Light emitting device and display substrate

Abstract

The application discloses a light-emitting device and a display substrate, and belongs to the technical field of display. The light-emitting device comprises a first electrode, a first crystalline layer, a light-emitting layer and a second electrode which are arranged in layers. The first crystalline layer is arranged between the first electrode and the light-emitting layer. Since the first crystalline layer is a crystalline film, the first crystalline layer has regular molecular arrangement, low impurity content and good stability, can form a stable carrier transport channel, and thus can improve the carrier mobility of the light-emitting device. Moreover, the light-emitting material formed on the first crystalline layer is in a nano-aggregate state. In the light-emitting process, the holes provided by the first electrode and the electrons provided by the second electrode have high mobility when moving to the nano-aggregate, and thus a higher current density can be realized, and thus the brightness of the light-emitting device can be improved.

Description

Technical Field

[0001] This application relates to the field of display technology, and in particular to a light-emitting device and a display substrate. Background Technology

[0002] Organic light-emitting diodes (OLEDs) have many advantages, such as active light emission, high brightness, high contrast, ultra-thinness, low power consumption, flexibility, and wide operating temperature range. Therefore, OLEDs have been widely used in the field of display technology.

[0003] The light-emitting layer in OLEDs is an organic semiconductor thin film. Although organic semiconductor materials can form orbitals, allowing electrons to move freely, the van der Waals forces between molecules are much weaker than covalent bonds, resulting in independent energy levels for each molecule and preventing the formation of a continuous band structure. Especially for amorphous organic semiconductor thin films, charge carriers typically transport in a hopping manner, leading to low mobility for holes and electrons.

[0004] Therefore, OLED light-emitting devices that use the aforementioned amorphous organic semiconductor thin film as the light-emitting layer have low carrier mobility, resulting in low current and thus low maximum brightness. Summary of the Invention

[0005] This application provides a light-emitting device and a display substrate. The technical solution is as follows:

[0006] According to one aspect of this application, a light-emitting device is provided, the light-emitting device comprising: a first electrode, a first crystalline layer, a light-emitting layer, and a second electrode stacked thereon;

[0007] The light-emitting layer includes: multiple sub-light-emitting layers stacked together; each sub-light-emitting layer includes: a plurality of nano-aggregates, and a functional layer covering the plurality of nano-aggregates; in the same sub-light-emitting layer, the functional layer is in contact with the outer surface of the plurality of nano-aggregates away from the first crystalline layer;

[0008] Specifically, for the sub-light-emitting layer closest to the first crystalline layer, a plurality of nano-aggregates in the sub-light-emitting layer are in contact with the surface of the first crystalline layer away from the first electrode, and are dispersed on the surface of the first crystalline layer away from the first electrode; for two adjacent sub-light-emitting layers, a plurality of nano-aggregates in the sub-light-emitting layer further away from the first electrode are in contact with the functional layer in the sub-light-emitting layer closer to the first electrode.

[0009] Optionally, the multilayer sub-emitting layer includes: at least one first sub-emitting layer and one second sub-emitting layer; the at least one first sub-emitting layer is located between the second sub-emitting layer and the first crystalline layer;

[0010] The functional layer in the first sub-light-emitting layer is a second crystalline layer.

[0011] Optionally, the nano-aggregates in the first sub-light-emitting layer include: a first blocking portion, a light-emitting portion, and a second blocking portion stacked in the direction from the first electrode to the second electrode;

[0012] The triplet energy levels of the first blocking part and the second blocking part are both higher than the triplet energy level of the light-emitting part.

[0013] Optionally, the first blocking portion is reused as an electron blocking layer, and the second blocking portion is reused as a hole blocking layer.

[0014] Optionally, the material of the light-emitting part includes: a P-type main material and an N-type main material;

[0015] The material of the first blocking part includes the P-type main body material, and the material of the second blocking part includes the N-type main body material.

[0016] Optionally, the surface of the first blocking portion near the first crystalline layer is a plane, and the surface of the first blocking portion away from the first crystalline layer is a first curved surface protruding toward the second electrode;

[0017] The light-emitting part covers the surface of the first blocking part away from the first crystalline layer, and the surface of the light-emitting part away from the first blocking part is a second curved surface that protrudes toward the second electrode;

[0018] The second blocking portion covers the surface of the light-emitting portion opposite to the first blocking portion, and the surface of the second blocking portion opposite to the light-emitting portion is a third curved surface protruding toward the second electrode.

[0019] Optionally, the functional layer in the second sub-light-emitting layer is a second crystalline layer, and the nano-aggregate in the second sub-light-emitting layer includes: a first blocking portion, a light-emitting portion, and a second blocking portion stacked in the direction from the first electrode to the second electrode;

[0020] The triplet energy levels of the first blocking part and the second blocking part are both higher than the triplet energy level of the light-emitting part.

[0021] Optionally, the functional layer in the second sub-light-emitting layer is a barrier layer that covers the entire layer, and the nano-aggregate in the second sub-light-emitting layer includes: a first barrier portion and a light-emitting portion stacked in the direction from the first electrode to the second electrode;

[0022] The triplet energy levels of the first blocking portion and the blocking layer are both higher than the triplet energy level of the light-emitting portion.

[0023] Optionally, the light-emitting device further includes: a planarization layer, the planarization layer being located between the first electrode and the first crystalline layer;

[0024] The roughness of the surface of the planarization layer facing away from the first electrode is less than the roughness of the surface of the first electrode facing the second electrode, and the planarization layer is reused as a hole injection layer.

[0025] Optionally, the first crystalline layer includes an induction layer and an epitaxial layer stacked along a direction away from the first electrode;

[0026] In this embodiment, at least one of the sub-light-emitting layers has a functional layer that is a second crystalline layer, and the material of the epitaxial layer is the same as that of the second crystalline layer.

[0027] Optionally, the epitaxial layer is multiplexed as a hole transport layer.

[0028] Optionally, the total thickness of the nano-aggregates in each of the sub-light-emitting layers ranges from 20 nanometers to 40 nanometers.

[0029] Optionally, in one of the sub-luminescent layers, the ratio of the total area of ​​the orthogonal projection of the plurality of nano-aggregates onto the first crystalline layer to the total area of ​​the first crystalline layer is in the range of 20% to 30%.

[0030] Optionally, the thickness of the nanoaggregate in the direction perpendicular to the first electrode ranges from 4 nanometers to 6 nanometers;

[0031] The diameter of the orthogonal projection of the nanoaggregate onto the first electrode ranges from 50 nanometers to 70 nanometers.

[0032] On the other hand, a display substrate is provided, including: a driving backplate, and a plurality of light-emitting devices arranged in an array on one side of the driving backplate, wherein the light-emitting devices are any of the aforementioned light-emitting devices.

[0033] The beneficial effects of the technical solutions provided in this application include at least the following:

[0034] This application provides a light-emitting device in which a first crystalline layer is disposed between a first electrode and a light-emitting layer. Since the first crystalline layer is a crystalline thin film, it has a regular molecular arrangement, low impurity content, and good stability, which can form a stable carrier transport channel, thereby improving the carrier mobility of the light-emitting device. Furthermore, the light-emitting material formed on the first crystalline layer exhibits a nano-aggregate state. During light emission, the holes provided by the first electrode and the electrons provided by the second electrode move to the nano-aggregates with high mobility, achieving a higher current density and thus improving the brightness of the light-emitting device. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of a structure provided in an embodiment of this application;

[0037] Figure 2 This is a comparison chart of voltage-brightness curves of a light-emitting device provided in the embodiments of this application and several light-emitting devices provided in related technologies;

[0038] Figure 3 This is a schematic diagram of another light-emitting device provided in an embodiment of this application;

[0039] Figure 4 This application provides a schematic diagram of the structure and energy levels of a first sub-emissive layer.

[0040] Figure 5 This is a schematic diagram of the structure and energy level of another sub-emissive layer provided in this application;

[0041] Figure 6 This is a schematic diagram of another light-emitting device provided in an embodiment of this application;

[0042] Figure 7 This is a schematic diagram of another light-emitting device provided in an embodiment of this application;

[0043] Figure 8 This is a schematic diagram of forming a planarization layer provided in an embodiment of this application;

[0044] Figure 9 This is a schematic diagram of an embodiment of the present application for forming an induction layer;

[0045] Figure 10 yes Figure 9 A schematic diagram of the morphology of the induced layer is provided;

[0046] Figure 11 This is a schematic diagram of forming an epitaxial layer according to an embodiment of this application;

[0047] Figure 12 yes Figure 11 Provided morphological diagram of the epitaxial layer;

[0048] Figure 13 This is a schematic diagram of the formation of nano-aggregates provided in an embodiment of this application;

[0049] Figure 14 yes Figure 13 Provided morphological diagram of the epitaxial layer;

[0050] Figure 15 This is a schematic diagram of the formation of a second crystalline layer provided in an embodiment of this application;

[0051] Figure 16 This is a schematic diagram of forming a light-emitting layer according to an embodiment of this application;

[0052] Figure 17 This is a schematic diagram of an embodiment of the present application providing a method for forming an electron transport layer, an electron injection layer, and a second electrode.

[0053] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0055] Currently, OLEDs are widely used in optoelectronic devices such as televisions, displays, mobile phones, and watches. However, OLEDs still face significant challenges in terms of electroluminescence performance, such as brightness, especially the commercialization of blue OLEDs, which is limited by lower brightness and shorter lifespan. The light-emitting layer in OLEDs is an organic semiconductor thin film. Although organic semiconductor materials can form orbitals, allowing electrons to move freely, the van der Waals forces between molecules are much weaker than covalent bonds. This results in each molecule's energy level being independent, making it impossible to form a continuous band structure. This localizes the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of organic semiconductor materials, requiring electrons to overcome a certain potential barrier when entering adjacent molecular energy levels.

[0056] In related technologies, the organic semiconductor thin film in OLEDs is an amorphous film, and charge carriers typically transport themselves in a hopping manner, resulting in low mobility for holes and electrons, generally ranging from 1E-4 cm² V⁻¹s⁻¹ to 1E-5 cm² V⁻¹s⁻¹. This low mobility leads to lower current density in OLEDs, resulting in lower maximum brightness. This is especially true for blue OLEDs; due to the inherent limitations of the current, the maximum brightness of blue OLEDs cannot meet current high-brightness requirements, making them unsuitable for outdoor applications and other scenarios requiring high-brightness displays.

[0057] This application provides a light-emitting device; please refer to the embodiments provided. Figure 1 , Figure 1 This is a schematic diagram of a structure provided in an embodiment of this application. The light-emitting device 10 includes: a first electrode 100, a first crystalline layer 200, a light-emitting layer 300, and a second electrode 400 stacked together.

[0058] One of the first electrode 100 and the second electrode 400 is an anode, and the other is a cathode. In some possible implementations, the first electrode 100 can be an anode and can be used to provide holes, while the second electrode 400 can be a cathode and can be used to provide electrons.

[0059] The first crystalline layer 200 is a crystalline thin film. For example, the material of the first crystalline layer 200 may include an organic crystal material. The organic crystal material has a regular molecular arrangement, low impurity content, good stability and high carrier mobility, and can provide sufficient current to support the light-emitting device 000 to achieve higher brightness.

[0060] The light-emitting layer 300 includes: a multilayered sub-light-emitting layer 310 stacked together, wherein the sub-light-emitting layer 310 includes: a plurality of nano-aggregates 311, and a functional layer 312 covering the plurality of nano-aggregates 311. Here, the nano-aggregates 311 can be aggregate structures with sizes in the nanoscale range, and the material of the nano-aggregates 311 includes a light-emitting material. The nano-aggregates 311 can be driven to emit light in cooperation with the first electrode 100 and the second electrode 400. Thus, under the action of the electric field between the first electrode 100 and the second electrode 400, the first electrode 100 generates holes, and the second electrode 400 generates electrons. When the holes provided by the first electrode 100 and the electrons provided by the second electrode 400 are transported to the nano-aggregates 311 in the light-emitting layer 300, the holes and electrons combine to generate excitons. The excitons can excite the light-emitting layer 300 to generate photons, thereby realizing the light-emitting function.

[0061] Within the same sub-light-emitting layer 310, the functional layer 312 is in contact with the outer surface of multiple nano-aggregates 311 facing away from the first crystalline layer 200. Here, the functional layer 312 can serve as a medium for carrier migration and has a certain regulatory effect on carrier migration. In one possible implementation, the functional layer 312 can be a crystalline thin film, in which case the functional layer 312 can be used to enhance the carrier migration rate. In another possible implementation, the functional layer 312 can also be an amorphous thin film; for example, the functional layer 312 can also be an n-type semiconductor thin film, in which case the functional layer 312 can allow electron migration and block hole migration.

[0062] Among them, for the sub-light-emitting layer 310 closest to the first crystalline layer, multiple nano-aggregates 311 in the sub-light-emitting layer 310 are in contact with the surface of the first crystalline layer 200 on the side away from the first electrode 100, and are dispersedly disposed on the surface of the first crystalline layer 200 on the side away from the first electrode 100. Here, as... Figure 1 As shown, the sub-light-emitting layer 310 closest to the first crystalline layer can be the lowermost sub-light-emitting layer 310 among the multiple sub-light-emitting layers 310. Therefore, multiple nano-aggregates 311 in the sub-light-emitting layer 310 are formed on the surface of the first crystalline layer 200 away from the first electrode 100. In this way, holes transmitted through the first crystalline layer 200 can be directly transmitted to the nano-aggregates 311.

[0063] For two adjacent sub-light-emitting layers 310, the multiple nano-aggregates 311 in the sub-light-emitting layer 310 further away from the first electrode 100 come into contact with the functional layer 312 in the sub-light-emitting layer 310 closer to the first electrode 100. Here, since the functional layer 312 can be a medium for carrier migration and has a certain regulatory effect on carrier migration, carriers can also be transported to the nano-aggregates 311 through the functional layer 312.

[0064] Therefore, during the light emission process of the light-emitting device 000, based on the regulation of carrier mobility by the first crystalline layer 200 and the functional layer 312, the mobility of holes provided by the first electrode 100 and electrons provided by the second electrode 400 to the nano-aggregates 311 can be higher, thereby achieving a higher current density and thus improving the brightness of the light-emitting device 000.

[0065] Please refer to Figure 2 , Figure 2 This is a comparison chart of the voltage-brightness curves of a light-emitting device provided in the embodiments of this application and several light-emitting devices provided in related technologies. Figure 2 The horizontal axis represents voltage in volts, and the vertical axis represents luminance in nits. O1 is a triplet-triplet annihilation device, O2 is a phosphorescent device, and O3 is a thermally excited delayed fluorescence device. O1, O2, and O3 are all amorphous OLED devices. Figure 2 It can be seen that the brightness achievable by amorphous OLED devices is much lower than that achievable by crystalline OLED devices. Therefore, the light-emitting device 000 provided in this application embodiment can achieve higher brightness and has a wider range of applications.

[0066] In summary, this application provides a light-emitting device in which a first crystalline layer is disposed between the first electrode and the light-emitting layer. Since the first crystalline layer is a crystalline thin film, it possesses a regular molecular arrangement, low impurity content, and good stability, enabling the formation of stable carrier transport channels and thereby improving the carrier mobility of the light-emitting device. Furthermore, the light-emitting material formed on the first crystalline layer exhibits a nano-aggregate state. During light emission, the high mobility of holes provided by the first electrode and electrons provided by the second electrode to the nano-aggregates allows for higher current density, thereby enhancing the brightness of the light-emitting device.

[0067] Optionally, the material of the nano-aggregate 311 includes: a host luminescent material and a guest luminescent material doped into the host luminescent material, wherein the guest luminescent material can be a phosphorescent material. When holes and electrons combine to form excitons, paired singlet excitons and unpaired triplet excitons are generated in a 1:3 ratio according to the spin configuration. For phosphorescent materials, both triplet and singlet excitons participate in luminescence, while for fluorescent materials, only singlet excitons participate in luminescence. Therefore, the embodiments of this application combine crystalline thin films and highly efficient phosphorescent materials, thereby increasing the current density while enhancing the probability of electron-hole pair formation and the effective radiative transition efficiency, enabling the light-emitting device 000 to achieve high brightness and low voltage under high current.

[0068] In this application, the nanoaggregates 311 are nanoscale in size. To achieve a certain effective luminescence thickness, multiple sub-luminescence layers 310 can be formed to stack the luminescence thickness. For some possible implementations, please refer to... Figure 3 , Figure 3 This is a schematic diagram of another light-emitting device provided in an embodiment of this application. The multilayer sub-light-emitting layer 310 includes at least one first sub-light-emitting layer 310a and one second sub-light-emitting layer 310b. The at least one first sub-light-emitting layer 310a is located between the second sub-light-emitting layer 310b and the first crystalline layer 200. That is, the second sub-light-emitting layer 310b is the sub-light-emitting layer 310 closest to the second electrode 400 in the multilayer sub-light-emitting layer 310. For example, with... Figure 3 Taking the light-emitting device shown as an example, the second sub-light-emitting layer 310b is the uppermost sub-light-emitting layer 310.

[0069] The structure of the first sub-light-emitting layer 310a is described below:

[0070] The functional layer 312 in the first sub-light-emitting layer 310a is the second crystalline layer 500. Here, the second crystalline layer 500 is a crystalline thin film. For example, the material of the first crystalline layer 200 may include an organic crystal material. Organic crystal materials have regular molecular arrangement, low impurity content, good stability, and high carrier mobility. Therefore, by combining the first crystalline layer 200 and the second crystalline layer 500, the mobility of electrons and holes can be effectively improved, thereby providing sufficient current to support the light-emitting device 000 to achieve higher brightness.

[0071] In this application, for the first sub-emitting layer 310a in the blue light-emitting device, please refer to... Figure 4 , Figure 4 This application provides a schematic diagram of the structure and energy levels of a first sub-luminescent layer 310a. In the first sub-luminescent layer 310a, nano-aggregates 311 are used for luminescence, and a second crystalline layer 500 surrounds the nano-aggregates 311. In some possible implementations, the nano-aggregates 311 include a blue phosphorescent material, and the triplet energy level T1 of the second crystalline layer 500 is lower than the triplet energy level T1 of the blue phosphorescent material. For example, the triplet energy level T1 of the second crystalline layer 500 is 2.4 eV, while the triplet energy level T1 of the blue phosphorescent material in the nano-aggregate 311 is 2.6 eV. Therefore, after exciton formation, a large amount of energy is poured from the triplet energy level T1 of the blue phosphorescent material in the nano-aggregate 311 to the triplet energy level T1 of the second crystalline layer 500, resulting in energy waste and reduced luminescence efficiency.

[0072] In addition, since the singlet energy level S1 of the second crystal layer 500 is higher than the singlet energy level S1 of the blue phosphorescent material, the energy of the singlet energy level S1 of the blue phosphorescent material will not leak out to the singlet energy level S1 of the second crystal layer 500.

[0073] To address the issue of energy leakage, please refer to... Figure 3 and Figure 5 , Figure 5 This is a schematic diagram of the structure and energy level of another sub-emissive layer provided in this application. The nano-aggregates 311 in the first sub-emissive layer 310a include a first blocking portion 311a, an emissive portion 311b, and a second blocking portion 311c stacked in the direction from the first electrode 100 to the second electrode 400. Here, the emissive portion 311b is the emissive center in the nano-aggregate 311. For example, for a blue light-emitting device, the material of the emissive portion 311b includes a blue phosphorescent material. The material of the emissive portion 311b also includes a host emissive material, and the blue phosphorescent material is a guest emissive material doped into the host emissive material.

[0074] The triplet energy levels of the first blocking part 311a and the second blocking part 311c are both higher than those of the light-emitting part 311b. For example, the triplet energy level T1 of the first blocking part 311a is 3.1 eV, the triplet energy level T1 of the second blocking part 311c is 3.2 eV, and the triplet energy level T1 of the blue phosphorescent material in the light-emitting part 311b is 2.6 eV. Therefore, the energy generated after exciton formation in the light-emitting part 311b is difficult to cross the first blocking part 311a and the second blocking part 311c, thus avoiding energy leakage and waste.

[0075] For example, the second blocking portion 311c can prevent the energy of the light-emitting portion 311b from leaking out to the second crystalline layer 500 in the same first sub-light-emitting layer 310. The first blocking portion 311a can prevent the energy from leaking out to the second crystalline layer 500 in an adjacent first sub-light-emitting layer 310, or, for the first blocking portion 311a in the first sub-light-emitting layer 310 closest to the first electrode 100, it can prevent the energy from leaking out to the first crystalline layer 200.

[0076] Optionally, the first blocking portion 311a is reused as an electron blocking layer, and the second blocking portion 311c is reused as a hole blocking layer. In this way, the first blocking portion 311a can prevent electrons from the second electrode 400 from continuing to move toward the first electrode 100, and the second blocking portion 311c can prevent holes from the first electrode 100 from continuing to move toward the second electrode 400. This confines holes and electrons at the light-emitting portion 311b for light emission, preventing carrier loss and thus improving light emission efficiency.

[0077] Optionally, the material of the light-emitting part 311b includes a P-type main material and an N-type main material. The material of the first blocking part 311a includes a P-type main material, and the material of the second blocking part 311c includes an N-type main material. Thus, both the first blocking part 311a and the light-emitting part 311b include the same P-type main material with equal band gaps, thereby reducing the barrier to hole transport. Similarly, both the second blocking part 311c and the light-emitting part 311b include the same N-type main material with equal band gaps, thereby reducing the barrier to electron transport.

[0078] Optionally, the surface of the first blocking portion 311a near the first crystalline layer 200 is a plane, and the surface of the first blocking portion 311a away from the first crystalline layer 200 is a first curved surface protruding toward the second electrode 400. For example, as shown... Figure 3 As shown, the shape of the first blocking part 311a can be approximately hemispherical, and the cross-section of the first blocking part 311a can be semi-circular. However, this application does not strictly require that the shape of the first blocking part 311a be a regular hemisphere.

[0079] The light-emitting portion 311b covers the surface of the first blocking portion 311a facing away from the first crystalline layer 200, and the surface of the light-emitting portion 311b facing away from the first blocking portion 311a is a second curved surface protruding towards the second electrode 400. For example, as shown... Figure 3 As shown, the shape of the light-emitting part 311b can be approximated as half of a hollow sphere, and the cross-section of the light-emitting part 311b can be a fan-shaped ring.

[0080] The second blocking portion 311c covers the surface of the light-emitting portion 311b facing away from the first blocking portion 311a, and the surface of the second blocking portion 311c facing away from the light-emitting portion 311b is a third curved surface protruding towards the second electrode 400. For example, as shown... Figure 3 As shown, the shape of the second blocking part 311c can be approximated as half of a hollow sphere, and the cross-section of the second blocking part 311c can be a fan-shaped ring.

[0081] Based on the above shape, the first blocking part 311a and the second blocking part 311c have a better covering effect on the light-emitting part 311b, thereby effectively blocking energy leakage and confining more electrons and holes at the light-emitting part 311b for light emission.

[0082] The structure of the second sub-light-emitting layer 310b is described below:

[0083] In one possible implementation, please refer to Figure 6 , Figure 6This is a schematic diagram of another light-emitting device provided in an embodiment of this application. The functional layer 312 in the second sub-light-emitting layer 310b is a second crystalline layer 500. The nano-aggregates 311 in the second sub-light-emitting layer 310b include a first blocking portion 311a, a light-emitting portion 311b, and a second blocking portion 311c stacked in the direction from the first electrode 100 to the second electrode 400. The triplet energy levels of the first blocking portion 311a and the second blocking portion 311c are both higher than the triplet energy level of the light-emitting portion 311b. In this case, the structure of the second sub-light-emitting layer 310b is consistent with the structure of the first sub-light-emitting layer 310a, thereby achieving the same effect, that is, effectively preventing energy leakage while improving carrier mobility, thus improving the light-emitting effect of the light-emitting device 000.

[0084] In another possible implementation, please refer to Figure 7 , Figure 7 This is a schematic diagram of another light-emitting device provided in an embodiment of this application. The functional layer 312 in the second sub-light-emitting layer 310b is a barrier layer 600 that covers the entire layer. The nano-aggregates 311 in the second sub-light-emitting layer 310b include a first barrier portion 311a and a light-emitting portion 311b stacked in the direction from the first electrode 100 to the second electrode 400.

[0085] In this design, the triplet energy levels of the first blocking portion 311a and the blocking layer 600 are both higher than the triplet energy levels of the light-emitting portion 311b. Thus, the blocking layer 600 can prevent energy leakage from the light-emitting portion 311b to the film layer above the second sub-light-emitting layer 310b, thereby achieving the effect of preventing energy leakage.

[0086] Optionally, the material of the blocking layer 600 can be the same as the material of the second blocking portion 311c, so the blocking layer 600 can also be reused as a hole blocking layer. In this way, the blocking layer 600 can prevent holes from the first electrode 100 from continuing to move toward the second electrode 400, thereby confining the holes at the light-emitting portion 311b for light emission, avoiding carrier loss, and thus improving the light emission efficiency.

[0087] Furthermore, the material of the blocking layer 600 can be the same as the material of the second blocking part 311c. That is, both the blocking layer 600 and the light-emitting part 311b include the same N-type host material with equal band gap, thereby reducing the barrier to electron transport.

[0088] In the embodiments of this application, please refer to Figure 6 and Figure 7The light-emitting device 000 further includes a planarization layer 700, which is located between the first electrode 100 and the first crystalline layer 200. The roughness of the surface of the planarization layer 700 facing away from the first electrode 100 is less than the roughness of the surface of the first electrode 100 facing the second electrode 400. The planarization layer 700 is used to improve flatness, preventing the first electrode 100 from being too rough and affecting the growth of the first crystalline layer 200, thereby improving the quality of the first crystalline layer 200.

[0089] Planarization layer 700 is reused as a hole injection layer. That is, planarization layer 700 can be made of a material with hole injection capability, thereby ensuring that holes can be transmitted through planarization layer 700, and thus ensuring that light-emitting device 000 can emit light effectively.

[0090] For example, the material of the first electrode 100 may include indium tin oxide (ITO), and if the surface roughness of indium tin oxide is about 0.8 nanometers, then the surface roughness of the planarization layer 700 is less than 0.8 nanometers. Alternatively, the material of the planarization layer 700 may include poly(3,4-ethylenedioxythiophene) / poly(p-phenylene sulfonate) composite material (PEDOT:PSS). Here, the surface roughness can be the root mean square roughness (RMS).

[0091] Optionally, the first crystalline layer 200 includes an induction layer 210 and an epitaxial layer 220 stacked along a direction opposite to the first electrode 100. In this embodiment, the first crystalline layer 200 can be fabricated using a weak-epitaxy-growth (WEG) method. Here, the induction layer 210 can be a layered organic small-molecule crystalline thin film (generally several molecular layers can be grown layer by layer) used to induce the growth of the epitaxial layer 220. Then, organic semiconductor molecules can be further grown on the induction layer 210 to form an organic crystalline thin film, ultimately forming the epitaxial layer 220.

[0092] For example, the material of the inducing layer 210 may include 2,5-bis(4-biphenyl)thiophene (BP1T), and the material of the epitaxial layer 220 may include 2-(4-(9H-carbazole-9-yl)-1-(3,5-difluorophenyl)-1H-phenanthimidazole (2FPPICz).

[0093] In this process, at least one sub-light-emitting layer 310 has a functional layer 312 that is a second crystalline layer 500, and the material of the epitaxial layer 220 is the same as that of the second crystalline layer 500. Thus, the second crystalline layer 500 continues to grow along the region on the epitaxial layer 320 where no nano-aggregates 311 have grown, until it reaches the same height as the nano-aggregates 311, filling the gaps between the nano-aggregates 311 and facilitating the growth of nano-aggregates for the next sub-light-emitting layer 310. This results in good continuity between the second crystalline layer 500 and the first crystalline layer 200.

[0094] Optionally, the epitaxial layer 220 can be reused as a hole transport layer, that is, the material of the epitaxial layer 220 can be a material with hole transport capability, thereby ensuring that holes can move toward the nano-aggregates via the epitaxial layer 220.

[0095] Optionally, in a sub-light-emitting layer 310, the ratio of the total area of ​​the orthogonal projection of multiple nano-aggregates 311 onto the first crystalline layer 200 to the total area of ​​the first crystalline layer 200 is in the range of 20% to 30%. This ensures that each sub-light-emitting layer 310 contains sufficient nano-aggregates 311 for light emission, thereby improving the light emission effect.

[0096] Optionally, the total thickness of the nano-aggregates 311 in each sub-light-emitting layer 310 ranges from 20 nm to 40 nm. The thickness of the nano-aggregates 311 in the direction perpendicular to the first electrode 100 ranges from 4 nm to 6 nm. Based on this, the number of sub-light-emitting layers 310 can range from 2 to 5 layers.

[0097] Among them, for the nano-aggregates 311 in the first sub-light-emitting layer 310a, the thickness range of the first blocking part 311a, the light-emitting part 311b and the second blocking part 311c can all be 0.5 nanometers to 2 nanometers.

[0098] Optionally, the diameter of the orthographic projection of the nanoaggregate 311 onto the first electrode 100 ranges from 50 nm to 70 nm. For example, in embodiments of this application, the size of the nanoaggregate 311 can be controlled by the nominal thickness. For instance, a nominal thickness of 0.5 nm corresponds to an actual thickness of 4 nm and a diameter of 50 nm for the nanoaggregate 311, and a nominal thickness of 1 nm corresponds to an actual thickness of 6 nm and a diameter of 70 nm for the nanoaggregate 311.

[0099] The following is based on Figure 6 Taking the light-emitting device 000 shown as an example, the manufacturing process for obtaining the light-emitting device 000 is described below:

[0100] 1. Obtain the first electrode 100.

[0101] The first electrode 100 can be disposed on the substrate. For example, to achieve the fabrication of a crystalline film and ensure weak epitaxial growth of the film, embodiments of this application can use an ITO / glass substrate, where the ITO thickness is 150 nanometers and its resistivity is 8 ohms per square meter (Ω / m). 2 )~10Ω / m 2 The surface roughness of ITO is approximately 0.8 nanometers.

[0102] In this embodiment, the substrate on which the first electrode 100 is disposed can also be cleaned and dried, and the surface of the first electrode 100 can be treated with ultraviolet light for 10 minutes to increase the wettability of the planarization layer 700.

[0103] 2. A planarization layer 700 is formed on the surface of the first electrode 100.

[0104] Please refer to Figure 8 , Figure 8 This is a schematic diagram illustrating the formation of a planarization layer according to an embodiment of this application. In this embodiment, the material of the planarization layer 700 can be spin-coated onto the surface of the first electrode 100 to form the planarization layer 700. The substrate with the spin-coated planarization layer 700 is then fed into a vacuum evaporation apparatus for heating to prepare an induction layer.

[0105] For example, the planarization layer 700 can be made of PEDOT:PSS, which may be filtered. The spin coating process can be performed at a speed of 4000 spins per minute (rpm). The substrate temperature range is 80°C to 110°C.

[0106] 3. An induction layer 210 is formed on the side of the planarization layer 700 opposite to the first electrode 100.

[0107] Please refer to Figure 9 , Figure 9 This is a schematic diagram of an induction layer provided in an embodiment of this application. The first crystalline layer 200 can be manufactured by a weak orientation epitaxial growth method. In this embodiment, an organic small molecule crystalline thin film that can be grown in layers needs to be introduced on an amorphous substrate (an ITO substrate with a planarization layer 700) as an induction layer 210.

[0108] The induced layer 210 can be formed by thermal evaporation (vapor deposition). For example, the cavity vacuum level during thermal evaporation is 3 × 10⁻⁶. -6 The Torr evaporation rate ranges from 0.1 nanometers per second (nm / s). For example, the material of the inducing layer 210 may include BP1T.

[0109] In this embodiment, the surface morphology of the induced layer 210 can be tested using atomic force microscopy (AFM). Please refer to [link / reference]. Figure 10, Figure 10 yes Figure 9 The provided schematic diagram of the morphology of the induced layer shows that, since the induced layer 210 has a layered growth structure, two molecular layers are grown in region Q1 and three molecular layers are grown in region Q2. For example, Figure 10 The surface roughness of the induced layer 210 shown is 4 nanometers.

[0110] It should be noted that, Figure 10 The white and black areas in the image are two areas with different heights, with the white area being taller than the black area.

[0111] 4. An epitaxial layer 220 is formed on the side of the induced layer 210 that is away from the planarization layer 700.

[0112] Please refer to Figure 11 , Figure 11 This is a schematic diagram of an epitaxial layer formation according to an embodiment of this application. Under constant process temperature, this embodiment of the application can form an epitaxial layer 220 on the side of the induced layer 210 opposite to the planarization layer 700 via a thermal evaporation process. For example, the material of the epitaxial layer 220 may include 2FPPICz.

[0113] In this embodiment, the surface morphology of the epitaxial layer 220 can be tested using an atomic force microscope. Please refer to [reference needed]. Figure 12 , Figure 12 yes Figure 11 A schematic diagram of the epitaxial layer is provided. Epitaxial layer 220 has a clear orientation, which indicates that epitaxial layer 220 is a crystalline film. It should be noted that... Figure 12 The white and black areas in the image are two areas with different heights, with the white area being taller than the black area.

[0114] 5. Multiple nano-aggregates 311 are formed on the side of the epitaxial layer 220 away from the induction layer 210.

[0115] Please refer to Figure 13 , Figure 13 This is a schematic diagram of the formation of nano-aggregates provided in an embodiment of this application. Under constant process temperature, this embodiment of the application can sequentially form a first blocking portion 311a, a light-emitting portion 311b, and a second blocking portion 311c through a thermal evaporation process, thereby forming multiple nano-aggregates 311. Here, due to the large surface energy difference between different regions of the epitaxial layer 220, amorphous materials can nucleate and grow on the crystal surface within a certain thickness to form nano-sized aggregates.

[0116] The surface morphology of the nanoaggregates 311 can be tested using an atomic force microscope in the embodiments of this application. Please refer to [link / reference]. Figure 14 , Figure 14yes Figure 13 The provided schematic diagram of the epitaxial layer shows that the multiple nano-aggregates 311 have an approximately circular structure when viewed from above, and the multiple nano-aggregates 311 are randomly and disorderly distributed.

[0117] 6. A second crystalline layer 500 is formed on the side of the multiple nano-aggregates 311 that is away from the epitaxial layer 220.

[0118] Please refer to Figure 15 , Figure 15 This is a schematic diagram of the formation of a second crystalline layer provided in an embodiment of this application. Under the condition that the process temperature remains unchanged, the second crystalline layer 500 can be formed by thermal evaporation process. The second crystalline layer 500 will continue to grow along the region on the epitaxial layer 320 where no nano-aggregates 311 have grown, until it is consistent with the height of the nano-aggregates 311, and fill the gaps between the nano-aggregates 311 so as to be used for growing the nano-aggregates of the next sub-light-emitting layer 310.

[0119] 7. Repeat steps 5 and 6 multiple times until the light-emitting layer 300 is formed.

[0120] Please refer to Figure 16 , Figure 16 This is a schematic diagram of forming a light-emitting layer according to an embodiment of this application. In this embodiment, the process of steps 5 and 6 can be repeated 4 times to manufacture a total of 5 sub-light-emitting layers 310, thereby obtaining a light-emitting layer 300.

[0121] 8. An electron transport layer 810, an electron injection layer 820, and a second electrode 400 are sequentially formed on the side of the light-emitting layer 300 opposite to the first electrode 100.

[0122] Please refer to Figure 17 , Figure 17 This is a schematic diagram of forming an electron transport layer, an electron injection layer, and a second electrode according to an embodiment of this application. In this embodiment, the electron transport layer 810, the electron injection layer 820, and the second electrode 400 can be formed sequentially by a thermal evaporation process after the substrate temperature drops to room temperature.

[0123] For bottom-emitting light-emitting devices, the second electrode 400 can be reflective; for example, the second electrode 400 can be a metal electrode with high reflectivity, such as silver (Ag) or aluminum (Al). For top-emitting light-emitting devices, the first electrode 100 can be reflective; for example, the first electrode 100 can be an ITO / Ag / ITO stacked structure.

[0124] It should be noted that in the above thermal evaporation process, except for the second electrode 400 which uses a metal cathode mask and has an evaporation rate of 0.3 nm / s, all other layers use open masks and have an evaporation rate of 0.1 nm / s. For details, please refer to the process of forming the inducing layer 210 in step 3, which will not be elaborated here.

[0125] This application embodiment can also encapsulate the light-emitting device. For example, in this application embodiment, a glass cover is used to cover the area to be encapsulated, and then UV-curable adhesive is applied around it. The device is then irradiated under a UV lamp with a wavelength of 265nm for 20 to 25 minutes. The final light-emitting area of ​​the resulting device is 2mm × 2mm.

[0126] In summary, this application provides a light-emitting device in which a first crystalline layer is disposed between the first electrode and the light-emitting layer. Since the first crystalline layer is a crystalline thin film, it possesses a regular molecular arrangement, low impurity content, and good stability, enabling the formation of stable carrier transport channels and thereby improving the carrier mobility of the light-emitting device. Furthermore, the light-emitting material formed on the first crystalline layer exhibits a nano-aggregate state. During light emission, the high mobility of holes provided by the first electrode and electrons provided by the second electrode to the nano-aggregates allows for higher current density, thereby enhancing the brightness of the light-emitting device.

[0127] On the other hand, this application also provides a display substrate, which includes: a driving backplate and a plurality of light-emitting devices arranged in an array on one side of the driving backplate. The light-emitting devices can be any of the light-emitting devices provided in the above embodiments.

[0128] Since the display substrate includes the light-emitting device provided in the above embodiments, the display substrate can also have a similar effect, that is, it can achieve high brightness display.

[0129] It should be noted that the dimensions of layers and regions may be exaggerated in the accompanying drawings for clarity. Furthermore, it is understood that when an element or layer is referred to as being "on" another element or layer, it can be directly on the other element, or there may be intermediate layers. Additionally, it is understood that when an element or layer is referred to as being "below" another element or layer, it can be directly below the other element, or there may be more than one intermediate layer or element. Furthermore, it is also understood that when a layer or element is referred to as being "between" two layers or two elements, it can be the only layer between the two layers or two elements, or there may be more than one intermediate layer or element. Similar reference numerals throughout indicate similar elements.

[0130] In this application, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0131] The above description is merely an optional embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A light-emitting device, characterized in that, The light-emitting device includes: a first electrode, a first crystalline layer, a light-emitting layer, and a second electrode stacked together; The light-emitting layer includes: multiple sub-light-emitting layers stacked together; each sub-light-emitting layer includes: a plurality of nano-aggregates, and a functional layer covering the plurality of nano-aggregates; in the same sub-light-emitting layer, the functional layer is in contact with the outer surface of the plurality of nano-aggregates away from the first crystalline layer; For the sub-light-emitting layer closest to the first crystalline layer, a plurality of nano-aggregates in the sub-light-emitting layer are in contact with the surface of the first crystalline layer away from the first electrode, and are dispersed on the surface of the first crystalline layer away from the first electrode; for two adjacent sub-light-emitting layers, a plurality of nano-aggregates in the sub-light-emitting layer further away from the first electrode are in contact with the functional layer in the sub-light-emitting layer closer to the first electrode. The multilayer sub-emitting layer includes: at least one first sub-emitting layer and one second sub-emitting layer; the at least one first sub-emitting layer is located between the second sub-emitting layer and the first crystalline layer; The functional layer in the first sub-light-emitting layer is a second crystalline layer; the nano-aggregate in the first sub-light-emitting layer includes: a first blocking portion, a light-emitting portion, and a second blocking portion stacked in the direction from the first electrode to the second electrode; The functional layer in the second sub-light-emitting layer is a second crystalline layer or a barrier layer that covers the entire layer; when the functional layer in the second sub-light-emitting layer is the second crystalline layer, the nano-aggregates in the second sub-light-emitting layer have the same structure as the nano-aggregates in the first sub-light-emitting layer; when the functional layer in the second sub-light-emitting layer is the barrier layer, the nano-aggregates in the second sub-light-emitting layer include: a first barrier portion and a light-emitting portion stacked in the direction from the first electrode to the second electrode; The triplet energy levels of the first blocking part, the second blocking part, and the blocking layer are all higher than the triplet energy level of the light-emitting part.

2. The light-emitting device according to claim 1, characterized in that, The first blocking portion is reused as an electron blocking layer, and the second blocking portion is reused as a hole blocking layer.

3. The light-emitting device according to claim 1, characterized in that, The materials of the light-emitting part include: P-type main material and N-type main material; The material of the first blocking part includes the P-type main body material, and the material of the second blocking part includes the N-type main body material.

4. The light-emitting device according to claim 1, characterized in that, The surface of the first blocking portion near the first crystalline layer is a plane, and the surface of the first blocking portion away from the first crystalline layer is a first curved surface protruding toward the second electrode; The light-emitting part covers the surface of the first blocking part away from the first crystalline layer, and the surface of the light-emitting part away from the first blocking part is a second curved surface that protrudes toward the second electrode; The second blocking portion covers the surface of the light-emitting portion opposite to the first blocking portion, and the surface of the second blocking portion opposite to the light-emitting portion is a third curved surface protruding toward the second electrode.

5. The light-emitting device according to any one of claims 1 to 4, characterized in that, The light-emitting device further includes: a planarization layer, the planarization layer being located between the first electrode and the first crystalline layer; The roughness of the surface of the planarization layer facing away from the first electrode is less than the roughness of the surface of the first electrode facing the second electrode, and the planarization layer is reused as a hole injection layer.

6. The light-emitting device according to any one of claims 1 to 4, characterized in that, The first crystalline layer includes an induction layer and an epitaxial layer stacked along a direction away from the first electrode; In this embodiment, at least one of the sub-light-emitting layers has a functional layer that is a second crystalline layer, and the material of the epitaxial layer is the same as that of the second crystalline layer.

7. The light-emitting device according to claim 6, characterized in that, The epitaxial layer is reused as a hole transport layer.

8. The light-emitting device according to any one of claims 1 to 4, characterized in that, The total thickness of the nano-aggregates in each of the sub-luminescent layers ranges from 20 nanometers to 40 nanometers.

9. The light-emitting device according to any one of claims 1 to 4, characterized in that, In one of the sub-luminescent layers, the ratio of the total area of ​​the orthogonal projection of the plurality of nano-aggregates onto the first crystalline layer to the total area of ​​the first crystalline layer is in the range of 20% to 30%.

10. The light-emitting device according to any one of claims 1 to 4, characterized in that, The thickness of the nanoaggregate in the direction perpendicular to the first electrode ranges from 4 nanometers to 6 nanometers. The diameter of the orthogonal projection of the nanoaggregate onto the first electrode ranges from 50 nanometers to 70 nanometers.

11. A display substrate, characterized in that, include: A driving backplate, and a plurality of light-emitting devices arranged in an array on one side of the driving backplate, wherein the light-emitting devices are the light-emitting devices according to any one of claims 1 to 10.

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