A paper written by Yuichiro WATANABE, a 3rd-year iFront Program student (Kido/Sasabe Lab), has been accepted by J. Mater. Chem. C (IF: 4.696) of Royal Society of  Chemistry. This is a joint research with Asso. Prof. Daisuke YOKOYAMA and Asso. Prof. Hiroshi KATAGIRI.

Syntheses, Properties, and OLED Characteristics of 2,2′-Bipyridine-Based Electron-Transport Materials: Synergistic Effect of Molecular Shape Anisotropy and a Weak Hydrogen-Bonding Network on Molecular Orientation
Y. Watanabe, H. Sasabe, D. Yokoyama, T. Beppu, H. Katagiri, J. Kido, J. Mater. Chem. C 2015, accepted.

Abstract: To boost the performances of OLEDs, one of the most promising approaches from a materials chemistry viewpoint is the use of thin solid films with horizontal molecular orientations. In this work, we developed 2,2′-bipyridine-skeleton-based electron-transport materials (ETMs) end-capped with 3,5-dipyridylphenyl groups with the objective of preparing films with horizontal molecular orientations for use in high-performance organic light-emitting devices (OLEDs). These compounds afforded highly oriented films and were used in fac-tris(2-phenylpyridine)iridium(III)-based OLEDs as an ETL. The optimized device exhibited low operating voltages of 2.8 and 3.2 V at luminances of 100 and 1000 cd m−2, respectively. At 1000 cd m−2, this device exhibited a power efficiency of 74 lm W−1 and an external quantum efficiency of 21%.

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