Light-emitting device, preparation method thereof and display device

Abstract

The invention discloses a light-emitting device and a preparation method thereof and a display device, a light-emitting layer comprises a host material, a sensitizer and a fluorescent object material, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent object material is high, and the light-emitting device aims at solving the problems that an existing light-emitting device is low in efficiency and short in service life. The invention further discloses a preparation method of the light-emitting device, the light-emitting layer is formed on the surface of the first electrode through linear source vacuum evaporation, the host material, the sensitizer and the fluorescent object material are placed in the corresponding evaporation sources respectively, the evaporation sources of the fluorescent object material are scanned preferentially, the evaporation rates of the three evaporation sources are adjusted, and the light-emitting device is obtained. The doping concentration of the sensitizer and the fluorescent guest material is gradually increased or decreased along with the increase of the thickness of the light-emitting layer; and evaporating a second electrode on the surface of the light-emitting layer.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a light-emitting device and a method for preparing the same, and a display device. Background Art

[0002] Organic light emitting devices (OLEDs) are active light emitting devices with the advantages of light emission, ultra-thinness, wide viewing angle, high brightness, high contrast, low power consumption, and extremely high response speed. They have gradually become the next generation display technology with great development prospects. Generally, OLEDs include an anode, a cathode, and an organic light emitting layer arranged between the anode and the cathode. The principle of light emission is to inject holes and electrons from the anode and the cathode into the light emitting layer respectively. When electrons and holes meet in the light emitting layer, they recombine in the light emitting layer to generate excitons. These excitons emit light while changing from an excited state to a ground state.

[0003] At present, red and green devices in commercial OLED devices use phosphorescent dopant (dopant). However, in recent years, the performance iteration of phosphorescent dopant has slowed down, and the efficiency improvement of phosphorescent devices has reached a bottleneck. By phosphorescently sensitizing narrow-band fluorescent materials, high external quantum efficiency can be achieved while achieving a narrow emission spectrum, achieving higher luminous efficiency in top-emitting devices, and thus achieving a breakthrough in efficiency.

[0004] In order to achieve efficiency improvement in phosphorescence-sensitized fluorescence, narrow-band fluorescent materials need to be used. Currently, these materials are all boron-containing multiple resonance delayed fluorescent materials. However, when the doping concentration of fluorescent guests in the sensitized device increases, the fluorescent guests aggregate, resulting in a significant loss in the efficiency and life of the device. Summary of the invention

[0005] In view of this, the present application provides a light-emitting device and a method for preparing the same, and a display device, aiming to improve the problems of low efficiency and short life of existing light-emitting devices.

[0006] According to a first aspect of an embodiment of the present application, there is provided a light emitting device, comprising a first electrode, a second electrode and a light emitting layer disposed between the first electrode and the second electrode;

[0007] The light-emitting layer comprises: a host material, a sensitizer and a fluorescent guest material;

[0008] The light-emitting layer has a sensitization region, in which the doping concentration of the sensitizer gradually increases; the doping concentration of the fluorescent guest material gradually decreases; the doping concentration of the sensitizer is greater than the doping concentration of the fluorescent guest material;

[0009] The light-emitting layer has a fluorescence rising zone, in which the doping concentration of the sensitizer gradually decreases; the doping concentration of the fluorescent guest material gradually increases; and the doping concentration of the sensitizer is greater than the doping concentration of the fluorescent guest material.

[0010] Optionally, in some embodiments of the present application, in the sensitivity rise zone, the sensitizer has at least one maximum doping concentration located in the first exciton region of the light-emitting layer; in the fluorescence rise zone, the fluorescent guest material has at least one minimum doping concentration located in the first exciton region of the light-emitting layer, and the exciton concentration of the first exciton region is higher than the concentration of other exciton regions in the light-emitting layer.

[0011] Optionally, in some embodiments of the present application, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material ranges from 1 to 100.

[0012] Optionally, in some embodiments of the present application, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material ranges from 2 to 100.

[0013] Optionally, in some embodiments of the present application, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material ranges from 5 to 100.

[0014] Optionally, in some embodiments of the present application, the thickness of the light-emitting layer is m, and the first exciton region is a region with a thickness of 0.125m to 0.375m of the light-emitting layer along the direction from the first electrode to the second electrode.

[0015] Optionally, in some embodiments of the present application, the main material includes one or both of an N-type main material and a P-type main material.

[0016] Optionally, in some embodiments of the present application, the sensitizer includes at least one of a phosphorescent material utilizing triplet excitons and a thermally activated delayed fluorescent material.

[0017] Optionally, in some embodiments of the present application, the luminescence spectrum peak of the fluorescent guest material is located at 400-700 nm, and the spectrum half-peak width is less than 60 nm.

[0018] Optionally, in some embodiments of the present application, the first electrode is an anode, and the second electrode is a cathode.

[0019] According to a second aspect of an embodiment of the present application, a method for preparing a light-emitting device is provided, comprising the following steps:

[0020] providing a first electrode;

[0021] Vacuum-deposit a light-emitting layer on the surface of the first electrode:

[0022] The host material, the sensitizer and the fluorescent guest material are placed in corresponding evaporation sources respectively, the evaporation source of the fluorescent guest material is scanned preferentially, and the evaporation rates of the three evaporation sources are adjusted so that the doping concentration of the sensitizer and the fluorescent guest material gradually increases or decreases as the thickness of the light-emitting layer increases;

[0023] A second electrode is evaporated on the surface of the light-emitting layer.

[0024] In a third aspect, an embodiment of the present application provides a display device, comprising the aforementioned light-emitting device.

[0025] The embodiment of the present application provides a light-emitting device. By controlling the doping concentration of a sensitizer and the doping concentration of a fluorescent guest material, in a sensitivity rise region, the doping concentration of the sensitizer gradually increases, and the doping concentration of the fluorescent guest material gradually decreases; the doping concentration of the sensitizer is greater than the doping concentration of the fluorescent guest material, which helps to reduce the loss of efficiency and life due to aggregation of the fluorescent guest material, thereby improving the problems of low efficiency and short life of existing light-emitting devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 is a schematic diagram of the structure of a light-emitting device provided in some embodiments of the present application;

[0028] Figure 2 is a schematic diagram of the structure of a light-emitting device provided in some other embodiments of the present application;

[0029] Figure 3 is a schematic diagram of the structure of a light-emitting device provided in some other embodiments of the present application;

[0030] Figure 4 is a schematic structural diagram of a light-emitting device provided in some other embodiments of the present application;

[0031] Figure 5 is a schematic structural diagram of a light-emitting device provided in some other embodiments of the present application;

[0032] Figure 6 is a flow chart of the evaporation process of the light-emitting device provided in some embodiments of the present application;

[0033] Figure 7is a schematic diagram of the evaporation process of the light-emitting device provided in some embodiments of the present application;

[0034] Figure 8 is the concentration variation curve of Example 1 of the present application and Comparative Example 1 in the first exciton region;

[0035] Fig. 9 is the concentration variation curve of Example 2 of the present application and Comparative Example 2 in the first exciton region;

[0036] Fig.10 It is the concentration variation curve of Example 3 of the present application and Comparative Example 3 in the first exciton region.

[0037] Reference numerals:

[0038] 100. Light emitting device;

[0039] 101. First electrode; 102. Hole injection layer; 103. Hole transport layer; 104. Electron blocking layer; 105. Light-emitting layer; 106. Hole blocking layer; 107. Electron transport layer; 108. Electron injection layer; 109. Second electrode; 110. Substrate; 111. Covering layer. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0042] In this application, unless otherwise stated, directional words such as "upper" and "lower" generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. In addition, in the description of this application, the term "including" means "including but not limited to". The terms first, second, third, etc. are used only as labels and do not impose numerical requirements or establish an order.

[0043] In this application, "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0044] In the present application, "at least one" means one or more, and "plurality" means two or more. "One or more", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0045] In the present application, when a layer is formed "on" another layer, the so-called "on" is a broad concept, which may indicate that the formed another layer is adjacent to the certain layer, or may indicate that there are other spacing structural layers between the another layer and the certain layer. For example, when a second electrode is formed "on" the first carrier functional layer, the so-called "on" may indicate that the formed second electrode is adjacent to the first carrier functional layer, or may indicate that there are other spacing structural layers between the second electrode and the first carrier functional layer, such as a light-emitting layer.

[0046] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0047] OLED is a self-luminous device. By sandwiching a functional layer between a pair of electrodes and applying voltage, the electrons injected from the electron transport layer and the holes injected from the hole transport layer recombine in the light-emitting layer to form excitons, and the excitons emit visible light when they return to the ground state. Most of the current organic electroluminescent devices use the host-guest uniform doping technology, but in mass production, due to the certain distribution of film thickness on the substrate, there is usually a periodic change of ±50%, so there will be concentration fluctuations, affecting the luminous efficiency and service life of the light-emitting device.

[0048] In view of this, according to a first aspect of the present application, there is provided a light-emitting device, comprising a first electrode, a second electrode, and a light-emitting layer disposed between the first electrode and the second electrode;

[0049] The light-emitting layer includes: a host material, a sensitizer and a fluorescent guest material;

[0050] Among them, the light-emitting layer has a sensitivity rise zone, in which the doping concentration of the sensitizer gradually increases; the doping concentration of the fluorescent guest material gradually decreases; the doping concentration of the sensitizer is greater than the doping concentration of the fluorescent guest material; the light-emitting layer has a fluorescence rise zone, in which the doping concentration of the sensitizer gradually decreases; the doping concentration of the fluorescent guest material gradually increases; the doping concentration of the sensitizer is greater than the doping concentration of the fluorescent guest material.

[0051] In some embodiments of the present application, in the sensitivity rise zone, the sensitizer has at least one maximum doping concentration located in the first exciton region of the light-emitting layer; in the fluorescence rise zone, the fluorescent guest material has at least one minimum doping concentration located in the first exciton region of the light-emitting layer, and the exciton concentration in the first exciton region is higher than the concentration in other exciton regions in the light-emitting layer.

[0052] It should be noted that, because the doping concentration of the sensitizer gradually increases and the doping concentration of the fluorescent guest material gradually decreases in the sensitivity rise region, the sensitivity rise region can also be called the fluorescence drop region. Similarly, because the doping concentration of the sensitizer gradually decreases and the doping concentration of the fluorescent guest material gradually increases in the fluorescence rise region, the fluorescence rise region can also be called the sensitivity drop region.

[0053] It should be noted that there can be multiple maximum doping concentrations of the sensitizer, and at least one maximum doping concentration is required to be located in the first exciton region of the light-emitting layer, which helps to ensure that in the first exciton region, the doping concentration of the sensitizer first increases and then decreases with the increase of the thickness of the light-emitting layer. Similarly, there can be multiple minimum doping concentrations of the fluorescent guest material, and at least one minimum doping concentration of the fluorescent guest material is required to be located in the first exciton region of the light-emitting layer, which helps to ensure that in the first exciton region, the doping concentration of the fluorescent guest material first decreases and then increases with the increase of the thickness of the light-emitting layer.

[0054] In some embodiments of the present application, the doping concentration of the sensitizer increases as the thickness of the light-emitting layer increases from the first electrode to the second electrode, and the doping concentration of the fluorescent guest material and the sensitizer gradually increases or decreases as the thickness of the light-emitting layer increases.

[0055] In some embodiments of the present application, as the thickness of the light-emitting layer increases from the first electrode to the second electrode, the doping concentration of the sensitizer changes in a W-type, and the doping concentration of the sensitizer changes in an M-type.

[0056] In some embodiments of the present application, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material ranges from 1 to 100.

[0057] In some embodiments of the present application, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material ranges from 2 to 100.

[0058] In some embodiments of the present application, the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material ranges from 5 to 100.

[0059] In some embodiments of the present application, the thickness of the light-emitting layer is m, and the first exciton region is a region with a thickness of 0.125m to 0.375m in the direction from the first electrode to the second electrode of the light-emitting layer.

[0060] In some embodiments of the present application, the first electrode and the second electrode are electrodes known in the art for light-emitting devices, for example, they may independently include but are not limited to doped metal oxide electrodes, composite electrodes, graphene electrodes, carbon nanotube electrodes, metal single-substance electrodes or alloy electrodes. The material of the doped metal oxide electrode may include but is not limited to one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), magnesium-doped zinc oxide (MZO), aluminum-doped magnesium oxide (AMO), and cadmium-doped zinc oxide. The composite electrode is an electrode formed by stacking two or more layers of conductive materials, such as AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, Ca / Al, LiF / Ca, LiF / Al, BaF2 / Al, CsF / Al, CaCO3 / Al, BaF2 / Ca / Al, etc., where " / " represents a stacked structure, for example, AZO / Ag / AZO represents a composite electrode including a sequentially stacked AZO layer, an Ag layer, and an AZO layer. The material of the metal single substance electrode may include, but is not limited to, one or more of Ag, Ni, Pt, Au, Ir, Cu, Mo, Al, Ca, Mg, and Ba. Alloy electrodes include, but are not limited to, Au:Mg alloy electrodes and Ag:Mg alloy electrodes.

[0061] In some embodiments of the present application, the first electrode is an anode, and the anode is an electrode with a relatively high work function, such as but not limited to a doped metal oxide electrode with a relatively high work function, a metal single substance electrode with a relatively high work function, and a carbon nanotube electrode. The metal single substance electrode with a relatively high work function can be selected from but not limited to Ni, Pt, Au, Ag, Ir, etc.

[0062] In some embodiments of the present application, the second electrode is a cathode, and the cathode is an electrode with a relatively low work function, for example, it may include but is not limited to a metal single substance electrode with a relatively low work function, a composite electrode with a relatively low work function, and an alloy electrode with a relatively low work function. The metal single substance electrode with a relatively low work function may be Ca, Ba, Al, Mg, etc. The composite electrode with a relatively low work function may be Ca / Al, LiF / Ca, LiF / Al, BaF2 / Al, CsF / Al, CaCO3 / Al, BaF2 / Ca / Al, etc. The alloy electrode with a relatively low work function may be Au:Mg and Ag:Mg, etc.

[0063] In some embodiments of the present application, one or more layers of a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer, and an electron injection layer may be selectively included between the first electrode and the second electrode, and the above-mentioned hole injection layer, hole transport layer, electron blocking layer, hole blocking layer, electron transport layer, and electron injection layer are arranged in sequence from the first electrode to the second electrode.

[0064] Reference Figure 1 In some embodiments of the present application, the light-emitting device 100 includes a first electrode 101, a light-emitting layer 105, and a second electrode 109 that are stacked in sequence.

[0065] Reference Figure 2 In some embodiments of the present application, the light-emitting device 100 includes a first electrode 101, a hole transport layer 103, a light-emitting layer 105, an electron transport layer 107 and a second electrode 109 which are stacked in sequence.

[0066] Reference Figure 3 In some embodiments of the present application, the light-emitting device 100 includes a first electrode 101, a hole injection layer 102, a hole transport layer 103, a light-emitting layer 105, an electron transport layer 107, an electron injection layer 108 and a second electrode 109 stacked in sequence.

[0067] Reference Figure 4 In some embodiments of the present application, the light-emitting device 100 includes a first electrode 101, a hole injection layer 102, an electron blocking layer 104, a light-emitting layer 105, a hole blocking layer 106, an electron injection layer 108 and a second electrode 109 which are stacked in sequence.

[0068] Reference Figure 5 In some embodiments of the present application, the light-emitting device 100 includes a substrate 110, a first electrode 101, a hole injection layer 102, a hole transport layer 103, an electron blocking layer 104, a light-emitting layer 105, a hole blocking layer 106, an electron transport layer 107, an electron injection layer 108, a second electrode 109 and a covering layer 111 stacked in sequence.

[0069] In some embodiments of the present application, the light-emitting layer 105 includes: a host material, a fluorescent guest material, and a sensitizer. The host material, the fluorescent guest material, and the sensitizer can be formed by evaporation, and the host material, the fluorescent guest material, and the sensitizer are uniformly distributed in the light-emitting layer 105. The host material can play a dispersing role, separating the sensitizer and the fluorescent guest material; and the carrier transport performance can be balanced by adjusting the types of the host material and the sensitizer. Of course, the host material and the sensitizer can both be electron transport materials or hole transport materials, and the host material and the sensitizer can also be different charge transport materials, for example, the host material is an electron transport material, the sensitizer is a hole transport material, or the host material is a hole transport material and the sensitizer is an electron transport material.

[0070] In some embodiments of the present application, the main body material includes one or both of an N-type main body material and a P-type main body material.

[0071] In some embodiments of the present application, the main body material is selected from N-type main body material, including but not limited to the following structure:

[0072]

[0073] In some embodiments of the present application, the main body material is a P-type main body material, including but not limited to the following structures:

[0074]

[0075] In some embodiments of the present application, the main body material is a combination of the above-mentioned N-type main body material and the P-type main body material.

[0076] In some embodiments of the present application, the sensitizer includes at least one of a phosphorescent material utilizing triplet excitons and a thermally activated delayed fluorescent material.

[0077] In some embodiments of the present application, the sensitizer includes but is not limited to the following structure:

[0078]

[0079] In some embodiments of the present application, the peak of the luminescent spectrum of the fluorescent guest material is located at 400-700 nm, and the half-peak width of the spectrum is less than 60 nm.

[0080] In some embodiments of the present application, the fluorescent guest material includes but is not limited to the following structures:

[0081]

[0082] In some embodiments of the present application, the doping concentration of the host material in the light-emitting layer 105 is 86.5%-97.9%, and the doping concentration of the host material is the ratio of the mass of the host material to the sum of the mass of the host material, the fluorescent guest material and the sensitizer;

[0083] The doping concentration of the fluorescent guest material is 0.1%-1.5%, and the doping concentration of the fluorescent guest material is the ratio of the mass of the fluorescent guest material to the sum of the mass of the host material, the fluorescent guest material, and the sensitizer;

[0084] The doping concentration of the sensitizer is 1%-15%, and the doping concentration of the sensitizer is the ratio of the mass of the sensitizer to the sum of the mass of the host material, the fluorescent guest material and the sensitizer.

[0085] In some embodiments of the present application, the doping concentration of the host material in the light-emitting layer 105 is 88.8%-94.8%, the doping concentration of the fluorescent guest material is 0.2%-1.2%, and the doping concentration of the sensitizer is 5%-10%.

[0086] In some embodiments of the present application, the hole transport layer 103 is mainly used to reduce the hole injection barrier and improve the hole injection efficiency. Exemplarily, the material of the hole injection layer can be a material known in the art for the hole transport layer 103, for example, it can be selected from but not limited to 4,4'-N,N'-dicarbazolyl-biphenyl (CBP), poly [bis (4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA), N,N'-diphenyl-N,N'-bis (1-naphthyl) -1,1'-biphenyl-4,4"-diamine (α-NPD), N,N'-diphenyl-N,N'-bis (3-methylphenyl) -(1,1'-biphenyl) -4,4'-diamine (TPD), poly (N,N'-bis (4-butylphenyl) -N,N'-bis (phenyl) benzidine) (Poly-TPD), N,N '-bis(3-methylphenyl)-N,N'-bis(phenyl)-spiro(spiro-TPD), N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine (DNTPD), 4,4',4'-tri(N-carbazolyl)-triphenylamine (TCTA), 4,4',4'-tri(N-3-methylphenyl-N-phenylamino)triphenylamine (m-MTDATA), poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))] (TFB), poly(N-vinylcarbazole) (PVK) and its derivatives, N,N'-di(1-naphthyl)-N,N'-diphenylamine Phenyl-1,1'-biphenyl-4-4'-diamine (NPB), spiro-NPB, poly(phenylene vinylene) (PPV), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV), poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MOMO-PPV), 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-omeTAD), 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline] (TAPC), 1,3-bis(carbazol-9-yl)benzene (MC P), polyaniline, polypyrrole, poly(p-)phenylene vinylene, aromatic tertiary amine, polynuclear aromatic tertiary amine, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compound, N,N,N',N'-tetraarylbenzidine, PEDOT:PSS and its derivatives, polymethacrylate and its derivatives, poly(9,9-octylfluorene) and its derivatives, poly(spirofluorene) and its derivatives, doped graphene, undoped graphene, C60, doped or undoped NiO, doped or undoped MoO3, doped or undoped WO3, doped or undoped V2O5, doped or undoped P-type gallium nitride, doped or undoped CrO3, doped or undoped CuO. One or more.

[0087] In some embodiments of the present application, the hole transport layer 103 may be made of a carbazole material with relatively high hole mobility, and may be formed by an evaporation process during the process preparation stage.

[0088] In some embodiments of the present application, the electron blocking layer 104 is mainly used to block electrons and excitons generated in the light-emitting layer 105, and to transfer holes. The molecular formula of the material of the electron blocking layer 104 and the hole transport material in the light-emitting layer 105 can be the same or different.

[0089] In some embodiments of the present application, the hole blocking layer 106 is mainly used to block holes and excitons generated in the light-emitting layer, and to transport electrons.

[0090] In some embodiments of the present application, the material of the electron transport layer 107 is a material known in the art for the electron transport layer 107, for example, it can be selected from but not limited to one or more of inorganic electron transport materials and organic electron transport materials. Inorganic electron transport materials include but are not limited to doped metal oxide particles, undoped metal oxide particles, ceramic semiconductor materials, IIB-VIA semiconductor materials, IIIA-VA semiconductor materials, and IB-IIIA-VIA semiconductor materials. The metal oxide in the undoped metal oxide particles includes but is not limited to one or more of ZnO, TiO2, SnO2, ZrO2, and Ta2O5. The metal oxides in the doped metal oxides include but are not limited to one or more of ZnO, TiO2, SnO2, ZrO2, Ta2O5, and Al2O3. The doping elements in the doped metal oxides include but are not limited to one or more of Al, Mg, Li, Mn, Y, La, Cu, Ni, Zr, Ce, In, Ga, and Sn. For example, the doped metal oxides may be aluminum zinc oxide (AZO), lithium-doped zinc oxide (LZO), magnesium-doped zinc oxide (MZO), and tin-doped zinc oxide (Sn-ZnO). Ceramic semiconductor materials include but are not limited to barium titanate. IIB-VIA semiconductor materials include but are not limited to one or more of ZnS, ZnSe, and CdS. IIIA-VA semiconductor materials include but are not limited to one or more of InP and GaP. IB-IIIA-VIA semiconductor materials include but are not limited to one or more of CuInS and CuGaS.

[0091] In some embodiments of the present application, the electron transport layer 107 is mainly used to transport electrons. The material of the electron transport layer 107 includes an electron transport material and Liq doped together, and the doping mass ratio of the two is 10:1 to 1:1. The thickness of the electron transport layer 107 is between 10-50nm, and Liq can be selected from the material The electron transport material contains at least one

[0092] In some embodiments of the present application, the material of the electron transport layer 107 includes, but is not limited to, one or more of quinoxaline compounds, imidazole compounds, triazine compounds, fluorene-containing compounds, and hydroxyquinoline compounds.

[0093] In some embodiments of the present application, the material of the hole injection layer 102 can be a material known in the art for the hole injection layer 102, for example, it can be selected from but not limited to 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN), PEDOT, PEDOT:PSS, a derivative of PEDOT:PSS doped with s-MoO3 (PEDOT:PSS:s-MoO3), 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine (m-MTDATA), tetracyanoquinodimethane (F4-TCQN), copper phthalocyanine, nickel oxide, molybdenum oxide, tungsten oxide, vanadium oxide, molybdenum sulfide, tungsten sulfide and copper oxide. One or more.

[0094] In some embodiments of the present application, the electron injection layer 108 is mainly used to reduce the electron injection barrier and improve the electron injection efficiency. Exemplarily, the material of the electron injection layer 108 can be selected from but not limited to one or more combinations of materials such as Yb, Li, LiF, NaCl, CsF, Li2O, BaO, and Liq.

[0095] In some embodiments of the present application, the cover layer 111 may be selectively disposed on the side of the second electrode 109 away from the light-emitting layer 105. The cover layer 111 is used to cover the second electrode 109, mainly to improve light extraction efficiency and protect the second electrode 109.

[0096] In some embodiments of the present application, the thickness of the first electrode 101 is 60-150 nm.

[0097] In some embodiments of the present application, the thickness of the hole transport layer 103 is 20-150 nm.

[0098] In some embodiments of the present application, the thickness of the light emitting layer 105 is 10-60 nm.

[0099] In some embodiments of the present application, the thickness of the second electrode 109 is 10-110 nm.

[0100] In some embodiments of the present application, the thickness of the electron injection layer 108 is 0.1-10 nm.

[0101] In some embodiments of the present application, the thickness of the electron transport layer 107 is 10-60 nm.

[0102] In some embodiments of the present application, the thickness of the hole injection layer 102 is 5-100 nm.

[0103] In some embodiments of the present application, the thickness of the electron blocking layer 104 is 0-100 nm.

[0104] In some embodiments of the present application, the thickness of the hole blocking layer 106 is 0-10 nm.

[0105] In some embodiments of the present application, the thickness of the cover layer 111 is 0-150 nm.

[0106] It should be noted that the materials of each layer of the light emitting device 100 can be adjusted according to the light emitting requirements of the light emitting device 100 .

[0107] In some embodiments of the present application, the light-emitting device 100 further includes a substrate 110 , which is disposed on a side of the first electrode 101 away from the light-emitting layer 105 , or on a side of the second electrode 109 away from the light-emitting layer 105 .

[0108] In some embodiments of the present application, the substrate 110 may be a rigid substrate or a flexible substrate. The material of the substrate 110 may include but is not limited to one or more of glass, silicon wafer, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyamide and polyether sulfone.

[0109] It should be noted that the light emitting device 100 may be an upright light emitting device or an inverted light emitting device.

[0110] Second, refer to Figure 6 and Figure 7 The present invention provides a method for preparing a light-emitting device, comprising the following steps:

[0111] S100, providing a first electrode 101;

[0112] S200, vacuum evaporating the light-emitting layer 105 on the surface of the first electrode 101:

[0113] The host material, the sensitizer and the fluorescent guest material are placed in corresponding evaporation sources respectively, the evaporation source of the fluorescent guest material is scanned preferentially, and the evaporation rates of the three evaporation sources are adjusted so that the doping concentration of the sensitizer and the fluorescent guest material gradually increases or decreases as the thickness of the light-emitting layer increases;

[0114] S300 , vapor-depositing the second electrode 109 on the surface of the light-emitting layer 105 .

[0115] In some embodiments of the present application, the three evaporation sources correspond to an evaporation source of a host material, an evaporation source of a sensitizer, and an evaporation source of a fluorescent guest material, respectively.

[0116] In some embodiments of the present application, the evaporation method may be line source evaporation.

[0117] In some embodiments of the present application, point source evaporation is to place fluorescent guest materials, host materials and sensitizers in three point sources respectively, form films uniformly by rotating the substrate, and control the evaporation rate to achieve a gradual increase and decrease in doping concentration with the thickness of the light-emitting layer.

[0118] In some embodiments of the present application, the evaporation rate of the fluorescent guest material is The evaporation rate of the sensitizer is The rate ratio of the sensitizer to the fluorescent guest material is equal to the ratio of the doping ratio of the two in the light-emitting layer; the evaporation rate of the host material is And the rate ratio of the host material to the fluorescent guest material is equal to the ratio of the doping ratios of the two in the light-emitting layer.

[0119] In some embodiments of the present application, the line source evaporation is to place the fluorescent guest material, the host material and the sensitizer in three linear evaporation sources respectively, and form a film by scanning the evaporation source. The evaporation source of the fluorescent guest material is scanned first, forming a periodic doping concentration that gradually increases and decreases with the thickness of the light-emitting layer. At this time, the rate setting ratio of the three materials is the ratio of the average doping concentration of the three in the light-emitting layer. The rate of the fluorescent guest material is The rate ratio of the sensitizer to the fluorescent guest material is equal to the ratio of the doping ratios of the two in the light-emitting layer, and the rate ratio of the host material to the fluorescent guest material is equal to the ratio of the doping ratios of the two in the light-emitting layer.

[0120] The light-emitting device provided in the embodiment of the present application can achieve an efficiency improvement of ≥20% and a device life of ≥100%.

[0121] In a third aspect, an embodiment of the present application provides a display device, comprising the aforementioned light-emitting device.

[0122] In some embodiments of the present application, the display device can be any electronic product with a display function, including but not limited to smart phones, tablet computers, laptops, digital cameras, digital video cameras, smart wearable devices, smart weighing electronic scales, car displays, televisions or e-book readers, among which the smart wearable device can be, for example, a smart bracelet, a smart watch, a virtual reality (VR) helmet, etc.

[0123] The present application is described in detail below by means of specific examples, which are only partial examples of the present application and are not intended to limit the present application. The raw materials used in the following examples are all commercially available products unless otherwise specified.

[0124] Example 1

[0125] A light-emitting device is prepared by the following method:

[0126] HAT-CN was evaporated on the glass substrate and ITO / Ag / ITO anode (15nm / 110nm / 15nm) under vacuum conditions as a hole injection layer with a thickness of 10nm;

[0127] TAPC was evaporated on the hole injection layer as a hole transport layer with a thickness of 120 nm;

[0128] The same hole transport material as that in the light emitting layer is evaporated on the hole transport layer as an electron blocking layer with a thickness of 40 nm;

[0129] A green light emitting layer is evaporated on the electron blocking layer with a thickness of 40 nm;

[0130] Wherein, the main material in the light-emitting layer is: The fluorescent guest material is The sensitizer is The doping concentration of the sensitizer is 7%, and the doping concentration of the fluorescent guest material is 0.5%;

[0131] The light-emitting layer is gradient doped by three-source evaporation method, and the main material, sensitizer and fluorescent guest material are placed in the corresponding evaporation source respectively. The fluorescent guest material is scanned first and the rate is The rates of the host material and the sensitizer can be converted according to the fluorescent guest material;

[0132] A hole blocking layer is evaporated on the light-emitting layer with a thickness of 5 nm;

[0133] The electron transport material and Liq were evaporated on the hole blocking layer in a ratio of 5:1 to form an electron transport layer with a thickness of 30 nm.

[0134] CsF was evaporated on the electron transport layer as an electron injection layer with a thickness of 1 nm;

[0135] A cathode Mg / Ag alloy is evaporated on the electron injection layer to obtain a cathode with a thickness of 1.2nm / 12nm;

[0136] Packaging to obtain a light-emitting device.

[0137] Example 2

[0138] A light-emitting device is prepared by the following method:

[0139] HAT-CN was evaporated on the glass substrate and ITO / Ag / ITO anode (15nm / 110nm / 15nm) under vacuum conditions as a hole injection layer with a thickness of 10nm;

[0140] TAPC was evaporated on the hole injection layer as a hole transport layer with a thickness of 120 nm;

[0141] The same hole transport material as that in the light emitting layer is evaporated on the hole transport layer as an electron blocking layer with a thickness of 40 nm;

[0142] A green light emitting layer with a thickness of 40 nm is evaporated on the electron blocking layer; wherein the material selection in the light emitting layer is the same as that in Example 1, the doping concentration of the sensitizer is 7%, and the doping concentration of the fluorescent guest material is 1%; during the evaporation, the light emitting layer is gradient doped by a three-source evaporation method, wherein the main material, the sensitizer and the fluorescent guest material are placed in the corresponding evaporation source respectively, the fluorescent guest material is scanned first, and the evaporation speed of the evaporation source is adjusted according to the doping concentration;

[0143] A hole blocking layer is evaporated on the light-emitting layer with a thickness of 5 nm;

[0144] The electron transport material and Liq were evaporated on the hole blocking layer in a ratio of 5:1 to form an electron transport layer with a thickness of 30 nm.

[0145] CsF was evaporated on the electron transport layer as an electron injection layer with a thickness of 1 nm;

[0146] A cathode Mg / Ag alloy is evaporated on the electron injection layer to obtain a cathode with a thickness of 1.2nm / 12nm;

[0147] Packaging to obtain a light-emitting device.

[0148] Example 3

[0149] A light-emitting device is prepared by the following method:

[0150] HAT-CN was evaporated on the glass substrate and ITO / Ag / ITO anode (15nm / 110nm / 15nm) under vacuum conditions as a hole injection layer with a thickness of 10nm;

[0151] TAPC was evaporated on the hole injection layer as a hole transport layer with a thickness of 120 nm;

[0152] The same hole transport material as that in the light emitting layer is evaporated on the hole transport layer as an electron blocking layer with a thickness of 40 nm;

[0153] A green light emitting layer with a thickness of 40 nm is evaporated on the electron blocking layer, wherein the material selection in the light emitting layer is the same as that in Example 1, the doping concentration of the sensitizer is 10%, and the doping concentration of the fluorescent guest material is 1%; during evaporation, the light emitting layer is gradient doped by a three-source evaporation method, wherein the main material, the sensitizer and the fluorescent guest material are placed in the corresponding evaporation source respectively, the fluorescent guest material is scanned first, and the evaporation speed of the evaporation source is adjusted according to the doping concentration;

[0154] A hole blocking layer is evaporated on the light-emitting layer with a thickness of 5 nm;

[0155] The electron transport material and Liq were evaporated on the hole blocking layer in a ratio of 5:1 to form an electron transport layer with a thickness of 30 nm.

[0156] CsF was evaporated on the electron transport layer as an electron injection layer with a thickness of 1 nm;

[0157] A cathode Mg / Ag alloy is evaporated on the electron injection layer to obtain a cathode with a thickness of 1.2nm / 12nm;

[0158] Packaging to obtain a light-emitting device.

[0159] Comparative Example 1

[0160] A light emitting device, which is different from the first embodiment in that the evaporation source of the sensitizer is scanned preferentially.

[0161] Comparative Example 2

[0162] A light emitting device, which is different from the embodiment 2 in that the evaporation source of the sensitizer is scanned preferentially.

[0163] Comparative Example 3

[0164] A light emitting device, which is different from the third embodiment in that the evaporation source of the sensitizer is scanned preferentially.

[0165] Comparative Example 4

[0166] A light emitting device, which is different from the embodiment 1 in that a point source uniformly evaporated phosphorescent device is used, and the doping concentration is 7%.

[0167] Detection methods:

[0168] (1) Device efficiency: The light-emitting devices of the above-mentioned embodiment and the comparative example were subjected to a current density of 10 mA / cm 2 Under the conditions of , the current efficiency of the above device is tested;

[0169] (2) Device life: The light-emitting devices of the above-mentioned embodiment and the comparative example were subjected to a current density of 30 mA / cm 2 The time required for the brightness to decay to 97%.

[0170] The test results of the embodiment and the comparative example are shown in Table 1

[0171] Table 1

[0172] sample Device efficiency (%) Device life (%) Example 1 128％ 105％ Example 2 125％ 102％ Example 3 122％ 110％ Comparative Example 1 110％ 85％ Comparative Example 2 103％ 72％ Comparative Example 3 107％ 83％ Comparative Example 4 100％ 100％

[0173] Combining the test results of Examples 1-3, Comparative Example 4 and Table 1, it can be seen that the present application adopts a method of preferential scanning of the evaporation source of the fluorescent guest material, and adjusts the evaporation rate of different evaporation sources according to the doping concentration, so as to achieve the preparation in the first exciton concentration region, and the ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material is high, which solves the problem of low device efficiency and short life due to aggregation of fluorescent guest materials. In the embodiment of the present application, when the ratio of the concentration of the sensitizer to the concentration of the fluorescent guest material is ≥7, the efficiency of the prepared light-emitting device is ≥120%, and the device life is ≥100%; while Comparative Example 4 adopts a point source uniform evaporation method, and the efficiency and life of the obtained light-emitting device are both 100%.

[0174] Combined with Example 1, Comparative Example 1, Figure 8 From the test results in Table 1, it can be seen that in Example 1, the doping concentration of the sensitizer is 7%, and the doping concentration of the fluorescent guest material is 0.5%, that is, the ratio of the sensitizer concentration to the fluorescent guest material doping concentration is 14, and during evaporation, the evaporation source of the fluorescent guest material is scanned first, which can increase the efficiency of the light-emitting device by 28% and the life span by 5%. If the evaporation source of the sensitizer is scanned first during evaporation, the efficiency and life span of the light-emitting device will be significantly affected.

[0175] Combined with Example 2, Comparative Example 2, Fig. 9 From the test results in Table 1, it can be seen that in Example 2, the doping concentration of the sensitizer is 7%, and the doping concentration of the fluorescent guest material is 1%, that is, the ratio of the sensitizer concentration to the fluorescent guest material concentration is 7, and during evaporation, the evaporation source of the fluorescent guest material is scanned preferentially, which can increase the efficiency of the light-emitting device by 25% and the life by 2%, which is slightly lower than that of Example 1. If the evaporation source of the sensitizer is scanned preferentially during evaporation, the efficiency and life of the light-emitting device will be significantly affected.

[0176] Combined with Example 3, Comparative Example 3, Fig.10 From the test results of Table 1, it can be seen that in Example 3, the doping concentration of the sensitizer is 10%, and the doping concentration of the fluorescent guest material is 1%, that is, the ratio of the sensitizer concentration to the doping concentration of the fluorescent guest material is 10, and during evaporation, the evaporation source of the fluorescent guest material is scanned preferentially, which can increase the efficiency of the light-emitting device by 22% and the lifespan by 10%, which is helpful to improve the lifespan of the light-emitting device compared to increasing the doping concentration of the sensitizer.

[0177] The light-emitting device and its preparation method, and the display device provided in the embodiments of the present application are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A light emitting device, characterized in that: comprising a first electrode, a second electrode and a light-emitting layer disposed between the first electrode and the second electrode; The light-emitting layer comprises: a host material, a sensitizer and a fluorescent guest material; Wherein, the light-emitting layer includes a first exciton region, the sensitizer has two maximum doping concentrations, the fluorescent guest material has two minimum doping concentrations, and the first exciton region contains a maximum doping concentration of the sensitizer and a minimum doping concentration of the fluorescent guest material, so that along the direction from the first electrode to the second electrode, as the thickness of the light-emitting layer increases, the doping concentration of the sensitizer in the first exciton region first increases and then decreases, and the doping concentration of the fluorescent guest material in the first exciton region first decreases and then increases.

2. The light emitting device according to claim 1, characterized in that: The light-emitting layer has a sensitization rise zone, in which the doping concentration of the sensitizer gradually increases; the doping concentration of the fluorescent guest material gradually decreases; the doping concentration of the sensitizer is greater than the doping concentration of the fluorescent guest material; The light-emitting layer has a fluorescence rising zone, in which the doping concentration of the sensitizer gradually decreases; the doping concentration of the fluorescent guest material gradually increases; and the doping concentration of the sensitizer is greater than the doping concentration of the fluorescent guest material.

3. The light emitting device according to claim 2, characterized in that: In the sensitization region, the sensitizer has a maximum doping concentration located in the first exciton region of the light-emitting layer; In the fluorescence rising zone, the fluorescent guest material has a minimum doping concentration located in the first exciton region of the light-emitting layer, and the exciton concentration of the first exciton region is higher than the concentration of other exciton regions in the light-emitting layer.

4. The light emitting device according to claim 3, characterized in that: The thickness of the light-emitting layer is m, and the first exciton region is a region of the light-emitting layer with a thickness of 0.125 m to 0.375 m along the direction from the first electrode to the second electrode.

5. The light emitting device according to claim 3 or 4, characterized in that: The thickness of the light-emitting layer is 400 angstroms, and the first exciton region is a region of the light-emitting layer with a thickness of 50 angstroms to 150 angstroms along a direction from the first electrode to the second electrode.

6. The light emitting device according to claim 1, characterized in that: The ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material ranges from 1 to 100.

7. The light emitting device according to claim 6, characterized in that: The ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material ranges from 2 to 100.

8. The light emitting device according to claim 7, characterized in that: The ratio of the doping concentration of the sensitizer to the doping concentration of the fluorescent guest material ranges from 5 to 100.

9. The light emitting device according to claim 1, characterized in that: The main body material includes one or both of an N-type main body material and a P-type main body material.

10. The light emitting device according to claim 1, characterized in that: The sensitizer includes at least one of a phosphorescent material utilizing triplet excitons and a thermally activated delayed fluorescent material.

11. The light emitting device according to claim 1, characterized in that: The peak of the luminescent spectrum of the fluorescent guest material is located at 400-700nm, and the half-peak width of the spectrum is less than 60nm.

12. The light emitting device according to claim 1, characterized in that: The first electrode is an anode, and the second electrode is a cathode.

13. A method for preparing a light emitting device according to claim 1, characterized in that: The steps include: providing a first electrode; Vacuum-deposit a light-emitting layer on the surface of the first electrode: The host material, the sensitizer and the fluorescent guest material are placed in corresponding evaporation sources respectively, the evaporation source of the fluorescent guest material is scanned preferentially, and the evaporation rates of the three evaporation sources are adjusted so that the sensitizer has two maximum doping concentrations and the fluorescent guest material has two minimum doping concentrations, the light-emitting layer includes a first exciton region, the first exciton region contains a maximum doping concentration of the sensitizer and a minimum doping concentration of the fluorescent guest material, and along the direction from the first electrode to the second electrode, as the thickness of the light-emitting layer increases, the doping concentration of the sensitizer in the first exciton region first increases and then decreases, and the doping concentration of the fluorescent guest material in the first exciton region first decreases and then increases; A second electrode is evaporated on the surface of the light-emitting layer.

14. A display device, characterized in that: The invention comprises a light emitting device as claimed in any one of claims 1 to 12.

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