Light-emitting device and display device

Abstract

The invention relates to a light emitting device and a display apparatus including the same. The light-emitting device comprises a cathode, an electron transmission layer and a light-emitting layer which are arranged in a stacked mode, the electron transmission layer comprises a transmission function layer, and the transmission function layer is used for reducing the electron transmission rate from the cathode to the light-emitting layer. According to the light-emitting device provided by the invention, the transmission function layer which can be used for reducing the electron transmission rate from the cathode to the light-emitting layer is introduced into the electron transmission layer, so that the effect of relieving charge accumulation at an interface is achieved, and the efficiency of the light-emitting device is improved.

Description

Technical Field

[0001] The present invention relates to the field of electroluminescence technology, and particularly to a light-emitting device and a display device including the light-emitting device. Background Art

[0002] Benefiting from the unique optical properties of quantum dots, such as continuously tunable emission wavelength with size and composition, narrow emission spectrum, high fluorescence efficiency, good stability, etc., quantum dot-based light-emitting diodes (QLEDs) have received extensive attention and research in the display field. At the same time, QLED displays also have many excellent features for future displays, such as foldability, rollability, fast response speed, large viewing angle, high contrast, etc., and thus are expected to become the next-generation display technology.

[0003] However, current QLEDs still have some problems, which lead to a decrease in device efficiency and performance. Summary of the Invention

[0004] In order to improve the above problems existing in the prior art, the present invention provides a light-emitting device and a display device including the light-emitting device.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A first aspect of the present invention provides a light-emitting device, including: a cathode, an electron transport layer, and a light-emitting layer stacked, wherein the electron transport layer includes a transport functional layer for reducing the electron transport rate from the cathode to the light-emitting layer.

[0007] In one example, the electron transport layer further includes an electron transport sub-layer stacked with the transport functional layer, the electron transport sub-layer at least includes a first metal oxide, the transport functional layer at least includes a second metal oxide, and the electron mobilities of the first metal oxide and the second metal oxide are not equal.

[0008] In one example, the electron transport sub-layer further includes the second metal oxide.

[0009] In one example, the doping ratio of the second metal oxide in the electron transport sub-layer is 0.01 wt%-50 wt%.

[0010] In one example, the thickness of the electron transport sub-layer is greater than or equal to the thickness of the transport functional layer.

[0011] In one example, the thickness of the electron transport sub-layer is 10 nm - 100 nm, and the thickness of the transport functional layer is 0 nm - 50 nm.

[0012] The second aspect of the present invention provides a display device, and the display device includes the light-emitting device described in the first aspect of the present invention.

[0013] Through the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0014] The light-emitting device provided by the present invention can reduce the electron transport rate of the electron transport layer by providing a transport functional layer capable of reducing the electron transport rate from the cathode to the light-emitting layer in the electron transport layer, thereby alleviating the charge accumulation at the interface between the electron transport layer and the quantum dot light-emitting layer, avoiding exciton quenching in the quantum dot light-emitting layer, and thus improving the efficiency of the light-emitting device.

[0015] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. Description of the Drawings

[0016] Figure 1 The following shows the structural schematic diagram of the light-emitting device provided in an embodiment of the present invention Figure 1 ;

[0017] Figure 2 The following shows the structural schematic diagram of the light-emitting device provided in an embodiment of the present invention Figure 2 ;

[0018] Figure 3 The following shows the structural schematic diagram of the light-emitting device provided in an embodiment of the present invention Figure 3 ;

[0019] Figure 4 The following shows the structural schematic diagram of the light-emitting device provided in an embodiment of the present invention Figure 4 ;

[0020] Figure 5 The following shows the structural schematic diagram of the inverted light-emitting device provided in an embodiment of the present invention.

[0021] Reference Signs:

[0022] Cathode - 1, Electron Transport Layer - 2, Electron Transport Sub - layer - 21, Transport Functional Layer - 22, Light - Emitting Layer - 3, Hole Transport Layer - 4, Hole Injection Layer - 5, Anode - 6. Detailed Embodiments

[0023] The following provides a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for illustrating and explaining the present invention, and are not used to limit the present invention.

[0024] In the case of using "including", "having", and "comprising" described herein, it is intended to cover non-exclusive inclusion. Unless explicit limiting terms are used, such as "only", "consisting of", etc., another component can also be added.

[0025] It should be understood that in the description and claims of this application, terms such as "first", "second", etc. can be used to describe various elements, but these elements should not be limited by these terms. These terms are only used to distinguish one element from another. "First", "second", etc. are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. For example, without departing from the scope of the present invention, the first element can be referred to as the second element, and similarly, the second element can be referred to as the first element.

[0026] Common quantum dot light-emitting diodes (QLEDs) generally have an organic-inorganic hybrid structure, and there will be a large amount of charge accumulation at the interface between the quantum dot light-emitting layer (QD) and the electron transport layer (ETL), resulting in a decline in device performance.

[0027] Based on this, the first aspect of the present invention provides a light-emitting device, as Figure 1 and Figure 2 shown, including: a cathode 1, an electron transport layer 2, and a light-emitting layer 3 arranged in a stacked manner. The electron transport layer 2 includes a transport functional layer 22, and the transport functional layer 22 is used to reduce the electron transport rate from the cathode to the light-emitting layer. It can be understood that the transport functional layer can reduce the electron transport rate from the cathode to the light-emitting layer, making the electron injection and transport capabilities tend to be balanced with the hole injection and transport capabilities, avoiding excessive electron injection and resulting in charge accumulation, thereby improving the light-emitting efficiency and properties of the device. It should be noted that in the present invention, in addition to the materials of the transport functional layer, the electron transport layer also includes one or more of the commonly used electron transport layer materials in the technical field for electron transport within the device.

[0028] In a specific embodiment, as Figure 2 shown, the electron transport layer 2 further includes an electron transport sub-layer 21 stacked with the transport functional layer 22. The electron transport sub-layer 21 at least includes a first metal oxide, and the transport functional layer 22 at least includes a second metal oxide, and the electron mobilities of the first metal oxide and the second metal oxide are not equal.

[0029] In the present invention, the electron mobility has its conventional meaning in the art, which refers to the average velocity of electrons under the action of a unit electric field, that is, a measure of the speed of electron movement under the action of an electric field. The faster the movement, the greater the mobility; the slower the movement, the smaller the mobility. The unit is [m 2 / (V·s) or cm 2 / (V·s)]. The electron transport sublayer and the transport functional layer of the present invention respectively comprise two metal oxides with unequal electron mobilities, which can reduce the electron transport efficiency of the oxide layer with a larger electron mobility, thereby alleviating the charge accumulation at the interface between the light-emitting layer and the electron transport layer, and further improving the efficiency of the device.

[0030] In a specific embodiment, the electron transport sublayer, the transport functional layer and the light-emitting layer are stacked in sequence, or the transport functional layer, the electron transport sublayer and the light-emitting layer are stacked in sequence. It can be understood that in the present invention, with reference to Figure 2 , there is no special limitation on the stacking order of the electron transport sublayer 21 and the transport functional layer 22. For example, as shown in FIG. a) in Figure 2 , the light-emitting device may include a cathode 1, an electron transport sublayer 21, a transport functional layer 22, and a light-emitting layer 3 stacked in sequence; or, as shown in FIG. b) in Figure 2 , the light-emitting device may include a cathode 1, a transport functional layer 22, an electron transport sublayer 21, and a light-emitting layer 3 stacked in sequence. The electron transport layer of the present invention is provided with a transport functional layer with an electron mobility unequal to that on either side of the electron transport sublayer, which can reduce the electron transport efficiency of the electron transport oxide layer, thereby alleviating the charge accumulation at the interface between the quantum dot light-emitting layer and the electron transport layer, and further improving the efficiency of the device.

[0031] In a specific embodiment, in order to further reduce the electron transport efficiency of the electron transport layer and alleviate the charge accumulation problem at the interface, the electron transport sub-layer further includes the second metal oxide. Specifically, the doping ratio of the second metal oxide in the electron transport sub-layer is 0.01 wt% - 50 wt%, for example: 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, and a typical example is 20 wt%. It can be understood that the electron transport sub-layer of the present invention may further include a second metal oxide, and the second metal oxide is mixed in the electron transport sub-layer in a doped form. For example, when the doping ratio of the second metal oxide in the electron transport sub-layer is 10 wt%, it means that the weight of the second metal oxide accounts for 10% of the total weight of the electron transport sub-layer.

[0032] Preferably, the doping ratio of the second metal oxide in the electron transport sub-layer is 20 wt% - 30 wt%.

[0033] In a specific embodiment, the light-emitting layer is a quantum dot light-emitting layer.

[0034] In a specific embodiment, the electron mobility of the first metal oxide is selected from any one of 1×10 -2 cm 2 / (V·s), 1×10 -3 cm 2 / (V·s), 1×10 -4 cm 2 / (V·s), 1×10 -5 cm 2 / (V·s), and the electron mobility of the second metal oxide is selected from another one of the optional electron mobilities of the above first metal oxide. It can be understood that the electron mobility of the first metal oxide is not equal to that of the second metal oxide. The electron transport layer (electron transport sub-layer or transport functional layer) containing the metal oxide with a relatively small electron mobility can play a role in reducing the overall electron transport efficiency of the electron transport layer, thereby alleviating the charge accumulation problem at the interface and improving the efficiency of the device.

[0035] Preferably, the electron mobility of the second metal oxide is less than that of the first metal oxide. It can be understood that when the electron mobility of the second metal oxide is less than that of the first metal oxide, the electron mobility of the transport functional layer containing the second metal oxide is smaller than that of the electron transport sub-layer containing the first metal oxide (or doped with a certain amount of the second metal oxide), so that the transport functional layer can reduce the electron transport rate from the cathode to the light-emitting layer, maintain the balance between the electron injection and transport ability and the hole injection and transport ability, avoid excessive electron injection resulting in charge accumulation, and improve the light-emitting efficiency and properties of the device.

[0036] In a specific embodiment, the thickness of the electron transport sub-layer is greater than or equal to the thickness of the transport functional layer.

[0037] Preferably, the thickness of the electron transport sub-layer is greater than the thickness of the transport functional layer. The advantage of this setting is to ensure the balance between the number of electron injections and the number of holes, and further alleviate the charge accumulation problem at the interface.

[0038] In a specific embodiment, the thickness of the electron transport sub-layer is 10 nm - 100 nm, such as: 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, and typical examples are 50 nm, 60 nm. The thickness of the transport functional layer is 0 nm - 50 nm, such as: 0 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, and typical examples are 0 nm, 10 nm.

[0039] It should be noted that when the thickness of the transport functional layer is 0 nm, it means that there may be a situation where the transport functional layer is not included in the electron transport layer. However, it can be understood that the situation of not including the transport functional layer needs to meet the condition that the electron transport sub-layer also includes the second metal oxide. The electron transport layer includes the first metal oxide and the second metal oxide, and the second metal oxide is mixed in the electron transport sub-layer in a doped form, as Figure 3 shown, the electron transport layer 2 only includes the electron transport sub-layer 21. In addition, in the present invention, the "thickness" refers to the average thickness of the electron transport sub-layer / transport functional layer.

[0040] Preferably, the thickness of the electron transport sub-layer is 50 nm - 60 nm, and the thickness of the transport functional layer is 0 nm - 20 nm.

[0041] In a specific embodiment, the first metal oxide is selected from at least one of zinc oxide, magnesium zinc oxide, and aluminum zinc oxide. The average particle size of the first metal oxide is 3 nm - 10 nm, for example: 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, and a typical example is 5 nm.

[0042] Preferably, the first metal oxide is zinc oxide, and the average particle size of the first metal oxide is 3 nm - 5 nm.

[0043] In a specific embodiment, the second metal oxide is niobium pentoxide, and the average particle size of the second metal oxide is 10 nm - 30 nm, for example: 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, and a typical example is 15 nm.

[0044] Preferably, the average particle size of the second metal oxide is 10 nm - 15 nm.

[0045] In a specific embodiment, as Figure 4 shown, the light-emitting device further includes: a hole transport layer 4, a hole injection layer 5, and an anode 6. Specifically, as Figure 4 shown in FIG. a), the cathode 1, the electron transport sub-layer 21, the transport function layer 22, the light-emitting layer 3, the hole transport layer 4, the hole injection layer 5, and the anode 6 are sequentially stacked; as Figure 4 shown in FIG. b), the cathode 1, the transport function layer 22, the electron transport sub-layer 21, the light-emitting layer 3, the hole transport layer 4, the hole injection layer 5, and the anode 6 are sequentially stacked.

[0046] In the present invention, the light-emitting device can be a normal light-emitting device, as Figure 4 shown; or it can be an inverted light-emitting device, as Figure 5 shown. It should be noted that the layer structures of the inverted light-emitting device are the same as those of the device being a normal light-emitting device, and the stacking order of the electron transport sub-layer and the transport function layer relative to the light-emitting layer can be interchanged, and reference can be made to Figure 5 FIG. a) and FIG. b) therein.

[0047] According to a possible embodiment:

[0048] The electron transport layer includes an electron transport sub-layer and a transport function layer that are sequentially stacked, where specifically, it is as follows:

[0049] 1 - Electron transport sub-layer (for example, with a thickness of 50 nm):

[0050] The first metal oxide: zinc oxide;

[0051] The second metal oxide: niobium pentoxide (mixed in the electron transport sub-layer in a doped form, for example, the doping ratio is 20 wt%);

[0052] 2 - Transport functional layer, with a thickness of 0 nm, excluding the second metal oxide.

[0053] According to another possible embodiment:

[0054] The electron transport layer includes an electron transport sub-layer and a transport functional layer stacked in sequence, where specifically, it is as follows:

[0055] 1 - Electron transport sub-layer (for example, with a thickness of 50 nm):

[0056] The first metal oxide: zinc oxide;

[0057] The second metal oxide: niobium pentoxide (mixed in the electron transport sub-layer in a doped form, for example, the doping ratio is 20 wt%);

[0058] 2 - Transport functional layer (for example, with a thickness of 10 nm):

[0059] The second metal oxide: niobium pentoxide.

[0060] The present invention also provides a method for preparing a light-emitting device, and the specific steps are as follows:

[0061] Before preparing the light-emitting device, first mix niobium pentoxide nanoparticles or nanorods into an electron transport (ETL) material (inorganic nanoparticles, ZnO) to obtain an electron transport sub-layer material. After stirring and mixing evenly to obtain a stable liquid, and at the same time prepare a transport functional layer material containing niobium pentoxide nanoparticles or nanorods, then start the device preparation;

[0062] Preparation of a normal device: Select a substrate; form an anode on the substrate; form a hole injection layer on the anode by wet film formation; form a hole transport layer on the hole injection layer by wet film formation; form a quantum dot light-emitting layer on the hole transport layer by wet film formation; form an electron transport layer on the quantum dot light-emitting layer (first use the wet film formation method to form the electron transport sub-layer, and then use the wet film formation method to form the transport functional layer, or first use the wet film formation method to form the transport functional layer, and then use the wet film formation method to form the sub-transport sub-layer); form a cathode on the electron transport layer by evaporation; encapsulate to obtain a normal light-emitting device;

[0063] Inverted device preparation: Select a substrate; form a cathode on the substrate; form an electron transport layer (electron transport sub-layer / transport functional layer, or transport functional layer / electron transport sub-layer) on the cathode by wet film formation; form a quantum dot light-emitting layer on the electron transport layer by wet film formation; form a hole transport layer on the quantum dot light-emitting layer by evaporation; form a hole injection layer on the hole transport layer by evaporation; form an anode on the hole injection layer by evaporation; and encapsulate to obtain an inverted light-emitting device.

[0064] In the second case, when the electron transport sub-layer simultaneously includes a first metal oxide and a second metal oxide and the thickness of the transport functional layer included in the electron transport layer is 0 nm:

[0065] Normal device preparation: Select a substrate; form an anode on the substrate; form a hole injection layer on the anode by wet film formation; form a hole transport layer on the hole injection layer by wet film formation; form a quantum dot light-emitting layer on the hole transport layer by wet film formation; form an electron transport layer (electron transport sub-layer) on the quantum dot light-emitting layer by wet film formation; form a cathode on the electron transport layer by evaporation; and encapsulate to obtain a normal light-emitting device.

[0066] Inverted device preparation: Select a substrate; form a cathode on the substrate; form an electron transport layer (electron transport sub-layer) on the cathode by wet film formation; form a quantum dot light-emitting layer on the electron transport layer by wet film formation; form a hole transport layer on the quantum dot light-emitting layer by evaporation; form a hole injection layer on the hole transport layer by evaporation; form an anode on the hole injection layer by evaporation; and encapsulate to obtain an inverted light-emitting device.

[0067] In the present invention, the wet film formation method and the evaporation method have their conventional meanings in the art. The specific operation methods are as follows: Wet film formation: Spin coating / or inkjet printing can be used for film formation; during evaporation, the substrate is transferred to a vacuum chamber and electrode evaporation film formation is started.

[0068] The second aspect of the present invention provides a display device, and the display device includes the light-emitting device described in the first aspect of the present invention.

[0069] The present invention will be described in detail below through embodiments. The embodiments described in the present invention are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0070] Example 1

[0071] (1) Preparation of electron transport layer material

[0072] 1. Preparation of electron transport sub-layer material: An alcohol solution containing zinc oxide and an alcohol solution containing niobium pentoxide are mixed in a certain proportion. The average particle size of zinc oxide is 5 nm, and the average particle size of niobium pentoxide is 15 nm, obtaining an alcohol solution containing zinc oxide / niobium pentoxide nanomaterial. Among them, the doping ratio of niobium pentoxide is 20 wt%.

[0073] 2. Preparation of transport functional layer material: Prepare an alcohol solution containing niobium pentoxide, with an average particle size of niobium pentoxide being 15 nm, and mix evenly to obtain an alcohol solution containing niobium pentoxide nanomaterial.

[0074] (2) Preparation of top-emitting light-emitting device

[0075] Step 1: Cleaning of ITO anode conductive glass: Ultrasonic clean with deionized water, acetone, and isopropyl alcohol for 10 min respectively, dry with nitrogen and place in a petri dish, and reserve after ozone treatment for 20 minutes.

[0076] Step 2: Preparation of hole injection layer: Take 100 μL of the prepared HIL and dissolve it in ethyl benzoate solution, spin-coat it on the anode provided in Step 1 at 3000 rpm for 30 s, and then anneal it under a 230 °C hot plate for 30 min to obtain the hole injection layer.

[0077] Step 3: Preparation of hole transport layer: Take 100 μL of the prepared HTL and dissolve it in chlorobenzene solution, spin-coat it on the hole injection layer prepared in Step 2 at 3000 rpm for 30 s, and then anneal it under a 230 °C hot plate for 30 min to obtain the hole transport layer.

[0078] Step 4: Preparation of quantum dot light-emitting layer: Take 50 μL of the prepared HTL and dissolve it in n-octane solution, spin-coat it on the hole transport layer prepared in Step 3 at 3000 rpm for 30 s, and then anneal it under a 100 °C hot plate for 5 min to obtain the quantum dot light-emitting layer.

[0079] Step 5: Preparation of electron transport layer: Take the mixed alcohol solution containing zinc oxide / niobium pentoxide nanomaterial, spin-coat it on the quantum dot light-emitting layer prepared in Step 4 at 3000 rpm for 30 s to form an electron transport sub-layer, such that the thickness of the prepared electron transport sub-layer is 60 nm; further, take the mixed alcohol solution containing niobium pentoxide nanomaterial, spin-coat it on the electron transport sub-layer at 3000 rpm for 30 s to form a transport functional layer, such that the thickness of the prepared transport functional layer is 10 nm, and then anneal it under a 100 °C hot plate for 5 min to obtain the electron transport layer.

[0080] Step 6: Preparation of cathode: Evaporate an aluminum Al electrode on the electron transport layer prepared in Step 5, at 4×10 -4Evaporate at a pressure of 100 Pa to a thickness of 100 nm to obtain a cathode aluminum electrode

[0081] Finally, encapsulate to obtain a forward-emitting device.

[0082] Example Group 2

[0083] Example Group 2 is carried out with reference to Example 1. The difference is that the doping ratio of Nb in the electron transport sublayer material is changed, as specifically shown in Table 1. 2 O 5 The specific doping ratio is shown in Table 1.

[0084] Example Group 3

[0085] Example Group 3 is carried out with reference to Example 1. The difference is that the thicknesses of the electron transport sublayer and the transport functional layer are changed, as specifically shown in Table 1.

[0086] Example Group 4

[0087] Example Group 4 is carried out with reference to Example 1. The difference is that the specific type of the first metal oxide is changed, as specifically shown in Table 1.

[0088] Comparative Example 1

[0089] Comparative Example 1 is carried out with reference to Example 1. The difference is that the electron transport layer only includes the electron transport sublayer and does not include the transport functional layer, and the electron transport sublayer is not doped with the second metal oxide.

[0090] Comparative Example 2

[0091] Comparative Example 2 is carried out with reference to Example 1. The difference is that the electron transport layer of the light-emitting device does not include any electron transport layer material and only includes the transport functional layer, and the metal oxide in the transport functional layer is Nb 2 O 5 nanoparticles or nanorods.

[0092] Table 1

[0093]

[0094]

[0095] Perform external quantum efficiency (EQE) performance tests on the light-emitting devices of the examples and comparative examples. The specific test results are shown in Table 2

[0096] Table 2

[0097]

[0098]

[0099] As can be seen from Table 2, in the examples, introducing niobium pentoxide, the second metal oxide, into the electron transport layer can reduce the electron transport efficiency of the electron transport layer, alleviate the charge accumulation at the interface between the electron transport layer and the quantum dot light-emitting layer, avoid exciton quenching in the quantum dot light-emitting layer, thereby improving the efficiency of the light-emitting device, which is far superior to Comparative Example 1. Moreover, the electron transport layer does not include an electron transport layer material for electron transport, nor does it include an electron transport sublayer, but only includes a transport functional layer containing a second metal oxide. The electron transport rate will be greatly affected, and the efficiency of the light-emitting device will rapidly decline, as seen in Comparative Example 2.

[0100] In the second group of examples, by changing the doping ratio of the second metal oxide in the electron transport sublayer, it can be proved that the doping amount of the second metal oxide in the electron transport sublayer will also affect the efficiency of the light-emitting device. If the doping ratio of the second metal oxide is relatively high, such as in Example 2d, the electron mobility of the metal oxide in the electron transport sublayer will be too low, resulting in the electron mobility being less than the hole mobility, thus reducing the light-emitting efficiency. If the doping ratio of the second metal oxide is relatively low or not doped, such as in Example 2f or 2g, then the electron mobility of the metal oxide in the electron transport sublayer is still relatively high. Therefore, there will still be partial charge accumulation and exciton quenching phenomena. So, it is necessary to reasonably adjust the doping ratio of the second metal oxide in the electron transport sublayer to obtain better light-emitting device efficiency.

[0101] In the third group of examples, by changing the thicknesses of the electron transport sublayer and the transport functional layer, it can be proved that appropriate thicknesses of the electron transport sublayer and the transport functional layer will directly affect the efficiency of the light-emitting device. Reasonably adjusting the above parameters can further improve the device efficiency, such as in Example 1 and the third group of examples. In addition, as seen in Example 3g, when the thickness of the transport functional layer is 0 nm, that is, the electron transport layer does not include a transport functional layer, but due to doping an appropriate proportion of the second metal oxide in the electron transport sublayer, it can also play a role in reducing the electron transport efficiency of the electron transport layer and alleviating the charge accumulation at the interface between the electron transport layer and the quantum dot light-emitting layer, thereby improving the efficiency of the light-emitting device.

[0102] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A light-emitting device, characterized in that, it comprises: a cathode, an electron transport layer, and a light-emitting layer which are stacked, the electron transport layer includes a transport functional layer, and the transport functional layer is used to reduce the electron transport rate from the cathode to the light-emitting layer.

2. The light-emitting device according to claim 1, wherein, the electron transport layer further includes an electron transport sub-layer stacked with the transport functional layer, the electron transport sub-layer at least includes a first metal oxide, the transport functional layer at least includes a second metal oxide, and the electron mobilities of the first metal oxide and the second metal oxide are not equal.

3. The light-emitting device according to claim 2, wherein, the electron transport sub-layer, the transport functional layer, and the light-emitting layer are stacked in sequence, or the transport functional layer, the electron transport sub-layer, and the light-emitting layer are stacked in sequence.

4. The light-emitting device according to claim 2 or 3, wherein, the electron transport sub-layer further includes the second metal oxide; Preferably, the doping ratio of the second metal oxide in the electron transport sub-layer is 0.01 wt% - 50 wt%.

5. The light-emitting device according to claim 1, wherein, the light-emitting layer is a quantum dot light-emitting layer.

6. The light-emitting device according to claim 2, wherein, The electron mobility of the first metal oxide is selected from any one of 1×10 -2 cm 2 / (V·s), 1×10 -3 cm 2 / (V·s), 1×10 -4 cm 2 / (V·s), 1×10 -5 cm 2 / (V·s), and the electron mobility of the second metal oxide is selected from the other one; Preferably, the electron mobility of the second metal oxide is less than that of the first metal oxide.

7. The light-emitting device according to claim 4, wherein, the thickness of the electron transport sub-layer is greater than or equal to the thickness of the transport functional layer. Preferably, the thickness of the electron transport sub-layer is 10 nm - 100 nm, and the thickness of the transport functional layer is 0 nm - 50 nm.

8. The light-emitting device according to claim 2, wherein, the first metal oxide is selected from at least one of zinc oxide, magnesium zinc oxide, and aluminum zinc oxide; and / or, the second metal oxide includes niobium pentoxide.

9. The light-emitting device according to claim 2, wherein, it further comprises: a hole transport layer, a hole injection layer, and an anode; the cathode, the electron transport sub-layer, the transport functional layer, the light-emitting layer, the hole transport layer, the hole injection layer, and the anode are stacked in sequence. Preferably, the cathode, the transport functional layer, the electron transport sub-layer, the light-emitting layer, the hole transport layer, the hole injection layer, and the anode are stacked in sequence.

10. A display device, characterized in that, the display device includes the light-emitting device according to any one of claims 1 - 9.

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