A quantum dot light-emitting diode and its fabrication method

Abstract

This invention discloses a quantum dot light-emitting diode (LED) and its fabrication method. The quantum dot LED includes an anode, a cathode, a quantum dot light-emitting layer disposed between the anode and the cathode, and an interface modification layer disposed between the anode and the quantum dot light-emitting layer. The interface modification layer includes a photonic crystal structure with periodic defects, and the anode is the light-emitting side. One defect in the photonic crystal structure with periodic defects is equivalent to an optical resonant cavity. Under the combined effect of the photonic crystal's grating diffraction and the optical resonant cavity's beam collimation, total emission of emitted light is avoided, thus improving the light extraction efficiency of the quantum dot LED.

Description

Technical Field

[0001] This invention relates to the field of quantum dot light-emitting diodes, and more particularly to a quantum dot light-emitting diode and its fabrication method. Background Technology

[0002] In quantum dot light-emitting diodes and organic light-emitting diodes, the refractive indices of the functional layers in the display substrate are different. When the incident angle of the light from the light-emitting center at the interface of different functional layers or at the glass-air interface reaches a certain size, total internal reflection will occur. Total internal reflection that occurs inside the device is the main reason that limits the light emission efficiency and external quantum efficiency of the display device.

[0003] In existing research, a light coupling layer or microlens with surface microstructure is usually added to the device, or a specific microstructure is formed directly on a certain functional layer to reduce the probability of total internal reflection of light at the interface. However, these methods still have a lot of room for improvement in light extraction, and the light extraction efficiency of existing quantum dot light-emitting diodes is still low.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a quantum dot light-emitting diode and its preparation method, which aims to solve the problem of low light extraction efficiency of existing quantum dot light-emitting diodes.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a quantum dot light-emitting diode, comprising an anode, a cathode, and a quantum dot light-emitting layer disposed between the anode and the cathode, wherein the diode further comprises an interface modification layer disposed between the anode and the quantum dot light-emitting layer, the interface modification layer comprising a photonic crystal structure having periodic defects, and the anode being the light-emitting side.

[0008] Optionally, the photonic crystal structure includes multiple arranged cylinders and multiple arranged non-cylinder vacancy defects. The arrangement is as follows: every three cylinders are arranged as vertices of an equilateral triangle. In a row containing any side of the equilateral triangle, a non-cylinder vacancy is set as a vacancy defect every X cylinders, where X is 2 to 4. Every Y rows, where Y is 2 to 4, a row of cylinders with the defect is set, where the values ​​of X and Y are equal.

[0009] Optionally, the photonic crystal structure includes multiple arranged cylinders and multiple arranged non-cylinder vacancy defects. The arrangement is as follows: every four cylinders are used as vertices of a regular quadrilateral, with a non-cylinder vacancy defect as the center. In the direction of the diagonal of the regular quadrilateral, a non-cylinder vacancy defect is set as a vacancy defect every X cylinders, where X is 2 to 4. Every Y rows, where Y is 2 to 4, a row of cylinders with the defect is set, and the values ​​of X and Y are equal.

[0010] Optionally, the height of the cylinder is 140-180 nm, and / or the diameter of the cylinder is 100-150 nm.

[0011] Optionally, the distance between the axes of two adjacent cylinders arranged as vertices of an equilateral triangle or as vertices of a regular quadrilateral is 200-300 nm.

[0012] Optionally, the interface modification layer consists of a body layer and a photonic crystal structure disposed on the surface of the body layer, wherein the photonic crystal structure is disposed close to the quantum dot emitting layer; the thickness of the body layer is 0-60 nm.

[0013] Optionally, the material of the interface modification layer is selected from ethoxylated polyethyleneimine, 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirodifluorene, and 4-methylthiophenol.

[0014] Optionally, the quantum dot light-emitting diode further includes:

[0015] A hole functional layer is disposed between the anode and the quantum dot light-emitting layer;

[0016] An electronic functional layer disposed between the cathode and the quantum dot light-emitting layer;

[0017] The interface modification layer is disposed between the anode and the hole functional layer, or the interface modification layer is disposed between the hole functional layer and the quantum dot luminescent layer.

[0018] Optionally, when the interface modification layer is disposed between the anode and the hole functional layer, the material of the interface modification layer is ethoxylated polyethyleneimine; or, when the interface modification layer is disposed between the hole functional layer and the quantum dot light-emitting layer, the material of the interface modification layer is one or more of ethoxylated polyethyleneimine, 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirodifluorene, and 4-methylthiophenol.

[0019] A second aspect of the present invention provides a method for fabricating a quantum dot light-emitting diode, comprising the steps of:

[0020] Provide anode;

[0021] An interface modification layer is prepared on the anode, the interface modification layer comprising a photonic crystal structure with periodic defects;

[0022] A quantum dot light-emitting layer is fabricated on the photonic crystal structure with periodic defects;

[0023] A cathode is fabricated on the quantum dot light-emitting layer.

[0024] Optionally, the photonic crystal structure with periodic defects is prepared by one of the following methods: photolithography, plasma etching, electron beam etching, laser interference etching, and nanoimprint lithography.

[0025] Beneficial Effects: This invention provides a quantum dot light-emitting diode and its fabrication method. In the quantum dot light-emitting diode, an interface modification layer comprising a photonic crystal structure with periodic defects is disposed between the anode and the quantum dot light-emitting layer. One defect in the photonic crystal structure with periodic defects is equivalent to an optical resonant cavity. By utilizing the grating diffraction effect of the photonic crystal and the beam collimation effect of the optical resonant cavity, the directionality of the light emitted from the quantum dot light-emitting layer in the photonic crystal is improved, reducing or avoiding total internal reflection of the emitted light at the interface. By utilizing the strong localization effect of the optical resonant cavity, the light emitted from the quantum dot light-emitting layer is radiated outward more efficiently, thereby improving the light extraction efficiency of the quantum dot light-emitting diode. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of a quantum dot light-emitting diode in an embodiment of the present invention.

[0027] Figure 2 This is a flowchart illustrating the fabrication process of the quantum dot light-emitting diode in an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the arrangement of vacancy defects and cylinders in Embodiment 1 and Embodiment 4 of the present invention.

[0029] Figure 4 This is a schematic diagram of the arrangement of vacancy defects and cylinders in Embodiment 2 of the present invention.

[0030] Figure 5 This is a schematic diagram of the arrangement of vacancy defects and cylinders in Embodiment 3 of the present invention.

[0031] Figure 6 This is a schematic diagram of the arrangement of vacancy defects and cylinders in Embodiment 5 of the present invention.

[0032] Figure 7 This is a schematic diagram of the arrangement of vacancy defects and cylinders in Embodiment 6 of the present invention. Detailed Implementation

[0033] This invention provides a quantum dot light-emitting diode and its fabrication method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0034] This invention provides a quantum dot light-emitting diode. It should be noted that quantum dot light-emitting diodes have various structures; the following mainly focuses on... Figure 1 The quantum dot light-emitting diode shown is introduced below. Figure 1 As shown, the quantum dot light-emitting diode includes, from bottom to top, an anode 1, an interface modification layer, a quantum dot light-emitting layer 4, and a cathode 5. The interface modification layer includes a photonic crystal structure 3 with periodic defects, and the anode 1 is the light-emitting side.

[0035] Because the refractive indices differ between the functional layers in a quantum dot light-emitting diode (QLED), total internal reflection occurs when the incident angle of light emitted from the quantum dot emissive layer at the interface reaches a certain value, leading to a decrease in the light extraction efficiency of the QLED. Therefore, in this embodiment, an interface modification layer comprising a photonic crystal structure with periodic defects is provided between the anode and the quantum dot emissive layer. This interface modification layer can avoid or reduce the occurrence of total internal reflection, allowing the light emitted from the quantum dot emissive layer to radiate outward more efficiently, thereby achieving a higher light extraction efficiency.

[0036] Photonic crystal structures contain periodic defects, and the emission frequency of quantum dots is the resonant frequency corresponding to these defects. At this frequency, the defects can form a resonant cavity structure, or optical resonant cavity, within the photonic crystal structure (or, in other words, a defect in a photonic crystal structure with periodic defects is equivalent to an optical resonant cavity). When light propagates along the photonic crystal towards the emission end, it is coupled into the defects and resonates within them. Finally, it radiates from the resonant cavity to the emission end. Multiple optical resonant cavities formed by multiple periodic defects, together with the waveguide (photonic crystal structure) emission end, form a multi-point light source interference system. Interference is enhanced at the front and destructive at the sides, thus concentrating the radiated energy in the middle direction. In other words, the beam collimation effect of the optical resonant cavity can improve the directionality of the light emitted from the quantum dot emission layer in the photonic crystal, thereby increasing the light extraction rate. In other words, in quantum dot light-emitting diodes, the emitted light has a high probability of total internal reflection at each interface, and the larger the incident angle, the greater the probability of total internal reflection. Therefore, by using the beam collimation effect of the optical resonant cavity to modulate the light to the direction perpendicular to the interface (reducing the incident angle), the occurrence of total internal reflection of the emitted light is weakened or avoided, thereby improving the light extraction efficiency of quantum dot light-emitting diodes.

[0037] In addition, a defective photonic crystal is equivalent to a grating structure. Due to the grating diffraction effect, the outgoing light interferes more strongly in a specific direction, thereby further improving the directionality of the outgoing light and thus improving the light extraction rate.

[0038] Furthermore, when defects exist in the photonic crystal structure, extremely narrow frequency defects will also appear in the photonic bandgap. Light that matches the frequency of the defect state is localized at the defect location. The excited atoms or molecules in the quantum dot emitting layer are strongly coupled with the local light field, thereby greatly enhancing the light radiation. In other words, the strong localization effect of the optical resonator enables the light from the quantum dot emitting layer to radiate outward more efficiently.

[0039] Therefore, by utilizing the grating diffraction effect of photonic crystals and the beam collimation effect of optical resonators, the occurrence of total internal reflection of outgoing light is reduced or avoided. By utilizing the strong localization effect of optical resonators, the light emitted by the quantum dot light-emitting layer is radiated outward more efficiently, thereby improving the light extraction efficiency of quantum dot light-emitting diodes.

[0040] In the photonic crystal structure with periodic defects of this embodiment, the photonic crystal structure may include multiple arranged cylinders and multiple arranged vacancy defects without cylinders. The arrangement can be as follows: three cylinders are arranged as vertices of an equilateral triangle, and the vacancy defects are also arranged in an equilateral triangle array. Alternatively, four cylinders are arranged as vertices of a regular quadrilateral, and the vacancy defects are also arranged in a regular quadrilateral array. Detailed descriptions of these two arrangements of the photonic crystal structure are provided below.

[0041] In one implementation, such as Figure 3 As shown, the photonic crystal structure includes multiple arranged cylinders and multiple arranged non-cylinder vacancy defects. The arrangement is as follows: every three cylinders are arranged as vertices of an equilateral triangle. In a row containing one side of the equilateral triangle, a non-cylinder vacancy defect is set every X cylinders, where X is 2 to 4. Every Y rows, where Y is 2 to 4, a row of cylinders with the defect is set, and the values ​​of X and Y are equal. Figure 3 The corresponding values ​​are X = 2 and Y = 2. Figure 4 The corresponding values ​​are X = 3 and Y = 3. Figure 4 (Corresponding to X being 4, Y being 4).

[0042] In one embodiment, the photonic crystal structure includes multiple arranged cylinders of equal height and diameter and multiple arranged vacancy defects without cylinders. The arrangement is as follows: every three cylinders are arranged as vertices of an equilateral triangle. In a row containing one side of the equilateral triangle, a vacancy defect without cylinders is set every X cylinders, where X is 2 to 4. Every Y rows, where Y is 2 to 4, a row of cylinders with the defect is set, and the values ​​of X and Y are equal. In this embodiment, all cylinders in the photonic crystal structure with periodic defects have equal height and diameter and are arranged in the form of every three cylinders as vertices of an equilateral triangle. The vacancy defects are also arranged in the form of an equilateral triangle array.

[0043] The vacancy defect refers to the location where no cylinder is provided. The vacancy defect is surrounded by the cylinder. As a defect in the photonic crystal structure, the emission frequency of the quantum dot emitting layer is the resonant frequency corresponding to this defect. At this operating frequency, the defect forms a resonant cavity structure, i.e., an optical resonant cavity. Under the influence of the grating diffraction effect of the photonic crystal and the beam collimation effect of the optical resonant cavity, total internal reflection of the emitted light is reduced or avoided, improving the light extraction efficiency of the quantum dot emitting diode. The strong localization effect of the optical resonant cavity allows the light from the quantum dot emitting layer to radiate outward more efficiently, further improving the luminous efficiency of the quantum dot emitting diode. In this embodiment, two, three, or four cylinders are arranged between adjacent vacancy defects. If the vacancy defects are too close, they will affect each other, causing deflection of the emitted light; if the vacancy defects are too far apart, the interference effect of the light will be weakened.

[0044] In one embodiment, the height of the cylinder is 140-180 nm.

[0045] In one embodiment, the diameter of the cylinder is 100-150 nm.

[0046] In one embodiment, the height of the cylinder is 140-180 nm, and the diameter of the cylinder is 100-150 nm.

[0047] In one embodiment, the distance between the axes of two adjacent cylinders arranged as vertices of an equilateral triangle is 200-300 nm.

[0048] In one implementation, reference is made to... Figures 6-7The photonic crystal structure comprises multiple arranged cylinders and multiple arranged non-cylinder vacancy defects. The arrangement is as follows: every four cylinders form the vertices of a regular quadrilateral, with a non-cylinder vacancy defect as the center. Along the diagonal of the quadrilateral, a non-cylinder vacancy defect is placed every X cylinders, where X is 2 to 4. Every Y rows, where Y is 2 to 4, a row of cylinders with the defect is formed, where X and Y are equal. Figure 6 The corresponding values ​​are X = 2 and Y = 2. Figure 7 (Corresponding to X being 3, Y being 3).

[0049] In this embodiment, the photonic crystal structure with periodic defects is arranged with four cylinders as vertices of a regular quadrilateral, and the vacancy defects are also arranged in a regular quadrilateral array. Furthermore, all cylinders have the same height and diameter.

[0050] In one implementation, reference is made to... Figure 1 The interface modification layer consists of a body layer 2 and a photonic crystal structure 3 disposed on the surface of the body layer 2, with the photonic crystal structure 3 positioned close to the quantum dot emitting layer. The thickness of the body layer 2 is 0-60 nm. Further, the thickness of the body layer 2 is 10-50 nm. It should be noted that the material of the body layer is the same as the material of the photonic crystal structure.

[0051] In one embodiment, the material of the interface modification layer is selected from ethoxylated polyethyleneimine, 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirodifluorene, and 4-methylthiophenol.

[0052] Of course, the present invention is not limited to the above embodiments. In one embodiment, the quantum dot light-emitting diode may further include:

[0053] A hole functional layer is disposed between the anode and the quantum dot light-emitting layer;

[0054] An electronic functional layer disposed between the cathode and the quantum dot light-emitting layer;

[0055] The interface modification layer is disposed between the anode and the hole functional layer, or the interface modification layer is disposed between the hole functional layer and the quantum dot luminescent layer.

[0056] In one embodiment, the hole functional layer is at least one of a hole injection layer and a hole transport layer. When the hole functional layer is a stacked hole injection layer and a hole transport layer, the hole injection layer is disposed closer to the anode side, and the hole transport layer is disposed closer to the quantum dot light-emitting layer side.

[0057] In existing technologies, a light coupling layer or microlens with a surface microstructure is usually added to QLEDs, or a specific microstructure is formed directly on a certain functional layer to reduce the probability of total internal reflection at the interface. However, the function of the structures added by these methods is only to improve the light extraction rate, without further optimizing the carrier balance and injection of the light-emitting device itself.

[0058] Therefore, in one embodiment of the present invention, a material capable of improving hole injection or balancing carriers is selected as the material of the interface modification layer. This improves both the light extraction efficiency of the quantum dot light-emitting diode and the hole injection or balancing carriers. The material of the interface modification layer is selected from, but is not limited to, ethoxylated polyethyleneimine (PEIE), 2,2′,7,7′-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9′-spirodifluorene (Spiro-OMe TAD), and 4-methylthiophenol (MTP). The interface modification layer can increase the work function of the anode surface, thereby increasing the hole injection capability; or it can enhance the valence band of the quantum dot while lowering the hole injection barrier; or it can block the entry of electrons on the hole transport side without affecting the hole transport capability, thus further facilitating the balance of electron and hole injection in the quantum dot light-emitting diode.

[0059] When the interface modification layer is placed between the anode and the hole injection layer, the material of the interface modification layer can be ethoxylated polyethyleneimine (PEIE). Using this material for the interface modification layer can improve the work function of the anode surface, increase the hole injection capability, and improve the luminous efficiency of QLED.

[0060] When the interface modification layer is disposed between the hole transport layer and the quantum dot emitting layer, and when the material of the interface modification layer is one or both of ethoxylated polyethyleneimine (PEIE) and 4-methylthiophenol (MTP), the interface modification layer can enhance the valence band of the quantum dot while reducing the injection barrier of holes from the hole transport layer to the quantum dot emitting layer; when the material of the interface modification layer is 2,2′,7,7′-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9′-spirodifluorene (Spiro-OMe TAD), the interface modification layer can block electrons from entering the hole transport layer without affecting the hole transport capability.

[0061] In one embodiment, the material of the hole injection layer is selected from one or more of PEDOT:PSS, PFA, MoO3, WoO3, NiO, CuO, V2O5 and CuS, but is not limited thereto.

[0062] In one embodiment, the material of the hole transport layer is selected from one or more of PVK, Poly-TPD, TFB, Poly-TBP, NPB, TCTA, TAPC, CBP, and PEODT:PSS, but is not limited thereto.

[0063] In one embodiment, the anode material may be selected from one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), etc., but is not limited thereto.

[0064] In one embodiment, the quantum dots in the quantum dot emitting layer may be selected from one or more of CdSe, ZnCdS, CdSeS, ZnCdSeS, CdSe / ZnS, CdSeS / ZnS, CdSe / CdS, CdSe / CdS / ZnS, ZnCdS / ZnS, CdS / ZnS, ZnCdSeS / ZnS, CdZnSe / CdZnS, CdZnSe / ZnSe / ZnCdS, CdZnSe / ZnSe / ZnS, GaAs, GaN, InP, InP / ZnS, CuInS, AgInS, CuInS / ZnS, and AnInS / ZnS, but are not limited thereto.

[0065] In one embodiment, the quantum dot light-emitting diode may further include an electronic functional layer.

[0066] In one embodiment, the electronic functional layer includes an electron transport layer disposed between the quantum dot light-emitting layer and the cathode. The material of the electron transport layer is selected from one or more of ZnO, n-type doped ZnO, PBI, PBD, BCP, Bphen, TAZ, and TmPyPB, but is not limited thereto.

[0067] In one embodiment, the electronic functional layer further includes an electron injection layer disposed between the electron transport layer and the cathode. The material of the electron injection layer may be selected from one or more of Ca, Ba, CsF, LiF, and CsCO3, or other electrolyte-type electron transport layer materials, but is not limited thereto.

[0068] In one embodiment, the quantum dot light-emitting diode may further include a cathode, the material of which is selected from one of Al, Ag, and Au, but is not limited thereto.

[0069] This invention also provides a method for fabricating a quantum dot light-emitting diode, such as... Figure 2 As shown, the steps include:

[0070] S11, providing the anode;

[0071] S12. An interface modification layer is prepared on the anode, the interface modification layer comprising a photonic crystal structure with periodic defects;

[0072] S13. A quantum dot light-emitting layer is prepared on the photonic crystal structure with periodic defects;

[0073] S14. A cathode is fabricated on the quantum dot light-emitting layer.

[0074] In step S12, in one embodiment, the interface modification layer consists of a body layer and the photonic crystal structure disposed on the surface of the body layer, wherein the body layer is disposed close to the anode side.

[0075] In one embodiment, the step of preparing the interface modification layer on the anode specifically includes:

[0076] The original bulk layer is prepared on the anode;

[0077] The surface of the original body layer away from the anode is processed to obtain an interface modification layer with a photonic crystal structure having periodic defects on the upper layer and the body layer on the lower layer.

[0078] In this embodiment, a raw body layer is prepared on the anode, and then a photonic crystal structure with periodic defects is processed from the raw body layer using one of the following methods: photolithography, plasma etching, electron beam etching, laser interference etching, nanoimprinting, etc. The portion of the raw body layer that does not have a photonic crystal structure with periodic defects is the body layer.

[0079] The present invention will be described in detail below through embodiments.

[0080] Example 1

[0081] The ITO substrate was ultrasonically cleaned for 15 minutes each with deionized water, acetone, and anhydrous ethanol. The cleaned ITO substrate was then subjected to ultraviolet-ozone treatment for 15 minutes to further clean the substrate and improve its surface activity and work function. Using the cleaned ITO substrate as the anode, a 20 nm thick layer of PEDOT:PSS was spin-coated onto it as a hole injection layer. After spin-coating, the substrate was placed in air and annealed at 150°C for 15 minutes, followed by cooling.

[0082] An ITO substrate containing a PEDOT:PSS hole injection layer was placed in a glove box under a nitrogen atmosphere. A layer of TFB with a thickness of 30 nm was spin-coated on the PEDOT:PSS hole injection layer as a hole transport layer. After spin-coating, the substrate was placed on a heating stage and annealed at 150°C for 30 min before cooling.

[0083] A layer of PEIE with an initial thickness of 180 nm was spin-coated onto the TFB hole transport layer as an interface modification layer. The PEIE layer was then imprinted into a cylindrical array structure with vacancy defects using nanoimprint lithography. After forming, the structure was placed on a heating stage, annealed at 100°C for 15 min, and then cooled to allow the solvent to fully evaporate and solidify. The specific arrangement of the vacancy defects and cylinders is as follows: Figure 3 As shown in the diagram (solid circles represent cylinders, hollow circles represent vacancy defects), each cylinder is 140 nm long and has a cross-sectional diameter of 100 nm. The distance between the axes of two adjacent cylinders is 200 nm. Every two rows of cylinders form a row with vacancy defects. Within each row with vacancy defects, one vacancy defect is placed every two cylinders. Each vacancy defect is surrounded by six cylinders: two from the previous row, two from the next row, and two from the left and right sides of the same row. The six cylinders form a regular hexagon, with the vacancy defect located at the center of the hexagon. The distance between the centers of two vacancy defects is 600 nm.

[0084] A CdZnSe / ZnSe / ZnCdS quantum dot luminescent layer with a thickness of 40 nm was spin-coated onto the PEIE layer. After spin-coating, the layer was placed on a heating stage and annealed at 80 °C for 10 min.

[0085] A 40 nm thick layer of ZnO was spin-coated onto a CdZnSe / ZnSe / ZnCdS quantum dot luminescent layer as an electron transport layer. After spin-coating, the layer was placed on a heating stage and annealed at 80 °C for 15 min.

[0086] A 100nm thick Ag electrode is vacuum thermally deposited on a ZnO electron transport layer to form a QLED device.

[0087] Example 2

[0088] The ITO substrate was ultrasonically cleaned for 15 minutes each with deionized water, acetone, and anhydrous ethanol. The cleaned ITO substrate was then subjected to ultraviolet-ozone treatment for 15 minutes to further clean the substrate and improve its surface activity and work function.

[0089] Using the cleaned ITO substrate as the anode, a layer of PEDOT:PSS with a thickness of 30nm was spin-coated onto the ITO substrate as a hole injection layer. After spin-coating, the substrate was placed in an air atmosphere, annealed at 150°C for 15 minutes, and then cooled.

[0090] An ITO substrate containing a PEDOT:PSS hole injection layer was placed in a glove box under a nitrogen atmosphere. A layer of TFB was spin-coated on the PEDOT:PSS hole injection layer as a hole transport layer with a thickness of 40 nm. After spin-coating, the substrate was placed on a heating stage and annealed at 150°C for 30 min before cooling.

[0091] A Spiro-OMe TAD layer with an initial thickness of 190 nm was spin-coated onto the TFB hole transport layer as an interface modification layer. The Spiro-OMe TAD layer was then imprinted into a cylindrical array structure with vacancy defects using nanoimprint lithography. After forming, the structure was placed on a heating stage, annealed at 100°C for 15 min, and then cooled to allow the solvent to fully evaporate and solidify. The specific arrangement of the vacancy defects and cylinders is as follows: Figure 4 As shown in the diagram (solid circles represent cylinders, hollow circles represent vacancy defects), each cylinder is 160 nm long and has a cross-sectional diameter of 125 nm. The distance between the axes of two adjacent cylinders is 250 nm. Every three rows of cylinders form a row containing vacancy defects. Within each row containing vacancy defects, one vacancy defect is placed every three cylinders. Each vacancy defect is surrounded by six cylinders: two from the previous row, two from the next row, and two from the left and right sides of the same row as the vacancy defect. The six cylinders form a regular hexagon, with the vacancy defect located at the center of the hexagon. The distance between the centers of two vacancy defects is 1000 nm.

[0092] A CdZnSe / ZnSe / ZnCdS quantum dot luminescent layer with a thickness of 40 nm was spin-coated onto the Spiro-OMe TAD layer. After spin-coating, the layer was placed on a heating stage and annealed at 80 °C for 10 min.

[0093] A 40 nm thick layer of ZnO was spin-coated onto a CdZnSe / ZnSe / ZnCdS quantum dot luminescent layer as an electron transport layer. After spin-coating, the layer was placed on a heating stage and annealed at 80 °C for 15 min.

[0094] A 100nm thick Ag electrode is vacuum thermally deposited on a ZnO electron transport layer to form a QLED device.

[0095] Example 3

[0096] The ITO substrate was ultrasonically cleaned for 15 minutes each with deionized water, acetone, and anhydrous ethanol. The cleaned ITO substrate was then subjected to ultraviolet-ozone treatment for 15 minutes to further clean the substrate and improve its surface activity and work function.

[0097] Using the cleaned ITO substrate as the anode, a layer of PEDOT:PSS with a thickness of 40nm was spin-coated onto the ITO substrate as a hole injection layer. After spin-coating, the substrate was placed in an air atmosphere, annealed at 150°C for 15 minutes, and then cooled.

[0098] An ITO substrate containing a PEDOT:PSS hole injection layer was placed in a glove box under a nitrogen atmosphere. A layer of TFB with a thickness of 50 nm was spin-coated on the PEDOT:PSS hole injection layer as a hole transport layer. After spin-coating, the substrate was placed on a heating stage and annealed at 150°C for 30 min before cooling.

[0099] A layer of MTP with an initial thickness of 200 nm was spin-coated onto the TFB hole transport layer as an interface modification layer. The MTP layer was then imprinted into a cylindrical array structure with vacancy defects using nanoimprint lithography. After forming, the structure was placed on a heating stage, annealed at 100°C for 15 min, and then cooled to allow the solvent to fully evaporate and solidify. The specific arrangement of the vacancy defects and cylinders is as follows: Figure 5 As shown in the diagram (solid circles represent cylinders, hollow circles represent vacancy defects), each cylinder is 180 nm long and has a cross-sectional diameter of 150 nm. The distance between the axes of two adjacent cylinders is 300 nm. Every four rows of cylinders, a row containing vacancy defects is placed. Within each row containing vacancy defects, a vacancy defect is placed every four cylinders. Each vacancy defect is surrounded by six cylinders: two from the previous row, two from the next row, and two from the left and right sides of the same row as the vacancy defect. The six cylinders form a regular hexagon, with the vacancy defect located at the center of the hexagon. The distance between the centers of two vacancy defects is 1500 nm.

[0100] A CdZnSe / ZnSe / ZnCdS quantum dot luminescent layer with a thickness of 40 nm was spin-coated onto the MTP layer. After spin-coating, the layer was placed on a heating stage and annealed at 80 °C for 10 min.

[0101] A 40 nm thick layer of ZnO was spin-coated onto a CdZnSe / ZnSe / ZnCdS quantum dot luminescent layer as an electron transport layer. After spin-coating, the layer was placed on a heating stage and annealed at 80 °C for 15 min.

[0102] A 100nm thick Ag electrode is vacuum thermally deposited on a ZnO electron transport layer to form a QLED device.

[0103] Example 4

[0104] The ITO substrate was ultrasonically cleaned for 15 minutes each with deionized water, acetone, and anhydrous ethanol. The cleaned ITO substrate was then subjected to ultraviolet-ozone treatment for 15 minutes to further clean the substrate and improve its surface activity and work function.

[0105] Using an ITO substrate as the anode, a PEIE layer with an initial thickness of 200 nm was spin-coated onto the ITO substrate as an interface modification layer. The PEIE layer was then imprinted into a cylindrical array structure with vacancy defects using nanoimprint lithography. After forming, the structure was placed on a heating stage, annealed at 100°C for 15 min, and then cooled to allow the solvent to fully evaporate and solidify. The specific arrangement of the vacancy defects and cylinders is shown in Figure 3. Each cylinder has a length of 140 nm and a cross-sectional diameter of 100 nm. The center-to-center distance between two adjacent cylinders is 200 nm. Every two rows of cylinders form a row with vacancy defects. Within each row with vacancy defects, one vacancy defect is placed every two cylinders. Each vacancy defect is surrounded by six cylinders: two from the previous row, two from the next row, and two from the left and right sides of the same row as the vacancy defect. Six cylinders form a regular hexagon, with the vacancy defect located at the center of the hexagon (i.e., the distance between the center of each of the six cylinders and the center of the vacancy defect is 200 nm). The distance between the centers of two vacancy defects is 600 nm.

[0106] A 20 nm thick PEDOT:PSS layer was spin-coated onto the PEIE layer as a hole injection layer. After spin-coating, the layer was placed in an air atmosphere, annealed at 150 °C for 15 min, and then cooled.

[0107] An ITO substrate containing a PEIE layer and a PEDOT:PSS hole injection layer was placed in a glove box under a nitrogen atmosphere. A TFB layer with a thickness of 30 nm was spin-coated on the PEDOT:PSS hole injection layer as a hole transport layer. After spin-coating, the substrate was placed on a heating stage and annealed at 150°C for 30 min before cooling.

[0108] A CdZnSe / ZnSe / ZnCdS quantum dot luminescent layer with a thickness of 40 nm was spin-coated onto the TFB hole transport layer. After spin-coating, the layer was placed on a heating stage and annealed at 80 °C for 10 min.

[0109] A 40 nm thick layer of ZnO was spin-coated onto a CdZnSe / ZnSe / ZnCdS quantum dot luminescent layer as an electron transport layer. After spin-coating, the layer was placed on a heating stage and annealed at 80 °C for 15 min.

[0110] A 100nm thick Ag electrode is vacuum thermally deposited on a ZnO electron transport layer to form a QLED device.

[0111] Example 5

[0112] The ITO substrate was ultrasonically cleaned for 15 minutes each with deionized water, acetone, and anhydrous ethanol. The cleaned ITO substrate was then subjected to ultraviolet-ozone treatment for 15 minutes to further clean the substrate and improve its surface activity and work function. Using the cleaned ITO substrate as the anode, a 20 nm thick layer of PEDOT:PSS was spin-coated onto it as a hole injection layer. After spin-coating, the substrate was placed in air and annealed at 150°C for 15 minutes, followed by cooling.

[0113] An ITO substrate containing a PEDOT:PSS hole injection layer was placed in a glove box under a nitrogen atmosphere. A layer of TFB with a thickness of 30 nm was spin-coated on the PEDOT:PSS hole injection layer as a hole transport layer. After spin-coating, the substrate was placed on a heating stage and annealed at 150°C for 30 min before cooling.

[0114] A layer of PEIE with an initial thickness of 180 nm was spin-coated onto the TFB hole transport layer as an interface modification layer. The PEIE layer was then imprinted into a cylindrical array structure with vacancy defects using nanoimprint lithography. After forming, the structure was placed on a heating stage, annealed at 100°C for 15 min, and then cooled to allow the solvent to fully evaporate and solidify. The specific arrangement of the vacancy defects and cylinders is as follows: Figure 6 As shown in the diagram (solid circles represent cylinders, hollow circles represent vacancy defects), each cylinder is 140 nm long and has a cross-sectional diameter of 100 nm. The distance between the axes of two adjacent cylinders is 200 nm. Every two rows of cylinders form a row with vacancy defects. Within each row with vacancy defects, a vacancy defect is placed every two cylinders. Each vacancy defect is surrounded by four cylinders: one from the previous row, one from the next row, and one from the left or right of the cylinder in the same row. The four cylinders form a regular quadrilateral, with the vacancy defect located at the center of the quadrilateral. The distance between the centers of two vacancy defects is 600 nm.

[0115] A CdZnSe / ZnSe / ZnCdS quantum dot luminescent layer with a thickness of 40 nm was spin-coated onto the PEIE layer. After spin-coating, the layer was placed on a heating stage and annealed at 80 °C for 10 min.

[0116] A 40 nm thick layer of ZnO was spin-coated onto a CdZnSe / ZnSe / ZnCdS quantum dot luminescent layer as an electron transport layer. After spin-coating, the layer was placed on a heating stage and annealed at 80 °C for 15 min.

[0117] A 100nm thick Ag electrode is vacuum thermally deposited on a ZnO electron transport layer to form a QLED device.

[0118] Example 6

[0119] The ITO substrate was ultrasonically cleaned for 15 minutes each with deionized water, acetone, and anhydrous ethanol. The cleaned ITO substrate was then subjected to ultraviolet-ozone treatment for 15 minutes to further clean the substrate and improve its surface activity and work function.

[0120] Using the cleaned ITO substrate as the anode, a layer of PEDOT:PSS with a thickness of 30nm was spin-coated onto the ITO substrate as a hole injection layer. After spin-coating, the substrate was placed in an air atmosphere, annealed at 150°C for 15 minutes, and then cooled.

[0121] An ITO substrate containing a PEDOT:PSS hole injection layer was placed in a glove box under a nitrogen atmosphere. A layer of TFB was spin-coated on the PEDOT:PSS hole injection layer as a hole transport layer with a thickness of 40 nm. After spin-coating, the substrate was placed on a heating stage and annealed at 150°C for 30 min before cooling.

[0122] A Spiro-OMe TAD layer with an initial thickness of 190 nm was spin-coated onto the TFB hole transport layer as an interface modification layer. The Spiro-OMe TAD layer was then imprinted into a cylindrical array structure with vacancy defects using nanoimprint lithography. After forming, the structure was placed on a heating stage, annealed at 100°C for 15 min, and then cooled to allow the solvent to fully evaporate and solidify. The specific arrangement of the vacancy defects and cylinders is as follows: Figure 7 As shown in the diagram (solid circles represent cylinders, hollow circles represent vacancy defects), each cylinder is 160 nm long and has a cross-sectional diameter of 125 nm. The distance between the axes of two adjacent cylinders is 250 nm. Every three rows of cylinders form a row containing vacancy defects. Within each row containing vacancy defects, one vacancy defect is placed every three cylinders. Each vacancy defect is surrounded by four cylinders: one from the previous row, one from the next row, and one from the left or right of the cylinder in the same row. The four cylinders form a regular quadrilateral, with the vacancy defect located at the center of the quadrilateral. The distance between the centers of two vacancy defects is 1000 nm.

[0123] A CdZnSe / ZnSe / ZnCdS quantum dot luminescent layer with a thickness of 40 nm was spin-coated onto the Spiro-OMe TAD layer. After spin-coating, the layer was placed on a heating stage and annealed at 80 °C for 10 min.

[0124] A 40 nm thick layer of ZnO was spin-coated onto a CdZnSe / ZnSe / ZnCdS quantum dot luminescent layer as an electron transport layer. After spin-coating, the layer was placed on a heating stage and annealed at 80 °C for 15 min.

[0125] A 100nm thick Ag electrode is vacuum thermally deposited on a ZnO electron transport layer to form a QLED device.

[0126] In summary, this invention provides a quantum dot light-emitting diode and its fabrication method. In the quantum dot light-emitting diode provided by this invention, an interface modification layer with a photonic crystal structure having periodic defects is further disposed between the anode and the quantum dot light-emitting layer. The photonic crystal structure with periodic defects faces the quantum dot light-emitting layer. One defect in the photonic crystal structure with periodic defects is equivalent to an optical resonant cavity. Utilizing the grating diffraction effect of the photonic crystal and the beam collimation effect of the optical resonant cavity, the directionality of light emitted from the quantum dot light-emitting layer in the photonic crystal is improved, avoiding or reducing total internal reflection of the emitted light at the interface. Simultaneously, the strong localization effect of the optical resonant cavity allows the light emitted from the quantum dot light-emitting layer to radiate outward more efficiently, thereby improving the light extraction efficiency of the quantum dot light-emitting diode. Furthermore, when the interface modification layer is disposed between the anode and the hole injection layer, it can increase the work function of the anode surface, thereby increasing the hole injection capability and balancing electron-hole injection. When the interface modification layer is disposed between the hole transport layer and the quantum dot emitting layer, it can enhance the valence band of the quantum dot, reducing the injection barrier between the hole transport layer and the quantum dot emitting layer, or it can block electrons from entering the hole transport layer without affecting the hole transport capability, thus balancing electron-hole injection. Therefore, the interface modification layer of this invention not only improves the light extraction efficiency of QLEDs but also facilitates the balance of electron-hole injection in QLEDs, thereby improving the luminous efficiency and photoelectric performance of QLEDs.

[0127] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A quantum dot light-emitting diode, comprising an anode, a cathode, and a quantum dot light-emitting layer disposed between the anode and the cathode, characterized in that, It also includes an interface modification layer disposed between the anode and the quantum dot light-emitting layer, the interface modification layer comprising a photonic crystal structure with periodic defects, the anode being the light-emitting side; The photonic crystal structure includes multiple arranged cylinders and multiple arranged non-cylinder vacancy defects. The arrangement is as follows: every three cylinders are arranged as vertices of an equilateral triangle. In a row containing one side of the equilateral triangle, a non-cylinder vacancy is set as a vacancy defect every X cylinders, where X is 2 to 4. Every Y rows, where Y is 2 to 4, a row of cylinders with the defect is set, and the values ​​of X and Y are equal. Alternatively, the photonic crystal structure comprises multiple arranged cylinders and multiple arranged non-cylinder vacancy defects, arranged as follows: every four cylinders serve as vertices of a regular quadrilateral, with a non-cylinder vacancy defect as the center. In the direction of the diagonal of the regular quadrilateral, a non-cylinder vacancy defect is set as a vacancy defect every X cylinders, where X is 2 to 4. Every Y rows, where Y is 2 to 4, a row of cylinders with the defect is set, and the values ​​of X and Y are equal.

2. The quantum dot light-emitting diode according to any one of claims 1, characterized in that, The height of the cylinder is 140-180 nm; and / or the diameter of the cylinder is 100-150 nm. And / or, the distance between the axes of two adjacent cylinders in the cylinders arranged as equilateral triangle vertices or as regular quadrilateral vertices is 200-300 nm.

3. The quantum dot light-emitting diode according to claim 1, characterized in that, The interface modification layer consists of a body layer and a photonic crystal structure disposed on the surface of the body layer, wherein the photonic crystal structure is disposed close to the quantum dot emitting layer; the thickness of the body layer is 0-60 nm.

4. The quantum dot light-emitting diode according to claim 1, characterized in that, The material of the interface modification layer is selected from one of ethoxylated polyethyleneimine, 2,2′,7,7′-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9′-spirodifluorene, and 4-methylthiophenol.

5. The quantum dot light-emitting diode according to claim 1, characterized in that, The quantum dot light-emitting diode also includes: A hole functional layer is disposed between the anode and the quantum dot light-emitting layer; An electronic functional layer disposed between the cathode and the quantum dot light-emitting layer; The interface modification layer is disposed between the anode and the hole functional layer, or the interface modification layer is disposed between the hole functional layer and the quantum dot luminescent layer.

6. The quantum dot light-emitting diode according to claim 5, characterized in that, When the interface modification layer is disposed between the anode and the hole functional layer, the material of the interface modification layer is ethoxylated polyethyleneimine; or, when the interface modification layer is disposed between the hole functional layer and the quantum dot light-emitting layer, the material of the interface modification layer is one or more of ethoxylated polyethyleneimine, 2,2′,7,7′-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9′-spirodifluorene, and 4-methylthiophenol.

7. A method for fabricating a quantum dot light-emitting diode, characterized in that, Including the following steps: Provide anode; An interface modification layer is prepared on the anode, the interface modification layer comprising a photonic crystal structure with periodic defects; A quantum dot light-emitting layer is fabricated on the photonic crystal structure with periodic defects; A cathode is fabricated on the quantum dot light-emitting layer; The anode is the light-emitting side; The photonic crystal structure includes multiple arranged cylinders and multiple arranged non-cylinder vacancy defects. The arrangement is as follows: every three cylinders are arranged as vertices of an equilateral triangle. In a row containing one side of the equilateral triangle, a non-cylinder vacancy is set as a vacancy defect every X cylinders, where X is 2 to 4. Every Y rows, where Y is 2 to 4, a row of cylinders with the defect is set, and the values ​​of X and Y are equal. Alternatively, the photonic crystal structure comprises multiple arranged cylinders and multiple arranged non-cylinder vacancy defects, arranged as follows: every four cylinders serve as vertices of a regular quadrilateral, with a non-cylinder vacancy defect as the center. In the direction of the diagonal of the regular quadrilateral, a non-cylinder vacancy defect is set as a vacancy defect every X cylinders, where X is 2 to 4. Every Y rows, where Y is 2 to 4, a row of cylinders with the defect is set, and the values ​​of X and Y are equal.

8. The preparation method according to claim 7, characterized in that, The photonic crystal structure with periodic defects is prepared by one of the following methods: photolithography, plasma etching, electron beam etching, laser interference etching, or nanoimprint lithography.

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