Organic light-emitting device and display device

Abstract

The invention relates to an organic light-emitting device and a display device. The organic light-emitting device comprises a first electrode layer, a second electrode layer, a light-emitting layer and a hole injection layer, the first electrode layer and the second electrode layer are oppositely arranged, the light-emitting layer is located between the first electrode layer and the second electrode layer, and the hole injection layer is located between the first electrode layer and the light-emitting layer; wherein the hole injection layer comprises a hole injection main body part and a P-type dopant doped in the hole injection main body part, the P-type dopant comprises an electron withdrawing group, and the mass percentage range of the P-type dopant in the hole injection layer is 8%-10%. The organic light-emitting device can effectively improve the exciton recombination efficiency, thereby effectively improving the light-emitting efficiency and stability of the organic light-emitting device.

Description

Technical Field

[0001] This application relates to the field of display technologies, and particularly to an organic light-emitting device and a display device. Background Art

[0002] Organic Light-Emitting Diode (OLED) is gradually becoming a major part of display technologies due to its advantages such as high brightness, low power consumption, wide viewing angle, fast response speed, and lightweight form. The preparation methods of OLED devices include evaporation and solution methods. Among them, the evaporation method requires heating organic materials to vaporize and sublime through methods such as current heating, electron beam bombardment heating, or laser heating in a vacuum environment. The gaseous atoms or molecules move in a straight line with a large mean free path and collide with the substrate surface to condense and form a thin film. The solution method refers to dissolving organic materials in a suitable solvent to form a solution, and then uniformly coating the solution on the substrate by spin coating, inkjet printing, etc. After the solvent evaporates, the organic materials form a thin film on the substrate. Compared with evaporated OLED devices, solution-processed organic light-emitting diodes (s-OLEDs), such as OLED devices fabricated based on spin coating, blade coating, or inkjet printing, have advantages such as simple process, cost-effectiveness, and high material utilization rate, and have attracted much attention in recent years.

[0003] Compared with macromolecular polymer thin films, small molecule thin films have characteristics such as good compactness and high mobility, and small molecule thin films have been widely used in evaporated OLED devices. Currently, the solution preparation process still faces challenges such as mutual solubility between thin films, uneven film formation, and poor carrier injection efficiency. Small molecule crosslinking materials have advantages such as good film-forming property, low roughness, and solvent resistance. Therefore, preparing high-quality, high-injection-efficiency, and high-stability small molecule crosslinked thin films based on the solution method is an effective way to improve the efficiency of s-OLED devices.

[0004] However, the mismatch between the hole and electron transport rates in s-OLED devices results in low exciton recombination efficiency, which hinders the commercial development of s-OLEDs. Summary of the Invention

[0005] Embodiments of this application provide an organic light-emitting device and a display device, which can effectively improve the exciton recombination efficiency, thereby effectively improving the luminous efficiency and stability of the organic light-emitting device.

[0006] To achieve the above object, according to the first aspect of this application, an organic light-emitting device is provided, including a first electrode layer, a second electrode layer, a light-emitting layer, and a hole injection layer; the first electrode layer and the second electrode layer are disposed opposite to each other, the light-emitting layer is located between the first electrode layer and the second electrode layer, and the hole injection layer is located between the first electrode layer and the light-emitting layer;

[0007] Wherein, the hole injection layer includes a hole injection main body and a P-type dopant doped in the hole injection main body, the P-type dopant includes an electron-withdrawing group, and the mass percentage range of the P-type dopant in the hole injection layer is 8% to 10%.

[0008] In some embodiments, the electron-withdrawing group includes at least one of fluorine and boron.

[0009] In some embodiments, the material of the hole injection main body includes a crosslinking group, and the crosslinking group includes at least one of a styrene group, a phenylacetylene group, or a benzocyclobutene group.

[0010] In some embodiments, the band gap of the hole injection layer ranges from 2.8 eV to 2.9 eV.

[0011] In some embodiments, the organic light-emitting device further includes an electron transport layer located between the light-emitting layer and the second electrode layer;

[0012] The electron transport layer includes an electron transport main body and a doping layer, and the doping layer covers one side of the electron transport main body close to the second electrode layer; in the electron transport layer, the thickness percentage range of the doping layer is 50% to 70%.

[0013] In some embodiments, the organic light-emitting device further includes an electron transport layer located between the light-emitting layer and the second electrode layer; the electron transport layer includes a first sub-electron transport layer and a second sub-electron transport layer stacked, the first sub-electron transport layer is located between the light-emitting layer and the second electrode layer, and the second sub-electron transport layer is located between the first sub-electron transport layer and the second electrode layer;

[0014] The second sub-electron transport layer includes an electron transport main body and a doping layer, and the doping layer covers one side of the electron transport main body close to the second electrode layer; the material of the electron transport main body is the same as that of the first sub-electron transport layer, and in the second sub-electron transport layer, the thickness percentage range of the doping layer is 50% to 80%.

[0015] In some embodiments, the material of the doping layer includes lithium 8-hydroxyquinoline.

[0016] In some embodiments, when the chromaticity coordinate of the light emitted by the organic light-emitting device in the Y-axis direction is within the range of 0.039 to 0.046, the ratio of the current efficiency of the organic light-emitting device to the chromaticity coordinate is greater than 160 and less than 210.

[0017] In some embodiments, when the current density of the organic light-emitting device is 10 mA / cm 2 the current efficiency of the organic light-emitting device is greater than 7 cd / A and less than 10 cd / A.

[0018] According to a second aspect of the present application, there is also provided a display device, which includes the organic light-emitting device described above.

[0019] In the organic light-emitting device and the display device according to the embodiments of the present application, by adjusting the doping concentration of the P-type dopant containing an electron-withdrawing group in the hole injection layer, the highest occupied molecular orbital (HOMO) energy level of the hole injection layer is changed, thereby adjusting the hole injection barrier, so that the hole injection rate is balanced with the electron injection rate (that is, the hole and electron transport rates are matched), thereby improving the exciton recombination efficiency in the light-emitting layer, and further improving the light-emitting efficiency of the organic light-emitting device. Moreover, through research, it is found that when the mass fraction of the P-type dopant in the hole injection layer is controlled within the range of 8% to 10%, the light-emitting efficiency and stability of the organic light-emitting device can be effectively improved.

[0020] Other features and advantages of the present application will be described in detail in the following specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application, and those skilled in the art can also obtain other drawings based on these drawings without creative efforts.

[0022] In order to more fully understand the present application and its beneficial effects, the following will be described in conjunction with the drawings, where the same reference numerals in the following description represent the same parts.

[0023] Figure 1 is a schematic structural diagram of an organic light-emitting device provided by an embodiment of the present application;

[0024] Figure 2 is a schematic structural diagram of a hole injection layer provided by an embodiment of the present application;

[0025] Figure 3 is a schematic diagram of carrier migration of an organic light-emitting device provided by an embodiment of the present application;

[0026] Figure 4 is a schematic diagram of carrier migration of another organic light-emitting device provided by an embodiment of the present application;

[0027] Figure 5It is a schematic diagram of carrier migration of another organic light-emitting device provided by an embodiment of the present application;

[0028] Figure 6 It is a schematic diagram of carrier migration of another organic light-emitting device provided by an embodiment of the present application;

[0029] Figure 7 It is a schematic diagram of the structure of an electron transport layer provided by an embodiment of the present application;

[0030] Figure 8 It is a schematic diagram of the structure of another electron transport layer provided by an embodiment of the present application;

[0031] Figure 9 It is a schematic diagram of the results of CIEy and BI of the comparative device OLED-Ref1, the experimental device OLED-1, and the experimental device OLED-2 provided by an embodiment of the present application;

[0032] Figure 10 It is a schematic diagram of the results of the current efficiency of the comparative device OLED-Ref1, the experimental device OLED-1, and the experimental device OLED-2 changing with the current density provided by an embodiment of the present application;

[0033] Figure 11 It is a schematic diagram of the results of CIEy and BI of the comparative device OLED-Ref2, the experimental device OLED-3, the experimental device OLED-4, and the experimental device OLED-5 provided by an embodiment of the present application;

[0034] Figure 12 It is a schematic diagram of the results of the current efficiency of the comparative device OLED-Ref2, the experimental device OLED-3, the experimental device OLED-4, and the experimental device OLED-5 changing with the current density provided by an embodiment of the present application;

[0035] Figure 13 It is a schematic flowchart of a preparation method of an organic light-emitting device provided by an embodiment of the present application;

[0036] Figure 14 It is a schematic diagram of the structure of a display device provided by an embodiment of the present application.

[0037] Explanation of reference numerals: 1. Organic light-emitting device; 2. First electrode layer; 3. Second electrode layer; 4. Light-emitting layer; 5. Hole injection layer; 6. Hole injection main body; 7. P-type dopant; 8. Hole transport layer; 9. Electron transport layer; 10. Electron transport main body; 11. Doping layer; 9a. First sub-electron transport layer; 9b. Second sub-electron transport layer; 12. Upper light covering layer; 13. Display device; 14. Array substrate. Detailed implementation manners

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application.

[0039] Generally, an electron transport material with a low carrier mobility can be selected to optimize the device performance, but this method is not applicable to the currently solution-processed s-OLED devices. Therefore, the development of electron transport materials with faster mobility and the structural design have become the focus of attention in s-OLED technology.

[0040] Aiming at the problem that the hole transport rate is greater than the electron transport rate in s-OLED devices, resulting in an imbalance in carrier injection and a low exciton recombination efficiency, an electron transport material with better electron transport performance can be used and doped to adjust the LUMO energy level of the electron transport layer, thereby adjusting the energy level difference between the electron transport layer and the light-emitting layer, improving the electron mobility, making the hole injection rate and the electron injection rate reach equilibrium, thus improving the exciton recombination efficiency in the light-emitting layer, and further improving the luminous efficiency of the organic light-emitting device.

[0041] On this basis, the present application further improves the material of the hole injection layer to further optimize the luminous efficiency of the device. Specifically, according to the injection characteristics of carriers in the s-OLED device, the present application embodiment designs a matching doping ratio in the hole injection layer (Hole Injection Layer, HIL) and the electron transport layer (Electron transport layer, ETL) to adjust the injection rates of holes and electrons, so that the injected carriers reach the best balance state, thereby effectively improving the luminous efficiency and service life of the OLED device.

[0042] Please refer to Figure 1 and Figure 2 , Figure 1 which is a schematic structural diagram of an organic light-emitting device provided by an embodiment of the present application, Figure 2 and which is a schematic structural diagram of a hole injection layer provided by an embodiment of the present application.

[0043] As shown in Figure 1 and Figure 2As shown, an embodiment of the present application provides an organic light-emitting device 1, which includes a first electrode layer 2, a second electrode layer 3, an emitting layer (EML) 4, and a hole injection layer (HIL) 5. The first electrode layer 2 and the second electrode layer 3 are disposed opposite to each other. The emitting layer 4 is located between the first electrode layer 2 and the second electrode layer 3, and the hole injection layer 5 is located between the first electrode layer 2 and the emitting layer 4. Among them, the hole injection layer 5 includes a hole injection main body 6 and a P-type dopant (p-dopant) 7 doped in the hole injection main body 6. The P-type dopant 7 includes an electron-withdrawing group, and the mass percentage range of the P-type dopant 7 in the hole injection layer 5 is 8% to 10%.

[0044] In some embodiments, the mass percentage of the P-type dopant 7 in the hole injection layer 5 is 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, or 10%, but not limited thereto.

[0045] It can be understood that the P-type dopant 7 has P-type conductivity, and the main carriers in the hole injection layer 5 are holes.

[0046] In some embodiments, the first electrode layer 2 is an anode layer, and the second electrode layer 3 is a cathode layer.

[0047] In some embodiments, the material of the first electrode layer 2 is selected from IZO (Indium Zinc Oxide) / Ag (silver) / IZO, and the material of the second electrode layer 3 is selected from Yb (ytterbium) / Ag, but not limited thereto.

[0048] In some embodiments, the material of the emitting layer 4 is an organic light-emitting material, and the embodiment of the present application does not limit the material of the emitting layer 4.

[0049] It can be understood that the first electrode layer 2 provides holes to the emitting layer 4, and the second electrode layer 3 provides electrons to the emitting layer 4. After the holes and electrons are injected (transported) into the emitting layer 4, they will recombine into excitons (excited electron-hole pairs) in the emitting layer 4. After the excitons are formed, the molecules in the excited state have higher energy and are in an unstable state. They will return to the ground state through radiative transition and release energy at the same time. The energy released by the radiative transition of the excitons is emitted in the form of photons. The energy of the photons determines the color of the light emission, and the number of photons determines the intensity of the light emission.

[0050] The ease of hole injection is related to the work function of the anode material and the highest occupied molecular orbital (HOMO) energy level of the hole injection layer 5 material. The better the energy level matching degree between the two, the higher the hole injection efficiency.

[0051] In the embodiments of the present application, by adjusting the doping concentration of the P-type dopant 7 containing an electron-withdrawing group in the hole injection layer 5, the highest occupied molecular orbital (HOMO) energy level of the hole injection layer 5 is changed, thereby adjusting the hole injection barrier, so that the hole injection rate and the electron injection rate reach equilibrium (that is, the hole and electron transport rates match), thereby improving the exciton recombination efficiency in the light-emitting layer 4, and further improving the light-emitting efficiency of the organic light-emitting device 1. Moreover, through research, it is found in the present application that when the mass fraction of the P-type dopant 7 in the hole injection layer 5 is controlled within the range of 8% to 10%, the exciton recombination efficiency can be effectively improved, thereby effectively improving the light-emitting efficiency of the organic light-emitting device 1.

[0052] In some embodiments, as Figure 1 shown, the organic light-emitting device 1 further includes a hole transport layer (HTL) 8 and an electron transport layer (ETL) 9. The hole transport layer 8 is located between the hole injection layer 5 and the light-emitting layer 4, and the electron transport layer 9 is located between the light-emitting layer 4 and the second electrode layer 3.

[0053] Please refer to Figure 3 and Figure 4 , Figure 3 is a schematic diagram of carrier migration of an organic light-emitting device provided by an embodiment of the present application, Figure 4 is another schematic diagram of carrier migration of an organic light-emitting device provided by an embodiment of the present application.

[0054] As Figure 3 shown, when the holes (h + ) of the first electrode layer (anode) 2 are injected too fast, the holes accumulate in large quantities at the interface between the hole transport layer (HTL) 8 and the light-emitting layer (EML) 4, resulting in deterioration of the device efficiency. As Figure 4 shown, by doping the P-type dopant 7, the HOMO energy level of the hole injection layer (HIL) 5 is reduced, and the hole injection efficiency is reduced, so that the injection rates of holes and electrons (e - ) reach a relatively balanced state, which is beneficial to improving the exciton recombination efficiency and further beneficial to improving the device efficiency.

[0055] In some embodiments, the electron-withdrawing group in the P-type dopant 7 includes at least one of fluorine (F) and boron (B). In a preferred embodiment, the electron-withdrawing group in the P-type dopant 7 includes both fluorine and boron at the same time.

[0056] It should be noted that in the embodiments of the present application, the electron-withdrawing group in the P-type dopant 7 is a strong electron-withdrawing group.

[0057] Of course, in other embodiments, the P-type dopant 7 may also include other electron-withdrawing groups, especially strong electron-withdrawing groups.

[0058] In some embodiments, the material of the hole injection main body 6 includes crosslinking groups, and the crosslinking groups include at least one of styrene groups, phenylacetylene groups or benzocyclobutene groups.

[0059] In some embodiments, the crosslinking groups in the hole injection main body 6 include at least one of the following groups:

[0060]

[0061] wherein, R is selected from hydrogen or an alkyl group;

[0062] Ar is selected from an aromatic group or a heteroaromatic group;

[0063] represents a crosslinking site.

[0064] In some embodiments, the material of the hole injection layer 5 is formed by crosslinking a small molecule crosslinking material or a mixed small molecule crosslinking material.

[0065] It should be noted that the small molecule crosslinking material has a relatively small molecular weight. For example, the molecular weight of the small molecule crosslinking material is less than or equal to 2000. The mixed small molecule crosslinking material is formed by mixing a small molecule crosslinking material and a large molecule crosslinking material; wherein, the mass ratio of the small molecule crosslinking material is greater than 50%, and the large molecule crosslinking material has a relatively large molecular weight, generally in the order of ten thousand.

[0066] Due to the advantages of good film-forming property, low roughness and solubility resistance of the small molecule crosslinking material, the material of the hole injection layer 5 in the embodiments of the present application is selected from a small molecule crosslinking material or a mixed small molecule crosslinking material, so that the hole injection layer 5 has advantages such as resistance to dissolution, high film density and high hole mobility.

[0067] Since the material of the hole injection layer 5 provided by the embodiments of the present application is selected from a small molecule crosslinking material or a mixed small molecule crosslinking material, the hole injection layer 5 can be prepared by a solution method, and the prepared hole injection layer 5 has the characteristics of good film-forming property and adjustable hole injection rate.

[0068] In some embodiments, the solution method includes processes such as spin coating, blade coating and inkjet printing.

[0069] In some embodiments, the band gap (Eg) of the hole injection layer 5 ranges from 2.8 electron volts (eV) to 2.9 eV. In solid state physics, the band gap refers to the energy difference between the top of the valence band and the bottom of the conduction band in a semiconductor or insulator. For the hole injection layer 5 of the small molecule crosslinking material, its Eg is about 2.8 eV - 2.9 eV, indicating that in this material, the minimum energy difference that an electron needs to overcome to jump from the valence band to the conduction band is 2.8 eV - 2.9 eV.

[0070] In some embodiments, as Figure 7 shown, the electron transport layer 9 includes an electron transport main body portion 10 and a doping layer 11, and the doping layer 11 covers one side of the electron transport main body portion 10 close to the second electrode layer 3. In the electron transport layer 9, the thickness percentage (or thickness ratio) of the doping layer 11 ranges from 50% to 70%.

[0071] In some embodiments, in the electron transport layer 9, the thickness percentage (or thickness ratio) of the doping layer 11 is 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68% or 70%, but is not limited thereto.

[0072] Since the efficiency of electron injection depends on the matching between the work function of the cathode material and the lowest unoccupied molecular orbital (LUMO) energy level of the electron transport layer material, in the embodiments of the present application, while adjusting the doping concentration of the P-type dopant 7 in the hole injection layer 5, the LUMO energy level of the electron transport layer 9 can also be adjusted by adjusting the thickness ratio of the doping layer 11 in the electron transport layer 9, so as to adjust the electron injection rate, so that the hole injection rate and the electron injection rate reach the injection equilibrium state while being improved, further effectively improving the exciton recombination efficiency, and thus further improving the device luminescence efficiency.

[0073] It should be noted that, in this embodiment, the electron transport main body portion 10 and the doping layer 11 of the electron transport layer 9 are fabricated by co-evaporation. The co-evaporation process reduces the interface defects between the electron transport main body portion 10 and the doping layer 11, which is beneficial to improving the electron injection efficiency.

[0074] In other embodiments, in combination with Figure 1 and Figure 8 shown, the electron transport layer 9 includes a first sub-electron transport layer 9a and a second sub-electron transport layer 9b which are stacked. The first sub-electron transport layer 9a is located between the light-emitting layer 4 and the second electrode layer 3, and the second sub-electron transport layer 9b is located between the first sub-electron transport layer 9a and the second electrode layer 3. The second sub-electron transport layer 9b includes an electron transport main body portion 10 and a doping layer 11, and the doping layer 11 covers one side of the electron transport main body portion 10 close to the second electrode layer 3. The materials of the electron transport main body portion 10 and the first sub-electron transport layer 9a are the same, and in the second sub-electron transport layer 9b, the thickness percentage of the doping layer 11 ranges from 50% to 80%. In this embodiment, the electron transport layer 9 is regionally doped and the thickness ratio of the doping layer 11 is adjusted.

[0075] In some embodiments, in the second sub-electron transport layer 9b, the thickness percentage (or thickness ratio) of the doping layer 11 is 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78% or 80%, but not limited thereto.

[0076] It should be noted that in this embodiment, the electron transport main body 10 and the doping layer 11 of the second sub-electron transport layer 9b are fabricated by co-evaporation. Although the material of the electron transport main body 10 of the second sub-electron transport layer 9b is the same as that of the first sub-electron transport layer 9a, the first sub-electron transport layer 9a and the second sub-electron transport layer 9b are not fabricated by co-evaporation.

[0077] In some embodiments, the material of the doping layer 11 in the electron transport layer 9 includes lithium 8-hydroxyquinolate (Liq).

[0078] By adjusting the doping ratio (thickness ratio) of the Liq doping layer 11 on the side of the electron transport layer 9 close to the second electrode layer (cathode) 3, the electron injection rate can be more effectively adjusted and the direct diffusion of metal ions into the light-emitting layer 4 can be prevented.

[0079] Moreover, by combining the hole injection layer 5 material provided in the embodiments of the present application with the electron transport layer 9 material containing Liq with different thickness ratios, and by simultaneously optimizing the doping ratios of the doping materials in the hole injection layer 5 and the electron transport layer 9, the carrier injection rate can reach the optimal equilibrium state, maximizing the exciton recombination efficiency, and thus maximizing the device luminescence efficiency and stability.

[0080] Please refer to Figure 5 and Figure 6 , Figure 5 which is a schematic diagram of carrier migration of another organic light-emitting device provided in the embodiments of the present application. Figure 6 which is a schematic diagram of carrier migration of another organic light-emitting device provided in the embodiments of the present application.

[0081] Continuing Figure 3 and Figure 4 , as Figure 4 shown, by doping the P-type dopant 7 in the hole injection layer (HIL) 5, although the HOMO energy level of the hole injection layer (HIL) 5 is reduced and the injected carriers reach relative equilibrium, the number of exciton recombinations in the light-emitting layer 4 is not large enough, resulting in insufficient device efficiency. As Figure 5 shown, by adjusting the doping ratio (thickness ratio) of the doping layer 11 in the electron transport layer 9, the LUMO energy level of the electron transport layer (ETL) 9 is reduced, thereby increasing the electron injection rate. As Figure 6As shown, the doping ratio of the P-type dopant 7 in the hole injection layer (HIL) 5 is adjusted again to change the injection barrier, so that the hole injection rate and the electron injection rate reach the optimal balance state, thereby maximizing the exciton binding and maximizing the light emission efficiency and stability of the device.

[0082] In some embodiments, the organic light-emitting device 1 is an OLED device; in particular, the organic light-emitting device 1 may be an s-OLED device, but is not limited thereto.

[0083] In some embodiments, the organic light-emitting device 1 further includes an upper light capping layer (Capping layer, CPL) 12 for improving the light extraction efficiency.

[0084] In some embodiments, functional layers such as a hole transport layer, an electron injection layer, an electron blocking layer, or a hole blocking layer may also be provided in the organic light-emitting device 1 as needed, but are not limited thereto.

[0085] In some embodiments, the hole injection layer 5, the hole transport layer, and the light-emitting layer 4 are prepared by a solution method, and other film layers may be prepared by an evaporation method, but are not limited thereto.

[0086] In the embodiments of the present application, the influence of the doping ratios of the doping materials in the hole injection layer 5 and the electron transport layer 9 on the performance of the OLED device is studied through comparative experiments, and the results are as Figures 9 to 12 shown.

[0087] Please refer to Figure 9 and Figure 10 , Figure 9 which is a schematic diagram of the results of CIEy and BI of the comparative device OLED-Ref1, the experimental device OLED-1, and the experimental device OLED-2 provided by the embodiments of the present application. Figure 10 which is a schematic diagram of the results of the change of the current efficiency (Current Efficiency, CE) of the comparative device OLED-Ref1, the experimental device OLED-1, and the experimental device OLED-2 provided by the embodiments of the present application with the current density.

[0088] It can be understood that CIEy is a parameter in the International Commission on Illumination (CIE) chromaticity system, which is used to represent the chromaticity coordinate of a color in the Y-axis direction. BI is the ratio of CE to CIEy and is an index used to evaluate the efficiency of a device.

[0089] Among them, the hole injection layer of the comparative device OLED-Ref1 is not doped with a P-type dopant, the hole injection layer of the experimental device OLED-1 is doped with a P-type dopant with a mass fraction of 8%, and the hole injection layer of the experimental device OLED-2 is doped with a P-type dopant with a mass fraction of 10%. The other structures of the comparative device OLED-Ref1, the experimental device OLED-1, and the experimental device OLED-2 are the same.

[0090] In some embodiments, the thickness of the hole injection layer in the comparative device OLED-Ref1, the experimental device OLED-1, and the experimental device OLED-2 is about 25 nanometers, and the thickness of the electron output layer is about 30 nanometers.

[0091] From Figure 9 and Figure 10 it can be seen that when the chromaticity coordinate CIEy of the light emitted by the experimental device OLED-1 and the experimental device OLED-2 in the Y-axis direction is in the range of 0.039 to 0.046, the ratio of the current efficiency of the experimental device OLED-1 and the experimental device OLED-2 to the chromaticity coordinate is greater than 160 and less than 210. When the current density of the experimental device OLED-1 and the experimental device OLED-2 is 10 mA / cm 2 ², the current efficiency of the experimental device OLED-1 and the experimental device OLED-2 is greater than 7 cd / A and less than 10 cd / A.

[0092] Compared with the comparative device OLED-Ref1, after the hole injection layer in the experimental devices OLED-1 and OLED-2 is doped with a P-type dopant (such as a dopant of model PD05), the BI value and CE value of the experimental devices OLED-1 and OLED-2 are both improved. Compared with the comparative device OLED-Ref1, when the doping concentration of the P-type dopant in the hole injection layer is 8%, the BI of the device increases by about 43%, and the J10 voltage increases by about 1 V; when the doping concentration of the P-type dopant in the hole injection layer is 10%, the BI of the device increases by about 27%, and the J10 voltage increases by about 0.7 V.

[0093] When the doping concentration of the P-type dopant in the hole injection layer exceeds 10%, the device efficiency and lifetime will show a downward trend because doping too much P-type dopant changes the HOMO energy level, makes the hole injection rate too fast, leads to serious exciton imbalance, and causes a large amount of holes to accumulate at the interface of the light-emitting layer, accelerating the deterioration of the device efficiency and lifetime.

[0094] It can be understood that J10 represents a current density of 10 mA / cm 2 ², and the corresponding voltage at this time is an important indicator for evaluating power consumption.

[0095] Therefore, when the doping concentration of the P-type dopant in the hole injection layer is controlled within the range of 8% to 10%, while increasing the BI of the device, a lower increase in J10 voltage can be maintained, which is beneficial to improving the light-emitting efficiency and stability of the device.

[0096] Please refer to Figure 11 and Figure 12 , Figure 11 which are schematic diagrams of the CIEy and BI results of the comparative device OLED-Ref2, experimental devices OLED-3, OLED-4, and OLED-5 provided by the embodiments of the present application. Figure 12 which are schematic diagrams of the results of the current efficiency of the comparative device OLED-Ref2, experimental devices OLED-3, OLED-4, and OLED-5 varying with the current density provided by the embodiments of the present application.

[0097] Among them, in the electron transport layer of the comparative device OLED-Ref2, Liq is not doped. In the electron transport layer of the experimental device OLED-3, the thickness ratio of the electron transport main body part (such as the material of the LG1035 model) to the Liq doping layer is 5:5 (that is, the thickness ratio of the Liq doping layer in the electron transport layer is 50%). In the electron transport layer of the experimental device OLED-4, the thickness ratio of the electron transport main body part to the Liq doping layer is 4:6 (that is, the thickness ratio of the Liq doping layer in the electron transport layer is 60%). In the electron transport layer of the experimental device OLED-5, the thickness ratio of the electron transport main body part to the Liq doping layer is 3:7 (that is, the thickness ratio of the Liq doping layer in the electron transport layer is 70%).

[0098] In some embodiments, the thickness of the hole injection layer of the comparative device OLED-Ref2, experimental devices OLED-3, OLED-4, and OLED-5 is about 25 nanometers, and the thickness of the electron output layer is about 30 nanometers.

[0099] From Figure 11 and Figure 12It can be seen that by changing the thickness ratio of the electron transport main body part to the Liq doping layer in the electron transport layer, the efficiency difference between devices is relatively obvious. Among them, when the thickness ratio of the electron transport main body part to the Liq doping layer in the electron transport layer is 5:5 and 4:6, although the efficiencies of the experimental devices OLED-3 and OLED-4 are improved more, the roll-off is faster and the device lifetime will deteriorate; when the thickness ratio of the electron transport main body part to the Liq doping layer in the electron transport layer is 3:7, the Liq content increases and the J10 voltage decreases by about 0.19V, but the device efficiency does not increase significantly. Considering the efficiency and lifetime of the device comprehensively, the thickness ratio of the electron transport main body part to the Liq doping layer in the electron transport layer is more suitable in the range of 3:7 to 5:5.

[0100] In the embodiments of the present application, by matching the hole injection layer material provided in the embodiments of the present application with the electron transport layer material containing Liq with different thickness ratios, and by simultaneously optimizing the doping ratios of the doping materials in the hole injection layer and the electron transport layer, the carrier injection rate can reach the optimal equilibrium state, which can maximize the exciton recombination efficiency, thereby maximizing the device luminescence efficiency and stability. It can be understood that the improvement of the device stability represents the improvement of the service life.

[0101] As Figure 13 shown, the embodiments of the present application also provide a preparation method of the organic light-emitting device 1 in the foregoing embodiments, and the preparation method includes steps S1 to S3.

[0102] S1: Form a first electrode layer.

[0103] In some embodiments, the first electrode layer is an anode layer, and the material of the first electrode layer is selected from IZO / Ag / IZO, but is not limited thereto.

[0104] S2: Sequentially form a hole injection layer and a light-emitting layer on one side of the first electrode layer; the material of the hole injection layer includes a hole injection main body part and a P-type dopant doped in the hole injection main body part, the P-type dopant includes an electron-withdrawing group, and the mass percentage range of the P-type dopant in the hole injection layer is 8% to 10%.

[0105] In some embodiments, step S2 includes:

[0106] Adopt a solution method to sequentially form a hole injection layer and a light-emitting layer on one side of the first electrode layer, and the solution method includes at least one of a spin coating process, a blade coating process, and an inkjet printing process.

[0107] In some embodiments, step S2 further includes:

[0108] The electron transport layer is formed on one side of the light-emitting layer facing away from the hole injection layer by a solution method. Among them, the electron transport layer includes an electron transport main body part and a doping layer located on the side of the electron transport main body part facing away from the light-emitting layer. In the electron transport layer, the thickness percentage range of the doping layer is 50% to 70%.

[0109] In some embodiments, the material of the hole injection layer is selected from small molecule crosslinking materials or mixed small molecule crosslinking materials, which is beneficial to improving the film-forming performance.

[0110] For the relevant descriptions of the hole injection layer and the electron transport layer, reference can be made to the descriptions of the foregoing embodiments, and details are not repeated here.

[0111] S3: A second electrode layer is formed on one side of the light-emitting layer facing away from the hole injection layer.

[0112] In some embodiments, the second electrode layer is a cathode layer, and the material of the second electrode layer includes Yb / Ag, but is not limited thereto.

[0113] It can be understood that the organic functional layers between the first electrode layer and the second electrode layer can all be prepared by a solution method.

[0114] In the embodiments of the present application, since the organic functional layers between the first electrode layer and the second electrode layer are prepared by a solution method, the obtained organic light-emitting device 1 is an s-OLED device. This preparation method has the advantages of simple process, low cost, and high material utilization rate. Moreover, by adjusting the doping ratio of the P-type dopant in the hole injection layer, the hole injection rate can be adjusted. At the same time, by adjusting the thickness ratio of the doping layer in the electron transport layer, the electron injection rate can be adjusted. Therefore, by simultaneously optimizing the doping ratios of the doping materials in the hole injection layer and the electron transport layer to make the carrier injection rate reach the optimal equilibrium state, the exciton recombination efficiency can be maximized, thereby maximizing the device luminescence efficiency and stability.

[0115] Such as Figure 14 As shown, the embodiments of the present application also provide a display device 13, and the display device 13 includes the organic light-emitting device 1 described in the above embodiments.

[0116] In some embodiments, the display device 13 further includes an array substrate 14, and the organic light-emitting device 1 is disposed on the array substrate 14. A driving circuit is provided in the array substrate 14, and the driving circuit is electrically connected to the first electrode layer 2 of the organic light-emitting device 1 for driving the organic light-emitting device 1 to emit light.

[0117] In some embodiments, the display device 13 further includes a packaging layer, and the packaging layer covers the organic light-emitting device 1 to prevent the organic light-emitting device 1 from being eroded by water and oxygen or damaged by external forces.

[0118] In the embodiments of the present application, since the luminous efficiency and stability of the organic light emission have been improved, the luminous efficiency and service life of the display device 13 have also been improved.

[0119] In the description of the present application, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, "a plurality of" means two or more unless otherwise specifically defined.

[0120] In the above embodiments, the descriptions of the respective embodiments have their own emphases. For the parts not detailed in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0121] Among the embodiments, implementation manners and related technical features of the present application, they can be combined and replaced with each other without conflict.

[0122] The above are only the preferred embodiments of the present application and do not impose any form of limitation on the present application. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application still fall within the scope of the technical solution of the present application.

Claims

1. An organic light-emitting device, characterized in that: The method comprises a first electrode layer, a second electrode layer, a light-emitting layer and a hole injection layer; the first electrode layer and the second electrode layer are arranged opposite to each other, the light-emitting layer is located between the first electrode layer and the second electrode layer, and the hole injection layer is located between the first electrode layer and the light-emitting layer; The hole injection layer includes a hole injection body and a P-type dopant doped in the hole injection body, the P-type dopant includes an electron-withdrawing group, and the mass percentage of the P-type dopant in the hole injection layer ranges from 8% to 10%.

2. The organic light-emitting device according to claim 1, characterized in that: The electron withdrawing group includes at least one of fluorine and boron.

3. The organic light-emitting device according to claim 1, characterized in that: The material of the hole injection body includes a cross-linking group, and the cross-linking group includes at least one of a styrene group, a phenylethynyl group, or a benzocyclobutene group.

4. The organic light-emitting device according to any one of claims 1 to 3, characterized in that: The bandgap width of the hole injection layer ranges from 2.8 eV to 2.9 eV.

5. The organic light-emitting device according to claim 1, characterized in that: The organic light emitting device further comprises an electron transport layer located between the light emitting layer and the second electrode layer; The electron transport layer includes an electron transport main body and a doping layer, wherein the doping layer covers a side of the electron transport main body close to the second electrode layer; in the electron transport layer, the thickness percentage of the doping layer ranges from 50% to 70%.

6. The organic light-emitting device according to claim 1, characterized in that: The organic light-emitting device further comprises an electron transport layer located between the light-emitting layer and the second electrode layer; the electron transport layer comprises a first sub-electron transport layer and a second sub-electron transport layer stacked, the first sub-electron transport layer is located between the light-emitting layer and the second electrode layer, and the second sub-electron transport layer is located between the first sub-electron transport layer and the second electrode layer; The second sub-electron transport layer includes an electron transport main body and a doping layer, wherein the doping layer covers a side of the electron transport main body close to the second electrode layer; the electron transport main body and the first sub-electron transport layer are made of the same material, and in the second sub-electron transport layer, the thickness percentage of the doping layer ranges from 50% to 80%.

7. The organic light-emitting device according to claim 5 or 6, characterized in that: The material of the doping layer includes 8-hydroxyquinoline lithium.

8. The organic light-emitting device according to claim 1, characterized in that: When the chromaticity coordinates of the light emitted by the organic light-emitting device in the Y-axis direction are in the range of 0.039 to 0.046, the ratio of the current efficiency of the organic light-emitting device to the chromaticity coordinates is greater than 160 and less than 210.

9. The organic light emitting device according to claim 1, characterized in that: When the current density of the organic light emitting device is 10 mA / cm 2 When the current efficiency of the organic light-emitting device is greater than 7 cd / A and less than 10 cd / A.

10. A display device, characterized in that: An organic light-emitting device comprising any one of claims 1 to 9.

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