Method for improving performance stability of QLED device by using negative pressure processing

Abstract

The invention discloses a method for improving the performance stability of a QLED device through negative pressure processing. According to the method, after functional layer deposition and electrode evaporation of the QLED device are completed, the QLED device is placed in a negative pressure environment to be processed. Compared with a natural positive aging process which is long in time consumption and unstable in the prior art, the negative pressure treatment provided by the invention is a simple, convenient, efficient and controllable technological means. According to the method, rapid pre-stabilization of the device can be completed in only about three days, and the processing time is remarkably shortened. After being processed by the method, key performance parameters such as brightness, external quantum efficiency and the like of the QLED device are remarkably improved and stabilized, the problem of color shift caused by inconsistent aging of red, green and blue light devices is effectively relieved, the batch consistency and predictability of device production are improved, and the method has important industrial application prospects.

Description

A method for improving the performance stability of QLED devices using negative pressure treatment Technical Field

[0001] This invention relates to the field of quantum dot light-emitting diode technology, and in particular to a method for improving the performance stability of QLED devices using negative voltage processing. Background Technology

[0002] Quantum dot light-emitting diodes (QLEDs) have attracted much attention in the display field due to their excellent color gamut, brightness, and efficiency. However, QLED devices, especially those using zinc oxide-based materials (such as ZnO and ZMO) as the electron transport layer (ETL), commonly exhibit a phenomenon known as "positive aging." This means that in the initial storage or use after fabrication, the brightness and efficiency of the device abnormally increase over time, rather than degrade.

[0003] While "positive aging" can improve performance, the process is slow, uncontrollable, and fraught with uncertainty. Inconsistent aging rates among red, green, and blue QLED devices can lead to severe color shifts, affecting the color stability and consistency of display products. Furthermore, this instability poses significant challenges to the design and debugging of device driver circuits, severely restricting the large-scale production and application of QLED technology. Existing research largely focuses on explaining its mechanism, generally believing it to be closely related to defect states such as hydroxyl groups and oxygen vacancies in the ZnO-based electron transport layer, but lacks an effective industrial method to actively utilize and control this process. Traditional methods of waiting for natural aging are time-consuming (typically over 60 days), unable to meet the demands of industrial-scale production.

[0004] Therefore, there is an urgent need in the field for a technical solution that can quickly and controllably complete the "positive aging" process of QLED devices and achieve pre-stabilization of their performance in order to solve the problems mentioned in the background. Summary of the Invention

[0005] The purpose of this invention is to provide a method for rapidly improving the performance stability of QLED devices using negative pressure treatment, so as to overcome the defects of the long time-consuming and uncontrollable "positive aging" process in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for improving the performance stability of QLED devices using negative pressure treatment is provided, comprising the following steps: S1, preparing a QLED semi-finished device (the device includes a substrate, an anode, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer, and a cathode arranged sequentially); S2, subjecting the QLED device semi-finished product to negative pressure treatment: placing the device in a negative pressure environment and treating it with a preset pressure and time to accelerate its performance stabilization process and improve its photoelectric performance.

[0007] Preferably, the electron transport layer is a zinc oxide-based material, including pure zinc oxide quantum dots, lithium-doped zinc oxide quantum dots (LZO), aluminum-doped zinc oxide (AZO), and magnesium-doped zinc oxide (ZMO), etc.

[0008] Preferably, the negative pressure treatment pressure is -0.08MPa to -85 kPa, and the treatment environment is anhydrous and oxygen-free.

[0009] Preferably, the negative pressure treatment is intended to reduce hydroxyl (-OH) defects and / or oxygen vacancy defects in the zinc oxide-based material in the electron transport layer.

[0010] Preferred: Through the negative pressure treatment, two adjacent hydroxyl groups in the zinc oxide-based material undergo a condensation reaction to generate water molecules and desorb them. At the same time, the released oxygen ions (O2-) fill the oxygen vacancy defects. The chemical reaction process is roughly as follows: -OH+-OH→H2O+O2-. The QLED device is prepared according to the method of improving the performance stability of QLED devices by using negative pressure treatment.

[0011] This method involves applying a negative pressure environment after device fabrication to actively and rapidly induce and complete the device's performance stabilization process. This negative pressure environment can effectively remove quenching sites such as hydroxyl groups in the electron transport layer (especially the ZMO layer) and passivate defects such as oxygen vacancies, thereby achieving a significant improvement and stabilization of the device's optoelectronic performance in a short period of time (3 days).

[0012] Compared with the prior art, the beneficial effects of the present invention are: 1. High efficiency and speed: The natural aging process that takes several weeks or even months is shortened to a few days, which greatly improves production efficiency.

[0013] 2. Performance improvement: The processed device shows significant improvements in startup voltage, brightness, current efficiency, and external quantum efficiency.

[0014] 3. High controllability and predictability: A standardized process is provided to ensure the consistency and stability of device performance at the factory, solve problems such as color shift, and has extremely high industrial application value. Figure 1 is a schematic diagram of the structure of the quantum dot light-emitting diode device provided in the embodiment of this application.

[0015] Figure 2 is an electron microscope scan of the cross-section of the quantum dot light-emitting diode device provided in the embodiment of this application.

[0016] Figure 3 shows a performance comparison between the red CdSe-based QLED device provided in the embodiments of this application after negative voltage treatment and the newly manufactured device, confirming that the method can significantly improve the external quantum dot efficiency (Figure 3a), reduce the start-up voltage (Figure 3b), and improve the brightness (Figure 3c) and power efficiency (Figure 3d).

[0017] Figure 4 is an X-ray photoelectron spectroscopy (XPS) spectrum of the quantum dot light-emitting diode device provided in the embodiments of this application.

[0018] Figure 5 shows the Fourier transform infrared (FTIR) and fluorescence spectra of the quantum dot light-emitting diode device provided in the embodiments of this application.

[0019] Figure 6 is a performance comparison diagram of the red CdSe-based QLED device of the quantum dot light-emitting diode device provided in the embodiments of this application after being treated under normal pressure and the newly manufactured device.

[0020] Figure 7 is a performance comparison diagram of the green InP-based QLED device of the quantum dot light-emitting diode device provided in the embodiments of this application after negative pressure treatment and the newly manufactured device.

[0021] Figure 8 shows a performance comparison between the blue ZnSe-based QLED device provided in the embodiments of this application after negative pressure treatment and the newly manufactured device. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments; the embodiments of the present invention are given for illustrative and descriptive purposes, and are not intended to be exhaustive or to limit the invention to the forms disclosed; many modifications and variations will be apparent to those skilled in the art; the embodiments were chosen and described in order to better illustrate the principles and practical applications of the invention, and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose; Embodiment 1

[0023] This embodiment provides a method for improving the performance stability of QLED devices using negative pressure treatment. The specific steps are as follows: S1. Preparation of QLED semi-finished device: The QLED prototype device includes a substrate, an anode, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer, and a cathode arranged sequentially. ITO glass is used as the substrate. After strict cleaning and pretreatment, poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate layer (PEDOT:PSS) is spin-coated as the hole injection layer, [(9,9-dioctylfluorene-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl)diphenylamine)] (TFB) is spin-coated as the hole transport layer, CdSe / ZnS red quantum dots are used as the light-emitting layer, and magnesium-doped zinc oxide (ZMO) is used as the electron transport layer. Finally, Ag electrodes are deposited by vacuum evaporation. The device structure is shown in Figure 1, and the cross-sectional view of the device is shown in Figure 2.

[0024] S2. Perform negative pressure treatment on the QLED device semi-finished product: Place the prepared red QLED device in an anhydrous and oxygen-free glove box with a vacuum degree of -0.1 MPa and perform negative pressure treatment for 3 consecutive days.

[0025] The electron transport layer is a zinc oxide-based material, including pure zinc oxide quantum dots, lithium-doped zinc oxide quantum dots (LZO), aluminum-doped zinc oxide (AZO), and magnesium-doped zinc oxide (ZMO), etc.

[0026] The negative pressure treatment is performed at a pressure ranging from -0.08 MPa to -85 kPa, and the treatment environment is anhydrous and oxygen-free.

[0027] The negative pressure treatment aims to reduce hydroxyl (-OH) defects and / or oxygen vacancy defects in the zinc oxide-based material in the electron transport layer.

[0028] Through the negative pressure treatment, two adjacent hydroxyl groups in the zinc oxide-based material undergo a condensation reaction to generate water molecules and desorb them. At the same time, the released oxygen ions (O2-) fill the oxygen vacancy defects. The chemical reaction process is roughly as follows: -OH+-OH→H2O+O2-. QLED devices are prepared according to the method of improving the performance stability of QLED devices by using negative pressure treatment.

[0029] Performance Comparison Test: The device performance was compared before negative voltage treatment (fresh state) and after 3 days of treatment. As shown in Figure 3, the peak EQE of the device increased from 6.4% to 8.7% after treatment, the startup voltage decreased from 2.9V to 2.4V, and the brightness and current efficiency were also significantly improved. This indicates that negative voltage treatment significantly improves device performance.

[0030] Mechanism Verification: To investigate the mechanism, X-ray photoelectron spectroscopy (XPS), fluorescence spectroscopy, and Fourier transform infrared (FTIR) tests were performed on the ZMO thin film. As shown in Figure 4, after negative pressure treatment, the peak area ratios corresponding to hydroxyl (Oiii) and oxygen vacancy (Oii) in the O1s spectrum decreased significantly, with a reduction ratio close to 2:1. The intensity of the absorption peak at the hydroxyl (OH) vibration position of the treated ZMO thin film was significantly reduced (Figure 5a), and the fluorescence spectroscopy data also showed that the intensity of the defect fluorescence peak generated by the defects in the ZMO material itself was significantly reduced after negative pressure treatment (Figure 5b). This evidence strongly demonstrates that negative pressure treatment reduces defects by promoting the removal of hydroxyl groups and filling oxygen vacancies, thereby improving device performance (Figure 5c).

[0031] Control group experiment: Another group of identical newly manufactured devices were placed in a glove box under normal pressure for 3 days. As shown in Figure 7, their performance hardly changed, which conversely proves that "negative pressure" is a key factor in achieving rapid performance improvement of the device.

[0032] Examples 2 & 3: Verification of the Universality of Green and Blue Light Devices To verify the universality of this method, InP-based green QDs and ZnSe-based blue QDs were used, and the steps of Example 1 were repeated. As shown in Figures 7 and 8, after undergoing the same negative voltage treatment, the EQE, brightness, and efficiency of both green and blue devices were significantly improved. This indicates that the method of the present invention has a positive effect on QLED devices with different types and colors of luminescent quantum dot materials, and its core lies in improving the universal ZnO-based electron transport layer.

[0033] In summary, this invention successfully addresses the industry pain point of slow and uncontrollable "positive aging" in QLEDs by introducing an innovative negative pressure post-processing technique. This method not only rapidly and stably improves the photoelectric performance of devices, but its underlying clear physicochemical mechanism has also been fully experimentally verified. This technical solution is simple, cost-effective, and highly efficient, paving the way for the commercial application of high-performance, high-stability QLED display technology.

[0034] Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments; based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art and related fields without creative effort should fall within the scope of protection of the present invention; structures, devices and operating methods not specifically described and explained in the present invention shall be implemented in accordance with conventional means in the art unless otherwise specified and limited.

Claims

1. A method for improving the performance stability of QLED devices using negative pressure treatment, characterized in that, Includes the following steps: S1. Prepare a QLED semi-finished device; S2. Perform negative pressure treatment on the QLED semi-finished device: place the device in a negative pressure environment and perform treatment with a preset pressure and time to accelerate its performance stabilization process and improve its photoelectric performance.

2. The method for improving the performance stability of QLED devices using negative pressure treatment according to claim 1, characterized in that: The electron transport layer is a zinc oxide-based material, including pure zinc oxide quantum dots, lithium-doped zinc oxide quantum dots (LZO), aluminum-doped zinc oxide (AZO), and magnesium-doped zinc oxide (ZMO), etc.

3. The method for improving the performance stability of QLED devices using negative pressure treatment according to claim 1, characterized in that: The negative pressure treatment is performed at a pressure ranging from -0.08 MPa to -85 kPa, and the treatment environment is anhydrous and oxygen-free.

4. The method for improving the performance stability of QLED devices using negative pressure treatment according to claim 3, characterized in that: The negative pressure treatment aims to reduce hydroxyl (-OH) defects and / or oxygen vacancy defects in the zinc oxide-based material in the electron transport layer.

5. The method for improving the performance stability of QLED devices using negative pressure treatment according to claim 4, characterized in that: Through the negative pressure treatment, two adjacent hydroxyl groups in the zinc oxide-based material undergo a condensation reaction to generate water molecules, which then desorb, releasing oxygen ions (O2). 2- The chemical reaction process for filling oxygen vacancies is roughly as follows: -OH + -OH → H₂O + O₂ 2- .

6. A QLED device prepared by the method of improving the performance stability of a QLED device using negative pressure treatment according to any one of claims 1-5.

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