Light-emitting device and preparation method therefor, display panel and display apparatus

Abstract

Provided are a light-emitting device and a preparation method therefor, a display panel and a display apparatus, which belong to the technical field of display. In the light-emitting device, a light-emitting layer of a first color comprises a first host layer and a second host layer. The first host layer comprises a first host material and a first guest material, and the second host layer comprises a second host material and a second guest material. The first host material is an electron-transport-type material or a hole-transport-type material, and the second host material is a mixed-transport-type material for both electrons and holes; therefore, by means of loading currents of different magnitudes to electrodes, during low-brightness display and high-brightness display, excitons formed by an encounter between electrons and holes can be located in different host layers. In addition, the first guest material and the second guest material respectively have the light emission characteristics of spectrums of different widths, and therefore light in colors of different depths can be emitted during low-brightness display and high-brightness display. In this way, good display flexibility can be ensured, and three indicators, i.e., color gamut, power consumption and service life, can also be better compatible with each other.

Description

Light-emitting device and manufacturing method thereof, display panel, and display device Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to a light-emitting device and a manufacturing method thereof, a display panel, and a display apparatus. Background Art

[0002] White organic light-emitting devices (WOLEDs) are a type of OLED. They typically use stacked multi-colored light-emitting layers to emit white light, and then use color filters (CFs) to achieve color display. They are mostly used in television products (TVs).

[0003] In related technologies, WOLEDs generally include an anode, an emitting layer (EML), and a cathode stacked in sequence. The emitting layer can emit light when driven by a current between the cathode and the anode. The emitting layer includes a blue emitting layer, a red emitting layer, and a green emitting layer.

[0004] However, due to factors such as wavelength and materials, current display products including WOLED cannot simultaneously and effectively meet the three indicators of color gamut, power consumption and lifespan, and have poor display flexibility.

[0005] Summary of the Invention

[0006] Provided are a light-emitting device and a method for manufacturing the same, a display panel, and a display device. The technical solution is as follows:

[0007] In one aspect, a light-emitting device is provided, comprising: a first electrode, a light-emitting layer of a first color, and a second electrode stacked in sequence; the light-emitting layer of the first color comprises: a first host layer and a second host layer stacked in sequence;

[0008] Wherein, the first host layer comprises a first host material and a first guest material; the second host layer comprises a second host material and a second guest material;

[0009] In addition, the first host material is an electron transport material or a hole transport material, and the second host material is a mixed transport material, the proportion of holes in the mixed transport material is less than the proportion of electrons; the first guest material has the luminescence characteristics of a first spectrum, and the second guest material has the luminescence characteristics of a second spectrum, and the widths of the first spectrum and the second spectrum are different; the thickness of the second host layer is greater than the thickness of the first host layer.

[0010] Optionally, the first host material is the electron transport material, and the width of the first spectrum is smaller than the width of the second spectrum.

[0011] Optionally, the first host material is the hole transport material, and the width of the first spectrum is greater than the width of the second spectrum.

[0012] Optionally, the ratio of holes to electrons in the mixed transport material satisfies 3:7.

[0013] Optionally, the thickness of the second main layer is greater than 100 nanometers.

[0014] Optionally, the light emitting device further comprises: an intermediate layer located between the first main layer and the second main layer;

[0015] Moreover, the material of the intermediate layer is the hole transport material or the electron transport material, and the material of the intermediate layer is the same as the first main material; the thickness of the intermediate layer is less than the thickness of the first main layer, and the thickness of the intermediate layer is less than the thickness of the second main layer.

[0016] Optionally, the thickness of the intermediate layer is between 4 nanometers and 6 nanometers.

[0017] Optionally, the light-emitting layer of the first color further includes: a third main body layer; the first main body layer, the second main body layer and the third main body layer are stacked in sequence;

[0018] wherein the third host layer comprises a third host material and the second guest material;

[0019] Furthermore, the third host material is the electron transport material or the hole transport material, and the third host material is different from the first host material; and the thickness of the second host layer is smaller than that of the third host layer.

[0020] Optionally, both the first guest material and the second guest material include fluorescent materials.

[0021] Optionally, the light emitting device further includes:

[0022] a hole injection layer, a hole transport layer, and an electron blocking layer located between the first electrode and the light-emitting layer of the first color and stacked in sequence in a direction away from the first electrode;

[0023] An electron injection layer, an electron transport layer, and a hole blocking layer are located between the second electrode and the light-emitting layer of the first color and are sequentially stacked in a direction away from the second electrode.

[0024] Optionally, the first host layer and the second host layer, wherein the first host material is an electron transport material, are sequentially stacked in a direction away from the second electrode;

[0025] The first host layer and the second host layer, in which the first host material is a hole transport material, are sequentially stacked in a direction away from the first electrode.

[0026] Optionally, the light emitting device further comprises: a light emitting layer of a second color and a light emitting layer of a third color, which are located between the first electrode and the second electrode and are stacked in sequence;

[0027] The first color is blue, the second color is red, and the third color is green.

[0028] Optionally, the first electrode is an anode and the second electrode is a cathode;

[0029] Furthermore, the material of the first electrode includes a transparent conductive material; and the material of the second electrode includes a metal material.

[0030] Optionally, the transparent conductive material includes: indium tin oxide material.

[0031] In another aspect, a method for preparing a light-emitting device is provided, for preparing the light-emitting device according to the above aspect, the method comprising:

[0032] forming a first electrode;

[0033] forming a first host layer on one side of the first electrode using a first host material and a first guest material doped in the first host material;

[0034] forming a second host layer on one side of the first host layer using a second host material and a second guest material doped in the second host material to obtain a light-emitting layer of a first color;

[0035] forming a second electrode on a side of the light-emitting layer of the first color away from the first electrode;

[0036] In which, the first main material is an electron transport material or a hole transport material, the second main material is a mixed transport material, the proportion of holes in the mixed transport material is less than the proportion of electrons; the first guest material has the luminescence characteristics of a first spectrum, the second guest material has the luminescence characteristics of a second spectrum, the width of the first spectrum is different from the width of the second spectrum; and the thickness of the formed second main layer is greater than the thickness of the formed first main layer.

[0037] Optionally, before forming the second electrode, the method further includes:

[0038] forming an intermediate layer between the first main layer and the second main layer using the hole transport material or the electron transport material;

[0039] The material used to form the intermediate layer is the same as the material of the first main body; and the thickness of the intermediate layer is smaller than that of the first main body layer, and the thickness of the intermediate layer is smaller than that of the second main body layer.

[0040] Optionally, after forming the second main body layer, the method further includes:

[0041] forming a third host layer on a side of the second host layer away from the first host layer using a third host material and the second guest material doped in the third host material to obtain a light-emitting layer of the first color;

[0042] The third host material is the electron transport material or the hole transport material, and the third host material is the same as the first host material; and the thickness of the formed second host layer is smaller than the thickness of the formed third host layer.

[0043] In yet another aspect, a display panel is provided, comprising: a substrate, and a plurality of light-emitting devices as described in the above aspect located on one side of the substrate.

[0044] Optionally, the light-emitting device is a white organic electroluminescent device; and the display panel further comprises: a color filter located on a side of the light-emitting device away from the substrate.

[0045] In another aspect, a display device is provided, comprising: a driving circuit, and the display panel according to the above-mentioned further aspect;

[0046] The driving circuit is connected to the light-emitting device in the display panel and is used to drive the light-emitting device to emit light. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0048] FIG1 is a schematic structural diagram of a light-emitting device provided by an embodiment of the present disclosure;

[0049] FIG2 is a schematic structural diagram of another light-emitting device provided in an embodiment of the present disclosure;

[0050] FIG3 is a schematic structural diagram of another light-emitting device provided in an embodiment of the present disclosure;

[0051] FIG4 is a schematic structural diagram of another light emitting device provided in an embodiment of the present disclosure;

[0052] FIG5 is a schematic structural diagram of another light emitting device provided in an embodiment of the present disclosure;

[0053] FIG6 is a schematic structural diagram of another light emitting device provided in an embodiment of the present disclosure;

[0054] FIG7 is a schematic structural diagram of another light emitting device provided in an embodiment of the present disclosure;

[0055] FIG8 is a schematic structural diagram of another light emitting device provided in an embodiment of the present disclosure;

[0056] FIG9 is a schematic flow chart of a method for preparing a light-emitting device according to an embodiment of the present disclosure;

[0057] FIG10 is a schematic flow chart of another method for preparing a light-emitting device provided in an embodiment of the present disclosure;

[0058] FIG11 is a schematic flow chart of another method for preparing a light-emitting device according to an embodiment of the present disclosure;

[0059] FIG12 is a schematic structural diagram of a display panel provided by an embodiment of the present disclosure;

[0060] FIG13 is a schematic structural diagram of another display panel provided by an embodiment of the present disclosure;

[0061] FIG14 is a schematic structural diagram of a display device provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0062] In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

[0063] Currently, display products like WOLED TVs face a trade-off between color gamut and power consumption, as well as between power consumption and lifespan. For example, when pursuing display quality, color gamut and power consumption are primary indicators to meet consumers' daily viewing experience. However, when pursuing absolute brightness, power consumption and lifespan are primary, with color gamut being irrelevant. Therefore, it is highly desirable to provide a display product that meets both color gamut and power consumption requirements at low brightness levels, while being unconstrained by color gamut at high brightness levels, focusing solely on absolute brightness. Understandably, the color gamut requires a deeper blue, greener, and redder color, meaning that the blue light must be deep blue. However, the efficiency and lifespan of the materials used in the blue light-emitting layer that emits deep blue light are both shortcomings. The reasons are: first, the shorter wavelength results in lower brightness, creating a bottleneck for WOLEDs to achieve high brightness. Second, the blue light-emitting layer has a poor lifespan due to the two-photon absorption (TPA) mechanism. The TPA mechanism involves excess triplet excitons T reacting with free charge carriers to generate higher energy, destroying the structure of the luminescent molecule. However, if the excess triplet excitons T can be transferred and reused to form triplet-triplet annihilation (TTA), the luminescence efficiency can be increased, thereby improving the display effect. The principle of TTA is that non-luminescent triplet excitons T collide with each other to generate singlet excitons that can emit light.

[0064] To address these issues, the present disclosure provides a light-emitting device capable of emitting light of varying depths (e.g., deep blue and light blue) at varying brightness levels. This achieves both a high color gamut and high brightness, resulting in greater display flexibility. As shown in Figure 1 , the light-emitting device provided by the present disclosure includes a first electrode 01, a light-emitting layer 02 of a first color, and a second electrode 03, stacked sequentially.

[0065] Optionally, one of the first electrode 01 and the second electrode 03 may be an anode and the other may be a cathode. The light-emitting layer 02 of the first color may emit light under the current driven by the first electrode 01 and the second electrode 03. The first color may be blue as described above, but is certainly not limited to blue.

[0066] Based on FIG1 and in combination with FIG2 , it can be seen that the first color light emitting layer 02 includes: a first host layer 021 and a second host layer 022 stacked in sequence. That is, the blue light emitting layer 02 may include two layers of blue host.

[0067] Among them, the first host layer 021 includes a first host material BH1 and a first guest material BD1. The second host layer 022 includes a second host material BH2 and a second guest material BD2. The first guest material BD1 can be a luminescent material doped in the first host material BH1, that is, the luminescent molecule described above. The second guest material BD2 is the same and will not be elaborated here.

[0068] Moreover, the first host material BH1 is an electron-transporting material or a hole-transporting material, the second host material BH2 is a mixed-transporting material, and the proportion of holes in the mixed-transporting material is less than the proportion of electrons. The first guest material BD1 has the luminescent characteristics of a first spectrum, the second guest material BD2 has the luminescent characteristics of a second spectrum, and the widths of the first spectrum and the second spectrum are different. The thickness of the second host layer 022 is greater than the thickness of the first host layer 021. Among them, referring to FIG. 1, the thickness direction can be the direction perpendicular to the first electrode 01, and the thickness can also be referred to as the width.

[0069] It can be understood that the electron-transporting material is also an N-type semiconductor material, the hole-transporting material is also a P-type semiconductor material, and the mixed-transporting material is also a transporting material doped with electrons N and holes P. Moreover, in this mixed-transporting material, the content of P < the content of N. On this basis, it can also be determined that the triplet energy level T1 of the second host material BH2 can be greater than the triplet energy level T1 of the first host material BH1. It can also be understood that the second host layer 022 is a high-energy-level host layer, and the first host layer 021 is a low-energy-level host layer. Moreover, for distinction, in the embodiments of the present disclosure, the first host material BH1 that is an electron-transporting material is labeled as BH1-1, and the first host material BH1 that is a hole-transporting material is labeled as BH1-2.

[0070] For example, in the light-emitting device shown in FIG. 2, the first host material BH1 is an electron-transporting material BH1-1. In the light-emitting device shown in FIG. 3, the first host material BH1 is a hole-transporting material BH1-2.

[0071] It can also be understood that the first guest material BD1 having the luminescent characteristics of a first spectrum can mean that the first guest material BD1 can emit light within a first wavelength range. Similarly, the second guest material BD2 having the luminescent characteristics of a second spectrum can mean that the second guest material BD2 can emit light within a second wavelength range.

[0072] For example, referring to Figure 2 , in one embodiment, the width of the first spectrum can be smaller than the width of the second spectrum, that is, the first spectrum can be a narrow spectrum, and the second spectrum can be a broad spectrum. Accordingly, the upper limit of the first wavelength range can be smaller than the lower limit of the second wavelength range. The first guest material BD1 can emit light of a darker first color, such as dark blue light, while the second guest material BD2 can emit light of a lighter first color, such as light blue light. In other words, the first guest material BD1 doped in the first host material BH1 can emit light of a narrow dark blue spectrum, while the second guest material BD2 doped in the second host material BH2 can emit light of a broad light blue spectrum.

[0073] Alternatively, in conjunction with Figure 3 , in another embodiment, the width of the first spectrum can be greater than the width of the second spectrum, that is, the first spectrum can be a broad spectrum, and the second spectrum can be a narrow spectrum. Accordingly, the lower limit of the first wavelength range can be greater than the upper limit of the second wavelength range. The first guest material BD1 can emit light of a lighter first color, such as light blue, while the second guest material BD2 can emit light of a darker first color, such as deep blue. In other words, the first guest material BD1 doped in the first host material BH1 can emit light of a broad light blue spectrum, while the second guest material BD2 doped in the second host material BH2 can emit light of a narrow deep blue spectrum.

[0074] Taking the structures shown in FIG2 and FIG3 , where the first color is blue, as an example, the light-emitting principle of the light-emitting device is described as follows:

[0075] (1) For the structure shown in FIG2 , that is, the first host material BH1 is an electron transport material BH1-1, the second host material BH2 is a mixed transport material, the first guest material BD1 has a deep blue narrow spectrum luminescence characteristic, and the second guest material BD2 has a light blue broad spectrum luminescence characteristic:

[0076] When displayed at low brightness, since the current loaded between the first electrode 01 and the second electrode 03 is small, the electron migration rate can be reduced, and the excitons formed after the holes and electrons meet can be located at the low brightness position shown in Figure 2, that is, at the junction of the first main layer 021 and the second main layer 022 and close to the first main layer 021, so that the light-emitting device can emit deep blue light of the first guest material BD1.

[0077] When the display is highlighted, since the current loaded between the first electrode 01 and the second electrode 03 is large, the electron migration rate can be faster, and the excitons formed after the holes and electrons meet can be located at the highlighted position shown in Figure 2, that is, in the second main layer 022, so that the light-emitting device can emit light blue light of the second guest material BD2.

[0078] In addition, in combination with Figure 2, it can be seen that although the triplet energy level T1 of the second host material BH2 is greater than the triplet energy level T1 of the first host material BH1-1, because the thickness of the second host layer 022 is greater than the thickness of the first host layer 021, it can be ensured that during highlight display, the excess T energy will not be transferred from the high-energy level second host layer 022 to the low-energy level first host layer 021, thereby ensuring that the light-emitting device can reliably emit the light blue light of the second guest material BD2 during highlight display, ensuring a better display effect.

[0079] Optionally, in the embodiment of the present disclosure, low-brightness display may refer to a display with a brightness less than 250 nits; correspondingly, high-brightness display may refer to a display with a brightness greater than 250 nits.

[0080] (2) For the structure shown in FIG3 , that is, the first host material BH1 is a hole transport material BH1-2, the second host material BH2 is a mixed transport material, the first guest material BD1 has a light blue broad spectrum luminescence characteristic, and the second guest material BD2 has a deep blue narrow spectrum luminescence characteristic:

[0081] When displayed at low brightness, since the current loaded between the first electrode 01 and the second electrode 03 is small, the electron migration rate can be made smaller, and the excitons formed after the holes and electrons meet can be located at the low brightness position shown in Figure 3, that is, in the second main layer 022, so that the light-emitting device can emit deep blue light of the second guest material BD2.

[0082] When the display is highlighted, since the current loaded between the first electrode 01 and the second electrode 03 is large, the electron migration rate can be faster, and the excitons formed after the holes and electrons meet can be located at the highlighted position shown in Figure 3, that is, at the junction of the first main layer 021 and the second main layer 022 and close to the first main layer 021, so that the light-emitting device can emit light blue light of the first guest material BD1.

[0083] In addition, in combination with Figure 3, it can be seen that although the triplet energy level T1 of the second host material BH2 is greater than the triplet energy level T1 of the first host material BH1-2, because the thickness of the second host layer 022 is greater than the thickness of the first host layer 021, it can be ensured that during high-brightness display, the excess T energy will not be transferred from the high-energy level second host layer 022 to the low-energy level first host layer 021, thereby ensuring that the light-emitting device can reliably emit the deep blue light of the second guest material BD2 during low-brightness display, thereby ensuring a better display effect.

[0084] That is, combined with the above records, it can be determined that by setting an electron-transporting host material and a mixed-transporting host material in which the hole ratio is smaller than the electron ratio, or by setting a hole-transporting host material and a mixed-transporting host material in which the hole ratio is smaller than the electron ratio, it is possible to drive the excitons formed by the encounter of electrons and holes to be located in different host layers under low-brightness display and high-brightness display, respectively. By setting guest materials with spectral characteristics of different widths in different host layers, it is possible to further drive the light-emitting device to emit light of the first color of different depths, such as dark blue light and light blue light, under low-brightness display and high-brightness display, respectively. Because dark blue light contributes to high color gamut and light blue light contributes to high brightness, it can make the display product better compatible with the three indicators of color gamut, power consumption and lifespan, thereby improving display flexibility.

[0085] In summary, the embodiments of the present disclosure provide a light-emitting device. In the light-emitting device, the light-emitting layer of the first color includes a first main layer and a second main layer. The first main layer includes a first main material and a first guest material, and the second main layer includes a second main material and a second guest material. Because the first main material is an electron transport material or a hole transport material, and the second main material is a mixed transport material in which electrons and holes are mixed, it is possible to load currents of different sizes to the electrodes so that the excitons formed by the encounter of electrons and holes are located in different main layers during low-brightness display and high-brightness display. Because the first guest material and the second guest material have luminescent properties with spectrums of different widths, respectively, light of different depths of color can be emitted during low-brightness display and high-brightness display. In this way, it is possible to ensure better display flexibility while better compatibility with the three indicators of color gamut, power consumption and lifespan.

[0086] Optionally, it can be seen from FIG. 2 that in an optional implementation of the embodiment of the present disclosure:

[0087] The first host material BH1 can be an electron-transporting material BH1-1, and the width of the first spectrum can be smaller than the width of the second spectrum. That is, the first guest material BD1 can have a narrow spectrum of deep blue light, while the second guest material BD2 can have a broad spectrum of light blue light. Therefore, taking blue as the first color as an example, based on the previous description of the light-emitting principle of the structure shown in Figure 2, it can be seen that the light-emitting device with this structure can emit deep blue light from the first guest material BD1 during low-brightness display, and can emit light blue light from the second guest material BD2 during high-brightness display.

[0088] Optionally, it can be seen from FIG3 that in another optional implementation of the embodiment of the present disclosure:

[0089] The first host material BH1 can be a hole-transporting material BH1-2, and the width of the first spectrum can be greater than the width of the second spectrum. That is, the first guest material BD1 can have a broad spectrum of light-blue light, while the second guest material BD2 can have a narrow spectrum of deep-blue light. Therefore, taking blue as the first color as an example, based on the aforementioned description of the light-emitting principle of the structure shown in FIG3 , it can be seen that the light-emitting device with this structure can emit deep-blue light from the second guest material BD2 during low-brightness display, and can emit light-blue light from the first guest material BD1 during high-brightness display.

[0090] Optionally, in the disclosed embodiment, the hole-to-electron ratio in the hybrid transport material satisfies a ratio of 3:7. That is, the P:N ratio can be 3:7. This effectively ensures that excitons can be reliably formed in the low-brightness and high-brightness positions shown in Figures 2 or 3, thereby ensuring a better display effect.

[0091] Optionally, in the embodiment of the present disclosure, the thickness of the second main layer 022 may be greater than 100 nanometers (nm). In this way, the transfer of excessive T energy and the influence on luminescence can be avoided, thereby further ensuring a better display effect.

[0092] Alternatively, FIG4 shows a schematic structural diagram of another light-emitting device based on FIG2 . FIG5 shows a schematic structural diagram of another light-emitting device based on FIG3 . As shown in FIG4 and FIG5 , the light-emitting device in the embodiment of the present disclosure may further include: an interlayer 04 located between the first main layer 021 and the second main layer 022 .

[0093] Furthermore, the material of the intermediate layer 04 can be a hole transport material or an electron transport material, and the material of the intermediate layer 04 can be the same as the first host material BH1. The thickness of the intermediate layer 04 can be less than that of the first host layer 021, and the thickness of the intermediate layer 04 can be less than that of the second host layer 022.

[0094] That is, based on Figure 2 and in conjunction with Figure 4 , it can be seen that if the first host material BH1 is an electron-transporting material BH1-1, then the intermediate layer 04 can be an electron-transporting material, also known as an N-type transport material. Based on Figure 3 and in conjunction with Figure 5 , it can be seen that if the first host material BH1 is a hole-transporting material BH1-2, then the intermediate layer 04 can be a hole-transporting material, also known as a P-type transport material.

[0095] It is understood that the light-emitting principle of the light-emitting device further provided with the intermediate layer 04 can refer to the above description. That is, in conjunction with Figure 4, the intermediate layer 04 is provided on the basis of Figure 2, so that the low-brightness position is located at the junction of the first host layer 021 and the intermediate layer 04 and is close to the first host layer 021, and the high-brightness position is located within the second host layer 022. This ensures that the light-emitting device can reliably emit the deep blue light of the first guest material BD1 during low-brightness display, and that the light-emitting device can reliably emit the light blue light of the second guest material BD2 during high-brightness display. In conjunction with Figure 5, the intermediate layer 04 is provided on the basis of Figure 3, so that the low-brightness position is located within the second host layer 022, and the high-brightness position is located at the junction of the first host layer 021 and the intermediate layer 04 and is close to the first host layer 021. This ensures that the light-emitting device can reliably emit the deep blue light of the second guest material BD2 during low-brightness display, and that the light-emitting device can reliably emit the light blue light of the first guest material BD1 during high-brightness display.

[0096] Moreover, the addition of the intermediate layer 04 can increase the distance between the second main layer 022 and the first main layer 021, which can also be understood as further increasing the thickness of the second main layer 022, thereby further reliably ensuring that the excess T energy will not be transferred from the high-energy-level second main layer 022 to the low-energy-level first main layer 021, thereby ensuring a better display effect.

[0097] Optionally, the thickness of the intermediate layer 04 may be between 4 nm and 6 nm, that is, 4-6 nm. It is understood that between 4 nm and 6 nm may mean: greater than or equal to 4 nm and less than or equal to 6 nm.

[0098] Alternatively, based on Figure 5 and further combined with Figure 6 , it can be seen that in the disclosed embodiment, the first-color light-emitting layer 02 can further include a third host layer 023. Furthermore, the first host layer 021, the second host layer 022, and the third host layer 023 can be stacked in sequence. That is, for example, the blue light-emitting layer 02 can include three layers of blue host.

[0099] The third host layer 023 may include a third host material BH3 and a second guest material BD2.

[0100] Furthermore, the third host material BH3 may be an electron transport material or a hole transport material, and the third host material BH3 may be different from the first host material BH1 . The thickness of the second host layer 022 may be smaller than that of the third host layer 023 .

[0101] That is, as can be seen from Figure 5 and Figure 6 , if the first host material BH1 is a hole-transporting material BH1-2, then the third host material BH3 can be an electron-transporting material BH1-1. Based on Figure 4 , if the first host material BH1 is an electron-transporting material BH1-1, then the third host material BH3 can be a hole-transporting material BH1-2. Based on this, it can also be determined that the triplet energy level T1 of the second host material BH2 can be greater than the triplet energy level T1 of the third host material BH3. This can also be understood as the second host layer 022 being a high-energy-level host layer, and the third host layer 023 being a low-energy-level host layer.

[0102] For the structure shown in FIG6 , that is, the first host material BH1 is a hole-transporting material BH1-2, the second host material BH2 is a mixed-transporting material, the third host material BH3 is an electron-transporting material BH1-1, and the first guest material BD1 has a light-blue broad-spectrum luminescence characteristic, and the second guest material BD2 has a deep-blue narrow-spectrum luminescence characteristic. Taking blue as the first color as an example, the light-emitting principle of the light-emitting device is described as follows:

[0103] When displaying at low brightness, the current flowing between the first electrode 01 and the second electrode 03 is relatively low, which reduces the electron migration rate. This allows the excitons formed by the interaction of holes and electrons to be located at the low-brightness position shown in Figure 6, that is, within the second host layer 022. This allows the light-emitting device to emit deep blue light from the second guest material BD2. Furthermore, because the triplet energy level T1 of the second host material BH2 is greater than that of the third host material BH3, and the thickness of the second host layer 022 is relatively small, as shown in Figure 6, the excess T energy is transferred from the high-energy level of the second host layer 022 to the low-energy level of the third host layer 023, causing the third host layer 023 to also emit deep blue light from the second guest material BD2. This increases the brightness of the deep blue light.

[0104] When the display is highlighted, since the current loaded between the first electrode 01 and the second electrode 03 is large, the electron migration rate can be faster, and the excitons formed after the holes and electrons meet can be located at the highlighted position shown in Figure 6, that is, at the junction of the first main layer 021 and the second main layer 022 and close to the first main layer 021, so that the light-emitting device can emit light blue light of the first guest material BD1.

[0105] It can be understood that, in the structure shown in FIG6 , the energy levels of the first main layer 021 and the second main layer 022 are comparable, so the excess T energy will not be transferred between the two.

[0106] Optionally, in the disclosed embodiment, both the first guest material BD1 and the second guest material BD2 may include a fluorescent material. For example, if the first color is blue, the fluorescent material may be a blue fluorescent material that emits blue light. Furthermore, the first guest material BD1 and the second guest material BD2 may be of the same or different types.

[0107] Optionally, as shown in Figure 7, the light-emitting device provided by the embodiment of the present disclosure may further include: a hole injection layer (HIL), a hole transport layer (HTL) and an electron blocking layer (B-Prime) located between the first electrode 01 and the light-emitting layer 02 of the first color, and stacked in sequence in a direction away from the first electrode 01.

[0108] Also, an electron injection layer (EIL), an electron transport layer (ETL), and a hole blocking layer (HBL) are located between the second electrode 03 and the first color light-emitting layer 02 and sequentially stacked in a direction away from the second electrode 03 .

[0109] It is understood that the hole injection layer HIL can inject holes when driven by a current between the first electrode 01 and the second electrode 03. The hole transport layer HTL can transport the injected holes to the first color light-emitting layer 02. The electron injection layer EIL can inject electrons when driven by a current between the first electrode 01 and the second electrode 03. The electron transport layer ETL can transport the injected electrons to the first color light-emitting layer 02. The electron blocking layer B-Prime can block electrons injected into the first color light-emitting layer 02, preventing them from being mistakenly transported to one side of the hole transport layer HTL, the hole injection layer HIL, and the first electrode 01. The hole blocking layer HBL can block holes injected into the first color light-emitting layer 02, preventing them from being mistakenly transported to one side of the electron transport layer ETL, the electron injection layer EIL, and the second electrode 03. Figures 2 to 6 schematically illustrate the electron blocking layer B-Prime and the hole blocking layer HBL located on both sides of the first color light-emitting layer 02.

[0110] Furthermore, based on the structure shown in FIG7 , since a hole injection layer HIL and a hole transport layer HTL are provided on the side of the first electrode 01, and an electron injection layer EIL and an electron transport layer ETL are provided on the side of the second electrode 03, the first host layer 021 and the second host layer 022 of the electron transport material BH1-1, which are the first host material BH1, can be stacked sequentially in a direction away from the second electrode 03. That is, as shown in FIG2 , the electron blocking layer B-Prime, the second host layer 022, the first host layer 021, and the hole blocking layer HBL can be stacked sequentially. Furthermore, the first host layer 021 and the second host layer 022 of the hole transport material BH1-2, which are the first host material BH1, can be stacked sequentially in a direction away from the first electrode 01. That is, as shown in FIG2 , the electron blocking layer B-Prime, the first host layer 021, the second host layer 022, and the hole blocking layer HBL can be stacked sequentially.

[0111] Alternatively, in the embodiment of the present disclosure, the first electrode 01 may be an anode, and the second electrode 03 may be a cathode. Furthermore, the material of the first electrode 01 may include a transparent conductive material, and the material of the second electrode 03 may include a metal material.

[0112] For example, the transparent conductive material may include indium tin oxide (ITO) material.

[0113] Optionally, as shown in FIG8 , the light-emitting device provided by the embodiment of the present disclosure may further include: a second color light-emitting layer 05 and a third color light-emitting layer 06 located between the first electrode 01 and the second electrode 03 and stacked in sequence.

[0114] The first color may be the blue color mentioned above, the second color may be red, and the third color may be green. In this way, the light-emitting device formed is the WOLED mentioned above.

[0115] It is understood that the region where excitons reside is also generally referred to as the recombination zone. Thus, it can be seen that the solution provided by the embodiments of the present disclosure can flexibly control the location of the recombination zone under different brightness displays by combining different host and guest materials, thereby enabling the light-emitting device to emit dark light that contributes to a high color gamut or light light that contributes to high brightness.

[0116] It is also understood that the relative positions of the film layers in Figures 2 to 6 are drawn according to energy levels and do not represent height differences in the actual structure. For example, the film layers in the actual structure may be aligned.

[0117] In summary, the embodiments of the present disclosure provide a light-emitting device. In the light-emitting device, the light-emitting layer of the first color includes a first main layer and a second main layer. The first main layer includes a first main material and a first guest material, and the second main layer includes a second main material and a second guest material. Because the first main material is an electron transport material or a hole transport material, and the second main material is a mixed transport material in which electrons and holes are mixed, it is possible to load currents of different sizes to the electrodes so that the excitons formed by the encounter of electrons and holes are located in different main layers during low-brightness display and high-brightness display. Because the first guest material and the second guest material have luminescent properties with spectrums of different widths, respectively, light of different depths of color can be emitted during low-brightness display and high-brightness display. In this way, it is possible to ensure better display flexibility while better compatibility with the three indicators of color gamut, power consumption and lifespan.

[0118] The present disclosure also provides a method for preparing a light-emitting device, which can be used to prepare a light-emitting device as shown in any one of Figures 1 to 8. As shown in Figure 9, the method includes:

[0119] Step 901: forming a first electrode.

[0120] Optionally, with reference to FIG. 1 , a substrate may be provided first, and then a conductive material (eg, ITO) may be evaporated on one side of the substrate to form the first electrode 01 .

[0121] Step 902 : Form a first host layer on one side of the first electrode using a first host material and a first guest material doped in the first host material.

[0122] Step 903 : forming a second host layer on one side of the first host layer using a second host material and a second guest material doped in the second host material to obtain a light-emitting layer of a first color.

[0123] Optionally, referring to FIG2 , after forming the first electrode, a first host material BH1 and a second host material BH2 can be evaporated on one side of the first electrode 01, and the first guest material BD1 can be doped into the first host material BH1, and the second guest material BD2 can be doped into the second host material BH2, to form a first host layer 021 and a second host layer 022, respectively, to obtain a first-color light-emitting layer 02. In this case, the first-color light-emitting layer 02 formed can be considered as a two-layer host light-emitting layer.

[0124] The first host material BH1 used is an electron-transporting material or a hole-transporting material, and the second host material BH2 is a mixed-transporting material, in which the proportion of holes is less than the proportion of electrons. The first guest material BD1 has luminescence characteristics of a first spectrum, and the second guest material BD2 has luminescence characteristics of a second spectrum. The first spectrum and the second spectrum have different widths, that is, the first guest material BD1 and the second guest material BD2 can respectively have luminescence characteristics of a narrow spectrum of deep blue light and a wide spectrum of light blue light. In addition, the thickness of the formed second host layer 022 is greater than the thickness of the formed first host layer 021. This can prevent excessive T energy from being transferred from the second host layer 022 to the first host layer 021, ensuring a better display effect.

[0125] Step 904: forming a second electrode on a side of the light-emitting layer of the first color away from the first electrode.

[0126] 1 , after forming the first color light-emitting layer 02 , a conductive material (eg, metal material) may be evaporated on a side of the first color light-emitting layer 02 away from the first electrode 01 to form the second electrode 03 .

[0127] Optionally, based on the structures shown in FIG. 3 and FIG. 4 , in combination with FIG. 10 , it can be seen that before forming the second electrode, the preparation method described in the embodiment of the present disclosure may further include:

[0128] Step 905 : forming an intermediate layer between the first main layer and the second main layer using a hole transport material or an electron transport material.

[0129] The material used to form the intermediate layer can be the same as the material of the first main body. Furthermore, the thickness of the intermediate layer can be less than that of the first main body layer, and the thickness of the intermediate layer can be less than that of the second main body layer. In this way, in conjunction with Figures 3 and 4 , the distance between the second main body layer 022 and the first main body layer 021 can be increased, further preventing excessive T energy from being transferred from the second main body layer 022 to the first main body layer 021.

[0130] It can be understood, in conjunction with Figures 3 and 4, that after forming the first bulk layer 021, a hole transport material or an electron transport material may be evaporated on one side of the first bulk layer 021 to form the intermediate layer 04, and then the second bulk layer 022 may be further formed on the side of the intermediate layer 04 away from the first bulk layer 021. In other words, step 905 may actually be performed between steps 902 and 903.

[0131] Optionally, based on the structure shown in FIG6 and in combination with FIG11 , it can be seen that after forming the second main body layer, the preparation method described in the embodiment of the present disclosure may further include:

[0132] Step 906 : Form a third host layer on a side of the second host layer away from the first host layer using a third host material and a second guest material doped in the third host material to obtain a light-emitting layer of the first color.

[0133] The third host material can be an electron-transporting material or a hole-transporting material, and the third host material can be different from the first host material. Furthermore, the thickness of the second host layer can be smaller than that of the third host layer. This allows excess T energy to be transferred from the second host layer 022 to the third host layer 023, increasing the brightness of the light-emitting device when emitting light from the second guest material BD2.

[0134] That is, referring to Figure 6 , after forming the second host layer 022, a third host material can be evaporated on the side of the second host layer 022 away from the first host layer 021, and the second guest material can be doped into the third host material to form a third host layer 023, thereby obtaining the first-color light-emitting layer 02. In this case, the first-color light-emitting layer 02 formed can be considered a three-layer host light-emitting layer.

[0135] Optionally, with reference to FIG7 , before forming the first body layer 021, that is, before executing step 902, a hole injection layer HIL, a hole transport layer HTL, and an electron blocking layer B-Prime may be sequentially formed by evaporation on one side of the first electrode 01, and then step 902 may be executed to form the first body layer 021. Furthermore, after forming the second body layer 022, that is, after executing step 903, a hole blocking layer HBL, an electron transport layer ETL, and an electron injection layer EIL may be sequentially formed by evaporation on the side of the second body layer 022 away from the first body layer 021, and then step 904 may be executed to form the second electrode 03.

[0136] It can be understood that since the preparation method of the light-emitting device can have basically the same technical effects as the light-emitting device described in the previous embodiment, the technical effects of the preparation method will not be repeatedly described here for the purpose of brevity.

[0137] The present disclosure also provides a display panel. As shown in FIG12 , the display panel includes a substrate 10 and a plurality of light-emitting devices 00 as shown in any one of FIG1 to FIG8 located on one side of the substrate 10 .

[0138] Optionally, the substrate 10 may be a flexible substrate or a non-flexible substrate (eg, a glass substrate).

[0139] Optionally, as previously described, the light-emitting device 00 may be a white organic electroluminescent device (WOLED). Furthermore, as shown in FIG13 , the display panel described in the embodiment of the present disclosure may further include a color filter (CF) located on the side of the light-emitting device 00 away from the substrate. The color filter CF can filter the white light emitted by the WOLED into colored light, enabling the display panel to display a color image.

[0140] The present disclosure also provides a display device. As shown in FIG14 , the display device includes a driving circuit 100 and a display panel 000 as shown in FIG12 or FIG13 .

[0141] The driving circuit 100 is connected to the light emitting device 00 in the display panel 000 and is used to drive the light emitting device 00 to emit light. For example, the driving circuit 100 can transmit a light driving signal to the light emitting device 00, thereby driving the light emitting device 00 to emit light.

[0142] It can be understood that FIG. 14 schematically illustrates only one light-emitting device 00 on the display panel 000 , and does not illustrate the connection between the driving circuit 100 and the light-emitting device 00 .

[0143] It should be understood that the terms used in the embodiments of the present disclosure are used to explain the embodiments of the present disclosure and are not intended to limit the present disclosure. Unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present disclosure should have the common meanings understood by people with ordinary skills in the field to which the present disclosure belongs.

[0144] For example, in the embodiments of the present disclosure, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance. The term "plurality" refers to two or more, unless expressly limited otherwise. Similarly, "one" or "an" and other similar words do not indicate a quantity limitation, but rather indicate the presence of at least one. "Include" or "comprising" and other similar words mean that the elements or objects appearing before "include" or "comprising" cover the elements or objects listed after "include" or "comprising" and their equivalents, and do not exclude other elements or objects. "Up", "down", "left" or "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0145] The above description is merely an optional embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.

Claims

1. A light-emitting device, comprising: A first electrode, a light-emitting layer of a first color, and a second electrode are sequentially stacked; The light-emitting layer of the first color includes: a first host layer and a second host layer stacked in sequence; Wherein, the first host layer comprises a first host material and a first guest material; the second host layer comprises a second host material and a second guest material; Furthermore, the first host material is an electron transport material or a hole transport material, the second host material is a mixed transport material, the proportion of holes in the mixed transport material is less than the proportion of electrons; the first guest material has the luminescence characteristics of a first spectrum, the second guest material has the luminescence characteristics of a second spectrum, and the widths of the first spectrum and the second spectrum are different; the thickness of the second host layer is greater than the thickness of the first host layer.

2. The light emitting device according to claim 1, wherein The first host material is the electron transport material, and the width of the first spectrum is smaller than the width of the second spectrum.

3. The light emitting device according to claim 1, wherein The first host material is the hole transport material, and the width of the first spectrum is greater than the width of the second spectrum.

4. The light emitting device according to any one of claims 1 to 3, wherein: The ratio of holes to electrons in the mixed transport material satisfies the ratio of 3:

7.

5. The light emitting device according to any one of claims 1 to 4, wherein: The thickness of the second main layer is greater than 100 nanometers.

6. The light emitting device according to any one of claims 1 to 5, wherein: The light emitting device further comprises: an intermediate layer located between the first body layer and the second body layer; Moreover, the material of the intermediate layer is the hole transport material or the electron transport material, and the material of the intermediate layer is the same as the first main material; the thickness of the intermediate layer is less than the thickness of the first main layer, and the thickness of the intermediate layer is less than the thickness of the second main layer.

7. The light emitting device according to claim 6, wherein The thickness of the intermediate layer is between 4 nanometers and 6 nanometers.

8. The light emitting device according to any one of claims 1 to 7, wherein: The first color light-emitting layer further includes: a third main body layer; the first main body layer, the second main body layer and the third main body layer are stacked in sequence; wherein the third host layer comprises a third host material and the second guest material; Furthermore, the third host material is the electron transport material or the hole transport material, and the third host material is different from the first host material; and the thickness of the second host layer is smaller than that of the third host layer.

9. The light emitting device according to any one of claims 1 to 8, wherein: The first guest material and the second guest material both include fluorescent materials.

10. The light emitting device according to any one of claims 1 to 9, wherein: The light emitting device further comprises: a hole injection layer, a hole transport layer, and an electron blocking layer located between the first electrode and the light-emitting layer of the first color and stacked in sequence in a direction away from the first electrode; An electron injection layer, an electron transport layer, and a hole blocking layer are located between the second electrode and the light-emitting layer of the first color and are sequentially stacked in a direction away from the second electrode. The light emitting device according to claim 10 , wherein: The first host layer and the second host layer, wherein the first host material is an electron transport material, are sequentially stacked in a direction away from the second electrode; The first host layer and the second host layer, in which the first host material is a hole transport material, are sequentially stacked in a direction away from the first electrode.

12. The light emitting device according to any one of claims 1 to 11, wherein: The light emitting device further includes: a light emitting layer of a second color and a light emitting layer of a third color, which are located between the first electrode and the second electrode and are sequentially stacked; The first color is blue, the second color is red, and the third color is green.

13. The light emitting device according to any one of claims 1 to 12, wherein: The first electrode is an anode, and the second electrode is a cathode; Furthermore, the material of the first electrode includes a transparent conductive material; and the material of the second electrode includes a metal material. The light emitting device according to claim 13 , wherein: The transparent conductive material includes: indium tin oxide material.

15. A method for preparing a light-emitting device, for preparing the light-emitting device according to any one of claims 1 to 14, the method comprising: forming a first electrode; forming a first host layer on one side of the first electrode using a first host material and a first guest material doped in the first host material; forming a second host layer on one side of the first host layer using a second host material and a second guest material doped in the second host material to obtain a light-emitting layer of a first color; forming a second electrode on a side of the light-emitting layer of the first color away from the first electrode; The first host material is an electron transport material or a hole transport material, and the second host material is a mixed transport material, wherein the hole ratio in the mixed transport material is smaller than the electron ratio; the first guest material has a luminescence characteristic of a first spectrum, and the second guest material has a luminescence characteristic of a second spectrum, and the widths of the first spectrum and the second spectrum are different; Furthermore, the thickness of the second main body layer is greater than the thickness of the first main body layer.

16. The method according to claim 15, wherein Before forming the second electrode, the method further includes: forming an intermediate layer between the first main layer and the second main layer using the hole transport material or the electron transport material; The material used to form the intermediate layer is the same as the first main body material; and the thickness of the intermediate layer is smaller than the thickness of the first main body layer. The thickness of the second main layer is formed.

17. The method according to claim 15, wherein: After forming the second body layer, the method further includes: forming a third host layer on a side of the second host layer away from the first host layer using a third host material and the second guest material doped in the third host material to obtain a light-emitting layer of the first color; The third main material is the electron transport material or the hole transport material, and the third main material is the same as the first main material; and the thickness of the formed second main layer is smaller than the thickness of the formed third main layer.

18. A display panel, comprising: A substrate, and a plurality of light-emitting devices according to any one of claims 1 to 14 located on one side of the substrate.

19. The display panel according to claim 18, wherein: The light emitting device is a white organic electroluminescent device; the display panel further comprises a color filter located on a side of the light emitting device away from the substrate.

20. A display device, comprising: A driving circuit, and a display panel as claimed in claim 18 or 19; The driving circuit is connected to the light-emitting device in the display panel and is used to drive the light-emitting device to emit light.

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