Pixel unit of display substrate, manufacturing method and display panel

Abstract

The present disclosure provides a pixel unit of a display substrate, a manufacturing method, and a display panel, which relate to the field of display technology. The pixel unit used in the display substrate includes a first electrode; a second electrode; and at least one organic electroluminescent unit stacked between the first electrode and the second electrode. The organic electroluminescent unit includes a light-emitting layer, the light-emitting layer includes a host material and a guest material as a dopant. The host material includes a phosphorescent-doped electron-type host material and a phosphorescent-doped hole-type host material. The guest material includes a first dopant and a second dopant, and the HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant. The pixel unit provided by the present disclosure can make the electron-hole transmission of the pixel unit more balanced, improve the efficiency roll-off of the phosphorescent-doped pixel unit at high current density, and significantly improve the life of the pixel unit.

Description

Technical Field

[0001] The present disclosure relates to the field of display technology, and in particular to a pixel unit of a display substrate, a manufacturing method thereof, and a display panel. Background Art

[0002] OLED (Organic Light-Emitting Diode) devices have many advantages such as full solid-state, active luminescence, high contrast, ultra-thin, low power consumption, no viewing angle limitation, fast response speed, wide operating temperature range, easy to achieve flexibility and large area, low power consumption, etc. They are often used as display devices. However, when used as display devices, the efficiency of the display device rolls off during use due to the imbalance of carrier transmission inside the display device, which reduces the service life of the display device. Summary of the Invention

[0003] Based on the background technology, the present disclosure proposes a driving system, method and terminal for a display device to solve the above problems.

[0004] In a first aspect of the present disclosure, a pixel unit of a display substrate is provided, comprising:

[0005] a first electrode;

[0006] a second electrode; and

[0007] at least one organic electroluminescent unit, stacked between the first electrode and the second electrode, the organic electroluminescent unit comprising a light-emitting layer, the light-emitting layer comprising a host material and a guest material as a dopant;

[0008] In which, the HOMO energy level of the host material is lower than the HOMO energy level of the guest material, and the energy level difference between the HOMO energy level of the host material and the HOMO energy level of the guest material is greater than 0.15 eV; the host material includes a phosphorescent-doped electron-type host material and a phosphorescent-doped hole-type host material, and the guest material includes a first dopant and a second dopant, the HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2 eV.

[0009] Furthermore, the spectral difference between the first dopant and the second dopant is less than 1 nm.

[0010] Furthermore, the light-emitting layer includes a first light-emitting sublayer and a second light-emitting sublayer stacked together;

[0011] Wherein, the host material of the first luminescent sublayer is the same as the host material of the second luminescent sublayer;

[0012] The first light-emitting sublayer includes the first dopant, and the second light-emitting sublayer includes the second dopant.

[0013] Furthermore, the first electrode is a cathode, and the second electrode is an anode;

[0014] The first light-emitting sublayer is disposed close to the cathode, and the second light-emitting sublayer is disposed close to the anode.

[0015] Furthermore, the first electrode is a cathode, the second electrode is an anode, the first light-emitting sublayer is arranged close to the anode, and the second light-emitting sublayer is arranged close to the cathode.

[0016] Furthermore, a plurality of the organic electroluminescent units are stacked in sequence, and a charge generation layer is stacked between every two adjacent organic electroluminescent units;

[0017] Among the plurality of organic electroluminescent units, there is at least one first organic electroluminescent unit, and the light-emitting layer in the first organic electroluminescent unit includes the first light-emitting sublayer and the second light-emitting sublayer.

[0018] Furthermore, the first electrode is a cathode, the second electrode is an anode, and there are a plurality of the first organic electroluminescent units;

[0019] Among the two first organic electroluminescent units, the first luminescent sublayer in one of the first organic electroluminescent units is arranged close to the cathode, and the first luminescent sublayer in the other of the first organic electroluminescent units is arranged close to the anode.

[0020] Furthermore, there is a second organic electroluminescent unit among the plurality of organic electroluminescent units, and the second organic electroluminescent unit includes a single-layer third light-emitting sublayer;

[0021] The third light-emitting sublayer includes the first dopant and the second dopant, and the thickness of the third light-emitting sublayer is greater than the thickness of the first light-emitting sublayer and greater than the thickness of the second light-emitting sublayer.

[0022] Furthermore, the first dopant includes an iridium complex or a platinum complex, and the second dopant includes an iridium complex or a platinum complex.

[0023] Furthermore, the phosphorescent-doped electronic host material includes at least one of triazine, pyrazine, pyridine, quinoline, and o-phenanthroline derivatives.

[0024] Furthermore, the phosphorescent-doped hole-type host material includes a derivative of triphenylamine or carbazole.

[0025] In a second aspect of the present disclosure, a method for manufacturing a pixel unit of a display substrate is provided, the method comprising:

[0026] forming a first electrode;

[0027] forming at least one organic electroluminescent unit on the first electrode in sequence, wherein the organic electroluminescent unit includes a light-emitting layer, and the light-emitting layer includes a host material and a guest material as a dopant;

[0028] forming a second electrode on a side of the organic electroluminescent unit away from the first electrode;

[0029] In which, the host material includes a phosphorescent-doped electron-type host material and a phosphorescent-doped hole-type host material, the guest material includes a first dopant and a second dopant, the HOMO energy level of the host material is lower than the HOMO energy level of the guest material, and the energy level difference between the HOMO energy level of the host material and the HOMO energy level of the guest material is greater than 0.15eV; the HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2eV.

[0030] Furthermore, the step of sequentially forming at least one organic electroluminescent unit on the first electrode layer includes:

[0031] forming a hole injection layer, a hole transport layer and an electron blocking layer in sequence on the first electrode;

[0032] Filling the electron blocking layer with the host material and the target dopant, and forming a first light-emitting sublayer at a corresponding evaporation rate; wherein the target dopant is the first dopant or the second dopant;

[0033] Filling the host material and the dopant in the guest material except the target dopant on the electron blocking layer, and forming a second light-emitting sublayer at a corresponding evaporation rate;

[0034] forming a hole blocking layer, an electron transport layer and an electron injection layer in sequence on a side of the second light-emitting sublayer facing away from the first electrode;

[0035] The evaporation rate of the host material is higher than the evaporation rate of the guest material.

[0036] According to a third aspect of the present disclosure, a display panel is provided, comprising a display substrate, wherein the display substrate comprises any pixel unit described in the first aspect of the present disclosure.

[0037] A pixel unit using the display substrate disclosed herein includes: a first electrode; a second electrode; and at least one organic electroluminescent unit stacked between the first electrode and the second electrode, wherein the organic electroluminescent unit includes a light-emitting layer, which includes a host material and a guest material as a dopant.

[0038] Among them, the HOMO energy level of the host material is lower than the HOMO energy level of the guest material, and the energy level difference between the HOMO energy level of the host material and the HOMO energy level of the guest material is greater than 0.15eV; the host material includes a phosphorescent-doped electron-type host material and a phosphorescent-doped hole-type host material, the guest material includes a first dopant and a second dopant, the HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2eV.

[0039] Since the pixel unit disclosed herein includes at least one organic electroluminescent unit, the light-emitting layer in the organic electroluminescent unit includes a host material and a guest material as a dopant, and the HOMO energy level of the host material is lower than the HOMO energy level of the guest material, and the energy level difference between the HOMO energy level of the host material and the HOMO energy level of the guest material is greater than 0.15 eV, the guest material includes a first dopant and a second dopant, the HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2 eV, in this combination structure, the electron-hole transmission in the light-emitting layer is more balanced, the exciton recombination center of the device moves toward the center of the light-emitting layer, the efficiency roll-off of the phosphorescent-doped pixel unit at high current density is improved, the life of the pixel unit is significantly improved, the device efficiency roll-off is significantly reduced, and the device life is significantly improved.

[0040] The above description is only an overview of the technical solution of the present disclosure. In order to more clearly understand the technical means of the present disclosure, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present disclosure more obvious and easy to understand, the specific implementation methods of the present disclosure are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or related technologies, the following is a brief introduction to the drawings required for the description of the embodiments or related technologies. Obviously, the drawings described below are some embodiments of the present disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without inventive efforts. It should be noted that the scales in the drawings are for illustration only and do not represent the actual scale.

[0042] Figure 1A schematic diagram showing a pixel unit of a display substrate in an embodiment of the present disclosure is shown;

[0043] Figure 2 A schematic diagram of a pixel unit in implementation mode 1 according to an embodiment of the present disclosure is shown;

[0044] Figure 3 Shown Figure 1 A schematic structural diagram of a pixel unit under implementation mode 1a;

[0045] Figure 4 Shown Figure 1 A schematic structural diagram of a pixel unit under implementation mode 1b;

[0046] Figure 5 A schematic diagram of a pixel unit in implementation mode 2 in an embodiment of the present disclosure is shown;

[0047] Figure 6 Shown Figure 5 A schematic structural diagram of a pixel unit under implementation method 2;

[0048] Figure 7 A schematic diagram of a pixel unit in implementation mode 3 in an embodiment of the present disclosure is shown;

[0049] Figure 8 Shown Figure 7 A schematic structural diagram of a pixel unit under implementation method 3;

[0050] Figure 9 A schematic structural diagram of a pixel unit according to Example 1 of the embodiment of the present disclosure is shown;

[0051] Figure 10 A schematic structural diagram of a pixel unit according to Example 2 of an embodiment of the present disclosure is shown;

[0052] Figure 11 A schematic structural diagram of a pixel unit according to Example 3 of the embodiment of the present disclosure is shown;

[0053] Figure 12 A schematic diagram showing the HOMO energy level of the light-emitting layer in an embodiment of the present disclosure;

[0054] Figure 13 A schematic diagram showing the HOMO energy level of a light-emitting layer in the related art;

[0055] Figure 14 Shown Figure 12 and Figure 13 Schematic diagram of the current and voltage curve;

[0056] Figure 15 Shown Figure 12 and Figure 13 Schematic diagram of the efficiency brightness curve;

[0057] Figure 16 A flowchart showing the steps of a method for manufacturing a pixel unit of a display substrate in an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0058] To make the above-mentioned purposes, features, and advantages of the present disclosure more clearly understood, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present disclosure without creative work are within the scope of protection of the present disclosure.

[0059] In related technologies, OLED devices can be used as both display and lighting devices. OLEDs can be divided into two types based on pixel units: single-layer OLED devices and stacked OLED devices. Stacked OLED devices have two or more pixel units connected in series via a charge generation layer. Compared to single-layer OLEDs, stacked OLEDs have the following advantages:

[0060] Driven by the same current density, the luminance of the stacked OLED is n times that of a single-layer OLED composed of a single pixel unit, so the current efficiency of the stacked OLED is n times that of a single-layer OLED.

[0061] Secondly, OLED displays and lighting devices operate at a certain brightness. Under the same luminous brightness, the current density driving the stacked OLED is 1 / n of the current density of the single-layer OLED. The greater the current density of the OLED, the faster it ages and the shorter the device life. Therefore, the life of the stacked OLED will be greatly extended.

[0062] Furthermore, depending on the luminescent material, OLEDs can be categorized as fluorescent and phosphorescent. Fluorescent devices can only utilize 25% of the energy of singlet excitons generated by electrical excitation, resulting in a maximum internal quantum efficiency of 25%. External quantum efficiencies are generally less than 5%, significantly lower than the efficiency of phosphorescent devices.

[0063] Because phosphorescent materials can utilize both singlet and triplet energy, the theoretical internal quantum efficiency of phosphorescent OLEDs can reach 100%. However, most phosphorescent devices exhibit significant efficiency roll-off at high current densities, meaning their efficiency gradually decreases as the operating current increases. This is due to unbalanced carrier transport within the device, which results in the concentration of exciton luminescence centers between the luminescent layer and the functional layer. At high current densities, the high exciton concentration at the luminescent center easily produces TTA (triplet-triplet annihilation) and TPA (exciton-polaron annihilation), which increase the non-radiative transitions of excitons, leading to a decrease in the efficiency roll-off of the display device and a shortened display device lifespan.

[0064] In view of this, in order to solve the problem of unbalanced carrier transmission in OLED devices, the present disclosure provides a pixel unit of a display substrate, a manufacturing method and a display panel, which respectively solve the problem of unbalanced electron and hole transmission capabilities of the host material and the trapping effect of the guest material on electrons or holes, resulting in obstructed electron or hole transmission and the resulting efficiency roll-off of the display device from the structure and material of the pixel unit of the display substrate.

[0065] Reference Figure 1 , Figure 1 A schematic diagram of a pixel unit of a display substrate in an embodiment of the present disclosure is shown; Figure 1 It can be seen that the pixel unit of the display substrate of the present disclosure includes: a first electrode, a second electrode, and at least one organic electroluminescent unit stacked between the first electrode and the second electrode, the organic electroluminescent unit including a light-emitting layer, the light-emitting layer including a host material and a guest material as a dopant;

[0066] Among them, the HOMO energy level of the host material is lower than the HOMO energy level of the guest material, and the energy level difference between the HOMO energy level of the host material and the HOMO energy level of the guest material is greater than 0.15eV; the host material includes a phosphorescent-doped electron-type host material and a phosphorescent-doped hole-type host material, the guest material includes a first dopant and a second dopant, the HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2eV.

[0067] In this embodiment, the display substrate is a main component of the display device, wherein the pixel units in the display substrate are used to emit light, so that a plurality of pixel units emit light to generate corresponding images.

[0068] The organic electroluminescent unit in the pixel unit can be a light-emitting device that converts electrical energy into light energy. Specifically, by connecting the anode in the pixel unit to the corresponding driving circuit, the organic electroluminescent unit can be driven to emit light to display the corresponding display screen. The luminous efficiency and life of the light-emitting device can be directly restricted by the device structure and materials.

[0069] In this embodiment, the pixel unit includes: a first electrode, a second electrode, and at least one organic electroluminescent unit, and the organic electroluminescent unit is stacked between the first electrode and the second electrode. The stacking means that multiple organic electroluminescent units can be overlapped between the first electrode and the second electrode.

[0070] In this embodiment, the first electrode and the second electrode are electrodes with opposite polarities. For example, if the first electrode is an anode, the second electrode is a cathode, or if the first electrode is a cathode, the second electrode is an anode. This is not limited in this embodiment.

[0071] An organic electroluminescent unit is a current-type semiconductor light-emitting device that can be driven by current, and a pixel unit includes at least one organic electroluminescent unit, which is stacked between a first electrode and a second electrode. Therefore, the corresponding light-emitting function can be achieved by changing the number of organic electroluminescent units stacked between the first electrode and the second electrode.

[0072] In addition, the organic electroluminescent unit includes a light-emitting layer, which includes a host material and a guest material as a dopant. By changing the material constituting the light-emitting layer, the material type of the light-emitting layer in the organic electroluminescent unit can be changed, thereby changing the efficiency roll-off and life of the pixel unit.

[0073] The host material has a lower HOMO energy level than the guest material, and the energy difference between the host material's HOMO energy level and the guest material's HOMO energy level is greater than 0.15 eV. The HOMO energy level refers to the energy level occupied by the highest-energy filled electron or hole in a molecular orbital. Therefore, the host material has a higher triplet energy level than the guest material, ensuring that the first dopant and the second dopant promote the transfer of electrons and holes between the host and guest materials, preventing carriers from being confined in the guest material, which slows electron-hole transport. A hole refers to an unfilled orbital left in the electronic structure due to the transition of an atomic valence electron to the conduction band, where the charge is equivalent to a positively charged carrier. In some examples, the host material includes a phosphorescent-doped electron-type host material and a phosphorescent-doped hole-type host material. In this embodiment, the phosphorescent-doped hole-type host material and the phosphorescent-doped electron-type host material can form an exciplex in a mixing ratio of 6:4.

[0074] The guest material includes a first dopant and a second dopant. In this embodiment, the doping ratio of the guest material may be 4%. For example, the doping ratio of the first dopant and the doping ratio of the second dopant may be the same, both 4%. Of course, in other examples, the doping ratio of the first dopant and the doping ratio of the second dopant may be different.

[0075] The HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2 eV. In some examples, the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant can be greater than 0.2 eV and can be less than 0.3 eV or 0.4 eV, and can be selected based on the characteristics of the actual material.

[0076] The pixel unit of a display substrate provided by the present disclosure is applied in a display device. By changing the structure of the pixel unit and limiting the HOMO energy levels and material types of the host material and guest material of the organic electroluminescent unit in the pixel unit, electron transmission and hole transmission in the display device can be made more balanced, the efficiency roll-off of the phosphorescent-doped pixel unit at high current density can be improved, and the life of the pixel unit in the display component can be significantly improved.

[0077] In one embodiment, the spectral difference between the first dopant and the second dopant is less than 1 nm and greater than 0.

[0078] In this embodiment, in order to shorten the gap between the first dopant and the second dopant, ensure that the first dopant and the second dopant promote the transfer of electrons and holes between the host material and the guest material, and prevent the carriers from being confined in the guest material, the spectral difference between the first dopant and the second dopant is less than 1 nm.

[0079] In a specific embodiment, since at least one organic electroluminescent unit is present between the first electrode and the second electrode, various pixel unit structures are provided to improve the efficiency roll-off and lifespan of the display device. Implementation 1 employs a single organic electroluminescent unit in the pixel unit, while Implementation 2 employs two or more organic electroluminescent units in the pixel unit. OLED devices with such structures can be referred to as tandem OLED devices. For details, please refer to the descriptions of Implementations 1 and 2.

[0080] The following describes implementation method 1:

[0081] In implementation method 1, the light-emitting layer includes a stacked first light-emitting sublayer and a second light-emitting sublayer; wherein the main material of the first light-emitting sublayer is the same as the main material of the second light-emitting sublayer; the first light-emitting sublayer includes a first dopant, and the second light-emitting sublayer includes a second dopant.

[0082] In this embodiment, the light-emitting layer includes a stacked first light-emitting sublayer and a second light-emitting sublayer, that is, the light-emitting layer of the organic electroluminescent unit can include two light-emitting sublayers. Compared with the case where there is only one light-emitting sublayer, the structure of the two light-emitting sublayers can make the electron transmission and hole transmission of the light-emitting layer more balanced, and the luminous brightness will be higher. At the same time, the film quality of the light-emitting layer can be guaranteed. For example, after preparing a light-emitting sublayer, if it is found that the film thickness of the light-emitting sublayer does not meet the requirements, it can be compensated by manufacturing another light-emitting sublayer.

[0083] This embodiment does not limit the stacking position of the first light-emitting sublayer and the second light-emitting sublayer. For example, the first light-emitting sublayer is stacked close to the first electrode, or the second light-emitting sublayer is stacked close to the first electrode.

[0084] In this embodiment, the main material of the first luminescent sublayer is the same as the main material of the second luminescent sublayer, and the guest materials included in the first luminescent sublayer and the second luminescent sublayer are different. For example, the first luminescent sublayer includes a first dopant, and the second luminescent sublayer includes a second dopant. The HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2 eV, which can promote the transfer of electrons and holes between the host and the guest, prevent the carriers from being confined in the guest, and make the electron-hole transmission in the luminescent layer more balanced.

[0085] In some examples, when two light-emitting sublayers are included, the doping ratios of the guest materials corresponding to the two light-emitting sublayers can be the same or different.

[0086] For example, the process of the light-emitting layer emitting light in implementation manner 1 is described below with a specific example.

[0087] Since the pixel unit is generally composed of a cathode (Cathode), an electron injection layer (EIL), an electron transport layer (ETL), a hole blocking layer (HBL), an emitting layer (EML), an electron blocking layer (Prime) a hole transport layer (HTL), a hole injection layer (HIL) and an anode (ITO).

[0088] The light-emitting layer is a light-emitting film structure of an organic electroluminescent unit, and the light-emitting layer includes a first light-emitting sublayer and a second light-emitting sublayer. Implementation method 1a is described below:

[0089] In implementation manner 1a, the first electrode of the pixel unit is a cathode, and the second electrode is an anode; the first light-emitting sublayer is arranged close to the cathode, and the second light-emitting sublayer is arranged close to the anode.

[0090] In this embodiment, the first electrode of the light-emitting layer is a cathode and the second electrode is an anode. Since the first light-emitting sublayer and the second light-emitting sublayer are stacked between the first electrode and the second electrode, and because the first light-emitting sublayer is arranged close to the cathode and the second light-emitting sublayer is arranged close to the anode, it can promote the transfer of electrons and holes between the host and the object, prevent the carriers from being confined in the object, and make the electron-hole transmission in the light-emitting layer more balanced.

[0091] For example, refer to Figure 3 , Figure 3 Shown Figure 1 The structural diagram of the pixel unit under the implementation method 1a, from Figure 3 It can be seen that the gray areas in the figure are the first luminescent sublayer and the second luminescent sublayer respectively. The first luminescent sublayer includes the first dopant, and the second luminescent sublayer includes the second dopant. The first luminescent sublayer is arranged close to the cathode, and the second luminescent sublayer is arranged close to the anode.

[0092] Implementation method 1b is described as follows:

[0093] In implementation manner 1b, the first electrode of the pixel unit is a cathode, the second electrode is an anode, the first light-emitting sublayer is arranged close to the anode, and the second light-emitting sublayer is arranged close to the cathode.

[0094] In this embodiment, the first electrode of the light-emitting layer is a cathode and the second electrode is an anode. Since the first light-emitting sublayer and the second light-emitting sublayer are stacked between the first electrode and the second electrode, and because the first light-emitting sublayer is arranged close to the anode and the second light-emitting sublayer is arranged close to the cathode, it can also promote the transfer of electrons and holes between the host and the object, prevent the carriers from being confined in the object, and make the electron-hole transmission in the light-emitting layer more balanced.

[0095] For example, refer to Figure 4 , Figure 4 Shown Figure 1 The structural diagram of the pixel unit under the implementation method 1b is as follows: Figure 4 It can be seen that the gray areas in the figure are the first luminescent sublayer and the second luminescent sublayer, respectively. The first luminescent sublayer includes the first dopant, and the second luminescent sublayer includes the second dopant. The first luminescent sublayer is arranged close to the anode, and the second luminescent sublayer is arranged close to the cathode.

[0096] The following describes implementation method 2:

[0097] In implementation method 2, the pixel unit includes a plurality of organic electroluminescent units stacked in sequence, and a charge generation layer is stacked between every two adjacent organic electroluminescent units; wherein, there is at least one first organic electroluminescent unit among the plurality of organic electroluminescent units, and the light-emitting layer in the first organic electroluminescent unit includes a first light-emitting sublayer and a second light-emitting sublayer.

[0098] In this embodiment, the pixel unit includes a plurality of organic electroluminescent units stacked in sequence. The plurality of organic electroluminescent units can enable the basic pixel unit of the display to have a lower driving voltage at the same luminous brightness. A charge generation layer is stacked between each two adjacent organic electroluminescent units, and the charge transfer between the two organic electroluminescent units is realized through the charge generation layer. In this embodiment, the charge generation layer includes a P-type charge generation layer PCGL and an N-type charge generation layer NCGL.

[0099] In addition, different materials can be used in the multiple organic electroluminescent units in the pixel unit, so the pixel unit can be improved in structure and material at the same time to achieve corresponding luminous functions.

[0100] In this example, there is at least one first organic electroluminescent unit among the plurality of organic electroluminescent units. For example, there may be a first organic electroluminescent unit, or there may be a plurality of first organic electroluminescent units.

[0101] Wherein, when there is one first organic electroluminescent unit, the first organic electroluminescent unit is the organic electroluminescent unit closest to the cathode, or may be the organic electroluminescent unit closest to the anode. When there are multiple first organic electroluminescent units, all organic electroluminescent units in the pixel unit may be first organic electroluminescent units, or some organic electroluminescent units may be first organic electroluminescent units.

[0102] Reference Figure 5 , Figure 5 FIG2 shows a schematic diagram of a pixel unit in implementation mode 2 according to an embodiment of the present disclosure. Figure 5 The method comprises two organic electroluminescent units stacked in sequence, wherein one of the organic electroluminescent units is a first organic electroluminescent unit, i.e., it includes a first luminescent sublayer and a second luminescent sublayer, and the other organic electroluminescent unit except the first organic electroluminescent unit includes only one luminescent layer, which may include a host material and a guest material, and the guest material may be a first dopant and a second dopant.

[0103] Wherein, in the case of including a plurality of first organic electroluminescent units, the light-emitting layers in all organic electroluminescent units in the pixel unit may include a first light-emitting sublayer and a second light-emitting sublayer, and further reference is made to Figure 5 , including two organic electroluminescent units, both of which are first organic electroluminescent units.

[0104] Of course, in some examples, the stacking of film layers in the light-emitting layer of different first organic electroluminescent units may vary slightly. For example, although all include two light-emitting sublayers, the relative positional relationship between the two light-emitting sublayers may vary slightly in different first organic electroluminescent units, as will be described in subsequent embodiments.

[0105] For example, in the two first organic electroluminescent units, the first light-emitting sublayer in one first organic electroluminescent unit is disposed close to the cathode, and the first light-emitting sublayer in the other first organic electroluminescent unit is disposed close to the anode.

[0106] For example, the first light-emitting sublayer in the first organic electroluminescent unit close to the cathode is arranged close to the cathode, and the first light-emitting sublayer in the first organic electroluminescent unit close to the anode can be arranged close to the anode. Alternatively, the first light-emitting sublayer in the first organic electroluminescent unit close to the cathode is arranged close to the anode, and the first light-emitting sublayer in the first organic electroluminescent unit close to the anode is arranged close to the cathode.

[0107] In implementation method 2, if the first electrode in the pixel unit is a cathode, the second electrode is an anode, and there are multiple first organic electroluminescent units; wherein, among the multiple first organic electroluminescent units, the first luminescent sublayer in the first organic electroluminescent unit close to the cathode is arranged close to the cathode, and the first luminescent sublayer in the first organic electroluminescent unit close to the anode is arranged close to the anode.

[0108] In this embodiment, referring to Figure 6 , Figure 6 , Figure 6 Shown Figure 5 Schematic diagram of the structure of the pixel unit under the implementation method 2; Figure 6 It can be seen that two first organic electroluminescent units are included, the gray area in the first organic electroluminescent unit in the figure is the light-emitting layer, the light-emitting layer includes a first light-emitting sublayer and a second light-emitting sublayer, the first electrode in the pixel unit is a cathode, and the second electrode is an anode; wherein, among the multiple first organic electroluminescent units, the first light-emitting sublayer in the first organic electroluminescent unit close to the cathode is arranged close to the cathode, and the first light-emitting sublayer in the first organic electroluminescent unit close to the anode is arranged close to the anode.

[0109] Of course, in some other examples, the film layers of the light-emitting layers of different first organic electroluminescent units are stacked in the same manner, the first light-emitting sublayers are all arranged close to the cathode, and the second light-emitting sublayers are all arranged close to the anode, or the first light-emitting sublayers are all arranged close to the anode, and the second light-emitting sublayers are all arranged close to the cathode.

[0110] In summary, the structures of one organic electroluminescent unit and two or more organic electroluminescent units in a pixel unit are described. This structure can improve the efficiency roll-off of the phosphorescent-doped pixel unit at high current density and significantly improve the life of the pixel unit.

[0111] The following describes implementation method 3:

[0112] In implementation method 3, there is a second organic electroluminescent unit among the multiple organic electroluminescent units in the pixel unit, and the second organic electroluminescent unit includes a single-layer third light-emitting sublayer; wherein the third light-emitting sublayer includes a first dopant and a second dopant, and the thickness of the third light-emitting sublayer is greater than the thickness of the first light-emitting sublayer and greater than the thickness of the second light-emitting sublayer.

[0113] In this embodiment, due to the space limitation of the display substrate, the pixel unit may include a single-layer organic electroluminescent unit, some of which are first organic electroluminescent units, and the remaining organic electroluminescent units are second organic electroluminescent units. In this embodiment, the single-layer luminescent layer included in the second organic electroluminescent unit is called the third luminescent sublayer. Figure 7 , Figure 7 A schematic diagram of a pixel unit in implementation mode 3 in an embodiment of the present disclosure is shown; Figure 7 It can be seen that there is a second organic electroluminescent unit in the plurality of organic electroluminescent units, and the second organic electroluminescent unit includes a single-layer third light-emitting sublayer.

[0114] The third light-emitting sublayer includes the first dopant and the second dopant, and the thickness of the third light-emitting sublayer is greater than the thickness of the first light-emitting sublayer and greater than the thickness of the second light-emitting sublayer.

[0115] In this example, the thickness of the third light-emitting sublayer may be equal to the sum of the thicknesses of the first light-emitting sublayer and the second light-emitting sublayer.

[0116] By adopting this structure, the problem of efficiency roll-off of phosphorescent devices at high current density can be effectively improved. Combined with adjusting the thickness of the third luminescent sublayer, it can also achieve the same effect as the first and second luminescent sublayers, that is, promoting the transfer of electrons and holes between the host and the guest, preventing carriers from being confined in the guest, and making the electron-hole transmission in the luminescent layer more balanced.

[0117] In some other embodiments, the pixel unit may be a structure of a single organic electroluminescent unit, that is, it only includes one organic electroluminescent unit, and the light-emitting layer in the organic electroluminescent unit in the pixel unit may include a host material and a guest material, and the guest material may include a first dopant and a second dopant.

[0118] Reference Figure 8 , refer to Figure 8 , Figure 8 shows a structural schematic diagram of another pixel unit; Figure 8 Only a single organic electroluminescent unit is used for illustration. Figure 8 The light-emitting layer in the method can still be called the third light-emitting sublayer, which includes the first dopant and the second dopant, and the HOMO energy level of the host material is lower than the HOMO energy level of the guest material, and the energy level difference between the HOMO energy level of the host material and the HOMO energy level of the guest material is greater than 0.15eV; the host material includes a phosphorescent-doped electron-type host material and a phosphorescent-doped hole-type host material, and the guest material includes the first dopant and the second dopant, the HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2eV.

[0119] For this structure, the problem of efficiency roll-off of phosphorescent devices at high current density can still be effectively improved.

[0120] In some embodiments, the first dopant includes an iridium complex or a platinum complex, and the second dopant includes an iridium complex or a platinum complex.

[0121] In this embodiment, since iridium and platinum have excellent luminescence properties, long phosphorescence lifetime and good thermal stability, the first dopant may include an iridium complex or a platinum complex, and the second dopant may include an iridium complex or a platinum complex.

[0122] Among them, the first dopant and the second dopant can both be iridium complexes, or both can be platinum complexes, or the first dopant is an iridium complex and the second dopant is a platinum complex; or the first dopant is a platinum complex and the second dopant is an iridium complex.

[0123] In one embodiment, the phosphorescent-doped electronic host material includes at least one of triazine, pyrazine, pyridine, quinoline, and o-phenanthroline derivatives.

[0124] In this embodiment, in order to utilize the singlet and triplet energy in phosphorescence, the electronic host material for phosphorescence doping may include at least one of triazine, pyrazine, pyridine, quinoline, and o-phenanthroline derivatives.

[0125] In one embodiment, the phosphorescent-doped hole-type host material includes a derivative of triphenylamine or carbazole.

[0126] In this embodiment, in order to make the electron-hole transport in the light-emitting layer more balanced, the phosphorescent-doped hole-type host material may include a derivative of triphenylamine or carbazole.

[0127] For example, the following will be described in detail using one of the methods provided by the present disclosure as an example:

[0128] Example 1

[0129] First refer to Figure 9 , Figure 9 A schematic structural diagram of a pixel unit of Example 1 in an embodiment of the present disclosure is shown.

[0130] Figure 9 The structure and thickness of the pixel unit from top to bottom are: cathode (Cathode) 13nm, electron transport layer (ETL) 30nm, hole blocking layer (HBL) 5nm, third light-emitting layer (EML) 40nm, electron blocking layer (Prime) 50nm, hole transport layer (HTL) 20nm, hole injection layer (HIL) 11nm, P-type charge generation layer (PCGL), N-type charge generation layer (NCGL), hole blocking layer (HBL) 30nm, third light-emitting sublayer (EML) 40nm, electron blocking layer (Prime) 50nm, hole transport layer (HTL) 110nm, hole injection layer (HIL) 11nm and anode (ITO).

[0131] from Figure 9 It can be seen that Figure 9 The second organic electroluminescent unit is composed of two stacked charge generation layers. The light-emitting layer materials and structures in the two second organic electroluminescent units are the same. The third light-emitting sublayer includes a host material and a guest material, and the guest material includes a first dopant and a second dopant. The HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2 eV.

[0132] Example 2

[0133] Reference Figure 10 , Figure 10 A structural schematic diagram of the pixel unit of Example 2 in the embodiment of the present disclosure is shown. Unlike Example 1, each organic electroluminescent unit includes a first light-emitting sublayer and a second light-emitting sublayer, wherein the first light-emitting sublayer is arranged close to the cathode and the second light-emitting sublayer is arranged close to the anode.

[0134] Example 3

[0135] Reference Figure 11 As shown, Figure 11 A structural schematic diagram of the pixel unit of Example 3 in the embodiment of the present disclosure is shown. Different from Example 2, the first light-emitting sublayers are all arranged close to the anode, and the second light-emitting sublayers are all arranged close to the cathode.

[0136] Example 4

[0137] Reference Figure 6 As shown, different from Example 2 and Example 3, the first luminescent sublayers in the organic electroluminescent units close to the cathode layer are all arranged close to the cathode, and the first luminescent sublayers in the organic electroluminescent units close to the anode layer are all arranged close to the anode.

[0138] Reference Figure 12 , Figure 12 Schematic diagram showing the HOMO energy level of the light-emitting layer in this embodiment, Figure 12 Wherein the host is the host material, guest 1 is the first dopant, and guest 2 is the second dopant. Figure 13 , Figure 13 A schematic diagram of the HOMO energy level of a light-emitting layer in the related art is shown, where the guest is only one dopant, such as the first dopant or the second dopant.

[0139] The pixel unit structures shown in Examples 1-4 are respectively Figure 12 and Figure 13 The hole transport method is used for transport detection, and the Figure 14 A schematic diagram of the current and voltage curves, and Figure 15 Schematic diagram of efficiency brightness curve shown. Figure 14 Shown Figure 12 and Figure 13 The current and voltage curve diagram of Figure 14 It can be seen from the figure that the current efficiency of the pixel unit whose guest material includes the first dopant and the second dopant is significantly higher than that of the pixel unit whose guest material includes only one dopant after the voltage is increased to 4V. Figure 15 Shown Figure 12 and Figure 13 Schematic diagram of the efficiency brightness curve, from Figure 15 It can be seen that selecting a light-emitting sublayer whose guest material includes the first dopant and the second dopant has faster carrier transmission, smaller efficiency roll-off, and is more conducive to balanced electron-hole transmission in the light-emitting layer than selecting a structure including only the first dopant or the first dopant.

[0140] Reference Figure 16 , Figure 16 A flowchart of a method for manufacturing a pixel unit of a display substrate in an embodiment of the present disclosure is shown, wherein the method steps include:

[0141] Step S161: forming a first electrode.

[0142] In this embodiment, a TFT circuit is first fabricated on white glass, and then a flat layer PLN is laid, and further a first electrode and a pixel definition layer PDL are fabricated on the PLN. In this embodiment, the first electrode is an anode.

[0143] Step S162: sequentially forming at least one organic electroluminescent unit on the first electrode, wherein the organic electroluminescent unit includes a light-emitting layer, and the light-emitting layer includes a host material and a guest material as a dopant.

[0144] In this embodiment, at least one organic electroluminescent unit needs to be formed sequentially on the first electrode by evaporating the OLED device according to the evaporation sequence of the OLED device, for example Figure 9 As shown, Figure 9 The evaporation sequence for the OLED device is: hole injection layer / hole transport layer / electron blocking layer / third luminescent sublayer / hole blocking layer / electron transport layer / charge generation layer / hole transport layer / electron blocking layer / third luminescent sublayer / hole blocking layer / electron transport layer / electron injection layer. TFE encapsulation is then performed sequentially on top, following CVD1, IJP, and CVD2. Since the organic electroluminescent unit includes a light-emitting layer, which includes a host material and a guest material serving as a dopant, three evaporation sources can be used for this unit. When forming the light-emitting layer, the host material, the first dopant, and the second dopant are simultaneously added, followed by evaporation at rates of 2, 0.1, and 0.1 A / s, respectively.

[0145] Step S163: forming a second electrode on a side of the organic electroluminescent unit away from the first electrode; wherein the host material includes a phosphorescent-doped electron-type host material and a phosphorescent-doped hole-type host material, the guest material includes a first dopant and a second dopant, the HOMO energy level of the host material is lower than the HOMO energy level of the guest material, and the energy level difference between the HOMO energy level of the host material and the HOMO energy level of the guest material is greater than 0.15 eV; the HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2 eV.

[0146] In this embodiment, after at least one organic electroluminescent unit is sequentially formed on the first electrode, a second electrode, i.e., a cathode, is formed on the side of the organic electroluminescent unit facing away from the first electrode. This is to ensure that the host material's electron and hole transport capabilities are unbalanced, and the guest material's trapping of electrons or holes can hinder electron and hole transport.

[0147] Therefore, the host material includes a phosphorescent-doped electron-type host material and a phosphorescent-doped hole-type host material, the guest material includes a first dopant and a second dopant, the HOMO energy level of the host material is lower than the HOMO energy level of the guest material, and the energy level difference between the HOMO energy level of the host material and the HOMO energy level of the guest material is greater than 0.15 eV; the HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2 eV.

[0148] In one embodiment, the light-emitting layer may include a first light-emitting sublayer and a second light-emitting sublayer. When at least one organic electroluminescent unit is formed sequentially on the first electrode layer, the first light-emitting sublayer may be formed first and then the second light-emitting sublayer, or the second light-emitting sublayer may be formed first and then the first light-emitting sublayer.

[0149] For example, a hole injection layer, a hole transport layer and an electron blocking layer can be formed in sequence on the first electrode; the main material and the target dopant are filled on the electron blocking layer, and a first light-emitting sublayer is formed at a corresponding evaporation rate; the main material and the dopant in the guest material except the target dopant are filled on the electron blocking layer, and a second light-emitting sublayer is formed at a corresponding evaporation rate; a hole blocking layer, an electron transport layer and an electron injection layer are formed in sequence on the side of the second light-emitting sublayer facing away from the first electrode.

[0150] wherein the evaporation rate of the host material is higher than the evaporation rate of the guest material, and the target dopant is the first dopant or the second dopant;

[0151] In this embodiment, during the distillation process, when forming the first luminescent sublayer, the main body and the first dopant can be loaded at the same time, and then evaporated at a rate of 2 / 0.1. When forming the second luminescent sublayer, the main body material and the second material can be loaded at the same time, and then evaporated at a rate of 2 / 0.1.

[0152] In this embodiment, when a plurality of organic electroluminescent units need to be formed, a plurality of film layers may be formed in sequence according to the stacking order of the plurality of organic electroluminescent units.

[0153] According to a third aspect of the present disclosure, a display panel is provided, comprising a display substrate, wherein the display substrate comprises any pixel unit described in the first aspect of the present disclosure.

[0154] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0155] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity, or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, commodity, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, commodity, or device that includes the element.

[0156] The above is a detailed introduction to the pixel unit, manufacturing method and display panel of a display substrate provided by the present disclosure. Specific examples are used herein to illustrate the principles and implementation methods of the present disclosure. The description of the above embodiments is only used to help understand the method and core ideas of the present disclosure. At the same time, for those skilled in the art, according to the ideas of the present disclosure, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present disclosure.

[0157] Other embodiments of the present disclosure will readily occur to those skilled in the art after considering the specification and practicing the invention disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the present disclosure being indicated by the following claims.

[0158] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes can be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

[0159] References herein to "one embodiment," "an embodiment," or "one or more embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Furthermore, please note that instances of the phrase "in one embodiment" do not necessarily all refer to the same embodiment.

[0160] In the description provided herein, numerous specific details are described. However, it is understood that embodiments of the present disclosure may be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0161] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in the claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present disclosure may be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The use of the words first, second, and third etc. does not indicate any order. These words may be interpreted as names.

[0162] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present disclosure.

Claims

1. A pixel unit of a display substrate, characterized in that: include: a first electrode; a second electrode; as well as, at least one organic electroluminescent unit, stacked between the first electrode and the second electrode, the organic electroluminescent unit comprising a light-emitting layer, the light-emitting layer comprising a host material and a guest material as a dopant; In which, the HOMO energy level of the host material is lower than the HOMO energy level of the guest material, and the energy level difference between the HOMO energy level of the host material and the HOMO energy level of the guest material is greater than 0.15 eV; the host material includes a phosphorescent-doped electron-type host material and a phosphorescent-doped hole-type host material, and the guest material includes a first dopant and a second dopant, the HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2 eV.

2. The pixel unit according to claim 1, wherein: The spectral difference between the first dopant and the second dopant is less than 1 nm.

3. The pixel unit according to claim 1, wherein: The light-emitting layer includes a first light-emitting sublayer and a second light-emitting sublayer stacked together; Wherein, the host material of the first luminescent sublayer is the same as the host material of the second luminescent sublayer; The first light-emitting sublayer includes the first dopant, and the second light-emitting sublayer includes the second dopant.

4. The pixel unit according to claim 3, wherein: The first electrode is a cathode, and the second electrode is an anode; The first light-emitting sublayer is disposed close to the cathode, and the second light-emitting sublayer is disposed close to the anode.

5. The pixel unit according to claim 3, wherein: The first electrode is a cathode, the second electrode is an anode, the first light-emitting sublayer is arranged close to the anode, and the second light-emitting sublayer is arranged close to the cathode.

6. The pixel unit according to claim 3, wherein: stacking a plurality of the organic electroluminescent units in sequence, with a charge generation layer stacked between every two adjacent organic electroluminescent units; Among the plurality of organic electroluminescent units, there is at least one first organic electroluminescent unit, and the light-emitting layer in the first organic electroluminescent unit includes the first light-emitting sublayer and the second light-emitting sublayer.

7. The pixel unit according to claim 6, wherein: The first electrode is a cathode, the second electrode is an anode, and there are a plurality of the first organic electroluminescent units; Among the two first organic electroluminescent units, the first luminescent sublayer in one of the first organic electroluminescent units is arranged close to the cathode, and the first luminescent sublayer in the other of the first organic electroluminescent units is arranged close to the anode.

8. The pixel unit according to claim 6, wherein: There is a second organic electroluminescent unit among the plurality of organic electroluminescent units, and the second organic electroluminescent unit includes a single-layer third light-emitting sublayer; The third light-emitting sublayer includes the first dopant and the second dopant, and the thickness of the third light-emitting sublayer is greater than the thickness of the first light-emitting sublayer and greater than the thickness of the second light-emitting sublayer.

9. The pixel unit according to any one of claims 1 to 8, characterized in that: The first dopant includes an iridium complex or a platinum complex, and the second dopant includes an iridium complex or a platinum complex.

10. The pixel unit according to any one of claims 1 to 8, characterized in that: The phosphorescent doped electronic host material includes at least one of triazine, pyrazine, pyridine, quinoline, and o-phenanthroline derivatives.

11. The pixel unit according to any one of claims 1 to 8, characterized in that: The phosphorescent-doped hole-type host material includes a derivative of triphenylamine or carbazole.

12. A method for manufacturing a pixel unit of a display substrate, characterized in that: The method comprises: forming a first electrode; forming at least one organic electroluminescent unit on the first electrode in sequence, wherein the organic electroluminescent unit includes a light-emitting layer, and the light-emitting layer includes a host material and a guest material as a dopant; forming a second electrode on a side of the organic electroluminescent unit away from the first electrode; In which, the host material includes a phosphorescent-doped electron-type host material and a phosphorescent-doped hole-type host material, the guest material includes a first dopant and a second dopant, the HOMO energy level of the host material is lower than the HOMO energy level of the guest material, and the energy level difference between the HOMO energy level of the host material and the HOMO energy level of the guest material is greater than 0.15eV; the HOMO energy level of the first dopant is lower than the HOMO energy level of the second dopant, and the energy level difference between the HOMO energy level of the first dopant and the HOMO energy level of the second dopant is greater than 0.2eV.

13. The method for manufacturing a pixel unit according to claim 12, wherein: The step of sequentially forming at least one organic electroluminescent unit on the first electrode layer comprises: forming a hole injection layer, a hole transport layer and an electron blocking layer in sequence on the first electrode; Filling the electron blocking layer with the host material and the target dopant, and forming a first light-emitting sublayer at a corresponding evaporation rate; wherein the target dopant is the first dopant or the second dopant; Filling the host material and the dopant in the guest material except the target dopant on the electron blocking layer, and forming a second light-emitting sublayer at a corresponding evaporation rate; forming a hole blocking layer, an electron transport layer and an electron injection layer in sequence on a side of the second light-emitting sublayer facing away from the first electrode; The evaporation rate of the host material is higher than the evaporation rate of the guest material.

14. A display panel, characterized in that: The device comprises a display substrate, wherein the display substrate comprises the pixel unit according to any one of claims 1 to 11.

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