Molecular Stacking Induced by Intermolecular C-H•••N Hydrogen Bonds Leading to High Carrier Mobility in Vacuum-Deposited Organic Films

Simple bottom-up fabrication processes for molecular self-assembly have been developed for the construction of higher-order structures using organic materials, and have contributed to maximization of the potential of organic materials in chemical and bioengineering. However, their application to organic thin-film devices such as organic light-emitting diodes have not been widely considered because simple fabrication of a solid film containing an internal self-assembly structure has been regarded as difficult. Here it is shown that the intermolecular C-H center dot center dot center dot N hydrogen bonds can be simply formed even in vacuum-deposited organic films having flat interfaces. By designing the molecules containing pyridine rings properly for the intermolecular interaction, one can control the molecular stacking induced by the intermolecular hydrogen bonds. It is also demonstrated that the molecular stacking contributes to the high carrier mobility of the film. These findings provide new guidelines to improve the performance of organic optoelectronic devices and open up the possibilities for further development of organic devices with higher-order structures.