Theoretical study on charge transport properties of high mobility n-channel organic semiconductor-hexachloro-hexa-azatrinaphthylene

Abstract

The electronic structure and charge transport property of the hexachloro-hexa-azatrinaphthylene (HHAT) compound have been investigated in the framework of density functional theory (DFT). The optimized geometries of the neutral and ionic states of the HHAT are obtained by using the B3LYP hybrid exchange–correlation functional and 6–311++G(d,p) basis set. The HOMO energy, LUMO energy and HOMO-LUMO gap of the compound is found to be −7.15 eV, −3.63 eV and 3.52 eV respectively. The maximum electron distribution of HOMO is delocalized over two branches, whereas, the electron distribution of LUMO is evenly distributed over the central core of the molecule. The lower LUMO energy and higher EA values indicate that the compound possesses substantial air-stability and n-channel characteristics. The computed electronic coupling of LUMO of the compound is found to be comparatively larger in the transverse-channel (86.6 meV) than other channels. The maximum hole mobility and electron mobility are observed to be 0.014 cm2V−1s−1 and 3.543 cm2V−1s−1 at Φ = 0˚ and Φ = 109˚, respectively. This may be accredited to the substitution of the electron-withdrawing group (-Cl) at the end position of the hexa-azatrinaphthylene compound. In HHAT crystal, the conduction band minima (CBM) and valence band maxima (VBM) are found to occur at the X-point, indicating that the material is a direct band gap semiconductor with band gap of 1.9 eV. In addition, the Hirshfeld Surface analysis shows the distribution of surface charge on the fragment of the crystal.