Development and function of novel electron-transporters realizinghigher order organic nanostructure for next generation organic LED

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Phosphorescent organic light-emitting device (organic LED) can realize four times higher efficiency than that in fluorescent organic LED. So far, our group has already developed high-efficiency sky-blue, green, and white organic LEDs with external quantum efficiency of 30%. These remarkable advances have been achieved by use of novel phosphorescent materials, especially phenylpyridine-containing electron transport materials (ETMs). However, there is few papers dealing with an effective molecular design for such ETMs. Generally, DFT calculation has been recognized as a powerful tool to design a promising material, however, this calculation can give only limited structural and optical properties in vacuum. While in organic LEDs, amorphous molecular glasses are normally used and solid state properties are critical for realizing high-efficiency devices. From this perspective, we have investigated the relationships among (1) DFT calculation, (2) physical properties and (3) overall device performances of novel ETMs with emphasis on the single crystal XRD analyses. Based on these analyses, we have successfully proposed a promising design for an ETM that can be self-assembled by using CH/N hydrogen bonds between pyridines in the solid state.