A Multifunctional Bipolar Luminogen with Delayed Fluorescence for High‐Performance Monochromatic and Color‐Stable Warm‐White OLEDs
Jiajie Zeng, Jingjing Guo, Hao Liu, Zujin Zhao, Ben Zhong Tang
Abstract
Abstract Increasing exciton utilization and reducing exciton annihilation are crucial to achieve high performance of organic light‐emitting diodes (OLEDs), which greatly depend on molecular engineering of emitters and hosts. A novel luminogen (SBF‐BP‐DMAC) is synthesized and characterized. Its crystal and electronic structures, thermal stability, electrochemical behavior, carrier transport, photoluminescence, and electroluminescence are investigated. SBF‐BP‐DMAC exhibits enhanced photoluminescence and promotes delayed fluorescence in solid state and bipolar carrier transport ability, and thus holds multifunctionality of emitter and host for OLEDs. Using SBF‐BP‐DMAC as an emitter, the nondoped OLEDs exhibit maximum electroluminescence (EL) efficiencies of 67.2 cd A −1 , 65.9 lm W −1 , and 20.1%, and the doped OLEDs provide maximum EL efficiencies of 79.1 cd A −1 , 70.7 lm W −1 , and 24.5%. A representative orange phosphor, Ir(tptpy) 2 acac, is doped into SBF‐BP‐DMAC for OLED fabrication, giving rise to superior EL efficiencies of 88.0 cd A −1 , 108.0 lm W −1 , and 26.8% for orange phosphorescent OLEDs, and forward‐viewing EL efficiencies of 69.3 cd A −1 , 45.8 lm W −1 , and 21.0% for two‐color hybrid warm‐white OLEDs. All of these OLEDs can retain high EL efficiencies at high luminance, with very small efficiency roll‐offs. The outstanding EL performance demonstrates the great potentials of SBF‐BP‐DMAC in practical display and lighting devices.