Views: 0 Author: Site Editor Publish Time: 2024-12-05 Origin: Site
Quantum dot light-emitting diode (QLED) has become a promising technology in the next generation of display applications. Compared with traditional light-emitting diodes (LEDs) including organic LEDs, liquid crystal displays, and micro LEDs, QLED has the advantages of tunable emission, high color purity, strong flexibility, and higher energy efficiency.In recent years, significant progress has been made in developing high-performance QLEDs in red, green, and blue regions.For example, it has been reported that the excellent external quantum efficiencies (EQEs) of red, green, and blue QLED devices are 44.5%, 30.3%, and 28.7%, respectively. At an initial brightness of 100cd/cm2, the half-life (T50) of red and green QLEDs exceeds 1.8 million hours and 2.57 million hours, respectively. Although the device performance of red and green QLEDs is excellent, the device parameters (including EQE and lifespan) of blue QLEDs are relatively backward, which hinders the commercialization process of this technology.
Due to the wide bandgap of blue quantum dots, the charge injection efficiency of blue QLEDs is lower compared to red and green devices, resulting in poorer device performance. People have been trying to improve the charge injection performance of blue light-emitting devices. In the design of quantum dots, the charge injection barrier has been reduced by customizing the core-shell gradient components and optimizing the core-shell thickness. Ligand exchange, such as chlorination of quantum dots, has also been proven to be an effective method for manipulating charge injection energy barriers. In addition, fine-tuning the work function of the charge transport layer can also improve the charge injection characteristics of QLED devices. In addition to various operation methods for customizing charge injection barriers, QLED devices also have a unique characteristic that can improve device performance.The performance of QLED devices, including EQE and lifespan, known as positive aging, often improves with prolonged storage time. People have been working hard to understand the reasons behind this phenomenon and have discovered that the chemical reaction between the acidic gases released by the acrylic resin used for device packaging and the electron transport layer (ETL) is the cause. The above customization methods have technical difficulties in material modification, and the positive aging effect cannot be controlled, both of which are not conducive to the commercialization of this technology.
Xiongfeng Lin et al. from TCL Industrial Research Institute introduced a simple annealing post-treatment method for QLED devices, which can significantly improve device efficiency by about 20%. The enhancement of charge injection and improvement of charge balance are the reasons for the improvement of device performance. In addition, the backward firing process has been proven to be a universal method suitable for QLEDs with various metal electrodes.
