White-light organic light-emitting device and display device

Abstract

The invention discloses a white-light organic light-emitting device and a display device, the device comprises an anode, a cathode and an organic functional layer located between the anode and the cathode, and the organic functional layer comprises a hole transport layer, a light-emitting layer and an electron transport layer which are sequentially arranged from the anode to the cathode. The light-emitting layer comprises a blue light fluorescent layer (namely, a host material layer) and at least one phosphorescent light-emitting layer (namely, a guest material layer) of which emitted light is complementary; an interface exciplex is formed between the blue light fluorescent layer and the electron transport layer, and the triplet state energy level of the interface exciplex is higher than that of the phosphorescent light-emitting layer. The light-emitting layer of the device adopts a non-doping technology, emission of light of several colors is simply overlaid to form white light in a composite mode, the structure is simple, the preparation cost is reduced, light color management can be achieved by optimizing the thickness of each single-layer light-emitting layer body in the light-emitting layer, control is easy, the display index of the device can be improved, and flexibility and repeatability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of organic light-emitting devices, and in particular to a white light organic light-emitting device and a display device. Background Art

[0002] White organic light-emitting diodes (WOLEDs), also known as white organic light-emitting devices, have shown important development prospects in applications such as solid-state lighting and solid-state displays due to their advantages such as high color rendering index, strong mechanical flexibility, high luminous efficiency, low power consumption, energy saving and environmental protection.

[0003] The manufacturing of WOLED devices is mainly achieved by vertically stacking multiple emission layers (or multiple components) to mix the three primary colors (red, green and blue (RGB)) or two complementary colors (blue and yellow or orange). The light-emitting layer structure of WOLED devices is generally doped with multi-color dyes. Since the triplet energy level of red or yellow light guests is low and it is easy to obtain energy, in order to adjust a more standard white light, the concentration of these two guests needs to be controlled below 0.1%. In addition, it is necessary to accurately control the doping concentration in one layer to control the light color and ensure the balanced exciton distribution and stable energy transfer between the luminescent materials. Slight changes in doping concentration will affect the energy transfer between different doping materials, which has a huge impact on the luminescent color of white light OLEDs. However, it is very difficult to always control the concentration completely and accurately during the preparation process, and the process is complicated. Such a complicated process will also consume a lot of luminescent materials containing rare metals, reduce the repeatability of device performance and the low color rendering index (CRI), which is not conducive to industrial promotion. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a white light organic light emitting device and a display device.

[0005] In a first aspect of the present invention, a white light organic light emitting device is provided, comprising: an anode, a cathode and an organic functional layer located between the anode and the cathode, wherein the organic functional layer comprises a hole transport layer, a light emitting layer and an electron transport layer stacked in sequence, wherein the hole transport layer is arranged on the anode side, and the electron transport layer is arranged on the cathode side;

[0006] The light-emitting layer includes a host material layer and at least one guest material layer; the host material layer is a blue fluorescent material layer, and the guest material layer is a phosphorescent material layer; the light emitted by the phosphorescent material layer and the light emitted by the blue fluorescent material layer complementarily recombine to form white light; an interface exciplex is formed between the blue fluorescent material layer and the electron transport layer, and the triplet energy level of the interface exciplex is higher than the triplet energy level of the phosphorescent material layer.

[0007] According to the white light organic light emitting device (i.e., OLED) of the embodiment of the present invention, there are at least the following beneficial effects: the light emitting layer in the white light organic light emitting device includes a host material layer and at least one guest material layer, the host material layer is a blue fluorescent material layer, the guest material layer is a phosphorescent material layer, the light emitted by the phosphorescent material layer in the light emitting layer and the light emitted by the blue fluorescent material layer are complementarily recombined to form white light, specifically, the triplet energy level of the interface exciplex formed between the blue fluorescent material layer and the electron transport layer is higher than the triplet energy level of the phosphorescent material layer, and the phosphorescent material layer emits light through a direct carrier capture mechanism and a sensitization mechanism of the interface exciplex to the phosphorescent material layer, and the light is recombined with the blue light emitted by the blue fluorescent material layer to form white light emission. The white light organic light emitting device is a non-doped white light organic light emitting device, wherein the light emitting layer uses non-doping technology, specifically a blue fluorescent material layer is used as a main material layer, a phosphorescent material layer is used as a guest material layer, the host and guest are separated, that is, the main material layer is not doped with a guest material, and the guest material layer is not doped with a main material. The light emitting layer is compositely constructed by using a non-doped blue fluorescent material layer and a non-doped phosphorescent material layer, and white light is compositely formed by simply superimposing the emission of several colors of light, which can simplify the device structure, simplify the preparation process, and reduce the device preparation cost; and the light color management can be achieved by optimizing the thickness of each single-layer light emitting material layer constituting the light emitting layer, which is easy to control, and can improve the color rendering index of the white light organic light emitting device, increase the flexibility of device design, and improve the repeatability of OLED.

[0008] In some embodiments of the present invention, the material of the blue fluorescent material layer is a thermally activated delayed fluorescence (TADF) material, and / or the phosphorescent material layer is a phosphorescent ultra-thin layer with a thickness less than or equal to 1 nm. The TADF material is specifically a blue TADF material; the fluorescent material of the blue fluorescent material layer in the light-emitting layer is the host material, and the phosphorescent material of the phosphorescent material layer is the guest material.

[0009] The luminescent materials of OLED are mainly divided into two categories: phosphorescent and fluorescent. Considering that fluorescent materials generally only have singlet excitons that can be used to emit light, the internal quantum efficiency of OLEDs based on fluorescent materials is only 25%, which limits the development of high-efficiency white light OLEDs. Both singlet and triplet excitons of phosphorescent materials can be used to emit light, so that the internal quantum efficiency of OLEDs based on phosphorescent materials can reach a theoretical 100%, which is conducive to the preparation of high-efficiency white light OLEDs. However, triplet excitons will accumulate in a high-energy state, resulting in severe exciton quenching and serious efficiency roll-off. The above-mentioned TADF material is used to construct the blue fluorescent material layer. The TADF material has a high fluorescence quantum yield and a large distance between molecules. It can also be used as an electron donor material and can form an interface exciton complex with the electron transport layer as an electron acceptor. Since the triplet excitons of the TADF material can be converted into singlet excitons through antisystem crossing, when it is combined with the phosphorescent material of the phosphorescent material layer, its barrier-free injection characteristic can effectively reduce the driving voltage of the device, and can also enhance the effective energy transfer from the TADF material to the phosphorescent material, inhibit the quenching of triplet excitons in the exciton complex host (that is, the interface exciton complex formed by the blue fluorescent material layer and the electron transport layer), and improve the utilization rate of the excitons, that is, realize the sensitization effect of the TADF material on the phosphorescent material.

[0010] In addition, the phosphorescent material layer uses a phosphorescent ultra-thin layer with a thickness less than or equal to 1nm, which can reduce the amount of expensive phosphorescent materials used, thereby reducing the cost of white light OLEDs. The thickness of the phosphorescent material layer can be further controlled to be 0.01nm to 1nm, for example, the thickness of the phosphorescent material layer can be 0.01nm to 0.1nm, 0.1nm to 1nm, 0.2nm to 1nm, 0.2nm to 0.8nm, 0.3nm to 0.5nm, etc.

[0011] In some embodiments of the present invention, the phosphorescent material layer is a phosphorescent material layer that emits yellow light or a phosphorescent material layer that emits orange light; the blue fluorescent material layer is disposed on one side of the hole transport layer, and the phosphorescent material layer is disposed on one side of the electron transport layer. Through the above arrangement, the yellow light or orange light emitted by the phosphorescent material layer can complement the blue light emitted by the blue fluorescent material layer to form white light.

[0012] In some embodiments of the present invention, the blue fluorescent material layer includes at least two blue sub-fluorescent layers; and the phosphorescent material layer is embedded between adjacent blue sub-fluorescent layers.

[0013] The blue fluorescent material layer may be composed of two blue sub-fluorescent layers, and the phosphorescent material layer is one layer and is embedded between the two blue sub-fluorescent layers; the phosphorescent material layer may be a phosphorescent material layer emitting yellow light or a phosphorescent material layer emitting orange light. The material of the blue sub-fluorescent layer is a blue fluorescent material, which may be a thermally activated delayed fluorescent material.

[0014] The blue fluorescent material layer may be composed of multiple layers (such as three, four, five, etc.) of blue sub-fluorescent layers, and phosphorescent material layers are embedded between adjacent blue sub-fluorescent layers, so that the number of phosphorescent material layers is one less than the number of blue photon sub-fluorescent layers. Generally, each phosphorescent material layer emits a single color of light, and the mixed light emitted by all phosphorescent material layers complements the light emitted by the blue fluorescent material layer to form white light. For example, the blue fluorescent material layer may be composed of three blue sub-fluorescent layers, and the phosphorescent material layers include a phosphorescent material layer that emits green light and a phosphorescent material layer that emits red light, and the two phosphorescent material layers are embedded between adjacent blue sub-fluorescent layers at intervals; for another example, the blue fluorescent material layer may be composed of four blue sub-fluorescent layers, and the phosphorescent material layers include a phosphorescent material layer that emits green light, a phosphorescent material layer that emits yellow light, and a phosphorescent material layer that emits red light, and the three phosphorescent material layers are embedded between adjacent blue sub-fluorescent layers at intervals. Among them, the construction of phosphorescent material layers of different colors can use phosphorescent materials of corresponding colors to construct phosphorescent material layers that can emit corresponding single color light. With the above light-emitting layer structure setting, white light OLEDs with different electroluminescence (EL) spectra can be obtained by changing the embedding order of phosphorescent material layers of different colors in the blue fluorescent material layer; or, the luminescent spectrum of the white light OLED can be changed by changing the thickness of the phosphorescent material layer to achieve ideal white light emission, which is simple to operate, easy to control, and highly flexible. Among them, based on the consideration of device lightness and thinness, the light emitted by each layer of phosphorescent material layer can be designed to have different colors; in some embodiments, phosphorescent material layers that emit the same color light can also be designed on the basis of the mixed light emitted by all phosphorescent material layers and the blue light emitted by the blue fluorescent material layer complementing each other to form white light.

[0015] In addition, considering the existing multi-light-emitting layer hybrid system white light OLED devices, especially those involving 3 or 4 light-emitting materials emitting light simultaneously to achieve a more ideal white light emission, it is often necessary to introduce an additional spacer layer between the fluorescent material layer and the phosphorescent material layer to manage the recombination area and energy transfer of carriers, and further balance the emission intensity of different light-emitting layers. However, the introduction of an additional spacer layer will cause a complex device structure of the multi-light-emitting layer hybrid white light OLED, further increasing the production cost of the device. At the same time, the multiple layer structure also introduces multiple heterojunction interfaces, affecting the stability of the device. In this regard, in the white light organic light-emitting device of the present invention, by designing the blue fluorescent material layer to include multiple blue sub-fluorescent layers, and embedding phosphorescent material layers between adjacent blue sub-fluorescent layers, the blue sub-fluorescent layers located between the phosphorescent material layers can be used as spacer layers, which can avoid using additional spacer layer structures to affect the stability of the device, and can effectively simplify the device structure and preparation process.

[0016] In the above light-emitting layer, if the blue fluorescent material layer adopts blue TADF material, the singlet excitons and triplet excitons generated by electricity can be captured by blue TADF molecules to realize blue light emission, and part of the triplet exciton energy is transferred to the phosphorescent material of the phosphorescent material layer to realize long-wavelength phosphorescent emission, or diffused to the middle of the light-emitting layer, and the excess triplet energy is collected and transferred to the blue fluorescent material layer for anti-intersystem crossing, realizing the interlayer sensitization strategy. Based on the above light-emitting mechanism, OLED devices can achieve a theoretical 100% internal quantum efficiency, thereby obtaining high device efficiency.

[0017] In some embodiments of the present invention, the number of blue sub-fluorescent layers in the blue fluorescent material layer is greater than two, the phosphorescent material layer is embedded between adjacent blue sub-fluorescent layers, and the mixed light emitted by all phosphorescent material layers is complementary to the light emitted by the blue fluorescent material layer; each phosphorescent material layer is arranged in the order of triplet energy from high to low from the anode to the cathode, so that the energy is fully utilized when transferred to each phosphorescent material layer, and / or the interval between adjacent phosphorescent material layers is 2nm to 4nm. Specifically, the interval between adjacent phosphorescent material layers can be 2nm to 3nm, 2.5nm to 3.5nm, or 3nm to 4nm.

[0018] In some embodiments of the present invention, the phosphorescent material layer includes one or more of a phosphorescent material layer emitting green light, a phosphorescent material layer emitting yellow light, and a phosphorescent material layer emitting red light. The phosphorescent material layer selection design needs to ensure that the light (or mixed light) emitted by all phosphorescent material layers is complementary to the light emitted by the blue fluorescent material layer.

[0019] In some embodiments of the present invention, the LUMO energy level of the blue fluorescent material layer is higher than the LUMO energy level of the electron transport layer by more than 0.55 ev. The blue fluorescent material layer and the electron transport layer can form an interface exciton complex, and the phosphorescent material layer with a thickness less than or equal to 1 nm can be designed to include a plurality of phosphorescent material units arranged in a dispersed interval, and each phosphorescent material unit is embedded between the blue sub-fluorescent layers like a watermelon seed, and does not form a film. By designing the LUMO energy level of the blue fluorescent material layer to be higher than the LUMO energy level of the electron transport layer by more than 0.55 ev, the effective transfer of excitons at various interfaces of the device can be enhanced. The electron transport layer has an electron acceptor function, and the LUMO energy level of the electron transport layer can be controlled to be below -3.5 ev.

[0020] In some embodiments of the present invention, the thickness of the blue fluorescent material layer is 3nm to 100nm; and / or the thickness of the electron transport layer is 20nm to 100nm. The thickness of the blue fluorescent material layer can further be 15nm to 100nm, 20nm to 80nm, 30nm to 70nm, 40nm to 80nm, 50nm to 100nm, 40nm to 60nm. If the blue fluorescent material layer includes at least two blue sub-fluorescent layers, the thickness of the blue fluorescent material layer is the sum of the thicknesses of the blue sub-fluorescent layers. The thickness of the electron transport layer can further be 30nm to 90nm, 40nm to 80nm, 50nm to 90nm, 35nm to 75nm, 60nm to 90nm.

[0021] In addition, the distance between the phosphorescent material layer closest to the hole transport layer and the hole transport layer can be designed to be 0 to 30 nm; the distance between the phosphorescent material layer closest to the electron transport layer and the electron transport layer can also be designed to be 0 to 30 nm; the distance between the blue sub-fluorescent layers at both ends of the blue fluorescent material layer along the thickness direction can also be designed to be 0 to 30 nm.

[0022] In some embodiments of the present invention, the triplet energy level of the blue fluorescent material layer is greater than the triplet energy level of the phosphorescent material layer; and / or, the triplet energy level of the blue fluorescent material layer is greater than 2.4 eV. By controlling the triplet energy level of the blue fluorescent material layer to be greater than the triplet energy level of the phosphorescent material layer, it is possible to ensure that the triplet excitons of the blue fluorescent material on the blue fluorescent material layer are effectively utilized by the phosphorescent material on the phosphorescent material layer. Since the triplet energy levels of the green, yellow, and red phosphorescent materials that are complementary to blue light generally do not exceed 2.4 eV, the use of a blue fluorescent material with a triplet energy level greater than 2.4 eV can ensure that the triplet excitons of the blue fluorescent material are effectively utilized by the phosphorescent material.

[0023] In some embodiments of the present invention, the material of the phosphorescent material layer is a phosphorescent iridium complex, and the phosphorescent material layer emitting light of different colors can be composed of phosphorescent iridium complexes of corresponding colors; and / or, the emission peak of the blue fluorescent material layer is located at 400nm~480nm, that is, the emission peak of the fluorescent material emission spectrum used in the blue fluorescent material layer is located at 400nm~480nm, for example, it can be 420nm~480nm, 430nm~470nm, 410nm~450nm, 440nm~480nm.

[0024] In some embodiments of the present invention, the organic functional layer further comprises:

[0025] A hole injection layer, disposed between the anode and the hole transport layer;

[0026] An electron blocking layer, disposed between the hole transport layer and the light emitting layer;

[0027] The electron injection layer is disposed between the electron transport layer and the cathode.

[0028] According to a second aspect of the present invention, a display device is provided, which comprises any one of the white light organic light emitting devices described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0030] Figure 1 This is a schematic structural diagram of a white light organic light emitting device according to an embodiment of the present invention;

[0031] Figure 2 The current density-voltage-brightness curve (JVL), power efficiency-brightness-current efficiency curve, EQE-brightness curve and normalized electroluminescence spectrum of the yellow organic light-emitting device of Comparative Example 1 are shown;

[0032] Figure 3 The current density-voltage-brightness curve (JVL), power efficiency-brightness-current efficiency curve, EQE-brightness curve and normalized electroluminescence spectrum of the white light organic light emitting device of Example 1 are shown;

[0033] Figure 4 The energy level diagram of the white light organic light emitting device of Example 1 and the four white light organic light emitting devices at 1000 cd / m 2 The color coordinates CIE diagram below;

[0034] Figure 5 The current density-voltage-brightness curve (JVL), power efficiency-brightness-current efficiency curve, EQE-brightness curve and normalized electroluminescence spectrum of the white organic light emitting device of Example 2;

[0035] Figure 6 The current density-voltage-brightness curve (JVL), power efficiency-brightness-current efficiency curve, EQE-brightness curve and normalized electroluminescence spectrum of the white light organic light emitting device of Example 3;

[0036] Figure 7 The four white light organic light emitting devices in Example 3 are 1000 cd / m 2 The CIE diagram below;

[0037] Figure 8 The normalized electroluminescence spectra and CRI, CIE and CCT of the four white organic light-emitting devices in Example 3 at different current densities;

[0038] Fig. 9 The power efficiency-brightness-current efficiency curve and the normalized electroluminescence spectrum of the white organic light emitting device of Example 4 are shown. DETAILED DESCRIPTION

[0039] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0040] The names and abbreviations of the experimental methods, production processes, instruments and equipment involved in the embodiments of the present invention are conventional names in the field and are very clear and unambiguous in the relevant application fields. Technical personnel in the field can understand the conventional process steps and apply the corresponding equipment according to the names and implement them according to conventional conditions or conditions recommended by the manufacturer.

[0041] The various raw materials or reagents used in the examples of the present invention are not particularly limited in their sources, and are all conventional products that can be purchased commercially, or can be prepared according to conventional methods well known to those skilled in the art.

[0042] The monochromatic or white light organic light emitting devices involved in the embodiments and comparative examples of the present invention are specifically organic light emitting diode devices, which are all realized by high vacuum evaporation process. All monochromatic or white light organic light emitting devices are prepared on a pre-patterned ITO (indium tin oxide) glass substrate purchased from Yiyang South China Xiangcheng Technology Co., Ltd., with a surface resistance of 17Ω / sq.

[0043] Except for high-purity aluminum particles purchased from Yiyang South China Xiangcheng Technology Co., Ltd., other organic and inorganic functional materials were purchased from Shenzhen Purui Materials Technology Co., Ltd. and did not undergo any purification treatment before use.

[0044] The preparation methods of all the monochromatic and white light organic light emitting devices involved in the embodiments and comparative examples of the present invention are as follows.

[0045] 1. Cleaning of ITO glass substrate.

[0046] After cleaning the oil stains on the surface of the ITO glass substrate with decon alkaline cleaning agent, the ITO glass substrate was repeatedly rinsed with deionized water until a complete water film was formed. The ITO glass substrate was then placed in deionized water, ethanol and acetone in turn and ultrasonically cleaned for 20 minutes each time.

[0047] 2. Drying of ITO glass substrate.

[0048] The cleaned ITO glass substrate was taken out from acetone, rinsed with ethanol, blown dry with a nitrogen gun, and placed in a constant temperature oven at 85°C for 2 hours.

[0049] 3. UV treatment of ITO glass substrate.

[0050] Before evaporation, the dried ITO glass substrate was taken out from the oven and treated with ultraviolet ozone for 20 minutes to further remove organic matter adhered to the ITO glass substrate and improve the surface work function of ITO.

[0051] 4. Cavity filling of ITO glass substrate.

[0052] Take out the ITO glass substrate from the UV box and transfer it into the cavity of the high vacuum coating machine.

[0053] 5. Vacuum the equipment.

[0054] Turn on the power supply, mechanical pump and molecular pump of the high vacuum coating machine in sequence to evacuate the vacuum chamber.

[0055] 6. Thermal evaporation preparation of organic light-emitting devices.

[0056] When the vacuum degree in the high vacuum coating machine chamber is lower than 5×10 -4 Pa, start heating the thermal evaporation sources in the cavity containing functional materials and luminescent materials such as hole injection layer materials, electron injection layer materials, hole transport layer materials, electron transport layer materials, electron blocking layer materials, etc., and thermally deposit various functional layers on the ITO glass substrate in sequence according to the designed device structure.

[0057] Finally, the mask plate with the ITO glass substrate is rotated to align the mask position for depositing the aluminum cathode with the ITO glass substrate, and the thermal evaporation crucible with aluminum particles is heated to deposit the aluminum cathode, thereby finally preparing a complete organic light-emitting device.

[0058] During the thermal evaporation process, the evaporation rate and film thickness of the material are monitored by a quartz crystal frequency meter connected outside the vacuum chamber. Among them, the evaporation rate of the phosphorescent light-emitting layer material is The evaporation rate of other organic functional layer materials is The evaporation rates of Liq and Al are approximately and

[0059] The overlapping part of the ITO glass and the aluminum cathode is taken as the effective light-emitting area of ​​the device, and the effective light-emitting area of ​​the device is 3.0 mm×3.0 mm.

[0060] Figure 1The schematic diagram of the structure of an organic light-emitting device according to an embodiment of the present invention is as follows: anode 11 / hole injection layer 12 / hole transport layer 13 / electron blocking layer 14 / light-emitting layer 15 / electron transport layer 16 / electron injection layer 17 / cathode 18 .

[0061] First, an ITO glass substrate can be used as the anode 11, and a layer of HAT-CN can be deposited thereon in high vacuum as a hole injection layer 12, and the thickness can be determined to be a certain value between 2nm and 10nm. Secondly, a hole transport layer material TAPC is deposited on the hole injection layer 12 to form a hole transport layer 13, and the thickness can be maintained at a certain value between 5nm and 100nm. Next, an electron blocking layer material TCTA is deposited on the hole transport layer 13 to form an electron blocking layer 14, and the thickness can be maintained at a certain value between 1nm and 10nm. Then, a light-emitting layer 15 is deposited on the electron blocking layer 14, and the total thickness can be maintained at a certain value between 5nm and 100nm. After that, an electron transport layer 16 is deposited thereon, and the thickness can be maintained at a certain value between 5nm and 100nm. Immediately afterwards, an electron injection layer material Liq is deposited to form an electron injection layer 17, and the thickness can be maintained at a certain value between 0.1nm and 5nm. Finally, an aluminum metal film on one side is deposited on the electron injection layer as a cathode 18, and the thickness can be controlled to be a certain value between 100nm and 400nm. At this point, a complete white light organic light-emitting device has been prepared.

[0062] The structure of the organic light emitting device of the comparative example is similar to that of the embodiment, and the main difference lies in the structure of the light emitting layer.

[0063] The present invention specifically tests the performance of the organic light emitting devices in the embodiments and comparative examples according to the following method.

[0064] The prepared organic light-emitting device was taken out from the vacuum chamber, and the current density, current efficiency and brightness of the device were obtained using a computer-controlled S SpectraScan PR655 photometer and a Keithley 2400 digital source meter. At the same time, the computer-controlled Spectra Scan PR655 spectroradiometer could also collect the electroluminescence spectrum, color coordinates and color rendering index of the device at different voltages.

[0065] The specific compound names corresponding to the abbreviations of the chemical substances involved in the following embodiments and comparative examples of the present invention are as follows.

[0066] HAT CN: 2,3,6,7,10,11-Hexaazatriphenylenehexacabonitrile, i.e. 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene, CAS No. 105598-27-4, its structural formula is

[0067] TAPC: 4,4′-cyclohexylidenebis[N,N-bis(p-tolyl)aniline], i.e. 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline, CAS No. 58473-78-2, with the structural formula:

[0068] TCTA: 4,4′,4”-tris(carbazol-9-yl)triphenylamine, CAS No. 139092-78-7, with the structural formula:

[0069] B4PymPm: 4,6-Bis(3,5-di(pyridin-4-yl)phenyl)-2-methylpyrimidine, CAS No.: 1030380-51-8, its structural formula is

[0070] Liq: Lithium-8-hydroxyquinolinolate, i.e. 8-hydroxyquinoline-lithium, CAS No. 850918-68-2, its structural formula is:

[0071] PPCzTrz: 9-(5'-(4,6-Diphenyl-1,3,5-triazin-2-yl)-[1,1':3',1"-terphenyl]-2'-yl)-3,6-diphenyl-9H-carbazole, CAS No. 2329651-89-8, its structural formula is:

[0072] PO-01: Bis(4-phenylthieno[3,2-c]pyridinato-N,C2')(acetylacetonate)iridium(III), i.e. acetylacetonate di(4-phenyl-thieno[3,2-c]pyridinato-C2,N)iridium(III), CAS No. 1258323-36-2, with the structural formula:

[0073]

[0074] Mono-Ir: A green luminescent organic small molecule based on iridium complex. The molecular structure is as follows:

[0075]

[0076] BuIr(dbpz)CN: Red luminescent organic small molecule based on iridium complex. The molecular structure is as follows:

[0077]

[0078] Comparative Example 1

[0079] In order to prove the feasibility of the present invention, in order to verify the performance of an organic light-emitting device in which the light-emitting layer is constructed of a non-doped and ultra-thin phosphorescent light-emitting layer, an electron donor material TCTA and an electron acceptor material B4PymPm are selected to form an interface exciplex, and a yellow light phosphorescent material layer with a thickness of less than 1 nm is inserted in the middle of the interface to prepare an interface exciplex-sensitized yellow light organic light-emitting device, the structure of which is as follows:

[0080] Yellow organic light-emitting device Y: ITO / HAT-CN (10nm) / TAPC (40nm) / TCTA (5nm or 10nm) / PO-01 (0.3nm or 0.6nm) / B4PymPm (50nm) / Liq (1nm) / Al (100nm).

[0081] The specific structure of each device is as follows:

[0082] Yellow organic light-emitting device Y1: ITO / HAT-CN (10nm) / TAPC (40nm) / TCTA (5nm) / PO-01 (0.3nm) / B4PymPm (50nm) / Liq (1nm) / Al (100nm).

[0083] Yellow organic light-emitting device Y2: ITO / HAT-CN (10nm) / TAPC (40nm) / TCTA (5nm) / PO-01 (0.6nm) / B4PymPm (50nm) / Liq (1nm) / Al (100nm);

[0084] Yellow organic light-emitting device Y3: ITO / HAT-CN (10nm) / TAPC (40nm) / TCTA (10nm) / PO-01 (0.3nm) / B4PymPm (50nm) / Liq (1nm) / Al (100nm);

[0085] Yellow organic light-emitting device Y1: ITO / HAT-CN (10nm) / TAPC (40nm) / TCTA (10nm) / PO-01 (0.6nm) / B4PymPm (50nm) / Liq (1nm) / Al (100nm).

[0086] In the above yellow light OLED, the 10nm thick HAT-CN layer is the hole injection layer, the 1nm thick Liq layer is the electron injection layer. The 40nm thick TAPC layer is the hole transport layer, the 5nm or 10nm TCTA layer is both the electron blocking layer and the electron donor layer of the interface exciplex, the 50nm thick B4PymPm layer is both the electron transport layer and the electron acceptor layer of the interface exciplex; the 0.3nm or 0.6nm PO-01 ultra-thin layer is the phosphorescent material layer that emits yellow light. ITO is the anode, and the 100nm thick Al film is the cathode.

[0087] The performance of each yellow organic light emitting device of the comparative example was tested according to the method described above, and the results were as follows: Figure 2 shown. Figure 2 (a), (b), (c), and (d) are four different yellow organic light-emitting devices at 1000 cd / m 2 Current density-voltage-brightness curve (JVL), power efficiency-brightness-current efficiency curve, EQE-brightness curve and normalized electroluminescence spectrum under.

[0088] from Figure 2 From the JVL curve relationship shown in (a), it can be seen that the turn-on voltage of the yellow organic light-emitting device is 1.85V. It can be seen that the energy transfer barrier between the excited complex formed by TCTA / B4PymPm and the phosphorescent guest PO-01 is small, and the device structure design is reasonable. Figure 2 As shown in (b) and (c), when the thickness of the electron donor layer TCTA in the device is 5nm and the thickness of the phosphorescent guest PO-01 is 0.3nm, the current efficiency is 72.9cd / A, the power efficiency is 116.3lm / W, and the external quantum efficiency is 21.4%, which are completely comparable to the existing doped phosphorescent devices. However, the device structure and preparation process of the interface exciplex-sensitized phosphorescent ultra-thin layer OLEDs are simpler and can reduce the use of expensive phosphorescent materials, proving the feasibility and universal applicability of the interface exciplex-sensitized phosphorescent ultra-thin layer structure for monochromatic light devices.

[0089] In addition, from Figure 2 From the normalized electroluminescence spectrum of the device shown in (d), it can be seen that the device has only one luminescence peak, 556nm in the yellow light region, with color coordinates of (0.466, 0.528), achieving good yellow light emission. The luminescence peaks of the exciplex and its single component do not appear in the spectrum of the device, indicating the complete energy transfer from the interface exciplex host to the phosphorescent material layer guest, which further explains the rationality and feasibility of device design using the phosphorescent luminescent layer.

[0090] Example 1

[0091] To demonstrate the feasibility of achieving white light emission in the present invention, this embodiment, based on Comparative Example 1, introduces a non-doped blue light TADF material (PPCzTrz) layer whose emitted light is complementary to the yellow light emitted by the PO-01 phosphorescent material layer to the interface of the exciplex, and prepares a blue-yellow dual-color composite white light organic light-emitting device, and compares the performance of the white light organic light-emitting devices with different thicknesses of PO-01 phosphorescent material layers under the interface exciplex.

[0092] The structure of the white light organic light emitting device in this embodiment is as follows:

[0093] White organic light emitting devices W11-W14: ITO / HAT-CN (10nm) / TAPC (40nm) / TCTA (5nm) / PPCzTrz (15nm) / PO-01 (X nm) / B4PymPm (50nm) / Liq (1nm) / Al (100nm). Where X = 0.2nm, 0.4nm, 0.6nm or 0.8nm, corresponding to devices W11, W12, W13 and W14.

[0094] In the above white light organic light emitting device, the 15 nm thick PPCzTrz layer serves as both a blue fluorescent material layer and an electron donor layer, and can form an interfacial exciplex with the electron transport layer (B4PymPm layer) serving as an electron acceptor layer; the other layers are similar to those in Comparative Example 1. The light emitting layer in the white light organic light emitting device includes a blue fluorescent material layer and a phosphorescent material layer emitting yellow light, wherein the blue fluorescent material layer is a host material layer, and the phosphorescent material layer emitting yellow light is a guest material layer, both of which are non-doped light emitting layers, and the phosphorescent material layer is specifically a phosphorescent ultra-thin layer having a thickness of less than 1 nm, and the yellow light emitted by the phosphorescent material layer complements the blue light emitted by the blue fluorescent material layer to form white light.

[0095] The performance of each white light organic light emitting device of this embodiment was tested according to the method described above. The results are as follows: Figure 3 shown. Figure 3 (a), (b), (c), and (d) are four different white light OLEDs at 1000 cd / m 2 Current density-voltage-luminance curve (JVL), power efficiency-luminance-current efficiency curve, EQE-luminance curve and normalized electroluminescence spectrum under.

[0096] Depend on Figure 3 As shown in (a), thanks to the full utilization of the energy of the exciplex, the turn-on voltage of the W11~W14 devices can be as low as 2.4V. Figure 3In (b) and (c), when the thickness of PO-01 in the W13 device is set to 0.6nm, the maximum current efficiency and power efficiency of the device can reach 44.7cd / A and 56.7lm / W, and the EQE is up to 17.7%. Compared with the monochromatic device in Comparative Example 1, since the energy of the device is transferred to several luminescent materials, there is inevitably loss, so the white light efficiency is slightly worse. It can be seen that the four devices have successfully achieved complementary white light emission, and their normalized electroluminescence spectra (d) contain two obvious emission peaks, which are located in the blue light region and the yellow light region respectively. The emission peak in the blue light region originates from the emission of the PPCzTrz non-doped layer; the emission peak in the yellow light region originates from the emission of the PO-01 phosphorescent material layer, and the blue light emitted by the PPCzTrz non-doped layer and the yellow light emitted by the PO-01 phosphorescent light-emitting layer are combined to form white light emission.

[0097] At the same time, similar to the monochromatic device in Comparative Example 1, the luminescence peak of the main body of the exciplex does not appear in the spectrum, and complete energy transfer from the main body to the guest is achieved, as shown in FIG. Figure 4 As shown in (a), the thicker blue fluorescent material layer and the electron acceptor material B4PymPm also meet the conditions for forming an interfacial exciplex (the LUMO energy level difference between the two is greater than 0.5 eV). Figure 4 (b) shows that at 1000cd / m 2 The color coordinates of the four devices are (0.32, 0.40), (0.33, 0.40), (0.33, 0.41) and (0.34, 0.41), respectively, all of which are located in the white light emission region. The slight change in the thickness of the phosphor material layer has little effect on the spectrum and color coordinates, which proves the feasibility of the present invention to achieve two-color white light emission.

[0098] Example 2

[0099] In order to prove the universal applicability of the present invention in achieving white light emission, based on the white light device in Example 1, this example introduces a green mono-Ir and a red (BuIr(dbpz)CN) phosphorescent material layer at the interface of the exciplex (PPCzTrz / B4PymPm) to prepare a blue-green-red three-color composite white light organic light-emitting device. At the same time, the blue light non-doped layer with different thicknesses was embedded in the interface exciplex to study its effect on the device performance.

[0100] The structure of the white light organic light emitting device in this embodiment is as follows:

[0101] White organic light emitting devices W21-W24: ITO / HAT-CN (10nm) / TAPC (40nm) / TCTA (5nm) / PPCzTrz (15nm) / Mono-Ir (0.1nm) / PPCzTrz (4nm) / BuIr (dbpz) CN (0.1nm) / PPCzTrz (X nm) / B4PymPm (50nm) / Liq (1nm) / Al (100nm). Where X = 2, 4, 6 and 8nm, corresponding to devices W21, W22, W23 and W24.

[0102] In the above white light organic light-emitting device, the light-emitting layer includes a blue fluorescent material layer and two phosphorescent material layers, wherein the blue fluorescent material layer is a main material layer, and the two phosphorescent material layers are guest material layers, and they are all non-doped light-emitting layers; the blue fluorescent material layer includes three blue sub-fluorescent layers, and phosphorescent material layers are embedded between adjacent blue sub-fluorescent layers, and the phosphorescent material layers are phosphorescent ultra-thin layers with a thickness of less than 1nm; the phosphorescent material layers specifically include a phosphorescent material layer that emits green light and a phosphorescent material layer that emits red light, and the mixed light emitted by all the phosphorescent material layers complements the blue light emitted by the blue fluorescent material layer to form white light.

[0103] The performance of each white light organic light emitting device of this embodiment was tested according to the method described above. The results are as follows: Figure 5 shown. Figure 5 (a), (b), (c), and (d) are four different white light OLEDs at 1000 cd / m 2 Current density-voltage-brightness curve (JVL), power efficiency-brightness-current efficiency curve, EQE-brightness curve and normalized electroluminescence spectrum under.

[0104] like Figure 5 As shown in (a), after introducing multiple interfaces, the turn-on voltage of the device is still maintained at about 2.5V, indicating the effective transfer of energy within the device. In this embodiment, a 4nm thick PPCzTrz layer is introduced between the phosphorescent material layers as a spacer layer to adjust the distance between the carriers and each phosphorescent light-emitting object. Since the triplet states of green and red light are much lower than those of blue light, it is easier to capture excitons. Here, the thickness of the phosphorescent material layer is set at 0.1nm, and the thickness of the last layer of blue fluorescent material is adjusted. Figure 5 In (b) and (c), when the thickness of PPCzTrz in the W22 device is set to 4nm, the maximum current efficiency and power efficiency of the device can reach 44.7cd / A and 54.4lm / W, and the maximum EQE is 16.1%. Figure 5From the normalized electroluminescence spectra of each in (d), it can be seen that the devices all achieve good white light emission. Specifically, the normalized electroluminescence spectra of the three-color composite white light organic light-emitting devices all contain three obvious emission peaks, which are located in the blue light region, green light region and red light region, respectively, and are attributed to the emission of PPCzTrz blue TADF, 0.1nm Mono-Ir green phosphor material layer and 0.1nm BuIr(dbpz)CN red phosphor material layer. The three light colors are combined to form white light, which is 1000cd / m 2 The color coordinates of the three-color white light emission are (0.36, 0.47), (0.35, 0.47), (0.34, 0.46) and (0.34, 0.44), all of which are located in the white light emission region. The above results prove the feasibility of the present invention to achieve three-color white light emission and the universal applicability of achieving white light emission.

[0105] At the same time, compared Figure 5 From the normalized electroluminescence spectra of the devices shown in (d), it can be seen that when the thickness of the blue fluorescent material layer is changed, the spectrum of the corresponding white light organic light-emitting device changes slightly, and the device W24 achieves a more balanced white light emission.

[0106] Example 3

[0107] In this embodiment, a white light organic light emitting device with a high color rendering index is further prepared on the basis of the three-color composite white light organic light emitting device W23 in Embodiment 2. By adjusting the thickness of the red phosphorescent material layer in the white light organic light emitting device, the red light is allowed to capture more excitons and the green light emission intensity is balanced.

[0108] The structure of the white light organic light emitting device in this embodiment is as follows:

[0109] White organic light emitting devices W31-W34: ITO / HAT-CN (10nm) / TAPC (40nm) / TCTA (5nm) / PPCzTrz (15nm) / Mono-Ir (0.1nm) / PPCzTrz (4nm) / BuIr (dbpz)CN (Y nm) / PPCzTrz (6nm) / B4PymPm (50nm) / Liq (1nm) / Al (100nm). Where Y = 0.1, 0.2, 0.3 and 0.4nm, corresponding to devices W31, W32, W33 and W34.

[0110] In the above white light organic light-emitting device, the light-emitting layer includes a blue fluorescent material layer and two phosphorescent material layers, wherein the blue fluorescent material layer is a main material layer, and the two phosphorescent material layers are guest material layers, and they are all non-doped light-emitting layers; the blue fluorescent material layer includes three blue sub-fluorescent layers, and phosphorescent material layers are embedded between adjacent blue sub-fluorescent layers, and the phosphorescent material layers are phosphorescent ultra-thin layers with a thickness of less than 1nm; the phosphorescent material layers specifically include a phosphorescent material layer that emits green light and a phosphorescent material layer that emits red light, and the mixed light emitted by all the phosphorescent material layers complements the blue light emitted by the blue fluorescent material layer to form white light.

[0111] The performance of each white light organic light emitting device of this embodiment was tested according to the method described above. The results are as follows: Figure 6 shown. Figure 6 (a), (b), (c), and (d) are four different white light OLEDs at 1000 cd / m 2 Current density-voltage-brightness curve (JVL), power efficiency-brightness-current efficiency curve, EQE-brightness curve and normalized electroluminescence spectrum under.

[0112] like Figure 6 As shown in (a), even after changing the thickness of the red phosphor material layer, the turn-on voltage of the device remains at around 2.6V. Figure 6 In (b) and (c), when the thickness of the red phosphor material layer of the W31 device is set to 0.1nm, the maximum current efficiency and power efficiency of the device can reach 36.3cd / A and 44.2lm / W, and the EQE can reach a maximum of 13.7%. It still maintains a relatively average device performance. Figure 6 From the normalized electroluminescence spectra of each device in (d), it can be seen that the devices all achieve good white light emission. Specifically, the normalized electroluminescence spectra of the three-color composite white organic light-emitting devices all contain three obvious emission peaks, which are located in the blue light region, green light region and red light region, respectively, and are attributed to the emission of PPCzTrz blue TADF, 0.1nm Mono-Ir green phosphor material layer and 0.1nm BuIr(dbpz)CN red phosphor material layer. Changing the thickness of the red phosphor material layer will significantly change the spectral emission of the device. Figure 7 The color coordinates of three light colors combined to form white light are shown in the figure. 2 The color coordinates are (0.33, 0.44), (0.34, 0.40), (0.36, 0.41) and (0.38, 0.39), all of which are located in the white light emission region.

[0113] in addition, Figure 8The normalized electroluminescence spectrum and color rendering index (CRI), CIE chromaticity coordinates and correlated color temperature (CCT) of the white light organic light emitting device of this embodiment at different current densities are shown. Figure 8 It can be seen that the four three-color white light organic light-emitting devices all achieve good white light emission, and the emission spectrum clearly contains four emission peaks. As the thickness of the red phosphor material layer increases, the blue light component also increases relatively. At 0.3nm, the blue and green light capture excitons reach saturation. The spectra of the white light organic light-emitting devices W32 and W33 achieve wide coverage in the visible light region, with a half-peak width close to 100nm, and a color rendering index greater than 90, which can meet the needs of indoor lighting. Among these two white light organic light-emitting devices, the blue light component is stronger, and the device color temperature is 5000K, achieving good cold white light emission.

[0114] Example 4

[0115] Based on the three-color composite white light organic light emitting device W34 in Example 3, this embodiment further prepares a white light device with a high color rendering index by adding a layer of yellow phosphorescent material to achieve light spectrum emission.

[0116] Device W4: ITO / HAT-CN(10nm) / TAPC(40nm) / TCTA(5nm) / PPCzTrz(15nm) / Mono-Ir(0.1nm) / PPCzTrz(4nm) / PO-0 1(0.07nm) / PPCzTrz(4nm) / BuIr(dbpz)CN(0.4nm) / PPCzTrz(6nm) / B4PymPm(50nm) / Liq(1nm) / Al(100nm).

[0117] In the above white light organic light-emitting device, the light-emitting layer includes a blue fluorescent material layer and three phosphorescent material layers, wherein the blue fluorescent material layer is a main material layer, and the three phosphorescent material layers are guest material layers, and they are all non-doped light-emitting layers; the blue fluorescent material layer includes four blue sub-fluorescent layers, and phosphorescent material layers are embedded between adjacent blue sub-fluorescent layers, and the phosphorescent material layers are phosphorescent ultra-thin layers with a thickness of less than 1 nm; the phosphorescent material layers specifically include a phosphorescent material layer emitting green light, a phosphorescent material layer emitting yellow light, and a phosphorescent material layer emitting red light, and the mixed light emitted by all the phosphorescent material layers complements the blue light emitted by the blue fluorescent material layer to form white light.

[0118] According to the method described above, each white organic light emitting device of this embodiment was subjected to 1000 cd / m 2 The power efficiency-brightness-current efficiency curve and normalized electroluminescence spectrum under Fig. 9 shown. Fig. 9(a) and (b) are four different white light OLEDs at 1000cd / m 2 The power efficiency-brightness-current efficiency curve and normalized electroluminescence spectrum under Fig. 9 As shown in (a), the maximum current efficiency and power efficiency of the W4 device can reach 48.9cd / A and 42.1lm / W. It still maintains a relatively average device performance. Fig. 9 (b) shows that the devices all achieve very standard white light emission. Specifically, the normalized electroluminescence spectra of the four-color composite white light organic light-emitting device contain four obvious emission peaks, which are located in the blue light region, green light region, yellow light region and red light region, respectively, and are attributed to the emission of the PPCzTrz blue TADF fluorescent material layer, the 0.1nm Mono-Ir green phosphorescent material layer, the 0.07nm PO-01 yellow phosphorescent material layer and the 0.5nm BuIr(dbpz)CN red phosphorescent material layer. Fig. 9 (b) shows the color coordinate change of the four light colors combined to form white light, at 1000 cd / m 2 The color coordinates are (0.361, 0.389), both located in the white light emission area, and the CRI is as high as 95.

[0119] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A white light organic light emitting device, characterized in that: include: An anode, a cathode and an organic functional layer located between the anode and the cathode, wherein the organic functional layer comprises a hole transport layer, a light emitting layer and an electron transport layer which are stacked in sequence, the hole transport layer is arranged on the anode side, and the electron transport layer is arranged on the cathode side; The light-emitting layer includes a host material layer and at least one guest material layer; the host material layer is a blue fluorescent material layer, and the guest material layer is a phosphorescent material layer; the light emitted by the phosphorescent material layer and the light emitted by the blue fluorescent material layer complementarily recombine to form white light; an interface exciplex is formed between the blue fluorescent material layer and the electron transport layer, and the triplet energy level of the interface exciplex is higher than the triplet energy level of the phosphorescent material layer.

2. The white light organic light emitting device according to claim 1, characterized in that: The material of the blue fluorescent material layer is a thermally activated delayed fluorescent material; and / or the phosphorescent material layer is a phosphorescent ultra-thin layer with a thickness less than or equal to 1 nm.

3. The white light organic light emitting device according to claim 2, characterized in that: The phosphorescent material layer is a phosphorescent material layer that emits yellow light or a phosphorescent material layer that emits orange light; the blue fluorescent material layer is arranged on one side of the hole transport layer, and the phosphorescent material layer is arranged on one side of the electron transport layer.

4. The white light organic light emitting device according to claim 2, characterized in that: The blue fluorescent material layer includes at least two blue sub-fluorescent layers; the phosphorescent material layer is embedded between adjacent blue sub-fluorescent layers.

5. The white light organic light emitting device according to claim 4, characterized in that: The number of blue sub-fluorescent layers in the blue fluorescent material layer is greater than two, the phosphorescent material layer is embedded between adjacent blue sub-fluorescent layers, and the mixed light emitted by all phosphorescent material layers is complementary to the light emitted by the blue fluorescent material layer; The phosphorescent material layers are arranged in descending order of triplet energy from the anode to the cathode, and / or the interval between adjacent phosphorescent material layers is 2 nm to 4 nm.

6. The white light organic light emitting device according to claim 5, characterized in that: The phosphorescent material layer includes one or more of a phosphorescent material layer emitting green light, a phosphorescent material layer emitting yellow light, and a phosphorescent material layer emitting red light.

7. The white light organic light emitting device according to any one of claims 1 to 6, characterized in that: The LUMO energy level of the blue fluorescent material layer is higher than the LUMO energy level of the electron transport layer by more than 0.55 eV.

8. The white light organic light emitting device according to any one of claims 1 to 6, characterized in that: The thickness of the blue fluorescent material layer is 3 nm to 100 nm; and / or the thickness of the electron transport layer is 20 nm to 100 nm.

9. The white light organic light emitting device according to any one of claims 1 to 6, characterized in that: The triplet energy level of the blue fluorescent material layer is greater than the triplet energy level of the phosphorescent material layer; and / or, the triplet energy level of the blue fluorescent material layer is greater than 2.4 eV; and / or, the emission peak of the blue fluorescent material layer is located at 400nm to 480nm.

10. The white light organic light emitting device according to any one of claims 1 to 6, characterized in that: The organic functional layer further comprises: A hole injection layer, disposed between the anode and the hole transport layer; An electron blocking layer, disposed between the hole transport layer and the light emitting layer; The electron injection layer is disposed between the electron transport layer and the cathode.

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

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