A top emission OLED and display panel

Abstract

The present application relates to the field of organic electroluminescence devices, and specifically provides a top emission OLED and display panel. The top emission OLED comprises: an anode; a first light emitting unit comprising a first organic light emitting layer; a charge generation layer; a second light emitting unit comprising a second organic light emitting layer; a cathode, the first light emitting unit further comprises an anti-reflection structure between the anode and the first organic light emitting layer, the anti-reflection structure comprises a first sub-layer and a second sub-layer, wherein the first refractive index threshold <= (n2-n1) <= the second refractive index threshold and n1 >= the third refractive index threshold, and the first thickness threshold < t2 <= lambda / (2*n2), n2 is the refractive index of the second sub-layer, n1 is the refractive index of the first sub-layer, t2 is the thickness of the second sub-layer, and lambda is the wavelength of the light emitted by the OLED. The present application can effectively improve the problem of viewing angle decay and improve the efficiency of the OLED device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of organic electroluminescent devices, and specifically provides a top-emitting OLED and a display panel. BACKGROUND

[0002] Organic light-emitting diodes (OLED) have the characteristics of self-luminescence, high color saturation, low driving voltage, wide viewing angle display, flexibility, fast response speed, simple manufacturing process, and other advantages, and are increasingly widely used. In addition, OLEDs are also easy to realize color display and large-screen display, easy to match with integrated circuit drivers, and easy to realize flexible display. These advantages make OLED technology have broad application prospects in many fields, such as televisions, mobile phones, computer displays, medical equipment, vehicle display screens, etc.

[0003] According to the difference in the light-emitting position of the OLED device, it can be divided into two categories: bottom-emitting OLED (BEOLED) and top-emitting OLED (TEOLED). In these two structures, the top-emitting OLED is characterized in that it uses non-transparent total reflection electrodes, which are covered on the glass or silicon substrate, followed by the OLED layer. When a voltage is applied to the OLED, light will be emitted from the top transparent or semi-transparent cathode, achieving light emission. In the display of the top-emitting OLED device, the TFT (Thin Film Transistor) driving the OLED is made below the OLED, and the light-emitting surface is separated from the TFT. This design cleverly solves the problem of low aperture ratio, because the aperture ratio refers to the ratio of the area available for displaying images to the total area in the display, and improving the aperture ratio can significantly improve the brightness and clarity of the display.

[0004] In the structure of the top-emitting OLED, the combination of the total reflection electrode and the semi-transparent electrode forms a microcavity effect. This microcavity effect can cause strong multi-beam interference, thereby selectively, narrowing and strengthening the light source. This characteristic is often used to improve the color purity of the device, strengthen the emission intensity of specific wavelengths, and even change the light-emitting color of the device. However, the presence of the microcavity effect can affect the viewing angle characteristics of the device. Specifically, as the observation angle deviates, the position of the light-emitting peak also deviates, which can cause differences in brightness and color drift of the display. Therefore, how to improve the display effect while overcoming the viewing angle problem caused by the microcavity effect is an important aspect that needs to be considered in the development of OLED technology.

[0005] At present, the scheme for improving the viewing angle characteristics of top-emitting OLEDs generally adds a light output coupling layer on the cathode to improve the transmittance and light extraction rate, thereby reducing the influence of multi-beam interference. However, with the suppression of multi-beam interference, another wide-angle interference in the microcavity effect comes into play, and the above scheme cannot solve the problem of wide-angle interference. Therefore, the suppression effect of the coupling layer on the microcavity effect in OLED devices is limited, and the viewing angle characteristics cannot be effectively improved.

[0006] In order to optimize the viewing angle characteristics of top-emitting organic light-emitting diodes (OLEDs), that is, to improve the clarity of viewing angles, a common approach includes covering a light output coupling layer on the cathode material. However, the suppression effect on the wide-angle interference phenomenon is very limited, and cannot comprehensively solve the display problems of OLED devices under wide viewing angles. Therefore, in order to obtain more ideal viewing angle characteristics and avoid visual distortion under different observation angles, new solutions need to be explored to optimize the microcavity effect and light output performance of OLEDs under wide viewing angles. SUMMARY

[0007] The present application provides a top-emitting OLED and a display panel, which improve the viewing angle of the top-emitting OLED.

[0008] In a first aspect, the present application provides a top-emitting OLED, comprising:

[0009] an anode;

[0010] a first light-emitting unit located on the anode, comprising a first organic light-emitting layer;

[0011] a charge generation layer located on the first light-emitting layer;

[0012] a second light-emitting unit located on the charge generation layer, comprising a second organic light-emitting layer;

[0013] a cathode located on the second light-emitting unit,

[0014] wherein the first light-emitting unit further comprises an antireflection structure located between the anode and the first organic light-emitting layer, the antireflection structure comprises a first sublayer and a second sublayer stacked in order from the anode towards the cathode, wherein the first refractive index threshold ≤ (n2-n1) ≤ the second refractive index threshold and n1 ≥ the third refractive index threshold, and the first thickness threshold < t2 ≤ λ / (2*n2), wherein n2 is the refractive index of the second sublayer, n1 is the refractive index of the first sublayer, t2 is the thickness of the second sublayer, and λ is the wavelength of the light emitted by the OLED.

[0015] Further, the reflection-increasing structure further comprises a third sub-layer on the second sub-layer, wherein a first refractive index threshold ≤ (n2-n3) ≤ a second refractive index threshold and n3 ≥ a fourth refractive index threshold, wherein n3 is the refractive index of the third sub-layer.

[0016] Further, the first refractive index threshold is 0.05, the second refractive index threshold is 0.5, the third refractive index threshold and the fourth refractive index threshold are both greater than 1.6, and the first thickness threshold is 10 nm.

[0017] Further, the first sub-layer and the second sub-layer are both hole transport layers; or

[0018] The first sub-layer and the second sub-layer are both electron blocking layers; or

[0019] The first sub-layer and the second sub-layer are respectively adjacent hole transport layers and electron blocking layers.

[0020] Further, the first sub-layer, the second sub-layer and the third sub-layer are all hole transport layers; or

[0021] The first sub-layer, the second sub-layer and the third sub-layer are all electron blocking layers.

[0022] Further, n1 = n3.

[0023] Further, the first sub-layer and the second sub-layer are both hole transport layers, and the third sub-layer is an electron blocking layer.

[0024] Further, n1 = n3.

[0025] Further, the first sub-layer is a hole transport layer, and the second sub-layer and the third sub-layer are both electron blocking layers.

[0026] Further, n1 = n3.

[0027] Further, the distance L between the cathode and the anode ≥ (φλ-6πλ) / 4π, wherein φ is the sum of the phase difference of the light emitted by the first organic light-emitting layer and the second organic light-emitting layer on the anode and the phase difference on the cathode.

[0028] Further, the reflection-increasing structure further comprises a third sub-layer on the second sub-layer, wherein a first refractive index threshold ≤ (n2-n3) ≤ a second refractive index threshold and n3 ≥ a fourth refractive index threshold, wherein n3 is the refractive index of the third sub-layer.

[0029] A light coupling layer on the cathode, wherein the thickness of the cathode ≤ a second thickness threshold, and the product of the refractive index of the light coupling layer and the thickness of the light coupling layer ≤ a first preset threshold.

[0030] Further, the second thickness threshold = 16 nm and the first preset threshold = 180.

[0031] Further, the charge generation layer comprises an N-type organic doped layer and a P-type organic doped layer stacked in sequence from the anode towards the cathode direction.

[0032] In a second aspect, the present application provides a display panel, comprising:

[0033] a substrate;

[0034] an array of OLEDs according to the first aspect formed on the substrate.

[0035] The one or more technical solutions of the present application have at least one or more of the following beneficial effects:

[0036] In the top emission OLED device with two light emitting units, the present application sets the anti-reflection structure, and through setting the anti-reflection structure between the anode and the light emitting unit closer to the anode, the light emitted from the two light emitting units is totally reflected through the anti-reflection structure at a certain incident angle, thereby effectively improving the problem of too fast brightness decay.

[0037] The present application reduces the microcavity effect of the top emission OLED device by limiting the thickness of the cathode and the specific optical path length, i.e., the product of the refractive index of the optical coupling layer and the thickness of the optical coupling layer, thereby improving the problem of too fast brightness decay. BRIEF DESCRIPTION OF DRAWINGS

[0038] The disclosure of the present application will become more readily apparent from the following description of the non-limiting embodiments, taken in conjunction with the accompanying drawings. As those skilled in the art will appreciate, the drawings are not intended to limit the scope of the present application, but merely to illustrate the principles of the present application. Further, like reference numerals are intended to refer to like parts throughout the various drawings.

[0039] Figure 1 is a schematic diagram of the overall structure of a top emission OLED according to an embodiment of the present application;

[0040] Figure 2 is a schematic diagram of an anti-reflection structure composed of two sub-layers according to an embodiment of the present application;

[0041] Figure 3 is a schematic diagram of the structure principle of a reference Ref device according to a comparative example of the present application;

[0042] Figure 4 is a schematic diagram of an anti-reflection structure according to embodiment one of the present application;

[0043] Figure 5 is a schematic diagram of an anti-reflection structure according to embodiment two of the present application;

[0044] Figure 6 is a schematic diagram of an anti-reflection structure according to embodiment three of the present application;

[0045] Figure 7 is a schematic diagram of a top emission OLED according to an embodiment of the present application;

[0046] Figure 8 is a schematic diagram of a top emission OLED according to an embodiment of the present application;

[0047] Figure 9 is a schematic diagram of the principle of total reflection of a light emitting dipole at the anode adjacent wave node according to the present application;

[0048] Figure 10 is a schematic diagram of the principle of the present application using the top emission OLED with the embodiment seven or eight anti-reflection structure arranged at the anode adjacent wave node;

[0049] Figure 11 is an OLED device with two light wave periods between the anode and the cathode. DETAILED DESCRIPTION

[0050] Some embodiments of the present application will be described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present application, and are not intended to limit the protection scope of the present application.

[0051] Referring to Figure 1 , the present application provides a top emission OLED, comprising:

[0052] an anode 1;

[0053] a first light emitting unit 2 located on the anode 1, comprising a first organic light emitting layer;

[0054] a charge generation layer 3 located on the first light emitting layer 2;

[0055] a second light emitting unit 4 located on the charge generation layer 3, comprising a second organic light emitting layer;

[0056] a cathode 5 located on the second light emitting unit 4.

[0057] The top emission OLED of the present application is a laminated organic light emitting device, specifically a two light emitting unit series lamination structure. The OLED with series lamination structure can emit brighter light by laminating two light emitting units together, while also reducing power consumption. The two light emitting layers are connected together through a charge generation layer 3 (CGL). When the current passes through, part of the holes and electrons recombine to emit light in the first light emitting layer, and the remaining holes and electrons pass through the CGL and recombine to emit light in the second light emitting layer. Compared with single layer OLED, the brightness of the double layer series of the present application is greatly improved, and the current efficiency, device life and illumination brightness are also improved.

[0058] In one embodiment, the charge generation layer 3 comprises an N-type organic doped layer 3-1 and a P-type organic doped layer 3-2 stacked in sequence from the anode to the cathode.

[0059] The N-type organic doped layer is a charge layer doped with an N-type dopant, forming an N-type semiconductor material. The P-type organic doped layer is a charge layer doped with a P-type dopant, forming a P-type semiconductor material.

[0060] In a top-emitting OLED, the combination of a fully reflective electrode (anode) and a semi-transparent electrode (cathode) forms a microcavity effect, which negatively affects the luminance-decay of the device, i.e. causes brightness decay. To address this issue, the present application provides a reflection-increasing structure between the first light-emitting unit 2 and the anode 1, which causes the light emitted from the first and second organic light-emitting layers to be totally reflected at a certain angle of incidence by the reflection-increasing structure, thereby improving the problem of excessive rapid brightness decay.

[0061] Referring to Figure 2 The reflection-increasing structure of the present application specifically comprises: a first sub-layer 6 and a second sub-layer 7 stacked in sequence from the anode to the cathode, wherein the first refractive index threshold ≤ (n2-n1) ≤ the second refractive index threshold and n1 ≥ the third refractive index threshold, and the first thickness threshold < t2 ≤ λ / (2*n2), wherein n2 is the refractive index of the second sub-layer, n1 is the refractive index of the first sub-layer, t2 is the thickness of the second sub-layer, and λ is the wavelength of the light emitted by the OLED.

[0062] The effect is best when t2 is equal to λ / (2*n2), but in practical applications, the OLED device cannot reach this thickness, so a value less than λ / (2*n2) is usually selected. For example, for blue light with a wavelength of 460 nm, the value of λ / (2*n2) is calculated to be more than 100 nanometers, which is difficult to achieve in practical applications of the OLED device.

[0063] When the reflection-increasing structure comprises two sub-layers, the first sub-layer and the second sub-layer can be of the same type, such as both being a hole transport layer or both being an electron blocking layer; or the first sub-layer and the second sub-layer can be of different types, such as the first sub-layer being a hole transport layer and the second sub-layer being an electron blocking layer. Regardless of whether the two sub-layers are configured as a hole transport layer or an electron blocking layer, the reflection-increasing effect can be achieved when the refractive index and thickness of the reflection-increasing structure meet the above-mentioned conditions.

[0064] In addition to the two sub-layers, a third sub-layer 8 can be used to form the anti-reflection structure. The first refractive index threshold value ≤ (n2-n3) ≤ the second refractive index threshold value, and n3 ≥ the fourth refractive index threshold value, where n3 is the refractive index of the third sub-layer.

[0065] In one embodiment, the first refractive index threshold value is 0.05, the second refractive index threshold value is 0.5, the third refractive index threshold value and the fourth refractive index threshold value are both greater than 1.6, and the first thickness threshold value is 10 nm.

[0066] When the anti-reflection structure has three sub-layers, the first sub-layer, the second sub-layer, and the third sub-layer can be of the same type, such as both being hole transport layers or both being electron blocking layers. The refractive indices of the first sub-layer and the third sub-layer can be the same or different.

[0067] In addition, the first sub-layer, the second sub-layer, and the third sub-layer can also have both hole transport layer and electron blocking layer properties. For example, the first sub-layer is a hole transport layer, and the second sub-layer and the third sub-layer are both electron blocking layers. The refractive indices of the first sub-layer and the third sub-layer can be the same or different.

[0068] For the top-emitting OLED device of the present application, the problem of too fast angular decay is caused by the microcavity effect. For some cases, the microcavity effect of the device is more obvious, such as when the distance L between the cathode and the anode is large. In one embodiment, the distance L between the cathode and the anode is ≥ (φλ-6πλ) / 4π, where λ is the wavelength of the light emitted by the OLED, and φ is the sum of the phase difference of the light emitted by the first organic light-emitting layer and the second organic light-emitting layer on the anode and the phase difference on the cathode. Specifically, the light emitted by the first organic light-emitting layer and the second organic light-emitting layer is first reflected on the anode, forming two phase differences φ1, and then reflected on the cathode, forming two phase differences φ2, and φ1+φ2 is the total phase difference φ.

[0069] When the distance between the cathode and the anode of the top-emitting electrode is too large, the microcavity effect is more obvious, and the more obvious microcavity effect leads to worse angular decay. Therefore, for OLED devices with L greater than (φλ-6πλ) / 4π, the technology of the present application for reducing angular decay is more suitable. In addition, the distance L between the cathode and the anode forms a larger distance between the first organic light-emitting layer and the anode, so that the anti-reflection structure can be arranged between the first organic light-emitting layer and the anode to achieve optimization of L-Decay by increasing total reflection.

[0070] In addition to the above-mentioned technical means of setting the anti-reflection structure to increase total reflection, in order to improve the problem of too fast angular decay, the present application also optimizes the structural parameters of the OLED from the perspective of reducing the microcavity effect.

[0071] The top-emitting OLED further comprises:

[0072] The light coupling layer 9 is located on the cathode 5, and the light coupling layer 9 and the cathode 5 jointly constitute a semi-transparent and semi-reflective electrode structure in the microcavity effect, wherein the thickness of the cathode is less than a second thickness threshold, and the product of the refractive index of the light coupling layer and the thickness of the light coupling layer is less than a first preset threshold.

[0073] The light coupling layer plays a role in assisting in improving the viewing angle. Specifically, the light coupling layer is made of a material with low light absorption or a material with high refractive index, which can reduce the reflection of the semi-transparent metal electrode, increase the output rate of internal light, and further improve the viewing angle characteristics of the device.

[0074] In one embodiment, the top-emitting OLED further comprises: an encapsulation layer 10 located on the light coupling layer 9, which plays a role in encapsulation.

[0075] In one embodiment, the second thickness threshold is 16 nm, and the first preset threshold is 180.

[0076] In order to better and more fully optimize the viewing angle of the top-emitting OLED, the reflection-increasing structure for increasing total reflection and the cathode and light coupling layer parameter limitation for improving the microcavity effect are integrated together to improve the viewing angle decay, especially to reduce the degree of white light brightness decay of the top-emitting OLED at an angle of 45° relative to the white light brightness at 0° (front), while improving the efficiency of the top-emitting OLED.

[0077] The embodiments of the present application will be described in detail below with the reflection-increasing structure of three sub-layers as an example.

[0078] Comparative Example - Reference Ref device

[0079] The comparative example refers to the device structure of Ref Figure 1 The comparative example OLED does not contain the reflection-increasing structure, and satisfies the following conditions: the thickness THK(CTD) of the cathode CTD is greater than 16 nm; the product of the refractive index n of the light coupling layer CPL and the thickness THK / nm of the film layer satisfies n(CPL) x THK(CPL) > 180 nm; the hole transport layer in the first light-emitting unit comprises one layer; the electron blocking layer in the first light-emitting unit comprises one layer, and the comparative example refers to Figure 3 From the anode to the first organic light-emitting layer, the anode, the hole injection layer, the hole transport layer, the electron blocking layer, and the first organic light-emitting layer are stacked in sequence.

[0080] After testing, the efficiency is 100%, W L-Decay@45°~25%(45° white light brightness / 0° white light brightness=25%, the same calculation method). W L-Decay@45°~25% means that at 45° angle, the white light brightness of the device is attenuated by 75% (because only 25%) relative to the white light brightness at 0° (front).

[0081] W JNCD@0-60°(full angle)<10JNCD, which means that the color accuracy of the Ref device is less than 10JNCD at any angle from 0° to 60°.

[0082] In order to distinguish the hole transport layer and the electron blocking layer, in the following figures of embodiment one to embodiment eight, the hole transport layer part is framed with a dashed line to facilitate identification.

[0083] Example One - First to third sub-layers are hole transport layers + (n1 = n3)

[0084] Referring to Figure 4 , the first sublayer 6, the second sublayer 7 and the third sublayer 8 are all hole transport layers, the first sublayer 6 and the third sublayer 8 are the same material A, and the second sublayer 7 is material B.

[0085] The thickness of material B is greater than 10 nm; the refractive index n A of material A B , and n A ≥1.6, 0.05≤(n B -n A )≤0.5.

[0086] An electron blocking layer is formed on the third sublayer 8, and the refractive index and thickness of the material of the electron blocking layer are not limited.

[0087] After testing, the efficiency of the formed embodiment one OLED device is improved by 3% compared with the Ref device, L-Decay@45°~33%, W JNCD@0-60°(full angle)<7JNCD.

[0088] Example Two - First to third sub-layers are hole transport layers + (n1 ≠ n3)

[0089] Referring to Figure 5 , the first sublayer 6, the second sublayer 7 and the third sublayer 8 are all hole transport layers, the first sublayer 6 and the third sublayer 8 are different materials A and C, the second sublayer 7 is material B, and the thickness of material B is greater than 10 nm; the refractive index n A of material A B , and the refractive index n C of material C B , and n A ≥1.6 and n C ≥1.6(n A >nC or n A <n C ), 0.05≤(n B -n A )≤0.5 and 0.05≤(n B -n C )≤0.5.

[0090] The electron blocking layer is formed on the third sub-layer 8, and the material of the electron blocking layer has no limitation on the refractive index and thickness.

[0091] After testing, the formed OLED device of Example Two has an efficiency of 4% higher than that of the Ref device, L-Decay@45° ~ 35%, W JNCD@0-60° (full angle) < 7 JNCD.

[0092] Example Three - First and second sub-layers are hole transport layers and third sub-layer is electron blocking layer + (n1 = n3)

[0093] Figure 6

[0094] Referring to Example Four - First and second sub-layers are hole transport layers and third sub-layer is electron blocking layer + (n1 ≠ n3) , the first sub-layer 6 and the second sub-layer 7 are both hole transport layers but have different materials, which are A and B respectively, and the third sub-layer 8 is an electron blocking layer, and the material is E.

[0095] The thickness of the material B is greater than 10 nm; the refractive index n A <n B of the material A is less than n A , and n B ≥1.6, 0.05≤(n A -n E )≤0.5, and the refractive index n A of the material E of the third sub-layer 8 is n A .

[0096] After testing, the formed OLED device of Example Three has an efficiency of 5% higher than that of the Ref device, L-Decay@45° ~ 36%, W JNCD@0-60° (full angle) < 7 JNCD.

[0097] Figure 6

[0098] Example Five - First sub-layer is hole transport layer and second and third sub-layers are electron blocking layers + (n1 = n3)

[0099] Still referring to the structure of Figure 7 , the first sub-layer 6 and the second sub-layer 7 are both hole transport layers but have different materials, which are A and B respectively, and the thickness of the material B is greater than 10 nm; the refractive index n B <n A of the material A is less than n B , and n A≤ 0.5. The third sub-layer 8 is an electron blocking layer, the material of which is F, the refractive index n F ≠ n A , and n F ≥ 1.6, 0.05 ≤ (n B -n F ) ≤ 0.5.

[0100] After testing, the formed OLED device of Example Four has an efficiency improved by 6% compared to the Ref device, L-Decay@45° ~ 36%, W JNCD@0-60° (full angle) < 7 JNCD.

[0101] Example Six - First sub-layer is hole transport layer and second and third sub-layers are electron blocking layers + (n1 ≠ n3)

[0102] Figure 7

[0103] Referring to Example Seven - Two anti-reflection structures + anti-reflection structure is three layers of hole transport layer / three layers of electron blocking layer + (n1 = n3) , the first sub-layer 6 is a hole transport layer, and the second sub-layer 7 and the third sub-layer 8 are both electron blocking layers. The two electron blocking layers are different materials, that is, the materials of the second sub-layer 7 and the third sub-layer 8 are G and E respectively, and the thickness of the material G is > 10 nm; the refractive index n G > n E , and n H ≥ 1.6, 0.05 ≤ (n G -n E ) ≤ 0.5, the material of the first sub-layer 6 is A, and the refractive index n A = n E .

[0104] After testing, the formed OLED device of Example Five has an efficiency improved by 2% compared to the Ref device, L-Decay@45° ~ 33%, W JNCD@0-60° (full angle) < 7 JNCD.

[0105] Figure 8

[0106] Example Eight - Two anti-reflection structures + anti-reflection structure is three layers of hole transport layer / three layers of electron blocking layer + (n1 ≠ n3)

[0107] Still referring to the structure of Figure 8 , the first sub-layer 6 is a hole transport layer, and the second sub-layer 7 and the third sub-layer 8 are both electron blocking layers. The two electron blocking layers are different materials, that is, the materials of the second sub-layer 7 and the third sub-layer 8 are G and H respectively, and the thickness of the material G is > 10 nm; the refractive index n G > n H , and n H ≥ 1.6, 0.05 ≤ (n G -n H ) ≤ 0.5, the hole transport layer of the first sub-layer 6 is material A, and the refractive index n A ≠ nH , and n A ≥ 1.6, 0.05 ≤ (n G -n A ) ≤ 0.5.

[0108] The formed Example Six OLED device has 3% efficiency improvement compared to the Ref device, L-Decay@45° ~ 34%, W JNCD@0-60° (full angle) < 7 JNCD after testing.

[0109] Figure 10 n3)

[0110] With reference to Figure 9 , this embodiment integrates two stack-arranged anti-reflection structures, the anti-reflection structure closer to the anode includes three layers of hole transport layers, and the anti-reflection structure closer to the cathode includes three layers of electron blocking layers.

[0111] The first sub-layer 6 and the third sub-layer 8 in the three layers of hole transport layers of the anti-reflection structure are of the same material, material A, and the second sub-layer 6 is of material B,

[0112] The thickness of material B is > 10 nm; the refractive index n A of material A is < n B , and n A ≥ 1.6, 0.05 ≤ (n B -n A ) ≤ 0.5.

[0113] The first sub-layer 6 and the third sub-layer 8 in the three layers of electron blocking layers of the anti-reflection structure are of the same material, material H, and the second sub-layer 6 is of material I, the thickness of material I is > 10 nm; the refractive index n H of material H is < n I , and n H ≥ 1.6, 0.05 ≤ (n I -n H ) ≤ 0.5.

[0114] The formed Example Seven OLED device has 6% efficiency improvement compared to the Ref device, L-Decay@45° ~ 35%, W JNCD@0-60° (full angle) < 7 JNCD after testing.

[0115] Figure 10 n3)

[0116] With reference to Figure 9 and Figure 10 structures, this embodiment integrates two stack-arranged anti-reflection structures, the anti-reflection structure closer to the anode includes three layers of hole transport layers, and the anti-reflection structure closer to the cathode includes three layers of electron blocking layers.

[0117] In the three-layer hole transport layer of the anti-reflection structure, the first sublayer 6 and the third sublayer 8 are made of different materials, namely materials A and C, respectively, while the second sublayer 6 is made of material B, with a thickness > 10 nm; the refractive index n of material A is... A <n B And the refractive index n of material C C <n B And n A ≥1.6 and n C ≥1.6(n A >n C or n A <n C ), 0.05≤(n B -n A )≤0.5 and 0.05≤(n B -n C ≥0.5.

[0118] In the three-layer electron blocking layer of the anti-reflection structure, the first sublayer 6 and the third sublayer 8 are made of different materials, namely materials H and J, respectively, while the second sublayer 6 is made of material I, with a thickness > 10 nm. The refractive index nH of material H is < nI, and the refractive index nI of material J is nI. J <n I And n H ≥1.6 and n J ≥1.6(n H >n J or n H <n J ), 0.05≤(n I -n H )≤0.5 and 0.05≤(n I -n J )≤0.5.

[0119] After testing, the OLED device of Example 8 showed a 7% improvement in efficiency compared to the Ref device, with L-Decay@45°~36% and W JNCD@0-60° (full angle)<7JNCD.

[0120] As can be seen from the above embodiments, the device efficiency is improved and the viewing angle is significantly improved after the two anti-reflection structures are superimposed. This is because the superimposed two-layer anti-reflection structures have periodic structural characteristics, which improve the optoelectronic performance of the device.

[0121] In the above-mentioned anti-reaction structure, both the hole transport layer and the electron blocking layer can be deposited using multiple sources in the same evaporation chamber. That is, the materials of Source1, Source2, and Source3 in the same chamber can be the same or different. Specifically, as shown below, A, B, and C are hole transport materials and D, E, F, G, H, I, and J are electron blocking materials. The hole transport layer material can be NPB (N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine); the electron blocking layer material can be TCTA (4,4',4”-tris(carbazole-9-yl)triphenylamine).

[0122] Table 1 Material Types of Hole Transport Layer and Electron Blocking Layer Chambers

[0123]

[0124] As can be seen from Embodiments 1 to 8 above, the refractive index and thickness of the hole transport layer and / or electron blocking layer are clearly defined in the embodiments. Those skilled in the art can determine the composition and specific parameters of the anti-reflection structure through experimental measurement based on the actual selected materials.

[0125] Although specific numerical ranges are given in Examples 1 to 8, this does not mean that obtaining the parameters through experimental means is obvious. This is because the anti-reflection structure in this invention aims to increase the total internal reflection effect of the emitting dipole at the anode-adjacent junction, thereby improving the viewing angle attenuation. (Refer to...) Figure 11 and Figure 11 The light-emitting dipole mentioned here is the part of the organic light-emitting layer of an OLED that is responsible for emitting light after electron-hole coupling.

[0126] To achieve the aforementioned total internal reflection effect, light reflection paths are required between the layers of the antireflective structure, which can only be realized under specific thicknesses and refractive indices. This indicates that there are interdependent relationships among the various parameters of the antireflective structure, and these relationships are not immediately apparent.

[0127] Reference Figure 11 and Figure 10 The optimal effect is achieved when the reflector structure is positioned at the wave junction adjacent to the anode. The calculation process for the wave junction is as follows:

[0128] (1) As ​ As shown, for ​ An OLED device with two light-wave cycles between the anode and cathode is described by the following formula: φ m / 2π-2L1 / λ=2, calculate ​ L1 of the device. λ is the wavelength of the light emitted by the OLED, L1 is the distance between the portion of the first organic light-emitting layer used for hole and electron coupling and the anode, and φ...m a phase difference of light emitted by the first organic light-emitting layer and the second organic light-emitting layer on the anode.

[0129] (2) Refer to ​ According to L1*2, the distance between the anti-reflection structure and the anode in the OLED device including three light wave periods between the anode and the cathode is obtained. The OLED device including three light wave periods has the characteristic that the distance L between the anode and the cathode is equal to (φλ-6πλ) / 4π, where φ is the sum of the phase difference of light emitted by the first organic light-emitting layer and the second organic light-emitting layer on the anode and the phase difference on the cathode, and λ is the wavelength of light emitted by the OLED.

[0130] The application further provides a display panel, comprising:

[0131] a substrate;

[0132] the OLED arranged in an array on the substrate.

[0133] The substrate can be silicon-based, glass or PI (polyimide) flexible material.

[0134] It should be noted that, although the above embodiments describe the steps in a specific order, those skilled in the art can understand that, in order to achieve the effect of the application, the steps do not necessarily have to be executed in this order, and they can be executed simultaneously (in parallel) or in other orders, and these changes are within the protection scope of the application.

[0135] So far, the technical solutions of the application have been described in combination with the preferred embodiments shown in the drawings, but those skilled in the art can easily understand that the protection scope of the application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the application, and the technical solutions after the changes or replacements will fall within the protection scope of the application.

Claims

1. A top-emitting OLED, characterized in that, Comprising: an anode; a first light emitting unit on the anode, comprising a first organic light emitting layer; a charge generation layer on the first light emitting unit; a second light emitting unit on the charge generation layer, comprising a second organic light emitting layer; a cathode on the second light emitting unit, wherein the first light emitting unit further comprises an enhancement reflection structure between the anode and the first organic light emitting layer, the enhancement reflection structure comprises a first sub-layer and a second sub-layer stacked in order from the anode towards the cathode, wherein a first refractive index threshold ≤ (n2-n1) ≤ a second refractive index threshold and n1 ≥ a third refractive index threshold, and a first thickness threshold < t2 ≤ λ / (2*n2), wherein n2 is the refractive index of the second sub-layer, n1 is the refractive index of the first sub-layer, t2 is the thickness of the second sub-layer, and λ is the wavelength of the light emitted by the OLED; the first refractive index threshold is 0.05, the second refractive index threshold is 0.5, and the third refractive index threshold is greater than 1.6; the first sub-layer and the second sub-layer are both from a hole transport layer or an electron blocking layer.

2. The top-emitting OLED of claim 1, wherein, the enhancement reflection structure further comprises a third sub-layer on the second sub-layer, wherein a first refractive index threshold ≤ (n2-n3) ≤ a second refractive index threshold and n3 ≥ a fourth refractive index threshold, wherein n3 is the refractive index of the third sub-layer; the fourth refractive index threshold is greater than 1.

6.

3. The top-emitting OLED of claim 2, wherein, the first thickness threshold is 10 nm.

4. The top emission OLED according to any one of claims 1-3, wherein: the first sub-layer and the second sub-layer are both a hole transport layer; or the first sub-layer and the second sub-layer are both an electron blocking layer; or the first sub-layer and the second sub-layer are respectively an adjacent hole transport layer and an electron blocking layer.

5. The top emission OLED according to claim 2 or 3, wherein: the first sub-layer, the second sub-layer and the third sub-layer are all hole transport layers; or the first sub-layer, the second sub-layer and the third sub-layer are all electron blocking layers.

6. The top-emitting OLED of claim 5, wherein, n1 = n 3。 7. The top emission OLED according to claim 2 or 3, wherein: the first sub-layer and the second sub-layer are both hole transport layers, and the third sub-layer is an electron blocking layer.

8. The top-emitting OLED of claim 7, wherein, n1 = n3.

9. The top emission OLED according to claim 2 or 3, wherein: the first sub-layer is a hole transport layer, and the second sub-layer and the third sub-layer are both electron blocking layers.

10. The top-emitting OLED of claim 9, wherein, n1 = n 3。 11. The top-emitting OLED of claim 1, wherein, a distance L between the cathode and the anode is ≥ (φλ-6πλ) / 4π, wherein φ is the sum of the phase difference of the light emitted by the first organic light emitting layer and the second organic light emitting layer on the anode and the phase difference on the cathode.

12. The top-emitting OLED of claim 1, wherein, further comprising: a light coupling layer on the cathode, wherein the thickness of the cathode ≤ a second thickness threshold, and the product of the refractive index of the light coupling layer and the thickness of the light coupling layer ≤ a first preset threshold.

13. The top emission OLED according to claim 12, wherein: the second thickness threshold = 16 nm and the first preset threshold = 180.

14. The top-emitting OLED of claim 1, wherein, the charge generation layer comprises an N-type organic doped layer and a P-type organic doped layer stacked in order from the anode towards the cathode.

15. A display panel, characterized by comprising: a substrate; An array of OLEDs according to any of claims 1-14 formed on the substrate. An array of OLEDs according to any of claims 1-14 formed on the substrate.

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