News [2019]

Title: Control of Molecular Orientation in Organic Semiconductor Films Using Weak Hydrogen Bonds , Adv. Mater. 2019, accepted.

2019/02/22

Title: Control of Molecular Orientation in Organic Semiconductor Films Using Weak Hydrogen Bonds
By Yuichiro Watanabe, Daisuke Yokoyama,* Tomoyuki Koganezawa, Hiroshi Katagiri, Takashi Ito, Satoru Ohisa, Takayuki Chiba, Hisahiro Sasabe,* and Junji Kido*, Adv. Mater. 2019, accepted.

Abstract: Use of the intrinsic optoelectronic functions of organic semiconductor films has not yet reached its full potential, mainly because of the primitive methodology used to control the molecular aggregation state in the amorphous films during vapor deposition. Here, we present a universal molecular engineering methodology to control molecular orientation; this methodology strategically uses non-covalent, intermolecular weak hydrogen bonds in a series of oligopyridine derivatives. A key was to use two bipyridin-3-ylphenyl moieties, which form self-complementary intermolecular weak hydrogen bonds that does not induce unfavorable crystallization. Another key was to incorporate a planar anisotropic molecular shape by reducing steric hindrance of core structure for inducing pai–pai interactions. These synergetic effects enhance horizontal orientation in amorphous organic semiconductor films and significantly increasing electron mobility. Through this evaluation process, we selected an oligopyridine derivative as an electron-transporter, and successfully developed a highly efficient and stable deep-red organic light-emitting devices as a proof-of-concept.

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