Preparation method of narrow-spectrum blue PLED device

Abstract

According to the preparation method of the narrow-spectrum blue PLED device provided by the invention, under the condition that a polymer luminescent material is not chemically modified, the polymer luminescent material is directly dispersed into an organic main body matrix to inhibit spectrum broadening caused by an aggregation-induced effect of a luminescent polymer, so that the narrow-spectrum blue PLED device is prepared. The light-emitting polymer is dispersed into the organic main body matrix, spectrum broadening caused by the aggregation-induced effect of the light-emitting polymer is avoided, and the light-emitting color purity of the device is improved.

Description

Technical Field

[0001] The present invention belongs to the technical fields of large-area display, preparation of polymer light-emitting diode arrays, etc., and particularly relates to a method for preparing a narrow-spectrum blue PLED device. Background Art

[0002] Polymer array devices have great potential in large-area display and lighting applications. Among them, polyfluorene-based materials have a high photoluminescence quantum yield (about 50%) and good charge transport characteristics in the solid state, and are considered to be one of the most promising candidates for blue-light polymer materials. However, one factor that limits the wide application of polyfluorene-based materials in blue PLED (polymer light-emitting diode) devices is their poor color purity. The aggregation of polyfluorene molecules in the solid film enhances the interaction between their molecules, resulting in the interaction between two identical molecules in the excited state to form an intermolecular exciplex. These exciplexes induce the transition of luminescence from the high-energy band to the low-energy band, thereby generating an additional low-energy emission band in the green spectral region (green band) centered at 530 - 540 nm, seriously broadening the emission spectrum. This broadened emission spectrum reduces the color purity of the device and severely limits the practical application of polyfluorene-based materials in PLEDs.

[0003] In addition, the existing methods for preparing patterned PLEDs are mainly inkjet printing methods, which can achieve on-demand printing, but the poor film uniformity and the limitation of printing resolution severely limit their application in the production of high-performance and high-precision patterned PLEDs. Therefore, there are still many difficulties in realizing a stable, efficient and narrow-spectrum blue PLED array device with good color purity. Summary of the Invention

[0004] In view of this, in response to the first problem raised in the above background art, the present invention provides a method for preparing a narrow-spectrum blue PLED device. Without chemically modifying the polymer light-emitting material, the polymer light-emitting material is directly dispersed into an organic host matrix to inhibit the spectral broadening caused by the self-aggregation induction effect of the luminescent polymer, thereby preparing a narrow-spectrum blue PLED device.

[0005] By dispersing the luminescent polymer into the organic host matrix, it avoids the spectral broadening caused by the self-aggregation induction effect of the luminescent polymer and realizes the improvement of the device's luminescence color purity.

[0006] Further, in response to the first and second problems raised in the above background art, on the basis of the above design, an organic host material is blended with a photosensitizer, and after ultraviolet exposure and development, patterning of the blue polymer light-emitting layer is achieved.

[0007] This solution can not only effectively suppress the green band emission induced by the aggregation of luminescent materials and achieve stable blue emission, but also obtain a PLED array device with significantly better performance through the photocrosslinking of the polymer host material.

[0008] The device obtained by its preparation includes sequentially depositing a hole injection layer, a patterned light-emitting layer, an electron transport layer, and a metal cathode on the ITO layer of a transparent conductive substrate. The narrow-spectrum blue polymer light-emitting layer used therein is prepared by dispersing the luminescent polymer into an organic host matrix to avoid the spectral broadening caused by the self-aggregation effect of the luminescent polymer and improve the color purity of the device emission. In addition, the organic host material is blended with a photosensitizer, and after ultraviolet exposure and development, patterning of the blue polymer light-emitting layer is achieved. The present invention can not only effectively suppress the green band emission induced by the aggregation of luminescent materials and achieve stable blue emission, but also prepare a PLED array device through the photocrosslinking of the polymer host material.

[0009] The technical solution specifically adopted by the present invention to solve its technical problems is: A method for preparing a narrow-spectrum blue PLED device: Without chemically modifying the polymer luminescent material, by directly dispersing the polymer luminescent material into an organic host matrix to inhibit the spectral broadening caused by the self-aggregation induction effect of the luminescent polymer, thereby preparing a narrow-spectrum blue PLED device.

[0010] Furthermore, in the process of preparing the narrow-spectrum blue PLED device, through direct photolithography patterning technology, by blending the organic host material with a photosensitizer, patterning of the blue polymer light-emitting layer is achieved after ultraviolet exposure and development.

[0011] Furthermore, the preparation process of the blue polymer light-emitting layer is as follows: Mix the polymer host material A and the small molecule host material B evenly to obtain the host material ink C; (preferably the mixing ratio is A:B = 5:5 or 7:3 or 2:8) Incorporate the polymer luminescent material D into the host material ink C in a certain proportion to obtain the mixed host-guest luminescent ink E; (the polymer luminescent material D preferably accounts for 3%, 5% or 7%, and the proportion range is required to be less than 10%) Blend the mixed host-guest luminescent ink E and the photosensitizer F evenly in a certain proportion to obtain the photolithographable luminescent ink G; (the photosensitizer F preferably accounts for 1%, 2% or 3%, and the proportion range is required to be less than 5%) Spin-coat the photolithographable luminescent ink G on the target substrate and obtain a light-emitting layer thin film after vacuum drying; Expose the light-emitting layer to ultraviolet light through a mask to cause the photosensitizer F to crosslink with the polymer host material A in the light-emitting layer to form a solid thin film; after development, a light-emitting thin film array is obtained.

[0012] Further, the polymer host material A is one of PVK, TFB, Poly:TPD, and PTAA.

[0013] Further, the small molecule host material B is one of mCP, CBP, and TCTA.

[0014] Further, the polymer light-emitting material D is one of PFO and PFSO.

[0015] Further, the photosensitive additive F is one of dithiodi(benzene azide), benzoin dimethyl ether, bisbenzophenone, and benzophenone.

[0016] Further, it includes the steps of sequentially preparing a hole injection layer, a patterned light-emitting layer, an electron transport layer, and a metal cathode on the ITO layer of the transparent conductive substrate; wherein the method for preparing the patterned light-emitting layer adopts the preparation process of the blue polymer light-emitting layer.

[0017] Further, the hole injection layer material is one of the polymer PEDOT:PSS, molybdenum oxide, nickel oxide, and cuprous thiocyanate; The electron transport layer material is one of TPBi, Poly-TPD, TmPyPB, and B3PyPB.

[0018] The metal cathode material is silver or aluminum.

[0019] And, a narrow-spectrum blue PLED device: obtained by using the method described above.

[0020] Compared with the prior art, the present invention and its preferred solutions at least include the following beneficial effects: (1) It does not involve chemical modification of the polymer light-emitting material. By directly dispersing the polymer light-emitting material into the organic host matrix, the spectral broadening caused by the aggregation-induced effect of the light-emitting polymer itself is effectively suppressed, and a narrow-spectrum blue PLED device is realized; (2) Through the direct photolithography patterning technology, by blending the organic host material with the photosensitizer and realizing the patterning of the blue polymer light-emitting layer after ultraviolet exposure and development, it is easy to fabricate a high-precision narrow-spectrum blue PLED array device; (3) The preparation process adopted is safe, pollution-free, does not generate by-products, and the process is simple and easy to operate. Description of the Drawings

[0021] The following further describes the present invention in detail in conjunction with the drawings and specific embodiments: Figure 1 , Figure 2 , Figure 3It is a schematic diagram of three specific device structures obtained by preparing through the method of the present invention in the embodiments of the present invention; Figure 4 It is a schematic diagram of the preparation process of the patterned light-emitting layer in Embodiment 1, Embodiment 2, and Embodiment 3 of the present invention. Detailed implementation manners

[0022] To make the features and advantages of this patent more obvious and understandable, specific embodiments are hereinafter given and described in detail as follows: It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanations for the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0023] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless otherwise clearly specified in the context, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Embodiment 1 In this embodiment, the purpose is to prepare a narrow-spectrum blue PLED device with the structure as Figure 1 shown, including the following steps: 1) Use the ITO conductive thin film prepared by magnetron sputtering as the anode substrate.

[0025] 2) Place the anode substrate into glass cleaning agent, deionized water, acetone, and ethanol in sequence for ultrasonic treatment, and the ultrasonic time for each time is 10 min.

[0026] 3) Prepare PEDOT:PSS as the hole injection layer by spin coating method, the annealing temperature is 120 °C, and the thickness is about 30 nm.

[0027] 4) As the core design of this embodiment, spin coat ink on the surface of the hole injection layer by spin coating method as the patterned light-emitting layer, and the thickness is about 30 nm. As Figure 4 shown, it specifically includes the following steps: Pre-uniformly mix the host material mCP and PVK in a ratio of 5:5, then mix with the luminescent polymer PFO with a mass ratio of 3%, and finally add 1% photosensitizer and mix evenly. Spin coat into a film under the conditions of a rotation speed of 3000 r and 40 s by a spin coater, make the crosslinkable polymer crosslink through mask exposure, develop with chlorobenzene, and then anneal at 100 °C for 20 minutes to construct the patterned light-emitting layer.

[0028] 5) Prepare TPBi as the electron transport layer by vacuum evaporation, with a thickness of 40 nm.

[0029] 6) Evaporate the LiF / Al electrode by vacuum evaporation, where the thickness of LiF is 1 nm and the thickness of Al is 100 nm.

[0030] Example Two In this example, the aim is to prepare a narrow-spectrum blue PLED device with the structure as shown in Figure 2 and the steps are as follows: 1) Use the ITO conductive thin film prepared by magnetron sputtering as the anode substrate.

[0031] 2) Place the anode substrate successively into glass cleaner, deionized water, acetone, and ethanol for ultrasonic treatment, with the ultrasonic time being 10 min each time.

[0032] 3) Prepare PEDOT:PSS as the hole injection layer by spin coating, with an annealing temperature of 120 °C and a thickness of approximately 30 nm.

[0033] 4) As the core design of this example, spin coat ink on the surface of the hole injection layer as the patterned light-emitting layer, with a thickness of approximately 30 nm. As shown in Figure 4 the specific steps are as follows: Pre-uniformly mix the host materials mCP and PVK in a ratio of 3:7, then mix with 5% of the light-emitting polymer PFO by mass, and finally add 2% of the photosensitizer and mix evenly. Spin coat into a film under the conditions of a rotational speed of 3000 r and a time of 40 s using a spin coater. Crosslink the crosslinkable polymer by mask exposure, develop with chlorobenzene, and then anneal at 100 °C for 20 minutes to construct the patterned light-emitting layer.

[0034] 5) Prepare TmPyPB as the electron transport layer by vacuum evaporation, with a thickness of 40 nm.

[0035] 6) Evaporate the LiF / Al electrode by vacuum evaporation, where the thickness of LiF is 1 nm and the thickness of Al is 100 nm.

[0036] Example Three In this example, the aim is to prepare a narrow-spectrum blue PLED device with the structure as shown in Figure 3 and the steps are as follows: 1) Use the ITO conductive thin film prepared by magnetron sputtering as the anode substrate.

[0037] 2) Place the anode substrate successively into glass cleaner, deionized water, acetone, and ethanol for ultrasonic treatment, with the ultrasonic time being 10 min each time.

[0038] 3) PEDOT:PSS was prepared by spin coating as the hole injection layer, with an annealing temperature of 120 °C and a thickness of about 30 nm.

[0039] 4) As the core design of this embodiment, ink was spin coated on the surface of the hole transport layer as the patterned light-emitting layer, with a thickness of about 30 nm. As Figure 4 shown, it specifically includes the following steps: The host material mCP and TFB were uniformly mixed in a ratio of 5:5 in advance, then mixed with 3% by mass of the light-emitting polymer PFO, and finally 1% photosensitizer was added and blended evenly. A film was formed by spin coating using a spin coater at a rotation speed of 3000 r and a time of 40 s. The crosslinkable polymer was crosslinked by mask exposure, developed with chlorobenzene, and annealed at 100 °C for 20 minutes to construct the patterned light-emitting layer.

[0040] 5) TPBi was deposited by vacuum evaporation as the electron transport layer, with a thickness of 40 nm.

[0041] 6) LiF / Al was deposited by vacuum evaporation as the cathode, where the thickness of LiF is 1 nm and the thickness of Al is 100 nm.

[0042] It should be noted that unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning understood by those of ordinary skill in the field to which the present invention belongs. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. The terms such as "including" or "comprising" mean that the elements or objects appearing before the term cover the elements or objects listed after the term and their equivalents, without excluding other elements or objects. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left", "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0043] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

[0044] This patent is not limited to the above-mentioned optimal implementation mode. Anyone inspired by this patent can obtain other various forms of a method for preparing a narrow-spectrum blue PLED device. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by this patent.

Claims

1. A method for preparing a narrow spectrum blue PLED device, characterized in that: Without chemically modifying the polymer light-emitting material, the polymer light-emitting material is directly dispersed into an organic host matrix to suppress the spectrum broadening caused by the aggregation-induced effect of the light-emitting polymer itself, thereby preparing a narrow-spectrum blue PLED device.

2. The method for preparing a narrow spectrum blue PLED device according to claim 1, characterized in that: In the process of preparing the narrow spectrum blue PLED device, the blue polymer light-emitting layer is patterned by using direct photolithography patterning technology, blending an organic host material with a photosensitizer, and then ultraviolet exposure and development.

3. The method for preparing a narrow spectrum blue PLED device according to claim 2, characterized in that: The preparation process of the blue polymer light-emitting layer is as follows: The polymer main material A and the small molecule main material B are mixed evenly to obtain the main material ink C; Adding the polymer luminescent material D into the host material ink C at a ratio of less than 10% to obtain a mixed host-guest luminescent ink E; The mixed host-guest luminescent ink E is uniformly mixed with a photosensitizer F accounting for less than 5% to obtain a photolithographic luminescent ink G; Spin coating the photolithographic luminescent ink G on a target substrate, and vacuum drying to obtain a luminescent layer film; The light-emitting layer is exposed to ultraviolet light through a mask, so that the photosensitizer F reacts with the polymer main material A in the light-emitting layer to form a stable film; After development, a light-emitting thin film array is obtained.

4. The method for preparing a narrow spectrum blue PLED device according to claim 3, characterized in that: The polymer main material A is one of PVK, TFB, Poly:TPD, and PTAA.

5. The method for preparing a narrow spectrum blue PLED device according to claim 3, characterized in that: The small molecule main material B is one of mCP, CBP and TCTA.

6. The method for preparing a narrow spectrum blue PLED device according to claim 3, characterized in that: The polymer light-emitting material D is one of PFO and PFSO.

7. The method for preparing a narrow spectrum blue PLED device according to claim 3, characterized in that: The photosensitive additive F is one of disulfide bis(phenyl azide), benzoin dimethyl ether, bis(dibenzophenone) and benzophenone.

8. The method for preparing a narrow spectrum blue PLED device according to claim 3, characterized in that: include: The step of sequentially preparing a hole injection layer, a patterned light-emitting layer, an electron transport layer and a metal cathode on the ITO layer of the transparent conductive substrate; The method for preparing the patterned light-emitting layer adopts the preparation process of the blue polymer light-emitting layer.

9. The method for preparing a narrow spectrum blue PLED device according to claim 8, characterized in that: The hole injection layer material is one of polymer PEDOT:PSS, molybdenum oxide, nickel oxide, and cuprous thiocyanate; The electron transport layer material is one of TPBi, Poly-TPD, TmPyPB and B3PyPB; The metal cathode material is silver or aluminum.

10. A narrow spectrum blue PLED device, characterized in that: The method is prepared by any one of claims 1 to 9.

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