Mixing a sterically bulky, electron-transporting host material into a conventional single host–guest emissive layer is demonstrated to suppress phase separation of the host matrix while increasing the efficiency and operational lifetime of deep-blue phosphorescent organic light-emitting diodes (PHOLEDs) with chromaticity coordinates of (0.14, 0.15). The bulky host enables homogenous mixing of the molecules comprising the emissive layer while suppressing single host aggregation; a significant loss channel of nonradiative recombination. By controlling the amorphous phase of the host-matrix morphology, the mixed-host device achieves a significant reduction in nonradiative exciton decay, resulting in 120 ± 6% increase in external quantum efficiency relative to an analogous, single-host device. In contrast to single host PHOLEDs where electrons are transported by the host and holes by the dopants, both charge carriers are conducted by the mixed host, reducing the probability of exciton annihilation, thereby doubling of the deep-blue PHOLED operational lifetime. These findings demonstrate that the host matrix morphology affects almost every aspect of PHOLED performance.
|Publication status||Accepted/In press - 2023|
Bibliographical noteFunding Information:
H.Z. and J.K. contributed equally to this work. The work was supported by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, award No. DE‐EE0009688 (J.K., device design). The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government. (J.K., H.Z., S.R.F., data collection and analysis) and Universal Display Corporation (J.K., lifetime studies). The authors thank the Lurie Nano Fabrication Facility at the University of Michigan for supporting the device processes. J.Y.L. acknowledges support from the Korean Ministry of Trade, Industry and Energy (20018956). X‐ray data acquisition and manuscript preparation by H.A. and K.D. are supported by ONR grant N000142012155. X‐ray data were acquired at the Advanced Light Source, which was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract DE‐AC02‐05CH11231.
© 2023 Wiley-VCH GmbH.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering