Effect of Nitrogen Atoms on Structures and Electron Transport of N-heteropentacene Devices.

Pentacene polycyclic aromatic hydrocarbons are the most promising organic semiconductor materials among aromatic compounds due to their potential optoelectronic properties. Introducing nitrogen atoms into the main chain of pentacene is supposed to tune the electronic structure and develop new high-performance organic molecular devices. Herein, we have investigated the electron transport properties of N-heteropentacenes consisting of different numbers, positions, and valence states of N atoms using density functional theory (DFT) and nonequilibrium Green's function (NEGF) method. The results show that the transport properties of N-heteropentacenes are strongly dependent on whether the C-N is a single or double bond. For devices with C-N double bonds, the change of current with voltage is consistent, and its electron transport properties are independent of the number and position of N atoms. In comparison, C-N single-bond devices exhibit an early negative differential resistance (NDR) and significant rectification. Moreover, the threshold voltages exist within certain bias voltages for different numbers of N atoms and might even show a second NDR. These studies would be useful to design performance-enhancing molecular devices by manipulating the molecular structure of N-heteropentacenes.