Theoretical studies on the hole transport property of tetrathienoarene derivatives: The influence of the position of sulfur atom, substituent and π-conjugated core

Chemical modifications such as changing the position of heteroatom, introducing different substituents and p-conjugated cores are powerful molecular design tools to modulate their optical and electrochemical performance. In this context, in-depth density functional theory investigations on the geometries, frontier molecular orbitals, reorganization energies, transfer integrals, anisotropic mobilities and band structures of tetrathienoarene derivatives were carried out to provide insights into the effects of these chemical modifications on their hole transport properties. The electrostatic potential, Hirshfeld surface analysis, energy decomposition analysis (EDA) and anisotropic mobility were also employed to shed light on the intricate interplays among molecular packings, intermolecular interactions and transport properties. It is found that compared with 2, 1a with sulfur atom inside has lower frontier orbital energy level, smaller reorganization energy and larger transfer integral and hole mobility. However, more S . . . S interactions in 2 could provide more effective transport channels for charge carrier transport. The introduction of hexylthienyl groups (1c) results in an enhancement of pi-pi interaction and leads to an increase in the highest occupied molecular orbital (HOMO) and transfer integrals. Meanwhile, the strongest intermolecular interaction energy of pathway A in 1c renders its transport behavior with typical one-dimensional (1D) transport. Moreover, anthracene as the pi-conjugated core seemed to possess better transport properties in comparison with dibenzothiophene or chrysene acting as core. In addition, the dispersion energy of all investigated compounds plays a leading role in determining the energetically accessible stacking motifs. We hope that our speculation would facilitate the future design and preparation of high-performance charge-transport materials. (C) 2013 Elsevier B.V. All rights reserved.