Organic electroluminescent device and display device

Abstract

The present invention provides an organic electroluminescent device and display device. The organic electroluminescent device includes an organic light-emitting layer, the organic light-emitting layer including a carrier recombination zone and a carrier capture zone. The carrier recombination zone is a region where a first carrier injected into the organic light-emitting layer recombines with a second carrier. The organic light-emitting layer includes a light-emitting functional material, the light-emitting functional material having a greater mobility for the second carrier than for the first carrier. The carrier capture zone is provided on the path from the second carrier to the carrier recombination zone and includes a carrier capture material for capturing the second carrier. The present invention can improve carrier imbalance in the organic light-emitting layer, thereby alleviating the efficiency roll-off problem of the device and improving performance such as the device lifespan.

Description

Technical Field

[0001] The present invention relates to the field of display technology, and in particular to an organic electroluminescent device and a display apparatus. Background Art

[0002] An organic light emitting diode (OLED) is a device that emits light through current. Its luminescence properties primarily come from its organic light-emitting layer. When an appropriate voltage is applied, electrons and holes, two charge carriers, combine / recombine in the organic light-emitting layer to produce excitons, which then emit light of different wavelengths depending on the characteristics of the organic light-emitting layer.

[0003] In related technologies, organic light-emitting layers generally have a carrier imbalance phenomenon, that is, electron injection is too fast and hole injection is too slow, or hole injection is too fast and electron injection is too slow, resulting in serious device efficiency roll-off. Summary of the Invention

[0004] The present invention provides an organic electroluminescent device and a display apparatus, which at least solve the technical problems of carrier imbalance in an organic light-emitting layer and severe roll-off of device efficiency caused thereby in the prior art.

[0005] In one aspect of the present invention, an organic electroluminescent device is provided, comprising an organic light-emitting layer, the organic light-emitting layer comprising a carrier recombination zone and a carrier capture zone, the carrier recombination zone being a region where a first carrier injected into the organic light-emitting layer and a second carrier recombine, the organic light-emitting layer comprising a light-emitting functional material, the mobility of the light-emitting functional material to the second carrier being greater than its mobility to the first carrier, the carrier capture zone being arranged on a path for the second carrier to be transmitted to the carrier recombination zone, the carrier capture zone comprising a carrier capture material for capturing the second carrier.

[0006] According to one embodiment of the present invention, the organic light-emitting layer has a first side and a second side relative to each other, the first carriers are injected into the organic light-emitting layer from the first side, and the second carriers are injected into the organic light-emitting layer from the second side, and the distance from the carrier recombination zone to the first side is smaller than the distance from the carrier recombination zone to the second side.

[0007] According to one embodiment of the present invention, the first carriers are holes, and the second carriers are electrons; or, the first carriers are electrons, and the second carriers are holes.

[0008] According to one embodiment of the present invention, it also includes a hole transport region and an electron transport region, and the hole transport region, the organic light-emitting layer, and the electron transport region are stacked in sequence, wherein the second carrier is an electron, and the carrier recombination region and the carrier capture region are distributed in sequence along the direction from the hole transport region to the electron transport region; or, the second carrier is a hole, and the carrier recombination region and the carrier capture region are distributed in sequence along the direction from the electron transport region to the hole transport region; preferably, the hole transport region includes at least one of a hole injection layer, a hole transport layer, and an electron blocking layer; and / or, the electron transport region includes at least one of an electron injection layer, an electron transport layer, and a hole blocking layer.

[0009] According to one embodiment of the present invention, the distance between the carrier recombination zone and the carrier capture zone is L, the thickness of the organic light-emitting layer is H1, and L>70%×H1.

[0010] According to one embodiment of the present invention, the organic light-emitting layer is a red light-emitting layer, L>70%×H1; or, the organic light-emitting layer is a green light-emitting layer, L>75%×H1; or, the organic light-emitting layer is a blue light-emitting layer, L>85%×H1.

[0011] According to one embodiment of the present invention, the thickness of the carrier trapping region is H2, the thickness of the organic light emitting layer is H1, H2≤30%×H1; and / or the thickness of the carrier trapping region is 0.1 nm to 1 nm.

[0012] According to one embodiment of the present invention, the second carrier is an electron, and the carrier-trapping material includes rubrene and / or a compound having a structure shown in Formula I; preferably, the carrier-trapping material includes a compound having a structure shown in Formula I-1.

[0013] According to one embodiment of the present invention, the light-emitting functional material includes a host material, a sensitizer and a fluorescent material.

[0014] Another aspect of the present invention provides a display device comprising the above-mentioned organic electroluminescent device.

[0015] In the present invention, a carrier capture zone is set on the path of the second carrier being transmitted to the carrier recombination zone, so that the second carrier with a larger mobility first passes through the carrier capture zone and then is transmitted to the carrier recombination zone. The carrier capture zone contains a carrier capture material for capturing the second carrier. In this way, the second carrier passes through the carrier capture zone, is captured by the carrier capture material therein, and is then released. After such a capture and release process, the injection energy barrier of the second carrier under the initial brightness of the device (low brightness, low current) conditions can be improved, thereby alleviating the problem of the second carrier being injected too quickly and the first carrier being injected too slowly, improving the carrier imbalance phenomenon in the organic light-emitting layer, and then alleviating the efficiency roll-off problem of the device, and improving the life and other performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the light-emitting principle of the TSF device;

[0017] Figure 2 Schematic diagram of the light-emitting principle of the PSF device;

[0018] Figure 3 Schematic diagram of the structure of an organic electroluminescent device according to an embodiment of the present invention;

[0019] Figure 4 Schematic diagram of the structure of an organic electroluminescent device according to an embodiment of the present invention;

[0020] Figure 5 is a schematic structural diagram of an organic electroluminescent device according to another embodiment of the present invention;

[0021] Figure 6 is a schematic structural diagram of an organic electroluminescent device according to another embodiment of the present invention;

[0022] Figure 7 The luminescence spectra of the devices of Examples 1 to 4 are shown (the horizontal axis is wavelength, and the vertical axis is peak intensity).

[0023] Figure 8 1 is a graph showing the variation of luminous efficiency (Current eff.) versus luminance (Luminance) of the devices of Examples 1 to 4. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific embodiments listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of the present invention.

[0025] An organic light emitting diode (OLED) is a device that emits light through current. Its luminescence properties primarily come from its organic light-emitting layer. When an appropriate voltage is applied, electrons and holes, two charge carriers, combine / recombine in the organic light-emitting layer to produce excitons, which then emit light of different wavelengths depending on the characteristics of the organic light-emitting layer.

[0026] In related technologies, organic light-emitting layers generally have a carrier imbalance phenomenon, that is, electron injection is too fast and hole injection is too slow, or hole injection is too fast and electron injection is too slow, resulting in serious device efficiency roll-off.

[0027] For example, TSF (TADF sensitized flourescene) and PSF (Phosphor sensitized flourescene) OLED devices have received extensive attention and research. Their basic luminescence principle is that the luminescent layer is a triple-doped material composed of a host material, a sensitizer, and a fluorescent dye, that is, luminescence is generated through a triple-doping mechanism of the host material, the sensitizer, and the fluorescent dye. In the triple-doped luminescent layer, the recombination zone where electrons and holes meet and recombine is biased towards the interface of the luminescent layer, resulting in a carrier imbalance in the luminescent layer. For example, if the recombination zone is located at the interface of the luminescent layer near the hole transport zone, electrons are injected too quickly compared to holes. Alternatively, if the recombination zone is located at the interface of the luminescent layer near the electron transport zone, holes are injected too quickly compared to electrons, resulting in a carrier imbalance in the luminescent layer and a severe device efficiency roll-off. Specifically, the device achieves high efficiency under initial brightness (low brightness, low current) conditions, but the efficiency drops sharply as the voltage and brightness increase. In addition, the device brightness decay time is relatively slow. These problems seriously restrict the mass production feasibility of TSF and PSF devices and affect their actual industrial applications.

[0028] In view of the above problems, an embodiment of the present invention provides an organic electroluminescent device, such as Figures 3 to 6As shown, the organic electroluminescent device includes an organic light-emitting layer EML, the organic light-emitting layer includes a carrier recombination zone and a carrier capture zone, the carrier recombination zone is a region where the first carriers injected into the organic light-emitting layer recombine with the second carriers, the organic light-emitting layer includes a light-emitting functional material, the mobility of the light-emitting functional material to the second carrier is greater than its mobility to the first carrier, the carrier capture zone is arranged on the path of the second carrier being transmitted to the carrier recombination zone, and the carrier capture zone includes a carrier capture material for capturing the second carrier.

[0029] The mobility of the light-emitting functional material in the organic light-emitting layer to the second carrier is greater than its mobility to the first carrier. The second carrier is injected too quickly relative to the first carrier, which easily leads to carrier imbalance in the organic light-emitting layer. In the embodiment of the present application, a carrier capture region is set on the path of the second carrier being transmitted to the carrier recombination region, so that the second carrier with a larger mobility first passes through the carrier capture region and then is transmitted to the carrier recombination region to recombine with the first carrier. The carrier capture region contains a carrier capture material for capturing the second carrier. , the carrier capture material easily loses the second carrier and captures the second carrier. In this way, the second carrier passes through the carrier capture area, is captured by the carrier capture material therein and then released. After such a capture-release process, the injection energy barrier of the second carrier under the initial brightness of the device (low brightness, low current) conditions can be improved, thereby alleviating the problem of the second carrier injection being too fast and the first carrier injection being too slow, improving the carrier imbalance phenomenon in the organic light-emitting layer, and then alleviating the efficiency roll-off problem of the device, and improving the device's life and other performance.

[0030] It can be understood that the polarity of the first carrier is opposite to that of the second carrier, that is, Figure 3 and Figure 4 As shown, the first carrier is the hole h + , the second carrier is electron e - , or, as Figure 5 and Figure 6 As shown, the first carrier is the electron e - , the second carrier is hole h + .

[0031] The carrier capture material has a strong second carrier capture property, which can capture and release the second carrier. Through the capture and release process of the second carrier, the injection energy barrier of the second carrier under the initial brightness conditions of the device can be increased, thereby reducing the injection efficiency of the second carrier and reducing the rapid accumulation of the second carrier in the carrier recombination zone under low current conditions, thereby reducing the luminous efficiency of the device at low brightness / low current and alleviating the efficiency roll-off of the device.

[0032] Specifically, the carrier capture material is an organic material and usually does not contain inorganic materials, which can improve the performance of the device, such as the life span.

[0033] When the second carrier is an electron e - When the carrier capture material is an electron capture material, it can capture and release electrons e - , increase the electron e - The injection energy barrier under the initial brightness conditions of the device prevents its rapid accumulation in the carrier recombination zone, thereby reducing the luminous efficiency of the device at low brightness / low current and alleviating the efficiency roll-off of the device.

[0034] In some embodiments, the electron capture material may include rubrene and / or a compound having a BN and / or BO bond skeleton structure, wherein the compound skeleton structure has a modifying group around it, and the modifying group may include an alkyl group and / or an aryl group. For example, it may specifically be a compound having a structure shown in the following formula I:

[0035]

[0036] wherein R1, R2, R3, R4, R5, and R6 are each independently monosubstituted to the maximum permissible substituent, and R1, R2, R3, R4, R5, and R6 are each independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl.

[0037] In some embodiments, the carrier capture material includes a compound having a structure shown in the following formula I-1:

[0038]

[0039] Among them, R 11 、R 12 、R 21 、R 22 、R 31 、R 41 、R 51 、R 61 are each independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl.

[0040] Illustratively, the substituted or unsubstituted alkyl group is, for example, a C1 to C6 alkyl group, such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, etc. These alkyl groups can be isomeric alkyl groups with branches, such as isopropyl group, tert-butyl group, etc., or can be straight-chain alkyl groups without branches; substituted or unsubstituted aryl groups include, for example, substituted or unsubstituted phenyl groups.

[0041] For example, R 12 、R 21are each independently hydrogen, R 11 、R 22 are each independently selected from substituted or unsubstituted aryl, for example phenyl, R 31 、R 41 、R 51 、R 61 are each independently a substituted or unsubstituted alkyl group, for example, a tert-butyl group; or, R 11 、R 22 are each independently hydrogen, R 12 、R 21 are each independently selected from substituted or unsubstituted aryl, for example phenyl, R 31 、R 41 、R 51 、R 61 Each is independently a substituted or unsubstituted alkyl group, for example, a tert-butyl group.

[0042] In some embodiments, the carrier-trapping material may include one or more of the following compounds of Formula I-11 to Formula I-19:

[0043]

[0044]

[0045] When the second carrier is a hole h + When the carrier capture material is a hole capture material, it can capture and release holes h + , increase the hole h + The injection energy barrier under the initial brightness conditions of the device prevents its rapid accumulation in the carrier recombination zone, thereby reducing the luminous efficiency of the device at low brightness / low current and alleviating the efficiency roll-off of the device.

[0046] In addition, the luminescent functional material is a material for realizing an organic electroluminescent device, which may specifically include a host material, a sensitizer, and a fluorescent material, that is, the organic light-emitting layer of the embodiment of the present invention may be a three-doping system. Among them, the mass content of the sensitizer may be 1% to 10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or a range consisting of any two thereof, the mass content of the fluorescent material (dye) may be 0.1% to 1.2%, for example, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2% or a range consisting of any two thereof, and the mass content of the host material may be 88.8% to 98.9%, for example, 88.8%, 90%, 92%, 95%, 97%, 98.9% or a range consisting of any two thereof.

[0047] Among them, the host material, sensitizer and fluorescent material can be conventional materials in this field. For example, the sensitizer can include a thermally activated delayed fluorescence (TADF) material and / or a phosphorescent material (or phosphorescent sensitizer), and the fluorescent material can include a resonant narrow spectrum fluorescent material, etc.

[0048] Specifically, the organic electroluminescent device can be a TSF device, and accordingly, the sensitizer in its organic light-emitting layer is a TADF material. Alternatively, the organic electroluminescent device can also be a PSF device, and accordingly, the sensitizer in its organic light-emitting layer is a phosphorescent material. In the embodiments of the present application, by providing a carrier capture region containing a second carrier capture material, the efficiency roll-off problem of these devices can be solved. Specifically, the luminous efficiency under the initial brightness conditions of the device can be reduced, and the phenomenon of a sudden drop in luminous efficiency with increasing voltage and brightness, as well as a slow device brightness decay time, can be avoided.

[0049] The main material in the above-mentioned organic light-emitting layer can be a single main material or include multiple (at least two) main materials. The above-mentioned main material, TADF material, phosphorescent material, and fluorescent material can be conventional materials of each of these materials in the field, and their contents can also be the conventional contents of each of these materials in the organic light-emitting layer in the field, and there is no special restriction on this.

[0050] In general, the main material in the organic light-emitting layer is the main factor affecting the mobility of the first carrier and the second carrier. If the electron mobility of the main material is greater than the hole mobility, the second carrier is the electron e - , the mobility of the second carrier of the light-emitting functional material is basically equal to the electron mobility of the main material, and accordingly, the first carrier is the hole h + , the mobility of the first carrier of the light-emitting functional material is basically equal to the hole mobility of the main material; if the hole mobility of the main material is greater than the electron mobility, the second carrier is the hole h + The mobility of the second carrier of the light-emitting functional material is basically equal to the hole mobility of the main material. Correspondingly, the first carrier is the electron e - , the mobility of the first carrier of the light-emitting functional material is basically equal to the electron mobility of the main material.

[0051] Specifically, the first carrier and the second carrier are injected into the organic light-emitting layer from opposite sides thereof respectively. The second carrier is injected too fast relative to the first carrier, and the carrier recombination region is generally closer to the first carrier injection side and away from the second carrier injection side.

[0052] Specifically, the organic light-emitting layer has a first side 101 and a second side 102 opposite to each other, the first carrier is injected into the organic light-emitting layer from the first side 101, and the second carrier is injected into the organic light-emitting layer from the second side 102, and the carrier recombination region and the carrier capture region are sequentially distributed along the direction from the first side 101 to the second side 102, and the direction from the carrier recombination region to the carrier capture region is the same as the direction from the first side 101 to the second side 102 (i.e., Figures 3 to 6 The same as the first direction indicated by the arrow in .

[0053] The distance L3 from the carrier recombination zone to the first side 101 is smaller than the distance L4 from the carrier recombination zone to the second side 102, that is, the carrier recombination zone is closer to the first side 101 (that is, the first carrier injection side), and the mobility of the second carrier is too fast relative to the mobility of the second carrier.

[0054] like Figures 3 to 6 As shown, L3 can specifically be the distance from the side of the carrier recombination zone facing the first side 101 to the first side 101 in the first direction, and L4 can specifically be the distance from the side of the carrier recombination zone facing the second side 102 to the second side 102 in the first direction.

[0055] The carrier recombination zone may be located at the boundary of the first side 101 of the organic light-emitting layer, and L3 may be equal to or greater than 0 (ie, L3 ≥ 0).

[0056] The embodiments of the present invention can determine the position of the carrier recombination zone in the organic light-emitting layer by conventional methods in the field, for example, by introducing a tracer into a preset area of ​​the organic light-emitting layer to determine the position of the carrier recombination zone. The tracer can absorb the energy of the light-emitting functional material used in the organic light-emitting layer, thereby losing the energy of the light-emitting functional material, resulting in a decrease in the luminous efficiency of the device. Generally, the closer the preset area where the tracer is introduced is to the carrier recombination area, the greater the energy loss of the light-emitting functional material caused by it, and the lower the luminous efficiency of the device. Therefore, when the tracer is doped in the carrier recombination area in the organic light-emitting layer, the energy loss of the light-emitting functional material is the largest and the device efficiency is the lowest. Therefore, it can be determined that when the luminous efficiency of the device is the lowest, the preset area in the organic light-emitting layer doped with the tracer is the carrier recombination zone.

[0057] For example, if the organic light-emitting layer is a red light-emitting layer, the tracer can be a material that emits red light. The wavelength of the red light emitted by the tracer is longer than that of the red light emitted by the light-emitting material in the organic light-emitting layer. This means that the tracer can emit redder red light, facilitating monitoring. Furthermore, the tracer can also have the ability to capture secondary charge carriers, meaning it can capture and then release secondary charge carriers. In other words, the tracer can be a carrier-trapping material that captures secondary charge carriers.

[0058] For example, the organic light-emitting layer is a red light-emitting layer, and the second carrier is an electron e - , the tracer used can be a deep red fluorescent dye, such as rubrene, which can not only emit redder red light but also capture and release electrons, acting as an electron capture material.

[0059] Specifically, the above-mentioned organic light-emitting layer can be a red light-emitting layer that emits red light, a green light-emitting layer that emits green light, or a blue light-emitting layer that emits blue light, and the above-mentioned organic electroluminescent device can be a red light device, a green light device, a blue light device, or other conventional devices in the field.

[0060] In addition, if Figures 3 to 6 As shown, the distance L1 from the carrier capture region to the first side 101 is generally greater than the distance L2 from the carrier capture region to the second side 102, that is, the carrier recombination region and the carrier capture region are respectively located on opposite sides of the organic light-emitting layer, which is beneficial to alleviating the carrier balance in the organic light-emitting layer. At the same time, the setting of the carrier capture region basically does not affect the driving voltage and electroluminescence spectrum of the device, thereby improving the luminescence performance of the device.

[0061] like Figures 3 to 6 As shown, L1 can specifically be the distance from the side of the carrier capture region facing the first side 101 to the first side 101 in the first direction, and L2 can specifically be the distance from the side of the carrier capture region facing the second side 102 to the second side 102 in the first direction.

[0062] Generally, L2>0, that is, a second region without carrier-trapping material is present between the carrier-trapping region and the second side 102 .

[0063] Specifically, if Figures 3 to 6 As shown, the organic light-emitting layer includes a first region, the carrier-trapping region, and the second region. The first region, the carrier-trapping region, and the second region are sequentially connected. The second region, the carrier-trapping region, and the first region are sequentially distributed along a first direction, with the carrier recombination zone located in the first region. The thickness of the first region in the first direction is equal to L1, and the thickness of the second region in the first direction is equal to L2.

[0064] In addition, the distance between the carrier recombination zone and the carrier capture zone is L, and L>0.

[0065] In some embodiments, the thickness of the organic light emitting layer is H1, and L>70%×H1.

[0066] Generally, when the light-emitting layers are organic light-emitting layers of different colors, the device performance can be further optimized by adjusting the relationship between L and H1.

[0067] Specifically, when the organic light-emitting layer is a red light-emitting layer, L>70%×H1. For example, when the organic electroluminescent device is a red light-emitting device, its organic light-emitting layer is a red light-emitting layer. Controlling L>70%×H1 can further balance the first and second carriers in the organic light-emitting layer, alleviate carrier imbalance, and improve the performance of the red light-emitting device.

[0068] When the organic light-emitting layer is a green light-emitting layer, L>75%×H1. For example, when the organic electroluminescent device is a green light-emitting device, its organic light-emitting layer is a green light-emitting layer. Controlling L>75%×H1 can further balance the first carrier and the second carrier in the organic light-emitting layer, alleviate the carrier imbalance phenomenon, and improve the performance of the green light-emitting device.

[0069] When the organic light-emitting layer is a blue light-emitting layer, L>85%×H1. For example, when the organic electroluminescent device is a blue light-emitting device, its organic light-emitting layer is a blue light-emitting layer. Controlling L>85%×H1 can further balance the first and second carriers in the organic light-emitting layer, alleviate carrier imbalance, and improve the performance of the blue light-emitting device.

[0070] In some embodiments, the thickness of the carrier capture region is H2, H2≤30%×H1, and H2 / H1 is, for example, 1%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30% or a range consisting of any two thereof.

[0071] Specifically, the thickness H2 of the carrier-trapping region can be 0.1 nm to 1 nm, for example, 0.1 nm, 0.2 nm, 0.5 nm, 0.8 nm, 1 nm, or any range between two thereof. By controlling the thickness of the carrier-trapping region H2 within the above range, the carrier balance in the organic light-emitting layer can be effectively improved while also improving the luminescence performance of the device.

[0072] Specifically, the thickness direction of the carrier trapping region and the thickness direction of the organic light-emitting layer are parallel to the first direction.

[0073] In some embodiments, the carrier capture region may include a luminescent functional material, and the carrier capture material is mixed in the luminescent functional material, that is, the carrier capture region may be composed of a luminescent functional material (including the above-mentioned main material, sensitizer and fluorescent material) and a carrier capture material.

[0074] In specific implementation, the light-emitting functional material can be evaporated to form an organic light-emitting layer. After the evaporation time is preset, the first area is formed, and then the carrier capture material is started to be evaporated, and the light-emitting functional material is kept evaporated, that is, the carrier capture material and the light-emitting functional material are evaporated at the same time, so that the carrier capture area formed includes the light-emitting functional material and the carrier capture material mixed in the light-emitting functional material. The carrier capture material is evaporated for a preset time to form a carrier capture area with a preset thickness H2, and then the carrier capture material is stopped from being evaporated, and the light-emitting functional material is kept evaporated for a preset time to form a second area, thereby preparing the organic light-emitting layer.

[0075] In other embodiments, the carrier capture region does not include a light-emitting functional material, and may include a carrier capture material layer formed by the carrier capture material, that is, the carrier capture material exists in the carrier capture material layer, and the carrier capture material layer does not include a light-emitting functional material, and may only contain carrier capture material.

[0076] In specific implementation, the light-emitting functional material can be evaporated to form an organic light-emitting layer. After the evaporation is performed for a preset time, a first area is formed, and then the carrier capture material is evaporated, and the light-emitting functional material is evaporated, that is, only the carrier capture material is evaporated, so that the carrier capture area formed is a carrier capture material layer formed by the carrier capture material. The carrier capture material is evaporated for a preset time to form a carrier capture area with a preset thickness H2. Then the carrier capture material is stopped and the light-emitting functional material is evaporated. After the preset time, the second area is formed, thereby obtaining an organic light-emitting layer.

[0077] Specifically, if Figures 3 to 6 As shown, the organic electroluminescent device further includes a hole transport region and an electron transport region, and the hole transport region, the organic light-emitting layer, and the electron transport region are stacked in sequence.

[0078] like Figure 3 and Figure 4 As shown, when the second carrier is electron e - When the organic light-emitting layer is formed, the first side 101 is the side of the organic light-emitting layer facing the hole transport region, and the second side 102 is the side of the organic light-emitting layer facing the electron transport region. The carrier recombination region and the carrier capture region can be distributed in sequence along the direction from the hole transport region to the electron transport region (the first direction).

[0079] like Figure 5 and Figure 6 As shown, when the second carrier is a hole h + When the organic light-emitting layer is formed, the first side 101 of the organic light-emitting layer is the side of the organic light-emitting layer facing the electron transport region, the second side 102 is the side of the organic light-emitting layer facing the hole transport region, and the carrier recombination region and the carrier capture region are distributed in sequence along the direction from the electron transport region to the hole transport region.

[0080] Specifically, the hole transport region may include at least one of a hole injection layer HIL, a hole transport layer HTL, and an electron blocking layer EBL. When the hole injection layer HIL and the hole transport layer HTL are included, the hole injection layer HIL, the hole transport layer HTL, and the organic light-emitting layer EML are stacked in sequence; when the hole injection layer HIL, the hole transport layer HTL, and the electron blocking layer EBL are included, the hole injection layer HIL, the hole transport layer HTL, the electron blocking layer EBL, and the organic light-emitting layer EML are stacked in sequence (e.g., Figure 4 and Figure 6 shown).

[0081] In addition, the electron transport region may include at least one of an electron injection layer EIL, an electron transport layer ETL, and a hole blocking layer HBL. When the electron injection layer EIL and the electron transport layer ETL are included, the electron injection layer EIL, the electron transport layer ETL, and the organic light-emitting layer EML are stacked in sequence; when the electron injection layer EIL, the electron transport layer ETL, and the hole blocking layer HBL are included, the electron injection layer EIL, the electron transport layer ETL, the hole blocking layer HBL, and the organic light-emitting layer EML are stacked in sequence (such as Figure 4 and Figure 6 shown).

[0082] In addition, the organic electroluminescent device further comprises an anode and a cathode, wherein the anode, the hole transport region, the organic light emitting layer, the electron transport region and the cathode are stacked in sequence.

[0083] Specifically, the organic electroluminescent device may be a top-emitting device or a bottom-emitting device.

[0084] In some embodiments, as Figures 3 to 6 As shown, the above-mentioned organic electroluminescent device may further include a light extraction layer CPL, which is located on the side of the cathode away from the organic light-emitting layer / electron transport region, that is, the organic light-emitting layer, electron transport region, cathode, and light extraction layer are stacked in sequence.

[0085] The organic electroluminescent device also includes a substrate. The anode can be formed on the substrate by sputtering or depositing an anode material. The remaining layers can be formed by conventional methods in the art, such as vacuum thermal evaporation, spin coating, and printing, and will not be described in detail. The substrate can be made of glass or a polymer material with excellent mechanical strength, thermal stability, water resistance, and transparency. Furthermore, the substrate used for the display can also include thin-film transistors (TFTs).

[0086] In the embodiment of the present invention, unless otherwise specified, the materials of the layers described above may be conventional materials of these layers in the art, and their thicknesses may also be conventional thicknesses of these layers in the art, and the embodiment of the present invention does not impose any particular limitation on this.

[0087] For example, the cathode material can be metals or alloys such as magnesium (Mg), silver (Ag), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag), and any combination thereof.

[0088] For example, the hole transport injection layer HIL includes a hole transport material (HT) and a p-type dopant material (PD). HT includes, for example, the following compound HTM, and PD includes, for example, NDP-9.

[0089]

[0090] For example, the anode may include an oxide transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), tin dioxide (SnO 2 ), zinc oxide (ZnO), and any combination thereof.

[0091] In some embodiments, the above-mentioned organic electroluminescent device can be a top-emitting device (or top-emitting device), and the substrate structure with an anode can be a top-emitting substrate structure conventionally used for top-emitting devices in the art. For example, the substrate structure with an anode includes an ITO layer, a silver layer, and an ITO layer (i.e., ITO-Ag-ITO) stacked in sequence.

[0092] An embodiment of the present invention further provides a display device comprising the aforementioned organic electroluminescent device. Specifically, the display device may be a display device such as an OLED display, as well as any product or component with a display function, such as a television, digital camera, mobile phone, or tablet computer, that incorporates the display device. The advantages of this display device over the prior art are the same as those of the aforementioned organic electroluminescent device, and are not further elaborated here.

[0093] The organic electroluminescent device according to the embodiment of the present invention is further described below by taking a red light device as an example through specific embodiments.

[0094] The device in the following embodiment is a red bottom light emitting device, and its structure is: ITO (50nm) / HIL (10nm) / HTL (100nm) / EBL (60nm) / EML (40nm) / HBL (5nm) / ETL (30nm) / EIL (1nm) / Mg-Ag (100nm).

[0095] Among them, the anode is ITO with a thickness of 50nm;

[0096] The thickness of the HIL is 10 nm, and its materials include the following compounds HTM and NDP-9, wherein the mass concentration of NDP-9 is 3%;

[0097]

[0098] The thickness of HTL is 100 nm and its material is the above-mentioned HTM;

[0099] The thickness of the EBL is 80 nm and its material is the following compound EBM:

[0100]

[0101] The thickness of the EML is H1 = 40 nm. The light-emitting functional materials thereof include a host material, a sensitizer, and a fluorescent material. The mass content of the sensitizer is 5%, and the mass content of the fluorescent material is 0.8%. The host material, sensitizer, and fluorescent material are the following compounds, respectively:

[0102]

[0103] The thickness of HBL is 5 nm and its material is Bphen;

[0104] The thickness of the ETL is 30 nm, and its materials include the following compounds ET and Liq, with a mass ratio of ET to Liq of 1:1:

[0105]

[0106] The thickness of the EIL is 1 nm and its material is Yb;

[0107] The thickness of the cathode is 100 nm, and the material thereof is Mg-Ag, with a mass ratio of Mg to Ag being 1:9.

[0108] The above device was used to carry out the following Examples 1-4:

[0109] Example 1: No tracer EY01 is provided in the EML, which is a standard light-emitting layer structure formed by a host material, a sensitizer and a fluorescent material;

[0110] Example 2: A tracer EY01 is introduced into a predetermined region of the EML. The distance L1′ from the center of the predetermined region to the side of the EML facing the EBL (the first side 101) is 4 nm. The thickness H2′ of the predetermined region is 0.5 nm.

[0111] Example 3: A tracer EY01 is introduced into a predetermined region of the EML. The distance L1′ from the center of the predetermined region to the side of the EML facing the EBL (the first side 101 ) is 15 nm. The thickness H2′ of the predetermined region is 0.5 nm.

[0112] Example 4: A tracer EY01 is introduced into a predetermined region of the EML, the distance L1′ from the center of the predetermined region to the side of the EML facing the EBL (the first side 101 ) is 36 nm, and the thickness H2′ of the predetermined region is 0.5 nm.

[0113] The emission spectra of the devices of Examples 1 to 4 are measured. Figure 7 , the curve of luminous efficiency changing with brightness is shown in Figure 8 The emission spectrum peak Wav, half-maximum width FWHM, voltage Vop when reaching the target brightness (6000 nit), and luminous efficiency Eff when reaching the target brightness (6000 nit) of the devices of Examples 1 to 4 are measured and shown in Table 1.

[0114] From Table 1 and Figure 8 It can be seen that the luminous efficiency of the device of Example 2 is the lowest. It can be determined that the preset area doped with EY01 in the EML of the device of this embodiment is basically the carrier recombination zone of the EML. It can be seen that the carrier recombination zone is closer to the hole injection side (the first side 101 of the EML), and its distance L3 to the first side 101 of the EML is approximately 4nm-0.5nm / 2=3.75nm, and its distance L4 to the second side 102 of the EML (the electron injection side) is approximately 40nm-4nm-0.5nm / 2=35.75nm.

[0115] Combined with the test results of Example 1, it can be seen that under the initial brightness of the device (low brightness, low current) conditions, electrons (second carriers) are easily injected, that is, electrons are injected too fast compared to holes (first carriers), resulting in the device having a higher luminous efficiency under low brightness / low current conditions. However, as the driving voltage and brightness increase, the luminous efficiency of the device decreases, the brightness decay time is low, and the efficiency roll-off phenomenon is serious.

[0116] Since EY01 has electron capture properties and can capture and release electrons, in Examples 3 and 4, EY01 is used as an electron capture material (i.e., a carrier capture material for capturing second carriers). Accordingly, the preset area doped with EY01 in the EML is the carrier capture region. The thickness H2 (H2=H2') of the carrier capture region, the distance L1 from the carrier capture region to the first side 101 of the EML, the distance L2 from the carrier capture region to the second side 102 of the EML (the side of the EML facing the HBL), and the distance L between the carrier capture region and the carrier recombination region are summarized in Table 1.

[0117] The test results of Examples 3 and 4 show that placing the electron capture material EY01 away from the carrier recombination zone to form a carrier capture zone can reduce the device's luminous efficiency under initial brightness (low brightness, low current) conditions. In Example 4, the distance L1 from the carrier recombination zone to the EML first side 101 is less than the distance L2 to the EML second side 102, where L>70%×H1. This effectively mitigates the device's efficiency roll-off while substantially unaffecting the device's driving voltage and electroluminescence spectrum.

[0118] Table 1

[0119]

[0120] With reference to the above-mentioned Example 4, devices of Examples 5 to 7 were prepared. The difference between them and Example 4 is that different electron capture materials are used, as shown in Table 2. Except for the difference shown in Table 2, the other conditions are basically the same.

[0121] The curves of the luminous efficiency (Current eff) versus brightness (Luminance) of the devices of Examples 5 to 7 are similar to those of the device of Example 4, which can reduce the luminous efficiency of the device under initial low brightness / low current conditions, effectively alleviate the efficiency roll-off problem of the device, and basically do not affect the driving voltage and electroluminescence spectrum of the device. The emission spectrum peak Wav of the devices of Examples 5 to 7 are all around 610nm, and the half-maximum width FWHM are all around 54nm. The voltage Vop when the target brightness (6000nit) is reached, the luminous efficiency Eff when the target brightness (6000nit) is reached, and the LT95 lifespan are shown in Table 2. Among them, the luminance meter is used at a current density of 50mA / cm 2 The LT95 life of the device (i.e. the time when the device reaches 95% of the initial brightness, in hours) is measured under the conditions of

[0122] Table 2

[0123]

[0124] It can be seen that the electron mobility in the organic light-emitting layer is greater than the mobility of the holes, that is, the electrons are injected too fast relative to the holes. By setting an electron capture zone doped with electron capture, the injection energy barrier of electrons under the initial brightness of the device (low brightness, low current density) can be improved to avoid excessive injection, thereby alleviating the imbalance of electron and hole injection in the organic light-emitting layer and the resulting device efficiency roll-off problem, thereby improving the device's life and other performance.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An organic electroluminescent device, characterized in that: The organic light-emitting layer includes an organic light-emitting layer, the organic light-emitting layer includes a carrier recombination zone and a carrier capture zone, the carrier recombination zone is a region where a first carrier injected into the organic light-emitting layer and a second carrier recombine, the organic light-emitting layer includes a light-emitting functional material, the mobility of the light-emitting functional material to the second carrier is greater than its mobility to the first carrier, the carrier capture zone is provided on a path where the second carrier is transmitted to the carrier recombination zone, the carrier capture zone includes a carrier capture material for capturing the second carrier; the second carrier is an electron, and the carrier capture material includes rubrene and / or a compound having a structure shown in the following formula I: Formula I wherein R1, R2, R3, R4, R5, and R6 are each independently monosubstituted to the maximum permissible substituent, and R1, R2, R3, R4, R5, and R6 are each independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl.

2. The organic electroluminescent device according to claim 1, wherein The organic light-emitting layer has a first side and a second side relative to each other, the first carriers are injected into the organic light-emitting layer from the first side, and the second carriers are injected into the organic light-emitting layer from the second side, and the distance from the carrier recombination zone to the first side is smaller than the distance from the carrier recombination zone to the second side.

3. The organic electroluminescent device according to claim 1, wherein The first carriers are holes, and the second carriers are electrons.

4. The organic electroluminescent device according to claim 1, wherein It also includes a hole transport region and an electron transport region, wherein the hole transport region, the organic light emitting layer, and the electron transport region are stacked in sequence, wherein: The second carriers are electrons, and the carrier recombination zone and the carrier capture zone are distributed in sequence along the direction from the hole transport zone to the electron transport zone.

5. The organic electroluminescent device according to claim 4, characterized in that: The hole transport region includes at least one of a hole injection layer, a hole transport layer, and an electron blocking layer; and / or the electron transport region includes at least one of an electron injection layer, an electron transport layer, and a hole blocking layer.

6. The organic electroluminescent device according to any one of claims 1 to 4, characterized in that: The distance between the carrier recombination zone and the carrier capture zone is L, the thickness of the organic light-emitting layer is H1, and L>70%×H1.

7. The organic electroluminescent device according to claim 6, characterized in that: The organic light-emitting layer is a red light-emitting layer, L>70%×H1; Alternatively, the organic light-emitting layer is a green light-emitting layer, L>75%×H1; Alternatively, the organic light-emitting layer is a blue light-emitting layer, and L>85%×H1.

8. The organic electroluminescent device according to claim 1, wherein The thickness of the carrier capture region is H2, the thickness of the organic light-emitting layer is H1, and H2≤30%×H1; And / or, the thickness of the carrier capture region is 0.1 nm to 1 nm.

9. The organic electroluminescent device according to any one of claims 1 to 4, characterized in that: The carrier capture material includes a compound having a structure shown in the following formula I-1: Formula I-1 Among them, R 11 、R 12 、R 21 、R 22 、R 31 、R 41 、R 51 、R 61 are each independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl.

10. The organic electroluminescent device according to claim 1, wherein The light-emitting functional material includes a host material, a sensitizer and a fluorescent material.

11. A display device, characterized in that: The organic electroluminescent device comprises the organic electroluminescent device according to any one of claims 1 to 10.

Images