Synthesis, properties, and OLED characteristics of 2,2′-bipyridine-based electron-transport materials: the synergistic effect of molecular shape anisotropy and a weak hydrogen-bonding network on molecular orientation?

Journal of Materials Chemistry C Pub Date: 2015-12-14 DOI: 10.1039/C5TC03737A

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 ETMs. 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%.

Graphical abstract: Synthesis, properties, and OLED characteristics of 2,2′-bipyridine-based electron-transport materials: the synergistic effect of molecular shape anisotropy and a weak hydrogen-bonding network on molecular orientation
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