phenanthroline mass ratio = 3:97; thickness: 10nm), a first electron transport layer 212 (material: Alq3; thickness: 10nm), a first hole blocking layer 213 (material: PBD; thickness: 5nm), a first light-emitting layer 214 (material: T BADN:Ir(piq)3 mass ratio = 97:3; thickness: 45nm), a first light-emitting auxiliary layer 215 (material: selected from the compound HT47 disclosed in CN108821985A; thickness: 20nm), a first hole transport layer 216 (material: TPD; thickness: 25nm), a hole injection layer 217 (material: TPD:PD mass ratio = 98:2; thickness: 10nm) and an anode 218 (material: ITO conductive glass; thickness: 14nm).

[0094] This embodiment provides a method for preparing a stacked organic light-emitting device, and the specific steps are the same as those in Embodiment 1.

[0095] Example 3

[0096] This embodiment provides a stacked organic light emitting device, the structural schematic diagram of which is shown in FIG. Figure 3As shown, it includes a capping layer 301 (material: CBP; thickness: 70nm), a cathode 302 (material: Ag; thickness: 12nm), an electron injection layer 303 (material: 8-hydroxyquinoline lithium; thickness: 1.5nm), a second P-type charge generation layer 304 (material: α-NPD:PD mass ratio = 92:8; thickness: 10nm), a second N-type charge generation layer 305 (material: Yb:4,7-diphenyl-1,10-phenanthroline mass ratio = 3 :97; thickness: 20nm), a second hole blocking layer 306 (material: 4,7-diphenyl-1,10-phenanthroline; thickness: 5nm), a second light-emitting layer 307 (material: TBADN:Ir(piq)3=97:3; thickness: 45nm), a second light-emitting auxiliary layer 308 (material: selected from the compound HT47 disclosed in CN108821985A; thickness: 50nm), a second hole transport layer 309 (material: α-NPD; thickness: 50 nm), a first P-type charge generation layer 310 (material: α-NPD:PD mass ratio = 92:8; thickness: 10 nm), a first N-type charge generation layer 311 (material: Yb:4,7-diphenyl-1,10-phenanthroline mass ratio = 3:97; thickness: 20 nm), a first hole blocking layer 312 (material: 4,7-diphenyl-1,10-phenanthroline; thickness: 5 nm; LUMO energy level is -3.0 eV), a first light-emitting layer 313 (material: TB ADN:Ir(piq)3 mass ratio = 97:3; thickness: 45nm), a first light-emitting auxiliary layer 314 (material: compound HT47 selected from CN108821985A; thickness: 20nm), a first hole transport layer 315 (material: TPD; thickness: 25nm), a hole injection layer 316 (material: TPD:PD mass ratio = 98:2; thickness: 10nm) and an anode 317 (material: ITO conductive glass; thickness: 14nm).

[0097] This embodiment provides a method for preparing a stacked organic light-emitting device, and the specific steps are the same as those in Embodiment 1.

[0098] Example 4

[0099] This embodiment provides a stacked organic light-emitting device, which is different from the first embodiment only in that the material of the first hole blocking layer is BAlq, and other materials, structures and preparation methods are the same as those of the first embodiment.

[0100] Example 5

[0101] This embodiment provides a stacked organic light-emitting device, which is different from the second embodiment only in that the material of the second hole blocking layer is BAlq, and other materials, structures and preparation methods are the same as those of the second embodiment.

[0102] Comparative Example 1

[0103] This comparative example provides a stacked organic light-emitting device, which differs from Example 2 only in that the second P-type charge generation layer 204 and the second N-type charge generation layer 205 are replaced by a second electron transport layer (material: Alq3; thickness: 30nm), and other materials, structures and preparation methods are the same as those in Example 2.

[0104] Comparative Example 2

[0105] This comparative example provides a stacked organic light-emitting device, which differs from Example 1 only in that the thickness of the N-type charge generation layer 110 is 10 nm, and a first electron transport layer (material: Alq3; thickness: 10 nm) is further provided between the N-type charge generation layer 110 and the first hole blocking layer 111. Other materials, structures and preparation methods are the same as those in Example 1.

[0106] The performance of the stacked organic light-emitting device obtained above was evaluated:

[0107] The current of the stacked organic light-emitting device at different voltages was tested using a Keithley 2365A digital nanovoltmeter, and the current was then divided by the luminous area to obtain the current density of the stacked organic light-emitting device at different voltages. The brightness and radiant energy flux density of the stacked organic light-emitting device at different voltages were tested using a Konicaminolta CS-2000 spectroradiometer. Based on the current density and brightness of the stacked organic light-emitting device at different voltages, the current density (10 mA / cm 2 ) and CE value (current efficiency CE, unit cd / A); the normal temperature life LT95 (at 25°C, 30mA / cm 2 test conditions); taking the test values ​​of V, CE, and LT95@25°C of the stacked organic light-emitting device provided in Comparative Example 1 as ref, ie 100%, the ratio of the performance test values ​​of other devices to the test values ​​of the device in Comparative Example 1 was calculated.

[0108] The specific test results are shown in Table 1:

[0109] Table 1

[0110]

[0111]

[0112] In summary, the stacked organic light-emitting device provided by the present invention can effectively reduce the voltage of the stacked organic light-emitting device through a specific structural design, and at the same time, can also ensure that the stacked organic light-emitting device has equivalent or higher efficiency and lifespan.

[0113] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A stacked organic light-emitting device, characterized in that: The stacked organic light-emitting device comprises a first electrode, a first light-emitting unit, a connecting layer, a second light-emitting unit and a second electrode which are arranged in sequence; The first light-emitting unit comprises a hole injection layer A, a hole transport layer A, a light-emitting layer A and a hole blocking layer A arranged in sequence; the hole blocking layer A is stacked with a connecting layer; The second light-emitting unit includes an electron injection layer B, an electron transport layer B, a hole blocking layer B, a light-emitting layer B and a hole transport layer B arranged in sequence; the hole transport layer B is stacked with a connecting layer.

2. The stacked organic light-emitting device according to claim 1, characterized in that: The connection layer includes a first N-type charge generation layer and a first P-type charge generation layer stacked in sequence, and the first P-type charge generation layer is stacked with the second light emitting unit.

3. The stacked organic light-emitting device according to claim 2, characterized in that: The LUMO energy level of the first N-type charge generation layer and the LUMO energy level of the hole blocking layer A are each independently -3 to -2 eV.

4. The stacked organic light-emitting device according to claim 3, characterized in that: The LUMO energy level difference between the first N-type charge generation layer and the hole blocking layer A is ≤0.5 eV.

5. The stacked organic light-emitting device according to claim 1, characterized in that: The second light-emitting unit includes an electron injection layer C, a charge generation layer, a hole blocking layer C, a light-emitting layer C and a hole transport layer C which are arranged in sequence; the hole transport layer C is stacked with a connecting layer.

6. The stacked organic light emitting device according to claim 5, characterized in that: The charge generation layer includes a second N-type charge generation layer and a second P-type charge generation layer stacked in sequence, and the second P-type charge generation layer is stacked with an electron injection layer C.

7. The stacked organic light emitting device according to claim 6, characterized in that: The LUMO energy levels of the second N-type charge generation layer and the hole blocking layer C are independently -3.2 to -1.8 eV.

8. The stacked organic light emitting device according to claim 7, characterized in that: The LUMO energy level difference between the second N-type charge generation layer and the hole blocking layer C is ≤0.5 eV.

9. The stacked organic light emitting device according to claim 1, characterized in that: In the first light-emitting unit and the second light-emitting unit, a light-emitting auxiliary layer is independently disposed between the light-emitting layer and the hole transport layer.

10. The stacked organic light emitting device according to claim 1, characterized in that: A covering layer is further disposed on a side of the second electrode away from the second light emitting unit.

11. A stacked organic light-emitting device, characterized in that: The stacked organic light-emitting device comprises a first electrode, a first light-emitting unit, a connecting layer, a second light-emitting unit and a second electrode which are arranged in sequence; The first light-emitting unit comprises a hole injection layer D, a hole transport layer D, a light-emitting layer D, a hole blocking layer D and an electron transport layer D arranged in sequence; the electron transport layer D is stacked with a connecting layer; The second light-emitting unit includes an electron injection layer E, a charge generation layer, a hole blocking layer E, a light-emitting layer E and a hole transport layer E which are arranged in sequence; the hole transport layer E is stacked with a connecting layer.

12. The stacked organic light emitting device according to claim 11, characterized in that: The charge generation layer includes a second N-type charge generation layer and a second P-type charge generation layer stacked in sequence, and the second P-type charge generation layer is stacked with an electron injection layer E.

13. The stacked organic light emitting device according to claim 12, characterized in that: The LUMO energy levels of the second N-type charge generation layer and the hole blocking layer E are independently -3 to -2 eV.

14. The stacked organic light emitting device according to claim 13, characterized in that: The LUMO energy level difference between the second N-type charge generation layer and the hole blocking layer E is ≤0.5 eV.

15. The stacked organic light emitting device according to claim 11, characterized in that: The first light-emitting unit includes a hole injection layer F, a hole transport layer F, a light-emitting layer F and a hole blocking layer F which are arranged in sequence; the hole blocking layer F is stacked with a connecting layer.

16. The stacked organic light emitting device according to claim 15, characterized in that: The connection layer includes a first N-type charge generation layer and a first P-type charge generation layer stacked in sequence, and the first P-type charge generation layer is stacked with the second light emitting unit.

17. The stacked organic light emitting device according to claim 16, characterized in that: The LUMO energy levels of the first N-type charge generation layer and the hole blocking layer F are independently -3.2 to -1.8 eV.

18. The stacked organic light emitting device according to claim 17, characterized in that: The LUMO energy level difference between the first N-type charge generation layer and the hole blocking layer F is ≤0.5 eV.

19. The stacked organic light emitting device according to claim 11, characterized in that: In the first light-emitting unit and the second light-emitting unit, a light-emitting auxiliary layer is independently disposed between the light-emitting layer and the hole transport layer.

20. The stacked organic light emitting device according to claim 11, characterized in that: A covering layer is further disposed on a side of the second electrode away from the second light emitting unit.

21. A display device, characterized in that: The display device comprises the stacked organic light emitting device according to any one of claims 1 to 10 and / or the stacked organic light emitting device according to any one of claims 11 to 20.

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