Charge transport and electronic properties of N-heteroquinones: quadruple weak hydrogen bonds and strong π-π stacking interactions

The charge transport and photophysical properties of N-heteroquinones, which can function as n-type organic semiconductors in organic field-effect transistors (OFETs) with high electron mobility, were systematically investigated using hopping model, band theory, and time-dependent density functional theory (TDDFT). The calculated absorption spectra and electron mobility are in good agreement with experimental results. To the studied compounds, subtle structural modifications can greatly reduce the reorganization energy. There are two main kinds of intermolecular interaction forces of the studied compounds in the crystal, which result from intermolecular pi-pi and hydrogen bonds interactions, respectively. The results of hopping model show that the electron transport properties are mainly determined by pathways containing intermolecular pi-pi interactions, and hole transport properties are mainly determined by pathways containing intermolecular hydrogen bonds from the standpoint of transfer integral. Moreover, electronic transfer integral value increases with the enhancement of intermolecular overlap corresponding to the overlap extent of pi-pi packing. Hole transfer integral value decreases with decreasing the number of hydrogen bonds. This means that charge transport properties can be efficiently tuned by controlling the relative positions of the molecules and the number of hydrogen bonds. The analysis of band structure also supports the conclusion of hopping model.