笹部久宏准教授と卒業生の佐藤瞭君 (Mr. Ryo Sato) の電子輸送材料群の戦略的利用による超高電力効率緑色TADF有機ELに関する「Ultra-High Power Efficiency Thermally Activated Delayed Fluorescent OLEDs by the Strategic Use of Electron Transport Materials」と題する論文が Wiley の Advanced Optical Materials (IF: 7.43) の Best of Advanced Optical Materials 2018 に選出されました。本研究は、京都大学の梶弘典教授（Prof. Hironori Kaji）、鈴木克明助教（Prof. Katsuaki Suzuki）、九州大学の安達千波矢教授（Prof. Chihaya Adachi）との共同研究です。
Ultra-High Power Efficiency Thermally Activated Delayed Fluorescent OLEDs by the Strategic Use of Electron Transport Materials
H. Sasabe*, R. Sato, K. Suzuki, Y. Watanabe, C. Adachi, H. Kaji*, J. Kido*, Adv. Opt. Mater. 2018, 6, 1800376.
Abstract: Thermally activated delayed fluorescent (TADF) emitters are one of the most promising candidates for developing low-cost organic light-emitting devices (OLEDs) that can achieve an internal quantum efficiency of 100%. However, the power efficiency values are still significantly lower than that of their phosphorescent counterparts. To achieve high power efficiency, both a high external quantum efficiency and low drive voltage are required. Here, we successfully developed TADF OLEDs with an ultra-high power efficiency of 133 lm W–1 and an unprecedented low turn-on voltage of 2.22 V via the strategic use of electron-transport materials (ETMs). We used 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]- N,N,N',N'-tetraphenyl-9H-carbazole-3,6-diamine (DACT-II) as a green TADF emitter. A series of green TADF OLEDs were fabricated using two different types of pyrimidine-based ETMs as an exciplex host partner and electron transport layer to minimize the drive voltages. The optimized device showed an external quantum efficiency of 29.2% and maximum power efficiency of 133.2 lm W–1 without any light-outcoupling enhancement. The device also showed 124.0 lm W–1 at 100 cd m–2, and 95.2 lm W–1 at a high brightness of 1000 cd m–2. The drive voltages were 2.48 V at 100 cd m–2 and 2.88 V at 1000 cd m–2. These performances are the best among TADF OLEDs to date, and comparable to state-of-the-art phosphorescent counterparts, even at high brightness of 1000 cd m–2. Our results demonstrate the potential of TADF OLEDs for future low power consumption eco-friendly display and lighting sources.