Internal light extraction structure and preparation method thereof

Abstract

The present invention discloses an internal light extraction structure and a preparation method thereof, comprising: a substrate, a functional layer arranged on the substrate, the functional layer comprising a metal nanoparticle layer, a nanofiller layer, and a planarization layer composed of a polymer. The metal nanoparticle layer provided by the present invention has a certain ductility, and when water and oxygen invade, it absorbs water and oxygen and forms a pore structure, which not only improves the light extraction effect, increases the efficiency of the organic electroluminescent device, but also has a good packaging effect; and the presence of the nanofiller layer can prevent the further diffusion of water and oxygen, so that the internal light extraction structure not only has a high extraction efficiency, but also has a good water blocking and water absorption effect.

Description

Technical Field

[0001] The present invention relates to the technical field of light extraction, and in particular to an internal light extraction structure and a preparation method thereof. Background Art

[0002] Organic light-emitting devices (OLED) use organic light-emitting materials and are active light-emitting devices. They have the advantages of low power consumption, wide color gamut, and thinner size, and are expected to become the next generation of mainstream lighting and flat panel display technology. Currently, organic light-emitting technology has been widely used in small-sized panels such as smartphone displays.

[0003] The light-emitting principle of OLED is that when a forward DC voltage is applied to the two electrodes, electrons and holes are injected into the organic film from the cathode and anode respectively. Under the action of the electric field, the carriers migrate towards each other in the organic semiconductor material, and excitons are generated after meeting. The excitons recombine and emit light in the light-emitting area, and the emitted light is randomly emitted in all directions. During the propagation process, due to the effect of total reflection, an external mode (light is emitted from the substrate surface), a substrate waveguide mode, and an ITO / organic layer waveguide mode are formed. In traditional classical devices, the proportions of external mode, substrate waveguide mode, and ITO / organic layer waveguide mode are 20%, 30%, and 50%, respectively. The light emitted from the substrate surface (external mode) is only 20%, which is far from meeting the needs of lighting and display applications. Therefore, it is particularly necessary to explore methods to improve the light extraction efficiency.

[0004] Generally, light extraction methods can be divided into two categories: external light extraction method and internal light extraction method. The external light extraction method is applied to the outside of the device, which is simple and easy to implement. It can be carried out separately from the device preparation process. It is low-cost and easy to mass-produce, but it can only extract the light trapped in the glass substrate, which limits the light enhancement efficiency. The internal light extraction structure is built inside the device, which can extract the light lost in the optical waveguide mode in the device. Therefore, the ability of the internal light extraction method to improve the light extraction efficiency can be higher than that of the external light extraction method.

[0005] However, the introduction of internal light extraction technology usually leads to a deterioration in the packaging performance of the organic electroluminescent device. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides an internal light extraction structure and a preparation method thereof, which can improve the light extraction efficiency and enhance the packaging effect of the device.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] An internal light extraction structure described in the present invention comprises: a substrate, a functional layer arranged on the substrate, wherein the functional layer comprises a metal nanoparticle layer, a nanofiller layer, and a planarization layer composed of a polymer.

[0009] Optionally, the metal nanolayer includes at least one of gold, platinum, copper, silver, tungsten, aluminum, cesium, and palladium.

[0010] Optionally, the nanofiller layer includes at least one of titanium dioxide, zirconium oxide, silicon oxide and aluminum oxide.

[0011] Optionally, the planarization layer includes at least one of polyvinyl alcohol, polysiloxane and polyimide.

[0012] Optionally, the functional layer consists of cesium, titanium dioxide and polyvinyl alcohol.

[0013] Optionally, the particle size of the metal nanoparticles in the metal nanoparticle layer is 1-20 nm; the particle size of the nanofiller particles in the nanofiller layer is 50-800 nm; and the thickness of the functional layer is 100 nm-10 μm.

[0014] Optionally, the coverage area of ​​the nanofiller layer is larger than the coverage area of ​​the metal nanoparticle layer; the coverage area of ​​the planarization layer is larger than the coverage area of ​​the nanofiller layer; the refractive index of the planarization layer in the output light band is smaller than the refractive index of the substrate and the refractive index of the nanofiller layer.

[0015] Optionally, the metal nanoparticles in the metal nanoparticle layer and the nanoparticles in the nanofiller layer are doped in the planarization layer. In terms of mass fraction, the doping ratio of the metal nanoparticles in the planarization layer is 1-40%, and the doping ratio of the nanofiller particles in the planarization layer is 10-60%.

[0016] Optionally, the metal nanoparticles are doped in the nanofiller layer, and the doping ratio of the metal nanoparticles in the nanofiller layer is 0.5-10% by mass fraction.

[0017] The method for preparing the internal light extraction structure of the present invention comprises the following steps:

[0018] 1) Preparing a metal nanoparticle layer and a nanofiller layer on a substrate;

[0019] 2) Prepare a planarization layer by spin coating, magnetron sputtering or printing.

[0020] Optionally, after preparing a planarization layer, the following steps are further included:

[0021] 1) writing the metal nanoparticle layer and the nanofiller layer into the planarization layer by means of a field emission electron gun, an ion beam or a laser;

[0022] 2) Etching the planarization layer flat by reactive ion etching or plasma etching.

[0023] Optionally, the metal nanoparticles are mixed with the nanofiller layer by vacuum evaporation or coating; or, the metal nanoparticle layer is prepared on the substrate by vacuum evaporation, coating or electron beam evaporation, and then the nanofiller layer is prepared on the metal nanoparticle layer by vacuum evaporation, coating or sputtering.

[0024] The above technical solution of the present invention has the following advantages compared with the prior art:

[0025] The metal nanoparticles provided by the present invention have a certain ductility, and when water and oxygen invade, they will absorb water and oxygen and form a pore structure, which not only improves the light extraction effect and increases the efficiency of the organic electroluminescent device, but also has a good packaging effect; and the presence of the nanofiller layer can prevent the further diffusion of water and oxygen. Such an internal light extraction structure not only has a high extraction efficiency, but also has a good water blocking and water absorption effect. In addition, the function of the planarization layer is to prevent the protrusion of the internal extraction structure from affecting the stability of the organic electroluminescent device and prevent short circuits caused by the protrusions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

[0027] Figure 1 is a schematic structural diagram of the internal light extraction structure of embodiment 1 of the present invention;

[0028] Figure 2 is a schematic structural diagram of an internal light extraction structure of Embodiment 2 of the present invention;

[0029] Figure 3 is a schematic structural diagram of an internal light extraction structure of Embodiment 3 of the present invention;

[0030] Figure 4 is a schematic structural diagram of an internal light extraction structure of Embodiment 4 of the present invention;

[0031] Figure 5 is a flow chart of the preparation process of the internal light extraction structure of Example 4 of the present invention;

[0032] Figure 6 It is a schematic structural diagram of an organic electroluminescent device with an internal light extraction structure according to the present invention;

[0033] Figure 7 It is a schematic diagram of the structure of an organic electroluminescent device in a comparative example of the present invention. DETAILED DESCRIPTION

[0034] The following describes the implementation of the present invention through specific embodiments, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0035] The following is a detailed decomposition description of the specific implementation process of the invention of the present application in combination with the specification and the accompanying drawings. It should be noted that the same or similar reference numerals throughout represent the same or similar elements or elements with similar functions. The embodiments described below with reference to the accompanying drawings are examples and are only used to describe the present invention, and cannot be understood as limiting conditions for the application of the present invention.

[0036] The present invention provides an internal light extraction structure, such as Figure 1-4 As shown, it comprises: a substrate 1, a functional layer 5 arranged on the substrate, wherein the functional layer 5 comprises a metal nanoparticle layer 2, a nanofiller layer 3, and a planarization layer 4 composed of a polymer.

[0037] As an embodiment of the present invention, in this embodiment, the metal nanoparticle layer 2 adopts a ductile metal material. Specifically, the metal nanoparticle layer 2 includes at least one of gold, platinum, copper, silver, tungsten, aluminum, palladium, and cesium. Preferably, the material of the metal nanoparticle layer 2 is cesium.

[0038] The nanofiller layer 3 is made of a material with a high refractive index and high water resistance. Specifically, the nanofiller layer 3 includes at least one of titanium dioxide, zirconium oxide, silicon oxide, and aluminum oxide. Preferably, the material of the nanofiller layer 3 is titanium dioxide.

[0039] The planarization layer 4 is made of a polymer material with strong polymerizability. Specifically, the planarization layer 4 includes at least one of polyvinyl alcohol, polysiloxane and polyimide. Preferably, the material of the planarization layer 4 is polyvinyl alcohol.

[0040] Optionally, the planarization layer 4 has a transmittance of greater than or equal to 85% under visible light, and a refractive index of 1 to 2. Preferably, the refractive index of the planarization layer 4 in the outgoing light band is smaller than the refractive index of the substrate 1 and the refractive index of the nanofiller layer 3 .

[0041] In a preferred embodiment of the present invention, the particle size of the metal nanoparticles in the metal nanoparticle layer 2 is 1-20nm; the metal nanoparticle layer 2 within this range can have stronger ductility and excellent water absorption capacity; the particle size of the nanofiller particles in the nanofiller layer 3 is 50-800nm; the nanofiller layer 3 within this range not only has a higher light extraction ability, but also can effectively block the water vapor diffusion of the metal nanoparticle layer; the thickness of the functional layer 5 is 100nm-10μm; the functional layer 5 within this range has better flatness and aggregation ability, which can further prevent the diffusion of water vapor.

[0042] In a preferred embodiment of the present invention, Figure 1 As shown, the coverage area of ​​the nanofiller layer 3 is greater than the coverage area of ​​the metal nanoparticle layer 2; the coverage area of ​​the planarization layer 4 is greater than the coverage area of ​​the nanofiller layer 3. Preferably, the distance between the coverage edge of the nanofiller layer 3 on the substrate and the coverage edge of the metal nanoparticle layer 2 on the substrate is greater than or equal to 0.1 μm. This ensures that the nanofiller layer completely blocks the diffusion of water vapor after the ductile metal particles in the metal nanoparticle layer 2 absorb water.

[0043] In one embodiment of the present invention, Figure 2 As shown, the metal nanoparticles in the metal nanoparticle layer 2 and the nanofiller particles in the nanofiller layer 3 are doped in the planarization layer 4, the doping ratio of the metal nanoparticle layer 2 in the planarization layer 4 is 1-40%, and the doping ratio of the nanofiller layer 3 in the planarization layer 4 is 10-60%; preferably, the doping ratio of the metal nanoparticle layer 2 is 1-10%, and the doping ratio of the nanofiller layer 3 is 10-40%.

[0044] In one embodiment of the present invention, Figure 3 As shown, the metal nanoparticles are doped in the nanofiller layer 3, and the doping ratio of the metal nanoparticles in the nanofiller layer 3 is 0.5-10%. Preferably, the doping ratio of the metal nanoparticles in the nanofiller layer 3 is 1-5%.

[0045] Another aspect of the present invention provides a method for preparing an internal light extraction structure, comprising the following steps:

[0046] 1) preparing a metal nanoparticle layer 2 and a nanofiller layer 3 on a substrate 1;

[0047] 2) After the preparation is completed, a planarization layer 4 is prepared by spin coating, magnetron sputtering or printing.

[0048] Preferably, Figure 4 As shown, the method for preparing the internal light extraction structure provided by the present invention further includes the following steps:

[0049] 1) After the planarization layer 4 is prepared, the metal nanoparticle layer 2 and the nanofiller layer 3 are written into the planarization layer by means of a field emission electron gun, an ion beam or a laser;

[0050] 2) After the preparation is completed, the planarization layer 4 is etched flat by reactive ion etching or plasma etching.

[0051] In this embodiment, the interface roughness can be controlled by the intensity of the field emission electron gun, the intensity range of the field emission electron gun is 2~10KV, and the current range is 5~20 uA. The shape of the planarization layer 4 after etching by the field emission electron gun, ion beam or laser treatment is as follows: Figure 4 The functional layer 5 formed after the treatment has a better light extraction effect, and further increases the path for water and oxygen expansion, thereby further improving the packaging effect and efficiency of the functional layer 5.

[0052] Optionally, the metal nanoparticle layer 2 and the nanofiller layer 3 can be mixed and prepared simultaneously by vacuum evaporation or coating; or, the metal nanoparticle layer 2 is prepared on the substrate by vacuum evaporation, coating or electron beam evaporation, and then the nanofiller layer 3 is prepared on the metal nanoparticle layer 3 by vacuum evaporation, coating or sputtering.

[0053] Example 1

[0054] An internal light extraction structure, such as Figure 1 As shown, it includes: a substrate 1, a functional layer 5 arranged on the substrate, the functional layer 5 includes a metal nanoparticle layer 2, a nanofiller layer 3, and a planarization layer 4 composed of a polymer. The coverage area of ​​the nanofiller layer 3 is larger than the coverage area of ​​the metal nanoparticle layer 2; the coverage area of ​​the planarization layer 4 is larger than the coverage area of ​​the nanofiller layer 3. Preferably, the distance between the covering edge of the nanofiller layer 3 on the substrate and the covering edge of the metal nanoparticle layer 2 on the substrate is greater than or equal to 0.1μm. To ensure that the ductile metal particles in the metal nanoparticle layer 2 absorb water, the nanofiller layer completely blocks the diffusion of water vapor. Specifically, as Figure 1 As shown, the functional layer 5 includes a metal nanoparticle layer 2 evaporated on a glass substrate, the material of which is cesium and has a thickness of 20 nm; a nanofiller layer 3 evaporated on the metal nanoparticle layer 2, the material of which is titanium dioxide and has a thickness of 800 nm; and a planarization layer 4 coated on the nanofiller layer 3, the material of which is polyvinyl alcohol and has a thickness of 5 μm.

[0055] This embodiment also provides an organic electroluminescent device, such as Figure 6As shown, it includes a glass substrate 1 and a functional layer 5 (i.e., the internal light extraction structure provided in Example 1), an organic electroluminescent device layer and a glass cover. The organic electroluminescent device layer includes: an anode ITO; a hole transport layer NPB with a thickness of 40nm; a light emitting layer of Alq 3 , with a thickness of 50nm, the electron transport layer is LiF, with a thickness of 0.8nm, and the cathode is aluminum, with a thickness of 150nm.

[0056] Example 2

[0057] An internal light extraction structure, such as Figure 2 As shown, the metal nanoparticles in the metal nanoparticle layer 2 and the nanofiller particles in the nanofiller layer 3 are doped in the planarization layer 4, the metal nanoparticle layer 2 in the functional layer 5 is cesium with a particle size of 10 nm, the nanofiller layer 3 is titanium dioxide with a particle size of 500 nm, and the planarization layer 4 is a polyvinyl alcohol material.

[0058] The method for preparing the internal light extraction structure of this embodiment is: preparing a polyvinyl alcohol solution doped with 3 wt % cesium and 20 wt % titanium dioxide on a glass substrate by coating.

[0059] This embodiment also provides an organic electroluminescent device, including a glass substrate 1 and a functional layer 5 (i.e., the internal light extraction structure provided in Embodiment 2), an organic electroluminescent device layer and a glass cover. The organic electroluminescent device layer includes: an anode ITO; a hole transport layer NPB with a thickness of 40 nm; a light emitting layer of Alq 3 , with a thickness of 50nm, the electron transport layer is LiF, with a thickness of 0.8nm, and the cathode is aluminum, with a thickness of 150nm.

[0060] Example 3

[0061] An internal light extraction structure, such as Figure 3 As shown, metal nanoparticles are doped in the nanofiller layer 3, the metal nanoparticle layer 2 in the functional layer 5 is cesium with a particle size of 10 nm, the nanofiller layer 3 is titanium dioxide with a particle size of 500 nm, and the planarization layer 4 is a polyvinyl alcohol material.

[0062] The preparation method of the internal light extraction structure of this embodiment is: prepare a titanium dioxide solution doped with 3wt% cesium on a glass substrate by coating, and then prepare a planarization layer with a thickness of 2μm on the titanium dioxide by spin coating.

[0063] This embodiment also provides an organic electroluminescent device, including a glass substrate 1 and a functional layer 5 (i.e., the internal light extraction structure of embodiment 3), an organic electroluminescent device layer and a glass cover. The organic electroluminescent device layer includes: an anode ITO; a hole transport layer NPB with a thickness of 40nm; a light emitting layer of Alq3 , with a thickness of 50nm, the electron transport layer is LiF, with a thickness of 0.8nm, and the cathode is aluminum, with a thickness of 150nm.

[0064] Example 4

[0065] An internal light extraction structure, such as Figure 4 As shown, metal nanoparticles are doped in the nanofiller layer 3, the metal nanoparticle layer 2 in the functional layer 5 is cesium with a particle size of 10 nm, the nanofiller layer 3 is titanium dioxide with a particle size of 500 nm, and the planarization layer 4 is a polyvinyl alcohol material.

[0066] The preparation method of the internal light extraction structure of this embodiment is: prepare a titanium dioxide solution doped with 3wt% cesium on a glass substrate by coating, and then prepare a 2μm thick planarization layer on the titanium dioxide by spin coating. The prepared functional layer 5 is written into polyvinyl alcohol by a field emission electron gun, and then the functional layer is etched flat by reactive ion etching to obtain the internal light extraction structure.

[0067] This embodiment also provides an organic electroluminescent device, including a glass substrate 1 and a functional layer 5 (i.e., the internal light extraction structure of embodiment 4), an organic electroluminescent device layer and a glass cover. The organic electroluminescent device layer includes: an anode ITO; a hole transport layer NPB with a thickness of 40 nm; a light emitting layer of Alq 3 , with a thickness of 50nm, the electron transport layer is LiF, with a thickness of 0.8nm, and the cathode is aluminum, with a thickness of 150nm.

[0068] Comparative Example 1

[0069] In Comparative Example 1, an organic electroluminescent device is provided, such as Figure 7 As shown, the specific structure includes a glass substrate, an OLED light-emitting device layer and a glass cover plate; wherein the organic electroluminescent device layer includes: an anode ITO; a hole transport layer NPB with a thickness of 40nm; and a light-emitting layer of Alq 3 , with a thickness of 50nm, the electron transport layer is LiF, with a thickness of 0.8nm, and the cathode is aluminum, with a thickness of 150nm.

[0070] The structures in the above embodiments and comparative examples were prepared into light-emitting devices and performance tests were performed. The test results are shown in the following table:

[0071]

[0072] It can be seen from the above data that under the same brightness conditions, the luminous efficiency of the light-emitting device provided in the embodiment of the present invention is higher than the efficiency of the device provided in the comparative example, and the service life is significantly higher than the service life of the device provided in the comparative example. Therefore, the internal light extraction structure described in the present invention can effectively improve the efficiency of the device, and can further prevent the invasion of water and oxygen, thereby improving the service life of the device. The efficiency and service life of the light-emitting device in Example 4 are the best, indicating that the preparation method of writing cesium-doped titanium dioxide into polyvinyl alcohol by means of a field emission electron gun can not only effectively fill metal nanoparticles of cesium and nanofiller particles of titanium dioxide into the planarization layer of polyvinyl alcohol, thereby improving the performance of the light-emitting device, but also can effectively prevent metal nanoparticles of cesium and nanofiller particles of titanium dioxide from overflowing the planarization layer after absorbing water, thereby further improving the service life of the device.

[0073] Obviously, the above embodiments are merely examples for clearly explaining the present invention, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. An internal light extraction structure, characterized in that: include: A substrate, a functional layer disposed on the substrate, the functional layer comprising a metal nanoparticle layer, a nanofiller layer and a planarization layer composed of a polymer; the particle size of the metal nanoparticles in the metal nanoparticle layer is 1nm-20nm; the metal nanoparticle layer is made of a ductile metal material; The metal nanoparticles in the metal nanoparticle layer and the nanofiller particles in the nanofiller layer are doped in the planarization layer. In terms of mass fraction, the doping ratio of the metal nanoparticles in the planarization layer is 1%-40%, and the doping ratio of the nanofiller particles in the planarization layer is 10%-60%. The nanofiller layer is composed of at least one of titanium dioxide, zirconium oxide, silicon oxide, and aluminum oxide nanoparticles; The metal nanoparticles are ductile and absorb water and oxygen to form a porous structure when water and oxygen invade, which not only improves the light extraction effect and increases the efficiency of the organic electroluminescent device, but also has a good packaging effect; the presence of the nanofiller layer prevents further diffusion of water and oxygen, so that the internal light extraction structure not only has a high extraction efficiency, but also has a good water-blocking and water-absorbing effect.

2. The internal light extraction structure according to claim 1, characterized in that: The metal nanoparticle layer is composed of at least one of gold, platinum, copper, silver, tungsten, aluminum, cesium, and palladium nanoparticles; and the polymer includes at least one of polyvinyl alcohol, polysiloxane, and polyimide.

3. The internal light extraction structure according to claim 1, characterized in that: The particle size of the nanofiller particles in the nanofiller layer is 50 nm-800 nm; the thickness of the functional layer is 100 nm-10 μm.

4. The internal light extraction structure according to claim 1, characterized in that: The coverage area of ​​the nanofiller layer is larger than that of the metal nanoparticle layer; the coverage area of ​​the planarization layer is larger than that of the nanofiller layer; the refractive index of the planarization layer in the outgoing light band is smaller than the refractive index of the substrate and the refractive index of the nanofiller layer.

5. The internal light extraction structure according to claim 3, characterized in that: The metal nanoparticles are doped in the nanofiller layer, and the doping ratio of the metal nanoparticles in the nanofiller layer is 0.5%-10% by mass fraction.

6. The method for preparing an internal light extraction structure according to any one of claims 1 to 5, characterized in that: The following steps are involved: 1) preparing a metal nanoparticle layer and a nanofiller layer on a substrate; 2) preparing a planarization layer by spin coating, magnetron sputtering or printing; After preparing a planarization layer, the following steps are also included: 1) writing the metal nanoparticle layer and the nanofiller layer into the planarization layer by means of a field emission electron gun, an ion beam or a laser; 2) The planarization layer is etched flat by reactive ion etching or plasma etching.

7. The method for preparing an internal light extraction structure according to claim 6, characterized in that: The metal nanoparticles are mixed with the nanofiller layer by vacuum evaporation or coating; or, the metal nanoparticle layer is prepared on the substrate by vacuum evaporation, coating or electron beam evaporation, and then the nanofiller layer is prepared on the metal nanoparticle layer by vacuum evaporation, coating or sputtering.

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