Method for improving external quantum efficiency of blue light QLED

Abstract

The invention relates to the technical field of material science efficiency improvement, and particularly discloses a method for improving the external quantum efficiency of a blue light QLED, which comprises a gradient hole injection structure and a PEDOT-PSSQLED-free structure, and is characterized in that the gradient hole injection structure is arranged between a typical hole transport layer and a blue quantum dot emission layer, and the PEDOT-PSSQLED-free structure is arranged between the typical hole transport layer and the blue quantum dot emission layer; multiple layers of gradient holes with gradient energy level distribution are introduced for material injection; the core layer of the gradient hole injection material is Poly-TPD, and the energy level of the highest occupied molecular orbital of the Poly-TPD is finely customized through micromolecule tri-TCTA; the initial layer of the gradient hole injection structure is a composite layer formed by PEDOT-PSS or TFB and Poly-TPD; according to the invention, the gradient hole transport material of a multi-component mixed system is adopted, and the proportion and the type of each component are adjusted, so that the composite material with continuous gradient energy level distribution is formed, the material can better match the energy level difference between different layers, efficient transport and injection of hole energy are realized, and the performance of the blue light QLED is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of improving material efficiency, and specifically relates to a method for improving the external quantum efficiency of a blue light QLED. Background Art

[0002] Blue light QLED (quantum dot light-emitting diode) is a type of QLED technology that focuses on emitting blue light. Blue light QLED is based on quantum dot technology. Its light-emitting principle is to stimulate red and green light by irradiating quantum dots with blue LED light sources (Note: The description here may be simplified because blue light QLED mainly focuses on the emission of blue light, but quantum dot technology may also involve the emission and conversion of light of other colors). In fact, the quantum dots in blue light QLED can emit pure blue light after being excited by blue light. In addition, the emission wavelength can be controlled by adjusting the size and composition of quantum dots, but in this discussion, we mainly focus on blue light emission.

[0003] Blue light QLED can emit pure blue light, which can achieve wider color gamut coverage when combined with other colors of light; due to the efficient luminescence characteristics of quantum dots, blue light QLED usually has higher brightness performance and also has advantages in energy efficiency; compared with self-luminous technologies such as OLED, QLED technology usually has a longer service life because quantum dot luminescent materials are relatively stable and not prone to aging; blue light QLED is easier to manufacture in large sizes, which is of great significance for large-screen display applications.

[0004] The reasons for improving the efficiency of blue light QLED are as follows: the improvement of blue light QLED efficiency can enable the display to achieve a wider color gamut coverage while maintaining a high brightness, which is crucial for users who pursue a high-quality visual experience and can bring more realistic and rich color performance; in display technology, contrast is an important indicator to measure image clarity and detail performance. The improvement of blue light QLED efficiency helps to enhance the contrast of the image, making the dark details clearer and the bright parts fuller; the improvement of blue light QLED efficiency means that less power is required when emitting light of the same brightness, which helps to reduce the energy consumption of display devices and extend battery life. This is particularly important for mobile devices; with the world's emphasis on environmental protection and sustainable development, improving the energy efficiency of display devices has become an industry consensus. The improvement in the efficiency of blue light QLED helps reduce energy consumption and carbon emissions, which is in line with the development trend of environmental protection and energy conservation; blue light QLED will generate a certain amount of heat in the process of light emission. The improvement in efficiency means that when emitting light of the same brightness, less heat is generated, which helps to reduce the impact of thermal effects on device performance and extend service life; the improvement in blue light QLED efficiency is usually accompanied by an improvement in stability. Stable device performance means less failure rate and longer service life, which is crucial to the reliability and durability of display equipment.

[0005] With the rapid development of display technology, quantum dot light-emitting diodes (QLEDs) have shown great application potential in the fields of display and lighting due to their advantages such as high brightness, high color purity and wide viewing angle. Especially in blue light QLEDs, the improvement of their performance is crucial to achieving full-color display and improving display quality. However, traditional blue light QLED devices still face many challenges in external quantum efficiency (EQE) and stability.

[0006] Traditional blue QLED devices usually use PEDOT-PSS as the hole injection layer (HIL), but PEDOT-PSS has problems such as high hygroscopicity, strong acidity and easy interface instability, which seriously affects the long-term stability and reliability of the device. In addition, the energy level matching between the traditional hole transport layer and the blue quantum dot emission layer is poor, resulting in low hole injection efficiency, further limiting the improvement of the EQE of blue QLED. Among them, the gradient hole injection structure has attracted much attention because it can gradually reduce the hole energy and achieve efficient injection. However, the existing gradient hole injection structure still has shortcomings in material selection, energy level matching and interface regulation, which limits its further performance improvement. Therefore, a method for improving the external quantum efficiency of blue QLED is proposed.

[0007] The present invention adopts a gradient hole transport material of a multi-component mixed system, and by adjusting the proportion and type of each component, a composite material with a continuous gradient energy level distribution is formed. This material can better match the energy level differences between different layers, achieve efficient transmission and injection of hole energy, and further improve the performance of blue light QLED.

[0008] The present invention significantly improves the external quantum efficiency (EQE) of blue light QLED by introducing a gradient hole injection structure and a PEDOT-PSS-free QLED structure, while enhancing the stability and long-term working reliability of the device. These innovative technical features jointly promote a significant improvement in the performance of blue light QLED and provide strong support for the application of QLED technology in fields such as displays and solid-state lighting. Summary of the invention

[0009] The purpose of the present invention is to provide a method for improving the external quantum efficiency of blue light QLED, so as to solve the problem that the gradient hole injection structure still has deficiencies in material selection, energy level matching and interface regulation, which limits the further improvement of its performance.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] A method for improving the external quantum efficiency of a blue light QLED, comprising:

[0012] A gradient hole injection structure and a PEDOT-PSSQLED-free structure, wherein the gradient hole injection structure is formed by introducing multiple layers of gradient holes with gradient energy level distribution between a typical hole transport layer and a blue quantum dot emission layer to inject materials, so as to achieve a gradual reduction in hole energy and efficient injection;

[0013] The core layer of the gradient hole injection material is Poly-TPD, and the energy level of the highest occupied molecular orbital of the Poly-TPD is finely customized by the small molecule tri-TCTA to accurately match the energy level of the blue emission layer, thereby greatly reducing the energy barrier of hole injection;

[0014] The starting layer of the gradient hole injection structure is a composite layer formed by PEDOT-PSS or TFB and Poly-TPD, so as to further optimize the hole injection efficiency and device performance.

[0015] Preferably, the gradient hole injection structure further includes at least one energy transition layer, and the energy transition layer has an energy level between the starting layer and the core layer to achieve a smooth transition of hole energy, further reduce invalid exciton recombination, and significantly improve the EQE of the blue light QLED.

[0016] Through the setting of the above-mentioned technical scheme, by introducing a gradient hole injection structure, the gradual reduction of hole energy and efficient injection are achieved, especially by finely customizing the highest occupied molecular orbital energy level of Poly-TPD and introducing an energy transition layer, the invalid exciton recombination is further reduced, and the EQE of the blue light QLED is significantly improved. Experimental results show that the EQE improvement efficiency of the blue light QLED device of the present invention can reach more than 20%.

[0017] Preferably, the PEDOT-PSSQLED-free structure comprises the following steps:

[0018] Step 1: Use PTAA as the hole injection layer and form a binary PTAA-F4-TCNQ HIL structure by doping F4-TCNQ, so that the structure not only has excellent hole injection ability, but also can effectively suppress the stability problem caused by PEDOT-PSS;

[0019] Step 2: depositing one or more layers of gradient hole transport materials with specific energy levels and thicknesses on the binary PTAA-F4-TCNQHIL structure to further optimize the hole transport path and injection efficiency;

[0020] Step 3: Deposit a blue QD emission layer, an electron transport layer and a metal electrode in sequence on the gradient hole transport material to form a complete QLED device structure, which significantly improves the stability and long-term working reliability of the device while ensuring efficient luminescence performance.

[0021] Preferably, the gradient hole transport material includes Poly-TPD, small molecule tri-TCTA or a material with energy levels and hole transport properties to achieve a gradual reduction in hole energy and efficient injection.

[0022] By setting the above technical solution, a PEDOT-PSS-free QLED structure is adopted, which effectively avoids the stability problem caused by PEDOT-PSS. At the same time, by optimizing the ratio and type of the hole injection layer and the gradient hole transport material, the stability and long-term working reliability of the device are further improved, which makes the blue light QLED device of the present invention have a longer service life and better performance in practical applications;

[0023] In the PEDOT-free PSD SQLED structure, the present invention adopts intelligent adaptive doping technology to dynamically adjust the concentration and type of dopants according to the working state of the device and changes in the external environment. At the same time, a nanoscale smooth transition interface is formed between the layers of the gradient hole injection structure, which further reduces the energy loss and charge load at the interface and improves the hole injection efficiency. These innovative technical features have jointly promoted a significant improvement in the performance of blue light QLED.

[0024] Preferably, the EQE improvement efficiency of the blue light QLED is 20%, and the device exhibits excellent stability and reliability under long-term working conditions, meeting the demand for high-performance blue light QLED devices in practical applications.

[0025] Preferably, the gradient hole injection efficiency improvement model formula is:

[0026]

[0027] in, is the hole injection efficiency under the gradient hole injection structure, is the hole injection efficiency in the gradient-free structure, ΔE barrier is the energy barrier reduced by the gradient structure, and k is the proportional coefficient between the energy barrier reduction and the injection efficiency improvement, which is obtained by fitting the experimental data.

[0028] Preferably, the external quantum efficiency improvement formula of the blue light QLED is:

[0029]

[0030] Among them, EQE base is the external quantum efficiency of the gradient-free structure, η exc is the exciton recombination efficiency.

[0031] Preferably, the gradient hole injection material adopts a multi-component mixed system, and by adjusting the proportion and type of each component, a composite material with a continuous gradient energy level distribution is formed to better match the energy level difference between different layers and achieve efficient transmission and injection of hole energy.

[0032] Preferably, in the PEDOT-free PSSQLED structure, an intelligent adaptive doping technology is used, and the concentration and type of dopants are dynamically adjusted according to the working state of the device and changes in the external environment to optimize the electrical properties and stability of the hole injection layer.

[0033] Preferably, between the layers of the gradient hole injection structure, a nanoscale smooth transition interface is formed by precisely controlling the deposition conditions and material ratios, thereby further reducing the energy loss and charge load at the interface and improving the hole injection efficiency.

[0034] Through the setting of the above-mentioned technical scheme, the present invention adopts a gradient hole transport material of a multi-component mixed system, and by adjusting the proportion and type of each component, a composite material with a continuous gradient energy level distribution is formed. This material can better match the energy level differences between different layers, realize efficient transmission and injection of hole energy, and further improve the performance of blue light QLED.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] By introducing a gradient hole injection structure, the gradual reduction of hole energy and efficient injection are achieved. In particular, by finely tailoring the highest occupied molecular orbital energy level of Poly-TPD and introducing an energy transition layer, invalid exciton recombination is further reduced, and the EQE of the blue light QLED is significantly improved. Experimental results show that the EQE of the blue light QLED device of the present invention can be improved by more than 20%;

[0037] The use of a PEDOT-PSS-free QLED structure effectively avoids the stability problem caused by PEDOT-PSS. At the same time, by optimizing the ratio and type of the hole injection layer and the gradient hole transport material, the stability and long-term working reliability of the device are further improved, which makes the blue light QLED device of the present invention have a longer service life and better performance in practical applications.

[0038] The present invention adopts a gradient hole transport material of a multi-component mixed system, and forms a composite material with a continuous gradient energy level distribution by adjusting the proportion and type of each component. This material can better match the energy level difference between different layers, realize efficient transmission and injection of hole energy, and further improve the performance of blue light QLED;

[0039] In the PEDOT-PSS-free QLED structure, the present invention adopts an intelligent adaptive doping technology to dynamically adjust the concentration and type of dopants according to the working state of the device and changes in the external environment. At the same time, a nanoscale smooth transition interface is formed between the layers of the gradient hole injection structure, further reducing the energy loss and charge load at the interface and improving the hole injection efficiency. These innovative technical features jointly promote a significant improvement in the performance of blue QLEDs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a flowchart of the steps of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0042] As Figure 1 shown, a method for improving the external quantum efficiency of blue QLEDs includes: a gradient hole injection structure and a PEDOT-PSS-free QLED structure. The gradient hole injection structure injects materials with gradient energy levels between the typical hole transport layer and the blue quantum dot emission layer to achieve a gradual reduction in hole energy and efficient injection.

[0043] The core layer of the gradient hole injection material is Poly-TPD, and the energy level of the highest occupied molecular orbital of Poly-TPD is finely customized by the small molecule tri-TCTA to precisely match the energy level of the blue emission layer, thereby greatly reducing the energy barrier for hole injection.

[0044] The starting layer of the gradient hole injection structure is a composite layer formed by PEDOT-PSS or TFB and Poly-TPD to further optimize the hole injection efficiency and device performance.

[0045] Specifically, the gradient hole injection structure further includes at least one energy transition layer, and the energy transition layer has an energy level between the starting layer and the core layer to achieve a smooth transition of hole energy, further reducing ineffective exciton recombination and significantly improving the EQE of blue QLEDs.

[0046] Specifically, the PEDOT-PSS-free QLED structure includes the following steps:

[0047] Step 1: Use PTAA as the hole injection layer and form a binary PTAA-F4-TCNQ HIL structure by doping F4-TCNQ, so that the structure not only has excellent hole injection ability, but also can effectively suppress the stability problem caused by PEDOT-PSS;

[0048] Step 2: depositing one or more layers of gradient hole transport materials with specific energy levels and thicknesses on the binary PTAA-F4-TCNQHIL structure to further optimize the hole transport path and injection efficiency;

[0049] Step 3: Deposit a blue QD emission layer, an electron transport layer and a metal electrode in sequence on the gradient hole transport material to form a complete QLED device structure, which significantly improves the stability and long-term working reliability of the device while ensuring efficient luminescence performance.

[0050] Specifically, the gradient hole transport material includes Poly-TPD, small molecule tri-TCTA or a material with energy level and hole transport properties to achieve gradual reduction of hole energy and efficient injection. The EQE improvement efficiency of the blue light QLED is 20%, and the device exhibits excellent stability and reliability under long-term working conditions, meeting the demand for high-performance blue light QLED devices in practical applications. The gradient hole injection material adopts a multi-component mixed system, and by adjusting the proportion and type of each component, a composite material with a continuous gradient energy level distribution is formed to better match the energy level difference between different layers, so as to achieve efficient transmission and injection of hole energy. Between the layers of the gradient hole injection structure, by precisely controlling the deposition conditions and material ratios, a nanoscale smooth transition interface is formed, which further reduces the energy loss and charge load at the interface and improves the hole injection efficiency.

[0051] As can be seen from the above, by introducing a gradient hole injection structure, the gradual reduction of hole energy and efficient injection are achieved. In particular, by finely tailoring the highest occupied molecular orbital energy level of Poly-TPD and introducing an energy transition layer, invalid exciton recombination is further reduced, and the EQE of the blue light QLED is significantly improved. The experimental results show that the EQE of the blue light QLED device of the present invention can be improved by more than 20%;

[0052] The present invention adopts a gradient hole transport material of a multi-component mixed system, and by adjusting the proportion and type of each component, a composite material with a continuous gradient energy level distribution is formed. This material can better match the energy level differences between different layers, achieve efficient transmission and injection of hole energy, and further improve the performance of blue light QLED.

[0053] Specifically, the improvement model formula of the gradient hole injection efficiency is:

[0054]

[0055] in, is the hole injection efficiency under the gradient hole injection structure, is the hole injection efficiency in the gradient-free structure, ΔE barrier is the energy barrier reduced by the gradient structure, and k is the proportional coefficient between the energy barrier reduction and the injection efficiency improvement, which is obtained by fitting the experimental data.

[0056] Preferably, the external quantum efficiency improvement formula of the blue light QLED is:

[0057]

[0058] Among them, EQE base is the external quantum efficiency of the gradient-free structure, η exc is the exciton recombination efficiency.

[0059] Specifically, in the PEDOT-free PSSQLED structure, an intelligent adaptive doping technology is used, and the concentration and type of dopants are dynamically adjusted according to the working state of the device and changes in the external environment to optimize the electrical performance and stability of the hole injection layer;

[0060] As can be seen from the above, in the PEDOT-PSSQLED-free structure, the present invention adopts intelligent adaptive doping technology to dynamically adjust the concentration and type of dopants according to the working state of the device and changes in the external environment. At the same time, a nano-scale smooth transition interface is formed between the layers of the gradient hole injection structure, which further reduces the energy loss and charge load at the interface and improves the hole injection efficiency. These innovative technical features jointly promote a significant improvement in the performance of blue light QLEDs.

[0061] The use of a PEDOT-PSS-free QLED structure effectively avoids the stability problem caused by PEDOT-PSS. At the same time, by optimizing the ratio and type of the hole injection layer and the gradient hole transport material, the stability and long-term working reliability of the device are further improved, which makes the blue light QLED device of the present invention have a longer service life and better performance in practical applications.

[0062] In summary, the present invention significantly improves the external quantum efficiency (EQE) of blue light QLED by introducing a gradient hole injection structure and a PEDOT-PSS-free QLED structure, while enhancing the stability and long-term working reliability of the device. These innovative technical features jointly promote a significant improvement in the performance of blue light QLED and provide strong support for the application of QLED technology in fields such as displays and solid-state lighting.

[0063] It should be noted that: with the continuous development of QLED technology, improving the external quantum efficiency of blue light QLED will become an important research direction in the future. By continuously optimizing the quantum dot structure, introducing the interface modification layer, improving the carrier transport layer, adopting new quantum dot materials and enhancing the light coupling output, the luminescence performance and stability of blue light QLED can be further improved, promoting its application in fields such as displays and solid-state lighting.

[0064] Furthermore, this design application is used to improve the external quantum efficiency of blue light QLED. The present invention adopts a gradient hole transport material of a multi-component mixed system, and by adjusting the proportion and type of each component, a composite material with a continuous gradient energy level distribution is formed. This material can better match the energy level differences between different layers, realize efficient transmission and injection of hole energy, and further improve the performance of blue light QLED.

[0065] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0066] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0067] In the drawings of the embodiments disclosed in the present invention, only the structures involved in the embodiments disclosed in the present invention are involved, and other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other.

[0068] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for improving the external quantum efficiency of a blue light QLED, characterized in that: include: A gradient hole injection structure and a PEDOT-PSSQLED-free structure, wherein the gradient hole injection structure is formed by introducing multiple layers of gradient holes with gradient energy level distribution between a typical hole transport layer and a blue quantum dot emission layer to inject materials; The core layer of the gradient hole injection material is Poly-TPD, and the energy level of the highest occupied molecular orbital of the Poly-TPD is finely customized by the small molecule tri-TCTA; The starting layer of the gradient hole injection structure is a composite layer formed by PEDOT-PSS or TFB and Poly-TPD.

2. The method for improving the external quantum efficiency of a blue light QLED according to claim 1, characterized in that: The gradient hole injection structure further includes at least one energy transition layer, and the energy transition layer has an energy level between the starting layer and the core layer.

3. The method for improving the external quantum efficiency of a blue light QLED according to claim 1, characterized in that: The PEDOT-free PSSQLED structure comprises the following steps: Step 1: Use PTAA as a hole injection layer and form a binary PTAA-F4-TCNQ HIL structure by doping F4-TCNQ; Step 2: depositing one or more layers of gradient hole transport materials with specific energy levels and thicknesses on the binary PTAA-F4-TCNQHIL structure to further optimize the hole transport path and injection efficiency; Step 3: Deposit the blue QD emission layer, electron transport layer and metal electrode in sequence on the gradient hole transport material to form a complete QLED device structure.

4. The method for improving the external quantum efficiency of a blue light QLED according to claim 1, characterized in that: The gradient hole transport material includes Poly-TPD, small molecule tri-TCTA or a material with energy level and hole transport performance.

5. The method for improving the external quantum efficiency of a blue light QLED according to claim 1, characterized in that: The EQE improvement efficiency of the blue light QLED is 20%.

6. The method for improving the external quantum efficiency of a blue light QLED according to claim 1, characterized in that: The model formula for improving the gradient hole injection efficiency is: in, is the hole injection efficiency under the gradient hole injection structure, is the hole injection efficiency in the gradient-free structure, ΔE barrier is the energy barrier reduced by the gradient structure, and k is the proportional coefficient between the energy barrier reduction and the injection efficiency improvement, which is obtained by fitting the experimental data.

7. The method for improving the external quantum efficiency of a blue light QLED according to claim 1, characterized in that: The external quantum efficiency improvement formula of the blue light QLED is: Among them, EQE base is the external quantum efficiency of the gradient-free structure, η exc is the exciton recombination efficiency.

8. The method for improving the external quantum efficiency of a blue light QLED according to claim 1, characterized in that: The gradient hole injection material adopts a multi-component mixed system, and forms a composite material with a continuous gradient energy level distribution by adjusting the proportion and type of each component.

9. The method for improving the external quantum efficiency of a blue light QLED according to claim 3, characterized in that: In the PEDOT-free PSSQLED structure, an intelligent adaptive doping technology is used, and the concentration and type of the dopant are dynamically adjusted according to the working state of the device and changes in the external environment to optimize the electrical performance and stability of the hole injection layer.

10. The method for improving the external quantum efficiency of a blue light QLED according to claim 1, characterized in that: Between the layers of the gradient hole injection structure, a nanoscale smooth transition interface is formed by precisely controlling deposition conditions and material ratios.

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