Display panel

Abstract

The application discloses a display panel, which comprises a substrate, a first electrode, a light-emitting layer and a second electrode. The first electrode is arranged on the substrate. The light-emitting layer is arranged on a side of the first electrode away from the substrate. The light-emitting layer comprises a hole injection sublayer, a hole transport sublayer, a light-emitting sublayer, an electron transport sublayer and an electron injection sublayer which are sequentially arranged on the first electrode. The film compactness parameter of the light-emitting sublayer is greater than or equal to a first threshold value, and the film compactness parameter is determined by a deformation amount of a thin film under unit stress. The inventors of the application find that when the film compactness parameter of the light-emitting sublayer is greater than or equal to the first threshold value, the film compactness parameter and the service life of the display panel are positively correlated, the greater the film compactness parameter, the higher the film compactness, and the longer the service life of the display panel.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, in particular to a display panel. BACKGROUND

[0002] An organic light emitting diode (OLED) display panel has the characteristics of self-emission, fast response, wide viewing angle, etc., and has a very broad application prospect.

[0003] In the structure design strategy of the existing OLED display panel, more consideration is given to the molecular orbital energy level arrangement form of each functional layer. However, optimizing the energy level arrangement form is more to optimize the efficiency of the OLED device. However, efficiency is not the main reason for limiting the large-scale commercialization of blue phosphor OLED devices. It is because the service life of the existing blue phosphor OLED device is generally short, which leads to the fact that the blue phosphor OLED light-emitting device cannot be widely used. SUMMARY

[0004] The embodiment of the present application provides a display panel for improving the service life of the display panel.

[0005] The embodiment of the present application provides a display panel, comprising:

[0006] a substrate,

[0007] a first electrode disposed on the substrate;

[0008] a light-emitting layer disposed on a side of the first electrode away from the substrate, the light-emitting layer comprising a hole injection sublayer, a hole transport sublayer, a light-emitting sublayer, an electron transport sublayer, and an electron injection sublayer disposed in sequence;

[0009] a second electrode disposed on a side of the light-emitting layer away from the substrate;

[0010] The film compactness parameter of the light-emitting sublayer is greater than or equal to a first threshold value, and the film compactness parameter is determined by the deformation amount of the film under a unit stress condition.

[0011] Optionally, in some embodiments provided by the present application, the film compactness parameter is determined by the thickness deformation amount of the stress part of the film in the thickness direction of the film under the unit stress condition.

[0012] Optionally, in some embodiments provided by the present application, the film compactness parameter can be calculated by the following formula:

[0013] X = ΔF / ΔH,

[0014] Wherein, ΔF is the difference of different forces in the thickness direction of the film; and ΔH is the thickness difference of the stressed part of the film under different forces.

[0015] Optionally, in some embodiments provided in the present application, the first threshold value is -1.7, and the film compactness parameter of the light-emitting sub-layer is less than 0.

[0016] Optionally, in some embodiments provided in the present application, the ratio between the size deformation amplitude of the light-emitting sub-layer and the original size of the light-emitting sub-layer is less than or equal to 5% under the energized working state of the display panel.

[0017] Optionally, in some embodiments provided in the present application, the ratio between the thickness expansion amplitude of the light-emitting sub-layer and the original thickness of the light-emitting sub-layer is less than or equal to 5% under the energized working state of the display panel.

[0018] Optionally, in some embodiments provided in the present application, the ratio between the size deformation amplitude of the light-emitting sub-layer and the original size of the light-emitting sub-layer is less than or equal to 10% under the heating state.

[0019] Optionally, in some embodiments provided in the present application, the ratio between the thickness expansion amplitude of the light-emitting sub-layer and the original thickness of the light-emitting sub-layer is less than or equal to 10% under the heating state.

[0020] Optionally, in some embodiments provided in the present application, the energy level difference between the highest occupied orbital of the hole transport sub-layer and the light-emitting sub-layer is less than or equal to 0.2eV, and the energy level difference between the lowest unoccupied orbital of the electron transport sub-layer and the light-emitting sub-layer is less than or equal to 0.2eV.

[0021] Optionally, in some embodiments provided in the present application, the light-emitting sub-layer comprises a blue phosphor light-emitting material or a blue fluorescent light-emitting material.

[0022] The embodiments of the present application provide a display panel. The display panel comprises a substrate, a first electrode, a light-emitting layer and a second electrode. The first electrode is arranged on the substrate. The light-emitting layer is arranged on the side of the first electrode away from the substrate. The light-emitting layer comprises a hole injection sub-layer, a hole transport sub-layer, a light-emitting sub-layer, an electron transport sub-layer and an electron injection sub-layer which are sequentially arranged on the first electrode. The film compactness parameter of the light-emitting sub-layer is greater than or equal to a first threshold value. The film compactness parameter is determined by the deformation amount of the film under the unit stress condition. The inventors of the present application find that when the film compactness parameter of the light-emitting sub-layer is greater than or equal to the first threshold value, the film compactness parameter and the service life of the display panel are positively correlated. The greater the film compactness parameter, the higher the film compactness, and the longer the service life of the display panel. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0024] Figure 1 A structural schematic diagram of a display panel provided by the embodiments of the present application;

[0025] Figure 2 A schematic diagram for characterizing the film compactness parameters of the light-emitting sublayer by atomic force microscopy in the embodiments of the present application;

[0026] Figure 3 A linear relationship fitted by taking mCP as the host material of the light-emitting sublayer provided by the embodiments of the present application;

[0027] Figure 4 A chemical structural formula of an organic light-emitting material provided by the embodiments of the present application;

[0028] Figure 5 A band diagram of a display panel provided by the embodiments of the present application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below in combination with the drawings. Please refer to the drawings in the drawings, in which the same component symbols represent the same components. The following description is based on the shown specific embodiments of the present application, which should not be regarded as limiting other specific embodiments of the present application not described in detail herein. The word “embodiment” used in the present specification means example, illustration or example.

[0030] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements indicated thereby must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated thereby. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0031] The present application provides a display panel. The following will be described in detail. It should be noted that the description order of the following embodiments is not limited as the preferred order of the embodiments.

[0032] The display panel provided by the present application will be described in detail below through specific embodiments.

[0033] Please refer to Figure 1 , Figure 1 A structural schematic diagram of the display panel provided by the present application is shown. The present application provides a display panel 100, which includes a substrate 101, a first electrode 102, a light-emitting layer 103 and a second electrode 104. The first electrode 102 is arranged on the substrate 101. The light-emitting layer 103 is arranged on the side of the first electrode 102 away from the substrate 101. The light-emitting layer 103 includes a hole injection sub-layer 1031, a hole transport sub-layer 1032, a light-emitting sub-layer 1033, an electron transport sub-layer 1034 and an electron injection sub-layer 1035 arranged in sequence on the first electrode 102. The film compactness parameter of the light-emitting sub-layer 1033 is greater than or equal to a first threshold value, and the film compactness parameter is determined by the deformation amount of the film under unit stress condition.

[0034] The present application has found that when the film compactness parameter of the light-emitting sub-layer 1033 is greater than or equal to the first threshold value, the film compactness parameter and the service life of the display panel 100 are positively correlated, the greater the film compactness parameter, the higher the film compactness, and the longer the service life of the display panel 100.

[0035] It should be understood that in the embodiments of the present application, the film compactness parameter is related to the film compactness, the higher the film compactness, the greater the film compactness parameter, and the longer the service life of the display panel 100.

[0036] It should be noted that in the embodiments of the present application, the unit stress includes but is not limited to the force applied to the light-emitting sub-layer 1033. The unit stress here refers to the force applied to the light-emitting sub-layer 1033 in the smallest unit for measurement, such as 1N, 2N, 5N, 10N, etc.

[0037] It should be noted that in the embodiments of the present application, the deformation amount of the thin film includes but is not limited to the deformation amount of the thickness of the thin film.

[0038] In some embodiments, the thin film density parameter is determined by the thickness deformation amount of the stressed part of the thin film in the thickness direction of the thin film under the condition of unit stress. Specifically, the thin film density parameter can be calculated by the following formula: X = ΔF / ΔH, wherein X is the thin film density parameter, ΔF is the difference of different forces in the thickness direction of the thin film; ΔH is the thickness difference of the stressed part of the thin film under different forces, 0>X≥-1.7N / cm.

[0039] That is, the first threshold value is -1.7. When the thin film density parameter is greater than or equal to -1.7 and less than 0, the greater the thin film density parameter, the higher the density of the thin film, and the longer the service life of the display panel 100.

[0040] Wherein, ΔF can be the difference of two different forces applied to the same stressed part, and ΔH is the difference of the thickness corresponding to the two different forces. Alternatively, ΔF is the difference of the forces applied to two different stressed parts, and ΔH is the difference of the thickness corresponding to the two different forces.

[0041] It should be noted that in the embodiments of the present application, the greater the unit stress of the thin film, the smaller the corresponding thickness of the thin film.

[0042] In the present application, the atomic force microscope can be used to characterize the thin film density parameter of the light-emitting sub-layer 1033. Under the characterization of the atomic force microscope, the thickness of the light-emitting sub-layer 1033 and the force of the probe of the atomic force microscope on the light-emitting sub-layer 1033 are in a linear relationship, and the slope of the linear relationship is the thin film density parameter.

[0043] Specifically, the atomic force microscope is used to characterize the light-emitting sub-layer 1033, and then a linear relationship between the thickness of the light-emitting sub-layer 1033 and the force of the probe of the atomic force microscope on the light-emitting sub-layer 1033 is established. The greater the slope of the linear relationship, the greater the density of the thin film of the light-emitting sub-layer 1033, and the longer the service life of the display panel 100.

[0044] Please refer to Figure 2 , Figure 2FIG. 1 is a schematic diagram of an atomic force microscope used in the embodiment for characterizing the film compactness of the light-emitting sub-layer. The film compactness of the light-emitting sub-layer 1033 is evaluated by using the atomic force microscope to characterize the light-emitting sub-layer 1033.

[0045] The process of using the atomic force microscope to characterize the light-emitting sub-layer 1033 can include disposing the light-emitting sub-layer 1033 on the substrate S, and then using the probe P to detect the relative thickness of the light-emitting sub-layer 1033. The disposing of the light-emitting sub-layer 1033 on the substrate S includes disposing a polyimide layer PI on the substrate S, the polyimide layer PI covering a portion of the substrate S. Then, the light-emitting sub-layer 1033 is evaporated on the substrate S, the light-emitting sub-layer 1033 covering the polyimide layer PI and the substrate S, and then the polyimide layer PI is removed to obtain the light-emitting sub-layer 1033 on the substrate S. In the embodiment, the light-emitting sub-layer 1033 only covers a portion of the substrate S, thereby forming a height difference for measuring the relative thickness of the light-emitting sub-layer 1033. The step of using the probe P to detect the relative thickness of the light-emitting sub-layer 1033 includes: first, randomly selecting an arbitrary point on the light-emitting sub-layer 1033, and then using the probe P to apply a first force to the substrate S to measure a first relative thickness of the light-emitting sub-layer 1033. Then, another point on the light-emitting sub-layer 1033 is randomly selected, and the probe P is used to apply a second force to the substrate S to measure a second relative thickness of the light-emitting sub-layer 1033. In this way, a third relative thickness of the light-emitting sub-layer 1033 is measured by using a third force, a fourth relative thickness of the light-emitting sub-layer 1033 is measured by using a fourth force, and an Nth relative thickness of the light-emitting sub-layer 1033 is measured by using an Nth force. Finally, the slope of the linear relationship fitted by taking the force of the probe P on the light-emitting sub-layer 1033 as the abscissa and the thickness of the light-emitting sub-layer 1033 as the ordinate is taken as the film compactness parameter of the light-emitting sub-layer 1033. The greater the slope, the greater the film compactness of the light-emitting sub-layer 1033, and the longer the service life of the display panel 100.

[0046] In the embodiment, the thickness of the light-emitting sub-layer 1033 decreases as the force of the probe P on the light-emitting sub-layer 1033 increases. The greater the force of the probe P on the light-emitting sub-layer 1033, the smaller the corresponding thickness of the light-emitting sub-layer 1033. In the embodiment, the corresponding linear relationship is fitted by taking the force of the probe P on the light-emitting sub-layer 1033 as the abscissa and the thickness of the light-emitting sub-layer 1033 as the ordinate.

[0047] Please refer to Figure 3 , Figure 3The linear relationship of the light-emitting host material provided in the embodiment of the present application with mCP (N,N-dicarbazole-3,5-benzene) as the light-emitting sublayer is fitted. In the embodiment of the present application, the slope of the fitted linear relationship is taken as the film compactness parameter of the light-emitting sublayer 1033, with the force (F) of the probe acting on the light-emitting sublayer 1033 as the abscissa and the thickness (T) of the light-emitting sublayer 1033 as the ordinate, wherein the slope is -1.69.

[0048] Specifically, the embodiment of the present application uses 10 different organic light-emitting materials as the host material of the light-emitting sublayer 1033 to evaluate the film compactness and light-emitting performance of the light-emitting sublayer 1033. Please refer to Figure 4 , Figure 4 The chemical structural formula of the organic light-emitting material provided in the embodiment of the present application. The organic light-emitting material includes DCB, CBP, CDBP, CBPE, mCP, BCzph, CzC, 4CzPBP, TPBi, BCzTPM, BCPPA, NPB, TAPC and Firpic.

[0049] Please refer to Table 1, which is the film compactness parameter of the 10 different organic light-emitting materials as the host material of the light-emitting sublayer and the performance test results of the display panel.

[0050] Table 1:

[0051]

[0052]

[0053] As can be seen from Table 1, under the same conditions, the light-emitting sublayer 1033 and the display panel 100 prepared by using different organic light-emitting materials as the host material are characterized by atomic force microscopy, the greater the slope, the greater the film compactness of the light-emitting sublayer 1033. With the increase of the film compactness of the light-emitting sublayer 1033, the influence on the voltage and the electroluminescence peak (EL Peak) is small, the external quantum efficiency (EQE) is slightly improved, and the lifetime is significantly improved. It is proved that the higher the film compactness of the light-emitting sublayer 1033, the more beneficial to the light-emitting performance of the blue phosphor material.

[0054] It should be noted that the slope is measured by the atomic force microscope acting on the film of the light-emitting sublayer 1033.

[0055] When the slope is greater than or equal to -1.7, the lifetime of the display panel 100 is significantly improved, of course, the first threshold can also be selected as -1.65, -1.6, -1.55, -1.5, -1.45, -1.4, -1.35, -1.3, -1.25, -1.2, -1.15, etc.

[0056] Compared with red phosphor and green phosphor materials, the lifetime of blue phosphor material is particularly short, resulting in reduced overall lifetime and reliability of the display panel 100. In the embodiments of the present application, taking the blue phosphor material as an example, the lifetime and reliability of the display panel 100 of the blue phosphor material are improved by improving the compactness of the film forming of the blue phosphor material, thereby improving the market competitiveness.

[0057] In some embodiments, the light-emitting sub-layer 1033 includes, but is not limited to, a blue phosphor light-emitting material or a blue fluorescent light-emitting material. The light-emitting sub-layer 1033 can also be a red phosphor light-emitting material and a green phosphor light-emitting material, a red fluorescent light-emitting material and a green fluorescent light-emitting material.

[0058] In the embodiments of the present application, the light-emitting sub-layer 1033 is characterized by an atomic force microscope, and a linear relationship between the thickness of the light-emitting sub-layer 1033 and the force of the probe of the atomic force microscope acting on the light-emitting sub-layer 1033 is established. The greater the slope of the linear relationship, the greater the compactness parameter of the film of the light-emitting sub-layer 1033, and the greater the compactness of the light-emitting sub-layer 1033, the longer the lifetime of the display panel 100. In the embodiments of the present application, when the film compactness parameter of the light-emitting sub-layer 1033 is greater than or equal to a first threshold value, the lifetime of the display panel 100 is greatly improved.

[0059] In some embodiments of the present application, the film forming quality of the light-emitting sub-layer 1033 can also be evaluated by the size deformation amplitude of the display panel 100.

[0060] In order to further evaluate the film forming quality of the light-emitting sub-layer 1033, the ratio between the size change amplitude of the light-emitting sub-layer 1033 and the original shape size of the light-emitting sub-layer 1033 is less than or equal to 5% under the power-on working state of the display panel 100.

[0061] It should be noted that the size change amplitude of the light-emitting sub-layer 1033 includes, but is not limited to, the thickness expansion amplitude of the light-emitting sub-layer 1033.

[0062] In some embodiments, the ratio between the thickness expansion amplitude of the light-emitting sub-layer 1033 and the original thickness of the light-emitting sub-layer 1033 is less than or equal to 5% under the power-on working state of the display panel 100.

[0063] For example, the light-emitting sub-layer 1033 has a first thickness a before power-on working, and the display panel 100 is lit at a preset brightness for a preset working time, and the light-emitting sub-layer 1033 has a second thickness b. The thickness expansion amplitude ω1 of the second thickness b and the first thickness a is less than or equal to 5%, wherein ω1 = [(b-a) / a]*100%.

[0064] In some embodiments, the preset brightness can be 100 nit, and the preset time can be 1 hour. Specifically, the thickness of the display panel 100 before and after being illuminated is measured by using the interferometer after the display panel 100 works at the brightness of 100 nit for 1 hour.

[0065] In some embodiments, the thickness of the display panel 100 before and after being heated can also be evaluated by heating the display panel 100.

[0066] In some embodiments, the ratio between the size variation amplitude of the light-emitting sub-layer 1033 in the heated state and the original size of the light-emitting sub-layer 1033 is less than or equal to 10%.

[0067] In some embodiments, the ratio between the thickness expansion amplitude of the light-emitting sub-layer 1033 in the heated state and the original thickness of the light-emitting sub-layer 1033 is less than or equal to 10%.

[0068] Specifically, the light-emitting sub-layer 1033 before being heated has a first thickness a, and the light-emitting sub-layer has a second thickness c after the display panel 100 is heated at a preset temperature for a preset working time; wherein the thickness expansion amplitude ω2 of the second thickness c and the first thickness a is less than or equal to 10%. Wherein ω2 = [(c-a) / a]*100%.

[0069] The preset temperature can be 100 degrees Celsius, and the preset working time can be 1 hour. Specifically, the display panel 100 is heated to 100 degrees Celsius, and the thickness of the display panel 100 after being heated is measured by using the interferometer after being kept at 100 degrees Celsius for 1 hour.

[0070] Please refer to Table 2, which is the thickness expansion amplitude of the light-emitting sub-layer of the display panel 100 in the powered state and the heated state.

[0071] Table 2:

[0072] Organic light emitting material ω1 ω2 DCB 7.4％ 14.5％ CBP 7.0％ 13.7％ CDBP 6.5％ 12.4％ CBPE 5.7％ 11.5％ mCP 5.1％ 10.4％ BCzPh 4.6％ 10.1％ CzC 4.1％ 9.2％ 4CzPBP 3.9％ 8.7％ BCzTPM 3.6％ 7.9％ BCPPA 3.2％ 7.2％

[0073] As can be seen from Table 2, the thickness of the display panel 100 before and after being heated is measured by using the interferometer, and the thickness expansion amplitude before and after being heated is obtained. The smaller the thickness expansion amplitude, the better the film forming quality of the light-emitting sub-layer 1033, the higher the film density of the light-emitting sub-layer 1033, and the better the performance of the display panel 100. The smaller the thickness expansion amplitude after being heated. It should be noted that in actual application, the maximum value of ω1 can be selected as 5%, 4.5%, 4%, 3.5%, 3%, etc.; and the maximum value of ω2 can be selected as 10%, 9.5%, 9%, 8.5%, 8%, 7.5%, 7%, etc.

[0074] In combination with Table 1 and Table 2, it can be seen that the higher the film compactness parameter of the light-emitting sub-layer is, the higher the film compactness is, the better the light-emitting performance of the device is, the smaller the thickness expansion amplitude after heating is, and the longer the service life of the display panel 100 is.

[0075] In the embodiments of the present application, the film forming quality of the light-emitting layer of the display panel 100 is evaluated from two dimensions. The density of the light-emitting sub-layer 1033 is evaluated, and the thickness of the display panel 100 before and after heating is evaluated as a whole. By evaluating the film forming quality of the display panel 100 from two dimensions, it is shown that under the characterization of the atomic force microscope, the larger the slope is, the larger the film compactness parameter of the light-emitting sub-layer 1033 is, and the larger the density of the light-emitting sub-layer 1033 is. With the increase of the density of the light-emitting sub-layer 1033, the influence on the voltage and the electroluminescence peak (EL Peak) is small, the external quantum efficiency (EQE) is slightly improved, and the service life is significantly improved. It is proved that the higher the density of the light-emitting sub-layer 1033 is, the more beneficial to the light-emitting performance of the blue phosphor material. The thickness of the complete display panel before and after heating is measured by an interferometer, and the thickness expansion amplitude before and after heating is obtained. The smaller the thickness expansion amplitude is, the better the film forming quality of the light-emitting sub-layer 1033 is, the higher the density of the light-emitting layer is, and the smaller the thickness expansion amplitude after heating is.

[0076] For reference Figure 5 , Figure 5 A kind of energy level arrangement mode diagram of display panel provided in the embodiments of the present application. In some embodiments, the lowest unoccupied orbital energy level and the highest occupied orbital energy level of the hole transport sub-layer 1032, the light-emitting sub-layer 1033 and the electron transport sub-layer 1034 decrease in turn.

[0077] In the embodiments of the present application, since the lowest unoccupied orbital energy level and the highest occupied orbital energy level of the hole transport sub-layer 1032, the light-emitting sub-layer 1033 and the electron transport sub-layer 1034 decrease in turn, i.e. the highest occupied orbital (The Highest Occupied Molecular Orbitals) energy level and the lowest unoccupied orbital (The Lowest Unoccupied Molecular Orbitals) energy level of each adjacent organic film layer material are arranged in a ladder shape, which is beneficial to the balanced injection and transmission of carriers, reduces the energy level barrier, thereby improving the light-emitting efficiency of the display panel 100, and further obtaining optimal device performance.

[0078] It should be noted that the highest occupied orbital refers to the molecular orbital with the highest energy in the molecular orbital occupied by electrons, which is also called the highest occupied molecular orbital. In the molecular orbital not occupied by electrons, the molecular orbital with the lowest energy is called the lowest unoccupied orbital.

[0079] In some embodiments, electrons and holes can be injected in a balanced 1:1 ratio to achieve efficient utilization of electrons and holes.

[0080] To lower the potential barrier for hole injection from the first electrode 102, enabling efficient hole injection into the display panel 100, the hole transport rate is generally greater than the electron transport rate. To ensure recombination of injected electrons and holes in the light-emitting sublayer 1033, the energy level structures of the hole transport sublayer 1032 and the light-emitting sublayer 1033 are matched, and their hole migration speeds are also matched. To lower the potential barrier for electron injection from the second electrode 104, enabling efficient electron injection into the display panel 100, the material of the electron injection sublayer 1035 is selected to ensure efficient electron injection into the display panel 100 from the second electrode 104. To lower the potential barrier for hole injection from the anode, enabling efficient hole injection into the OLED device, the matching of the material's energy levels and the material of the second electrode 104 must be considered when selecting the electron injection layer material.

[0081] In some embodiments, the lowest empty orbital energy level and the highest occupied orbital energy level of the hole injection sublayer 1031, the hole transport sublayer 1032, the light emission sublayer 1033, the electron transport sublayer 1034, and the electron injection sublayer 1035 decrease sequentially. This arrangement facilitates balanced carrier injection and transport, lowers the energy level barrier, and further improves the luminous efficiency of the display panel 100, thereby achieving optimal device performance.

[0082] In some embodiments, the energy level difference between the highest occupied orbitals of the hole transport sublayer 1032 and the light-emitting sublayer 1033 is less than or equal to 0.2 eV, and the energy level difference between the lowest unoccupied orbitals of the electron transport sublayer 1034 and the light-emitting sublayer 1033 is less than or equal to 0.2 eV. This reduces the potential barrier between adjacent organic film layers and further improves the luminous efficiency of the display panel 100.

[0083] Specifically, the energy level difference between the highest occupied orbitals of the hole transport sublayer 1032 and the light-emitting sublayer 1033 can be any one of 0.05 eV, 0.08 eV, 0.12 eV, 0.15 eV, 0.18 eV, or 0.2 eV. Similarly, the energy level difference between the lowest unoccupied orbitals of the hole transport sublayer 1032 and the light-emitting sublayer 1033 can be any one of 0.05 eV, 0.08 eV, 0.12 eV, 0.15 eV, 0.18 eV, or 0.2 eV. This reduces the potential barrier between adjacent organic film layers, further improving the luminous efficiency of the display panel 100.

[0084] In some embodiments, the display panel 100 further comprises a thin film transistor structure layer, which is disposed on the substrate 101 and used to drive the display panel 100 to emit light.

[0085] In some embodiments, the first electrode 102 is an anode, and the material of the first electrode 102 comprises indium tin oxide and silver, and specifically can be indium tin oxide, silver, and a three-layer laminated structure of indium tin oxide. The second electrode 104 is a cathode, and the material of the second electrode 104 is a magnesium-silver alloy.

[0086] Correspondingly, the present application further provides a manufacturing method of the display panel 100, which comprises the following steps:

[0087] Step B001: providing a first electrode, wherein the first electrode comprises indium tin oxide and silver.

[0088] After step B001, a hole injection sublayer and a hole transport sublayer are further formed on the first electrode, wherein the material of the hole transport sublayer can be NPB (N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4-4'-diamine), and the thickness of the hole transport sublayer is between 30 nm and 60 nm. In a specific embodiment, the thickness of the hole transport sublayer can be 45 nm.

[0089] Subsequently, an electron blocking layer is formed on the hole transport sublayer, and the material of the electron blocking layer can be TAPC (4,4'-cyclohexyl di[N,N-di(4-methylphenyl) aniline]). The thickness of the electron blocking layer is between 2 nm and 10 nm. In a specific embodiment, the thickness of the electron blocking layer can be 5 nm.

[0090] Step B002: forming a light-emitting sublayer on the electron blocking layer, wherein the light-emitting sublayer is an organic light-emitting material, the concentration of the doped organic light-emitting material is less than 2%, and the evaporation rate of the light-emitting sublayer is less than or equal to 1.5 angstroms per second. In an embodiment, the evaporation rate of the light-emitting sublayer is 1.0 angstroms per second. The host material of the organic light-emitting material can be at least one of DCB, CBP, CDBP, CBPE, mCP, BCzph, CzC, 4CzPBP, TPBi, BCzTPM, BCPPA, NPB, TAPC, and Firpic, and the chemical structural formula of the organic light-emitting material is as shown in the following formula (I). Figure 4 The thickness of the light-emitting sublayer can be between 10 nm and 30 nm. In a specific embodiment, the thickness of the light-emitting sublayer can be 20 nm.

[0091] After step B002, it further includes sequentially forming an electron transport sub-layer and an electron injection sub-layer on the side of the light emitting sub-layer away from the first electrode. The material of the electron transport sub-layer can be TPBi (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene), and the thickness of the electron transport sub-layer is between 20 nm and 40 nm. In a specific embodiment, the thickness of the electron transport sub-layer can be 35 nm.

[0092] Step B003: evaporating a second electrode on the side of the light emitting sub-layer away from the first electrode. The material of the second electrode can include magnesium-silver alloy. The evaporation rate of the second electrode is less than or equal to 3 angstroms per second, and in an embodiment, the evaporation rate of the second electrode can be 2 angstroms per second. The thickness of the second electrode is between 50 nm and 150 nm, for example, the thickness of the second electrode can be 100 nm.

[0093] In summary, although the present application has been disclosed with preferred embodiments as above, the preferred embodiments are not intended to limit the present application, and those skilled in the art can make various modifications and decorations without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application is subject to the scope defined by the claims.

Claims

1. A display panel, characterized in that, include: Substrate, A first electrode is disposed on the substrate; A light-emitting layer is disposed on the side of the first electrode away from the substrate. The light-emitting layer includes a hole injection sublayer, a hole transport sublayer, a light-emitting sublayer, an electron transport sublayer, and an electron injection sublayer stacked sequentially. The second electrode is disposed on the side of the light-emitting layer away from the substrate; Wherein, the film compactness parameter of the light-emitting sublayer is greater than or equal to a first threshold, and the film compactness parameter is determined by the deformation of the film under unit force conditions; The film compactness parameter is determined by the thickness deformation of the stressed portion of the film under unit force in the thickness direction of the film. The film compactness parameter is calculated by the following formula: X=ΔF / ΔH, where ΔF is the difference between different forces in the thickness direction of the film; ΔH is the thickness difference of the stressed portion of the film under different forces; the first threshold is -1.7, and the film compactness parameter of the luminescent sublayer is less than 0; the energy level difference between the highest occupied orbitals of the hole transport sublayer and the luminescent sublayer is less than or equal to 0.2eV, and the energy level difference between the lowest empty orbitals of the electron transport sublayer and the luminescent sublayer is less than or equal to 0.2eV.

2. The display panel according to claim 1, characterized in that, When the display panel is powered on, the ratio between the dimensional deformation of the light-emitting sublayer and its original shape and size is less than or equal to 5%.

3. The display panel according to claim 2, characterized in that, When the display panel is powered on, the ratio between the thickness expansion of the light-emitting sublayer and the original thickness of the light-emitting sublayer is less than or equal to 5%.

4. The display panel according to claim 1, characterized in that, When the light-emitting sublayer is heated, the ratio between the magnitude of its dimensional deformation and the original shape and size of the light-emitting sublayer is less than or equal to 10%.

5. The display panel according to claim 4, characterized in that, When the light-emitting sublayer is heated, the ratio between the thickness expansion of the sublayer and its original thickness is less than or equal to 10%.

6. The display panel according to claim 1, characterized in that, The luminescent sublayer comprises a blue phosphorescent material or a blue fluorescent material.

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