Electroluminescent device with low driving voltage and preparation method thereof

Abstract

The invention belongs to the technical field of alternating-current electroluminescence, and discloses a low-driving-voltage electroluminescent device which comprises a substrate, and a bottom electrode, a high-k bottom dielectric layer, a high-k luminescent layer, a transparent top dielectric layer and a top transparent electrode which are sequentially stacked on the substrate. The invention also discloses a preparation method of the low-driving-voltage electroluminescent device, and the method comprises the following steps: S1, printing the conductive slurry on the substrate, and drying and curing the conductive slurry to obtain the bottom electrode; s2, printing a high-k bottom dielectric layer on the bottom electrode; s3, printing a high-k light-emitting layer on the high-k bottom dielectric layer; s4, printing a transparent top dielectric layer on the high-k light-emitting layer; s5, preparing a top transparent electrode above the transparent top dielectric layer; and S6, packaging to complete the preparation of the electroluminescent device. According to the electroluminescent device prepared by the method, the voltage is reduced to a human body safety voltage of 35 V, and the brightness is improved to 175 cd / m < 2 >.

Description

Technical Field

[0001] The invention belongs to the technical field of alternating current electroluminescence, and in particular relates to an electroluminescent device with a low driving voltage and a preparation method thereof. Background Art

[0002] Flexible AC electroluminescent devices have the characteristics of good flexibility, high mechanical strength, simple structure, low cost and high mechanical stability. They are an important component of future wearable integrated display device systems and have great commercial prospects. However, flexible AC electroluminescent devices still face considerable challenges in practical applications, and there are still many problems that need to be solved. For example, the current operating voltage of the device is relatively high (110 V AC), which far exceeds the safety voltage of the human body (36 V), which greatly limits its application in the field of wearable electronics.

[0003] At present, the main way to reduce the voltage is to reduce the dielectric constant of the device's light-emitting layer, or to add two additional dielectric layers. For example, adding high-dielectric barium titanate nanoparticles to the light-emitting layer increases the dielectric constant of the light-emitting layer, so that the luminous intensity can be 113 cd / m at a voltage of 35 V. 2 , which can meet the standards for indoor use (ACS Materials Lett. 2019, 1, 511-518).

[0004] There are generally three structures of AC electroluminescence: (1) transparent conductive layer / dielectric layer / luminescent layer / dielectric layer / conductive layer; (2) transparent conductive layer / luminescent layer / dielectric layer / conductive layer; (3) transparent conductive layer / luminescent layer / conductive layer.

[0005] The prior art usually only increases the dielectric constant of the dielectric layer or the light-emitting layer, for example, only adding barium titanate to the dielectric layer to increase the dielectric constant; or only adding barium titanate to the light-emitting layer to increase the dielectric constant. At the same time, most of the literature does not use a suitable process to deliberately reduce the film thickness of the dielectric layer. Therefore, although the dielectric constant is large, the brightness of the light is still low due to the excessive thickness of the film, and the driving voltage is still large. Summary of the invention

[0006] In view of this, the object of the present invention is to provide an electroluminescent device with low driving voltage and a preparation method thereof. The present invention aims to solve the problem of low luminous brightness and high driving voltage of the existing electroluminescent device.

[0007] To achieve the above object, the present invention provides a method for preparing an electroluminescent device with a low driving voltage, comprising the following steps: S1. Printing a conductive paste on a substrate, drying and curing, to obtain a bottom electrode; S2. Printing a high-k bottom dielectric layer on the bottom electrode; S3. Printing a high-k light-emitting layer on the high-k bottom dielectric layer; S4. Printing a transparent top dielectric layer on the high-k light-emitting layer; S5. Preparing a top transparent electrode above the transparent top dielectric layer; S6. Packaging, completing the preparation of the electroluminescent device.

[0008] Furthermore, in step S1, the substrate includes at least one of PET, colorless PI, PEN, silicon wafer, glass, and cloth; and the conductive paste includes at least one of silver layer, PEDOT, carbon layer, ITO, stainless steel, and aluminum.

[0009] Further, in step S2, the high-k bottom dielectric layer is a high-k composite material, the k value of the high-k bottom dielectric layer is 5-100, and the thickness is 0.1-10 microns; The high-k composite material is a mixture of two or more materials, and is characterized by containing inorganic particles and organic high molecular polymers; The inorganic particles are barium titanate or titanium dioxide; The organic high molecular polymer includes at least one of PMMA, PVDF, TPU, HSEBS and PMDS.

[0010] Further, in step S3, the high-k light-emitting layer includes phosphor materials, organic high polymers and inorganic particles, and the k value of the high-k light-emitting layer is 5-100 and the thickness is 5-200 microns; The phosphor material includes at least one of zinc sulfide-based phosphor particles, oxide-based phosphor particles, and nitride-based phosphor particles; The inorganic particles are barium titanate or titanium dioxide; The organic high molecular polymer includes at least one of PMMA, PVDF, TPU, HSEBS and PMDS.

[0011] Furthermore, in step S4, the material of the transparent top dielectric layer includes at least one of PMMA, PVDF, TPU, HSEBS, and PMDS.

[0012] Furthermore, in step S5, the top transparent electrode includes at least one of metal nanowires, metal grids, CNTs, ITO, and PEDOT.

[0013] Furthermore, in step S6, the material used for packaging includes at least one of TPU, PVDC, PE, PET, and PI.

[0014] The present invention also provides an electroluminescent device with a low driving voltage, which is made by the above-mentioned preparation method of the electroluminescent device with a low driving voltage, and includes a substrate, a bottom electrode, a high-k bottom dielectric layer, a high-k light-emitting layer, a transparent top dielectric layer and a top transparent electrode stacked in sequence on the substrate.

[0015] The beneficial effects of the present invention are: The present invention provides an electroluminescent device with low driving voltage and a preparation method thereof. By adding inorganic particles with high dielectric constant to the bottom dielectric layer and the light-emitting layer at the same time and adding a PVDF dielectric layer on the top, the dielectric constant is greatly improved. At the same time, screen printing is used to control the film thickness (even if the dielectric constant is large, if the film thickness is very thick, high brightness and low voltage driving cannot be achieved), thereby reducing the voltage to 35 V, a safe voltage for human body, and increasing the brightness to 175 cd / m 2 The electroluminescent device prepared by the method of the present invention has a high brightness at the same voltage (when driven at 110 V, the brightness is 1448 cd / m 2 ).

[0016] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a flow chart for preparing an electroluminescent device with a low driving voltage; Figure 2 is the dielectric constant of the bottom dielectric layer, the light-emitting layer, and the top dielectric layer. DETAILED DESCRIPTION

[0018] In order to make the technical solutions, advantages and purposes of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of this application.

[0019] like Figure 1 As shown, the present invention provides a method for preparing an electroluminescent device with a low driving voltage, comprising the following steps: S1. Printing a conductive paste on a substrate, drying and curing, to obtain a bottom electrode; S2. Printing a high-k bottom dielectric layer on the bottom electrode; S3. Printing a high-k light-emitting layer on the high-k bottom dielectric layer; S4. Printing a transparent top dielectric layer on the high-k light-emitting layer; S5. Preparing a top transparent electrode above the transparent top dielectric layer; S6. Packaging, completing the preparation of the electroluminescent device.

[0020] As a preference of this embodiment, in step S1, the substrate can be PET, colorless PI, PEN, silicon wafer, glass, cloth and other substrates; the bottom conductive layer can be a silver layer, PEDOT, carbon layer, ITO, stainless steel, aluminum and other conductive materials.

[0021] As a preferred embodiment of this embodiment, in step S2, the high-k bottom dielectric layer may be a composite material or a single high-k material; the k value of the high-k bottom dielectric layer is between 5 and 100, and the thickness is about 0.1 to 10 microns; High-k composite materials are a mixture of two or more materials, and are characterized by containing inorganic particles and organic polymers; The inorganic particles may be barium titanate, titanium dioxide, etc.; The organic high molecular polymer may be PMMA, PVDF, TPU, HSEBS, PMDS and the like.

[0022] As a preferred embodiment of this embodiment, in step S3, the high-k light-emitting layer is mainly composed of a mixture of phosphor material, organic high polymer and inorganic particles, with a k value of 5-100 and a thickness of about 5-200 microns; The inorganic particles may be barium titanate, titanium dioxide, etc.; The phosphor material may be zinc sulfide-based phosphor particles, oxide-based phosphor particles, nitride-based phosphor particles, etc.; The organic high molecular polymer may be PMMA, PVDF, TPU, HSEBS, PMDS and the like.

[0023] As a preference of this embodiment, in step S4, the transparent top dielectric layer may be PMMA, PVDF, TPU, HSEBS, PMDS or the like.

[0024] As a preference of this embodiment, in step S5, the top transparent electrode may be metal nanowires, metal grids, CNTs, ITO, PEDOT, etc.

[0025] As a preference of this embodiment, in step S6, the packaging material may be TPU, PVDC, PE, PET, PI, etc.

[0026] Figure 2is the dielectric constant of the bottom dielectric layer, the light-emitting layer and the top dielectric layer. In the present application, the dielectric constant of the light-emitting layer is about 80.

[0027] The present invention also provides an electroluminescent device with a low driving voltage, which is made by the above-mentioned preparation method of the electroluminescent device with a low driving voltage, and includes a substrate, a bottom electrode, a high-k bottom dielectric layer, a high-k light-emitting layer, a transparent top dielectric layer and a top transparent electrode stacked in sequence on the substrate. Example 1

[0028] This embodiment provides a method for preparing a high-brightness flexible alternating current electroluminescent device based on a silver electrode: (1) Select a fabric with a thickness of 0.1-1 mm as the substrate; (2) Using a heat press machine on the fabric, heat press it into a film with a thickness of 10-50 μm, the heat press temperature is 150 °C, the heat press time is 3 minutes, and the surface of the fabric is flattened; (3) Screen-printing conductive silver paste on the fabric as the bottom electrode and drying it at 130 °C / 10 min; (4) Screen-print a mixture of barium titanate and PVDF as a high-k bottom dielectric layer above the bottom electrode and dry it at 130 °C / 10 min; (5) Screen printing a mixture of ZnS:Cu, barium titanate, and PVDF as a high-k light-emitting layer on top of the high-k bottom dielectric layer and drying at 130 °C / 10 min; (6) Screen print PVDF solution as the top dielectric layer above the high-k light-emitting layer and dry it at 130 °C / 10 min; (7) Spraying silver nanowires as the top electrode on top of the top dielectric layer and drying at 80 °C / 10 min; (8) Use TPU film to complete device packaging.

[0029] In this embodiment, barium titanate is added to both the bottom dielectric layer and the light-emitting layer, and a PVDF dielectric layer is added to the top, which greatly improves the dielectric constant. At the same time, screen printing is used to control the appropriate film thickness. While reducing the voltage to the human safety voltage of 35 V, the brightness is increased to 175 cd / m 2 .

[0030] Example 2 This embodiment provides a method for preparing a two-sided luminous AC electroluminescent device based on a metal grid: (1) Select PET with a thickness of 5-15 microns as the substrate; (2) Applying embossing glue on the PET substrate, completing embossing through a nickel plate, and obtaining a grid groove with a groove depth of 1-15 μm, a width of 0.2-10 μm, a primer thickness of 0-5 μm, and a channel width of 1-50 μm; (3) Scrape a thin layer of gold nanoparticles into the groove and dry it at 120 °C / 30 min; (4) Electroplating copper to obtain a high-conductivity and high-transmittance copper metal grid; (5) Screen-printing a mixture of titanium dioxide and PDMS as a high-k bottom dielectric layer on top of the high-conductivity and high-transmittance copper metal grid and drying it at 130 °C / 10 min; (6) Screen printing a mixture of ZnS:Mn, titanium dioxide, and PDMS on top of the high-k bottom dielectric layer as a high-k light-emitting layer and drying at 130 °C / 10 min; (7) Screen print PVA solution on top of the high-k light-emitting layer as the top dielectric layer and dry it at 130 °C / 10 min; (8) Use the same metal grid and PET as the top electrode and packaging layer above the top dielectric layer to complete the device packaging.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the protection scope of the present invention.

Claims

1. A method for preparing an electroluminescent device with a low driving voltage, characterized in that: The following steps are involved: S1. Printing a conductive paste on a substrate, drying and curing, to obtain a bottom electrode; S2. Printing a high-k bottom dielectric layer on the bottom electrode; S3. Printing a high-k light-emitting layer on the high-k bottom dielectric layer; S4. Printing a transparent top dielectric layer on the high-k light-emitting layer; S5. Preparing a top transparent electrode above the transparent top dielectric layer; S6. Packaging, completing the preparation of the electroluminescent device.

2. The method for preparing a low driving voltage electroluminescent device according to claim 1, characterized in that: In the step S1, the substrate includes at least one of PET, colorless PI, PEN, silicon wafer, glass, and cloth; the conductive paste includes at least one of silver layer, PEDOT, carbon layer, ITO, stainless steel, and aluminum.

3. The method for preparing a low driving voltage electroluminescent device according to claim 2, characterized in that: In the step S2, the high-k bottom dielectric layer is a high-k composite material, the k value of the high-k bottom dielectric layer is 5-100, and the thickness is 0.1-10 microns; The high-k composite material is a mixture of two or more materials, and is characterized by containing inorganic particles and organic high molecular polymers; The inorganic particles are barium titanate or titanium dioxide; The organic high molecular polymer includes at least one of PMMA, PVDF, TPU, HSEBS and PMDS.

4. The method for preparing a low driving voltage electroluminescent device according to claim 3, characterized in that: In the step S3, the high-k light-emitting layer includes phosphor materials, organic high polymers and inorganic particles, and the k value of the high-k light-emitting layer is 5-100 and the thickness is 5-200 microns; The phosphor material includes at least one of zinc sulfide-based phosphor particles, oxide-based phosphor particles, and nitride-based phosphor particles; The inorganic particles are barium titanate or titanium dioxide; The organic high molecular polymer includes at least one of PMMA, PVDF, TPU, HSEBS and PMDS.

5. The method for preparing a low driving voltage electroluminescent device according to claim 4, characterized in that: In the step S4, the material of the transparent top dielectric layer includes at least one of PMMA, PVDF, TPU, HSEBS, and PMDS.

6. The method for preparing a low driving voltage electroluminescent device according to claim 5, characterized in that: In the step S5, the top transparent electrode includes at least one of metal nanowires, metal grids, CNTs, ITO, and PEDOT.

7. The method for preparing a low driving voltage electroluminescent device according to claim 6, characterized in that: In step S6, the material used for packaging includes at least one of TPU, PVDC, PE, PET, and PI.

8. An electroluminescent device with low driving voltage, characterized in that: The device is made by the preparation method of the low driving voltage electroluminescent device according to any one of claims 1 to 7, and comprises a substrate, a bottom electrode, a high-k bottom dielectric layer, a high-k light-emitting layer, a transparent top dielectric layer and a top transparent electrode sequentially stacked on the substrate.

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