High-efficiency long-life dark blue light OLED device

Abstract

The invention belongs to the technical field of photoelectric devices, and particularly discloses a high-efficiency long-life dark blue light OLED device which comprises a preset substrate, a first bottom water and oxygen barrier layer, an OLED unit, a third all-dimensional water and oxygen barrier layer and a cover plate from bottom to top, and the OLED unit comprises a cathode, an electron transport layer, a light-emitting layer, a second water and oxygen barrier layer, a hole injection layer and an anode from bottom to top. And the second water-oxygen barrier layer is an organic single-crystal multifunctional layer. According to the high-efficiency long-service-life dark blue light OLED device, the organic single crystal which is high in mobility, good in thermal stability and regular in molecular arrangement is selected as the charge transmission layer, the main body material with TTA property is doped with the MR-TADF dye to serve as the light emitting layer, the electroluminescence performance, stability and color coordinates of the OLED device are optimized, and the OLED device is high in efficiency and long in service life. Omnibearing water and oxygen blocking can be achieved for the deep blue light OLED device, and the service life of the device is further prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic devices, and in particular to a high-efficiency, long-life deep blue light OLED device. Background Art

[0002] Organic light-emitting diode (OLED) devices have made remarkable progress over the past few decades and are now commercialized in the display and solid-state lighting sectors. With the growing demand for displays and lighting, higher requirements are being placed on the efficiency, stability, and color purity of OLED devices. To provide a wider color space, enabling images and videos to present richer and more realistic colors, the International Telecommunication Union (ITU) has proposed the Broadcasting and Television Service (BT2020) standard. The BT2020 standard requires the International Commission on Illumination (CIE) coordinates of (0.131, 0.046) for blue light emission. However, in full-color OLED research, the development of blue light materials, as one of the three primary colors, is still relatively lagging compared to red and green light materials. Fluorescent materials have limited efficiency, phosphorescent materials are too expensive, and thermally activated delayed fluorescence (TADF) materials have low color purity. The half-width (FWHM) can be narrowed by introducing multiple resonance effects. However, the introduction of multiple resonance effects leads to increased planar rigidity of the material molecules and reduced exciton transition rates. When used as a single light-emitting layer, exciton accumulation is prone to occur, leading to exciton quenching and efficiency roll-off. Therefore, the preparation of deep blue OLED devices that meet both high performance and long life remains a major challenge.

[0003] Currently, the molecular design and development of deep blue light materials has reached a bottleneck. It is relatively difficult to break through the limitations of deep blue light OLED devices from the material perspective alone. Therefore, it is of great significance to propose a high-efficiency and long-life deep blue light OLED device structure.

[0004] Typically, OLED devices have a sandwich structure, consisting of charge transport layers (CTL) on both sides and an organic light-emitting layer sandwiched in the middle. These organic functional layers can be obtained by vacuum hot-dip coating or solution spin coating, and are usually amorphous thin films, including polycrystalline and amorphous. Organic semiconductor single crystal materials have attracted more and more interest in the field of organic optoelectronic materials, and there have been many reports in the fields of OLED, organic light-emitting transistors (OFET), and optically pumped lasers. The prior art is an OLED device top emission structure based on an organic single crystal as a hole transport layer. Due to the outstanding interface characteristics and carrier transport capabilities of the SC-HTL (single crystal-hole transport layer), a red, green, and blue primary color OLED with a maximum EQE of 13.78% is achieved. This is the highest efficiency value of single crystal OLEDs, of which the blue light EQEmax is 7.82%. However, the current blue light single crystal OLED still has many problems, such as insufficient color purity, color coordinates that cannot meet the BT.2020 standard, and slightly low efficiency. Using organic single crystal materials with high carrier mobility as the transport layer of OLEDs, combined with the main material of the light-emitting layer with triplet-triplet annihilation (TTA) characteristics, is of great significance and challenge to achieve high-efficiency and long-life deep blue light OLED devices. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-efficiency, long-life deep blue light OLED device. By selecting an organic single crystal with high mobility, good thermal stability and regular molecular arrangement as the charge transport layer, and doping a host material with TTA properties with an MR-TADF dye as the light-emitting layer, the electroluminescent performance, stability and color coordinates of the OLED device are optimized. In addition, a new packaging method is proposed for the single crystal OLED device structure, which can achieve all-round water and oxygen barrier for the deep blue light OLED device, further improving the device life.

[0006] To achieve the above objectives, the present invention provides a high-efficiency, long-life deep blue light OLED device. The device comprises, from bottom to top, a preset substrate, a first bottom water and oxygen barrier layer, an OLED unit, a third omnidirectional water and oxygen barrier layer, and a cover plate. The OLED unit comprises, from bottom to top, a cathode, an electron transport layer, a light-emitting layer, a second water and oxygen barrier layer, a hole injection layer, and an anode. The second water and oxygen barrier layer is an organic single crystal multifunctional layer. The material of the organic single crystal multifunctional layer is a p-type organic single crystal semiconductor material. The organic single crystal semiconductor material is one of 1,4-bis(4-methylphenyl)benzene (BSB-Me), 2,6-diphenylanthracene (DPA), and 2,5-bis(4-biphenyl)thiophene (BP1T).

[0007] Preferably, the first bottom water and oxygen barrier layer is a photoresist, and the third omnidirectional water and oxygen barrier layer is the same photoresist as the first bottom water and oxygen barrier layer.

[0008] Preferably, the photoresist is one of NOA61, NOA63, and NOA65.

[0009] Preferably, the cover plate is made of ultra-thin quartz glass.

[0010] Preferably, the cathode is one of Ag / Ca with a thickness of 100nm / 5nm, Al / LiF with a thickness of 100nm / 0.5nm, and Al / Liq with a thickness of 100nm / 2nm.

[0011] Preferably, the hole injection layer is one of MoO3 with a thickness of 3-5 nm and 12-hexaazatriphenylene (HAT-CN) with a thickness of 5-10 nm.

[0012] Preferably, the anode is one of Ag with a thickness of 8-15 nm and Au with a thickness of 8-15 nm.

[0013] Preferably, the electron transport layer is one of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), 4,7-diphenyl-1,10-phenanthroline (BPhen), and 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1"-terphenyl]-3,3"-diyl]dipyridine (TmPyPB) with a thickness of 30-50 nm.

[0014] Preferably, the light-emitting layer is a non-polar host material with a thickness of 30-50 nm doped with a multiple resonance-thermally activated delayed fluorescence (MR-TADF) material, the host material is one of 7-(10-phenylanthracene-9-yl) naphtho[1,2-b]benzofuran (BH-16), 2-methyl-9,10-bis(naphthalene-2-yl)anthracene (MADN), 9-(naphthalene-1-yl)-10-(4-(naphthalene-2-yl)phenyl)anthracene, and the MR-TADF is diazo-13-borazinane naphtho[3,2,1-de]anthracene (M-tDABNA), N1,N6-bis(5-(tert-butyl)-2-methylphenyl)-N1,N6-bis(2,4-dimethylphenyl)-pyrene-1,6-diamine (MBD 106), one of 5,9-diphenyl-5,9-dihydro-5,9-diaza-13b-boryloxy[3,2,1-de]anthracene (DABNA-1).

[0015] The advantages and beneficial effects of the present invention using the above-mentioned high-efficiency, long-life deep blue OLED device are:

[0016] 1. The present invention optimizes the device structure of traditional deep blue OLEDs in multiple steps, and uses TTA materials that provide additional exciton upconversion channels to optimize the main material of the light-emitting layer to avoid quenching caused by excessive local high-energy state exciton concentration.

[0017] 2. The present invention uses an organic single crystal material with high carrier mobility and strong water and oxygen barrier ability as the charge transport layer, which improves the efficiency of the OLED device while effectively extending its long working life; and proposes a novel and effective packaging method that can achieve overall protection of the OLED device with the same photoresist, which is used to prevent sensitive materials in the OLED device from being corroded by atmospheric environmental factors such as water and oxygen, thereby further improving the operating stability of the device.

[0018] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a structural diagram of a high-efficiency, long-life deep blue OLED device according to the present invention;

[0020] Figure 2 is a graph showing the relationship between current density, voltage and brightness of OLED devices according to an embodiment of the present invention and a comparative example;

[0021] Figure 3 is a graph showing the relationship between external quantum efficiency and brightness of OLED devices according to the embodiments of the present invention and the comparative example;

[0022] Figure 4 is a graph showing the relationship between electroluminescence intensity and wavelength of OLED devices according to an embodiment of the present invention and a comparative example;

[0023] Figure 5 1 is a brightness decay curve of an OLED device of a comparative example of the present invention at different initial brightnesses;

[0024] Figure 6 is a brightness decay curve of the OLED device of an embodiment of the present invention at different starting brightness;

[0025] Figure 7 This is a lifespan fitting diagram of an OLED device according to a comparative example of the present invention;

[0026] Figure 8 This is a lifespan fitting diagram of an OLED device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0028] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0029] Unless otherwise defined, the reagents, equipment and other materials used in the present invention are all commercially available.

[0030] Example

[0031] like Figure 1 As shown, a high-efficiency, long-life deep blue light OLED device, the device comprises a preset substrate, a first bottom water and oxygen barrier layer, an OLED unit, a third omnidirectional water and oxygen barrier layer, and a high-transmittance cover plate from bottom to top. The OLED unit comprises a cathode, an electron transport layer, a light-emitting layer, a second water and oxygen barrier layer, a hole injection layer, and an anode from bottom to top. The second water and oxygen barrier layer is an organic single crystal multifunctional layer.

[0032] The first bottom water and oxygen barrier layer is a photoresist. The third omnidirectional water and oxygen barrier layer is the same photoresist as the first bottom water and oxygen barrier layer. The photoresist is one of NOA61, NOA63, or NOA65. The high-transmittance cover is made of ultra-thin quartz glass.

[0033] The cathode is one of Ag / Ca (100nm / 5nm), Al / LiF (100nm / 0.5nm), and Al / Liq (100nm / 2nm).

[0034] The hole injection layer is one of MoO3 (3-5nm) and HAT-CN (5-10nm).

[0035] The anode is one of Ag (8-15nm) and Au (8-15nm).

[0036] The electron transport layer is one of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), 4,7-diphenyl-1,10-phenanthroline (BPhen), and 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1"-terphenyl]-3,3"-diyl]dipyridine (TmPyPB), with a thickness of 30-50 nm.

[0037] The emitting layer is a non-polar host material with TTA properties doped with MR-TADF material, with a thickness of 30-50nm. The host material is one of 7-(10-phenylanthracene-9-yl)naphtho[1,2-b]benzofuran (BH-16), 2-methyl-9,10-bis(naphthalene-2-yl)anthracene (MADN), or 9-(naphthalene-1-yl)-10-(4-(naphthalene-2-yl)phenyl)anthracene. MR-TADF is one of diazo-13-borazinonaphtho[3,2,1-de]anthracene (M-tDABNA), N1,N6-bis(5-(tert-butyl)-2-methylphenyl)-N1,N6-bis(2,4-dimethylphenyl)-pyrene-1,6-diamine (MBD 106), and 5,9-diphenyl-5,9-dihydro-5,9-diaza-13b-boryloxy[3,2,1-de]anthracene (DABNA-1).

[0038] The organic single-crystal multifunctional layer is a p-type organic single-crystal semiconductor material, serving as the hole transport layer and water and oxygen barrier layer of the OLED device. The organic single-crystal semiconductor material is one of 1,4-bis(4-methylphenylphenyl)benzene (BSB-Me), 2,6-diphenylanthracene (DPA), or 2,5-bis(4-biphenyl)thiophene (BP1T).

[0039] Organic single crystal semiconductor materials are prepared using the physical vapor transport (PVT) method, with the temperature range set at 500-600K.

[0040] A method for preparing a high-efficiency, long-life deep blue OLED device is as follows: first, a sheet of organic single crystal semiconductor material (second water and oxygen barrier layer) grown by PVT is transferred to a pre-prepared substrate that has been hydrophobically treated; after covering it with an organic layer mask, it is placed in a vacuum thermal coating device, and a metal weight is placed on the back to prevent shadow effects, and the light-emitting layer and electron transport layer are deposited in sequence; then the cathode mask is replaced to deposit a metal composite electrode (cathode); next, a photoresist as the first bottom water and oxygen barrier layer is dripped onto the center area of ​​the cathode and covered with a glass substrate, and the photoresist is spread flat to the pre-prepared After the edge of the substrate, the device is exposed to ultraviolet light to cure the photoresist, and then the device is peeled off from the hydrophobic pre-treated preset substrate and transferred to the glass substrate and photoresist; finally, the device is covered with an anode mask and placed in a coating machine, and the hole injection layer and the anode are deposited in sequence; an appropriate amount of photoresist is dripped into the center area of ​​the anode as a third all-round water and oxygen barrier layer, and covered with a small ultra-thin high-transmittance glass substrate (high-transmittance cover); after the photoresist spreads to the outside of the organic mask evaporation area, the device is exposed to ultraviolet light again to cure the photoresist, completing the device packaging process.

[0041] A method for preparing a high-efficiency, long-life deep blue light OLED device is as follows:

[0042] (1) All the pre-set substrates (substrates) were first ultrasonicated in acetone solution for 30 min, then taken out, wiped clean with an ethanol cotton ball, rinsed with high-purity water with a resistivity of 18 MΩ·cm, blown clean with nitrogen, and dried at 95°C for 10 min for use.

[0043] (2) The organic single crystal semiconductor material (second water and oxygen barrier layer) prepared by PVT is transferred to the pretreated substrate, covered with an organic mask and placed in a vacuum thermal coating machine, and a 20g metal weight is placed on the back of the substrate to prevent the shadow effect.

[0044] (3) The vacuum degree in the coating chamber is lower than 5*10 -4 After pa, the light-emitting layer was evaporated, and the doping ratio of the guest (MR-TADF) material M-tDABNA and the host material BH-16 was 1-3wt%, and the evaporation rates were and The evaporation thickness is 30 nm.

[0045] (4) Evaporation of electron transport layer TmPyPB at a rate of The evaporation thickness is 30 nm.

[0046] (5) Replace the cathode mask to evaporate the Ag / Ca cathode electrode, and the evaporation rates are and The evaporation thicknesses are 5 nm and 100 nm respectively.

[0047] (6) Add 100-300 μL of NOA63 photoresist (the first bottom water and oxygen barrier layer) to the center of the cathode, and evenly cover the photoresist with a glass substrate of the same size as the substrate. After the photoresist has completely spread to the edge, cure it with a 365 nm wavelength UV lamp with an intensity of 10 W for 20 minutes.

[0048] (7) Peel off the cured glass substrate and photoresist, cover with the anode mask and continue evaporation.

[0049] (8) Evaporation of hole injection layer MoO3, the evaporation rate is The evaporation thickness is 5 nm.

[0050] (9) Evaporation of anode Ag, the evaporation rate is The evaporation thickness is 15 nm.

[0051] (10) Add 10-300 μL of NOA63 photoresist (the third all-round water and oxygen barrier layer) to the center of the anode, and evenly cover the photoresist with an ultra-thin glass substrate of the same size as the organic mask. After the photoresist has completely spread to the outside of the organic mask evaporation area, cure it with a 365 nm wavelength UV lamp at a 10 W intensity for 20 minutes.

[0052] Comparative Example

[0053] The structure of the comparative OLED device is as follows: the OLED device comprises, from bottom to top, a quartz glass substrate, an ITO anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode.

[0054] The preparation method of the comparative example OLED device is as follows:

[0055] (1) ITO (indium tin oxide) glass was first ultrasonicated in acetone solution for 30 minutes, then taken out and wiped clean with an ethanol cotton ball, rinsed with high-purity water with a resistivity of 18 MΩ·cm, blown clean with nitrogen, and dried at 95℃ for 10 minutes.

[0056] (2) Cover the anode on the ITO glass and place it in a vacuum coating machine, and place a 20g metal weight on the back of the substrate to prevent the shadow effect.

[0057] (3) The vacuum degree in the coating chamber is lower than 5*10 -4 After pa, the hole injection layer was evaporated at a rate of The evaporation thickness is 5 nm.

[0058] (4) Replace the organic mask and evaporate the light-emitting layer. The doping ratio of the guest material M-tDABNA and the host material BH-16 is 1-3wt%, and the evaporation rate is and The evaporation thickness is 30 nm.

[0059] (5) Evaporation of electron transport layer TmPyPB, the evaporation rate is The evaporation thickness is 30 nm.

[0060] (6) Replace the cathode mask to evaporate the Ag / Ca composite electrode, and the evaporation rates are and The evaporation thicknesses are 5 nm and 100 nm respectively.

[0061] (7) Add 10-300 μL of NOA63 photoresist (water and oxygen barrier layer) to the center of the device and evenly cover the photoresist with an ultra-thin glass substrate of the same size as the organic mask. After the photoresist has completely spread to the outside of the organic mask evaporation area, cure it with a 365 nm wavelength UV lamp at a 10W intensity for 20 minutes.

[0062] The light-emitting devices prepared in the examples and comparative examples were subjected to performance tests.

[0063] Figure 2-Figure 4 The electroluminescent performance diagram of the deep blue OLED device prepared in the comparative example and the deep blue OLED device prepared in the embodiment is shown in FIG. Figure 2-Figure 4 It can be seen that the deep blue light OLED device prepared in the comparative example has a maximum brightness of 7836 candelas per square meter, a maximum external quantum efficiency of 8.11%, a luminescence peak at 463 nm, a half-maximum width of 29 nm, and a luminescence color coordinate (CIE1931) of (0.127, 0.098); the deep blue light OLED device prepared in the example has a maximum brightness of 4474 candelas per square meter, a maximum external quantum efficiency of 9.34%, a luminescence peak at 461 nm, a half-maximum width of 23 nm, and a luminescence color coordinate (CIE1931) of (0.135, 0.069).

[0064] Figure 5 and Figure 6The following are the brightness decay curves of the deep blue OLED devices prepared in the comparative example and the deep blue OLED devices prepared in the example at different starting brightnesses. All devices exhibit good stability. The comparative example deep blue OLED device has an initial brightness of 4641, 2935, and 1106 candelas per square meter, and its LT50 lifespan is 2.08, 3.6, and 24.8 hours, respectively. The deep blue OLED of the example has an initial brightness of 4802, 3205, and 1170 candelas per square meter, and its LT50 lifespan is 4.3, 10.3, and 60.75 hours, respectively. Through fitting, the relationship between the lifespan of the deep blue OLED device and the starting brightness can be obtained.

[0065] Figure 7 and Figure 8 The LT50 lifespan (the time it takes for the brightness to decay to 50% of the initial brightness) and the initial brightness curve of the deep blue OLED devices prepared in the comparative examples and the examples are fitted by the empirical formula (1):

[0066]

[0067] Where L0 is the initial brightness, n is the acceleration factor, τ is the lifetime, and C is a constant. At a brightness of 500 candelas per square meter, the deep blue OLED device prepared in the comparative example has an LT50 lifetime of up to 96.8 hours; the deep blue OLED device of the embodiment has an LT50 lifetime of up to 299 hours, more than three times that of the deep blue OLED device prepared in the comparative example.

[0068] The present invention selects a main material for the light-emitting layer that can provide additional exciton upconversion channels, and replaces the traditional evaporated amorphous thin film hole transport layer with an organic single crystal multifunctional layer; a simple packaging method of covering the organic layer area with a photoresist and an ultra-thin glass substrate improves the external quantum efficiency and operating stability of the deep blue light OLED device.

[0069] Therefore, the present invention adopts the above-mentioned high-efficiency and long-life deep blue light OLED device, selects an organic single crystal with high mobility, good thermal stability and regular molecular arrangement as the charge transport layer, and dopes a host material with TTA properties with MR-TADF dye as the light-emitting layer, while optimizing the electroluminescent performance, stability and color coordinates of the OLED device, and proposes a new packaging method for the single crystal OLED device structure, which can achieve all-round water and oxygen barrier for the deep blue light OLED device, further improving the life of the device.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-efficiency, long-life deep blue OLED device, characterized by: The device comprises, from bottom to top, a preset substrate, a first bottom water and oxygen barrier layer, an OLED unit, a third omnidirectional water and oxygen barrier layer, and a cover plate. The OLED unit comprises, from bottom to top, a cathode, an electron transport layer, a light-emitting layer, a second water and oxygen barrier layer, a hole injection layer, and an anode. The second water and oxygen barrier layer is an organic single crystal multifunctional layer. The material of the organic single crystal multifunctional layer is a p-type organic single crystal semiconductor material. The organic single crystal semiconductor material is one of 1,4-bis(4-methylphenyl)benzene, 2,6-diphenylanthracene, and 2,5-bis(4-biphenyl)thiophene.

2. The high-efficiency, long-life deep blue OLED device according to claim 1, characterized in that: The first bottom water and oxygen barrier layer is a photoresist, and the third omnidirectional water and oxygen barrier layer is the same photoresist as the first bottom water and oxygen barrier layer.

3. The high-efficiency, long-life deep blue OLED device according to claim 1, characterized in that: The photoresist is one of NOA61, NOA63, and NOA65.

4. The high-efficiency, long-life deep blue OLED device according to claim 1, characterized in that: The cover plate is made of ultra-thin quartz glass.

5. The high-efficiency, long-life deep blue OLED device according to claim 1, characterized in that: The cathode is one of Ag / Ca with a thickness of 100 nm / 5 nm, Al / LiF with a thickness of 100 nm / 0.5 nm, and Al / Liq with a thickness of 100 nm / 2 nm.

6. The high-efficiency, long-life deep blue OLED device according to claim 1, characterized in that: The hole injection layer is one of MoO3 with a thickness of 3-5 nm and 12-hexaazatriphenylene with a thickness of 5-10 nm.

7. The high-efficiency, long-life deep blue OLED device according to claim 1, characterized in that: The anode is one of Ag and Au with a thickness of 8-15 nm.

8. The high-efficiency, long-life deep blue OLED device according to claim 1, characterized in that: The electron transport layer is one of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, 4,7-diphenyl-1,10-phenanthroline, and 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1"-terphenyl]-3,3"-diyl]dipyridine with a thickness of 30-50 nm.

9. The high-efficiency, long-life deep blue OLED device according to claim 1, characterized in that: The light-emitting layer is a non-polar host material with a thickness of 30-50 nm doped with a multiple resonance-thermally activated delayed fluorescent material, wherein the host material is one of 7-(10-phenylanthracene-9-yl)naphtho[1,2-b]benzofuran, 2-methyl-9,10-bis(naphthalene-2-yl)anthracene, and 9-(naphthalene-1-yl)-10-(4-(naphthalene-2-yl)phenyl)anthracene, and the multiple resonance-thermally activated delayed fluorescent material is one of diazo-13-borazinonaphtho[3,2,1-de]anthracene, N1,N6-bis(5-(tert-butyl)-2-methylphenyl)-N1,N6-bis(2,4-dimethylphenyl)-pyrene-1,6-diamine, and 5,9-diphenyl-5,9-dihydro-5,9-diaza-13b-boryloxy[3,2,1-de]anthracene.

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