Presentation Information
[22p-P02-6]Judicious Design of Pyridine-based Hosts for Stable, Efficient, and Low-Driving Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes
〇(D)Yanmei Hu1, Alexander Civil2, Gerardus N. Iswara Lestanto1, Youichi Tsuchiya1, Chin-Yiu Chan3, Chihaya Adachi1 (1.Kyushu Univ., 2.Univ. of Queensland, 3.CityU of Hong Kong)
Keywords:
Thermally Activated Delayed Fluorescence,Host Material
Despite thermally activated delayed fluorescence (TADF) based organic light-emitting diodes (OLEDs) have improved the device stability with high quantum efficiency through their advanced material design, they still need further improvement to meet industrial standards. To enhance the stability of the devices, the development of a stable host material is one of the crucial issues. Herein, with a comparison of a conventional p-type host material, 3,3-di(9H-carbazol-9-yl)-1,1'-biphenyl (mCBP), known for its promising stability, three novel host materials incorporating a pyridine unit, mCBP-1N, CzPyPhCz, and CzPyBF, are systematically designed aimed for further stability improvement. The green and blue TADF-OLEDs are fabricated with these three new hosts. The maximum external quantum efficiencies (EQEs) of green OLEDs were 20.3% and 14.0% for CzPyBF and mCBP hosts, respectively. Also, high EQEs of 19.2% and 12.9% were maintained even at 1000 cd m^-2. Most importantly, the CzPyBF host demonstrated a substantially longer device lifetime of 62.7 hours at LT95, which is 2.5 times longer than that of mCBP. Further, lower turn-on voltages were achieved by using CzPyPhCz in both blue and green devices. Our findings indicated that the TADF-OLEDs can simultaneously be improved with lower turn-on voltages, higher EQEs, and longer device lifetimes with the host engineering.