Pseudoplanar Hole Conductor: HN-D

The direction of carrier transport in an organic electronics device differs with the structure of the device. Although development of high mobility organic semiconductors is promising, control of molecular arrangement in the solid state is also important to increase carrier mobility toward a target direction. A conventional organic electronics material involves crystalline molecules with a rigid and planar structure. For amorphous materials, one has developed organic molecules with a twisted propeller structure.
　

Wakamiya et al. developed pseudoplanar materials (1, 2) in which those structures are intermediate between planar and propeller types.^1,2) They partially introduced an ether-bridged structure into a conventional propeller-type molecule, N,N,N′,N′-tetraphenylbenzidine derivative. The pseudoplanar structure provides one-dimensionally-arranged on-top π-stacking in the crystal. These materials show relatively high mobility along the molecular stacking direction in the crystal, and also demonstrate large anisotropy of carrier mobility in the amorphous film. It was considered that the pseudoplanar materials (1, 2) maintain a molecular stacking along the perpendicular direction with respect to a device substrate in the amorphous film. Accordingly, they are expected to be useful for organic solar cell and organic light-emitting diode devices, because these devices require high carrier mobility in the perpendicular direction toward a device substrate.