OLED device with enhanced light emitting performance and preparation thereof
By setting a carbon quantum dot layer in OLED devices to form a step effect and energy transfer mechanism, the problem of insufficient luminescence performance of red and blue light materials was solved, and the luminous efficiency and brightness were improved, while simplifying the fabrication process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGZHOU AOSHI TECHNOLOGY CO LTD
- Filing Date
- 2026-06-10
- Publication Date
- 2026-07-31
AI Technical Summary
In existing OLED devices, the red and blue light materials have low quantum efficiency, insufficient luminous intensity, and short lifespan, which affects the overall display effect.
A first carbon quantum dot layer is set below the red light emitting layer to form a step effect to reduce the hole injection energy barrier, and a second carbon quantum dot layer is set above the blue light emitting layer to enhance the luminescence performance through electron capture and energy transfer. At the same time, the same nitrogen-doped carbon quantum dot solution and spin coating process are used to achieve dual functional enhancement.
It significantly improves the luminous efficiency and brightness of red and blue light, optimizes the balance between carrier injection and recombination, simplifies the preparation process, reduces the complexity of materials and processes, and is suitable for industrial mass production.
Smart Images
Figure CN122497225A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of organic electroluminescent materials technology, and in particular to an OLED device with enhanced luminescence performance and its fabrication. Background Technology
[0002] Organic light-emitting diodes (OLEDs) are considered a next-generation display technology due to their advantages such as thinness, high luminous efficiency, and low cost. Currently, full-color OLEDs mainly employ RGB three-primary-color emission methods, color conversion methods, and color filter methods. Among these, independent emission of RGB pixels is the most commonly used color mode, achieving true color by adjusting the mixing ratio of the three primary colors.
[0003] However, the development of the three primary color materials in current technologies is unbalanced: green light materials are already in mass production capability, but red and blue light materials still suffer from problems such as low quantum efficiency, insufficient luminous intensity, and short lifespan. Therefore, improving the luminous performance of red and blue light in OLED devices has become the key to enhancing the overall display effect. Summary of the Invention
[0004] The purpose of this invention is to provide an OLED device with enhanced light emission performance and its fabrication. By setting a first carbon quantum dot layer below the red light emitting layer to form a step effect, the hole injection energy barrier is reduced and the red light emission efficiency is improved. A second carbon quantum dot layer is set above the blue light emitting layer to enhance the blue light emission performance through electron capture and energy transfer. At the same time, the same nitrogen-doped carbon quantum dot solution and spin coating process are used to achieve one material, two coatings, and dual functions.
[0005] To achieve the above objectives, the present invention provides an OLED device with enhanced light-emitting performance, comprising an anode, a hole transport layer, a red light-emitting layer, a green light-emitting layer, a blue light-emitting layer, an electron transport layer, and a cathode, and further comprising: The first carbon quantum dot layer, located below the red light emitting layer, is used to adjust the energy level structure and form a step effect to regulate the recombination position and recombination efficiency of electron-hole pairs, thereby enhancing the red light emitting performance. The second carbon quantum dot layer, located above the blue light emitting layer, is used to capture electrons, form excitons with holes, and transfer energy to the blue light emitting layer through energy transfer, thereby enhancing the blue light emitting performance.
[0006] Preferably, both the first carbon quantum dot layer and the second carbon quantum dot layer are nitrogen-doped carbon quantum dot materials.
[0007] The fabrication of the aforementioned OLED device with enhanced luminous performance includes the following steps: S1. Prepare carbon quantum dot solution; S2. After the anode and hole transport layer are prepared, the carbon quantum dot solution is spin-coated to form the first carbon quantum dot layer below the red light emitting layer. S3. Sequentially vapor-deposit a red light-emitting layer, a green light-emitting layer, and a blue light-emitting layer; S4. A second carbon quantum dot layer is formed on top of the blue light-emitting layer by spin coating of carbon quantum dot solution; S5. Continue to deposit the electron transport layer and cathode, and then encapsulate to obtain the OLED device.
[0008] Preferably, in S1, the carbon quantum dot solution is prepared by: adding citric acid and urea to water and stirring evenly, heating in a microwave device, then dialyzing and centrifuging to obtain a black solid, which is then dissolved in ethanol to obtain a carbon quantum dot solution.
[0009] Preferably, in S1, the mass ratio of citric acid to urea is 1:2.
[0010] Preferably, in S1, the power of the microwave device is 700-780W, the heating temperature is 180-202℃, and the heating time is 10-20min.
[0011] Preferably, in S2, the rotation speed of spin coating is 2000 rpm, the spin coating time is 40 s, and the thickness of the first carbon quantum dot layer is 100-130 nm.
[0012] Preferably, in S4, the spin coating speed is 2000 rpm, the spin coating time is 40 s, and the thickness of the second carbon quantum dot layer is 100-130 nm.
[0013] Therefore, the present invention employs the above-mentioned OLED device with enhanced light-emitting performance and its fabrication, which has the following beneficial effects: (1) By setting a first carbon quantum dot layer below the red light emitting layer, the energy level modulation characteristics of carbon quantum dots are used to form a step effect, which effectively reduces the energy barrier for hole injection into the red light emitting layer, allowing more holes and electrons to recombine in the red light emitting layer, thereby significantly improving the quantum efficiency, luminous brightness and device stability of the red light material.
[0014] (2) By setting a second carbon quantum dot layer above the blue light emitting layer, the strong electron-capturing ability of the nitrogen-doped carbon quantum dot surface groups is utilized to form excitons in the carbon quantum dot layer, and the exciton energy is efficiently transferred to the blue light emitting layer through energy transfer, thereby effectively compensating for the defects of insufficient luminous intensity and low exciton utilization of blue light materials, and greatly improving the luminous performance of blue light.
[0015] (3) The two layers of carbon quantum dots are located at the hole input end and the electron input end of the device, respectively, forming a symmetrical auxiliary relationship in electrical engineering. They do not interfere with each other's electric field distribution and jointly optimize the carrier injection and recombination balance of the whole device. The two different enhancement mechanisms (step effect and energy transfer) target the different physical bottlenecks of red light and blue light, respectively, and achieve functional complementarity in the same device, avoiding the structural redundancy and process complexity of fabricating a single improved device separately.
[0016] (4) Using the same nitrogen-doped carbon quantum dot solution and the same spin coating process, films are formed twice, before and after the evaporation of the three primary color materials, achieving a simple design of "one material, two coatings, and dual functions". This preparation method is highly compatible with existing OLED evaporation processes, eliminating the need to develop multiple materials or multiple deposition equipment, significantly reducing material costs and process complexity, and facilitating industrial mass production.
[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the structure of an OLED device with enhanced light-emitting performance and its fabrication embodiment 1 according to the present invention; Figure 2 This is a comparison diagram of the effects of an OLED device with enhanced luminous performance and its preparation in Example 1 and Comparative Example 1, where A is the JV curve, B is the efficiency-brightness curve, and C is the LV curve. Detailed Implementation
[0019] This invention provides an OLED device with enhanced light-emitting performance, comprising an anode, a hole transport layer, a red light-emitting layer, a green light-emitting layer, a blue light-emitting layer, an electron transport layer, and a cathode, and further comprising: The first carbon quantum dot layer, located below the red light emitting layer, is used to adjust the energy level structure and form a step effect to regulate the recombination position and recombination efficiency of electron-hole pairs, thereby enhancing the red light emitting performance. The second carbon quantum dot layer, located above the blue light emitting layer, is used to capture electrons, form excitons with holes, and transfer energy to the blue light emitting layer through energy transfer, thereby enhancing the blue light emitting performance.
[0020] In this invention, both the first carbon quantum dot layer and the second carbon quantum dot layer are nitrogen-doped carbon quantum dot materials.
[0021] The first carbon quantum dot layer utilizes the energy level characteristics of carbon quantum dots to form a "step energy level" below the red light emitting layer. This lowers the energy barrier for holes to enter the red light emitting layer from the hole transport layer (i.e., the step effect), allowing more holes and electrons to recombine within the red light emitting layer, thereby improving the luminous efficiency and brightness of red light.
[0022] The second carbon quantum dot layer contains abundant polar groups (such as carboxyl and amino groups) on its surface, which can effectively capture electrons injected from the cathode. The captured electrons and holes from the light-emitting layer form excitons in the carbon quantum dot layer, which transfer energy to the blue light-emitting layer through energy transfer (Förster or Dexter mechanism), thereby enhancing blue light emission.
[0023] Nitrogen doping can introduce additional surface states and defect levels, modulate the energy level positions (HOMO / LUMO) of carbon quantum dots, and enhance their electron trapping ability and exciton formation efficiency; at the same time, it can improve the fluorescence quantum yield and conductivity of carbon quantum dots, making them more suitable for the energy transfer and energy level modulation requirements in OLEDs.
[0024] The fabrication of the aforementioned OLED device with enhanced luminous performance includes the following steps: S1. Prepare carbon quantum dot solution; S2. After the anode and hole transport layer are prepared, the carbon quantum dot solution is spin-coated to form the first carbon quantum dot layer below the red light emitting layer. S3. Sequentially vapor-deposit a red light-emitting layer, a green light-emitting layer, and a blue light-emitting layer; S4. A second carbon quantum dot layer is formed on top of the blue light-emitting layer by spin coating of carbon quantum dot solution; S5. Continue to deposit the electron transport layer and cathode, and then encapsulate to obtain the OLED device.
[0025] In this invention, in S1, the carbon quantum dot solution is prepared by adding citric acid and urea to water and stirring until homogeneous, heating in a microwave device, then obtaining a black solid by dialysis and centrifugation, and then dissolving it in ethanol to obtain a carbon quantum dot solution.
[0026] In this invention, in S1, the mass ratio of citric acid to urea is 1:2. Urea, as a nitrogen source, when used in excess, can promote nitrogen doping of the carbon framework, forming high contents of pyridine nitrogen, pyrrole nitrogen, and graphitic nitrogen. These nitrogen sites are active centers for electron trapping and exciton formation. Optimizing this ratio can achieve the best doping efficiency and carbon quantum dot yield.
[0027] The first and second carbon quantum dot layers were prepared using the exact same nitrogen-doped carbon quantum dot solution and the same spin-coating process, achieving "one material, two coatings, dual functions." This high degree of material and process uniformity not only reduces material development costs and preparation complexity but also ensures consistent film quality and good compatibility with existing OLED evaporation processes. Using different materials to enhance red and blue light separately would require two material systems and two deposition equipment, while this solution simplifies complexity and demonstrates ingenious technological synergy.
[0028] In this invention, in step S1, the microwave device has a power of 700-780W, a heating temperature of 180-202℃, and a heating time of 10-20min. The microwave power determines the heating rate and the intensity of the reaction. Appropriately high power can rapidly carbonize the precursor and uniformly nucleate it, forming small-sized carbon quantum dots with a narrow particle size distribution, which is beneficial to the uniformity of film formation and the consistency of energy levels.
[0029] Temperature controls the degree of carbonization and the retention of surface functional groups. Too low a temperature results in incomplete carbonization, while too high a temperature leads to over-graphitization and loss of surface functional groups. A suitable temperature preserves abundant carboxyl, hydroxyl, and amino groups, which are crucial for electron capture and solution stability. Too short a time results in insufficient carbonization, while too long a time leads to particle agglomeration or detachment of surface groups. Experimentally, this temperature range has been verified to yield nitrogen-doped carbon quantum dots with high yield, good dispersibility, and stable fluorescence properties.
[0030] Unreacted citric acid, urea, and small molecule byproducts (such as ammonia and cyanic acid) are removed to purify carbon quantum dots. Simultaneously, centrifugation can remove large particle agglomerates in stages, ensuring that the obtained carbon quantum dots have a uniform particle size, which is beneficial for spin coating to form a smooth and dense film.
[0031] Ethanol, as a polar solvent, exhibits good dispersibility for nitrogen-doped carbon quantum dots, and has a moderate boiling point and suitable surface tension, making it suitable for spin coating. At the same time, ethanol does not react adversely with organic light-emitting materials in OLEDs.
[0032] In this invention, in step S2, the spin coating speed is 2000 rpm, the spin coating time is 40 s, and the thickness of the first carbon quantum dot layer is 100-130 nm. The first carbon quantum dot layer is located below the red light emitting layer, and its thickness needs to be precisely controlled: if it is too thin, the step effect will be insignificant, and the energy level tuning capability will be weak; if it is too thick, the series resistance will increase, reducing the carrier injection efficiency. The optimized thickness can effectively control the hole injection and recombination positions without sacrificing voltage.
[0033] In this invention, in step S4, the spin coating speed is 2000 rpm, the spin coating time is 40 s, and the thickness of the second carbon quantum dot layer is 100-130 nm. The second carbon quantum dot layer is located above the blue light-emitting layer and is primarily responsible for capturing electrons and forming excitons. If the thickness is too thin, the capturing ability is insufficient; if it is too thick, electrons will have difficulty tunneling to the cathode, and the risk of exciton quenching will increase. An optimized thickness achieves a balance between electron capture and energy transfer.
[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the protection scope of the present invention.
[0035] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.
[0036] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.
[0037] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.
[0038] Example 1 like Figure 1 As shown, the present invention provides an OLED device with enhanced light-emitting performance, the preparation method of which includes the following steps: S1. Preparation of carbon quantum dot solution: Citric acid and urea were added to deionized water at a mass ratio of 1:2. After stirring evenly, the mixture was heated in a microwave oven with a power of 700-780W for 15 minutes to obtain a black solid. The black solid was then dissolved in ethanol after dialysis (using existing conventional dialysis methods) and centrifugation to obtain a nitrogen-doped carbon quantum dot solution.
[0039] S2. Fabrication of OLED devices: Hole transport layers are sequentially deposited on the ITO anode substrate using existing conventional preparation methods. A carbon quantum dot solution was prepared on the hole transport layer by spin coating at a speed of 2000 rpm for 40 s to form a first carbon quantum dot layer with a thickness of 100-130 nm. Red, green, and blue light-emitting layers are sequentially deposited (using existing conventional preparation methods); A second carbon quantum dot layer was prepared on the blue light emitting layer by spin coating, and the thickness of the second carbon quantum dot layer was 100-130 nm. Continue by evaporating the electron transport layer and cathode (using existing conventional preparation methods), and finally encapsulate to obtain the target device, denoted as AS01.
[0040] Comparative Example 1 This comparative example uses mainstream OLED display devices from 2023, denoted as STD(S).
[0041] The devices of Comparative Example 1 and Comparative Example 1 are composed of... Figure 2 It can be seen that the OLED device prepared in Example 1 has improved the brightness of red light and blue light by about 30% and 25% respectively, and the overall luminous efficiency of the device has been improved by more than 20%.
[0042] And by Figure 2 As can be seen from A in the figure, the starting points of Example 1 and Comparative Example 1 almost coincide. Under the same driving voltage, the current density of Example 1 is slightly higher than that of Comparative Example 1, indicating that Example 1 has better carrier injection / transmission efficiency, stronger device conduction capability, and lower internal resistance.
[0043] Depend on Figure 2 As shown in curve B, in the low-brightness region, the peak current efficiency of Example 1 is higher than that of Comparative Example 1, indicating that Example 1 has better electro-optical conversion efficiency and can output higher brightness under the same current. As brightness increases, both curves show a decrease in efficiency, but the decrease in Example 1 is more gradual. This means that Example 1 exhibits slower efficiency decay when operating at high brightness, making it more suitable for high-brightness applications (such as outdoor displays and high-brightness lighting), and effectively alleviating the common efficiency roll-off problem in OLED devices.
[0044] Depend on Figure 2 As shown in C, under the same driving voltage, the brightness of Example 1 is consistently higher than that of Comparative Example 1. At the highest test voltage, the brightness of Example 1 reaches approximately 7000 cd / m². 2 The comparative example 1 is only about 6300 cd / m³ 2 The increase was approximately 11%.
[0045] Therefore, the present invention employs the above-mentioned OLED device with enhanced light emission performance and its fabrication. By setting a first carbon quantum dot layer below the red light emitting layer to form a step effect, the hole injection energy barrier is reduced and the red light emission efficiency is improved. A second carbon quantum dot layer is set above the blue light emitting layer to enhance the blue light emission performance through electron capture and energy transfer. At the same time, the same nitrogen-doped carbon quantum dot solution and spin coating process are used to achieve one material, two coatings, and dual functions.
[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. An OLED device with enhanced light-emitting performance, comprising an anode, a hole transport layer, a red light-emitting layer, a green light-emitting layer, a blue light-emitting layer, an electron transport layer, and a cathode, characterized in that: Also includes: The first carbon quantum dot layer, located below the red light emitting layer, is used to adjust the energy level structure and form a step effect to regulate the recombination position and recombination efficiency of electron-hole pairs, thereby enhancing the red light emitting performance. The second carbon quantum dot layer, located above the blue light emitting layer, is used to capture electrons, form excitons with holes, and transfer energy to the blue light emitting layer through energy transfer, thereby enhancing the blue light emitting performance.
2. The OLED device with enhanced light-emitting performance according to claim 1, characterized in that: Both the first carbon quantum dot layer and the second carbon quantum dot layer are nitrogen-doped carbon quantum dot materials.
3. The fabrication of an OLED device with enhanced luminous performance as described in any one of claims 1-2, characterized in that: Includes the following steps: S1. Prepare carbon quantum dot solution; S2. After the anode and hole transport layer are prepared, the carbon quantum dot solution is spin-coated to form the first carbon quantum dot layer below the red light emitting layer. S3. Sequentially vapor-deposit a red light-emitting layer, a green light-emitting layer, and a blue light-emitting layer; S4. A second carbon quantum dot layer is formed on top of the blue light-emitting layer by spin coating of carbon quantum dot solution; S5. Continue to deposit the electron transport layer and cathode, and then encapsulate to obtain the OLED device.
4. The fabrication of an OLED device with enhanced light emission performance according to claim 3, characterized in that: In S1, the carbon quantum dot solution is prepared by adding citric acid and urea to water and stirring until homogeneous. The mixture is then heated in a microwave device, followed by dialysis and centrifugation to obtain a black solid, which is then dissolved in ethanol to obtain the carbon quantum dot solution.
5. The fabrication of an OLED device with enhanced light emission performance according to claim 4, characterized in that: In S1, the mass ratio of citric acid to urea is 1:
2.
6. The fabrication of an OLED device with enhanced light emission performance according to claim 4, characterized in that: In S1, the power of the microwave device is 700-780W, the heating temperature is 180-202℃, and the heating time is 10-20min.
7. The fabrication of an OLED device with enhanced light emission performance according to claim 3, characterized in that: In S2, the spin coating speed is 2000 rpm, the spin coating time is 40 s, and the thickness of the first carbon quantum dot layer is 100-130 nm.
8. The fabrication of an OLED device with enhanced light emission performance according to claim 3, characterized in that: In S4, the spin coating speed is 2000 rpm, the spin coating time is 40 s, and the thickness of the second carbon quantum dot layer is 100-130 nm.