Theoretical investigations on the charge transport properties of anthracene derivatives with aryl substituents at the 2,6-position—thermally stable “herringbone” stacking motifs

Abstract

At present, the high-performance organic semiconductor materials based on the small aromatic anthracene-core and its derivatives develop comparatively slow, which largely due to the lack of a profound understanding with the influence of chemical modifications on their charge-transfer properties. In this paper, the electronic properties and the charge transport characteristics of several typical anthracene-based derivatives with aryl group substituted at 2,6-site are systematically investigated by multi-scale simulation methods including Molecular Dynamics (MD) simulation and full quantum nuclear tunneling model with the help of density functional theory (DFT). To elucidate the origin of different charge transport properties of these anthracene-based materials, molecular stacking and the noncovalent intermolecular interaction analysis are carried out caused by different substituents in anthracene-based derivatives. The results indicate that as the size of the aryl substituent increases, the electron and hole injection capabilities, air oxidation stability with the anthracene derivatives are greatly improved. In addition, incorporation of the 2,6-site aryl substituents can inhibit the stretching vibration of the anthracene-core during charge transport, and allow the molecular packing along the long axis (a-axis of DPA and BDBFAnt, c-axis of dNaAnt) almost no slipped; as well as the main transport channels remain unchanged, exhibiting more isotropic 2D transport properties. It should be emphasized that the edge-to-face dimers with the smallest dihedral angles are closest to the thermal stable dimer model, relative larger π-orbital distributions in the transmission channels (dimer1,2) and the largest spatial overlap, resulting in the largest hole transfer integral in DPA (V_h1/h2=57 meV). Although the analysis of thermal disorder effect shows phonon scattering effect, the maximum hole mobility of DPA molecule is still as high as 1.5 cm² V^-1 s^-1.