Blue light laminated organic light-emitting device and preparation method thereof

Abstract

The invention discloses a blue light laminated organic light-emitting device and a preparation method thereof. The blue light laminated organic light-emitting device comprises at least two blue light-emitting units which are connected in series through a charge generation layer, and each electroluminescent unit internally comprises a sandwich type core constraint structure of an electron blocking layer / blue light emitting layer / hole blocking layer. The unique double-side constraint structure can efficiently limit carriers and excitons in emission layers of respective light-emitting units, so that non-radiation quenching of the excitons on a functional layer interface and a charge generation layer interface is greatly inhibited. In addition, rare earth metal is preferably adopted as an n-type doping agent in the charge generation layer, so that the operation stability of the charge generation layer is improved. The laminated device structure cooperatively solves the technical problems that an existing blue light OLED is low in efficiency and short in service life, and an extra attenuation path exists in a laminated device, and excellent luminous efficiency, extremely low efficiency roll-off and excellent working stability are achieved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor light-emitting device technology, and in particular to a blue light-emitting multilayer organic electroluminescent device and its preparation method. Background Technology

[0002] Organic light-emitting diode (OLED) technology has become the mainstream of next-generation display and lighting technologies due to its outstanding advantages such as self-emission, high contrast, wide viewing angle, fast response, and flexibility. In full-color display applications, OLED panels present rich colors through the combination of red (R), green (G), and blue (B) sub-pixels. Similarly, in white light lighting applications, blue light emitting units are usually mixed with other colors of light (such as yellow light or a combination of red and green light) to produce high-quality white light. Therefore, the performance of blue OLEDs, including their luminous efficiency, lifespan, and color purity, directly determines the power consumption, reliability, and color performance of the entire display panel or lighting product.

[0003] However, the development of blue OLEDs has always faced the severe challenge known as "The Blue Problem." The root cause lies in the high energy of blue photons, which is comparable to the bond dissociation energy of chemical bonds in many organic materials. This makes the blue light emitting material and its surrounding functional layer materials highly susceptible to irreversible chemical degradation under electrical stress, leading to rapid brightness decay and a much shorter lifespan compared to red and green OLEDs.

[0004] Besides the limitations of the materials themselves, device structure design is equally crucial for solving the "blue light problem." In traditional single-emitting-unit devices, the imbalance between carrier (holes and electrons) injection and transport is a key factor leading to decreased efficiency and lifetime. This imbalance causes the exciton recombination region to shift towards one side of the transport layer, resulting not only in exciton quenching in the non-emitting layer but also accelerated degradation of the transport layer material due to bombardment by high-energy excitons. In addition to the limitations of the materials themselves, device structure design is also critical to the performance of blue OLEDs. In traditional device structures, the imbalance between carrier (holes and electrons) injection and transport is a common problem. For example, if the injection and transport capabilities of holes are much stronger than those of electrons, the exciton recombination region will shift towards the electron transport layer. This not only causes some excitons to annihilate in the non-emitting layer, resulting in efficiency loss, but more seriously, high-energy blue excitons will directly bombard the relatively unstable electron transport layer material, accelerating its degradation and becoming one of the main causes of device failure. The reverse is also true. Furthermore, exciton leakage from the luminescent layer to the adjacent transport layer, followed by quenching at the interface, is also a significant factor contributing to decreased device efficiency and lifetime. Therefore, relying solely on the development of novel luminescent materials is insufficient to completely solve the "blue light problem."

[0005] To address the lifespan bottleneck of blue light-emitting diodes (OLEDs) structurally, stacked OLED architectures have emerged. Stacked devices connect two or more independent electroluminescent (EL) cells in series vertically via a charge generation layer (CGL). Their core advantage lies in achieving the same brightness as single-cell devices, requiring only 1 / N of the current density flowing through each EL cell (where N is the number of EL cells). Since device degradation is closely related to current density, this significant reduction in current density can increase the theoretical lifespan of the device by N times or more, which is particularly attractive for blue OLEDs, which inherently have a short lifespan.

[0006] In summary, while existing technologies recognize the potential of stacked structures to improve the lifespan of blue OLEDs, simply stacking traditional blue EL units cannot completely solve the problem and may even introduce new instabilities.

[0007] Therefore, it is necessary to develop a blue light-emitting multilayer organic electroluminescent device and its fabrication method to solve the above problems. Summary of the Invention

[0008] The purpose of this invention is to design a blue light-emitting multilayer organic electroluminescent device and its fabrication method in order to solve the above-mentioned problems.

[0009] The present invention achieves the above objectives through the following technical solutions: A blue-light-emitting stacked organic electroluminescent device includes an anode, a cathode, a first blue electroluminescent unit disposed between the anode and the cathode, a second blue electroluminescent unit, and a charge-generating layer disposed between the first and second blue electroluminescent units. Each of the first and second blue electroluminescent units includes, sequentially disposed, an electron-blocking layer, a blue light-emitting layer, and a hole-blocking layer. Both the first and second blue electroluminescent units contain: a. an electron-blocking layer (EBL); b. an emissive layer (EML); and c. a hole-blocking layer (HBL). This "EBL / EML / HBL" double-sided blocking "sandwich" structure deployed within each EL unit constitutes the key to this invention. It not only precisely confines charge carriers (electrons and holes) within their respective EMLs to achieve efficient recombination, but more importantly, it also completely encloses the resulting high-energy blue excitons within the EMLs. This structure provides dual protection in multilayer devices: on the one hand, it prevents excitons from leaking into adjacent transport layers; on the other hand, it physically isolates the EML from the CGL, effectively preventing exciton quenching at the CGL interface, and also preventing possible contamination of the EML by mobile ions in the CGL.

[0010] Specifically, the charge generation layer comprises an n-type doped charge generation layer and a p-type doped charge generation layer; the n-type doped charge generation layer comprises an electron transport host material and an n-type dopant, wherein the n-type dopant is a rare earth metal or a compound thereof.

[0011] Specifically, an electron injection layer is disposed below the cathode, and the electron injection layer contains rare earth metals or their compounds.

[0012] Specifically, a p-type doped hole injection layer is also included between the anode and the first blue electroluminescent unit.

[0013] Specifically, an optical cover layer is disposed above the cathode, which together with other layers of the device constitutes an optical microcavity structure.

[0014] Specifically, the blue light emitting layer comprises a host material and a blue light emitting dopant material, wherein the blue light emitting dopant material is selected from at least one of blue light fluorescent materials, blue light phosphorescent materials, or blue light thermally activated delayed fluorescent materials.

[0015] Specifically, the lowest unoccupied molecular orbital energy level of the material used in the electron blocking layer is higher than the lowest unoccupied molecular orbital energy level of the host material in the adjacent blue light emitting layer; the highest occupied molecular orbital energy level of the material used in the hole blocking layer is lower than the highest occupied molecular orbital energy level of the host material in the adjacent blue light emitting layer.

[0016] Specifically, the anode layer is a transparent conductive oxide.

[0017] Specifically, the cathode has a thickness of 5 nm to 15 nm; the electron blocking layer has a thickness of 3 nm to 8 nm; and the optical cladding layer has a thickness of 60 nm to 70 nm.

[0018] A method for fabricating a blue multilayer organic electroluminescent device, characterized in that it includes, under a high vacuum environment, sequentially depositing an anode, a hole injection layer, a first blue electroluminescent unit, a charge generation layer, a second blue electroluminescent unit, an electron injection layer, a cathode, and an optical capping layer on a substrate through a vacuum thermal evaporation process.

[0019] The beneficial effects of this invention are: Lifetime multiplication effect: By adopting a stacked structure of dual light-emitting units, the operating current density of each unit is halved when achieving the same brightness, thereby greatly delaying the intrinsic aging process of blue light materials and multiplying the operating life of the device.

[0020] Superior exciton and carrier management: The innovative "EBL / EML / HBL" core constraint structure within each EL cell achieves dual-sided confinement of both carriers and excitons. This ensures that exciton recombination occurs entirely in the central region of the EML, maximizing the radiative recombination probability, while fundamentally preventing exciton leakage and quenching to the CGL and other functional layers. This is key to achieving high efficiency and suppressing efficiency roll-off.

[0021] Enhanced interface stability: By selecting rare earth metals (such as Yb) with higher stability and lower diffusion as n-type dopants for CGL, and combining the physical isolation effect of the “EBL / EML / HBL” structure, this invention effectively solves the interface contamination and performance degradation problems caused by dopant migration in traditional stacked devices, and significantly improves the long-term operational reliability of the device. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0023] Figure 1 This is a schematic diagram of the structure of a blue organic light-emitting device in one embodiment of the present invention.

[0024] Figure 2 This is a comparison curve of the brightness (cd / m²) - external quantum efficiency (EQE) characteristics of the device in the embodiment of the present invention and the device in the comparative embodiment.

[0025] The diagram is labeled as follows: 1-Anode, 2-First hole injection layer, 3-First hole transport layer, 4-Intermediate layer, 5-First electron blocking layer, 6-First blue light emitting layer, 7-Hole blocking layer, 8-First electron transport layer, 9-n-type charge generation layer, 10-p-type charge generation layer, 11-Second hole transport layer, 12-Intermediate layer, 13-Second electron blocking layer, 14-Second blue light emitting layer, 15-Second hole blocking layer, 16-Second electron transport layer, 17-Electron injection layer, 18-Cathode, 19-Optical capping layer. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0028] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0029] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0030] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0031] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0032] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] Reference Figure 1 The present invention discloses a blue light-emitting multilayer organic electroluminescent device, the typical structure of which, from bottom to top, includes: an anode 1, a first hole injection layer 2, a first hole transport layer 3, an intermediate layer 4, a first electron blocking layer 5, a first blue light emitting layer 6, a hole blocking layer 7, a first electron transport layer 8, an n-type charge generation layer 9, a p-type charge generation layer 10, a second hole transport layer 11, an intermediate layer 12, a second electron blocking layer 13, a second blue light emitting layer 14, a second hole blocking layer 15, a second electron transport layer 16, an electron injection layer 17, a cathode 18, and an optical capping layer 19.

[0034] Anode 1: Used for hole injection, typically made of transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), whose work function is processed to match the hole transport layer energy level. Substrate: Serves as the mechanical support of the device, typically made of transparent material such as glass or flexible polymers (e.g., polyimide PI, polyethylene terephthalate PET, etc.).

[0035] First hole injection layer 2 / first hole transport layer 3: This layer is adjacent to the anode 1. To reduce the potential barrier for injecting holes from the anode, a p-type doped hole injection layer (HIL) (first hole injection layer 2) is placed adjacent to the anode, for example, the host material is doped with 2% p-type dopant. Following this is the first hole transport layer (HTL1), which is responsible for efficiently transporting holes to subsequent functional layers.

[0036] Intermediate layers 4 and 12: The materials for these layers must meet two conditions: 1) Their LUMO energy level must be significantly higher than that of the blue light emitting layer and the main material, thus forming a high potential barrier for electrons and effectively preventing electrons from passing through the emitting layer and entering the hole transport layer; 2) Their triplet energy level (T1) must be higher than the T1 energy level of the blue light emitting doped material to prevent reverse energy transfer quenching of luminescent excitons. Therefore, this layer plays a dual role of efficient electron blocking and exciton confinement.

[0037] First electron blocking layer 5: This layer material has a high lowest unoccupied molecular orbital (LUMO) energy level, forming a high barrier to electrons and effectively preventing electrons from leaking from emission layer 1 to HTL1.

[0038] The first blue light emitting layer 6 and the second blue light emitting layer 15 are composed of a host material (EB) and a blue light dopant material (BD), with a doping concentration of, for example, 2%. Charge carriers recombine here to form excitons, which emit light through the dopant. The dopant can be a highly efficient fluorescent, phosphorescent, or TADF material.

[0039] First hole blocking layer 7: This layer material has a low highest occupied molecular orbital (HOMO) energy level, forming a high barrier to holes, effectively preventing holes from passing through the emitter layer 1 into the subsequent electron transport layer 1, and finally reaching CGL.

[0040] First electron transport layer 8: Responsible for efficiently transporting electrons from CGL to EML1.

[0041] Charge Generation Layer (CGL): The CGL is the core component connecting two EL units. Its function is to generate electron-hole pairs under an applied electric field, acting like an internal virtual electrode. It consists of two parts: The n-type charge generation layer (N-CGL) 9 is formed by co-evaporation of the electron transport host material and an n-type dopant. In a preferred embodiment of the present invention, the n-type dopant is ytterbium (Yb), with a doping concentration of, for example, 3%. As an n-type dopant, Yb has more stable physicochemical properties and a lower diffusion coefficient than commonly used Li or Cs, which helps to improve the overall operational stability of the device.

[0042] p-type charge generation layer (P-CGL) 10: adjacent to N-CGL, formed by co-evaporation of hole transport host material and p-type dopant, with a doping concentration of, for example, 5%.

[0043] Second hole transport layer 11: responsible for efficiently transmitting holes from CGL to EML2.

[0044] Second electron blocking layer 13: This layer material has a high lowest unoccupied molecular orbital (LUMO) energy level, forming a high barrier to electrons and effectively preventing electrons from leaking from the emission layer 2 to HTL2.

[0045] Second electron transport layer 16: responsible for efficiently transporting electrons from the cathode assembly to EML2.

[0046] Electron injection layer 17: A very thin layer of low work function material used to reduce the electron injection barrier from the cathode to ETL2.

[0047] Cathode 18: Typically a low work function metal or alloy used for electron injection. For top-emitting devices, this layer is usually translucent.

[0048] Optical capping layer 19: An organic or inorganic material with a specific refractive index and thickness deposited on the cathode. Together with the anode and other internal layers, it forms an optical microcavity, which can enhance the light output intensity of a specific wavelength (i.e., blue light) in the device normal direction and compress the emission spectrum, thereby improving light extraction efficiency and obtaining purer blue light color coordinates.

[0049] Material selection: The device structure of this invention has broad material applicability. To achieve efficient blue light emission, this invention provides a preferred material combination, while also listing other feasible material options to reflect the breadth of the invention's scope.

[0050]

[0051] Table 1: Example Materials for Each Functional Layer of the Device A method for fabricating a blue light-emitting multilayer organic electroluminescent device includes the following steps: 1. Clean the substrate, which consists of a transparent glass substrate and a transparent conductive anode ITO, in the following order: cleaning agent, deionized water, acetone, isopropanol, and anhydrous ethanol. After cleaning, dry it with nitrogen gas. 2. Ultraviolet light irradiation treatment of the substrate; 3. Place the processed substrate in a high-vacuum evaporation chamber, where the vacuum level reaches 10. -6 The organic thin film is prepared in sequence according to the device structure: hole injection layer, hole transport layer, intermediate layer, electron blocking layer, first hole blocking layer, first electron transport layer, n-type charge generation layer, p-type charge generation layer, second hole transport layer, intermediate layer, electron blocking layer, second hole blocking layer, second electron transport layer, electron injection layer, cathode, and optical capping layer.

[0052] Comparative Example: To further illustrate the technical effects of this invention, specific device fabrication and performance testing data are provided below. All devices were fabricated under ultra-high vacuum (substrate vacuum better than 10). -6 The film is prepared in a Pa) evaporation system, and the thickness of each layer and the evaporation rate are controlled by a film thickness monitor.

[0053] Comparative Example 1: Blue fluorescent OLED with conventional structure To establish a performance benchmark, a conventional blue OLED structure without the core features of this invention (i.e., the stacked structure and the "EBL / EML / HBL" double-sided blocking "sandwich" structure) was fabricated. Device structure: ITO / TAPC:5%MoO3 (100Å) / TAPC (300Å) / mCP:10%FIrpic (200Å) / TPBi (400Å) / Yb (10Å) / Mg:Ag (120Å). Wherein, ITO is the anode, TAPC:5%MoO3 is the hole injection layer, TAPC is the hole transport layer, mCP:10%FIrpic is the blue light emitting layer, TPBi is the electron transport layer, and Yb / Mg:Ag is the composite cathode. Example 1 of this invention (preferred embodiment): OLED of the present invention using TADF emitting material. Comparative Example 2: Blue stacked OLED without core feature structure This embodiment employs a stacked structure, but each electroluminescent unit lacks the crucial "EBL / EML / HBL" core constraint structure of this invention, which is used to demonstrate the importance of this constraint structure for improving efficiency and stability. Device structure: ITO / HIL / HTL1 / EML1 / ETL1 / CGL / HTL2 / EML2 / ETL2 / EIL / cathode / CAP. Specifically: ITO / TAPC:2%MoO3(100Å) / TAPC(250Å) / mCP:10%FIrpic(200Å) / TPBi(150Å) / TPBi:3%Yb(100Å) / TAPC: 5%MoO3(100Å) / TAPC(450Å) / mCP:10%FIrpic(200Å) / TPBi(330Å) / Yb(10Å) / Mg:Ag(120Å) / TAPC(650Å).

[0054] Comparative Example 3 (Invention): Blue Stacked OLED that fully embodies the structure of the present invention This embodiment fully embodies all the core technical features of the present invention, including the stacked architecture, the "EBL / EML / HBL" core constraint structure within each light-emitting unit, and the use of rare-earth metal Yb as the dopant for N-CGL. Device structure: ITO(1500Å) / TAPC:2%MoO3(100Å) / TAPC(200Å) / mCP(50Å) / mCP:10%FIrpic(200Å) / TPBi(50Å) / TPBi(100Å) / TPBi:3%Yb(100Å) / TAPC :5%MoO3(100Å) / TAPC(400Å) / mCP(50Å) / mCP:10%FIrpic(200Å) / TPBi(50Å) / TPBi(280Å) / Yb(10Å) / Mg:Ag(120Å,9:1) / TAPC(650Å).

[0055] Performance Data and Analysis The photoelectric performance of the devices prepared above was tested at room temperature and under atmospheric conditions, and the results are summarized in Table 2.

[0056] Table 2: Summary of Device Performance Parameters for Each Embodiment

[0057] The superiority of the structure of this invention can be clearly seen from the data comparison in Table 2: Significantly improved efficiency: The maximum current efficiency (55 cd / A) of Embodiment 1 of this invention is more than twice that of Control Embodiment 1 (25 cd / A), demonstrating the synergistic advantages of the stacked structure and efficient exciton management. Simultaneously, its efficiency is also significantly higher than that of Control Embodiment 2 (40 cd / A), which lacks a core constraint structure. This indicates that the "EBL / EML / HBL" structure effectively prevents exciton quenching in the non-luminescent region, greatly improving the radiative recombination probability.

[0058] Reasonable driving voltage: The driving voltage (9.0V) of Embodiment 1 of the present invention is approximately twice that of the control embodiment 1 (4.5V). This conforms to the basic physical law of voltage superposition in stacked devices, indicating that the CGL and core constraint structure designed in this invention do not introduce significant additional voltage drop, thus ensuring high power efficiency.

[0059] Significantly Extended Lifespan: Lifespan is the core advantage of this invention in solving the "blue light problem." First, compared to Control Example 1 (200 hours), the lifespan of all stacked devices (Example 2 and this invention) is significantly improved, thanks to a substantial reduction in operating current density at the same brightness. Second, the lifespan of Example 1 of this invention (850 hours) is much longer than that of Control Example 2 (350 hours), which lacks a core constraint structure, demonstrating that by perfectly confining excitons and reducing bombardment of non-light-emitting layer materials, the device decay rate can be effectively slowed down.

[0060] Reference Figure 2The figure shows the external quantum efficiency (EQE) curves of three different embodiments of the device as a function of brightness. It can be seen that the EQE of Embodiment 3 remains consistently at a high level of nearly 20%, exhibiting excellent brightness stability; the EQE of Embodiment 2 increases slowly with increasing brightness, eventually approaching 15%; while the EQE of Embodiment 1 is in a lower range (below approximately 8%) and decreases slightly with increasing brightness. This result indicates that the device of Embodiment 3 possesses superior photoelectric conversion efficiency and stability over a wide brightness range, and its performance is significantly better than that of Embodiments 1 and 2.

[0061] In summary, the blue light stacked OLED structure proposed in this invention, by systematically integrating the stacked architecture, the dual-sided core constraint structure inside the unit, and the highly stable CGL material system, successfully improves the efficiency and lifespan of the device, providing a comprehensive and effective technical solution to the long-standing blue light problem in the OLED field.

[0062] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A blue-light-emitting multilayer organic electroluminescent device, characterized in that, It includes an anode, a cathode, a first blue electroluminescent unit disposed between the anode and the cathode, a second blue electroluminescent unit, and a charge generating layer disposed between the first blue electroluminescent unit and the second blue electroluminescent unit; wherein, both the first blue electroluminescent unit and the second blue electroluminescent unit include an electron blocking layer, a blue light emitting layer, and a hole blocking layer disposed sequentially.

2. The blue light-emitting multilayer organic electroluminescent device according to claim 1, characterized in that, The charge generation layer comprises an n-type doped charge generation layer and a p-type doped charge generation layer; the n-type doped charge generation layer comprises an electron transport host material and an n-type dopant, wherein the n-type dopant is a rare earth metal or a compound thereof.

3. The blue light-emitting multilayer organic electroluminescent device according to claim 1, characterized in that, An electron injection layer is disposed below the cathode, and the electron injection layer contains rare earth metals or their compounds.

4. The blue light-emitting multilayer organic electroluminescent device according to claim 1, characterized in that, Between the anode and the first blue electroluminescent unit, there is also a p-type doped hole injection layer.

5. A blue light-emitting multilayer organic electroluminescent device according to claim 1, characterized in that, Above the cathode, there is also an optical cladding layer, which together with the other layers of the device constitutes an optical microcavity structure.

6. A blue light-emitting multilayer organic electroluminescent device according to claim 1, characterized in that, The blue light emitting layer comprises a host material and a blue light emitting dopant material, wherein the blue light emitting dopant material is selected from at least one of blue light fluorescent materials, blue light phosphorescent materials, or blue light thermally activated delayed fluorescent materials.

7. A blue light-emitting multilayer organic electroluminescent device according to claim 1, characterized in that, The lowest unoccupied molecular orbital energy level of the material used in the electron blocking layer is higher than the lowest unoccupied molecular orbital energy level of the host material in the adjacent blue light emitting layer; the highest occupied molecular orbital energy level of the material used in the hole blocking layer is lower than the highest occupied molecular orbital energy level of the host material in the adjacent blue light emitting layer.

8. A blue-light-emitting multilayer organic electroluminescent device according to claim 1, characterized in that, The anode layer is a transparent conductive oxide.

9. A blue light-emitting multilayer organic electroluminescent device according to claim 1, characterized in that, The cathode has a thickness of 5 nm to 15 nm; the electron blocking layer has a thickness of 3 nm to 8 nm; and the optical cladding layer has a thickness of 60 nm to 70 nm.

10. A method for fabricating a blue-light-emitting multilayer organic electroluminescent device according to any one of claims 1-9, characterized in that, This includes depositing an anode, a hole injection layer, a first blue electroluminescent unit, a charge generation layer, a second blue electroluminescent unit, an electron injection layer, a cathode, and an optical capping layer sequentially on a substrate under a high vacuum environment through a vacuum thermal evaporation process.

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