New‐Fashioned Universal and Functional Host‐Material from a Near‐Ultraviolet Organic Emitter for High‐Efficiency Organic Light‐Emitting Diodes with Low Efficiency Roll‐Offs
Xuecheng Guo, Ganggang Li, Jingli Lou, Kongqi Chen, Ruishan Huang, Dezhi Yang, Han Zhang, Zhiming Wang, Ben Zhong Tang
Abstract
Abstract In this work, a near‐ultraviolet (NUV) emitter, 2MCz‐CNMCz, with hot‐exciton property is designed based on a “long‐short axis” strategy, which exhibits good thermal stability, bipolar carrier transport ability, and high T 1 energy level. Its nondoped NUV organic light‐emitting diode (OLED) achieves a record maximum external quantum efficiency (η ext ) of 7.76%, with a peak at 404 nm and CIE coordinates of (0.158, 0.039). The corresponding high exciton utilization efficiency (η r ) in the electroluminescence process reveals its potential as a functional sensitizing host. As expected, the TBPe‐based blue fluorescent OLED with 2MCz‐CNMCz as the host material shows better efficiency and lower efficiency roll‐off than that with traditional host material mCP. Meanwhile, the Ir complexes‐based green/yellow/red phosphorescent OLEDs with 2MCz‐CNMCz host are also fabricated, reaching high η ext values of 26.1%, 30.4%, and 20.4%, respectively, and displaying negligible efficiency roll‐offs at 1000 cd m −2 , which are among the best OLED performances based on the same emitters. To the authors’ best knowledge, this is the first report on the design of high‐quality universal and functional host material, and may bring new inspiration to the preparation of high‐efficiency, low roll‐off, full‐color OLEDs.