Organic light-emitting device, display panel and electronic equipment

Abstract

The invention discloses an organic light-emitting device, a display panel and electronic equipment, and the organic light-emitting device comprises a carrier substrate, a refractive index gradient layer, an anode, a light-emitting functional layer and a cathode which are sequentially stacked, the refractive index of the refractive index gradient layer is gradually increased from a first refractive index to a second refractive index along the direction from the carrier substrate to the anode, the first refractive index is larger than or equal to the refractive index of the carrier substrate, and the second refractive index is smaller than or equal to the refractive index of the anode. After light emitted by the light-emitting functional layer passes through the anode, the light is refracted for multiple times at the interface of the anode and the refractive index gradient layer and in the refractive index gradient layer and reaches the interface of the refractive index gradient layer and the carrier substrate, the incident angle is greatly reduced relative to the initial incident angle, and the possibility of total reflection is reduced. Therefore, the light extraction efficiency of the organic light-emitting device is improved, and the brightness of the organic light-emitting device is improved.

Description

Technical Field

[0001] The present invention relates to optoelectronic display technology, and in particular to an organic electroluminescent device, a display panel and an electronic device. Background Art

[0002] In an organic light-emitting diode (OLED), an electric field causes holes generated at the anode and electrons generated at the cathode to migrate, injecting into the hole-transport layer and electron-transport layer, respectively, before migrating to the light-emitting layer. When these two molecules meet in the light-emitting layer, they generate energy excitons, which in turn excite the luminescent molecules, ultimately producing visible light. OLEDs offer advantages such as high luminous efficiency, high brightness, long life, and environmental friendliness, making them widely used in display and lighting applications.

[0003] Existing organic electroluminescent devices typically use a bottom-emitting design, where light from the light-emitting layer exits the substrate via a transparent anode. Because the substrate's refractive index is typically lower than that of the anode, and the difference between the two is significant, the emitted light is prone to total internal reflection at the substrate-anode interface, reducing the device's light extraction efficiency and brightness. Summary of the Invention

[0004] The present invention provides an organic electroluminescent device, a display panel and an electronic device, which can improve the light extraction efficiency and brightness of the organic electroluminescent device.

[0005] In a first aspect, the present invention provides an organic electroluminescent device, comprising:

[0006] a carrier substrate;

[0007] a refractive index gradient layer, the refractive index gradient layer being disposed on one side of the carrier substrate;

[0008] an anode, the anode being disposed on a side of the refractive index gradient layer away from the carrier substrate;

[0009] a light-emitting functional layer, the light-emitting functional layer being arranged on a side of the anode away from the refractive index gradient layer;

[0010] a cathode, the cathode being disposed on a side of the light-emitting functional layer away from the anode;

[0011] The refractive index of the anode is greater than the refractive index of the carrier substrate, and the refractive index of the refractive index gradient layer gradually increases from a first refractive index to a second refractive index along the direction from the carrier substrate to the anode, the first refractive index is greater than or equal to the refractive index of the carrier substrate, and the second refractive index is less than or equal to the refractive index of the anode.

[0012] Optionally, the refractive index gradient layer includes at least two adjustment sublayers, the adjustment sublayer close to the carrier substrate has a first refractive index, and the adjustment sublayer close to the anode has a second refractive index, and the refractive index of the at least two adjustment sublayers gradually increases along the direction from the carrier substrate to the anode.

[0013] Optionally, the thickness and refractive index of each regulating sublayer in the refractive index gradient layer satisfy the following formula:

[0014]

[0015] Among them, L is the number of layers of the regulation sublayer, n i is the refractive index of the i-th regulating sublayer, t i is the thickness of the i-th regulating sublayer, λ em is the wavelength of the light emitted by the organic electroluminescent device, and k is a natural number.

[0016] Optionally, the thickness of the refractive index gradient layer ranges from 30 nm to 200 nm.

[0017] Optionally, the organic electroluminescent device further includes a scattering layer, and the scattering layer is arranged on a side of the carrier substrate away from the refractive index gradient layer.

[0018] Optionally, the scattering layer includes a substrate and scattering particles dispersed in the substrate.

[0019] Optionally, the scattering particles are SiO2 particles, and the surfaces of the SiO2 particles are hydroxylated; or,

[0020] The scattering particles are doped with Al 3+ ZnO particles; or

[0021] The scattering particles are TiO2-SiO2 core-shell particles, wherein the TiO2 core is covered with a SiO2 shell; or

[0022] The scattering particles include polymethyl methacrylate microsphere particles and SiO2 hollow particles, and the interior of the SiO2 hollow particles is a nitrogen cavity.

[0023] Optionally, a microlens array is formed on a surface of the scattering layer away from the carrier substrate, the array period ranges from 2 μm to 8 μm, and the curvature radius of the lens ranges from 1 μm to 3 μm.

[0024] In a second aspect, the present invention further provides a display panel comprising the organic electroluminescent device provided in the first aspect of the present invention.

[0025] In a third aspect, the present invention further provides an electronic device comprising the display panel provided in the second aspect of the present invention.

[0026] The organic electroluminescent device provided by the present invention includes a carrier substrate, a refractive index gradient layer, an anode, a light-emitting functional layer, and a cathode. The refractive index gradient layer is disposed on one side of the carrier substrate, the anode is disposed on the side of the refractive index gradient layer away from the carrier substrate, the light-emitting functional layer is disposed on the side of the anode away from the refractive index gradient layer, and the cathode is disposed on the side of the light-emitting functional layer away from the anode. The refractive index of the anode is greater than the refractive index of the carrier substrate. The refractive index of the refractive index gradient layer gradually increases from a first refractive index to a second refractive index along the direction from the carrier substrate to the anode. The first refractive index is greater than or equal to the refractive index of the carrier substrate, and the second refractive index is less than or equal to the refractive index of the anode. After light emitted from the light-emitting functional layer passes through the anode, it undergoes multiple refractions at the interface between the anode and the refractive index gradient layer, as well as within the refractive index gradient layer. When it reaches the interface between the refractive index gradient layer and the carrier substrate, the incident angle is significantly reduced relative to the initial incident angle, thereby reducing the possibility of total internal reflection, thereby improving the light extraction efficiency of the organic electroluminescent device and improving the brightness of the organic electroluminescent device. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 A schematic structural diagram of an organic electroluminescent device provided by the present invention;

[0029] Figure 2 This is a schematic structural diagram of another organic electroluminescent device provided by the present invention.

[0030] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0031] To make the technical problems solved, the technical solutions adopted, and the technical effects achieved by the present invention more clearly understood, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the described embodiments are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0032] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0033] In the present invention, unless otherwise expressly specified and limited, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, the first feature being "above", "above" and "above" the second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature includes the first feature being directly below and obliquely below the second feature, or simply means that the first feature is lower in level than the second feature. In addition, the terms "first" and "second" are only used to distinguish in description and have no special meaning.

[0034] Figure 1 A schematic structural diagram of an organic electroluminescent device provided by the present invention is shown in FIG. Figure 1 As shown, the organic electroluminescent device includes:

[0035] Carrier substrate 110. For example, the carrier substrate 110 may be a transparent substrate with high light transmittance, including a glass substrate and a substrate made of an organic material, which is not limited in the present invention.

[0036] The refractive index gradient layer 120 is disposed on one side of the carrier substrate 110 .

[0037] Anode 130 is disposed on a side of the refractive index gradient layer 120 away from the carrier substrate 110. For example, the material of anode 130 may be indium tin oxide (ITO). In other embodiments of the present invention, the material of anode 130 may also be other anode materials, which is not limited herein.

[0038] The light-emitting functional layer 140 is disposed on the side of the anode 130 away from the refractive index gradient layer 120. For example, the light-emitting functional layer 140 may include an electron injection layer, an electron transport layer, a light-emitting layer, a hole transport layer, a hole injection layer, etc., which is not limited in the present invention.

[0039] The cathode 150 is disposed on a side of the light-emitting functional layer 140 away from the anode 130. For example, the cathode 150 may be made of a metal material, such as aluminum, magnesium, silver, or alloys thereof, which is not limited in the present invention.

[0040] Among them, the refractive index of the anode 130 is greater than the refractive index of the carrier substrate 110, and the refractive index of the refractive index gradient layer 120 along the direction from the carrier substrate 110 to the anode 130 gradually increases from a first refractive index to a second refractive index, the first refractive index is greater than or equal to the refractive index of the carrier substrate 110, and the second refractive index is less than or equal to the refractive index of the anode 130.

[0041] For example, Figure 1 As shown, after the light emitted by the light-emitting functional layer 140 passes through the anode 130, it undergoes multiple refractions at the interface between the anode 130 and the refractive index gradient layer 120, as well as inside the refractive index gradient layer 120. When it reaches the interface between the refractive index gradient layer 120 and the carrier substrate 110, the incident angle α2 is greatly reduced relative to the initial incident angle α1, thereby reducing the possibility of total reflection, thereby improving the light extraction efficiency of the organic electroluminescent device and improving the brightness of the organic electroluminescent device.

[0042] The organic electroluminescent device provided by the present invention includes a carrier substrate, a refractive index gradient layer, an anode, a light-emitting functional layer, and a cathode. The refractive index gradient layer is disposed on one side of the carrier substrate, the anode is disposed on the side of the refractive index gradient layer away from the carrier substrate, the light-emitting functional layer is disposed on the side of the anode away from the refractive index gradient layer, and the cathode is disposed on the side of the light-emitting functional layer away from the anode. The refractive index of the anode is greater than the refractive index of the carrier substrate. The refractive index of the refractive index gradient layer gradually increases from a first refractive index to a second refractive index along the direction from the carrier substrate to the anode. The first refractive index is greater than or equal to the refractive index of the carrier substrate, and the second refractive index is less than or equal to the refractive index of the anode. After light emitted from the light-emitting functional layer passes through the anode, it undergoes multiple refractions at the interface between the anode and the refractive index gradient layer, as well as within the refractive index gradient layer. When it reaches the interface between the refractive index gradient layer and the carrier substrate, the incident angle is significantly reduced relative to the initial incident angle, thereby reducing the possibility of total internal reflection, thereby improving the light extraction efficiency of the organic electroluminescent device and improving the brightness of the organic electroluminescent device.

[0043] Figure 2 This is a schematic diagram of the structure of another organic electroluminescent device provided by the present invention. This embodiment further explains the refractive index gradient layer based on the previous embodiment. The rest of the embodiment is the same as the previous embodiment, and the present invention will not repeat it here. Figure 2 As shown, in this embodiment, the refractive index gradient layer 120 includes at least two regulating sublayers. Figure 2Taking the refractive index gradient layer 120 as an example, including the adjustment sublayer 121 and the adjustment sublayer 122, the adjustment sublayer 121 near the carrier substrate 110 has a first refractive index, and the adjustment sublayer 122 near the anode 130 has a second refractive index. The refractive index of at least two adjustment sublayers gradually increases along the direction from the carrier substrate 110 to the anode 130. Exemplarily, the first refractive index is less than the second refractive index, and the first refractive index is greater than the refractive index of the carrier substrate 110, and the difference between the first refractive index and the refractive index of the carrier substrate 110 is within 0.25. The second refractive index is less than the refractive index of the anode 130, and the difference between the second refractive index and the refractive index of the anode 130 is within 0.25. This avoids the problem of full reflection caused by excessive differences in refractive indices between different layers.

[0044] For example, Figure 2 As shown, after the light emitted by the light-emitting functional layer 140 passes through the anode 130, it is refracted at the interface between the anode 130 and the regulating sublayer 121, and at the interface between the regulating sublayer 121 and the regulating sublayer 122. When it reaches the interface between the regulating sublayer 122 and the carrier substrate 110, the incident angle α2 is greatly reduced relative to the initial incident angle α1, thereby reducing the possibility of total reflection, thereby improving the light extraction efficiency of the organic electroluminescent device and improving the brightness of the organic electroluminescent device.

[0045] It should be noted that, in other embodiments of the present invention, the refractive index gradient layer may include multiple adjustment sublayers, which is not limited in the present invention.

[0046] In one embodiment of the present invention, the carrier substrate 110 is a glass substrate with a refractive index of approximately 1.5. The anode 130 is ITO with a refractive index between 1.8 and 2.1. The regulating sublayer 121 can be made of SiO2 or MgF2 with a refractive index between 1.5 and 1.8. The regulating sublayer 122 can be made of TiO2, Nb2O5, or Ta2O5 with a refractive index between 1.8 and 2.0. The refractive index gradient layer 120 has a thickness ranging from 50 nm to 200 nm.

[0047] In another embodiment of the present invention, the carrier substrate 110 is a glass substrate with a refractive index of approximately 1.5. The anode 130 is ITO with a refractive index between 1.8 and 2.1. The materials of the regulating sublayer 121 and the regulating sublayer 122 can be a doped mixture of high and low refractive index materials, for example, SiO2 doped in TiO2, and the refractive index of the regulating sublayer 121 and the regulating sublayer 122 can be controlled by controlling the doping concentration. Exemplarily, the refractive index of the regulating sublayer 121 is approximately between 1.5 and 1.8, and the refractive index of the regulating sublayer 122 is between 1.8 and 2.0. The thickness range of the refractive index gradient layer 120 is 30nm-100nm.

[0048] In the embodiment of the present invention, the thickness and refractive index of each regulating sublayer in the refractive index gradient layer satisfy the following formula:

[0049]

[0050] Among them, L is the number of layers of the regulation sublayer, n i is the refractive index of the i-th regulating sublayer, t i is the thickness of the i-th regulating sublayer, λ em is the wavelength of the light emitted by the organic electroluminescent device, and k is a natural number. Usually, k takes values ​​between 0, 1, and 2 according to different colors of light (blue, green, and red).

[0051] In some embodiments of the present invention, Figure 1 、 2 As shown, the organic electroluminescent device further includes a scattering layer 160, which is disposed on a side of the carrier substrate 110 away from the graded refractive index layer 120. The scattering layer 160 is used to scatter light emitted from the carrier substrate 110, thereby improving the light extraction efficiency of the organic electroluminescent device based on the scattering principle.

[0052] In some embodiments of the present invention, the scattering layer 160 includes a substrate and scattering particles dispersed within the substrate, with the filling rate of the scattering particles being between 5% and 30%. Exemplarily, the refractive index of the substrate of the scattering layer 160 is lower than that of the carrier substrate 110. Light emitted from the carrier substrate 110 is refracted at the interface between the carrier substrate 110 and the scattering layer 160. Upon reaching the interface between the scattering layer 160 and air, the angle of incidence is significantly reduced relative to the initial angle of incidence, thereby reducing the likelihood of total internal reflection and thereby improving the light extraction efficiency and brightness of the organic electroluminescent device. Furthermore, light incident on the scattering layer 160 is scattered by the scattering particles within the scattering layer 160, changing its original propagation direction and scattering in all directions, thereby improving light extraction efficiency and uniformity.

[0053] In some embodiments of the present invention, the base material of the scattering layer 160 may be an organic resin, including UV-curable acrylate resin, organic silicone, polymethyl methacrylate (PMMA) or SU8 photoresist, with a viscosity between 300 cP and 800 cP.

[0054] In some embodiments of the present invention, the scattering particles are SiO2 particles with a particle size between 100 nm and 300 nm. The surface of the SiO2 particles is hydroxylated to enhance dispersibility in the substrate.

[0055] In some embodiments of the present invention, the scattering particles are doped with Al 3+ ZnO particles reduce the ultraviolet light absorption rate, and the particle size is between 80nm-250nm.

[0056] In some embodiments of the present invention, the scattering particles are TiO2-SiO2 core-shell particles, wherein the TiO2 core is coated with a SiO2 shell, the TiO2 core has a particle size of 50nm-100nm, and the SiO2 shell has a thickness of 10nm-30nm.

[0057] In some embodiments of the present invention, the scattering particles include polymethyl methacrylate (PMMA) microspheres and SiO2 hollow particles, wherein the SiO2 hollow particles have nitrogen cavities inside. The PMMA microspheres have a particle size of 150nm-400nm, and the SiO2 hollow particles have a particle size of 50nm-200nm.

[0058] For example, in the embodiment of the present invention, if the organic electroluminescent device emits blue light (wavelength between 440nm-480nm), the scattering particles may preferably be SiO2 particles with hydroxylation treatment on the surface; if the organic electroluminescent device emits green light (wavelength between 510nm-550nm), the scattering particles may preferably be Al doped particles. 3+ ZnO particles; if the organic electroluminescent device emits red light (wavelength between 600nm-640nm), the scattering particles can preferably be TiO2-SiO2 core-shell particles.

[0059] In some embodiments of the present invention, during the preparation of the scattering layer 160, scattering particles are added to a dispersion using ultrasonic dispersion combined with a static mixer to ensure that the particle agglomeration rate is less than 5%. After dispersion, the dispersion is coated and formed into a film within 30 minutes. The film formation method is slot coating, followed by UV or thermal curing, with the thermal curing temperature below 110°C.

[0060] In some embodiments of the present invention, a microlens array is formed on the surface of the scattering layer 160 away from the carrier substrate 110. The array period ranges from 2 μm to 8 μm, and the lens curvature radius ranges from 1 μm to 3 μm, further improving light extraction efficiency. For example, during the later stage of curing the resin used to prepare the scattering layer 160, an embossing method can be used to form the microlens array on the surface of the scattering layer 160 away from the carrier substrate 110.

[0061] In order to verify the effect of the present invention, the present invention prepared a plurality of organic light-emitting devices as test devices and carried out test experiments.

[0062] Test device 1

[0063] 1. Substrate pretreatment

[0064] A glass substrate with a thickness of 0.7 mm (refractive index n=1.52) was used, and surface organic pollutants were removed by plasma cleaning (Ar / O2 mixed gas, power 200 W, time 5 min).

[0065] 2. Preparation of anode, light-emitting layer, and cathode

[0066] ITO anode: An ITO layer (thickness 100 nm, square resistance 10 Ω / sq) was prepared by radio frequency sputtering, and then etched to form a pixel electrode pattern.

[0067] Light-emitting layer and cathode: vacuum evaporated HAT-CN hole injection layer, NPB hole transport layer (40nm), electro-blocking layer TCTA (10nm), the material of the light-emitting layer is Bepp2 doped with Ir(ppy)3, the doping ratio is 5%, and the thickness is 30nm, the electron transport layer, Bphen doped with 8-hydroxyquinoline lithium (Liq), Bepp2 is bis(2-(2-phenolyl)pyridine)beryllium, Ir(ppy)3 is tris(2-phenylpyridine)iridium, HAT-CN is 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, NPB is N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, TCTA is tris(4-carbazolyl-9-ylphenyl)amine, Bphen doped with Liq, the doping ratio is 70%, and the thickness is 30nm. The cathode material is Al and the thickness is 200 nm.

[0068] 3. Packaging: Use glass cover + UV curing glue for packaging.

[0069] Test device 2

[0070] 1. Substrate pretreatment

[0071] A glass substrate with a thickness of 0.7 mm (n=1.52) was used, and surface organic pollutants were removed by plasma cleaning (Ar / O2 mixed gas, power 200 W, time 5 min).

[0072] 2. Preparation of Refractive Index Gradient Layer

[0073] The regulating sublayer 121 is formed by magnetron sputtering of SiO2 layer (purity 99.99%, thickness 80 nm, n=1.45), substrate temperature 120°C, sputtering power 1.5 kW, or plasma enhanced chemical vapor deposition (PECVD) film formation.

[0074] Adjustment sublayer 122: A gradient-doped TiO2 / ZrO2 composite target (ZrO2 doping concentration increases gradually from 0% to 8%) is used to deposit a gradient refractive index layer with a thickness of 100 nm (refractive index n increases gradually from 1.8 to 2.1), a sputtering pressure of 0.3 Pa, and a substrate temperature of 150°C.

[0075] 3. Preparation of anode, light-emitting layer, and cathode

[0076] ITO anode: An ITO layer (thickness 100 nm, square resistance 10 Ω / sq) was prepared by radio frequency sputtering, and then etched to form a pixel electrode pattern.

[0077] Light-emitting layer and cathode: Vacuum-evaporated HAT-CN hole injection layer, NPB hole transport layer (40nm), and TCTA (10nm) electrolytic blocking layer. The light-emitting layer material is Bepp2 doped with Ir(ppy)3 at a doping ratio of 5% and a thickness of 30nm, and Bphen doped with 8-hydroxyquinoline lithium at a doping ratio of 70% and a thickness of 30nm. The cathode material is Al, with a thickness of 200nm.

[0078] 4. Packaging: Use glass cover + UV curing glue for packaging.

[0079] Test device 3

[0080] 1. Substrate pretreatment

[0081] A glass substrate with a thickness of 0.7 mm (n=1.52) was used, and surface organic pollutants were removed by plasma cleaning (Ar / O2 mixed gas, power 200 W, time 5 min).

[0082] 2. Preparation of Refractive Index Gradient Layer

[0083] Adjustment sublayer 121: magnetron sputtering SiO2 layer (purity 99.99%, thickness 80nm, n=1.45), substrate temperature 120°C, sputtering power 1.5kW, or PECVD film formation.

[0084] Adjustment sublayer 122: A gradient-doped TiO2 / ZrO2 composite target (ZrO2 doping concentration increases gradually from 0% to 8%) is used to deposit a gradient refractive index layer with a thickness of 100 nm (refractive index n increases gradually from 1.8 to 2.1), a sputtering pressure of 0.3 Pa, and a substrate temperature of 150°C.

[0085] 3. Preparation of anode, light-emitting layer, and cathode

[0086] ITO anode: An ITO layer (thickness 100 nm, square resistance 10 Ω / sq) was prepared by radio frequency sputtering, and then etched to form a pixel electrode pattern.

[0087] Light-emitting layer and cathode: Vacuum-evaporated HAT-CN hole injection layer, NPB hole transport layer (40nm), and TCTA (10nm) electrolytic blocking layer. The light-emitting layer material is Bepp2 doped with Ir(ppy)3 at a doping ratio of 5% and a thickness of 30nm, and Bphen doped with 8-hydroxyquinoline lithium at a doping ratio of 70% and a thickness of 30nm. The cathode material is Al, with a thickness of 200nm.

[0088] 4. Packaging: Use glass cover + UV curing glue for packaging.

[0089] 5. Scattering Layer Preparation

[0090] A scattering layer is applied to the light-emitting surface of the glass substrate. The scattering layer is made of a polymethyl methacrylate (PMMA) resin matrix and scattering particles of approximately 200 nm ZnO. The weight ratio of the scattering particles to the resin matrix is ​​10%. The scattering layer is prepared using an online dispersion system, employing ultrasonic dispersion combined with a static mixer, to ensure that the particle agglomeration rate is less than 5%. After dispersion, the dispersion is applied to form a film within 30 minutes. The film is formed using a slot coating method, followed by thermal curing at 100°C for 10 minutes. After drying, the film is cured at 60°C for 2 hours until the removal layer is fully cured.

[0091] Test device 4

[0092] 1. Substrate pretreatment

[0093] A glass substrate with a thickness of 0.7 mm (n=1.52) was used, and surface organic pollutants were removed by plasma cleaning (Ar / O2 mixed gas, power 200 W, time 5 min).

[0094] 2. Preparation of Refractive Index Gradient Layer

[0095] Adjustment sublayer 121: magnetron sputtering SiO2 layer (purity 99.99%, thickness 80nm, n=1.45), substrate temperature 120°C, sputtering power 1.5kW, or PECVD film formation.

[0096] Adjustment sublayer 122: A gradient-doped TiO2 / ZrO2 composite target (ZrO2 doping concentration increases gradually from 0% to 8%) is used to deposit a gradient refractive index layer with a thickness of 100 nm (refractive index n increases gradually from 1.8 to 2.1), a sputtering pressure of 0.3 Pa, and a substrate temperature of 150°C.

[0097] 3. Preparation of anode, light-emitting layer, and cathode

[0098] ITO anode: An ITO layer (thickness 100 nm, square resistance 10 Ω / sq) was prepared by radio frequency sputtering, and then etched to form a pixel electrode pattern.

[0099] Light-emitting layer and cathode: Vacuum-evaporated HAT-CN hole injection layer, NPB hole transport layer (40nm), and TCTA (10nm) electrolytic blocking layer. The light-emitting layer material is Bepp2 doped with Ir(ppy)3 at a doping ratio of 5% and a thickness of 30nm, and Bphen doped with 8-hydroxyquinoline lithium at a doping ratio of 70% and a thickness of 30nm. The cathode material is Al, with a thickness of 200nm.

[0100] 4. Packaging: Use glass cover + UV curing glue for packaging.

[0101] 5. Scattering Layer Preparation

[0102] The organic-inorganic hybrid material is a mixture of polymethyl methacrylate (PMMA) microspheres and hollow SiO2 microspheres (calculated at a weight ratio of 1:1). The PMMA microspheres have a diameter of about 200nm and the hollow SiO2 microspheres have a diameter of about 100nm. They are then added to a UV-curable acrylic resin matrix material for blending to obtain a light extraction layer material with a viscosity of 600cP. The coating film is formed by a slit coating method, followed by UV+thermal curing, first using a 365nm ultraviolet lamp with an intensity of ≥50mW / cm 2 , irradiation time 60S, then transfer to thermal curing temperature 60℃, 2 hours, until the removal layer is completely cured.

[0103] Test device 5

[0104] 1. Substrate pretreatment

[0105] A glass substrate with a thickness of 0.7 mm (n=1.52) was used, and surface organic pollutants were removed by plasma cleaning (Ar / O2 mixed gas, power 200 W, time 5 min).

[0106] 2. Preparation of Refractive Index Gradient Layer

[0107] Adjustment sublayer 121: magnetron sputtering SiO2 layer (purity 99.99%, thickness 80nm, n=1.45), substrate temperature 120°C, sputtering power 1.5kW, or PECVD film formation.

[0108] Adjustment sublayer 122: A gradient-doped TiO2 / ZrO2 composite target (ZrO2 doping concentration increases gradually from 0% to 8%) is used to deposit a gradient refractive index layer with a thickness of 100 nm (refractive index n increases gradually from 1.8 to 2.1), a sputtering pressure of 0.3 Pa, and a substrate temperature of 150°C.

[0109] 3. Preparation of anode, light-emitting layer, and cathode

[0110] ITO anode: An ITO layer (thickness 100 nm, square resistance 10 Ω / sq) was prepared by radio frequency sputtering, and then etched to form a pixel electrode pattern.

[0111] Light-emitting layer and cathode: Vacuum-evaporated HAT-CN hole injection layer, NPB hole transport layer (40nm), and TCTA (10nm) electrolytic blocking layer. The light-emitting layer material is Bepp2 doped with Ir(ppy)3 at a doping ratio of 5% and a thickness of 30nm, and Bphen doped with 8-hydroxyquinoline lithium at a doping ratio of 70% and a thickness of 30nm. The cathode material is Al, with a thickness of 200nm.

[0112] 4. Packaging: Use glass cover + UV curing glue for packaging.

[0113] 5. Scattering Layer Preparation

[0114] A scattering layer is applied to the light-emitting surface of a glass substrate. The scattering layer is made of a polymethyl methacrylate (PMMA) resin matrix and ZnO particles with a particle size of approximately 200 nm. The weight ratio of the scattering particles to the resin matrix is ​​10%. The scattering layer is prepared using an online dispersion system, employing ultrasonic dispersion combined with a static mixer, to ensure that the particle agglomeration rate is less than 5%. The dispersion is applied to form a film within 30 minutes of dispersing. The film is then cured using a slot-coating method at 100°C for 10 minutes. After drying, a replica template made of hard quartz containing a microlens array (with a 5μm period and a 2μm radius of curvature) is used. An anti-sticking layer (such as fluorosilane) is applied to the template surface to reduce demolding difficulties. Pressure and temperature are then applied to the template, which is then cured at 60°C for 2 hours until the removal layer is fully cured. The template is then removed to obtain the microlens array.

[0115] Each test device was tested at the same test voltage (5V), and the performance comparison of each test device is shown in the following table.

[0116]

[0117]

[0118] As shown in the table above, in the vertical direction (90° perpendicular to the carrier substrate), when the device operating voltage is 5V, the device with a refractive index gradient layer (test device 2), and the device with both a refractive index gradient layer and a scattering layer (test device 3 and test device 4) respectively bring about a 14.5%-38.1% improvement in front brightness. The overall external quantum efficiency EQE of the device is improved by 8.6%, 44.2%, and 53.7% compared to the device of the prior art (test device 1), achieving better light extraction efficiency. Compared with the device with a refractive index gradient layer (test device 2), the device with both a refractive index gradient layer and a scattering layer (test device 3 and test device 4) can further improve the device EQE, indicating that the composite structure has a better effect on suppressing light loss than a single technical solution.

[0119] The device (test device 5) combining the refractive index gradient layer, scattering layer and microlens array achieved the highest brightness (46045cd / m 2 ), which is 63.8% higher than the baseline, and its brightness at 60° reaches 34558cd / m 2 , an improvement of 87.2%; EQE also leads the way with a value of 19.5%, an 87.5% improvement over the existing device (Test Device 1), demonstrating that the microlens array's light-converging effect can significantly optimize wide-angle light extraction efficiency. The positive correlation between EQE and brightness improvement indicates that these technologies effectively reduce total internal reflection and light absorption losses within the device.

[0120] It is worth noting that the device with only a refractive index gradient layer (test device 2) has a brightness improvement of only 10.5% in the 60° direction, which is lower than the 14.5% improvement in the 90° vertical direction. The brightness improvement at 60° for all devices with a refractive index gradient layer and a scattering layer (test device 3, test device 4, and test device 5) is higher than that in the front direction. In particular, after the introduction of the microlens array, the 60° brightness improvement (87.2%) exceeds the front improvement (63.8%), indicating that controlling light scattering in the non-vertical direction is the key to improving the overall lighting efficiency.

[0121] Furthermore, the spectra of the devices with graded refractive index layers and scattering layers (Test Devices 3, 4, and 5) remain unchanged. This means that the color coordinates and color rendering characteristics of the luminescent material are fully preserved, avoiding the wavelength selectivity loss or color shift introduced by the graded refractive index layers and scattering layers, which is crucial for maintaining color accuracy and visual consistency in the devices.

[0122] The present invention further provides a display panel, comprising the organic electroluminescent device provided by any of the aforementioned embodiments of the present invention.

[0123] The present invention further provides an electronic device, comprising the display panel provided by the aforementioned embodiment of the present invention. The electronic device may be a smart phone, a television, a tablet computer, a desktop display, etc., and the present invention is not limited thereto.

[0124] In the description of this document, it should be understood that the terms "up", "down", "left", "right", and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0125] In this specification, reference to terms such as "one embodiment" or "example" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example.

[0126] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0127] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and are not to be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will readily conceive of other specific embodiments of the present invention without inventive effort, and such embodiments will fall within the scope of protection of the present invention.

Claims

1. An organic electroluminescent device, characterized in that: include: a carrier substrate; a refractive index gradient layer, the refractive index gradient layer being disposed on one side of the carrier substrate; an anode, the anode being disposed on a side of the refractive index gradient layer away from the carrier substrate; a light-emitting functional layer, the light-emitting functional layer being arranged on a side of the anode away from the refractive index gradient layer; a cathode, the cathode being disposed on a side of the light-emitting functional layer away from the anode; The refractive index of the anode is greater than the refractive index of the carrier substrate, and the refractive index of the refractive index gradient layer gradually increases from a first refractive index to a second refractive index along the direction from the carrier substrate to the anode, the first refractive index is greater than or equal to the refractive index of the carrier substrate, and the second refractive index is less than or equal to the refractive index of the anode.

2. The organic electroluminescent device according to claim 1, wherein The refractive index gradient layer includes at least two adjustment sublayers, the adjustment sublayer close to the carrier substrate has a first refractive index, and the adjustment sublayer close to the anode has a second refractive index. The refractive index of the at least two adjustment sublayers gradually increases along the direction from the carrier substrate to the anode.

3. The organic electroluminescent device according to claim 2, characterized in that: The thickness and refractive index of each regulating sublayer in the refractive index gradient layer satisfy the following formula: Among them, L is the number of layers of the regulation sublayer, n i is the refractive index of the i-th regulating sublayer, t i is the thickness of the i-th regulating sublayer, λ em is the wavelength of the light emitted by the organic electroluminescent device, and k is a natural number.

4. The organic electroluminescent device according to claim 3, characterized in that: The thickness of the refractive index gradient layer ranges from 30 nm to 200 nm.

5. The organic electroluminescent device according to any one of claims 1 to 4, characterized in that: The invention further comprises a scattering layer, wherein the scattering layer is arranged on a side of the carrier substrate away from the refractive index gradient layer.

6. The organic electroluminescent device according to claim 5, characterized in that: The scattering layer includes a base material and scattering particles dispersed in the base material.

7. The organic electroluminescent device according to claim 6, characterized in that: The scattering particles are SiO2 particles, and the surfaces of the SiO2 particles are hydroxylated; or The scattering particles are doped with Al 3+ ZnO particles; or The scattering particles are TiO2-SiO2 core-shell particles, wherein the TiO2 core is covered with a SiO2 shell; or The scattering particles include polymethyl methacrylate microsphere particles and SiO2 hollow particles, and the interior of the SiO2 hollow particles is a nitrogen cavity.

8. The organic electroluminescent device according to claim 7, characterized in that: A microlens array is formed on the surface of the scattering layer away from the carrier substrate, the array period ranges from 2 μm to 8 μm, and the curvature radius of the lens ranges from 1 μm to 3 μm.

9. A display panel, characterized in that: The organic electroluminescent device comprises the organic electroluminescent device according to any one of claims 1 to 8.

10. An electronic device, characterized in that: Comprising the display panel as claimed in claim 9.

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