Highly Efficient Organic Light-Emitting Diodes with Green and Sky-blue Iridium Complexes

• Main Authors: Yen-Po Wang, 王彥博
• Other Authors: Chih-Hao Chang
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/7dvj4h

碩士 === 元智大學 === 光電工程學系 === 106 === Phosphorescent organic light-emitting diodes (OLEDs) have been under intensive investigations in recent years because phosphorescent OLEDs (PhOLEDs) can utilize both singlet and triplet excitons, whereas fluorescent organic light-emitting diodes (OLEDs) can use only singlet excitons. The quantum efficiency of PhOLEDs can reach 100%, however, the quantum efficiency of fluorescent OLEDs can only reach 25%. For this reason, theoretically, the quantum efficiency of PhOLEDs could be higher by four times than that of fluorescent OLEDs. In this thesis, we focused on the development of new iridium-based phosphors and their electroluminescent applications. In the first part, a new series of sky-blue emitting iridium complexes were developed by Prof. Yun Chi’s group for constructing highly efficient sky-blue OLEDs. In order to improve the efficiencies of the tested devices, exciplex was used as the host to combine with these emitters, aiming to adjust the carrier balance. The maximum efficiencies of sky-blue OLEDs with Ir(1) were up to 20.9 %, 47.0 cd/A, and 47.9 lm/W while the Ir(2)-based OLEDs were achieving 19.3 %, 49.7 cd/A, and 39.6 lm/W. In the second part, we also collaborated with Prof. Chi's group to develop a new series of iridium complexes, including green-emitting Ir(3) and Ir(4). Similarly, exciplex was used as the host to adjust the carrier balance and thus improving the efficiencies. A maximum external quantum efficiency of 20.0 %, a luminance efficiency of 56.7 cd/A, and a power efficiency of 44.2 lm/W were obtained, which compares with 19.4 %, 57.7 cd/A, and 40.5 lm/W obtained for the OLEDs with Ir(4). Thus we can see that the high efficiencies of these OLED devices suggest the great potential for these iridium complexes in the fabrication of multicolored OLED devices.