title: Effect of molecular asymmetry on the charge transport physics of high mobility n-type molecular semiconductors investigated by scanning Kelvin probe microscopy.
abstract: We have investigated the influence of the symmetry of the side chain substituents in high-mobility, solution processable n-type molecular semiconductors on the performance of organic field-effect transistors (OFETs). We compare two molecules with the same conjugated core, but either symmetric or asymmetric side chain substituents, and investigate the transport properties and thin film growth mode using scanning Kelvin probe microscopy (SKPM) and atomic force microscopy (AFM). We find that asymmetric side chains can induce a favorable two-dimensional growth mode with a bilayer structure, which enables ultrathin films with a single bilayer to exhibit excellent transport properties, while the symmetric molecules adopt an unfavorable three-dimensional growth mode in which transport in the first monolayer at the interface is severely hindered by high-resistance grain boundaries.
authors.affiliation: Cavendish Laboratory, University of Cambridge , Cambridge CB3 0HE, United Kingdom.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Hu
authors.forename: Nikolai
authors.initials: N
authors.lastname: Berdunov
authors.forename: Chong-an
authors.initials: CA
authors.lastname: Di
authors.forename: Iris
authors.initials: I
authors.lastname: Nandhakumar
authors.forename: Fengjiao
authors.initials: F
authors.lastname: Zhang
authors.forename: Xike
authors.initials: X
authors.lastname: Gao
authors.forename: Daoben
authors.initials: D
authors.lastname: Zhu
authors.forename: Henning
authors.initials: H
authors.lastname: Sirringhaus