Zhang Qianmin, Jiang Jixin, Xu Zheng, Song Dandan, Qiao Bo, Zhao Suling, Wageh S, Al-Ghamdi Ahmed
Key Laboratory of Luminescence and Optical Information, Beijing Jiaotong University, Ministry of Education Beijing 100044 China
Department of Physics, Faculty of Science, King Abdulaziz University Jeddah 21589 Saudi Arabia.
RSC Adv. 2021 Jul 13;11(39):24436-24442. doi: 10.1039/d1ra01567b. eCollection 2021 Jul 6.
Deep-red organic light-emitting diodes (DR-OLEDs) or near-infrared organic light-emitting diodes (NIR-OLEDs) have a wide range of applications in real life, such as special light sources for plant growth in agriculture, optical communications, infrared imaging, infrared medical imaging and other fields. However, the device performance of DR-OLEDs is still far behind that of red, green and blue OLEDs. In addition to the well-known energy gap law, the location of the recombination region also has a significant impact on the device performance. If the recombination area is too close to the cathode, the electrons in the electron transport layer will easily cause exciton quenching. In this study, for the first time, we adopted a quantum well-like structure by changing the host (CBP) and guest (TPA-DCPP) thicknesses as the light-emitting layer to manage the position of the recombination zone, and then improved the carrier injection and transportation as well as increased the exciton recombination rate. Furthermore, we introduced a hole trap layer to reduce the current density and suppress the recombination zone movement; finally, we prepared high-brightness and high-efficiency DR-OLEDs based on the TADF material with a wavelength of 674 nm, a maximum brightness of 1151 cd m and a maximum EQE of 4.4%.
深红色有机发光二极管（DR-OLED）或近红外有机发光二极管（NIR-OLED）在现实生活中有广泛应用，例如农业中用于植物生长的特殊光源、光通信、红外成像、红外医学成像等领域。然而，DR-OLED的器件性能仍远远落后于红色、绿色和蓝色OLED。除了众所周知的能隙定律外，复合区域的位置对器件性能也有重大影响。如果复合区域离阴极太近，电子传输层中的电子很容易导致激子猝灭。在本研究中，我们首次通过改变主体（CBP）和客体（TPA-DCPP）的厚度采用类量子阱结构作为发光层来控制复合区的位置，进而改善载流子注入和传输并提高激子复合率。此外，我们引入了空穴陷阱层以降低电流密度并抑制复合区移动；最后，我们基于TADF材料制备了波长为674 nm、最大亮度为1151 cd m且最大外量子效率为4.4%的高亮度和高效率DR-OLED。
