Single molecular bilayers of organic semiconductor molecules realized using geometrical frustration

Single molecular bilayers (SMBs) are the fundamental form of molecular nanostructures composed of biological lipids or synthetic amphiphiles. Although the realization of air-stable artificial SMBs is expected to result in versatile applications, those formed via self-assembly of usual amphiphilic molecules have strictly limited their practical use because of the inherent instability and fragility associated with the weak intermolecular interactions. Here we demonstrate the fabrication of unprecedented large-area, uniform, and self-organized SMBs using extended π-conjugated frameworks substituted by alkyl chains of variable length; (πCore)-C_n. These SMBs were produced by simple blade-coating with a solution containing two (πCore)-C_n’s with different alkyl chain lengths. The chain-length disorder did not perturb in-plane molecular order, but acted effectively as a geometrical frustration to inhibit multiple stacking of bilayers. The obtained SMBs exhibited efficient carrier transport as channels of thin-film transistors, reflecting strong intralayer π-π interactions and the concomitant highly layered-crystalline nature. We expect that this finding should open a new route to SMB-based ultrathin super-flexible electronics capable of biomimetic functions.